Method and device for distributing resources in communication system with multiple inputs and outputs
Abstract
FIELD: technology for distributing resources of descending communication line in communication system with multiple inputs and multiple outputs. ^ SUBSTANCE: in accordance to method, for possible data transmission one or more sets of terminals is formed, while each set includes unique combination of one or more terminals and matches hypothesis subject to evaluation. Formed additionally may be one or more sub-hypotheses for each hypothesis, while each sub-hypothesis matches certain assignment of several transmitting antennas to one or more terminals in hypothesis. Then efficiency of each hypothesis is evaluated, one of evaluated sub-hypotheses is selected, based on their efficiency. Then terminal (terminals) in selected sub-hypothesis is planned for data transmission, and after that data are encoded, modulated and transferred to each terminal, planned for transmission, via one or more transmitting antennas, assigned to terminal. ^ EFFECT: increased efficiency. ^ 7 cl, 9 dwg
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Expired 15 May 2022, 4.4 years ago.
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49 claims: 7 independent, 42 dependent
- 1Способ планирования передачи данных множеству терминалов по прямой линии связи в беспроводной коммуникационной системе, содержащий этапы:формируют один или более наборов терминалов для возможной передачи данных, причем каждый набор включает в себя комбинацию из одного или более терминалов и соответствует гипотезе, предназначенной для оценки;назначают множество передающих антенн одному или более терминалам в каждом наборе;оценивают эффективность каждой гипотезы, частично основываясь на назначении антенн для данной гипотезы;выбирают одну из одной или более оцененных гипотез, основываясь на эффективности;планируют передачу данных одному или более терминалам в выбранной гипотезе.
- 2Способ по п.1, дополнительно содержащий этапы:формируют множество подгипотез для каждой гипотезы, причем каждая подгипотеза соответствует конкретному назначению передающих антенн одному или более терминалам в гипотезе, при этом оценивают эффективность каждой подгипотезы и одну из оцененных подгипотез выбирают, основываясь на эффективности.
- 3Способ по п.1, в котором назначение включает в себя этапы:идентифицируют пару передающая антенна и терминал с наилучшей эффективностью среди всех неназначенных передающих антенн;назначают передающую антенну из пары терминалу из этой пары;удаляют назначенные передающую антенну и терминал из рассмотрения.
- 4Способ по п.1, в котором каждая гипотеза оценивается, в частности основываясь на информации о состоянии канала (ИСК) для каждого терминала в гипотезе, причем ИСК отражает характеристики канала между передающими антеннами и терминалом.
- 5Способ по п.4, в котором ИСК для каждого терминала содержит оценку отношения сигнал/шум-плюс-помеха (SNR), определенную в терминале, основываясь на сигналах, переданных через передающие антенны.
- 6Способ по п.5, в котором каждый набор из одного или более терминалов, предназначенных для оценки, ассоциируется с соответствующей матрицей SNR, полученных в одном или более терминалах набора.
- 7Способ по п.4, дополнительно содержащий этап:определяют схему кодирования и модуляции для каждой передающей антенны, основываясь на ИСК, ассоциированной с передающей антенной.
- 8Способ по п.1, в котором один или более терминалов в каждом наборе выбираются из совокупности терминалов.
- 9Способ по п.8, в котором совокупность терминалов включает в себя один или более терминалов SIMO, причем каждый выполнен с возможностью приема одного потока данных.
- 10Способ по п.9, в котором выбранная гипотеза включает в себя множество терминалов SIMO.
- 11Способ по п.8, в котором совокупность терминалов включает в себя один или более терминалов MIMO, причем каждый выполнен с возможностью приема множества потоков данных от множества передающих антенн.
- 12Способ по п.11, в котором выбранная гипотеза включает в себя один терминал MIMO.
- 13Способ по п.11, в котором каждый запланированный для передачи терминал MIMO выполняет обработку при приеме с последующим подавлением для восстановления данных, переданных на терминал MIMO.
- 14Способ по п.5, в котором один или более наборов лучей антенн оценивается каждым терминалом, предназначенным для планирования, для получения одного или более векторов SNR, по одному вектору для каждого набора лучей антенн.
- 15Способ по п.1, в котором каждый набор включает в себя терминалы, имеющие аналогичный энергетический запас линии связи.
- 16Способ по п.1, в котором этап оценки включает в себя вычисление метрики эффективности для каждой гипотезы.
- 17Способ по п.16, в котором метрика эффективности представляет собой функцию пропускной способности, достижимой каждым терминалом в гипотезе.
- 18Способ по п.16, в котором для планирования выбирается гипотеза, имеющая наилучшую метрику эффективности.
- 19Способ по п.1, дополнительно содержащий присвоение приоритетов терминалам, подлежащим рассмотрению для планирования.
- 20Способ по п.19, в котором в каждом наборе множество передающих антенн назначается одному или более терминалам, исходя из приоритетов терминалов в наборе.
- 21Способ по п.20, в котором терминалу в наборе с наивысшим приоритетом назначается передающая антенна, ассоциированная с наибольшей пропускной способностью, а терминалу с самым низким приоритетом в наборе назначается передающая антенна, ассоциированная с самой низкой пропускной способностью.
- 22Способ по п.19, дополнительно содержащий ограничение количества терминалов, подлежащих рассмотрению для планирования, до группы из N терминалов с наивысшим приоритетом, где N равно или больше единицы.
- 23Способ по п.19, дополнительно содержащий поддержание одной или более метрик для каждого терминала, подлежащего рассмотрению для планирования, при этом приоритет каждого терминала определяется, в частности, основываясь на одной или более метриках, поддерживаемых для терминала.
- 24Способ по п.23, в котором одна метрика, поддерживаемая для каждого терминала, относится к уровню средней пропускной способности, достигнутой терминалом.
- 25Способ по п.19, в котором приоритет для каждого терминала дополнительно определяется, основываясь на одном или более факторах, поддерживаемых для терминала и ассоциированных с качеством услуги (QoS).
- 26Способ по п.1, в котором один или более терминалов в выбранной гипотезе планируются для передачи данных по каналу, который включает в себя множество пространственных подканалов.
- 27Способ по п.1, в котором один или более терминалов в выбранной гипотезе планируется для передачи данных по каналу, который включает в себя множество частотных подканалов.
- 28Способ планирования передачи данных множеству терминалов в беспроводной коммуникационной системе, содержащий этапы:формируют один или более наборов терминалов для возможной передачи данных, причем каждый набор включает в себя уникальную комбинацию из одного или более терминалов и соответствует гипотезе, подлежащей оценке;формируют одну или более подгипотез для каждой гипотезы, причем каждая подгипотеза соответствует конкретному назначению множества передающих антенн одному или более терминалам в гипотезе;оценивают эффективность каждой подгипотезы;выбирают одну из множества оцененных подгипотез, основываясь на их эффективности, планируют передачу данных одному или более терминалам в выбранной подгипотезе и передают данные каждому запланированному для передачи терминалу в выбранной подгипотезе через одну или более передающих антенн, назначенных терминалу.
- 29Способ по п.28, в котором этап оценки включает в себя этап:определяют пропускную способность для одного или более терминалов в подгипотезе, исходя из конкретных назначений антенн, при этом выбирают подгипотезу с наивысшей пропускной способностью.
- 30Способ по п.28, в котором формируют один набор терминалов и в котором терминалы в наборе выбирают, исходя из приоритетов терминалов, требующих передачи данных.
- 31Коммуникационная система с множественными входами и множественными выходами (MIMO), содержащая базовую станцию, содержащую множество передающих антенн, планировщик, выполненный с возможностью приема информации о состоянии канала (ИСК), отражающей оценки каналов для множества терминалов в коммуникационной системе, выбора набора из одного или более терминалов для передачи данных по прямой линии связи и назначения множества передающих антенн одному или более выбранным терминалам, процессор передаваемых данных, выполненный с возможностью приема и обработки данных для одного или более выбранных терминалов, основываясь на ИСК для получения множества потоков данных, и множество модуляторов, выполненных с возможностью обработки этого множества потоков данных для получения модулированных сигналов, подходящих для передачи через множество передающих антенн;один или более терминалов, причем каждый терминал содержит множество приемных антенн, причем каждая приемная антенна выполнена с возможностью приема множества модулированных сигналов, передаваемых базовой станцией, множество входных устройств, причем каждое входное устройство выполнено с возможностью обработки сигнала от ассоциированной приемной антенны для получения соответствующего принятого сигнала, процессор приема, выполненный с возможностью обработки множества принятых сигналов от множества входных устройств для получения одного или более потоков декодированных данных и для последующего получения ИСК для множества модулированных сигналов, и процессор передаваемых данных, выполненный с возможностью обработки ИСК для передачи обратно к базовой станции.
- 32Базовая станция в коммуникационной системе с множественными входами и множественными выходами (MIMO), содержащая процессор передаваемых данных, выполненный с возможностью приема и обработки данных для получения множества потоков данных для передачи одному или более терминалам, запланированным для передачи данных, причем данные обрабатываются, основываясь на информации о состоянии канала (ИСК), указывающей оценки канала для одного или более запланированных терминалов;множество модуляторов, выполненных с возможностью обработки множества потоков данных для получения множества модулированных сигналов;множество передающих антенн, выполненных с возможностью приема и передачи множества модулированных сигналов одному или более терминалам, запланированным для передачи;планировщик, выполненный с возможностью приема ИСК для множества терминалов в коммуникационной системе, выбора набора из одного или более терминалов для передачи данных, и назначения множества передающих антенн одному или более выбранных терминалов.
- 33Базовая станция по п.32, в которой поток данных для каждой передающей антенны обрабатывается, основываясь на схеме кодирования и модуляции, выбранной для передающей антенны, исходя из ИСК, ассоциированной с данной передающей антенной.
- 34Базовая станция по п.32, дополнительно содержащая множество демодуляторов, выполненных с возможностью обработки множества сигналов, принимаемых через множество передающих антенн для получения множества принятых сигналов, и процессор принятых данных, выполненный с возможностью дополнительной обработки множества принятых сигналов для получения ИСК для множества терминалов в коммуникационной системе.
- 35Терминал в коммуникационной системе с множественными входами и множественными выходами (MIMO), содержащий множество приемных антенн, причем каждая приемная антенна выполнена с возможностью приема множества модулированных сигналов, передаваемых базовой станцией;множество входных устройств, причем каждое входное устройство выполнено с возможностью обработки сигнала от ассоциированной приемной антенны для получения соответствующего принятого сигнала;процессор приема, выполненный с возможностью обработки множества принятых сигналов от множества входных устройств для получения одного или более потоков декодированных данных и для дальнейшего получения информации о состоянии канала (ИСК) для каждого потока декодированных данных;процессор передаваемых данных, выполненный с возможностью обработки ИСК для передачи обратно к базовой станции, в котором терминал является одним из одного или более терминалов, содержащихся в наборе, запланированных для приема данных, передаваемых от базовой станции в конкретном временном интервале, и в котором набор из одного или более терминалов, запланированных для приема передаваемых данных, выбирается из одного или более наборов терминалов, основываясь на эффективности, оцененной для каждого набора.
- 36Терминал по п.35, в котором терминал запланирован для приема данных передачи от одной или более передающих антенн базовой станции, назначенной терминалу.
