Reverse link power control for an ofdma system
Abstract
An apparatus comprising: means (912) for sending a first signal through a reference channel, using a first radio technology, characterized in that the apparatus additionally comprises: means (914) for sending a second signal through a second channel, using a second radio technology that is different from the first radio technology; means (916) for adjusting a transmission power of the reference channel, at least in part, to achieve a desired level of performance for the reference channel; and means (918) for adjusting a transmission power of the second reference channel, based, at least in part, on a spectral density of transmission power, PSD, of the reference channel.

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16 claims: 1 independent, 15 dependent
- 1REIVINDICACIONES 1. Un aparato que comprende:medios (912) para enviar una primera señal por un canal de referencia, usando una primera tecnología de radio, caracterizado porque el aparato comprende adicionalmente: medios (914) para enviar una segunda señal por un segundo canal, usando una segunda tecnología de radio que es distinta a la primera tecnología de radio;medios (916) para ajustar una potencia de transmisión del canal de referencia, al menos en parte, para lograr un nivel deseado de prestaciones para el canal de referencia;y medios (918) para ajustar una potencia de transmisión del segundo canal de referencia, en base, al menos en parte, a una densidad espectral de potencia de transmisión, PSD, del canal de referencia.
- 2El aparato de la reivindicación 1, que comprende:al menos un procesador configurado: para transmitir el canal de referencia usando la primera tecnología de radio, para transmitir el segundo canal usando la segunda tecnología de radio, que es distinta a la primera tecnología de radio, para ajustar la potencia de transmisión del canal de referencia, al menos en parte, para lograr el nivel deseado de prestaciones para el canal de referencia, y para ajustar la potencia de transmisión del segundo canal, en base, al menos en parte, a la PSD de transmisión del canal de referencia;y una memoria acoplada a dicho al menos un procesador.
- 3El aparato de la reivindicación 2, en el cual la primera tecnología de radio es el Acceso Múltiple por División del Código, CDMA, y la segunda tecnología de radio es el Acceso Múltiple por División Ortogonal de Frecuencia, OFDMA.
- 4El aparato de la reivindicación 2, en el cual el canal de referencia lleva señalización y el segundo canal lleva datos de tráfico.
- 5El aparato de la reivindicación 2, en el cual dicho al menos un procesador está configurado para recibir comandos de control de potencia, PC, para el canal de referencia, y para ajustar la potencia de transmisión del canal de referencia en base a los comandos de PC recibidos.
- 6El aparato de la reivindicación 5, en el cual los comandos de PC son generados, al menos en parte, para alcanzar una calidad deseada de señal recibida para el canal de referencia.
- 7El aparato de la reivindicación 2, en el cual el nivel deseado de prestaciones para el canal de referencia está basado, al menos en parte, en una tasa de borrado deseada para una o más palabras código enviadas por el canal de referencia.
- 8El aparato de la reivindicación 2, en el cual dicho al menos un procesador está configurado para recibir una o más indicaciones de borrado para una o más palabras código enviadas por el canal de referencia, y para ajustar la potencia de transmisión del canal de referencia, en base, al menos en parte, a dicha(s) indicación(es) de borrado.
- 9El aparato de la reivindicación 2, en el cual dicho al menos un procesador está(n) configurado(s) para aumentar la potencia de transmisión del canal de referencia, en un paso hacia arriba, en respuesta a una palabra código enviada por el canal de referencia, detectada como un borrado, y para reducir la potencia de transmisión del canal de referencia, en un paso hacia abajo, en respuesta a la palabra código enviada, detectada como no borrada.
- 10El aparato de la reivindicación 9, en el cual los pasos hacia arriba y hacia abajo son seleccionados en base, al menos en parte, a una tasa de borrado deseada para el canal de referencia.
- 11El aparato de la reivindicación 2, en el cual dicho al menos un procesador está(n) configurado(s) para ajustar un valor de delta de PSD, en base, al menos en parte, a uno o más valores de estimación de interferencia, y para fijar la potencia de transmisión del segundo canal, en base, al menos en parte, al valor ajustado de la delta de PSD.
- 12El aparato de la reivindicación 2, en el cual dicho al menos un procesador está(n) configurado(s) para ajustar un valor de delta de PSD, en base, al menos en parte, a una o más estimaciones de interferencia, a fin de determinar una PSD de transmisión del segundo canal, en base, al menos en parte, a la delta de PSD de transmisión y a la PSD de transmisión del canal de referencia, y fijar la potencia de transmisión del segundo canal, al menos en parte, para alcanzar la PSD de transmisión del segundo canal.
- 13El aparato de la reivindicación 2, en el cual el canal de referencia lleva información de indicación de calidad de canal, 5 CQI.
- 14Un procedimiento que comprende:enviar (812) una primera señal por un canal de referencia, usando una primera tecnología de radio, caracterizado porque el procedimiento comprende adicionalmente: enviar (814) una segunda señal por un segundo canal usando una segunda tecnología de radio que es distinta a la 10 primera tecnología de radio;ajustar (816) una potencia de transmisión del canal de referencia, al menos en parte, para alcanzar un nivel deseado de prestaciones para el canal de referencia;y ajustar (818) una potencia de transmisión del segundo canal, en base, al menos en parte, a una densidad espectral de potencia, PSD, transmisora del canal de referencia. 15 15. El procedimiento de la reivindicación 14, en el cual el ajuste de la potencia de transmisión del canal de referencia comprende recibir uno o más comandos de control de potencia, PC, para el canal de referencia, y ajustar la potencia de transmisión del canal de referencia en base, al menos en parte, a dicho(s) comando(s) de PC.
- 16El procedimiento de la reivindicación 14, en el cual al ajuste de la potencia de transmisión del canal de referencia comprende recibir una o más indicaciones de borrado para una o más palabras código enviadas por el canal de 20 referencia, y ajustar la potencia de transmisión del canal de referencia en base, al menos en parte a dicha(s) indicación(es) de borrado.
- 17El procedimiento de la reivindicación 14, en el cual el ajuste de la potencia de transmisión del segundo canal comprende ajustar un valor de delta de PSD en base a uno o más valores de estimación de interferencia, y fijar la potencia de transmisión del segundo canal en base, al menos en parte, al valor ajustado de la delta de PSD. 25 18. Un medio legible por un procesador, que incluya instrucciones en el mismo que puedan ser utilizadas por uno o más procesadores para realizar todas las etapas del procedimiento de una cualquiera de las reivindicaciones 14 a 17.
Independent claims16
243 paragraphs, as filed
Reverse link power control for an OFDMA system
Background
I. Field
The present disclosure relates, in general, to communication and, more specifically, to power control in a wireless communication system.
II. Background
A multi-access wireless communication system can communicate with multiple terminals through direct and reverse links. The direct link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations.
Multiple terminals can simultaneously receive data on the direct link and / or transmit data on the reverse link. This can be achieved by multiplexing the transmissions by each link so that they are orthogonal to each other in the domain of time, frequency and / or code. In the reverse link, full orthogonality, if achieved, results in that the transmission from each terminal does not interfere with the transmissions from other terminals in a receiving base station. However, full orthogonality between transmissions from different terminals is often not performed, due to channel conditions, receiver imperfections, etc. The loss of orthogonality results in each terminal causing a certain amount of interference to other terminals in communication with the same base station. In addition, transmissions from terminals that communicate with different base stations are usually not orthogonal to each other. In this way, each terminal can also cause interference to other terminals in communication with nearby base stations. The performance of each terminal is degraded by interference from all other terminals in the system.
There is, therefore, a need in technology technology to control the transmission power of the terminals, in order to reduce interference and achieve good performance for all terminals.
US 2004/179494 A1 describes a technique for determining the transmission power for a traffic channel, based on a transmission power for a pilot channel.
WO 2004/025869 A2 describes a technique for determining whether or not a station has sufficient power to transmit on a communication channel, determining whether a power value for the communication channel (based on a reference level value of pilot signal and several other factors) is or is not less than a ratio between a maximum transmission power and a slack value.
EP 1467498 A1 describes a technique for determining the transmission power for second channels, based on the transmission power for first channels and a maximum total load of a transmission power amplifier (which is used to provide transmission power for the first and second channels).
