Diversity transmission modes for mimo ofdm communication systems
59 claims: 7 independent, 52 dependent
- 1複数の空間時間ダイバーシティ トランスミッション モードの内から1つの空間時間ダイバーシティ トランスミッション モードを選択し、ここで、前記複数のダイバーシティ トランスミッション モードの各々は空間時間送信ダイバーシティを用いて、第1の一対のアンテナを用いる第1の一対の送信記号と第2の一対のアンテナを用いる第2の一対の送信記号とを送信するように用いられ、前記第1の一対のアンテナは前記第2の一対のアンテナと異なっており、 少なくとも1つのデータストリームを符号化し変調して、第1及び第2の対の変調記号を供給し、及び 前記第1の一対のアンテナから送信される前記第1の一対の送信記号を与えるために前記選択された空間時間ダイバーシティ トランスミッション モードに基づいて前記第1の一対の変調記号と、前記第2の一対のアンテナから送信される前記第2の一対の送信記号を与えるために前記選択された空間時間ダイバーシティ モードに基づいて前記第2の一対の変調記号とを処理することを具備する無線通信装置から送信用のデータを処理する方法。
- 2前記第1の一対の変調記号と前記第2の一対の変調記号は異なるサブバンドで送信される請求項1記載の方法。
- 3前記第1の一対の変調記号と前記第2の一対の変調記号の少なくとも1つの記号は同一の変調記号である請求項1記載の方法。
- 4前記複数のダイバーシティ トランスミッション モードは周波数ダイバーシティ トランスミッション モードをさらに含む請求項1記載の方法。
- 5前記複数のダイバーシティ トランスミッション モードはウォルシュダイバーシティ トランスミッション モードをさらに含む請求項1載の方法。
- 6前記少なくとも1つのデータストリームはオーバーヘッドチャネルに対応する請求項1記載の方法。
- 7選択することは前記少なくとも1つのデータストリームの型に基づいて選択することを含む請求項1記載の方法。
- 8選択することは前記第1及び第2の一対の変調記号の1つを受信する端末の型に基づいて選択することを含む請求項1記載の方法。
- 9選択することはアクセスポイントと通信する端末の型の混合に基づいて選択することを含む請求項1記載の方法。
- 10選択することは前記複数のダイバーシティ トランスミッション モードの1つか空間多重化モードのいずれかを選択することを含む請求項1記載の方法。
- 11選択することはチャネル情報に基づいて選択することを含む請求項1記載の方法。
- 12パイロット記号を前記変調記号で多重化することをさらに具備する請求項1記載の方法。
- 13符号化することはターボ符号を用いることを含む請求項1記載の方法。
- 14符号化することは畳み込み符号を用いることを含む請求項1記載の方法。
- 15複数の空間時間ダイバーシティ トランスミッション モードの内から1つの空間時間ダイバーシティ トランスミッション モードを選択するように構成されたコントローラ、ここで、前記複数のダイバーシティ トランスミッション モードの各々は空間時間送信ダイバーシティを用いて、第1の一対のアンテナを用いる第1の一対の送信記号と第2の一対のアンテナを用いる第2の一対の送信記号とを送信するように用いられ、前記第1の一対のアンテナは前記第2の一対のアンテナと異なっている、と、 少なくとも1つのデータストリームを符号化し変調し、第1及び第2の対の変調記号を供給するように構成されたプロセッサと、 前記第1の一対のアンテナから送信される前記第1の一対の送信記号を与えるために前記選択された空間時間ダイバーシティ トランスミッション モードに基づいて前記第1の一対の変調記号と、前記第2の一対のアンテナから送信される前記第2の一対の送信記号を与えるために前記選択された空間時間ダイバーシティ モードに基づいて前記第2の一対の変調記号とを処理するように構成された他のプロセッサと、を具備する無線通信システムにおける装置。
- 16前記第1の一対の変調記号と前記第2の一対の変調記号は異なるサブバンドで送信される請求項15記載の装置。
- 17前記第1の一対の変調記号と前記第2の一対の変調記号の少なくとも1つの記号は同一の変調記号である請求項15記載の装置。
- 18前記複数のダイバーシティ トランスミッション モードは周波数ダイバーシティ トランスミッション モードをさらに含む請求項15記載の装置。
- 19前記複数のダイバーシティ トランスミッション モードはウォルシュダイバーシティ トランスミッション モードをさらに含む請求項15記載の装置。
- 20前記少なくとも1つのデータストリームはオーバーヘッドチャネルに対応する請求項15記載の装置。
- 21前記コントローラは前記少なくとも1つのデータストリームの型に基づいて選択するように構成されている請求項15記載の装置。
- 22前記コントローラは前記第1及び第2の一対の変調記号の1つを受信する端末の型に基づいて選択するように構成されている請求項15記載の装置。
- 23前記コントローラはアクセスポイントと通信する端末の型の混合に基づいて選択するように構成されている請求項15記載の装置。
- 24前記コントローラは前記複数のダイバーシティ トランスミッション モードの1つか空間多重化モードのいずれかを選択するように構成されている請求項15記載の装置。
- 25前記コントローラはチャネル情報に基づいて選択するように構成されている請求項24記載の装置。
- 26複数の空間時間ダイバーシティ トランスミッション モードの内から1つの空間時間ダイバーシティ トランスミッション モードを選択するための手段、ここで、前記複数の空間時間ダイバーシティ トランスミッション モードの各々は空間時間送信ダイバーシティを用いて、第1の一対のアンテナを用いる第1の一対の送信記号と第2の一対のアンテナを用いる第2の一対の送信記号とを送信し、前記第1の一対のアンテナは前記第2の一対のアンテナと異なる、と、 少なくとも1つのデータストリームを符号化し変調し、第1及び第2の一対の変調記号を供給するように構成されたプロセッサと、 前記第1の一対のアンテナから送信される前記第1の一対の送信記号を与えるために前記選択された空間時間ダイバーシティ トランスミッション モードに基づいて前記第1の一対の変調記号と、前記第2の一対のアンテナから送信される前記第2の一対の送信記号を与えるために前記選択された空間時間ダイバーシティ モードに基づいて前記第2の一対の変調記号とを処理するための手段と、を具備する装置。
- 27前記第1の一対の変調記号と前記第2の一対の変調記号は異なるサブバンドで送信される請求項26記載の装置。
- 28前記第1の一対の変調記号と前記第2の一対の変調記号の少なくとも1つの記号は同一の変調記号である請求項26記載の装置。
- 29前記複数のダイバーシティ トランスミッション モードは周波数ダイバーシティ トランスミッション モードをさらに含む請求項26記載の装置。
- 30前記少なくとも1つのデータストリームはオーバーヘッドチャネルに対応する請求項26記載の装置。
- 31前記選択するための手段は少なくとも1つのデータストリームの型に基づいて選択するための手段を含む請求項26記載の装置。
- 32前記選択するための手段は前記第1及び第2の一対の変調記号の1つを受信する端末の型に基づいて選択するための手段を含む請求項26記載の装置。
- 33前記選択するための手段はアクセスポイントと通信する端末の型の混合に基づいて選択するための手段を含む請求項26記載の装置。
- 34前記選択するための手段は前記複数のダイバーシティ トランスミッション モードの1つか空間多重化モードのいずれかを選択するための手段を含む請求項26記載の装置。
- 35前記選択するための手段はチャネル情報に基づいて選択するための手段を含む請求項34記載の装置。
- 36二対の変調記号を供給し、 複数の空間時間ダイバーシティ トランスミッション モードの内から選択された一つの空間時間ダイバーシティ トランスミッション モードにより各対の変調記号を処理して前記二対の変調記号から第1の一対の送信記号と、前記二対の変調記号から第2の一対の送信記号とを供給し、 第1の一対のアンテナを用いて送信用の前記第1の一対の送信記号と、前記第1の一対のアンテナとは異なる第2の一対のアンテナを用いて送信用の前記一対の第2の送信記号とを供給することを具備する無線通信装置から送信するためのデータを処理する方法。
- 37前記第1の一対の送信記号と前記第2の一対の送信記号は異なるサブバンドで送信される請求項36記載の方法。
- 38前記二対の変調記号はオーバーヘッドチャネルに対応する請求項36記載の方法。
- 39前記二対の変調記号を供給することはターボ符号を用いて符号化することを含む請求項36記載の方法。
- 40前記二対の変調記号を供給することは畳み込み符号を用いることを含む請求項36記載の方法。
- 41処理することは前記第1の一対の送信記号を形成するために前記二対の変調記号のうちの第1の一対の変調記号を処理することと、前記第2の一対の送信記号を形成するために前記二対の変調記号のうちの第2の一対の変調記号を処理することとを含む請求項36記載の方法。
- 42前記第1の一対の変調記号と前記第2の一対の変調記号の少なくとも1つの記号は同一の変調記号である請求項41記載の方法。
- 43二対の変調記号を供給するように構成された第1のプロセッサと、 複数の空間時間ダイバーシティ トランスミッション モードの内から選択された一つの空間時間ダイバーシティ トランスミッション モードによって各一対の変調記号を処理して、前記二対の変調記号から第1の一対の送信記号と前記二対の変調記号から第2の一対の送信記号とを供給すると共に、第1の一対のアンテナを用いて送信用の前記第1の一対の送信記号と前記第1の一対のアンテナとは異なる第2の一対のアンテナを用いて送信用の前記第2の一対の送信記号とを供給するように構成された第2のプロセッサと、を具備する無線通信装置。
- 44前記第1の一対の送信記号と前記第2の一対の送信記号を異なるサブバンドで送信するように構成されたコントローラをさらに具備する請求項43記載の装置。
- 45前記二対の変調記号はオーバーヘッドチャネルに対応する請求項43記載の装置。
- 46前記第1のプロセッサはターボ符号を用いて前記二対の変調記号を供給するように構成される請求項43記載の装置。
- 47前記第1のプロセッサは畳み込み符号を用いて前記二対の変調記号を供給するように構成される請求項43記載の装置。
- 48前記第2のプロセッサは前記二対の変調記号の内の第1の一対を処理して前記第1の一対の送信記号を形成し、前記二対の変調記号の内の第2の一対を処理して前記第2の一対の送信記号を形成するように構成される請求項43記載の装置。
- 49前記第1の一対の変調記号と前記第2の一対の変調記号の少なくとも1つの記号は同一の変調記号である請求項48記載の装置。
- 50二対の変調記号を供給するための手段と、 前記二対の変調記号から第1の一対の送信記号と前記二対の変調記号から第2の一対の送信記号を形成するために、複数の空間時間ダイバーシティ トランスミッション モードの内から選択された一つの空間時間ダイバーシティ トランスミッション モードを使用するための手段と、 第1の一対のアンテナを用いて送信するための前記第1の一対の送信記号と前記第1の一対のアンテナとは異なる第2の一対のアンテナを用いて送信するための前記第2の一対の送信記号を供給するための手段と、を具備する無線通信装置から送信用のデータを処理するための装置。
- 51前記第1の一対の送信記号と前記第2の一対の送信記号は異なるサブバンドで送信される請求項50記載の装置。
- 52前記二対の変調記号はオーバーヘッドチャネルに対応する請求項50記載の装置。
- 53前記使用するための手段は、前記二対の変調記号の内の第1の対を処理して前記第1の一対の送信記号と、前記二対の変調記号の内の第2の対を処理して前記第2の一対の送信記号を形成する手段を含む請求項50記載の装置。
- 54前記第1の一対の変調記号と前記第2の一対の変調記号の少なくとも1つの記号は同一の変調記号である請求項53記載の装置。
- 55無線通信装置から送信されるデータを処理するためのコンピュータプログラムプロダクトであって、前記無線装置にはメモリが具備され、このメモリには方法を実施するための一つまたは複数のプロセッサにより実行可能な複数の命令が記憶され、前記方法は、 複数の空間時間ダイバーシティ トランスミッション モードの内から1つの空間時間ダイバーシティ トランスミッション モードを選択し、ここで、前記複数のダイバーシティ トランスミッション モードの各々は空間時間送信ダイバーシティを用いて、第1の一対のアンテナを用いる第1の一対の送信記号と第2の一対のアンテナを用いる第2の一対の送信記号とを送信するように用いられ、前記第1の一対のアンテナは前記第2の一対のアンテナと異なっており、 少なくとも1つのデータストリームを符号化し変調して、第1及び第2の対の変調記号を供給し、 前記第1の一対のアンテナから送信される前記第1の一対の送信記号を与えるために前記選択された空間時間ダイバーシティ トランスミッション モードに基づいて前記第1の一対の変調記号と、前記第2の一対のアンテナから送信される前記第2の一対の送信記号を与えるために前記選択された空間時間ダイバーシティ モードに基づいて前記第2の一対の変調記号とを処理することを具備する、コンピュータプログラムプロダクト。
- 56前記第1の一対の送信記号と前記第2の一対の送信記号は異なるサブバンドで送信される請求項55記載のコンピュータプログラムプロダクト。
- 57前記複数のダイバーシティ トランスミッション モードは周波数ダイバーシティ トランスミッション モードをさらに含む請求項55記載のコンピュータプログラムプロダクト。
- 58前記複数のダイバーシティ トランスミッション モードはウォルシュダイバーシティ トランスミッション モードをさらに含む請求項55記載のコンピュータプログラムプロダクト。
- 59前記選択するための手段は前記複数のダイバーシティ トランスミッション モードの1つか空間多重化モードのいずれかを選択するための手段を含む請求項55記載のコンピュータプログラムプロダクト。
Independent claims59
150 paragraphs, as filed
The present invention relates generally to data communication, and more particularly to data transmission techniques using many diversity transmission modes in MIMO OFDM systems.