- 37Устройство планирования передачи данных множеству терминалов в беспроводной коммуникационной системе, содержащее средство для формирования одного или более наборов терминалов для возможной передачи данных, причем каждый набор включает в себя комбинацию из одного или более терминалов и соответствует гипотезе, предназначенной для оценки;средство для назначения множества передающих антенн одному или более терминалам в каждом наборе;средство для оценки эффективности каждой гипотезы, частично основываясь на назначении антенн для данной гипотезы;средство для выбора одной из одной или более оцененных гипотез, основываясь на эффективности;средство для планирования передачи данных одному или более терминалам в выбранной гипотезе.
- 38Устройство по п.37, дополнительно содержащее средство для формирования множества подгипотез для каждой гипотезы, причем каждая подгипотеза соответствует конкретному назначению передающих антенн одному или более терминалам в гипотезе, при этом выполняется оценка эффективности каждой подгипотезы и выбор одной из оцененных подгипотез, основываясь на эффективности.
- 39Устройство по п.37, в котором средство для назначения включает в себя средство для идентификации пары передающая антенна и терминал с наилучшей эффективностью среди всех неназначенных передающих антенн;средство для назначения передающей антенны из этой пары терминалу из этой пары;средство для удаления назначенной передающей антенны и терминала из рассмотрения.
- 40Устройство по п.37, в котором каждая гипотеза оценивается, в частности, основываясь на информации о состоянии канала (ИСК) для каждого терминала в гипотезе, причем ИСК отражает характеристики канала между передающими антеннами и терминалом.
- 41Устройство по п.40, в котором ИСК для каждого терминала содержит оценки отношения сигнал/шум-плюс-помеха (SNR), основываясь на сигналах, переданных через передающие антенны.
- 42Устройство по п.40, дополнительно содержащее средство для определения схемы кодирования и модуляции для каждой передающей антенны, основываясь на ИСК, ассоциированной с передающей антенной.
- 43Устройство по п.42, в котором средство оценки включает в себя средство для вычисления метрики эффективности для каждой гипотезы.
- 44Устройство по п.43, в котором метрика эффективности представляет собой функцию пропускной способности, достижимой каждым терминалом в гипотезе.
- 45Устройство по п.37, дополнительно содержащее средство для присвоения приоритетов терминалам, подлежащим рассмотрению для планирования.
- 46Устройство по п.45, в котором в каждом наборе множество передающих антенн назначается одному или более терминалам, исходя из приоритетов терминалов в наборе.
- 47Устройство по п.45, дополнительно содержащее средство для поддержания одной или более метрик для каждого терминала, подлежащего рассмотрению для планирования, при этом приоритет каждого терминала определяется, в частности, основываясь на одной или более метриках, поддерживаемых для терминала.
- 48Устройство планирования передачи данных множеству терминалов в беспроводной коммуникационной системе, содержащее средство для формирования одного или более наборов терминалов для возможной передачи данных, причем каждый набор включает в себя уникальную комбинацию из одного или более терминалов и соответствует гипотезе, подлежащей оценке;средство для формирования одной или более подгипотез для каждой гипотезы, причем каждая подгипотеза соответствует конкретным назначениям множества передающих антенн одному или более терминалам в гипотезе;средство для оценки эффективности каждой подгипотезы;средство для выборки одной из множества оцененных подгипотез, основываясь на их эффективности, средство для планирования передачи данных одному или более терминалам в выбранной подгипотезе, средство для передачи данных каждому запланированному для передачи терминалу в выбранной подгипотезе через одну или более передающих антенн, назначенных терминалу.
- 49Устройство по п.48, в котором средство для оценки включает в себя средство для определения пропускной способности для одного или более терминалов в подгипотезе, исходя из конкретных назначений антенн, при этом выбирается подгипотеза с наивысшей пропускной способностью.
Independent claims49
198 paragraphs in 5 sections, as filed
TECHNICAL FIELD
The present invention relates generally to data communication, and more particularly to methods for allocation of downlink resources in a communication system with multiple-input multiple-output (MIMO).
BACKGROUND
Wireless communication systems are widely deployed to provide various types of communication such as voice, data, and so on, for a number of users. Such systems may be based on code division multiple access (CDMA), multiple access with time division (TDMA), multiple access, frequency division (FDMA), or some other multiple access techniques.
A communication system with multiple-input multiple-output (MIMO) used for the transmission of multiple independent data streams plurality (NT) transmit antennas and multiple (NR) receive antennas. In one embodiment of the conventional MIMO system data streams at a given time is transmitted I to one terminal. However, communication systems with multiple access with a base station with multiple antennas may also concurrently communicate with a number of terminals. In this case, the base station uses several antennas, and each terminal employs NR antennas to receive one or more of the plurality of data streams.
The connection between a multi-antenna base station and one multi-antenna terminal is called a MIMO channel. MIMO channel, formed by these NT transmit and NR receive antennas may be decomposed into NC independent channels, with NC≤min {NT, NR}. Each of the NC independent channels is also referred to as a spatial subchannel of the MIMO channel and corresponds to a dimension. The MIMO system can provide improved performance (e.g., increased transmission capacity) if the additional dimensionalities these subchannels created by the multiple transmit and receive antennas.
Each MIMO channel between a base station and a terminal typically has a different link characteristics and is associated with different transmission capacity as the spatial subchannels available to each terminal have different effective capacitance. Efficient use of the available resources of the downlink (forward) link (and higher throughput) may be achieved if the available spatial subchannels NC allocated efficiently, so that data is transmitted on these subchannels to the "appropriate" set of terminals in the MIMO system.
Thus, a need exists for resource allocation method of a downlink MIMO system to improve system efficiency.
SUMMARY OF THE INVENTION
Aspects of the present invention provide methods for increasing the efficiency of the downlink wireless communications system. In one aspect, data may be transmitted from the base station to one or more terminals using one of a number of different modes. In the MIMO mode, all available downlink data streams over the communication line allocated to a terminal using multiple antennas (i.e. MIMO terminal). In the N-SIMO mode, a single data stream is allocated to each of a number of different terminals, each terminal uses multiple antennas (i.e., SIMO terminals). In mixed mode, the downlink resources may be allocated to a combination of SIMO and MIMO terminals, with both types of terminals supported simultaneously. When data is transmitted simultaneously at multiple SIMO terminals, one or more MIMO terminals, or a combination thereof, increases the transmission capacity of the system.
In another aspect, scheduling schemes are provided to schedule data transmission for the active terminals. The scheduler selects the best mode of operation, based on various factors, such as the service requested by the terminal. Additionally, the scheduler may implement an additional level of optimization by selecting a particular set of terminals for simultaneous data transmission and the allocation of the available transmit antennas to the selected terminals such that high system efficiency is achieved, and other requirements. Below is shown and described several scheduling schemes and antenna allocation schemes.
A particular embodiment of the invention provides a method for scheduling data transmission on the downlink series of terminals in a wireless communication system. In accordance with this method, for possible data transmission are formed one or more sets of terminals, each set of terminals includes a unique combination of one or more terminals corresponding to a hypothesis to be evaluated. For each hypothesis may be generated by one or more sub-hypotheses, each sub-hypothesis corresponds to a particular purpose of a number of transmit antennas to the one or more terminals in the hypothesis. Then the estimated performance of each sub-hypothesis and selects one of the evaluated sub-hypotheses based on their effectiveness. Then the terminal (s) in the selected sub-hypothesis are scheduled for data transmission, and then transmitted to the data scheduled for transmission terminal through one or more transmit antennas assigned to the terminal.
Each antenna may be used to transmit an independent data stream. To achieve high performance, each data stream may be coded and modulated based on a scheme selected, for example, based on an evaluation of the signal / noise-plus-interference (SNR) for the antenna used to transmit the data stream.
Terminals needing data transfer (i.e., active terminals) may be prioritized based on various metrics and factors. The priority of the active terminals may then be used to determine which terminal (s) should be considered for scheduling and / or destination of available antennas to the selected terminals. The present invention provides methods, systems, and apparatus that implement various aspects, embodiments, and features of the present invention, as described in more detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
The features, nature, and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the drawings in which like reference numbers refer to like elements throughout.
1 is a block diagram of a communication system with multiple-input multiple-output (MIMO), which can be designed and operated to implement various aspects and embodiments of the present invention.
2 is a flowchart of scheduling of terminals for data transmission according to an embodiment of the present invention.
3 is a flowchart of the destination of transmission antennas using the criterion "max-max", according to an embodiment of the present invention.
4 is a block diagram of a scheduling scheme, based on the priority, which is considered for scheduling a set of one or more highest priority terminals, according to an embodiment of the present invention.
5 is a block diagram of a base station and a number of terminals in the MIMO communication system.
6 is a block diagram of an embodiment of the transmitter portion of base station capable of processing data for transmission to terminals based on the available CSI.
7 is a block diagram of an embodiment of the receiving part of the terminal.
8A and 8B are block diagrams of embodiments of a channel MIMO processor / data device suppressor respectively reception (RX) MIMO processor / data terminal; and
Figure 9 shows the average throughput for the MIMO communication system with four transmit antennas (i.e., NT = 4) and four receive antennas at each terminal (i.e., NR = 4) of two different modes.
DETAILED DESCRIPTION OF THE INVENTION
1 is a block diagram of a communication system 100 with multiple-input multiple-output (MIMO), which can be designed and operated to implement various aspects and embodiments of the present invention. MIMO system 100 utilizes a data set (NT) transmit antennas and multiple (NR) receive antennas. MIMO system 100 is effectively formed for a communication system with multiple access, having a base station (BS) 104 that can concurrently communicate with a number of terminals (T) 106. In this case, the base station 104 employs multiple antennas and represents the multiple-input (MI) for transmission on the downlink from the base station to the terminals. A set of one or more "connected" terminals 106 collectively represent the multiple outputs (MO) for transmissions on the downlink. As used herein, the term "swapping terminal" is a terminal, receiving data specific to the user from the base station, and an "active" terminal is a terminal requiring data transmission in an upcoming or a subsequent transmission interval. Active terminals may include terminals that are currently connected.
MIMO system 100 may be designed to implement any number of standards and is designed for CDMA, TDMA, FDMA, and other multiple access techniques. CDMA standards include IS-95, cdma2000, and W-CDMA, and the TDMA standards include the Global System for Mobile Communications (GSM). These standards are known in the art and are incorporated herein in their entirety by reference.
MIMO system 100 may operate to transmit data via a number of transmission channels. Each terminal 106 communicates with base station 104 via the MIMO channel. A MIMO channel may be decomposed into NC independent channels, with NC≤min {NT, NR}. Each of the NC independent channels is also referred to as a spatial subchannel MIMO channel. For a MIMO system, not using modulation with orthogonal frequency division (OFDM), there is usually one frequency subchannel and each spatial subchannel may be referred to as "transmission channel". For both MIMO systems, utilizing OFDM, each spatial subchannel of each frequency subchannel may be referred to a transmission channel.
For the example shown in Figure 1, base station 104 concurrently communicates with terminals 106a to 106d on (as shown by the solid lines) via multiple antennas available at the base station and multiple antennas available at each terminal. Terminals 106a at 106d may receive pilot signals and other signaling information from the base station (as shown by dashed lines), but not from the base station receive information specific to the user.
Each terminal 106 in MIMO system 100 employs NR antennas to receive one or more data streams. In general, the number of antennas at each terminal is equal to or greater than the number of data streams transmitted by the base station. It is not necessary that all terminals in the system, have been equipped with the same number of receive antennas.