Document US 2005/053031 A1 describes a technique for forecasting the transmission power level for each user of data of a second type of channel, and determining the power level for a first type of channel, multiplying the expected level of power of transmission by profit factors.
US 2002/163974 A1 describes a technique for mitigating far-end crosstalk interference between channels in a communication system, by generalizing the reference length and equalized FEXT procedures.
Summary
Aspects of the present invention are defined in the independent claims.
Techniques for controlling the transmission power of control and data channels in a wireless communication system are described herein. In one example, the power control (PC) is performed for a reference channel sent using a first radio technology, as well as for a second channel sent using a second radio technology. The reference channel can be a control channel that carries signaling and can be sent using Multiple Code Division Access (CDMA). The second channel can be a data channel that carries traffic data, and can be sent using the Multiple Access by Orthogonal Frequency Division (OFDMA). The transmission power of the reference channel is adjusted to achieve a desired level of performance for the reference channel, which can be quantified by a desired erase rate. The transmission power of the second channel
It is adjusted based on the transmission power of the reference channel.
In another example, the power control is performed for a control channel, e.g. eg, an acknowledgment channel (ACK), without using explicit feedback for the control channel. A reference transmission power level is determined, which may be the transmission power of the reference channel. Signaling errors sent by the control channel are detected, e.g. e.g., implicitly, without receiving feedback indicating errors. The signaling can be ACKs, and ACK errors sent by the control channel can be detected based on the data packets received by a data channel. The transmission power of the control channel is adjusted to the reference transmission power level and the errors detected in the control channel.
In another example, the power control is performed for a data channel. A reference power spectral density (PSD) level is determined, e.g. eg, based on the transmission power of the reference channel. A delta of the transmission PSD is set for the data channel, e.g. eg, based on interference estimates. A transmission PSD of the data channel is determined based on the reference PSD level and the transmission PSD delta. The transmission power of the data channel can then be determined based on the transmission PSD and the number of subcarriers used for the data channel.
Various aspects and embodiments of the disclosure are described in greater detail below.
Brief description of the drawings
The characteristics and nature of the present disclosure will become more apparent from the detailed description set forth below, when considered in conjunction with the drawings, in which the same reference characters identify correspondingly throughout their length.
FIG. 1 shows a wireless communication system.
FIG. 2 shows an exemplary superframe structure.
FIG. 3 shows an H-ARQ transmission scheme for the direct link.
FIG. 4 shows a power control mechanism for a top-down PC scheme.
FIG. 5 shows a power control mechanism for a PC scheme based on deletions.
FIG. 6 shows a power control mechanism for an ACK channel.
FIG. 7 shows a power control mechanism for a data channel.
FIGS. 8 and 9 show, respectively, a procedure and an apparatus for performing power control in a system using multiple radio technologies.
FIGS. 10 and 11 show, respectively, a method and an apparatus for performing power control for a control channel, e.g. eg, an ACK channel.
FIGS. 12 and 13 show, respectively, a procedure and an apparatus for performing power control for a data channel.
FIG. 14 shows a block diagram of one terminal and two base stations.
Detailed description
The word "exemplary" is used herein to mean "that serves as an example, case or illustration." Any embodiment or design described herein as "exemplary" should not necessarily be construed as preferred or advantageous over other embodiments or designs.
FIG. 1 shows a wireless communication system 100 with multiple base stations 110 and multiple terminals
120. A base station is a station that communicates with the terminals. A base station may also be called, and may contain some, or all, of the functionality of an access point, a Node B and / or some other network entity. Each base station 110 provides communication coverage for a specific geographic area 102. The term "cell" may refer to a base station and / or its coverage area, depending on the context in which the term is used. To improve system capacity, a base station coverage area can be divided into multiple smaller areas, e.g. eg, three smaller areas 104a, 104b and 104c. Each smaller area is served by a respective base transceiver subsystem (BTS). The term "sector" may refer to a BTS and / or its coverage area, depending on the context in which the term is used. For a sectorized cell, the BTS for all sectors of that cell are usually cosituted within the base station for the cell.
Terminals 120 are usually dispersed throughout the entire length of the system, and each terminal can be fixed or mobile. A terminal may also be called, and may contain some, or all, of the functionality of an access terminal, a mobile station, a user equipment and / or some other entity. A terminal can be a wireless device, a cell phone, a personal digital assistant (PDA), a wireless modem, a portable device, etc. A terminal can communicate with zero, one or multiple base stations through the direct and / or reverse link at any given time.
For a centralized architecture, a system controller 130 is coupled to base stations 110 and provides coordination and control for these base stations. The system controller 130 may be a single network entity or a collection of network entities. For a distributed architecture, base stations can communicate with each other as necessary.
The power control techniques described herein can be used for a system with sectorized cells, as well as a system with non-sectorized cells. For clarity, the techniques are described below for a system with sectorized cells. In the following description, the terms "base station" and "sector" are used interchangeably, and the terms "terminal" and "user" are also used interchangeably.
The power control techniques described herein can also be used for various wireless communication systems and various radio technologies, such as Orthogonal Frequency Division Multiple Access (OFDMA), Carrier Frequency Division Multiple Access Single (SC-FDMA), Multiple Access by Code Division (CDMA), Multiple Access by Time Division (TDMA), Multiple Frequency Division Access (FDMA), etc. OFDMA and SC-FDMA divide a frequency band (e.g., system bandwidth) into multiple orthogonal subcarriers, which are also called tones, compartments, etc. Each subcarrier can be modulated with data. In general, modulation symbols are sent in the frequency domain with OFDMA and in the time domain with SC-FDMA. The techniques can also be used for wireless communication systems that use multiple radio technologies. For clarity, the techniques are described below for a system that uses OFDMA for data channels and CDMA for some control channels.
FIG. 2 shows an exemplary superframe structure 200 that can be used for the reverse link in the system
100 The transmission time line for the reverse link is divided into units of superframes. Each superframe covers a fixed or configurable time duration, and includes M frames, where M> 1. Each frame can carry traffic and / or signaling data. The superframe structure for the direct link may be the same or different from the superframe structure for the reverse link.
FIG. 2 also shows an embodiment of a CDMA control segment for a carrier that is divided into four subbands. In this embodiment, the CDMA control segment carries certain types of signaling and is sent in a subband in every 6th frame. A CDMA frame is a frame in which the CDMA control segment is sent. The CDMA control segment is correlated with a temporal frequency region that covers F subcarriers and covers T periods of symbols, where both F and T can be any integer value. In general, the CDMA control segment can be sent at any speed and in a time frequency region of any dimension. The CDMA control segment can jump between frequency values, as shown in FIG. 2, or it can be static in frequency.
FIG. 2 also shows an exemplary scheme of frequency hops for data channels. A data channel is a means to send data from a transmitter to a receiver, and it can also be called a traffic channel, a physical channel, etc. Each data channel can be correlated with a specific sequence of time frequency blocks that jump between frequency values in different frames, to achieve frequency diversity, as shown in FIG.
two. In one embodiment, the frequency hopping for the data channels avoids the CDMA control segment. A set of subcarriers can be awarded for the CDMA control segment. Each data channel that collides with the CDMA control segment can be correlated with the set of subcarriers assigned to the CDMA control segment.
Various control channels can be defined and used to carry various types of signaling on the reverse link. Reverse link control channels may include the following:
<dl><dt>* </dt><dd>ACK channel - carries ACK for data packets received by the direct link, </dd></dl>
<dl><dt>* </dt><dd>CQI Channel - carries direct link signal quality information, </dd></dl>
<dl><dt>* </dt><dd>Request channel - carries resource requests through the reverse link, </dd></dl>
<dl><dt>* </dt><dd>Pilot channel - carries a broadband pilot signal for the reverse link, and </dd></dl>
<dl><dt>* </dt><dd>Access channel - carries access probes to access the system. </dd></dl>
Different and / or additional channels can also be sent through the reverse link.
In general, various channel structures can be used to send traffic and signaling data. In an embodiment described below, the reverse link uses the OFDMA for data channels that carry traffic data, and the CDMA is used for most control channels. In one embodiment, the CDMA control segment carries the CQI, Request, Pilot and Access channels, and the ACK channel is sent along with a reverse link data channel. Control channels can also be sent in other ways.