Wireless communication systems have been widely deployed, providing various types of communication such as voice and packet data. Such a system is a multiple access system capable of sequentially or simultaneously supporting communication with a plurality of users. This is achieved by sharing available system resources limited by the sum of available operating bandwidth and transmit output.
Multiple access systems include many access points (or base stations) that communicate with many user terminals. Each access point is equipped with one or more antennas that send and receive data. Similarly, each terminal is equipped with one or more antennas.
Transmission between a given access point and a given terminal is characterized by the number of antennas used to send and receive data. In particular, there are (1) multiple (N) pairs of access points and terminals.<sub>T</sub>) Transmitting antenna and plural (N)<sub>R</sub>) As a multiple input multiple output (MIMO) system when used for data transmission, (2) as a multiple input single output (MISO) system when multiple transmitting antennas and a single receiving antenna are used. , (3) Single input when multiple transmitting antennas and multiple receiving antennas are used As a multiple output (SIMO) system, (4) Single input single when using a single transmitting antenna and multiple receiving antennas Considered as an output (SISO) system.
For MIMO systems, N<sub>T</sub>Transmitting antennas and N<sub>R</sub>The MIMO channel formed by the receiving antennas is N<sub>S</sub>Decomposed into independent channels, but here N<sub>S</sub> min {N<sub>T</sub>, N<sub>R</sub>}. This N<sub>S</sub>Each of the independent channels is also called a spatial subchannel of the MIMO channel and corresponds to a dimension. This MIMO system can improve performance by taking advantage of the additional dimensions created by these multiple transmit and receive antennas (eg, increased transmit capacity and / or increased reliability). For MISO systems, only one spatial subchannel is available for data transmission. However, multiple transmitting antennas are used to transmit data to improve the likelihood that the receiver will receive it correctly.
Spatial subchannels in broadband systems encounter different channel situations due to different factors such as fading and multipathing. Thus, each spatial subchannel experiences frequency-selective fading, which is characterized by varying channel gains as frequencies vary over the entire system bandwidth. Frequency selective fading is known to cause inter-symbol interference (ISI), a phenomenon in which each symbol in a received signal acts as a distortion to subsequent symbols in this received signal. This ISI distortion adversely affects the ability to correctly detect received symbols and degrades performance.
To counter frequency-selective fading, use Orthogonal Frequency Division Multiplexing (OFDM) to increase the overall bandwidth of the system (N).<sub>F</sub>Effectively segmented into () sub-bands, which are also referred to as OFDM sub-bands, frequency bins or frequency sub-channels. Each subband is associated with a respective subcarrier to which the data is modulated against it. At each time interval, which depends on the bandwidth of one subband, the modulation symbol is N<sub>F</sub>It is transmitted in each of the subbands.
In the case of a multiple access system, a given access point communicates with terminals with different numbers of antennas at different times. Moreover, the characteristics of the communication channel between the access point and the terminal generally vary from terminal to terminal, and moreover, especially in the case of mobile terminals, over time. Therefore, various transmission methods are required for various terminals depending on their capabilities and requirements.
Therefore, there is a need for data transmission techniques using many diversity transmission modes in the art, depending on the capabilities of the receiver device and the channel conditions.
The present specification provides a technique for transmitting data so as to improve the reliability of data transmission. MIMO OFDM systems are designed to support many modes of operation for data transmission. One such transmission mode is the diversity transmission mode, which is a method used to improve the reliability of certain types of data transmission (eg overhead channels, poor quality channel conditions, etc.). This diversity transmission mode seeks to achieve transmission diversity by establishing orthogonality between a plurality of signals transmitted from a plurality of transmitting antennas. Orthogonality between transmitted signals is achieved as frequency, time, space or a combination thereof. Such transmission modes also include spatial multiplex transmission mode and beam steering transmission mode, which are used to improve the bit rate under certain favorable channel conditions.
In one embodiment, a method of processing data for transmission in a wireless (eg MIMO OFDM) communication system is provided. According to this method, the particular diversity transmission mode used for each of one or more data streams is selected from the many possible transmission modes. Diversity transmission modes each transmit data redundantly for time, frequency, space, or a combination thereof. Each data stream is encoded and modulated to a modulation symbol based on the encoding and modulation scheme selected for this data stream. This modulation symbol for each data stream is this selected diversity transmission Further processed based on the mode, it becomes a transmission symbol. In the case of OFDM, this transmit symbol for all data streams is further OFDM-modulated into a transmit symbol stream for each of one or more transmit antennas used for data transmission. The pilot symbol is also multiplexed with the modulation symbol using frequency division multiplexing (FDM), time division multiplexing (TDM), code division multiplexing (CDM), or a combination thereof.
The above transmission modes include, for example, (1) frequency diversity transmission mode in which modulation symbols are redundantly transmitted over multiple OFDM subbands, and (2) N.<sub>T</sub>OFDM symbol period (N<sub>T</sub>Is the number of transmitting antennas used for data transmission) in Walsh diversity transmission mode, which transmits each modulation symbol, and (3) spatial-time transmission, which transmits modulation symbols with multiple OFDM symbol periods and multiple transmitting antennas. There is a diversity (STTD) transmission mode and (4) a Walsh STTD transmission mode in which modulation symbols are transmitted using a combination of Walsh diversity and STTD. In the case of Walsh diversity transmission mode and Walsh STTD transmission mode, the same modulation symbol is transmitted redundantly on all transmitting antennas, or if the modulation symbols are different, the transmitting antennas for them are also transmitted from different antennas.
Each data stream may be for an overhead channel or targeted for a particular receiver device. The data rate for each user-specific data stream is adjusted based on the transmission capability of this receiver device. The transmission symbol for each data stream is transmitted on each group of one or more subbands.
In another embodiment, a method of processing data transmission in a receiver of a wireless communication system is provided. According to this method, the specific diversity transmission mode used for each of the one or more data streams to be recovered is determined at an early stage. This diversity transmission mode used for each is selected from many possible transmission modes. The received symbol for each data stream is then processed to be a recovered symbol based on the diversity transmission mode used for this data stream, which is the modulation sent by the transmitter for this data stream. Estimated value of the symbol. This recovered symbol for each data stream is further demodulated and decoded into decrypted data for this data stream.
Various aspects and embodiments of the present invention will be further described in detail below. The present invention provides methods, transmitter units, receiver units, terminals, access points, systems and other devices and components that implement various aspects, embodiments and features of the invention, as further described below. Further provide.
The features, properties and advantages of the present invention will become more apparent when reading the following detailed description with the following drawings in which similar reference symbols generally indicate similar parts.
<figref num="1">It is a diagram of a multiple access system that supports many users.</figref><figref num="2">It is a block diagram of an embodiment of an access point and two terminals.</figref><figref num="3">It is a block diagram of a transmitter unit.</figref><figref num="4">FIG. 6 is a block diagram of a TX diversity processor used to implement a frequency diversity scheme.</figref><figref num="5">FIG. 6 is a block diagram of a TX diversity processor used to implement the Walsh diversity scheme.</figref><figref num="6">It is a block diagram of the TX diversity processor used to implement the STTD scheme.</figref><figref num="7">FIG. 6 is a block diagram of a TX diversity processor used to implement the iterative Walsh STTD scheme.</figref><figref num="8">FIG. 6 is a block diagram of a TX diversity processor used to implement a non-repetitive Walsh STTD scheme.</figref><figref num="9">It is a block diagram of a receiver unit.</figref><figref num="10">It is a block diagram of RX diversity processor.</figref><figref num="11">It is a block diagram of the RX antenna processor used for the Walsh diversity scheme in the RX diversity processor.</figref><figref num="12">It is a block diagram of the RX subband processor used for the iterative and non-repetitive Walsh STTD schemes in the RX antenna processor.</figref>
FIG. 1 is a diagram of a multiplex access system 100 that supports many users. System 100 includes one or more access points (APs) 104 that communicate with a number of terminals (T) 106 (for simplicity, only one access point is shown in FIG. 1). Access points are also referred to by base station, UTRAN or some other term. Terminals are also referred to by handset, mobile station, remote station, user device (UE) or some other term. Each terminal 106 communicates with a plurality of access points 104 in parallel when in a soft handoff state (if the soft handoff is supported by the system).
In one embodiment, each access point 104 uses multiple antennas, (1) multiple inputs (MI) for downlink transmission from the access point to the terminal, and (2) from the terminal to the access point. Represents multiple outputs (MO) for uplink transmission. A set of one or more terminals 106 communicating with a given access point collectively represents multiple outputs for downlink transmission and multiple inputs for uplink transmission.