For MIMO system 100, the number of antennas at each terminal (NR) is typically greater than or equal to the number of antennas at the base station (NT). In this case, for the downlink, the number of spatial subchannels is limited by the number of transmit antennas at the base station. Each transmit antenna may be used to send an independent data stream that may be coded and modulated based on a scheme supported by the spatial subchannel associated with the MIMO channel between the base station and the selected terminal.
Aspects of the present invention provide ways to improve wireless communication system. These techniques may be advantageously used to improve the downlink of a cellular system with multiple access. These methods can also be used in combination with other multiple access methods.
In one aspect, data may be transmitted from the base station to one or more terminals using a number of different modes. In the MIMO mode, the available downlink resources are allocated to one terminal (i.e., MIMO terminal). In the N-SIMO mode, the available downlink resources are allocated to several terminals, with each terminal demodulating a single data stream (i.e., SIMO terminals). In mixed mode, the downlink resources may be allocated combination SIMO and MIMO terminals, with both types of terminals supported simultaneously in the same channel, which may be a slot (interval) time code channel, a frequency subchannel, etc. When data is transmitted simultaneously at multiple SIMO terminals, one or more MIMO terminals, or a combination thereof, increases the transmission capacity of the system.
In another aspect, scheduling schemes are provided to schedule data transmission for the active terminals. The scheduler chooses to use the best mode of operation, based on various factors, such as the service requested by the terminal. Additionally, the scheduler may implement an additional level of optimization by selecting a particular set of terminals for simultaneous data transmission and the allocation of the available transmit antennas to the selected terminals, so that a high system efficiency and other requirements. Below are described in more detail several scheduling schemes and antenna allocation schemes.
The MIMO base station can transmit multiple independent data streams through a plurality of transmit antennas to one or more terminals scheduled for transmission. If the propagation environment has significant scattering in the terminals can be used MIMO receiver processing techniques for effective use of the spatial dimension of a MIMO channel to increase transmission capacity. Methods for MIMO receiver processing may be used if the base station communicates with multiple terminals simultaneously. From the viewpoint of the terminal can be used the same methods receiver processing to process NT different signals intended for that terminal (i.e., a MIMO terminal) or just one of the NT signals (i.e., SIMO terminals).
As shown in Figure 1, the terminals may be randomly distributed over the area of the base station (or "cell") or may be co-located. For wireless communication systems generally characteristics connections change over time due to a number of factors such as fading and multipath. At a particular time channel response between the NT transmit array base station antennas and NR receive antennas for a single terminal may be characterized by a matrix H whose elements are independent random variables with Gaussian distribution:
<img he="29" wi="128" file="00000002.tif" img-content="undefined" img-format="tif" />
where H is the channel response matrix for the terminal, and hij represent the connection between the i-th transmitting antenna of the base station and the j-th reception antenna of the terminal.
As shown in equation (1), the channel estimates for each terminal may be represented by a matrix having NTxNR elements corresponding to the number of transmit antennas of the base station and the number of receive antennas of the terminal. Each element of the matrix H describes the response for a respective pair of transceivers antenna between the base station and one terminal. For simplicity, equation (1) describes a channel characterization based on a model amplitude fading channel (i.e., one complex value for the entire system bandwidth). The actual operating environment, the channel may be frequency selective (i.e., the channel response varies across the system bandwidth), and may be used more detailed characteristics of the system (e.g., each element of the matrix H may include a set of values for different frequency subchannels or time delays).
Active terminals in the MIMO system periodically estimate the channel response for each pair of transceivers antenna. The channel estimates may be facilitated in various ways, e.g., such as methods based on the use of pilot and / or data to make solutions known in the art. Channel estimates may comprise the complex-value channel response for each pair of transmitting-receiving antenna, as shown above in equation (1). The channel estimates give information on the characteristics of the transmission in each of the spatial subchannels, i.e. what data rate can be supported in each subchannel with a given set of transmission parameters. The information given by the channel estimates may be processed into the product after the processing assessment of signal / noise-plus-interference (SNR) for each spatial subchannel (described below) or some other statistic that allows the transmitter to select the appropriate transmission parameters for the spatial subchannel. Typically, this process of obtaining the necessary statistics reduces the amount of data required to characterize a channel. In any case, this information represents one form of channel state information (CSI, CSI), which may be transmitted to the base station. Also, other shapes can be transmitted CSI as described below.
The aggregate CSI received from the set of terminals can be used to (1) select the "best" set of one or more terminals for data transmission, (2) assign the available transmit antennas to the selected terminals in the set, and (3) selecting a suitable coding scheme, and modulation for each transmit antenna. With the available CSI may be various scheduling schemes are designed to maximize the efficiency of the downlink by evaluating the particular combination of terminal and assignment of antennas providing the best system performance (e.g., the highest throughput) subject to the limitations and requirements of the system. Using the spatial (and possibly frequency) "signatures" of hotel active terminals (such as their channel estimates), may be increased average throughput downlink.
The terminals may be scheduled for data transmission based on various factors. One set of factors may relate to system constraints and requirements such as the desired quality of service (QoS), maximum latency, average data rate, etc. It is possible that in a communication system with multiple access require satisfaction of some or all of these factors in terminal (i.e., for each terminal). Another set of factors may relate to system performance, which may be quantified by the average system throughput rate or some other indicator system efficiency. These various factors are described in more detail below.
The scheduling schemes can be designed to select the best set of terminals for simultaneous data transmission on the available transmission channels, so that the efficiency of the system becomes the maximum while satisfying the system constraints and requirements. For simplicity, various aspects of the invention are described below for a MIMO system without OFDM, in which the base station through each transmit antenna may transmit one independent data stream. In this case the base station via the NT transmit antennas may be transmitted simultaneously (up to) NT independent data streams directed to one or more terminals, each equipped with NR receive antennas (ie NTxNR MIMO), where NR≥NT.
For simplicity, it is assumed that the number of receive antennas equals the number of transmit antennas (ie, NR = NT) for much of the description below. It is not necessary, since all of the analysis applies to the case where NR≥NT.
Scheduling of data transmission on the downlink comprises two parts: (1) selecting one or more sets of terminals for evaluation, and (2) assign the available transmit antennas to terminals in each set. Can be considered for scheduling all or only a subset of the active terminals and these terminals may be combined to form one or more sets (i.e., hypotheses) to be evaluated. For each hypothesis, the available transmit antennas can be assigned to the terminals in the hypothesis based on any scheme destination antennas. The terminals in the best hypothesis may then be scheduled for data transmission in an upcoming interval. The flexibility in both selecting the best set of terminals for data transmission and to assign the transmit antennas to the selected terminals allows the scheduler to optimize the efficiency of using a medium with a multi-user diversity.
In order to determine the "optimum" transmission to a set of terminals, each terminal and each spatial subchannel is provided SNR, or any other sufficient statistics. If statistics are SNR, then for each set of terminals to be evaluated for data transmission in the upcoming transmission interval, a hypothesis matrix r SNR "after treatment" (defined below) for this terminal set may be expressed as:
<img he="28" wi="128" file="00000003.tif" img-content="undefined" img-format="tif" />
where γi, j is the post processing SNR for the data stream (hypothetically) transmitted from the i-th transmit antenna to the j-th terminal.
In the N-SIMO NT rows in the hypothesis matrix r correspond to NT vectors SNR for NT different terminals. In this mode, each row in the hypothesis matrix G gives the SNR of each transmit data stream for one terminal. In mixed mode, for a particular MIMO terminal, for receiving two or more data streams, that terminal SNR vector can be replicated such that the vector appears in as many rows as to be transmitted to the terminal data streams (i.e., one row in the data stream). Alternatively, one row in the hypothesis matrix F can be used for each SIMO or MIMO terminal, and the scheduler can be designed to correspondingly mark and evaluate these different types of terminals.
Each terminal set used for evaluation (hypothetically) NT transmitted data streams are received via NR receive antennas and a terminal NR received signals can be processed using spatial or space-time compensation for separating NT transmitted data streams, as described below. It can be estimated SNR data stream after processing (i.e., after compensation), and a post processing SNR for the data stream. Each terminal may be provided with a set of NT post processing SNR for NT data streams that may be received by the terminal.
If the terminal for processing the received signals using a method for processing when taken with subsequent equalization and interference cancellation (or "successive cancellation"), the SNR after treatment attainable in the terminal for each transmitted data stream depends on the order in which the transmitted data streams are detected (i.e., demodulated and decoded) to recover the transmitted data, as described below. In this case, each terminal may be provided with several sets of SNR for several possible detection orders. It can then be formed and evaluated hypotheses plurality of matrices to determine which specific combination of terminals and detection order provides the best system performance.
In any case, each hypothesis matrix r includes the post processing SNR for a particular set of terminals (i.e., hypothesis) intended for evaluation. Such SNR after treatment are SNR, achievable in the terminals and are used to evaluate the hypotheses.
2 is a block diagram of a process 200 for scheduling terminals for data transmission in accordance with an embodiment of the present invention. For clarity, the first gives a general description of the process, and then describe in detail some of the steps of the process.
Initially in step 212 is initialized metrics that should be used to select the best set of terminals for data transmission. To evaluate sets of terminals may be employed various performance metrics, and some of them are described in more detail below. For example, it may be used performance metric that maximizes system throughput.
Then, in step 214 from all active terminals considered for scheduling, chosen (new) set of one or more active terminals. This set of terminals forms a hypothesis designed to assess. To limit the number of active terminals considered for scheduling, may be used various methods, which then reduces the number of hypotheses intended for evaluation, as described below. For each terminal in the hypothesis in step 216 is restored SNR vector (e.g.,). SNR vectors for all terminals in the hypothesis form the hypothesis matrix F given in Equation (2).
<IMG>
For each hypothesis matrix r of NT transmit antennas and NT terminals, there NT factorial possible combinations of destination terminals transmit antennas (i.e., NT! Sub-hypotheses). Thus, to assess the specific forms (new) combination of antenna assignments / terminal. This particular combination of assignments antenna / terminal forms a sub-hypotheses to be evaluated.
Next, in step 220, the sub-hypothesis is evaluated and determined metric (e.g., the system throughput) corresponding to this sub-hypothesis (e.g., based on SNR for the sub-hypothesis). Then, in step 222, said performance metric is used to update the performance metric corresponding to the current best sub-hypothesis. More specifically, if the performance metric for the sub-hypothesis is better than a metric for the best sub-hypothesis, then this sub-hypothesis becomes the new best sub-hypothesis, and the performance metric and other terminal metrics corresponding to this sub-hypothesis are saved. Performance metrics and terminal metrics are described below.
Then in step 224 it is determined whether all the current sub-hypothesis of the hypothesis have been evaluated. If all sub-hypotheses have been evaluated, the process returns to step 218 to evaluate and select another, not yet evaluated combination use antenna / terminal. Steps 218 224 are repeated for each sub-hypothesis is intended for evaluation.
If at step 224 it is determined that all sub-hypotheses for this hypothesis have been evaluated, then at step 226 a determination is made whether all hypotheses have been considered. If not all hypotheses have been considered, then the process returns to step 214 to evaluate and select another, not yet considered set of terminals. Steps 214 through 226 are repeated for each hypothesis to be considered.