FIG. 3 shows an exemplary scheme 300 of transmission of hybrid automatic retransmission (H-ARQ) requests for the direct link in the system 100. A terminal measures the quality of the signal received from the direct link for a base station, generates an indication report of channel quality (CQI), associates the CQI report with a code word and transmits the code word through the CQI channel (not shown in FIG. 3). The signal quality can be quantified by a ratio between signal and noise (SNR), a ratio between signal and noise and interference (SINR), a ratio between carrier and interference (C / I), a ratio between energy per symbol and noise (It is / No), etc. For clarity, the SNR is used to indicate the signal quality in the description below.
The base station receives the CQI code word from the terminal and selects a packet format (eg, a data rate, a packet size, etc.) to be used for data transmission to the terminal. The base station then processes (e.g., encodes and modulates) a data packet (Package A) according to the selected packet format and generates multiple blocks of data for the packet. Each block of data may contain enough information to allow the terminal to decode the packet correctly in favorable channel conditions. Multiple data blocks usually contain different redundancy information for the packet, and can be sent one block at a time, until the packet is finished. Each block transmission is also called an H-ARQ attempt. Each block transmission after the first block is also called a retransmission.
The base station transmits the first data block (Block A1) of Package A in frame n. The terminal receives and processes (e.g., demodulates and decodes) Block A1, determines that Package A is decoded with errors, and sends a negative acknowledgment (NAK) through the ACK channel in frame n + 3 The base station receives the NAK and transmits the second data block (Block A2) of Package A in frame n + 6. The terminal receives Block A2, processes Blocks A1 and A2; determines that Package A is decoded correctly and sends an ACK in frame n + 9. The base station receives the ACK and terminates the transmission of Package A. The base station processes the next data packet (Package B) and transmits the blocks of Package B data similarly.
FIG. 3 shows a specific embodiment of the transmission of data blocks, CQI and ACK / NAK. In this embodiment, traffic data is sent in every 6th frame, a CQI report is also sent in every 6th frame, and an ACK is sent if a packet is properly decoded. Data and signaling can also be sent in other ways, e.g. eg, at different speeds, with a different interval between block transmissions, with a different delay for ACK / NAK, etc. For example, a CQI report can be sent every CDMA frames, where any positive integer value can be.
For clarity, FIG. 3 shows the transmission of both NAKs and ACKs through the ACK channel. For an ACK-based scheme, an ACK is sent if a packet is properly decoded, and the NAKs are not sent, and are understood by the absence of the ACKs. For a NAK-based scheme, a NAK is sent if a packet is decoded with errors, and ACKs are not sent. For clarity, the following description assumes the use of an ACK-based scheme, and only ACKs are sent for correctly decoded packets.
The data channels are sent using the OFDMA and are orthogonal to each other on the frequency. In general, data channels minimally interfere with each other at a receiving base station, and there is little intrasectoral interference between users transmitting on these data channels. Consequently, users located closer to the base station (or “indoor” users) can potentially be received at a higher power spectral density (PSD), with little impact on other users in the same sector, because their channels of data are orthogonal to each other and there is no "near-far" effect. Internal users may also have little impact on users in other sectors, due to greater path losses to neighboring base stations. An objective of reverse link power control is to maximize data capacity under restrictions of complexity, over-cost and stability.
In one aspect, closed loop power control is performed for a reference channel, and power control for other data and control channels is referred to the reference channel. The reference channel can be any channel that is sent at a speed sufficient to allow reliable adjustment of the transmission power of the reference channel. In an embodiment described below, the reference channel is the CQI channel, which has a relatively constant low data rate, as shown in FIG. 3.
1. Power control for the CQI channel
A CQI report, or signaling, to be sent on the CQI channel in a given frame may be a small word containing L bits, where, in general, L> 1 and, p. eg, L = 10. This word can be correlated with one between 2L possible code words in a code book. The code word is then sent by the CQI channel in frame n. The same number of bits (eg, L bits) can be sent for each CQI report. In this case, the same codebook can be used for each CQI report. Alternatively, different numbers of bits may be sent for different CQI reports, and different codebooks may be used, depending on the number of bits that are sent. The code words in a given code book can be generated based on a block code or some other correlation scheme. In one embodiment, the 2L possible code words correspond to 2L Walsh codes of length 2L.
A base station receives the code words sent by the CQI channel. The base station performs the complementary decoding on each received code word, to obtain a decoded word, which is a word considered to have been sent, most likely, for the received code word. Decoding can be done in various ways. In one embodiment, the base station calculates a Euclidean distance between the received code word and each of the 2L possible valid code words in the codebook. The valid code word with the shortest Euclidean distance to the received code word can be considered as the transmitted code word. The word corresponding to this valid code word can be provided as the decoded word.
An error detection code cannot be used for the CQI channel, e.g. eg, due to the small word size. In this case, there is no direct way to determine if the decoding of a given code word received is correct or has errors, and if the decoded word is effectively the transmitted word. A metric can be defined and used as an indication of confidence in the decoding result. In one embodiment, the metric is defined as:
Ec. (1)
where
d1 (n) is the Euclidean distance between the code word received in the frame and the closest valid code word,
d2 (n) is the Euclidean distance between the code word received in the frame n and the next closest valid code word, and
M (n) is the metric for the code word received in frame n.
If the received code word is much closer to the nearest valid code word than the next closest valid code word, then the metric M (n) is a small value and there is a high degree of confidence that the decoded word be correct On the contrary, if the received code word has a distance approximately equal to the nearest valid code word and the next nearest valid code word, then the metric M (n) approaches one, and there is less confidence that The decoded word is correct.
The metric in equation (1) can be used for the detection of deletions, which is to determine if the decoding of a given code word received is correct or has errors. Other metrics can also be used for deletion detection. In general, a metric can be defined based on any reliability function f (r, C), where r is a received code word and C is a code book of all possible code words. The function f (r, C) should be indicative of the quality / reliability of the received code word, and should have the appropriate characteristics, e.g. eg, be monotonous with detection reliability.
The base station can perform deletion detection to determine whether or not the decoding result for a received code word satisfies a desired level of trust. The base station can calculate the metric for the received code word, compare the metric with the delete threshold and declare that the received code word is "deleted" or "not deleted", according to the following:
If M (n) <TH deleted, then declare a code word not deleted, Eq. (2)
If M (n)> TH deleted, then declare a deleted code word,
where TH deleted is the threshold used for deletion detection. In general, deletion detection depends on how the metric is defined and may be different from equation (2) for other metrics.
The probability of declaring a received code word as a deleted code word is called an erase rate. The deletion rate depends on various factors, such as the threshold used for the detection of deletions and the SNR received from the received code word. For a given received SNR, a lower deletion threshold increases the probability that a received code word will be declared as a deleted code word, and vice versa. For a given deletion threshold, a lower SNR received increases the probability that a received code word will be declared as a deleted code word, and vice versa.
The transmission power of the CQI channel can be adjusted in various ways. In one embodiment, which is called a "top-down" PC scheme, a base station measures the SNR received from the CQI channel and sends PC bits or PC commands to direct a terminal to adjust the transmission power of the CQI channel. In another embodiment, which is called a "delete-based" PC scheme, the base station sends CQI erase indication bits (IEC), or erase indications indicating the results of the erase detection at the base station. The terminal adjusts the transmission power of the CQI channel based on the CEI bits. For both PC schemes, the transmission power of the CQI channel can be adjusted so that the CQI channel can achieve the desired level of performance, which can be quantified by a desired erase rate and / or some other measures.
FIG. 4 shows an embodiment of a power control mechanism 400 that implements the top-down PC scheme for the CQI channel. The power control mechanism 400 includes an internal loop 410, an external loop 412 and a third loop 414. The internal loop 410 operates between a base station 110x and a terminal 120x. The external loop 412 and the third loop 414 are maintained by the base station 110x. The base station 110x can be any of the base stations 110 in FIG. 1, and terminal 120x may be any of terminals 120 in FIG. 1.
The internal loop 410 adjusts the transmission power of the CQI channel to maintain the SNR received from the CQI channel at, or near, a desired SNR. For the internal loop 410, a SNR estimator 420 at the base station 110x estimates the SNR received from the CQI channel and provides the received SNR to a PC bit generator 422. The PC bit generator 422 also receives the desired SNR for the CQI channel, compares the received SNR with the desired SNR, and generates PC bits based on the results of the comparison. Each PC bit can be either (1) an UP command to direct an increase in the transmission power of the CQI channel, or (2) a DOWN command to direct a reduction in transmission power. The 110x base station transmits the PC bits over the direct link (cloud 452) to the 120x terminal.