Each access point 104 may communicate with one or more terminals 106 simultaneously or sequentially via a plurality of antennas available at the access point and one or more antennas available at each terminal. It is possible. Terminals that are not in active communication state receive pilot and / or other signal notification information from the access point as indicated by the dashed lines from terminals 106e to 106h in FIG.
For downlink, the access point is N<sub>T</sub>Use one antenna, and each terminal has one or N<sub>R</sub>It uses a single antenna to receive one or more data streams from the access point. Generally, N<sub>R</sub>Can be different for different multi-antenna terminals and can be any integer. N<sub>T</sub>Transmitting antennas and N<sub>R</sub>The MIMO channel formed from the receiving antennas is N<sub>S</sub>Decomposed into independent channels, but here N<sub>S</sub> min {N<sub>T,</sub>N<sub>R</sub>}. Each such independent channel is also referred to as a spatial subchannel of the MIMO channel. A terminal that receives downlink data transmission contents in parallel does not need to be equipped with the same number of receiving antennas.
For downlinks, the number of receiving antennas at a given terminal is greater than or equal to the number of transmitting antennas at the access point (ie, N).<sub>R</sub> N<sub>T</sub>). For such terminals, the number of spatial subchannels is limited by the number of transmitting antennas at the access point. Each of the multi-antenna type terminals has an access point and N of the access point.<sub>T</sub>N of transmitting antennas and their own<sub>R</sub>It communicates via each MIMO channel formed by the receiving antennas. However, even if a plurality of multiple antenna terminals are selected for the purpose of performing downlink data transmission in parallel, only N is selected regardless of the number of terminals that receive the downlink transmission content.<sub>S</sub>Only spatial subchannels are available.
For downlinks, the number of receiving antennas at a given terminal is also less than the number of transmitting antennas at the access point (ie, N).<sub>R</sub><N<sub>T</sub>). For example, MISO terminals are equipped with one receiving antenna for downlink data transmission (N).<sub>R</sub>= 1). The access point then uses diversity, beam steering, time division multiplexing (SDMA), or some other transmission technique to communicate with one or more MISO terminals in parallel.
In the case of uplink, each terminal uses one or more terminals for uplink data transmission purposes. Each terminal also utilizes all or its subsets of available antennas for uplink transmission. N for uplink at any time<sub>T</sub>The transmitting antenna is formed by all the antennas used by one or more active terminals. The MIMO channel will then be N from all active terminals.<sub>T</sub>N of transmitting antennas and access points<sub>R</sub>Formed by a number of receiving antennas. The number of spatial subchannels is limited by the number of transmitting antennas, which is generally limited by the number of receiving antennas at the access point (ie, N).<sub>S</sub> min {N<sub>T</sub>, N<sub>R</sub>})。
FIG. 2 is a block diagram of an embodiment of the access point 104 and the two terminals 106. On the downlink, at the access point 104, various types of traffic data, such as user-specific data and signal notifications from the data source 208, are provided to the transmit (TX) data processor 210. The processor 210 then formats and encodes the traffic data based on one or more coding schemes into encoded data. This encoded data is then interleaved and further modulated based on one or more modulation schemes (ie, symbols are mapped) to become modulation symbols (ie, modulated data). Data rate, coding, interleaving and symbol mapping are determined by control by controller 230 and scheduler 234. The processing by the TX data processor 210 will be described in more detail below.
Next, the transmission processor 220 receives and processes the modulation symbol and the pilot data to obtain a transmission symbol. This pilot data is generally well-known data processed in a well-known manner (if any). In certain specific embodiments, processing by the transmit processor 220 involves: (1) processing a modulation symbol based on one or more transfer schemes selected for data transmission to the terminal to obtain a transmit symbol. (2) It includes processing this transmission symbol by OFDM to make it a transmission symbol. This process by the transmit processor 220 will be described in more detail below.
Transmission processor 220 is N<sub>T</sub>One transmitter corresponds to each of the transmission symbols forming a stream for each of the data transmission transmission antennas.<sub>T</sub>Provided to a number of transmitters (TMTR) 222a to 222t. Each transmitter 222 converts the transmission symbol stream into one or more analog signals and further tunes (eg, amplifies, filters, frequency upconverts) this analog signal for transmission over a radio communication channel. Generate each suitable modulated downlink signal. Each of the modulated downlink signals is then transmitted to the terminal via their respective antenna 224.
At each terminal 106, the modulated downlink signal from the access point's plurality of transmitting antennas is received by one or more antennas 252 available at the terminal. This received signal from each antenna 252 is provided to each receiver (RCVR) 254. Each receiver 254 adjusts the received signal (eg, filtering, amplification and frequency down-conversion) and further digitizes the adjusted signal into their respective sample streams.
The receiving processor 260 then receives and processes this sample stream from all receivers 254 into a recovered symbol (ie, demodulated data). In one specific embodiment, processing by the receiving processor 260 is based on (1) OFDM processing of the received transmission symbol into a received symbol and (2) this received symbol being based on the selected transmission mode. Includes processing to obtain a recovered symbol. This recovered symbol is an estimate of the modulation symbol transmitted by the access point. These processes by the receiving processor 260 will be described in more detail below.
The receive (RX) data processor 262 then symbolically demaps, deinterleaves, and decodes this recovered symbol to send user-specific data and signal notifications over the downlink to the terminal. obtain. The processing by the receiving processor 260 and the RX data processor 262 has a complementary relationship with the processing by the transmitting processor 220 and the TX data processor 210 at the access point.
On the uplink, the terminal 106 outputs various types of traffic data, such as user-specific data from the data source 276 and signal notifications, to the TX data processor 278. The processor 278 encodes these various types of traffic data according to their respective encoding schemes to obtain encoded data, and further interleaves the encoded data. The modulator 280 then symbolically maps this interleaved data into modulated data, which is output to one or more transmitters 254. OFDM may or may not be used for uplink data transmission, depending on the system design. Each transmitter 254 adjusts this received modulated data to generate its own modulated uplink signal, which is then transmitted to the access point via the associated antenna 252.
At the access point 104, a modulated uplink signal from one or more terminals is received by the antenna 224. This received signal from each antenna 224 is provided to the receiver 222, which adjusts and digitizes the received signal into their respective sample streams. These sample streams from all receivers 222 are then processed by demodulator 240 and further decoded by RX data processor 242 (if necessary) to recover the data transmitted by the terminal.
The controllers 230 and 270 instruct the operation of the access point and the terminal, respectively. The memories 232 and 272 store the program code and data used by the controllers 230 and 270, respectively. Scheduler 234 schedules data transmission over the downlink (and possibly the uplink) for the terminal.
For clarity, various transmission diversity schemes for downlink transmission are specifically described below. These schemes are also used for uplink transmission purposes, which are within the scope of the present invention. Also, for clarity, in the following description, in the MIMO OFDM system, the subscript "i" is used as the index of the receiving antenna, "j" is used as the index of the transmitting antenna, and "k" is used as the subband. It is used as an index of.
(Transmitter unit) FIG. 3 is a block diagram of the transmitter unit 300, which is an embodiment of the transmitter portion of the access point 104. The transmitter unit 300 includes (1) a TX data processor 210a that receives and processes traffic data and pilot data to obtain a modulation symbol, and (2) further processes this modulation symbol to obtain N.<sub>T</sub>N for 9 transmitting antennas<sub>T</sub>It includes a transmission processor 220a as a transmission symbol consisting of a stream. The TX data processor 210a and the transmission processor 220a are embodiments of the TX data processor 210 and the transmission processor 220, respectively, in FIG.
In this specific embodiment shown in FIG. 3, the TX data processor 210a includes a encoder 312, a channel interleaver 314, and a symbol mapping element 316. The encoder 312 receives traffic data (ie, information bits) and encodes it based on one or more coding schemes into encoded bits. This coding increases the reliability of data transmission.
In one embodiment, the user-specific data for each terminal and the data for each overhead channel are considered to be clear data streams. This overhead channel includes a broadcast channel, a paging channel, and other common channels that are received by all terminals. Multiple data streams are also sent to a given terminal. Each data stream is encoded independently of each other based on the particular encoding scheme selected for this data stream. Therefore, many independently encoded data streams are output from the encoder 312 towards various overhead channels and terminals.
This particular coding scheme used for each data stream is determined by coding control from controller 230. This coding scheme for each terminal is selected, for example, based on feedback information received from the terminal. Each coding scheme has some forward error detection (FED) code (eg, cyclic redundancy check (CRC) code) and forward error correction (FEC) code (eg, convolutional code, turbo code, block code, etc.). Contains combinations. The coding scheme also does not specify any coding. Binary-based or trellis-based codes are also used for each data stream. Moreover, the convolutional code and the turbo code adjust the code rate using puncturing. More specifically, puncturing is used to increase the code rate so that it is greater than the base code rate.
In certain specific embodiments, the data for each data stream is initially segmented into frames (or packets). For each frame, this data is used to generate a set of CRC bits for this frame, which is then added to the data. These data and CRC bits for each frame are then encoded by a convolutional code or turbo code to produce encoded data for the frame.
The channel interleaver 314 receives this encoded bit and interleaves it based on one or more interleaving schemes. Generally, each coding scheme is associated with its corresponding interleaving scheme. This interleaving provides time diversity for the encoded bits, causing each data stream to be transmitted based on the average SNR of the subband and spatial subbands used for this data stream to counter fading and each. Further remove the correlation between the encoded bits used to form the modulation symbol.
In OFDM, the channel interleaver distributes the encoded data for each data stream into multiple subbands of one OFDM symbol or, in some cases, multiple OFDM symbols. The purpose of this channel interleaver is to randomize this encoded data so that the chances of contiguous encoded bits being corrupted by the communication channel are reduced. When the interleave interval of a given data stream reaches the length of one OFDM symbol, the encoded bits of this data stream are randomly distributed across the subband for this data stream to take advantage of frequency diversity. Will be done. When the interleave interval reaches the length of multiple OFDM symbols, the encoded bits are randomly distributed over the data transmission subband and the interleave interval for multiple symbols, taking advantage of both frequency diversity and time diversity. To do. For wireless local area networks (WLANs), the time diversity achieved by interleaving over multiple OFDM symbols is not important if the minimum expected coherence time of the communication channel is many times longer than the interleaving interval.
The symbol mapping element 316 receives the interleaved data and maps it according to one or more modulation schemes to make it a modulation symbol. Use a specific modulation scheme for each data stream. The symbolic mapping for each data stream is encoded and interleaved q<sub>m</sub>A set of bits is grouped together to form a data symbol, each of which is a non-binary value, during signal constellation corresponding to the modulation scheme chosen to be used for this data stream. Achieved by mapping each data symbol to the point of. This selected modulation scheme is QPSK, M-PSK or some other modulation scheme. Each mapped signal point is a complex number, M<sub>m</sub>Corresponds to the base modulation symbol, but here M<sub>m</sub>Corresponds to this particular modulation scheme selected for the data stream m, M<sub>m</sub>=2<sup>qm</sup>Is. Symbol mapping element 316 provides a stream of modulation symbols for each data stream. The modulation symbol streams for all data streams are collectively shown as the modulation symbol streams s (n) in FIG.