If at step 226 all hypotheses have been considered, then when a specific set of terminals scheduled for data transmission in the upcoming transmission interval and their assigned antennas are known. SNR after processing corresponding set of destination terminals and antennas may be used to select appropriate coding and modulation schemes for the data streams to be transmitted to the terminals. In step 228 the scheduled terminals may be notified (e.g., via a control channel) scheduled transmission slot assignment antennas coding and modulation scheme. Alternatively, the terminals may perform "blind" detection and attempt to detect all transmitted data streams to determine which of the data streams, if any, is intended for them.
If the scheduling scheme requires other metrics supported by the system and the terminal (for example, the average data rate over the past K transmission intervals, latency for data transmission, etc.), then these metrics are updated at step 230. The terminal metrics may be used to assess effectiveness of the individual terminals, and are described below. Scheduling is typically performed for each transmission interval.
For a given matrix T hypotheses planner evaluates various combinations of pairs of transmitting antennas and terminals (ie, sub-hypothesis) to determine the best destinations for hypotheses. There may be used various assignment scheme to assign transmit antennas to terminals to achieve various system goals such as fairness, maximum efficiency, etc.
<img he="9" wi="54" file="00000005.tif" img-content="undefined" img-format="tif" />
<IMG>
wherein it represents SNR after processing the i-th transmit antenna to the j-th terminal, and the subscripts {a, b, ... and r} identify the specific terminals in pairs of antenna / terminal for the sub-hypothesis.
<img he="11" wi="46" file="00000007.tif" img-content="undefined" img-format="tif" />
Each sub-hypothesis is further associated with a performance metric, Rsub-hub, which may be a function of various factors. For example, a performance metric based on the SNR after processing may be expressed as
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<img he="14" wi="128" file="00000008.tif" img-content="undefined" img-format="tif" />
To determine the performance metric can be used various functions. In one embodiment, the function can be used achievable throughput for all NT transmit antennas for this sub-hypothesis, which may be expressed as:
<img he="9" wi="128" file="00000009.tif" img-content="undefined" img-format="tif" />
where ri is the throughput associated with the i-th transmit antenna in the sub-hypothesis, and may be expressed as:
<IMG>
where ci is a positive constant that reflects the fraction of the theoretical capacity achieved by the coding and modulation schemes selected for the data stream transmitted through the i-th transmit antenna, and γi is the SNR after the processing for the i-th data stream.
The first antenna assignment scheme shown in Figure 2 and described above represents a specific scheme that evaluates all possible combinations of assignments of transmit antennas to terminals. The total number of potential sub-hypotheses for assessing the scheduler for each hypothesis is NT !, which still may be a large value on the assumption that the rating may require a large number of hypotheses. The first scheduling scheme performs an exhaustive search to determine the sub-hypothesis, which provides "optimum" efficiency of the system, which is expressed numerically performance metric used to select the best sub-hypothesis.
To reduce the complexity of processing when assigning transmit antennas can be used a number of ways. One of these methods is described below and can also be implemented in other ways without departing from the scope of the invention. These techniques may also provide high system performance while reducing the amount of processing required to assign the antenna terminals.
In the second scheme, the destination antenna terminals in the hypothesis evaluated using the criterion of maximum-maximum ("max-max"). Using this criterion "max-max", each transmit antenna is assigned to a specific terminal, which gives the best SNR for a given transmit antenna. Purpose of the antenna is performed for one transmit antenna at a time.
3 is a block diagram of a process 300 the destination transmit antennas to terminals using the criterion "max-max" in accordance with an embodiment of the present invention. The processing shown in Figure 3 is performed for a particular hypothesis, which corresponds to a particular set of one or more terminals. First, in step 312 the maximum SNR is determined after the processing in the matrix T hypotheses. Said maximum SNR corresponds to a particular pair of transmit antenna / terminal, and the transmitting antenna assigned to the terminal in step 314. This transmit antenna and terminal then, in step 316 are removed from the matrix F and the matrix is reduced to dimension (NT-1) x (NT 1) by removing the columns corresponding to the transmitting antenna and the row corresponding to the terminal, the purpose of which was made.
In step 318 it is determined whether all the transmit antennas have been assigned hypothesis. If all antennas have been assigned, then in step 320 the antennas provided purpose and the process ends. Otherwise, the process returns to step 312 and similarly produced assignment another transmit antenna.
After completion of the assignment of antennas for a given matrix T hypothesis may be determined (e.g., based on SNR, the corresponding destination antennas) performance metric (e.g., system capacity corresponding to this hypothesis as shown in equations (3 and 4). This performance metric is updated for each hypothesis. After evaluating all hypotheses best set of terminals and antenna assignments selected for data transmission in the subsequent transmission interval.
Table 1 shows an example matrix r of post processing SNR obtained terminals in a 4x4 MIMO system, wherein the base station includes four transmit antennas and each terminal includes four receive antennas. For antenna assignment scheme based on the max-max criterion, the best SNR (16 dB) in the original matrix is achieved by transmit antenna 3 and is assigned to the terminal 1, as shown by shading the cell of the fourth row in the third column. Then the antenna 3 and terminal 1 are removed from the matrix. The best SNR (14 dB) in the reduced 3x3 matrix is achieved by antennas 1 and 4, which are respectively assigned to terminals 3 and 2. Then the remaining transmit antenna 2 is assigned to the terminal 4.
Table 1SNR (dB) is transmitted antennaTerminal1234179165281012143147694121075
Table 2 shows the assignment of antennas using the max-max criterion for the example matrix r shown in Table 1. For terminal 1, the best SNR (16 dB) is achieved when processing the signal transmitted from transmit antenna 3. The best transmit antennas for other terminals are also shown in Table 2. The scheduler can use this information to select appropriate coding and modulation scheme to use for data transmission.
<img he="15" wi="129" file="00000010.tif" img-content="undefined" img-format="tif" />
Scheduling scheme shown in Figures 2 and 3 represents a specific scheme, evaluate different hypotheses corresponding to various possible sets of active terminals, require data transmission in the upcoming transmission interval. The total number of hypotheses for assessing the scheduler can be quite large even for a small number of active terminals. In fact, the total number of hypotheses, Nhyp, can be expressed as:
<IMG>
where NU is the number of active terminals to be considered for planning. For example, if NU = 8 and NT = 4, then Nhyp = 70. It can be used for the determination of an exhaustive search for a particular hypothesis (and specific assignments antennas) to ensure optimum system performance, Quantitative performance metric used to select the best hypothesis and destination antennas.
It may also be implemented other scheduling schemes, reducing the complexity and are within the scope of the present invention. These schemes may also provide high system performance while reducing the amount of processing required to schedule terminals for data transmission.
In another scheduling scheme, active terminals are scheduled for data transmission based on their priority. The priority of each terminal may be derived based on one or more metrics (e.g., average throughput), system constraints and requirements (e.g., maximum latency), other factors, or combinations thereof, as described below. It can maintain a list of all active terminals that require data in the upcoming transmission interval (also called "frame"). If the terminal requests transfer of the data, it is added to the list and its metrics are initialized (e.g., reset). The metrics of each terminal in the list thereafter updated on each frame. If the terminal no longer requires the data, it is removed from the list.
For each frame, all or a subset of the terminals in the list may be considered for scheduling. The specific number of terminals may be considered based on many factors. In one embodiment, only the NT highest priority terminals are selected for data transmission. In another embodiment, the invention is considered for scheduling NX highest priority terminals, where NX> NT.
4 is a flow diagram for the circuit 400 scheduling based on the priority, and according to an embodiment of the invention, are considered for scheduling NT highest priority terminals. In each frame interval, in step 412, the scheduler checks the priority of the active terminals in the list and selects the set of NT highest priority terminals. The remaining terminals in the list are not considered for planning. Then, in step 414, remove the ratings for each selected terminal. For example, the selected terminal may be received SNR and after processing used to form the hypothesis matrix r.
Then, in step 416, the selected terminals administered NT transmit antennas based on the channel estimates and using one of a number of antenna assignment schemes. For example, the assignment of antennas may be based on an exhaustive search or max-max criterion, described above. In another antenna assignment scheme, the transmit antennas assigned to the terminal so that the terminals after their metrics update priorities are normalized as close as possible.
<img he="15" wi="128" file="00000012.tif" img-content="undefined" img-format="tif" />
To determine the priority of the active terminals may be used various metrics and factors. In one embodiment, for each terminal in the list and for each metric used to plan, supported "quantitative index." In one embodiment, for each active terminal supported quantitative indicator of the average throughput for a particular averaging time interval. In one embodiment, the quantitative index for terminal n in frame k is computed as a linear average throughput received in a certain time interval, and can be expressed as:
<img he="9" wi="131" file="00000015.tif" img-content="undefined" img-format="tif" />
<IMG>
wherein a realized data rate (in units of bits / frame) for terminal n at frame i and may be computed as shown in equation (4). Generally, limited to a specific maximum achievable data rate, and a particular minimum data rate (e.g., zero). In another embodiment, a quantitative indicator for terminal n in frame k is an exponential average throughput, resulting in a certain time interval, and can be expressed as:
<IMG>
<IMG>
<IMG>
<IMG>
<IMG>
where α is a constant exponential averaging, the larger value α corresponds to a greater time interval averaging.
If the terminal requires the transmission of data, it is added to the list and its quantitative indicator is initialized by zero. Quantitative value for each terminal in the list sequentially updated in each frame. Whenever a terminal is not scheduled for transmission in a frame, its data rate for a given interval is set to zero (i.e.,) is updated accordingly its quantitative proportion. If a frame is received with errors by the terminal, the effective data rate of the terminal for that frame may be set to 0. On the frame error may not be known immediately (e.g., due to the delay in signal propagation in both ends of the circuit confirmation / refuting (Ack / Nak) used for data transmission), but quantitative measure may be adjusted accordingly, as soon as the information becomes available.
<IMG>
The priority of the active terminals may be defined, in particular based on system constraints and requirements. For example, if the maximum latency for a particular terminal exceeds a threshold value, then this UE may be assigned a higher priority.
In order to determine the priority of the active terminals may also be considered other factors. One such factor may relate to the type of data to be transmitted to the terminals. These are sensitive to delay may be associated with a high priority, and data that are not sensitive to delay may be associated with a lower priority. The data retransmitted due to decoding error in the previous transmission may also be associated with a high priority because the retransmitted data can expect other processes. Another factor may relate to the type of data services provided by these terminals. Also, for the priority may consider other factors without departing from the scope of the present invention.
Thus, the priority of the terminal can be a function of any combination of (1) a quantitative indicator for the terminal is maintained for each of the metric and (2) other parameter values maintained for system constraints and requirements, and (3) other factors. In one embodiment, the system constraints and requirements represent "hard" values (e.g., high or low priority, depending on whether or not violated constraints and requirements) and quantitative indicators represents the "flexible" value. For this embodiment, the terminals for which the system constraints and requirements are not met, are considered immediately, together with other terminals based on their quantitative indicators.