At terminal 120x, a 460-bit PC processor receives the PC bits sent by the 110x base station and makes a decision for each received PC bit. A PC decision can be an UP decision if the received PC bit is considered as an UP command, or a DOWN decision if the received PC bit is considered a DOWN command. A unit 462 can adjust the transmission power of the CQI channel based on PC decisions from the 460 processor, as follows:
for a decision UP, Ec. (3) for a decision DOWN,
where
PCQI (n) is the transmission power of the CQI channel in the update interval n, and
! PCQI is a step size for the transmission power of the CQI channel.
The transmission power PCQI (n) and the size! PCQI step are given in units of decibels (dB). In the embodiment shown in equation (3), the transmission power is increased or reduced by the same step size, e.g. For example, 0.5 dB, 1.0 dB or some other value, which can be selected to provide good performance for the CQI channel. In another embodiment, the transmission power is adjusted with different step sizes up and down. The PCQI (n) transmission power can also be maintained at the same level if it is estimated that a received PC bit is too unreliable. A transmission data processor (modulator) 464 (TX) generates CQI code words and transmits these code words with a transmission power of PCQI (n) through the CQI channel, via the reverse link (cloud 450), to the station 110x base
External loop 412 adjusts the desired SNR based on received code words, so that the desired erase rate for the CQI channel is obtained. At base station 110x, a metric calculation unit 424 calculates the metric M (n) for each code word received by the CQI channel, p. eg, as shown in equation (1). An erasure detector 426 performs the erasure detection for each received code word, based on the metric M (n) and the erasure threshold, p. eg, as shown in equation (2). A desired SNR setting unit 428 obtains the status of each received code word (either deleted or not deleted) and can set the desired SNR of the CQI channel, as follows:
SNR desired (k) +! SNRarriba, for a deleted code word,
SNR desired (k) -! SNR below, for a code word not deleted, Eq. (4) SNR desired (k + 1) =
where
! SNR desired (k) is the desired SNR of the CQI channel in the update interval k,
! SNRarriba is a step-up size for the desired SNR, and
! SNR Down is a step-down size for the desired SNR.
The desired SNR and step sizes up and down are given in units of dB.
The step sizes! SNRarriba and! SNRabajo can be set as follows:
__1 - Prborrado__
! SNRarriba =! SNRabajo. Prborrado, Ec. (5)
where Prorrado is the desired erase rate. For example, if the desired erase rate for the CQI channel is 10%, then the step size up is 9 times the size of the step down. If the size of the step up is 0.5 dB, then the size of the step down is approximately 0.056 dB.
In one embodiment, the erase threshold is adjusted to achieve a desired Conditional Error Prerror rate for the CQI channel. The conditional error rate is the probability of code words conditioned by errors or not deleted, which means the following: since a received code word is declared a code word not deleted, the probability that the received code word is decoded with errors It’s Prerror. A low Prerror (p. 1% or 0.1%) corresponds to a high degree of confidence in the result of decoding when a code word is not deleted.
The third loop 414 adjusts the deletion threshold based on known code words received, so that the desired conditional error rate is reached for the CQI channel. The 120x terminal can transmit a code word known by the CQI channel periodically, or whenever it is indicated. At the base station 110x, the metric calculation unit 424 and the erase detector 426 perform deletion detection for each known code word received, in the same manner as for other code words received. The erase detector 426 provides the status of each known code word received. A decoder 430 decodes each received code word received, estimated as not deleted, and provides the status of the code word, which can be: (1) deleted, (2) "good" if the received known code word is not deleted and is decoded correctly, or (3) "bad" if the known code word received is not deleted but is decoded with errors. An erase threshold adjustment unit 432 may adjust the erase threshold based on the status of known received code words, according to the following:
THborrado (l) +! THarriba, for a good code word,
THborrado (l + 1) = THborrado (l) -! TH below, for a bad code word, and Eq. (6)
TH deleted (l), for a deleted code word,
where
! TH deleted (l) is the delete threshold for the CQI channel in the update interval l;
! THarriba is a step-up size for the erase threshold; and
! TH below is a step-down size for the erase threshold.
In the embodiment shown in equation (6), the deletion threshold is reduced by! TH below for each known code word received that is "bad." The lower deletion threshold corresponds to a more stringent deletion detection criteria and results in a more likely that a received code word is considered deleted, which, in turn, results in the code word being more likely received is decoded correctly when it is considered as not deleted. The deletion threshold is increased by! THarriba for each received known code word that is "good" and is maintained for the received known code words that are deleted.
The step sizes! THarriba and! THabajo can be determined according to the following:
Ec. (7)
.
! Down =! THarriba.
For example, if the desired conditional error rate for the control channel is 1%, then the size of the step down is 99 times the size of the step up. The magnitude of! THarriba and! THabajo can be selected based on the desired convergence rate for the third loop and / or other factors.
The deletion rate, the conditional error rate, the deletion threshold and the SNR received are usually interrelated. For a given erase threshold and a given SNR received, there is a specific erase rate and a specific conditional error rate. By changing the erase threshold by the third loop 414, a balance can be achieved between the erase rate and the conditional error rate.
In general, the erase threshold setting depends on the metric used for deletion detection. The equations
(6) and (7) are based on the metric shown in equation (2). Other metrics can also be used for deletion detection, and the erase threshold setting can be modified accordingly.
The erase threshold can be adjusted in various ways. In one embodiment, base station 110x maintains a third separate loop for each terminal and adjusts the erase threshold to achieve the desired performance for that terminal. In another embodiment, the base station 110x maintains a single third loop for all terminals and adjusts the deletion threshold based on known code words, received from these terminals, to achieve good performance for all terminals. In yet another embodiment, the base station 110x maintains a single third loop for each group of terminals with similar performance and adjusts the deletion threshold based on known code words received from all terminals in the group.
The internal loop 410, the external loop 412 and the third loop 414 can operate at different speeds. The internal loop 410 is usually the fastest loop, and the transmission power of the CQI channel can be updated whenever the SNR received from the CQI channel is available. External loop 412 is the next fastest loop, and the desired SNR can be updated whenever a code word is received by the CQI channel. The third loop 414 is the slowest loop, and the deletion threshold can be selected whenever a code word known to the CQI channel is received. Update rates for the three loops can be selected to achieve the desired performance for the CQI channel.
FIG. 5 shows an embodiment of a power control mechanism 500 that implements the erased PC scheme for the CQI channel. The power control mechanism 500 includes a first loop 510 and a second loop 512.
The first loop 510 adjusts the transmission power of the CQI channel to achieve the desired erase rate for the CQI channel. For the first loop 510, the metric calculation unit 424 calculates the metric M (n) for each code word received by the CQI channel. The deletion detector 426 performs the deletion detection for each received code word, based on the metric M (n) and the deletion threshold, and generates a CEI bit based on the result of the deletion detection. The CEI bit indicates whether the received code word is deleted or not deleted. The base station 110x transmits the CEI bits over the direct link to the 120x terminal.
At terminal 120x, a CEI bit processor 466 receives the CEI bits sent by the base station 110x and makes a decision as to whether it is deleted or not deleted for each bit of CEI received. A unit 468 can adjust the transmission power of the CQI channel based on the CEI decisions of the 466 processor, as follows:
PCQI (n) +! PCQI, above for a deletion decision,
PCQI (n + 1) = PCQI (n) -! PCQI, below for a decision not to be deleted, Eq. (8)
where! PCQI, above is a step-up size for a deletion decision, and! PCQI, below is a step-down size for a non-deletion decision. The step up and down sizes can be determined based on the desired erase rate, as
following:
1 - Prborrado_
! PCQI, above =! PCQI, below
Ec. (9)
Protruding
The 110x base station may broadcast the step size up and / or down to the terminals within its coverage area. In a given deployment, the desired erase rate may change very slowly. In this way, the overload of spreading the step size up and / or down can be a small percentage of the total overload.
The second loop 512 adjusts the deletion threshold based on known code words received, so that the desired conditional error rate is achieved for the CQI channel. The second loop 512 functions as described above for the third loop 414 in FIG. Four.