Table 1 lists the various coding and modulation schemes used to achieve a range of spectral efficiency (or bit rate) using convolutional and turbo codes. Each bit rate (in bits / second / Herz or bps / Hz) is achieved using a particular combination of code rate and modulation scheme. For example, a bit rate of half is achieved using a code rate of 1/2 and a BPSK modulation scheme, a bit rate of 1 is achieved using a code rate of 1/2 and a QPSK modulation scheme, and so on. ..
In Table 1, BPSK, QPSK, 16-QAM and 64-QAM are used for the listed bit rates. Other modulation schemes such as DPSK, 8-PSK, 32-QAM, 128-QAM are also used, but are within the scope of the invention. DPSK (Differential Phase Shift Keying) is not used when the communication channel is difficult to track, because coherence criteria are not needed at the receiver to demodulate the DPSK modulated signal. In the case of OFDM, modulation is performed for each subband, and the modulation scheme used for each subband is independently selected.<tables num="1"><img file="JP5080628B2_D0001.tif" /></tables>
Other combinations of code rates and modulation schemes are also used to achieve various bit rates, which are also within the scope of the invention.
In the specific embodiment shown in FIG. 3, the transmit processor 220a is the TX diversity processors 320 and N.<sub>T</sub>Includes several OFDM modulators. Each OFDM modulator contains an inverse fast Fourier transform (IFFT) unit 330 and a cyclic prefix generator 332. The TX diversity processor 320 receives a modulation symbol from the TX data processor 210a and processes it according to one or more selected transmission modes to make it a transmission symbol.
In one embodiment, the TX diversity processor 320 further receives a pilot symbol (ie, pilot data) and transmits it using frequency division multiplexing (FDM) in a subset of available subbands. Multiplex with symbols. An example of the FDM pilot transmission scheme is shown in Table 2. In this example, 64 subbands are available for the MIMO OFDM system, and subband indicators ± 7 and ± 21 are used for pilot transmission. In an alternative embodiment, the pilot symbol is multiplexed with the transmit symbol using, for example, any combination of time division multiplexing (TDM), code division multiplexing (CDM) or FDM, TDM and CDM.
The TX diversity processor 320 outputs one transmit symbol stream to each OFDM modulator. The processing by the TX diversity processor 320 will be described in more detail below.
Each OFDM modulator has its own transmit symbol stream x<sub>j</sub>Receive (n). Within each OFDM modulator, the IFFT unit 330 is a stream x<sub>j</sub>N in (n)<sub>F</sub>Each set of transmission symbols is grouped into a corresponding symbol vector, which is transformed into a time domain representation (called an OFDM symbol) using an inverse fast Fourier transform.
For each OFDM, the cyclic prefix generator 332 iterates over a portion of the OFDM symbol to form the corresponding transmit symbol. Cyclic prefixes ensure that the transmit symbol retains orthogonality in the presence of multipath delay spreading, which improves performance against harmful path effects such as channel dispersion caused by frequency selective fading. .. A fixed or adjustable cyclic prefix is used for each OFDM symbol. As a concrete example of an adjustable cyclic prefix, the system has a bandwidth of 20 MHz, a chip period of 50 ns, and 64 subbands. For this system, each OFDM symbol has a duration of 3.2 μsec (ie 64 × 50 ns). The cyclic prefix for each OFDM system has a minimum length of 4 chips (200ns) and a maximum length of 16 chips (800ns), and the inclusion is 4 chips (200ns). Then, each transmission symbol is cyclic from 200ns to 800ns. Each prefix will have a duration in the range of 3.4 μs to 4.0 μs.
The cyclic prefix generator 332 in each OFDM modulator outputs a stream of transmit symbols to the associated transmitter 222. Each transmitter 222 receives and processes its own transmission symbol stream to generate a modulated downlink signal, which is then transmitted from the associated antenna 224.
Coding and modulation for MIMO OFDM systems is described in more detail in the next US patent pending.
U.S. Patent Application No. 09 / 993,987, entitled "Multiple Access Multiple Inputs Multiple Output (MIMO) Communication Systems," filed November 6, 2001, U.S. Patent Application No. 09 / 854,235, entitled "Methods and Devices for Processing Data in Multiple Input and Multiple Output (MIMO) Communication Systems Using Channel State Information," filed May 11, 2001, -U.S. Patent Application Nos. 09 / 8,26,481 entitled "Methods and Devices for Utilizing Channel State Information in Wireless Communities," both submitted on May 23, 2001 and September 18, 2001, respectively. No. 09 / 956,449, U.S. Patent Application No. 09 / 776,075, entitled "Code Schemes for Wireless Communication Systems," filed February 1, 2001, -US Patent Application No. 09 / 532,492, entitled "High Efficiency, High Performance Communication Systems Using Multicarrier Modulation," filed March 30, 2000.
All of these patent applications are assigned to the assignee of this application and incorporated herein by reference.
MIMO OFDM systems are designed to support many modes of operation for data transmission. These transmission modes include diversity transmission mode, spatial multiplexing transmission mode and beam steering transmission mode.
Spatial multiplexing mode and beam steering mode are used to increase the bit rate under certain favorable channel conditions. These transmission modes are referred to as "Multiple Input Multiple Output (MIMO) Systems with Multiple Transmission Modes" submitted on February 26, 2002, which are assigned and incorporated herein by the assignee of this application. It is further detailed in the title US Patent Application No. 10 / 085,456.
Diversity transmission mode is used to increase the reliability of certain types of data transmission. For example, diversity transmission mode is used for overhead channels on downlinks such as broadcast channels, paging channels, and other common channels. Diversity transmission modes are also (1) all when the transmitter does not have proper channel state information (CSI) for the communication channel, and (2) the channel conditions are bad enough (eg, some mobility conditions). Used for data transmission when (in) and (3) in other situations. When the diversity transmission mode is used for downlink data transmission to terminals, the rate and / or output of each terminal is controlled to improve performance. Many diversity transmission modes are supported, which are described in more detail below.
The diversity transmission mode seeks to achieve transmit diversity by establishing orthogonality between a plurality of signals transmitted from a plurality of transmit antennas. Orthogonality between transmitted signals is achieved as frequency, time, space or a combination thereof. Transmission diversity is established through any one or combination of the following processing techniques:
-Frequency (or subband) diversity. The inherent orthogonality between the subbands provided by OFDM is used to provide diversity for frequency selective fading.
-Transmission diversity using orthogonal functions. A Walsh function or some other orthogonal function is applied to the OFDM symbols transmitted from multiple transmitting antennas to establish orthogonality between the transmitted signals. This scheme is also referred to herein as the "Walsh Diversity" scheme.
-Space-time transmission diversity (STTD). Spatial orthogonality is established between paired transmitting antennas while preserving the high spectral efficiency potential provided by MIMO techniques.
In general, frequency diversity schemes are used to counter frequency selective fading and also operate in the frequency and spatial dimensions. The Walsh diversity scheme and the STTD scheme operate in the time and space dimensions.
For clarity, the processing techniques listed above and some combinations of this will be described using the MIMO OFDM system as an example. In this system, each access point is equipped with four antennas for sending and receiving data, and each terminal is equipped with one or more antennas.
(Frequency diversity) FIG. 4 is a block diagram of the TX diversity processor 320a used to implement the frequency diversity scheme. In the case of OFDM, the subbands are inherently orthogonal to each other. Frequency diversity is established by transmitting the same modulation symbol over multiple subbands.
As shown in FIG. 4, the modulation symbol s (n) from the TX data processor 210 is output to the symbolic repeat unit 410. Unit 410 iterates over each modulation symbol based on the diversity provided for this modulation symbol (eg, dual or quad). The demultiplexer 412 then receives this repeated symbol and the pilot symbol and demultiplexes these symbols to N.<sub>T</sub>Let it be a stream of transmission symbols. A modulation symbol for each data stream is transmitted on each group of one or more subbands assigned to this data stream. Reserve some of the available subband for pilot transmission (eg using FDM). In an alternative example, the pilot symbol is transmitted with the modulation symbol using TDM or CDM.
In general, it is desirable to transmit the ellipsis in subbands separated from each other by at least the coherence bandwidth of the communication channel. Moreover, the modulation symbol is repeated over any number of subbands. The higher the iteration factor, the higher the corresponding redundancy, and the greater the likelihood that the receiver will receive it accurately at the expense of reduced efficiency.
For clarity, a specific example of a frequency diversity scheme will be described by taking the case of a particular MIMO OFDM system with some of the features defined by IEEE Standard 802.11a as an example. This IEEE standard specification is publicly available and incorporated here in September 1999, "Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: High Speed in the 5 GHz Band. Physical Layer (Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer in the 5 GHz Band) is described in the document. This system has an OFDM waveform structure with 64 subbands. Of these 64 subbands, 48 subbands (with the index ± {1, ..., 6,8, ..., 20,22, .., 26}) are used for data, and 4 Sub-band (with an index of ± {7,21}) is used for pilots, DC sub-band (with an index of 0) is unused, and the remaining sub-bands are also unused as protected sub-bands. Make it work.
Table 2 shows specific examples of dual and quad frequency diversity for the above systems. For dual frequency diversity, each modulation symbol is transmitted over two subbands separated by 26 or 27 subbands. For quad frequency diversity, each modulation symbol is transmitted over four subbands separated by 13 or 14 subbands. Other frequency diversity schemes are also implemented, but are within the scope of the invention.<tables num="2"><img file="JP5080628B2_D0002.tif" /></tables>
Frequency diversity schemes are used by transmitters (eg, terminals) that are not equipped with multiple transmitting antennas. In this case, one transmission symbol stream is output from the TX diversity processor 310a. Each modulation symbol in s (n) is repeated and transmitted over multiple subbands. For single antenna terminals, frequency diversity is used to provide robust performance in the presence of frequency selective fading.
Frequency diversity schemes are also used when multiple transmit antennas are available. This is achieved by transmitting the same modulation symbol from all transmitting antennas on a known subband or group of subbands. For example, in a 4-transmit antenna type device, a sub-band for every 4th is assigned to one of these transmit antennas. Then, the transmitting antenna is N<sub>F</sub>It will be associated with different groups with a / 4 subband. For quad frequency diversity, each modulation symbol is transmitted on a set of four subbands, each of which is one of each of the four subband groups associated with a particular transmitting antenna. To. The four subbands in this set are also chosen so that they are as far apart as possible. In the case of dual frequency diversity, each modulation content is transmitted on a set of two subbands, which is one in each group of the two subband groups. Other embodiments of frequency diversity with multiple transmitting antennas are also envisioned, but are also within the scope of the invention. The frequency diversity schemes described above are also used in combination with one or more other transmit diversity schemes, as described below.
(Walsh transmission diversity) FIG. 5 is a block diagram of the TX diversity processor 320b used to implement the Walsh diversity scheme. In the case of this diversity scheme, an orthogonal function (or sign) is used to establish time orthogonality, which itself is used to establish complete transmit diversity on all transmit antennas. This is achieved by repeating the same modulation symbols on these transmitting antennas and time-spreading these symbols with separate orthogonal functions for each transmitting antenna, as described below. Generally, various orthogonal functions such as Walsh function and orthogonal variable diffusion factor (OVSF) code are used. For clarity, the Walsh function is used in the following description.