Maybe planning a scheme based on the priorities for achieving equal bandwidth (ie, the same QoS (Quality of Service)) for all terminals in the list. In this case, active terminals is assigned a priority based on their achieved average throughput, which may be determined as shown in equation (6) or (7). In planning such a scheme, based on the priorities, the scheduler uses quantitative indicators to determine the priority of the terminals available for the purpose of transmitting antennas. Quantitative parameters terminals are updated based on the fact whether or not they have the purpose of transmitting antennas. Priority terminals in the list may be assigned such that the terminal with the lowest quantitative indicator is assigned the highest priority, and on the contrary, the terminal with the highest quantitative indicator will be assigned the lowest priority. Also, there may be other methods for ranking terminals. Assigning priorities may also assign unequal weights quantitative indicators terminalov.Dlya planning scheme, in which terminals are selected and scheduled for transmission of data based on their priorities, may from time to time will be weak grouping of terminals. A set of "weak" is a set of terminals, which gives similar channel response matrices Hk which give the same and low SNR for all terminals on all transmit data streams as given in the hypothesis matrix r. Subsequently, this leads to lower overall throughput for each terminal in the set. If this happens, the priorities terminals can basically do not change for a few frames. In this case, the scheduler can be bound to a given set of terminals as long as the priorities are not changed significantly in order to cause a change in the group.
In order to avoid the above-described effect of "clustering", the scheduler can be designed to recognize the situation before said destination terminals available transmit antennas and / or detect the situation immediately after it occurs. To determine the degree of linear dependence of the matrix Hk channel response can be used a number of ways. A simple way is to use to determine the matrix T a certain threshold. If all are below a given SNR threshold, then the clustering condition exists. This condition determining clustering scheduler can reorder the terminals (e.g. random), an attempt to reduce the linear dependence in the hypothesis matrix. It can also be designed mixing scheme in order to force the scheduler to select a set of terminals, which gives a "good" hypothesis matrix (i.e., a matrix having a minimum level of linear dependence).
Some scheduling schemes described above employ methods of reducing the amount of processing required to select terminals and assign the selected terminals transmit antennas. These and other methods can also be combined to derive other scheduling schemes, without departing from the scope of the present invention. For example, may be considered for scheduling NX highest priority terminals, using any of the schemes described above.
It can also be developed more complex scheduling schemes that enable achieving capacity close to the optimum. These schemes may be required to evaluate a large number of hypotheses and antenna assignments to determine the best set of terminals and the best assignment of antennas. There may also be other scheduling schemes are designed to take advantage of the statistical distribution of the data rates achievable by each terminal. This information may be useful for reducing the number of hypotheses to be evaluated. Additionally, for some applications it may be possible to identify which terminal groupings (i.e., hypotheses) work well by analyzing efficiency for some time. This information can then be stored, updated and used in subsequent intervals scheduler planirovaniya.Sposoby described above may be applied to the scheduled terminals for data transmission using the MIMO mode, N-SIMO mode, and mixed mode. For each of these modes may be other types of analysis, as described below.
MIMO Mode
In the MIMO mode, (up to) NT independent data streams may be simultaneously transmitted to the base station via the NT transmit antennas dedicated to one terminal of MIMO NR receive antennas (i.e., NTxNR MIMO), wherein NR≥NT. The terminal may use spatial compensation (for nondispersive MIMO channel with a flat frequency response) or space-time compensation (for a dispersive MIMO channel with a frequency response of the channel, frequency-dependent) for processing and separation of NT transmitted data streams. SNR of each data stream after processing (i.e., after compensation) can be evaluated and reported to the base station as CSI (channel state information, CSI), which then uses this information to select appropriate coding and modulation scheme to use for each transmission antenna so that the predetermined terminal was able to detect each transmitted data stream at the desired level of performance.
If all data streams are transmitted to one terminal, in the case of MIMO mode, then the terminal to process NR received signals to recover NT transmitted data streams may be used in a method of processing successive cancellation receiver. This method sequentially processes the NR received signals several times (or iterations) to recover the signals transmitted from the terminals, and for each iteration one signal is restored. For each iteration, the method performs a linear or non-linear processing (ie, spatial or spatio-temporal compensation) for the NR received signals to restore one of the received signals and suppresses noise associated with the restored channel of the received signals to produce a "modified" signals remote component interference.
Then, at the next iteration, the modified signals are processed to recover the other received signal. Using interference cancellation associated with the recovered signal from the received signal, SNR improves for the transmitted signals included in the modified signals but not yet recovered. The improved SNR results in improved efficiency of the terminal as well as system. In fact, under certain operating conditions, the efficiency achievable in processing using successive cancellation receiver in conjunction with spatial compensation on a minimum mean square error (MMSE), is comparable with the efficiency of the processing with full CSI. A method of processing at successive cancellation receiver described in more detail in US patent application number [Attorney Docket No. PD010210], entitled "METHOD AND APPARATUS FOR PROCESSING DATA IN A MULTIPLE-INPUT MULTIPLE-OUTPUT (MIMO) COMMUNICATION SYSTEM UTILIZING CHANNEL STATE INFORMATION", filed on 11 May, 2001, and assigned to the assignee hereof and which is incorporated herein in their entirety by reference.
In one embodiment, each MIMO terminal in the system estimates and sends back NT post processing SNR values for the NT transmit antennas. SNR from the active terminals may be evaluated by the scheduler to determine which terminal to perform transmission and when and to determine the appropriate coding and modulation scheme to use based on the distribution of each transmit antenna for each selected terminal.
MIMO terminals for data transmission may be selected based on a particular performance metric formed to achieve the desired system goals. Performance metric may be based on one or more functions and any number of parameters. To form the performance metrics could be various functions such as a function of the achievable throughput for the MIMO terminals, which is given by equations (3 and 4) given above.
N-SIMO Mode
In the N-SIMO (up to) NT independent data streams may be simultaneously transmitted to the base station via the NT transmit antennas for the (up to) NT different SIMO terminals. To maximize efficiency, the scheduler may consider a data set of a large number of possible terminals. The scheduler determines the best set of NT terminals to transmit simultaneously on a given channel (i.e., time slot, code channel, frequency sub-channel, etc.). In the communication system with multiple access, in general, there are limits to meet some of the requirements for each terminal, such as maximum latency or average data rate. In this case, the scheduler can be designed so that it selects the best set of terminals which satisfy these constraints.
In one embodiment, for N-SIMO mode terminals are used for processing the received signals compensated linear spatial and SNR after processing corresponding to each transmission antenna of the base station is provided. The scheduler uses this information to select terminals for data transmission and the assignment of transmit antennas to the selected terminals.
In another embodiment, for the N-SIMO mode terminals are used for processing the received signal processing with successive cancellation receiver to achieve the highest SNR after processing. In the case of treatment at successive cancellation receiver SNR after processing for the transmitted data streams depend on the order in which the detected (i.e., demodulated and decoded) data stream. In some cases, a particular SIMO terminal may not be able to cancel the interference from a given transmitted data stream intended for another terminal, since the coding and modulation scheme used for this data stream was selected based on SNR after treatment of another terminal. For example, the transmitted data streams may be intended for terminal ux and coded and modulated for proper detection at a (e.g., 10 dB) SNR after treatment achievable at the target terminal ux, but another terminal uy may receive the same transmitted data stream at a worse SNR after processing and thus is suitably not able to detect the data stream. If the data stream intended for another terminal can not be detected error free, then interference suppression is associated with this data stream is not possible. Processing at successive cancellation receiver viable if SNR after processing corresponding to the transmitted data stream, permits reliable detection.
In order for the scheduler to take advantage of improving the SNR after treatment, provided SIMI terminals, using the processing when successive cancellation receiver, each such terminal can determine SNR after processing, corresponding to different possible orderings of detection for the transmitted data streams. NT transmitted data streams can be detected on the basis of NT factorial (t.e.NT!) Possible orderings terminals SIMO, and each order is associated to NT SNR values after treatment. Thus, each active terminal may inform the base station · NT NT! values SNR (for example, if NT = 4, then each terminal can communicate SIMO 96 values SNR). The scheduler can use this information to select terminals for data transmission and for the further purpose of transmitting antennas to the selected terminals.
If the terminals use successive cancellation process, the scheduler can also consider the terminal for each possible detection orders. However, a large number of these n oryadkov are usually wrong, because a particular terminal may not be able to correctly detect the data streams transmitted to another terminal due to low SNR after processing received at this terminal to undetectable data stream.
As indicated above, the transmit antennas may be assigned to the selected terminals based on various schemes. In one antenna assignment schemes transmit antennas are assigned so as to achieve high system performance and based on the priorities of the terminals.
Table 3 shows an example of SNR after treatment determined by each terminal in the hypothesis under consideration. For terminal 1, the best SNR is achieved when detecting the data stream transmitted through a transmit antenna 3, as indicated by the shaded cell in row 3, column 4 of the table. The best transmit antennas for other terminals in the hypothesis are also indicated by means of shaded cells.
Table 3SNR (dB) Antenna peredachiTerminal1234179165281012143147694121075
If each terminal identifies a different transmit antenna from which the best SNR is detected after treatment, then the transmit antennas may be assigned to terminals based on the their best SNR after processing. For the example given in Table 3, terminal 1 may be assigned to transmit antenna 3, and terminal 2 may be assigned to transmit antenna 2.
If more than one terminal prefers the same transmit antenna, then the scheduler can determine the antenna assignment based on various criteria (e.g., fairness, performance metric, and others.). For example, Table 3 indicates that the best SNR after treatment for terminals 3 and 4 are obtained for a data stream transmitted via the same transmit antenna 1. Assuming a maximum bandwidth, then the scheduler may assign transmit antenna 1 to the terminal 3 and transmit antenna 2 terminal 4. However, if antennas are assigned based on requirements of fairness, then transmit antenna 1 may be assigned to terminal 4 if terminal 4 has higher priority than terminal 3.
Mixed mode
The methods described above can be generalized to the case of mixed SIMO and MIMO terminals. For example, if the base stations are four transmitting antennas, then four independent data streams may be transmitted on one 4x4 terminal MIMO, two 2x4 terminal MIMO, four 1x4 terminal SIMO, one 2x4 terminal MIMO plus two 1x4 terminal SIMO or any other combination of terminals, for receiving generally four data streams. The scheduler can be designed to select the best combination of terminals based on the SNR after treatment for any hypothetical set of terminals, wherein each hypothesized set may include a combination of both MIMO terminals, and SIMO terminals.
Even if a mixed-mode traffic is supported, the use of treatment at successive cancellation receiver terminals (e.g., MIMO) imposes an additional restriction on the scheduler due to these relationships. These constraints may result in more hypothesized sets being evaluated, since in addition to considering different sets of terminals the scheduler must also consider demodulation of the various orders by each terminal data streams. Purpose of transmit antennas and the choice of coding and modulation schemes may take into account these dependencies for efficiency.
Transmitting antenna
The set of transmit antennas at the base station may physically represent a certain set of "apertures", each of which may be used for direct transfer of the corresponding data stream. Each aperture may be formed by a set of one or more antenna elements distributed in space (e.g., physically localized to one place or distributed over multiple sites). Alternatively, the antenna apertures may have one or more (fixed) matrix arranged in front and forming a beam, wherein each matrix is used for the synthesis of a separate set of antenna beams from the set of apertures. In this case, the above description of transmitting antennas similarly applicable to the transformed antenna beams.
It can be determined in advance for a number of beams forming the matrix and the terminals may evaluate the post processing SNR for each of the possible matrices (or sets of antenna beams) and send SNR vectors back to the base station. Usually different sets of antenna beams converted achieve different efficiency (ie SNR after processing), and this is reflected in the reported vectors SNR. Then, the base station may perform scheduling and antenna assignment for each of the possible beam-forming matrices (using the reported SNR vectors), and select a particular beamforming matrix as well as a set of terminals and their use antenna that provides the best use of available resources.