The first loop 510 and the second loop 512 can operate at different speeds. The first loop 510 can be updated whenever a code word is received by the CQI channel. The second loop 512 can be updated whenever a code word known to the CQI channel is received.
In the embodiments shown in FIGS. 4 and 5, the benefits of the CQI channel are quantified by a desired erase rate and a desired conditional error rate. Benefits can also be quantified by other measures. The power control mechanisms can be modified accordingly, based on the measures used to quantify the performance.
two. Power control for the ACK channel
In one embodiment, the ACK channel is transmitted at a fixed power, offset with respect to the transmission power of the CQI channel. The offset of the fixed power can be selected to provide good performance for all terminals in a sector and for various operating scenarios (eg, vehicular, pedestrian, etc.).
In another embodiment, the ACK channel for each terminal is transmitted with an adjustable power, offset with respect to the transmission power of the CQI channel for that terminal. The power offset can be adjusted in various ways, e.g. eg, with a closed loop. The power offset can be increased by an upward step size if there is an ACK error, and can be reduced by a downward step size if there is no ACK error.
For the H-ARQ transmission scheme shown in FIG. 3, a base station transmits another block of data for a current packet, after receiving a NAK (or no ACK) and transmits a new packet after receiving an ACK. If a terminal transmits an ACK but the base station detects an ACK with errors, then the base station would transmit another block of data for the current packet. The terminal may therefore be able to deduce that an ACK error has occurred if the terminal transmits an ACK but receives another block of data for the current packet. Therefore, a separate feedback channel through the direct link is not necessary to carry ACK errors, since these errors can be implicitly deduced by the terminal.
FIG. 6 shows an embodiment of a power control mechanism 600 that can be used for the ACK channel. The power control mechanism 600 includes a reference loop 610 and a power offset loop 612. The reference loop 610 provides a reference transmission power level. The reference loop 610 may be the internal loop 410 in FIG. 4, the first loop 510 in FIG. 5 or some other loop that works based on a designated channel. In the embodiment shown in FIG. 6, the reference loop 610 is implemented with the internal loop 410, and the transmission power of the CQI channel is used as the reference transmission power level. Reference loop 610 includes units 420, 422, 460, 462 and 464, which function as described above for FIG. Four.
The power offset loop 612 adjusts the power offset for the ACK channel. For the power offset loop 612, an ACK detector 440 at the 110x base station detects the ACKs sent by the 120x terminal and provides the detected ACKs. For each potential ACK transmission, the ACK detector 440 can determine the ACK channel energy, compare the energy with a threshold and declare a detected ACK if the energy is above the threshold. A TX data processor / modulator 442 receives data packets for the 120x terminal and processes each data packet to generate data blocks. Unit 442 also receives the ACKs detected from the detector 440, transmits a data block for a new packet if an ACK is detected, and transmits another block of data for a current packet if an ACK is not detected.
At terminal 120x, a demodulator / receiver data processor 470 (Demod / RX) receives block transmissions from the base station 110x and attempts to demodulate and decode each received data block. The 470 processor can first perform the decoding, under the assumption that the ACK (if any) sent by the 120x terminal was correctly detected. If there is a decoding error, then the processor 470 can then perform the decoding, under the assumption that the ACK (if any) sent by the 120x terminal was not detected. He
Processor 470 determines whether or not an ACK error has occurred, based on your knowledge of the transmitted ACK (if any) and the decoding results for the received data block.
A unit 472 can adjust the power offset for the ACK channel based on the ACK errors detected from the 470 processor, as follows:
! PACK (n) +! PACK, above for an ACK error,
! PACK (n + 1) = PCQI (n) -! PACK, below for no ACK errors, Ec. (10)
where
! PACK (n) is a power offset for the ACK channel in the update interval n,
! PACK, above is a step-up size for the power offset, and
! PACK, below is a step-down size for the power offset.
The offset! PACK (n) of power and the sizes! PACK, up and! PACK, down step up and down are given in units of dB. Up and down step sizes can be set to achieve the desired ACK error rate, e.g. eg, as shown in equation (9). In one embodiment, the step sizes up and down are set for all data blocks of a given package. In another embodiment, the step up size and /
or down can depend on the number of blocks of data sent for a given packet, and / or other factors.
A calculating unit 474 calculates the transmission power of the ACK channel based on the transmission power of the CQI channel and the power offset, according to the following:
PACK (n) = PCQI (n) +! PACK (n), Ec. (11)
where PACK (n) is the transmission power of the ACK channel in the update interval n.
For each data block received, the TX data processor / modulator 464 generates an ACK if the packet is properly decoded by the 470 processor and transmits the ACK to the transmit power of PACK (n) through the ACK channel.
3. Power control for OFDMA data channels
Data channels can be sent using OFDMA and can be orthogonal to each other in time and frequency. Therefore, in theory, multiple terminals can simultaneously transmit over the data channels to a base station without interfering with each other. However, full orthogonality between data transmissions from different terminals is often not performed, due to channel conditions, receiver imperfections, etc. The loss of orthogonality results in each terminal causing certain magnitudes of interference to other terminals in communication with the same base station. Intra-sector interference is usually not significant for OFDMA.
Data transmissions from terminals in communication with different base stations are usually not orthogonal to each other. Thus, each terminal may cause interference to other terminals in communication with nearby base stations. The performance of each terminal is degraded by interference from all other terminals in the system. The magnitude of the intersectoral interference caused by a given terminal is determined by the magnitude of the transmission power used by that terminal and the location of the terminal with respect to neighboring base stations. The intersectoral interference may be small if the terminal is located near its serving base station and may be large if the terminal is located at the edge of the coverage.
For data channels, the power control can be carried out in such a way that each terminal is allowed to transmit at a power level that is as high as possible, while maintaining intrasectoral and intersectoral interference within acceptable levels. A terminal located closer to its server base station may be authorized to transmit at a higher power level, since this terminal will probably cause less interference to neighboring base stations. On the contrary, a terminal located further from its server base station, and near the edge of the coverage, may be authorized to transmit at a lower power level, since this terminal may cause more interference to neighboring base stations. The control of the transmission power in this way can reduce, in power, the total interference observed by each base station, while allowing the "qualified" terminals to achieve higher SNR values and, therefore, higher data rates. The power control for the data channels can be carried out in various ways to achieve the objectives indicated above.
In one embodiment, the transmission power of a data channel for a terminal is set to achieve a specific transmitter PSD, which can be expressed as:
PSDDCH (n) = PSDREF (n) +! PSD (n), Ec. (12)
where
PSDDCH (n) is the transmission channel PSD in the update interval n,
PSDREF (n) is a reference PSD level in the update interval n, and
! PSD (n) is a delta of transmission PSD for the data channel in the update interval n.
The PSDDCH (n) and PSDREF (n) levels of PSD are given in units of decibels / Hertz (dB / Hz) and the delta! PSD (n) of PSD is given in units of dB.
The reference PSD level is a transmission PSD level that reaches a desired SNR for a designated transmission. In one embodiment, the designated transmission is the CQI channel. If the reference PSD level can reach the desired SNR, then the SNR received from the data channel can be expressed as:
SNRDCH (n) = SNR desired +! PSD (n), Ec. (13)
where SNRDCH (n) is the SNR received from the data channel in the update interval n.
Equation (13) assumes that the data channel and the CQI channel have similar interference statistics. This is the case, p. For example, if CQI and data channels in different sectors can interfere with each other. Otherwise, an interference gap between the CQI channel and the data channel can be determined (e.g., by the base station, and broadcast to the terminals) and can be taken into account in equation (12) .
The transmission PSD of the data channel can be set based on various factors, such as (1) the amount of intersectoral interference that the terminal could cause to other terminals in neighboring sectors, (2) the amount of intrasectoral interference that the terminal it could cause other terminals in the same sector, (3) the maximum power level allowed for the terminal and, (4) possibly other factors.
The magnitude of intersectoral interference that a terminal could cause can be determined in various ways. In one embodiment, the magnitude of intersectoral interference caused by the terminal can be estimated by each neighboring base station, and sent to the terminal, which can then adjust its transmission power accordingly. This individualized interference report may require an exhaustive overload signaling. In another embodiment, the magnitude of intersectoral interference that the terminal could cause can be roughly estimated based on (1) the total interference observed by each neighboring base station, (2) the channel gains for the serving and neighboring base stations, and (3) the level of transmission power used by the terminal. This embodiment is described below.