In the embodiment shown in FIG. 5, the modulation symbol s (n) from the TX data processor 210 is output to the demultiplexer 510, which causes the symbol to be N.<sub>B</sub>Demultiplexed into multiple modulation symbol substreams, one substream corresponds to each subband used for data transmission (ie, the subband that conveys the data). Each modulation symbol substream s (n) is provided for each TX subband processor 520.
Within each TX subband processor 520, the modulation symbol in substream s (n) is N.<sub>T</sub>Transmitting antennas (N in this illustrated system)<sub>T</sub>N for = 4)<sub>T</sub>Provided to the multipliers 524a to 524d. In the embodiment shown in FIG. 5, one modulation symbol s<sub>k</sub>Is (4T<sub>OFDM</sub>)<sup>-1</sup>It is provided to all four multipliers with each four symbol period corresponding to the symbol rate. Each multiplier also has four chips (ie W)<sub>j</sub><sup>4</sup>= {w<sub>1j</sub>, w<sub>2j</sub>, w<sub>3j</sub>, w<sub>4j</sub>}) And receive a separate Walsh function assigned to the transmitting antenna j associated with this multiplier. Then each multiplier will have the symbol s<sub>k</sub>Walsh function W<sub>j</sub><sup>4</sup>Multiplexed with, four transmission symbols {(s<sub>k</sub>w<sub>1j</sub>), (S<sub>k</sub>w<sub>2j</sub>), (S<sub>k</sub>w<sub>3j</sub>), (S<sub>k</sub>w<sub>4j</sub>)}, Which is transmitted in four consecutive OFDM symbol cycles on the subband k of the transmitting antenna j. These four transmission symbols are the original modulation symbols s<sub>k</sub>Has the same size as. However, the sign of each transmission symbol in this sequence depends on the code of the Walsh chip used to generate this code. In this way, the Walsh function is used to time-spread each modulation symbol in four symbol periods. The four multipliers 524a to 520d of each TX subband processor 520 output four transmit symbol substreams to the four buffers / multipliers 530a to 530d, respectively.
Each buffer / multiplexer 530 is N<sub>B</sub>Pilot symbols and N from TX subband processors 520a-520f<sub>B</sub>N for N subbands<sub>B</sub>Receives transmission symbol substreams. Next, each unit 530 multiplexes the transmission symbol and the pilot symbol at each symbol cycle, and transmits the transmission symbol x.<sub>j</sub>Output (n) to the corresponding IFFT unit 330. Each IFFT unit 330 has its own transmit symbol stream x in the manner described above.<sub>j</sub>Receive and process (n).
In the embodiment shown in FIG. 5, one modulation symbol is N from all four transmitting antennas, each with a four-symbol period.<sub>B</sub>It is transmitted over each of the individual data transmission subbands. When using four transmit antennas for data transmission, the spectral efficiency achieved with the Walsh diversity scheme is achieved with a quad frequency diversity scheme that transmits one modulation symbol over four data transmission subbands at each symbol period. Same as spectral efficiency. In a Walsh diversity scheme with four transmitting antennas, the duration or length of the Walsh function is the four OFDM symbols (W).<sub>j</sub><sup>4</sup>(Specified by superscript). Since the information in each modulation symbol is distributed over four consecutive OFDM symbols, the demodulation operation is performed at the receiver based on the four consecutive OFDM symbols received.
In one alternative embodiment, increased spectral efficiency is achieved by transmitting a well-defined modulation symbol (instead of the same modulation symbol) from each transmitting antenna. For example, the demultiplexer 510 has four distinct modulation symbols s.<sub>1</sub>, S<sub>2</sub>, S<sub>3</sub>, S<sub>4</sub>, Are designed to be output from the multipliers 5124a to 524d in each 4-symbol period. Each multiplier 524 then multiplies this Walsh function by a separate modulation symbol into a separate sequence of four transmit symbols. Then, the spectral efficiency of this embodiment is four times that of the embodiment shown in FIG. As another example, the demultiplexer 510 has two known modulation symbols (eg, s).<sub>1</sub>To the multipliers 524a and 524b, s<sub>2</sub>To the multipliers 524c and 524d) are designed to output each with a 4-symbol cycle.
(Space-Time Transmission Diversity (STTD)) Spatial-time transmission diversity (STTD) supports the operation of effectively simultaneously transmitting two independent symbol streams from two antennas while maintaining orthogonality at the receiver. Therefore, the STTD scheme is more spectrally efficient than the Walsh transmission diversity scheme shown in FIG.
The STTD scheme works as follows. s<sub>1</sub>, S<sub>2</sub>It is assumed that the two modulation symbols shown as are transmitted on a given subband. Transmitter is two vectors<u style="single">x</u><sub>1</sub>= [s<sub>1 </sub>s<sub>2</sub><sup>*</sup>]<sup>T</sup>When<u style="single">x</u><sub>2</sub>= [s<sub>2 </sub>-s<sub>1</sub><sup>*</sup>]<sup>T</sup>And generate. Each of these vectors is transmitted sequentially from their respective transmitting antennas in two symbol cycles (ie, vectors).<u style="single">x</u><sub>1</sub>Is transmitted from antenna 1 and vector<u style="single">x</u><sub>2</sub>Contains two elements (transmitted from antenna 2).
If the receiver contains one receiving antenna, the received signal is expressed in matrix form as follows:<maths num="1"><img file="JP5080628B2_D0003.tif" /></maths>
Where r<sub>1</sub>And r<sub>2</sub>Is two symbols received by the receiver in two consecutive symbol cycles, h<sub>1</sub>And h<sub>2</sub>Is the path gain from the two transmitting antennas to the receiving antenna in the subband under consideration, where the path gain is assumed to be constant over the subband and static over a two-symbol period.
n<sub>1</sub>And n<sub>2</sub>Is the two signals received r<sub>1</sub>And r<sub>2</sub>Is the noise associated with.
Then the receiver sent two symbols s<sub>1</sub>And s<sub>2</sub>The estimated value of is derived as follows.<maths num="2"><img file="JP5080628B2_D0004.tif" /></maths>
In one alternative embodiment, the transmitter has two vectors<u style="single">x</u><sub>1</sub>= [s<sub>1 </sub>s<sub>2</sub><sup>*</sup>]<sup>T</sup>When<u style="single">x</u><sub>2</sub>= [-s<sub>2</sub><sup>*</sup><sub></sub>s<sub>1</sub><sup>*</sup>]<sup>T</sup>And, but the elements of these two vectors are transmitted sequentially from the two transmitting antennas in two symbol periods. Then, the received signal is expressed as follows.<maths num="3"><img file="JP5080628B2_D0005.tif" /></maths>
The receiver then derives an estimate of the two transmitted symbols as follows:<maths num="4"><img file="JP5080628B2_D0006.tif" /></maths>
Using two transmitting antennas for data transmission, the spectral efficiency of the STTD scheme is twice that of both the dual frequency diversity scheme with the two transmitting antennas and the Walsh diversity scheme. The STTD scheme effectively transmits at the ratio of one independent modulation symbol per subband with two transmitting antennas in each symbol period, while the dual frequency diversity scheme has every two subbands in each symbol period. Sending at the rate of only one modulation symbol, the Walsh diversity scheme sends at the rate of only one modulation symbol for each subband in two symbol cycles. In the case of the STTD scheme, the information in each modulation symbol is distributed to two consecutive OFDM symbols, so that at the receiver, the demodulation operation is performed based on the two consecutive received OFDM symbols.
FIG. 6 is a block diagram of an embodiment of the TX diversity processor 320c used to implement the STTD scheme. In this embodiment, the modulation symbol s (n) from the TX data processor 210 is output to the demultiplexer 610, which causes the symbol to be 2N.<sub>B</sub>It is demultiplexed into multiple modulation symbol substreams, but two substreams correspond to each subband that carries the data. Each pair of modulation symbol substreams is output to their respective TX subband processor 620. Each modulation symbol substream contains one modulation symbol every two symbol cycles, which is (2T).<sub>OFDM</sub>)<sup>-1</sup>Corresponds to the symbol rate.
Within each TX subband processor 620, a pair of modulation symbol substreams is provided to the space-time encoder 622. For each pair of modulation symbols in these two substreams, the space-time encoder 622 has two vectors.<u style="single">x</u><sub>1</sub>= [s<sub>1 </sub>s<sub>2</sub><sup>*</sup>]<sup>T</sup>When<u style="single">x</u><sub>2</sub>= [s<sub>2 </sub>-s<sub>1</sub><sup>*</sup>]<sup>T</sup>Each of these vectors contains two transmit symbols that are transmitted in two symbol cycles. These two transmission symbols in each vector are the original modulation symbols s<sub>1</sub>And s<sub>2</sub>Has the same size as. However, each of these transmission symbols is rotated in this phase with respect to the original modulation symbol. In this way, each TX subband processor 620 provides two transmit symbol substreams to two buffers / multiplexers 630a and 630b, respectively.
Each buffer / multiplexer 630 has a pilot symbol and N<sub>B</sub>N transmission symbol substreams<sub>B</sub>Received from TX subband processors 620a to 620f, this transmission symbol and pilot symbol are multiplexed for each symbol cycle, and the transmission symbol x<sub>j</sub>Provide the stream (n) to the corresponding IFFT unit 330. Each ITTF unit 330 then processes each transmission symbol stream in the manner described above.
The STTD scheme, incorporated herein by reference, is "Simple Transmission Diversity Techniques for Wireless Communication" by SM Alamouti, IEEE Journal Vol. 16, No. 8, pp. 14511458, in the Select Area for Communications, published October 1998. A simple Transmit Diversity Technique for Wireless Communications) is explained in more detail. The STTD scheme is also transferred to the assignee of this application and incorporated herein by reference under the title "Methods and Systems for Improving Band Efficiency of Multiple Inputs and Multiple Output Channels" submitted on January 5, 2001. It is explained in more detail in US Patent Application No. 09 / 737,602.
(Walsh STTD) The Walsh STTD scheme is a combination of Walsh Diversity and STTD described above. The Walsh STTD scheme is used in systems with three or more transmitting antennas. In the case of Walsh STTD (also called iterative Walsh STTD scheme), which has a scheme in which the symbols are repeated, a pair of modulation symbols transmitted from the two transmitting antennas on a given subband, as described above for Figure 6. Two transmit vectors for each<u style="single">x</u><sub>1</sub>When<u style="single">x</u><sub>2</sub>Is generated. These two transmit vectors are also iterated over multiple pairs of transmit antennas using the Walsh function to achieve orthogonality to this pair of transmit antennas and also provide additional transmit diversity.
FIG. 7 is a block diagram of the TX diversity processor 320d used to implement the Walsh STTD scheme. The modulation symbol s (n) from the TX data processor 210 is output to the demultiplexer 710, which causes the symbol to be 2N.<sub>B</sub>Demultiplexed into multiple modulation symbol substreams, with two substreams corresponding to each subband of data transmission. Each modulation symbol substream is (4T<sub>OFDM</sub>)<sup>-1</sup>Includes one modulation symbol for every four symbol cycles corresponding to the symbol rate of. Each pair of modulation symbol substreams is provided to their respective TX subband processor 720.