Application of beam-forming matrix provides additional flexibility in scheduling terminals and may further provide increase efficiency. As an example, the following situations may be well suited for beam-forming transformations:
- High correlation in MIMO channel, so that the best efficiency can be achieved with a small number of data streams. However, transmission of only a subset of the available transmit antennas (and using only their associated transmit amplifiers) results in a smaller total transmit power. It may be selected for transformation of most or all of the transmit antennas (and their amplifiers) for the data streams sent. In this case, the transmitted data stream is achieved by high power transmission;
- Physically disconnected terminals can be somehow insulated in their location. In this case, the terminals may be served by a standard fast Fourier transform for apertures with a horizontal spacing in the set of beams directed in different azimuths.
Performance
The methods described herein may be viewed as a particular form of multiple access spatial diversity (SDMA), where each transmitting antenna in an antenna array of the base station is used to transmit a single data stream using channel state information (e.g., SNR or any other significant parameters that determine the supported data rate) obtained terminals in the service area. High performance is achieved on the basis of the channel state information CSI, which is used for scheduling terminals and processing data.
The methods described herein can provide improved performance (e.g., higher throughput). It was produced for the quantitative description of the modeling system capacity possible for some of these methods. In the simulation, it was assumed that the channel response matrix Hk associated with the array of transmit antennas and receive antennas of k-th terminal is composed of a complex Gaussian random variables with the same variance and zero mean. Simulations were performed for MIMO modes and SIMO.
In the MIMO mode for each realization (i.e., each transmission interval) describes four MIMO terminals (each with four receive antennas) and the best terminal is selected and planned for data transmission. Scheduled for transmission terminal transmitted four independent data streams and processing terminal used when receiving successive cancellation (MMSE-compensated c) for processing the received signals and recover the transmitted data streams. Recorded average throughput for the planned terminal for transmitting MIMO.
In the N-SIMO mode for implementation considered every four SIMO terminals, each with four receive antennas. SNR after treatment for each SIMO terminal are determined using MMSE linear spatial compensation (without treatment with successive cancellation receiver). Transmitting antennae were appointed selected terminals, based on the criteria for max-max. Four terminals scheduled for transmission transmitted four independent data streams and each terminal used for payment MMSE processing of the received signals and recover the data stream. The capacity for each planned to transfer terminal SIMO recorded separately, and also recorded the average throughput for all scheduled for transmission terminals.
Figure 9 shows the average throughput for the MIMO communication system with four transmit antennas (i.e., NT = 4) and four receive antennas at each terminal (i.e., NR = 4) for the MIMO mode and the N-SIMO. Simulated throughput associated with each operating mode, represented as a function of the average SNR after processing. The average throughput for the MIMO mode is shown in graph 910, the average throughput for the N-SIMO mode is shown in graph 912.
As shown in Figure 9, the simulated throughput associated with the N-SIMO mode using the max-max criterion antenna assignment shows better performance than that achieved in the MIMO mode. In the MIMO terminals benefit obtained from the processing of a successive cancellation to achieve higher SNR after processing. In the SIMO mode, the ability to use a scheduling scheme multiuser diversity goal to achieve higher efficiency (i.e., higher throughput) even though each terminal uses linear spatial compensation. In fact, the multi-user diversity provided in the N-SIMO mode, results in an average bandwidth of downlink, which exceed the capacity achievable by dividing a transmission interval into four equal duration sub-interval and assigning each MIMO terminal to a corresponding sub-interval.
The scheduling schemes used in modeling the two operating modes were not designed to provide proportionate fairness and some terminals will show a higher average throughput than others. If we take the criterion of equal service, differences in capacity between the two modes can be reduced. Nevertheless, the ability to use both coherent MIMO terminals, and N-SIMO terminals provides added flexibility in the provision of wireless data services.
For simplicity, various aspects and embodiments of the invention have been described for a communication system in which (1) the number of receive antennas equals the number of transmit antennas (i.e., NR = NT), and (2) through each antenna of the base station sends one stream data. In this case, the number of transmission channels equal to the number of available spatial subchannels MIMO channel. For a MIMO system, utilizing OFDM, each spatial subchannel may be associated a plurality of frequency subchannels, and these frequency subchannels may be assigned to terminals based on the above-described methods. For a dispersive channel matrix H would represent a three-dimensional cube of channel response estimates for each terminal.
Each scheduled terminal for transmission may also be provided with the number of receive antennas greater than the total number of data streams. Moreover, multiple terminals may share a given transmit antenna, and the sharing may be achieved by multiplexing (multiplexing) with time division multiplexing (e.g., assigning different fractions transmission interval to different terminals), sealed on code division multiplexing (e.g., assigning different orthogonal codes to different terminals ), other circuitry, or any combination seal of said circuits.
The scheduling schemes set forth herein select terminals and assign antennas for data transmission based on channel state information (e.g., SNR after treatment). SNR for the data processing after the terminals depends on the particular transmit power level used for the data streams transmitted by the base station. For simplicity, it is assumed that all data streams transmission power level is the same (i.e., no transmission power control). However, by controlling the transmission power for each antenna may be changed achievable SNR. For example, reducing the transmit power for a particular transmit antenna using the power control is reduced SNR, associated with the data stream transmitted via this antenna, the interference caused by this data stream, in other data streams will also decrease, and other data streams may be achieved best SNR. Thus, power control may also be used in conjunction with the scheduling schemes set forth herein without departing from the scope of the present invention.
Planning terminals for the transmission based on the priority, as described in US patent application number 09 / 675.706, entitled "METHOD AND APPARATUS FOR DETERMINIMG AVAILABLE TRANSMIT POWER IN A WIRELESS COMMUNICATION SYSTEM" filed on September 29, 2000 Planning data for the downlink as described in US patent application number 08 / 798.951, entitled "METHOD AND APPARATUS FOR FORWARD LINK RATE SHEDULING", filed September 17, 1999 The rights to said patent application assignee of the present application and are incorporated herein in whole their entirety by reference.
The scheduling schemes set forth herein, include a number of features and provide numerous advantages. Some of these features and advantages are described below.
First, the scheduling schemes support various operating modes, including a mixed mode, wherein data transmission on the downlink different combinations may be scheduled SIMO and MIMO terminals. Each SIMO or MIMO terminal is associated with an SNR vector (i.e. one row in equation (2)). The scheduling schemes can evaluate data for any number of possible combinations of terminals.
Second, the scheduling schemes provide a plan for each transmission interval that includes a set of (optimal or near optimal) "mutually compatible" terminals based on their spatial signatures. Mutual compatibility may be interpreted as the coexistence of the transmission in the same channel at the same time for given specific limitations relating to the requirements for the transmission rate of data terminals, transmit power, link margin, a terminal SIMO and MIMO, and optionally, other factors.
Third, the scheduling schemes support various data rates based on the SNR after treatment achievable terminals. Each scheduled for transmission terminal may be informed when to expect data transmission on the assigned antenna (s) and velocity (speed) of data (for example, for each transmit antenna).
Fourth, the scheduling schemes can be designed to consider sets having the same link margin. Terminals may be grouped according to their performance link margin. Then, the scheduler may consider combinations of terminals in one group "link margin" when searching for mutually compatible spatial signatures. This grouping according to link margin may improve the overall spectral efficiency of scheduling schemes compared to achievable by ignoring the link margins. Moreover, for scheduling terminals with the same transmission link margin can be more easily produced power control of downlink (e.g., on the entire set of terminals) to improve overall spectral reuse. To this can be viewed as a combination of the adaptive reuse scheduling downlink in combination with SDMA for SIMO / MIMO. Scheduling based on link margin, described in more detail in US patent application number 09 / 539.157, entitled "METHOD AND APPARATUS FOR CONTROLLING TRANSMISSIONS OF A COMMUNICATIONS SYSTEM", filed March 30, 2000 and US patent application number [ Attorney Docket No. PA010071], entitled "METHOD AND APPARATUS FOR CONTROLLING UPLINK TRANSMISIONS OF A WIRELESS COMMUNICATION SYSTEM", filed May 3,, 2001, the rights to which assignee of the present application and which are incorporated herein in their entirety by reference.
Communication MIMO system
Figure 5 is a block diagram of a base station 104 and communication terminal 106 in MIMO system 100. At base station 104, data source 512 provides data (i.e., information bits), processor 514 transmit (TX) data. For each transmit antenna TX data processor 514 (1) encodes the data in accordance with a particular coding scheme, (2) interleaves (i.e., reorders) the encoded data in accordance with a particular interleaving scheme, and (3) transforms bits , the interleaved modulation symbols for one or more transmission channels selected for data transmission. The encoding increases the reliability of data transmission. The interleaving provides time diversity for the coded bits, allowing the transfer of data, based on an average SNR for the transmit antenna combat fading, and further eliminate the correlation between coded bits used to form each modulation symbol. The interleaving may further provide frequency diversity if the coded bits are transmitted over multiple frequency subchannels. In one aspect, the coding and symbol mapping may be performed based on control signals provided by a scheduler 534.
Coding, interleaving, and signal conversion can be performed based on various schemes. Some such schemes are described in the aforementioned US patent application number [Attorney Docket No. PA010210]; US patent application number 09 / 826.481, entitled "METHOD AND APPARATUS FOR UTILIZING CHANNEL STATE INFORMATION IN A WIRELESS COMMUNICATION SYSTEM", filed March 23, 2001 .; and US patent application number 09 / 776.075, entitled "CODING SCHEME FOR A WIRELESS COMMUNICATION", filed on February 1, 2001, assigned to the assignee hereof and which is incorporated herein in its entirety by reference.
TX MIMO processor 520 receives and demultiplexes the modulation symbols from TX data processor 514 and provides a stream of modulation symbols for each transmission channel (e.g., each transmit antenna), one modulation symbol per time slot (slot). TX MIMO processor 520 may further perform the preconditioned modulation symbols for each selected transmission channel if full CSI is available (e.g., the channel response matrix H). MIMO processing and CSI processing is more fully described in detail in US patent application number 09 / 532.492, entitled "HIGH EFFICIENCY, HIGH PERFORMANCE COMMUNICATION SYSTEM EMPLOYING MULTI-CARRIER MODULATION", filed on 22 March 2000, assigned to the assignee hereof and which is incorporated herein in its entirety by reference. If OFDM is not applicable, the TX MIMO processor 520 provides a stream of modulation symbols for each antenna used for data transmission. And if OFDM is used, the TX MIMO processor 520 provides each antenna used for data transmission, the modulation symbol vector stream. If processing is executed with the full-CSI, TX MIMO processor 520 provides for each antenna used for data stream modulation symbols pretreated or pretreated modulation symbol vectors. Then, each stream is received and modulated by a respective modulator (MOD) 522 and transmitted via an associated antenna 524.
Each scheduled terminal 106 for transmitting a certain number of receive antennas 552 receives the transmitted signals, and each receive antenna provides a received signal to a respective demodulator (DEMOD) 554. Each demodulator (or input device) 554 performs processing complementary to that performed at modulator 552. The modulation symbols from all demodulators 554 are issued by the receiver (RX) MIMO processor 556 / data and processed to recover one or more data streams transmitted for the terminal. RX MIMO processor 556 / data performs processing complementary to that performed by TX data processor 514 and TX MIMO processor 520 and provides decoded data to a data receiver 560. Processing in the terminal 106 is described in more detail in the aforementioned US patent application number [Attorney Docket No. PA010210] and 09 / 776.075.