Each base station can estimate the total, or average, magnitude of interference observed by that base station. The interference can be quantified by an interference-over-thermal (IOT) value, or with some other amount. IOT is a ratio between the total interference power observed by the base station and the thermal noise power. In one embodiment, the base station generates an interference value or report from other sectors (OSI), according to the following:
'2' if IOTmed, m (n)> IOTalta, '1' if IOTalta> IOTmed, m (n)> IOT desired, Ec. (14)
OSIm (n) = '0' if IOT desired> IOTmed, m (n)
where IOTmed, m (n) is a measured IOT for sector m in the update interval n, Desired IOT is a desired operating point for the system, IOTalta is a high threshold for intersectoral interference, and OSIm (n) is the OSI value for sector m in the update interval n. In the embodiment shown in equation (14), the OSI value is set to '0' to indicate low interference
intersectorial, '1' to indicate high intersectoral interference and '2' to indicate excessive intersectoral interference. The OSI value can also be set in other ways. The base station can spread the value of OSI to terminals in other sectors.
A terminal may estimate the channel gain (or path loss) for each base station that may receive the reverse link transmission from the terminal. The channel gain for each base station can be estimated based on the pilot signal received from the base station. A channel gain ratio can be calculated for each neighboring base station, as follows:
Eq. (15) where gs (n) is the channel gain for the server base station, gm (n) is the channel gain for the neighboring base station m, and rm (n) is the channel gain ratio for the neighboring base station m. The channel gain ratio for each neighboring base station can be considered as a relative distance that
indicates the distance to that neighboring base station with respect to the distance to the serving base station. In general, the channel gain ratio for a neighboring base station increases as the terminal approaches the serving base station and decreases as the terminal approaches the edge of coverage.
A terminal can monitor the OSI values broadcast by neighboring base stations. In one embodiment, the terminal considers only the OSI value of the most powerful neighboring base station, which has the smallest channel gain ratio. The terminal can adjust its transmission PSD delta according to the following:
! PSD (n) -∀down, if the OSI value = '1' or '2',! PSD (n + 1) =! PSD (n) + ∀up, if the OSI value = '0' Ec . (16)
where
Ibaup is a step-up size for the delta of the transmission PSD, and
∀ below is a step-down size for the delta of the transmission PSD.
In equation (16), if the OSI value of the most powerful neighboring base station is set to '1' or '2', because that base station registers an intersectoral interference greater than the nominal one, then the PSD delta Transmission can be adjusted down. On the contrary, if the OSI value is set to '0', then the transmission PSD delta can be adjusted upwards. Up and down determine the magnitude of the adjustment for the transmission PSD delta. In one embodiment, "up" and "down" are fixed values. In another embodiment, "up" and "down" are variable values that may depend on the current level of transmission power, or the current transmission PSD delta for the terminal, the channel gain ratio for the more powerful neighboring base station and / or other factors.
In other embodiments, the terminal may consider the OSI values of multiple neighboring base stations. In any case, the OSI values from the neighboring base stations determine the direction in which to adjust the transmission PSD delta.
A specific embodiment to maintain intersectoral interference within acceptable levels has been described in the foregoing. Intersectoral interference can also be maintained within acceptable levels based on other parameters and / or in other ways.
Although the data channels for each sector are designated to be orthogonal to each other, some loss of orthogonality may be the result of carrier interference (ICI), inter-symbol interference (ISI), etc. This loss of orthogonality causes intrasectoral interference. To mitigate intrasectoral interference, the transmission PSD of each terminal can be controlled so that the extent of intrasectoral interference that the terminal may cause to other terminals in the same sector is maintained within acceptable levels. In one embodiment, acceptable intrasectoral interference is achieved by restricting the transmission PSD delta so that it is within a predetermined range, as follows:
! PSD (n) # [! PSDmax,! PSDmin], Ec. (17)
where! PSDmax is the maximum transmission PSD delta and! PSDmin is the minimum transmission PSD delta acceptable for the data channel.
FIG. 7 shows an embodiment of a power control mechanism 700 that can be used for the data channel. Terminal 120x communicates with server base station 110x and may cause interference to neighboring base stations 110a at 110m. The power control mechanism 700 includes (1) a reference loop 710 operating between terminal 120x and server base station 110x, and (2) an external data loop 712 operating between terminal 120x and neighboring base stations 110a to 110m. The reference loop 710 and the external data loop 712 can operate simultaneously, but can be updated at different speeds, e.g. For example, the reference loop 710 may be updated more frequently than the external data loop 712. For simplicity, FIG. 7 shows only the part of loops 710 and 712 that resides in terminal 120x.
Reference loop 710 provides the level of reference PSD in equation (12). The reference loop 710 may be the internal loop 410 in FIG. 4, the first loop 510 in FIG. 5 or some other loop that works based on a designated channel. In the embodiment shown in FIG. 7, the reference loop 710 is implemented with the internal loop 410, and the transmission PSD of the CQI channel is used as the reference PSD level.
The external data loop 712 adjusts the transmission PSD of the data channel to be as high as possible, while maintaining intrasectoral and intersectoral interference within acceptable levels. For the external data loop 712, each neighboring base station 110 receives transmissions on the reverse link, estimates the intersectoral interference recorded by that base station from the terminals in other sectors, generates an OSI value based on the interference estimate, e.g. eg, as shown in equation (14), and disseminates the value of OSI to terminals in the other sectors.
At terminal 120x, an OSI processor 480 receives the OSI values broadcast by the neighboring base stations and provides the detected OSI values to a unit 484 for calculating the transmission PSD deltas. A channel estimator 482 receives pilot signals from the serving and neighboring base stations, estimates the channel gain for each base station and provides the estimated channel gains for all base stations to unit 484. Unit 484 determines the channel gain ratios for neighboring base stations and further adjusts the transmission PSD delta based on the detected OSI values, the channel gain ratios and the maximum and minimum transmission PSD deltas, as described above.
A calculation unit 486 can determine the reference PSD level based on the transmission power of the CQI channel, according to the following:
Ec. (18)
where NCQI is the number of subcarriers used for the CDMA control segment over which the CQI channel is sent. Unit 486 then calculates the transmission PSD of the data channel based on the reference PSD level and the transmission PSD delta, p. eg, as shown in equation (12). Unit 486 can then calculate the transmission power of the data channel based on the transmission PSD, according to the following:
PDCH (n) = PSDDCH (n). NDCH, Ec. (19)
where
NDCH is the number of subcarriers used for the data channel, and
PDCH (n) is the transmission power of the data channel in the update interval n.
The TX data processor / modulator 464 uses the PDCH transmission power (n) for the transmission of data to the 110x server base station.
The 120x terminal can send various types of feedback information to the 110x server base station. For example, terminal 120x can send the transmission PSD delta, the maximum number of subcarriers that the terminal can support in the current transmission PSD delta, the desired quality of service (QoS), the size of the temporary store, etc. . The 120x terminal can send the feedback information (e.g. e.g., the transmission PSD delta and / or the maximum number of subcarriers with support) every few update intervals, to reduce the magnitude of the signaling, and can also send the information by signaling in the band through the data channel . If the 120x terminal has a low delta of transmission PSD, then the terminal can be assigned more
subcarriers in order to use more than, or all, of the available transmission power.
Four. System stability
For CDMA control channels on the reverse link, the CDMA transmission from each terminal acts as interference for the CDMA transmissions from other terminals on a base station. The power control techniques described herein adjust the transmission power of each terminal to achieve the desired level of performance, while minimizing interference to other terminals. The capacity and stability of the CDMA control channels can be quantified for an increase-over-thermal (RoT) ratio, which is the ratio between the total power received at the base station and the thermal noise power. In general, capacity increases for older RoTs. However, capacity gains are minimal above a specific RoT value.
A terminal usually has a maximum transmitting power Pmax given, which can be specified by regulatory requirements. The terminal usually transmits at a higher power level for greater path loss, as well as greater RoT, in order to achieve the desired SNR. If the path loss is too large and / or the RoT is too high, then the terminal may not be able to reach the desired SNR with maximum transmission power.