Spatial-time encoder 722 in each TX subband processor 720 receives a pair of this modulation symbol substream and every 4 symbol cycles, a pair of modulation symbols {s<sub>1</sub>And s<sub>2</sub>}, But one symbol is obtained from each of the two substreams. Then this modulation symbol pair {s<sub>1</sub>And s<sub>2</sub>Two vectors using}<u style="single">x</u><sub>1</sub>= [s<sub>1 </sub>s<sub>2</sub><sup>*</sup>]<sup>T</sup>When<u style="single">x</u><sub>2</sub>= [s<sub>2 </sub>-s<sub>1</sub><sup>*</sup>]<sup>T</sup>Each of these vectors reaches the length of a 4-symbol period. Space-time encoder 722 is the first vector<u style="single">x</u><sub>1</sub>To the multipliers 724a and 724c, the second vector<u style="single">x</u><sub>2</sub>Is output to the multipliers 724b and 724c. The multipliers 724a and 724c also each have two chips (ie, W).<sub>1</sub><sup>2</sup>= {w<sub>11</sub>, W<sub>21</sub>}) Receive the Walsh function assigned to transmit antennas 1 and 2. Similarly, the multipliers 724c and 724d each have two chips and the Walsh function W assigned to transmitting antennas 3 and 4.<sub>2</sub><sup>2</sup>To receive. Then each multiplier 724 is a vector<u style="single">x</u><sub>j</sub>Multiply each symbol in and the Walsh function to obtain two transmit symbols transmitted in two consecutive symbol cycles on the subband k of the transmit antenna j.
In particular, the multiplier 724a is a vector<u style="single">x</u><sub>1</sub>Each symbol in and Walsh function W<sub>2</sub><sup>2</sup>Multiply with and four transmission symbols {(s<sub>1</sub>w<sub>11</sub>), (S<sub>1</sub>w<sub>21</sub>), (S<sub>2</sub><sup>*</sup>w<sub>11</sub>), (S<sub>2</sub><sup>*</sup>w<sub>21</sub>)}, Which is transmitted in four consecutive symbol cycles. Multiplier 724b is a vector<u style="single">x</u><sub>2</sub>Each symbol in and Walsh function W<sub>1</sub><sup>2</sup>Multiply with and four transmission symbols {(s<sub>2</sub>w<sub>11</sub>), (S<sub>2</sub>w<sub>21</sub>), (-S<sub>1</sub><sup>*</sup>w<sub>11</sub>), (-S<sub>1</sub><sup>*</sup>w<sub>21</sub>)}. Multiplier 724c is a vector<u style="single">x</u><sub>1</sub>Each symbol in and Walsh function W<sub>2</sub><sup>2</sup>Multiply with and four transmission symbols {(s<sub>1</sub>w<sub>12</sub>), (S<sub>1</sub>w<sub>22</sub>), (S<sub>2</sub><sup>*</sup>w<sub>12</sub>), (S<sub>2</sub><sup>*</sup>w<sub>22</sub>)}. Multiplier 724d is a vector<u style="single">x</u><sub>2</sub>Each symbol in and Walsh function W<sub>2</sub><sup>2</sup>Multiply with and four transmission symbols {(s<sub>2</sub>w<sub>12</sub>), (S<sub>2</sub>w<sub>22</sub>), (S<sub>1</sub><sup>*</sup>w<sub>12</sub>), (-S<sub>1</sub><sup>*</sup>w<sub>22</sub>)}. Using the Walsh function in this way, a vector with two symbol periods<u style="single">x</u>Time spread each symbol or element inside. The four multipliers 724a to 724d of each TX subband processor 720 output four transmit symbol substreams to each of the four buffers / multiplexers 730a to 730d.
Each buffer / multiplexer 730 is N<sub>B</sub>Pilot symbol and N from TX subband processor 720a-720f<sub>B</sub>Receives a transmission symbol substream, multiplexes this pilot symbol and transmission symbol for each symbol cycle, and transmits the transmission symbol x<sub>j</sub>Output the stream (n) to the corresponding IFFT unit 330. The subsequent processing is as described below.
The iterative Walsh STTD scheme (with four transmitting antennas) shown in FIG. 7 has the same spectral efficiency as the STTD scheme shown in FIG. 6 and twice the spectral efficiency of the Walsh diversity scheme shown in FIG. However, this Walsh STTD scheme provides additional diversity by transmitting repeated symbols on multiple pairs of transmitting antennas. Walsh STTD processing provides full transmit diversity (per subband) for signals transmitted from all transmit antennas.
FIG. 8 is a block diagram of the TX diversity processor 320e used to implement a Walsh STTD (also called a non-repetitive Walsh STTD scheme) without an ellipsis scheme. This scheme is used to improve spectral efficiency at a lower cost of diversity than the scheme shown in Figure 7. Modulation symbols s (n) are provided to the demultiplexer 810, where these symbols are 4N, as shown in FIG.<sub>B</sub>It is demultiplexed into multiple modulation symbol substreams, but four substreams correspond to each data transmission subband. Each set of four modulation symbols is provided to each TX subband processor 820.
Within each TX subband processor 820, the space-time encoder 822a receives the first modulation symbol substream pair and the space-time encoder 822b receives the second modulation symbol substream pair. For each modulation symbol pair in the two substreams of the first pair, the space-time encoder 822a has two vectors.<u style="single">x</u><sub>1</sub>= [s<sub>1 </sub>s<sub>2</sub><sup>*</sup>]<sup>T</sup>When<u style="single">x</u><sub>2</sub>= [s<sub>2 -</sub>s<sub>1</sub><sup>*</sup>]<sup>T</sup>And are provided to the multipliers 824a and 824b, respectively. Similarly, for each modulation symbol pair in the two substreams of the second pair, the space-time encoder 822b has two vectors.<u style="single">x</u><sub>3</sub>= [s<sub>3 </sub>s<sub>4</sub><sup>*</sup>]<sup>T</sup>When<u style="single">x</u><sub>4</sub>= [s<sub>4 -</sub>s<sub>3</sub><sup>*</sup>]<sup>T</sup>And are provided to the multipliers 824c and 824d, respectively.
The multipliers 824a and 824b are also Walsh functions W, respectively.<sub>1</sub><sup>2</sup>And also the multipliers 824c and 824d, each with a Walsh function W<sub>2</sub><sup>2</sup>To receive. Then each multiplier 824 is a vector<u style="single">x</u><sub>j</sub>Multiply each symbol in and the Walsh function to obtain two transmit symbols transmitted in two consecutive symbol cycles on the subband k of the transmit antenna j. The four multipliers 824a through 824d of each TX subband processor 820 provide four transmit symbol substreams, respectively, for four buffers / multiplexers 830a-830d.
Each buffer / multiplexer 830 has a pilot symbol and N<sub>B</sub>Send symbol substream and N<sub>B</sub>Received from the TX subband processors 820a-820f, this pilot symbol and transmission symbol are multiplexed for each symbol cycle, and the transmission symbol x<sub>i</sub>Provide the stream (n) to the corresponding IFFT unit 330. The subsequent processing will be described below.
The non-repetitive Walsh STTD scheme shown in FIG. 8 (with four transmitting antennas) has twice the spectral efficiency of the repetitive Walsh STTD scheme shown in FIG. This same process extends to systems with multiple transmit antenna pairs. Instead of iterating over the two transmit vectors on these transmit antenna pairs, each transmit antenna pair is used to transmit an independent symbol stream. As a result, spectral efficiency is improved, but diversity performance is sometimes sacrificed. Part of this diversity is restored using a forward error correction (FEC) code.
The Walsh STTD scheme is also further detailed in US Patent Application No. 09 / 737,602 described above.
(Frequency STTD) The frequency STTD scheme uses a combination of frequency diversity and STTD. The frequency STTD scheme also uses antenna diversity for systems with two or more pairs of transmitting antennas. For frequency STTD schemes, each modulation symbol is transmitted over multiple (eg, two) subbands and output to multiple TX subband processors. The subbands used for each modulation symbol are selected so that these subbands are as far apart as possible (eg, as shown in Table 1) or based on some other subband allocation scheme. If four transmit antennas are available, two pairs of modulation symbols are processed using STTD for each subband. The first modulation symbol pair is transmitted from the first antenna pair (eg, transmitting antennas 1 and 2), and the second modulation symbol pair is transmitted from the second antenna pair (eg, transmitting antennas 3 and 4).
In this way, each modulation symbol is transmitted on a plurality of subbands and from a plurality of transmitting antennas. For clarity, a given modulation symbol s for a system with four transmitting antennas and dual frequency diversity.<sub>a</sub>The processing of is executed as follows. Modulation symbol s<sub>a</sub>Initially for two TX subband processors (eg subbandk k and k + N)<sub>F</sub>Provided (at / 2). In subband k, the modulation symbol s<sub>a</sub>Is another modulation symbol s using STTD<sub>b b</sub>Processed with two vectors<u style="single">x</u><sub>1</sub>= [s<sub>a </sub>s<sub>b b</sub><sup>*</sup>]<sup>T</sup>When<u style="single">x</u><sub>2</sub>= [s<sub>b -</sub>s<sub>a</sub><sup>*</sup>]<sup>T</sup>And, which are transmitted from transmitting antennas 1 and 2, respectively. Subband k + N<sub>F</sub>In / 2, the modulation symbol s<sub>a</sub>Is another modulation symbol s using STTD<sub>c</sub>Processed with two vectors<u style="single">x</u><sub>3</sub>= [s<sub>a </sub>s<sub>c</sub><sup>*</sup>]<sup>T</sup>When<u style="single">x</u><sub>4</sub>= [s<sub>c-</sub>s<sub>a</sub><sup>*</sup>]<sup>T</sup>And are transmitted from transmitting antennas 3 and 4, respectively. Modulation symbol s<sub>a</sub>Is the modulation symbol s<sub>b b</sub>It may be the same as, or it may be a different modulation symbol.
In the case of the above embodiment of the frequency STTD scheme, the modulation symbols in each subband have twice the transmit diversity provided by the STTD process. Each transmitted modulation symbol has a 4x transmission diversity, plus some frequency diversity provided by using two subbands and STTD. This frequency STTD scheme has the same spectral efficiency as the iterative Walsh STTD scheme. However, the total transmission time for each modulation symbol is two symbol cycles in the frequency STTD scheme, which is half the total transmission time for each modulation symbol in the Walsh STTD scheme, which is Walsh processing frequency STTD. This is because it is not executed in the scheme.
In one embodiment of the frequency STTD scheme, all subbands are used by each transmitting antenna pair for data transmission. In the case of quad diversity, each modulation symbol is provided in two subbands for a pair of two transmitting antennas, as described above. In another embodiment of the frequency STTD scheme, each transmitting antenna pair is assigned to a separate subband group for data transmission. For example, in a device with two transmitting antenna pairs, every other subband is assigned to one transmitting antenna pair. Now each transmitting antenna pair is N<sub>F</sub>/ Associated with separate groups of 2 subbands. In the case of quad diversity, each modulation symbol is transmitted in two subbands, one for each of the two subband groups in which each group is associated with a particular transmit antenna pair. The two subbands for each modulation symbol are chosen to be as far apart as possible. Other examples of frequency STTD diversity with multiple transmit antenna pairs are also conceivable, but these are also within the scope of the invention.