At each active terminal 106, RX MIMO processor 556 / data further evaluates the communication status and provides CSI (e.g., SNR estimates after processing or measurement channel gain). Then a TX data processor 562 receives and processes the CSI and provides processed data indicative of the CSI to one or more modulators 554. Modulator (modulators) 554 performs additional processing of the processed data and transmit the CSI back to base station 104 over the reverse channel. CSI may be reported by the terminal using various signaling techniques (e.g., fully differential representation or a combination thereof), as described in the aforementioned US patent application number 09 / 826.481.
At base station 104, the transmitted feedback signal is received by antennas 524, demodulated by demodulators 522, and provided to RX MIMO processor 532 / data. RX processor 532 MIMO / data performs processing complementary executed TX processor 562 and recovers data communicated ISK, which is then transmitted to the scheduler 534.
Scheduler 534 uses the messages CSI to perform a number of functions such as (1) selecting a set of best terminals for data transmission, (2) assign the available antennas to the selected terminals, and (3) determining the coding and modulation schemes to be used for each assigned transmit antenna. Scheduler 534 may schedule terminals to achieve high throughput or based on other criteria or performance metrics, as described above. Figure 5 shows a scheduler 534 included in the base station 104. In another embodiment, the scheduler 534 may be implemented as part of some other element of communication system 100 (e.g., a base station controller, which is connected and communicates with multiple base stations ).
6 is a block diagram of an embodiment of a base station 104h capable of processing data for transmission to the terminals based on CSI available to the base station (e.g., communicated by the terminals). The base station 104h is one embodiment of the transmitter portion of base station 104 in Figure 5. The base station 104h includes (1) a TX data processor 514h that receives and processes information bits to provide modulation symbols and (2) TX MIMO processor 520x that demultiplexes the modulation symbols for the NT transmit antennas.
In the particular embodiment illustrated in Figure 6, TX data processor 514h includes a demultiplexer 608 associated with a number of channel data processors 610, one processor for each of the NC transmission channels. Demultiplexer 608 receives and demultiplexes the combined information bits into several (up to NC) data streams, one data channel to each of the transmission channels used for data transmission. Each data stream issued by the respective channel data processor 610.
In the embodiment illustrated in Figure 6, each channel data processor 610 includes encoder 612, channel interleaver unit 614, and symbol mapping element 616. Encoder 612 receives and encodes the information bits of the received data stream in accordance with a particular coding scheme to provide coded bits. Channel interleaving unit 614 subjects the interleaved coded bits based on a particular interleaving scheme to provide time diversity. And symbol mapping element 616 converts the bits interleaved modulation symbols for the transmission channel used to transmit the data stream.
Also, along with the processed information bits are encoded and multiplexed pilot data (e.g., data of known structure (pattern)). The processed pilot data may be transmitted (e.g., using a seal time division (TDM)) in all channels, or a subset thereof, are used to transmit the information bits. The pilot data can be used at the terminals to perform channel estimation.
As shown in Figure 6, coding, interleaving, and modulation data (or combination thereof) can be made based on the available CSI (e.g., communicated to the terminal). In one coding and modulation scheme, adaptive encoding is performed by using a fixed base code (e.g., a turbo code with a coding rate 1/3), and adjusting puncturing (periodic puncturing) to achieve the required data rate supported by a given transmission channel SUIT used for data transmission. For this scheme, puncturing may be performed after the channel interleaving. In other coding and modulation scheme may use different encoding schemes, based on the reported claim. For example, each of the data streams may be coded by an independent source. With this scheme, the terminals may be used in the processing circuit at successive cancellation receiver for detecting and decoding the data streams as described in more detail below.
Symbol mapping element 616 can be designed to group sets of bits to generate interleaved not binary symbols and mapping each non-binary symbol into a point in a signal constellation corresponding to a particular modulation scheme (e.g., QPSK, M-PSK, QAM, or kakoy- or other scheme) selected for that transmission channel. Each point of the converted signals corresponds to a modulation symbol. The number of information bits that may be transmitted by each modulation symbol at a certain level of efficiency (e.g., one percent packet error rate) is dependent on the SNR of the communication channel.
The modulation symbols from TX data processor 514h are sent to a TX MIMO processor 520x, which is one embodiment of TX MIMO processor 520 in Figure 5. Within TX MIMO processor 520x demultiplexer 622 receives (up to) NC modulation symbol streams from NC channel data processors 610 and demultiplexes the received modulation symbols into a number of (NT) modulation symbol streams, one stream for each antenna used for transmission of modulation symbols. Each modulation symbol stream is provided to a respective modulator 522. Each modulator 522 converts the modulation symbols into an analog signal, and further amplifies, filters, performs quadrature modulation, and frequency upconverts the signal to obtain a modulated signal suitable for transmission over a wireless link.
Structure transmitter implementing OFDM, is described in the aforementioned US patent application number [Attorney Docket No. PA010210], 09 / 826.481, 09/09 and 776.075 / 532.492.
7 is a block diagram of an embodiment of a terminal 106x capable of implementing various aspects and embodiments of the present invention. Terminal 106x is one embodiment of the receiver portion of terminal 106a-106n of Figure 5 and implements processing method when successive cancellation receiver to receive and recover the transmitted signals. The transmitted signals from (up to) NT transmit antennas are received by each of NR antennas 552a of 552r and routed to a respective demodulator (DEMOD) 554 (which is also called the input processor). Each demodulator 554 performs the reduction to the desired form (e.g., filters and amplifies) a respective received signal, downconverts reduced to the required form of the signal to an intermediate frequency or band, and digitizes the signal from the low frequency to obtain samples. Each demodulator 554 may further demodulate the samples with a received pilot signal to obtain a stream of received modulation symbols, which is supplied to the CPU 556h RX MIMO / data.
In the embodiment illustrated in Figure 7, RX MIMO processor 556h / data (which is one embodiment of RX MIMO processor 556 / data 5) includes a certain number of successive (i.e., cascaded) stages 710 receiver processing, one stage for each transmitted data stream intended for the recovery in the terminal 106x. In one of the processing circuits in the transmission, one data stream is transmitted through each transmission channel assigned to terminal 106x, and each data stream is independently processed (e.g., on its own coding and modulation scheme) and transmitted over a respective transmit antenna. Said processing circuit for the transmission data streams is equal to the number of assigned transmission channels, which is also equal to the number of transmit antennas assigned to terminal 106x to transmit data (which may be a subset of the available transmit antennas). For simplicity RX MIMO processor 556h / data is described for said processing circuit when transmitting.
Each stage 710, receiver processing (except for the last stage 710n) includes a channel MIMO processor 720 / data related to the noise suppressor 730, and the last stage 710n includes only channel MIMO processor 720 / data. The first processing stage 710a when receiving channel MIMO processor 720 / receives the data and processes the NR modulation symbol streams from demodulators 554a through 554r to provide a decoded data stream for the first transmission channel (or the first transmitted signal). And for each stage, the second channel 710b 710n for MIMO processor 720 / data at these stages receives and processes the NR modified symbol streams from the interference canceller 730 prior processing stage for obtaining a decoded data stream for the transmission channel being processed at this stage. Each channel processor 720 MIMO / data further provides CSI (e.g., SNR) for the associated transmission channel.
For the first stage 710a receiver processing interference canceller 730a receives the NR modulation symbol streams from all NR demodulators 554. And for each stage of the second to penultimate, interference canceller 730 receives the NR modified symbol streams from the preceding stage interference canceller. Each interference canceller 730 also receives and decodes the data stream from channel processor 720 MIMO / data of the same stage, and performs the processing (e.g., coding, interleaving, modulation, channel response receipt, etc.) to obtain NR remodulated symbol streams that They are estimates of the interference components of the received modulation symbol streams due to this decoded data stream. Remodulated symbol streams are then subtracted from the received modulation symbol streams to obtain NR modified symbol streams that include all but the subtracted (i.e., remote) interference components. NR modified symbol streams are then provided to the next stage.
Figure 7 shows a controller 740 associated with RX processor 556h MIMO / data, and it can be used to control various stages in the processing with successive cancellation receiver executed by the processor 556h.
7 shows a receiver structure that may be used directly, if each data stream is transmitted over a respective transmit antenna (i.e., each transmitted signal corresponds to one data stream). In this case each processing stage 710 can operate at reception, restoring one of the transmitted signals and obtaining decoded data stream corresponding to the recovered transmitted signal. For some other processing circuits in the transmission data stream can be transmitted over multiple transmit antennas, frequency subchannels, and / or time intervals to provide, respectively, frequency and time diversity. For these circuits, first receiver processing provides a stream of received modulation symbols for the signal transmitted by each transmit antenna of each frequency subchannel. Modulation symbols for multiple transmit antennas frequency subchannels and / or time intervals may then be combined in a manner complementary to the demultiplexing process, performance of the base station. Then, the combined stream of modulation symbols is processed to obtain a corresponding decoded data stream.
FIG. 8A is a block diagram of an embodiment of channel MIMO processor 720h / data, which is one embodiment of channel MIMO processor 720/7 data. In this embodiment, channel MIMO processor 720h / data includes a spatial / space-time processor 810, CSI processor 812, a selector 814, a demodulation unit 816, deinterleave unit 818, and a decoder 820.
Spatial / space-time processor 810 performs linear spatial processing on the NR received signals for a non-dispersive MIMO channel (i.e., with flat fading) or space-time processing on the NR received signals for a dispersive MIMO channel (i.e., fading, independent of frequency). Spatial processing may be performed using the techniques of linear spatial processing techniques such as a method for the inversion of the correlation matrix of the channel (CCMI), a minimum mean error (MMSE), and so on. These methods can be used to eliminate undesired signals or to maximize the received SNR of each of the component signals in the presence of noise and interference from other signals. Spatio-temporal processing may be performed using methods linearly-time processing such as a MMSE linear equalizer (MMSE-LE), a decision feedback coupling (DFE), the device estimates a maximum-likelihood sequence (MLSE), and others. Methods CCMI, MMSE, MMSE-LE and DFE are described in more detail in the aforementioned US patent application number [Attorney Docket No. PA010210]. Methods MLSE and DFE are also described in more detail SL Ariyavistakul et.al. in the work entitled "Optimum Space-Time Processor with Dispersive Interference: Unified Analysis and Required Filter Span", IEEE Trans. On Communication, Vol.7, №7, July 1999 and which is incorporated herein in its entirety by reference.
The processor determines the ISK 812 ISK for each transmission channel used for data transmission. For example, CSI processor 812 may estimate a noise covariance matrix based on the received pilot signals and then compute the SNR for the k-th transmission channel used for the data stream for decoding. SNR may be estimated using methods analogous to using a pilot signal in systems with a single and multicarrier known in the art. SNR for all transmission channels used for data transmission may comprise the CSI that is reported to the base station of said transmission channels. CSI processor 812 further produces a selector control signal 814 that identifies the particular data stream for restoration on this receiver processing stage.
Selector 814 receives a number of symbol streams from spatial / space-time processor 810 and extracts the symbol stream corresponding to the data stream for decoding, which is indicated by the control signal processor 812 KIU. The separated stream of modulation symbols is then provided to a demodulation element 814.