A base station can limit the RoT to ensure that terminals with high path loss are not temporarily suspended, and to ensure system stability. The base station can estimate its RoT and compare the estimated RoT with a threshold. If the estimated RoT exceeds the threshold, then the base station may take corrective actions to decrease the RoT. Corrective actions may include the following:
<dl><dt>* </dt><dd>Deny new users access to the system, </dd></dl>
<dl><dt>* </dt><dd>Unassign some users who have already been granted access to the system, </dd></dl>
<dl><dt>* </dt><dd>Increase the desired erase / error rate, and </dd></dl>
<dl><dt>* </dt><dd>Allocate additional resources for control channels. </dd></dl>
The base station may also take other corrective actions, in addition to those listed above.
For OFDMA data channels on the reverse link, intrasectoral interference is minimal, and the capacity and stability of a base station are determined by the IOT. Thus, for OFDMA data channels, the IOT, before the RoT, can be controlled.
The IOT can be reduced if it becomes excessive, in order to avoid temporary suspension for disadvantaged users. A base station that experiences excessive IOT can diffuse an OSI value of '2' through the air. Users who can receive this OSI value can reduce their transmission PSD deltas more quickly and / or in greater steps. For network-based interference control, a base station that experiences excessive IOT can report its IOT to neighboring base stations. The intersectoral OSI report may be the same as the OSI report over the air, or it may be more comprehensive. A base station can also report its RoT and / or other information to neighboring base stations. Neighboring base stations can regulate data transmissions by controlling the admission of new users to their sectors, deallocating users that have already been admitted, planning users in their sectors in a way that reduces interference to neighboring base stations, assigning users in its sectors to data channels that cause less interference to neighboring base stations, adjusting the transmission power of users, and / or perform other actions to mitigate degradation for the base station experiencing excessive IOT or RoT. For example, the other base stations can reduce the transmission power of the users in their sectors whenever an excessive IOT or RoT is reported by another base station.
A power control scheme can also control all terminals for a desired value of given RpoT. However, this power control scheme would ignore the fact that terminals in different locations cause different magnitudes of intersectoral interference, and ignoring this fact may reduce system capacity. In addition, an equal degree of service flow can be achieved in the system by the power control scheme of the same RpoT, while a proportionally equitable flow can also be achieved by the delta-based power control scheme, shown in the FIG. 7.
The base stations can be synchronized and can transmit their CDMA control segments in the same time and frequency region. In this case, the CDMA control channels for each sector can be orthogonal to OFDMA data channels in neighboring sectors. Therefore, RoT-based control of CDMA control channels may not affect IOT-based control of OFDMA data channels, and vice versa.
Base stations may be out of sync and can transmit their CDMA control segments in different regions of time and frequency. In this case, the CDMA control channels for each sector can
experiencing greater interference from OFDMA data channels in neighboring sectors, and the performance of control channels may be degraded. This degradation can be mitigated if the desired interference level in the data channels is set close to the desired interference level of the control channels. However, this restriction may reduce the capacity of data channels. Data capacity can be improved if degradation in control channels, due to intersectoral interference from data channels, can be tolerated or mitigated, e.g. eg, increasing the dimension of the CDMA control segment.
5. System
FIG. 8 shows an embodiment of a process 800 for performing power control in a system that uses multiple radio technologies. The process 800 can be carried out by a terminal. A reference channel is sent using a first radio technology, e.g. eg, CDMA (block 812). A second channel is sent using a second radio technology, e.g. eg, OFDMA (block 814). The reference channel may be a control channel that carries signaling, e.g. eg, CQI information. The second channel may be a data channel that carries traffic data. The transmission power of the reference channel is adjusted to achieve a desired level of performance for the reference channel (block 816). The transmission power of the second channel is adjusted based on the transmission power of the reference channel (block 818).
The transmission power of the reference channel can be adjusted based on PC commands, which can be generated to achieve a desired quality of signal received for the reference channel at a receiving base station. The transmission power of the reference channel can also be adjusted based on erase indications for code words sent by the reference channel. The desired level of performance for the reference channel can be quantified by a desired erase rate and / or some other measure. The desired quality of the received signal can be adjusted to achieve the desired erase rate. The step sizes up or down for the transmission power of the reference channel can also be set to achieve the desired erase rate.
A transmission power delta, or a transmission PSD delta for the second channel, can be adjusted, e.g. eg, based on interference estimates. The transmission power of the second channel can then be determined based on the transmission power of the reference channel and the transmission power delta or the transmission PSD delta.
FIG. 9 shows an embodiment of an apparatus 900 for performing power control in a system that uses multiple radio technologies. The apparatus 900 includes one or more processors to send a reference channel using a first radio technology, e.g. eg, CDMA (block 912), one or more processors to send a second channel using a second radio technology, e.g. eg, OFDMA (block 914), one or more processors to adjust the transmission power of the reference channel, in order to achieve a desired level of performance for the reference channel (block 916), and one or more processors to adjust the transmission power of the second channel based on the transmission power of the reference channel (block 918).
FIG. 10 shows an embodiment of a process 1000 for performing power control for a control channel, e.g. eg, an ACK channel. A reference transmission power level is determined (block 1012). The reference transmission power level may be the transmission power of a reference channel, which may be controlled in terms of power, to achieve a desired level of performance for the reference channel. Errors in signaling sent by a control channel are detected, e.g. e.g., implicitly, without receiving feedback indicating errors (block 1014). The signaling can be ACKs, and ACK errors sent by the control channel can be detected based on the data packets received by a data channel. The transmission power of the control channel is adjusted based on the reference transmission power level and the errors detected in the control channel (block 1016).
FIG. 11 shows an embodiment of an apparatus 1100 for performing power control for a control channel, e.g. eg, an ACK channel. The apparatus 1100 includes one or more processors to determine a reference transmission power level (block 1112), one or more processors to detect errors in signaling sent by a control channel, e.g. e.g., implicitly, without receiving feedback indicating errors (block 1114), and one or more processors to adjust the transmission power of the control channel based on the reference transmission power level and the errors detected in the channel control (block 1116).
FIG. 12 shows an embodiment of a process 1200 for performing power control for a data channel. A reference PSD level is determined, e.g. eg, based on the transmission power of a reference channel, which can be controlled for power, to achieve a desired level of performance for the reference channel (block 1212). A delta of transmission PSD is adjusted, e.g. eg, based on interference estimates (block 1214). A data channel transmission PSD is determined based on the reference PSD level and the transmission PSD delta (block 1216). The transmission power of the data channel can then be determined in
based on the transmission PSD and the number of subcarriers used for the data channel (block 1218). The reference channel can be sent using CDMA, and the data channel can be sent using OFDMA. Reference and data channels can also be sent using other radio technologies.
For block 1214, interference reports can be received from base stations. Channel gains for base stations can be estimated, e.g. eg, based on pilot signals received from the base stations. The transmission PSD delta can then be adjusted based on the estimated channel gains for the base stations and the interference reports received from the base station. For example, the transmission PSD delta can be reduced if at least one (eg, the most powerful) neighboring base station indicates high interference, and can be increased if said at least one base station does not indicate high interference. The transmission PSD delta may be limited to be within a range of values determined by the maximum and minimum PSD deltas supported for the data channel.
FIG. 13 shows an embodiment of an apparatus 1300 for performing power control for a data channel. The apparatus 1300 includes one or more processors to determine a reference PSD level, e.g. e.g., based on the transmission power of a reference channel (block 1312), one or more processors to adjust a transmission PSD delta, e.g. e.g., based on interference estimates (block 1314), one or more processors to determine a transmission PSD of the data channel, based on the reference PSD level and the transmission PSD delta (block 1316), and one or more processors to determine the transmission power of the data channel based on the transmission PSD and the number of subcarriers used for the data channel (block 1318).
FIG. 14 shows a block diagram of an embodiment of terminal 120x, server base station 110x and neighboring base station 110m in system 100. For clarity, the following description assumes the use of control mechanisms 400, 600 and 700 power in FIGS. 4, 6 and 7, respectively.