As described above, various diversity schemes are implemented using various processing techniques as described herein. For clarity, specific examples of various diversity schemes for specific systems have also been described above.
Moreover, other diversity schemes are also implemented based on other combinations of processing techniques described herein, which are also within the scope of the invention. For example, there are other diversity schemes that utilize frequency diversity and Walsh transmit diversity, and there are yet other diversity schemes that utilize frequency diversity, Walsh diversity and STTD.
(Diversity transmission mode) Many diversity transmission modes are implemented using the transmission processing scheme described above. These diversity transmission modes include:
-Frequency diversity Transmission mode Use only frequency diversity (eg, dual, quad, or some other integer multiple frequency diversity).
-Walsh Diversity Transmission Mode-Use only Walsh Transmission Mode.
-STTD transmission mode Use only STTD.
-Walsh STTD Transmission Moderush Uses both diversity and STTD, but may be symbolic iterative or non-repetitive.
-Frequency STTD Transmission mode Use frequency diversity and STTD.
-Frequency STTD Transmission mode Uses frequency diversity and Walsh transmission diversity.
-Frequency Walsh STTD Transmission mode Use frequency diversity, Walsh transmission diversity and STTD.
Diversity transmission mode is used for data transmission between the access point and the terminal. Which transmission mode is specifically used for a given data stream is as follows: (1) The type of data being transmitted (eg, data that is common to all terminals or for a particular terminal). User-specific data), (2) number of antennas available at the transmitter or receiver, (3) channel status, (4) data transmission requirements (eg, required packet error rate) ), Etc. are determined by various factors.
Each access point in this system is equipped with, for example, four antennas for transmitting and receiving data. Each terminal is equipped with one, two, four or any other number of antennas for sending and receiving data. The default diversity transmission mode is defined and used for each terminal type. In some specific embodiments, the following diversity transmission modes are used as defaults.
Single antenna terminal-using dual or quad diversity frequency diversity transmission mode, Dual antenna terminals-use STTD transmission mode for dual diversity and frequency STTD transmission mode for quad diversity, Cud Antenna Terminal-Uses STTD transmission mode for dual diversity and Walsh STTD transmission mode for quad diversity.
Other diversity transmission modes are also selected as the default mode, which is within the scope of the present invention.
Diversity transmission mode is also used to improve the reliability of data transmission over overhead channels that are to be received by all terminals in the system. In one embodiment, a particular diversity transmission mode is used for the broadcast channel, which is speculatively known by all terminals in the system (ie, identifies the transmission mode used for this broadcast channel). No signal notification is required to do this). In this way, the terminal can process and recover the data transmitted on the broadcast channel. The transmission mode used for other overhead channels can be fixed or dynamically selected. In one dynamic selection scheme, the system uses the transmission for each of the remaining overhead channels. Which mode is the most reliable (and spectrally efficient) is determined based on the mixture of terminals being serviced. The transmission mode and other configuration information selected to be used for these overhead channels are signaled to the terminal, for example, via the broadcast channel.
In OFDM, subbands are treated as known transmission lines, and the same or different transmission modes are used for these subbands. For example, one diversity transmission mode may be used for all data transmission subbands, or separate diversity transmission modes may be selected for each data transmission subband. Moreover, different diversity transmission modes can be used for a given subband with different sets of transmitting antennas.
In general, each data stream (whether for overhead channels or for a particular receiver device) is encoded, modulated, and modulated based on the encoding and modulation scheme chosen for this data stream. It becomes a symbol. The modulation symbol is then further processed based on the diversity transmission mode selected for this data stream to become the transmission symbol. This transmit symbol is further processed and transmitted on a group of one or more subbands from a set of one or more transmit antennas designed to be used for this data stream.
(Receiver device) FIG. 9 is a block diagram of the receiver unit 900, which is an embodiment of the receiver portion of the multi-antenna type terminal 106. The modulated downlink signal from the access point 104 is received by the antennas 252a to 252r, and this received signal is provided from each antenna to the respective receiver 254. Each receiver 254 processes this received signal (eg, tuning, digitizing and demodulating data) into a stream of received transmit symbols, which is then provided to each OFDM demodulator in the receiving processor 260a. Will be done.
Each OFDM demodulator includes a cyclic prefix stripping unit 912 and a fast Fourier transform (FFT) unit 914. Unit 912 removes the cyclic prefix attached to each transmit symbol to the corresponding received OFDM symbol. This cyclic prefix removal operation is the N corresponding to each received send symbol.<sub>A</sub>Determine the number of samples and these N<sub>A</sub>N for the OFDM symbol for which samples have been received<sub>F</sub>Performed by selecting as a set of samples. The FFT914 then receives each received OFDM symbol (or N).<sub>F</sub>Each set of samples) is transformed using the Fast Fourier Transform to N<sub>F</sub>N for N subbands<sub>F</sub>Let it be a vector of received symbols. FFT units 914a to 914r are N<sub>F</sub>Received symbol stream r<sub>1</sub>(n) to r<sub>NR</sub>(n) is provided to the RX diversity processor 920.
RX diversity processor 920 is N<sub>R</sub>Let the symbol s ^ (n) be recovered by performing diversity processing on the received symbol stream, which is an estimate of the modulation symbol s (n) sent from the transmitter. This process performed by the RX diversity processor 920 depends on the transmission mode used for each data stream to be recovered, as indicated by the transmission mode control. Next, the RX diversity processor 920 will be described in more detail below.
The RX diversity processor 920 provides the recovered symbol s ^ (n) for all data streams to be recovered to the RX data processor 262a, which is an embodiment of the RX data processor 262 of FIG. Processor 262a demodulates the symbol demapping element 942, the recovered symbol for each data stream, according to a demodulation scheme that is complementary to the modulation scheme used for this data stream. The channel reverse interleaver 944 then reverse interleaves this demodulated data in such a way that it is complementary to the interleaving performed on the transmitter for this data stream, and this reverse interleaving is performed. The data is further decoded by the decoder 946 in such a way that it is complementary to the encoding performed at the transmitter. For example, if turbo coding or convolutional coding is performed at the transmitter, respectively, a turbo decoder or Viterbi decoder is used in place of the decoder 946. This decrypted data from decoder 946 represents an estimate of the recovered transmitted data. The decoder 946 also outputs the status of each received packet (eg, indicating whether it was received correctly or incorrectly).
In the embodiment shown in FIG. 9, the channel estimator 950 estimates various channel features such as channel response and noise variance (eg, based on the recovered pilot symbol) and provides these estimates to controller 270. .. The controller 270 is designed to perform various functions related to diversity processing at the receiver. For example, controller 270 determines the diversity transmission mode used for each recovered data stream and also directs the operation of RX diversity processor 920.
FIG. 10 is a block diagram of an embodiment of an RX diversity processor used for a multi-channel receiver device. In this embodiment, N<sub>R</sub>N for N receiving antennas<sub>R</sub>The received symbol stream is N<sub>R</sub>Provided to the RX antenna processors 1020a to 1020r. Each RX antenna processor 1020 has its own received symbol stream r<sub>i</sub>Process (n) and output the corresponding recovered symbol stream s ^ (n) to the associated receiving antenna. In one alternative embodiment, one or more RX antenna processors 1020 are used in a time division manner, N.<sub>R</sub>Process all received symbol streams.
Next, combiner 1030 is N<sub>R</sub>N via 10 RX antenna processors 1020a to 1020r<sub>R</sub>Receives and combines the recovered symbol streams into one recovered symbol stream s ^ (n). This compositing operation is performed symbol by symbol. In one embodiment, for a given subband k, N for each symbol period<sub>R</sub>N from receiving antennas<sub>R</sub>Recovered symbols {s ^<sub>ki</sub>} (Here, i = 1,2, ..., N<sub>R</sub>) In the initial stage, N<sub>R</sub>N assigned to each receiving antenna<sub>R</sub>Scaled by individual weights. Then N<sub>R</sub>The scaling symbols are summed and the recovered symbol s ^ for the subband k<sub>k</sub>Will be. These weights are chosen to achieve maximum ratio synthesis and are determined based on the signal quality associated with the receiving antenna (eg, SNR). Scaling with this weight is also performed via an automatic gain control (AGC) loop maintained for each receiving antenna, as is well known in the art.
For single-antenna receiver devices, only one symbol stream is received. In this case, only one RX antenna processor 1020 is needed. The design of the RX antenna processor 1020 is further detailed below.
The recovered symbol stream s ^ (n) provided by combiner 1030 contains recovered symbols for all data streams transmitted from the transmitter. In an alternative example, this stream s ^ (n) contains only one recovered symbol for one or more data streams recovered by the receiver device.
FIG. 11 is a block diagram of the RX antenna processor 1020x used to perform receive processing for the Walsh diversity scheme shown in FIG. RX antenna processor 1020x, received symbol stream r for one receiving antenna<sub>i</sub>(n) is processed and used for each of the RX antenna processors 1020a to 1020r shown in FIG.
In the embodiment shown in FIG. 11, the received symbol stream r<sub>i</sub>(n) is provided to the demultiplexer 1110, where r<sub>i</sub>The received symbol in (n) is the received symbol N<sub>B</sub>Substreams (r<sub>1</sub>From r<sub>NB</sub>However, the indicator i is dropped here for simplicity), and one substream corresponds to each data transmission subband. Then each received symbol substream r<sub>k</sub>Is provided for each RX subband processor 1120.
Each RX subband processor 1120 contains many receive processing paths, one of which corresponds to each transmit antenna used for data transmission (4 receive processing paths for 4 transmit antennas). Shown in 11). For each processing path, the received symbol in the substream is provided to multiplier 1122, which is also scaled to the Walsh function h ^.<sup>*</sup><sub>kj</sub>(W<sub>j</sub><sup>4</sup>)<sup>*</sup>Receives, but here h ^<sup>*</sup><sub>kj</sub>Is the conjugate complex of the estimated channel response between the transmitting antenna (which is associated with this multiplier) and the receiving antenna for the subband k, (W).<sub>j</sub><sup>4</sup>)<sup>*</sup>Is the conjugate complex of the Walsh function assigned to the transmitting antenna j. Each multiplier 1122 then multiplies the received symbol by the scaled Walsh function and provides this result to the associated integrator 1124. The integrator 1124 then integrates the multiplier result over the length of the Walsh function (ie, four symbol periods) and provides this integral output to the adder 1126. One received symbol is provided to multiplier 1122 for each symbol period (ie rate = (T).<sub>OFDM</sub>)<sup>-1</sup>), The integrator 1124 provides one integrated output for each four symbol period (ie rate = (4T).<sub>OFDM</sub>)<sup>-1</sup>)。
Every four symbol periods, the adder 1126 synthesizes the four outputs of the integrators 1124a to 1124d for the subband k and widens the symbol s ^.<sub>k</sub>However, this is the modulation symbol s transmitted in this subband.<sub>k</sub>Is an estimate of. Every 4 symbol cycles, the RX subband processors 1120a to 1120f have widened symbols s ^ with NB data transmission subbands.<sub>1</sub>From s ^<sub>NB</sub>I will provide a.