For the embodiment shown in Figure 6, wherein the data stream for each transmission channel independently coded and modulated based on the channel SNR, the recovered modulation symbols for the selected transmission channel are demodulated according to a demodulation scheme (e.g., M-PSK, M-QAM) which is complementary to the modulation scheme used in the transmission channel. The demodulated data from demodulation element 816 deinterleaves a deinterleaving unit 818 in a manner complementary to the interleaving performed by the device channel 614 and further data, deinterleaved, decoded by a decoder 820 in a manner complementary executable by encoder 612. For example, as the decoder 820 may apply turbo decoder or a Viterbi decoder if the base station is applied, respectively, turbo coding or convolutional coding. The flow of the decoded data from the decoder 820 represents an estimate of the transmitted data stream, recovered at this time.
8B is a block diagram of noise suppressor 730h, which is an embodiment of interference canceller 730 7. The suppressor 730h interference decoded data stream from channel processor 720 MIMO / data of the same stage is re-encoded, interleaved, and re-modulating the channel processor 610h data for characters remodulating, which are estimates of the modulation symbols at the base station to the MIMO processing and distortion in channel. Channel data processor 610h performs the same processing (e.g., coding, interleaving, and modulation), which is performed in the base station for the data stream. Re-modulating the symbols are then provided to a channel simulator 830, which processes the modulation symbols together with the channel response estimates to obtain the estimates, noise associated with a stream of decoded data. The channel response estimate may be derived based on pilot and / or data on the data transmitted by the base station in accordance with the methods described in the aforementioned US patent application number [Attorney Docket No. PA010210]. NR interference vector elements correspond to the components of the received signal at each of the NR receive antennas are associated with a stream of symbols transmitted through the k-th transmit antenna. Each element of the vector represents an estimate of the component associated with the decoded data stream in the corresponding received modulation symbol stream. These components are interference to the remaining (not yet detected) transmitted signals in the NR received modulation symbol streams (i.e., vector), and are subtracted (i.e., removed) from the received signal vector adder 832 to produce modified vectors with remote components corresponding decoded data stream. The modified vector is supplied as an input vector to the next receiver processing stage, as shown in Figure 7.
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Various aspects of the processing in successive cancellation receiver described in more detail in the aforementioned US patent application number [Attorney Docket No. PA010210].
Receiver design that does not use a method of processing with successive cancellation receiver may also be used to receive, process, and recover the transmitted data streams. Several designs of receivers described in the aforementioned US patent applications №№ 09 / 776.075 and 09 / 826.481 and US Patent №09 / 532,492, entitled "HIGH EFFICIENCY, HIGH PERFORMANCE COMMUNICATIONS SYSTEM EMPLOYING MULTI-CARRIER MODULATION", filed March 30, 2000 , assigned to the assignee hereof and which is incorporated herein in its entirety by reference.
For simplicity, various aspects and embodiments of the invention have been described on the assumption that the claim is a SNR. In general, the CSI may comprise any type of information that reflects the characteristics of the communication link. The CSI can be used as various types of information, some examples of which are described below.
In one embodiment, the CSI comprises a signal / noise-plus-interference (SNR), which is calculated as the ratio of signal power to interference plus noise power. Typically SNR estimated and provided for each transmission channel used for data transmission (e.g., each transmit data stream), although it may also be represented by a complex number of the SNR for the transmission channels. Qualification SNR can be expressed as a numerical value represented by a certain number of bits. In one embodiment, the SNR estimate is converted to a SNR index, e.g., using a conversion table.
In another embodiment, the CSI comprises signal power and interference plus noise power. These two components can be separately determined and provided for each transmission channel used for data transmission.
In another embodiment, the CSI comprises signal power, interference power and noise power. These three components may be determined and provided for each transmission channel used for data transmission. In another embodiment, the CSI comprises signal / noise ratio plus a list of interference powers for each observable interference element. This information may be determined and provided for each transmission channel used for data transmission.
In another embodiment, the CSI comprises signal components in a matrix form (e.g., NTxNR complex entries for all pairs (transmitting antenna - receiver antenna), and component noise plus interference in a matrix form (e.g., NTxNR complex entries). The base station may then combine in a suitable form signal components and noise plus interference components for the corresponding pair of the transmitting antenna - receiver antenna to determine the quality for each transmission channel used for data transmission (e.g., after processing SNR for each transmitted data stream received by the terminal).
In another embodiment, the CSI comprises a data rate indicator for the stream of data transmitted. The quality of the transmission channel for transmitting data can be determined internally (e.g., based on SNR, estimated for the transmission channel) and can then be identified by a data rate corresponding to a specific channel quality (e.g., based on the conversion table). The identified data rate represents the maximum data rate which can transmit the transmission channel at the desired performance level. Then, the data rate is converted to a data rate indicator (DRI - ISPD) which can be efficiently encoded, and they appear. For example, if the base station for each transmit antenna supported by seven (seven) possible data rates, while for the representation can be used ISPD three-bit number, where, for example, 0 may indicate a null data rate (i.e., failure to transmit antenna) and from 1 to 7 may be used to indicate seven different data rates. In the conventional implementation of quality measurements (e.g., SNR estimates) are converted directly into ISPD based, for example, the conversion table.
In another embodiment, the CSI comprises power control information for each transmission channel. The power control information may include a single bit for each transmission channel to indicate a request for a power increase or a power decrease, or it may include multiple bits to indicate the magnitude of the change of the requested power level. In this embodiment, the base station may use the power control information fed back from terminals to adjust the data processing and / or transmission power.
In another embodiment, the CSI comprises an indicator specific processing schemes to be used in the base station for each transmitted data stream. In this embodiment, the indicator may identify the particular coding scheme and the particular modulation scheme used to transmit the data stream, so that when this is achieved the required level of performance.
In another embodiment, the CSI comprises various indicators for measuring the quality of a particular channel. Initially ISPD or SNR, or any other numerical characteristic of the transmission channel is determined and reported as a reference value characteristic. After that, it continues to monitor the quality of the transmission channel and is determined by the difference between the latest posts characteristic and current characteristic. Then, the difference may be digitized into one or more bits, and the difference is converted to a digitized LED differences and they appear, then the reported indicator. Indicator differences may indicate increase or decrease of the latest posts on the specific characteristics of the step size (or confirm the latest posts characteristics). For example, the indicator may indicate differences that (1) the observed SNR for a particular transmission channel has increased or decreased by a particular step size, or (2) the data rate should be adjusted by a particular amount, or some other change. The reference values of characteristics may be transmitted periodically to ensure that errors in the differences indicators and / or erroneous determination of these indicators do not accumulate.
Other forms of CSI may also be used and are within the scope of the present invention. In general, the CSI includes essential information in the form in which it can be used for adjustment processing in the base station, so that a desired level of performance for the transmission data streams.
Contents5
Every citation, both ways
| Document | Relation | Office | Cited during |
|---|---|---|---|
| US8509162B2 | Cited by | United States of America | Applicant |
| US9838184B2 | Cited by | United States of America | Applicant |
| RU2613526C1 | Cited by | Russian Federation | Search report |
| RU2510596C2 | Cited by | Russian Federation | Search report |
| US8798183B2 | Cited by | United States of America | Applicant |
| US11895053B2 | Cited by | United States of America | Applicant |
| RU2706805C1 | Cited by | Russian Federation | Search report |
| RU2509430C2 | Cited by | Russian Federation | Search report |
| US11398887B2 | Cited by | United States of America | Applicant |
| US8553667B2 | Cited by | United States of America | Applicant |
| RU2607238C2 | Cited by | Russian Federation | Search report |
| RU2469490C2 | Cited by | Russian Federation | Search report |
41 members in 19 offices
Priority claims4
| Document | Office | Kind | Date |
|---|---|---|---|
| 85934501 | United States of America | A | |
| 85934501 | United States of America | A | |
| 09859345 | – | – | – |
| US20010859345 | – | – | – |
Members41
| Document | Office | Kind | |
|---|---|---|---|
| CA2446877A1 | Canada | A1 | |
| WO02093819A1 | World Intellectual Property Organization (WIPO) | A1 | |
| US2003087673A1 | United States of America | A1 | |
| TW545074B | Taiwan Province of China | B | |
| NO20035072D0 | Norway | D0 | |
| US6662024B2 | United States of America | B2 | |
| KR20030096405A | Republic of Korea | A | |
| EP1388231A1 | European Patent Office (EPO) | A1 | |
| MXPA03010414A | Mexico | A | |
| IL158760A0 | Israel | A0 | |
| IL158760D0 | Israel | D0 | |
| CN1522512A | China | A | |
| BR0209636A | Brazil | A | |
| JP2004535106A | Japan | A | |
| HK1065665A | Hong Kong, China | A | |
| HK1065665A1 | Hong Kong, China | A1 | |
| RU2003136165A | Russian Federation | A | |
| UA74882C2 | Ukraine | C2 | |
| RU2294599C2This record | Russian Federation | C2 | |
| AU2002309974B2 | Australia | B2 | |
| EP1388231B1 | European Patent Office (EPO) | B1 | |
| AT365405T | Austria | T | |
| ATE365405T1 | Austria | T1 | |
| US7248879B1 | United States of America | B1 | |
| DE60220783D1 | Germany | D1 | |
| EP1830509A2 | European Patent Office (EPO) | A2 | |
| ES2287282T3 | Spain | T3 | |
| US2008013638A1 | United States of America | A1 | |
| DE60220783T2 | Germany | T2 | |
| IL158760A | Israel | A | |
| EP1830509A3 | European Patent Office (EPO) | A3 | |
| CN100505607C | China | C | |
| KR100938302B1 | Republic of Korea | B1 | |
| JP4537004B2 | Japan | B2 | |
| US7907972B2 | United States of America | B2 | |
| US2011261899A1 | United States of America | A1 | |
| CA2446877C | Canada | C | |
| US8489107B2 | United States of America | B2 | |
| EP1830509B1 | European Patent Office (EPO) | B1 | |
| ES2436766T3 | Spain | T3 | |
| BRPI0209636B1 | Brazil | B1 |
Numbers
- Publication, DOCDB
- 2294599
- Publication, EPODOC
- RU2294599
- Application
- 200313616509
- Application, DOCDB
- 2003136165
- Application, EPODOC
- RU20030136165
Titles2
- English
- METHOD AND DEVICE FOR DISTRIBUTING RESOURCES IN COMMUNICATION SYSTEM WITH MULTIPLE INPUTS AND OUTPUTS
- Russian
- СПОСОБ И УСТРОЙСТВО ДЛЯ РАСПРЕДЕЛЕНИЯ РЕСУРСОВ В КОММУНИКАЦИОННОЙ СИСТЕМЕ С МНОЖЕСТВЕННЫМИ ВХОДАМИ И МНОЖЕСТВЕННЫМИ ВЫХОДАМИ
Classification
- CPC, 13
- H04W16/00
- H04W72/1273
- H04B7/0417
- H04B7/0452
- H04B7/061
- H04L1/0003
- H04L1/0009
- H04L1/0026
- H04L1/06
- H04L25/0204
- H04L2025/03426
- H04W16/28
- H04W84/14
- IPC, 8
- H04L1 00
- H04B7 04
- H04B7 06
- H04J99 00
- H04L1 06
- H04W16 00
- H04W16 28
- H04W84 14