At the 110x server base station, a 1414x TX data processor receives traffic data from a 1412x data source, and signaling from a 1430x controller / processor and a 1434x scheduler. For example, the 1430x controller / processor can provide PC commands to adjust the transmission power of the terminals in communication with the 120x base station, and the 1434x scheduler can provide assignments of data channels and /
or subcarriers for terminals. The 1414x TX data processor processes (e.g., encodes, interleaves and correlates with symbols) traffic data and signaling, and provides symbols. A modulator (Mod) 1416x performs OFDM modulation for data channels sent using OFDMA, performs CDMA modulation for control channels sent using CDMA and provides a sequence of complex value segments. A transmitter (TMTR) 1418x conditions (p. For example, it converts the sequence of segments to analogue, amplifies, filters and increases the frequency and generates a direct link signal, which is transmitted through a 1420x antenna.
The neighboring base station 110m similarly processes traffic data and signaling for the terminals served by that base station. The 110m base station also sends OSI reports indicating the magnitude of interference recorded by the base station. Traffic data and signaling are processed by a 1414m TX data processor, modulated by a 1416m modulator, conditioned by a 1418m transmitter and transmitted by a 1420m antenna.
At terminal 120x, an antenna 1452 receives the direct link signals from the base stations 110x and 110m, and possibly other base stations. A receiver (RCVR) 1454 conditions (e.g., filters, amplifies, reduces the frequency and digitizes) a signal received from the antenna 1452, and provides samples. A demodulator (Demod) 1456 performs OFDM demodulation for the data channel, performs CDMA demodulation for control channels and provides symbol estimates. An RX data processor 1458 processes (e.g., decorates symbols, deinterleaves and decodes) symbol estimates, provides decoded data to a data sink 1460 and provides the detected signaling (e.g., PC commands, OSI reports, etc.) to a 1470 controller / processor.
On the reverse link, a TX data processor 1482 receives and processes traffic data from a data source 1480, and signaling (eg, ACK, CQI code words) from the controller / processor 1470. A modulator 1484 performs OFDM modulation for a data channel sent using OFDMA, performs CDMA modulation for control channels sent using CDMA and provides a sequence of segments. A transmitter 1486 conditions the sequence of segments and generates a reverse link signal, which is transmitted from the antenna 1452.
At the 110x server base station, the reverse link signals from the 120x terminal, and other terminals, are received by the 1420x antenna, conditioned by a 1440x receiver, demodulated by a 1442x demodulator and processed by a 1444x RX data processor. The 1444x processor provides decoded data to a 1446x data sink, and the signaling detected, to the 1430x controller / processor. The 1440x receiver can estimate the signal quality received from a reference channel (e.g., the CQI channel) for each terminal, and can provide this information to the 1430x controller / processor. The 1430x controller / processor can obtain PC commands and / or instructions
Deleted for each terminal, as described above.
The 1430x, 1430m and 1470 controllers / processors direct the operations of various processing units at the 110x and 110m base stations, and the 120x terminal, respectively. These controllers / processors can also perform various functions for power control. For example, the 1430x controller / processor may implement some or all of the units 420 to 442 shown in FIGS. 4 to 7 for the 110x base station. Controller 1470 may implement some or all of the units 460 to 486 shown in FIGS. 4 to 7 for the 120x terminal. The 1470 controller can also implement the 800, 1000 and / or 1200 processes shown in FIGS. 8, 10 and 12, respectively. Memories 1432x, 1432m and 1472 store data and program codes for base stations 110x and 110m, and terminal 120x, respectively. The 1434x scheduler plans terminals in communication with the 110x base station and assigns data channels and / or subcarriers to the planned terminals.
The power control techniques described herein can be implemented by various means. For example, these techniques can be implemented in hardware, firmware, software or a combination thereof. For a hardware implementation, the processing units used to perform the control can be implemented within one or more application-specific integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD) , programmable logic devices (PLD), field programmable gate formations (FPGA), processors, controllers, microcontrollers, microprocessors, electronic devices, other electronic units designed to perform the functions described herein, or a combination thereof.
For a firmware and / or software implementation, power control techniques can be implemented with instructions (e.g., procedures, functions, etc.) that can be used by one or more processors to perform the functions described in the present memory Firmware and / or software codes can be stored in a memory (e.g., memory 1432x or 1472 in FIG. 14) and executed by a processor (e.g., processor 1430x or 1470). The memory can be implemented within the processor, or be external to the processor.
Headings are included herein for reference and to assist in locating certain sections. These headings are not intended to limit the scope of the concepts described below, and these concepts may be applicable in other sections throughout the entire length of the specification.
The foregoing description of the disclosed embodiments is provided to enable any person skilled in the technology to manufacture or use the present disclosure. Various modifications to these embodiments will be immediately apparent to those skilled in the technology, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein, but must be granted the broadest scope consistent with the novel principles and characteristics disclosed herein.
11 sheets
Sheet 1 Sheet 2 Sheet 3 Sheet 4 Sheet 5 Sheet 6 Sheet 7 Sheet 8 Sheet 9 Sheet 10 Sheet 11
50 members in 13 offices
Priority claims5
| Document | Office | Kind | Date |
|---|---|---|---|
| 710404P | United States of America | – | |
| 71040405 | United States of America | P | |
| 756816P | United States of America | – | |
| 75681606 | United States of America | P | |
| 2006032894 | United States of America | W |
Members50
| Document | Office | Kind | |
|---|---|---|---|
| US2007041429A1 | United States of America | A1 | |
| WO2007024931A2 | World Intellectual Property Organization (WIPO) | A2 | |
| WO2007024931A3 | World Intellectual Property Organization (WIPO) | A3 | |
| TW200729767A | Taiwan Province of China | A | |
| AR055131A1 | Argentina | A1 | |
| KR20080046667A | Republic of Korea | A | |
| EP1932251A2 | European Patent Office (EPO) | A2 | |
| CN101305528A | China | A | |
| JP2009506654A | Japan | A | |
| US2010027451A1 | United States of America | A1 | |
| US2010034315A1 | United States of America | A1 | |
| KR20100087767A | Republic of Korea | A | |
| KR20100089892A | Republic of Korea | A | |
| TW201036356A | Taiwan Province of China | A | |
| US7965789B2 | United States of America | B2 | |
| JP2011244443A | Japan | A | |
| JP2011244444A | Japan | A | |
| KR20120003971A | Republic of Korea | A | |
| CN102325363A | China | A | |
| CN102325364A | China | A | |
| KR101120193B1 | Republic of Korea | B1 | |
| KR101120202B1 | Republic of Korea | B1 | |
| KR101139092B1 | Republic of Korea | B1 | |
| JP2012124919A | Japan | A | |
| TWI369863B | Taiwan Province of China | B | |
| EP2521280A1 | European Patent Office (EPO) | A1 | |
| EP2521281A1 | European Patent Office (EPO) | A1 | |
| EP1932251B1 | European Patent Office (EPO) | B1 | |
| PT1932251E | Portugal | E | |
| ES2398967T3This record | Spain | T3 | |
| DK1932251T3 | Denmark | T3 | |
| PL1932251T3 | Poland | T3 | |
| CN101305528B | China | B | |
| US8520745B2 | United States of America | B2 | |
| JP2013168952A | Japan | A | |
| JP5318905B2 | Japan | B2 | |
| JP2014060730A | Japan | A | |
| US8718181B2 | United States of America | B2 | |
| JP5490831B2 | Japan | B2 | |
| JP5503040B2 | Japan | B2 | |
| TWI456926B | Taiwan Province of China | B | |
| TW201442451A | Taiwan Province of China | A | |
| JP5678158B2 | Japan | B2 | |
| CN102325363B | China | B | |
| CN102325364B | China | B | |
| TWI527396B | Taiwan Province of China | B | |
| EP2521281B1 | European Patent Office (EPO) | B1 | |
| ES2671945T3 | Spain | T3 | |
| EP2521280B1 | European Patent Office (EPO) | B1 | |
| HUE036936T2 | Hungary | T2 |
Numbers
- Publication
- 2398967
- Application
- 6813674
Titles2
- Spanish
- Control de potencia de enlace inverso para un sistema de OFDMA
- English
- Reverse link power control for an OFDMA system
Classification
- CPC, 15
- H04W52/146
- H04W52/241
- H04W52/08
- H04W52/12
- H04W52/16
- H04W52/20
- H04W52/247
- H04W52/248
- H04W52/325
- H04B17/391
- H04L1/18
- H04W52/243
- H04W52/48
- H04W52/54
- H04W88/06
- IPC, 3
- H04B7 005
- H04B1 69
- H04J13 00