The multiplier 1140 receives the recovered symbols from the RX subband processors 1120a to 1120f and multiplexes these symbols into the recovered symbol stream s ^ (n) for the receiving antenna i.
FIG. 12 is a block diagram of the RX subband processor 1120x used to perform receive processing in the case of the Walsh STTD scheme shown in FIGS. 7 and 8. The RX subband processor 1120x has received symbol substream r in one subband of one receiving antenna.<sub>k</sub>And also used for each of the RX subband processors 1120a to 1120f in FIG. In the embodiment shown in FIG. 12, the substream r<sub>k</sub>The received symbol inside is provided for two receive processing paths, but one path corresponds to each transmit antenna pair used for data transmission (2 for four transmit antennas in Figure 12). Two receive processing routes are shown). For each processing path, the received symbol is provided to the multiplier 1222, which is also the conjugate complex Walsh function (W) assigned to the transmitting antenna pair being processed on this path.<sub>j</sub><sup>2</sup>)<sup>*</sup>To receive. Each multiplier 1222 then multiplies this received symbol by the Walsh function and provides the result to the associated integrator 1224. The integrator 1224 then integrates the multiplier result over the length of the Walsh function (ie, a two-symbol period) and provides the integrated output to the delay element 1226 and unit 1228. One received symbol is provided to the multiplier 1222 for each symbol period (ie rate = (4T).<sub>OFDM</sub>)<sup>-1</sup>), The integrator 1224 provides one integral output every two symbol periods (ie rate = (2T).<sub>OFDM</sub>)<sup>-1</sup>)。
Seeing Figure 8 again, for the non-repetitive Walsh STTD scheme, the four modulation symbols {s<sub>k1</sub>, S<sub>k2</sub>, S<sub>k3</sub>, S<sub>k4</sub>} Is transmitted from two transmitting antenna pairs with four symbol periods for the subband k (where the index k is used to indicate the subband k). Symbol pair {s<sub>k1</sub>, S<sub>k2</sub>} Is transmitted from the first transmitting antenna pair, and the symbol pair {s<sub>k3</sub>, S<sub>k4</sub>} Is transmitted from the second transmitting antenna pair. Each modulation symbol is transmitted in a 2-symbol cycle using the 2-chip Walsh function assigned to the transmitting antenna pair.
With reference to FIG. 12 again, complementary processing is performed at the receiver to recover the modulation symbol. For every four symbol periods corresponding to the new symbol pairs transmitted from each transmit antenna pair in subband k, the integrator 1224 receives received symbol pairs {r.<sub>k1</sub>, R<sub>k2</sub>} Is output. Then the first symbol of this pair (ie, r)<sub>k1</sub>) The delay element 1226 outputs a delay of 2 symbol cycles (ie, T).<sub>w</sub>= 2T<sub>OFDM</sub>But this is the length of the Walsh function), and unit 1228 is the second symbol of this pair (ie, r).<sup>*</sup><sub>k2</sub>) Is output as the conjugate complex number.
Next, the multipliers 1230a to 1230d and the adders 1232a to 1232b collectively execute the operations shown in Eq. (2) on the first transmitting antenna pair. In particular, the multiplier 1230a has the symbol r<sub>k1</sub>And channel response estimates h ^<sup>*</sup><sub>k1</sub>Multiply and the multiplier 1230b is the symbol r<sup>*</sup><sub>k2</sub>And channel response estimates h ^<sub>k2</sub>Multiply and the multiplier 1230c is the symbol r<sub>k1</sub>And channel response estimates h ^<sup>*</sup><sub>k2</sub>Multiply and the multiplier 1230d is the symbol r<sup>*</sup><sub>k2</sub>And channel response estimates h ^<sub>k1</sub>Multiply, but here h ^<sub>kj</sub>Is an estimate of the channel response from the transmitting antenna j to the receiving antenna for the subband k. The adder 1232a then subtracts the output of the multiplier 1230b from the output of the multiplier 1230a to pair {s.<sub>k1</sub>, S<sub>k2</sub>} Estimated value of the first modulation symbol in s ^<sub>k1</sub>And. The adder 1232b adds the output of the multiplier 1230c and the output of the multiplier 1230d to the estimated value s of the second modulation symbol in this pair.<sub>k2</sub>And.
The processing by the second path for the second transmitting antenna pair is similar to the above processing of the first path. However, the channel response estimate of the second transmitting antenna pair for the subband k h ^<sup>*</sup><sub>k3</sub>And h ^<sup>*</sup><sub>k4</sub>Is used for the second processing path. Every four symbol cycles, the second processing path is the modulation symbol pair {s transmitted from the second transmitting antenna pair in the subband k.<sub>k3</sub>, S<sub>k4</sub>Symbolic estimate for} s ^<sub>k3</sub>And s ^<sub>k4</sub>And provide.
For the non-repeating Walsh STTD scheme shown in Figure 8, s ^<sub>k1</sub>, S ^<sub>k2</sub>, S ^<sub>k3</sub>, S ^<sub>k4</sub>Is the four modulation symbols s sent from the four transmit antennas on the subband k with a four symbol period.<sub>k1</sub>, S<sub>k2</sub>, S<sub>k3</sub>, S<sub>k4</sub>Represents an estimate of. These symbol estimates are then multiplexed to recover the symbol substream s ^ for the subband k ^.<sub>k</sub>(n), which is then provided to the multiplexer 1140 of FIG.
For the iterative Walsh STTD scheme shown in Figure 7, one symbol pair {s<sub>k1</sub>, S<sub>k2</sub>} Is sent from both pairs of transmitting antennas on the subband k every 4 symbol cycles. Next, the symbol estimate s ^<sub>k1</sub>And s ^<sub>k3</sub>Is combined with an adder (not shown in Figure 12) to give an estimate of the first symbol in China, the symbol estimate s ^<sub>k2</sub>And s ^<sub>k4</sub>Is similarly combined with another adder to give an estimate of the second symbol in China. The symbolic estimates from these two adders are then multiplexed together into a recovered symbolic substream s ^ (n) for subbandk k, which is then provided to multiplexer 1140 in FIG.
For clarity, various details have been specifically described for downlink data transmission from the access point to the terminal. The techniques described herein are also used for uplinks, which are also within the scope of the invention. For example, the processing schemes shown in FIGS. 4, 5, 6, 7, and 8 are implemented within a multi-antenna terminal for uplink data transmission.
The MIMO OFDM systems described herein also implement one or more multiple access schemes such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), and the like. It is designed to be. CDMA has certain advantages, such as increased system capacity compared to other types of systems. MIMO OFDM systems are also designed to implement various processing techniques described in CDMA standards, such as IS-95, cdma2000, IS-856, W-CDMA and others.
The techniques described herein for sending and receiving data using many diversity transmission modes are implemented by a variety of means. For example, these techniques are performed in hardware, software or a combination thereof. When implemented in hardware, the elements used to implement any one or combination within these techniques (eg, TX diversity processor, RX diversity processor, TX subband processor, RX antenna processor, RX subband processor, etc.) ) Are one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmed gate arrays (FPGAs), processors, It is carried out within a controller, a microcontroller, another electronic unit designed to perform the functions described herein, or a combination thereof.
When implemented in software, any one or combination of the techniques described herein is performed in a module (eg, procedure, function, etc.) that performs the functions described herein. The software code is stored in a memory unit (eg, memory 232 or 272 in FIG. 2) and executed by a processor (eg, controller 230 or 270). This memory unit is implemented on or outside the processor, in which case it is communicably coupled to the processor by various means, as is well known in the art.
Headings are included herein for reference and to assist in locating sections. These headings are not intended to limit the scope of the concepts described herein, and these concepts may be applied in other sections throughout the specification.
The disclosed embodiments have been described above to allow any person skilled in the art to make and use the present invention. Various modifications of these embodiments will be readily apparent to those of skill in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit or scope of the invention. Is also applied. Accordingly, the present invention is not intended to limit the embodiments presented herein, and is provided with the broadest scope consistent with the principles and novel features disclosed herein.
100 ... Multiple Access System, 104 ... Access Point, 106 ... Terminal, 208,276 ... Data Source, 210,278 ... TX Data Processor, 220 ... Transmit Processor, 234 ... Scheduler, 230,270 ... controller, 232,272 ... memory, 244,264 ... data sink, 242,262 ... RX data processor, 240 ... demodulator, 260 ... receive processor, 280 ... modulator, 312 .. .Signer, 314 ... Channel Interleaver, 316 ... Symbol Mapping, 320 ... TX Diversity Processor, 332 ... Cyclic Prefix Generator, 412,510,610,710,810,1110 ... Demultiplexer, 520f, 620f, 720f, 820f ... TX Subband Processor, 524,724 ... Multiplier, 530a-d, 630a, 630b, 730a-d, 830a-d. .. Buffer / Multiplexer, 622,722,822a, b ... Spatial-Time Coder, 920 ... RX Diversity Processor, 942 ... Symbol Demapping, 944 ... Channel Reverse Interleaver, 946 ... Decoder, 950 ... channel estimator, 270 ... controller, 272 ... memory, 1020a, r ... RX antenna processor, 1030 ... combiner, 1124a-d, 1224a-d ... integrator, 1140 ... multiplexer, 1120f ... RX subband processor, 1226a, b ... delay T<sub>w</sub>
18 sheets
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Every citation, both ways
| Document | Relation | Office |
|---|---|---|
| WO01071928A1 | Cites | World Intellectual Property Organization (WIPO) |
| JP2002135232A | Cites | Japan |
| JP2002044051A | Cites | Japan |
| WO00014921A1 | Cites | World Intellectual Property Organization (WIPO) |
45 members in 16 offices
Priority claims5
| Document | Office | Kind | Date |
|---|---|---|---|
| 10179439 | United States of America | – | |
| 17943902 | United States of America | A | |
| 17943902 | United States of America | A | |
| 2002179439 | – | – | – |
| US20020179439 | – | – | – |
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| TW200408216A | Taiwan Province of China | A | |
| KR20050013624A | Republic of Korea | A | |
| NO20050350L | Norway | L | |
| EP1516441A1 | European Patent Office (EPO) | A1 | |
| MXPA05000098A | Mexico | A | |
| RU2005101415A | Russian Federation | A | |
| CN1675853A | China | A | |
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| JP2011050074A | Japan | A | |
| US7990841B2 | United States of America | B2 | |
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| EP2254262A3 | European Patent Office (EPO) | A3 | |
| JP5080628B2This record | Japan | B2 | |
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| RU2474955C2 | Russian Federation | C2 | |
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Numbers
- Publication
- 5080628
- Publication, DOCDB
- 5080628
- Publication, EPODOC
- JP5080628B
- Application
- 224047
- Application, DOCDB
- 2010224047
- Application, EPODOC
- JP20100224047
Titles2
- Japanese
- MIMOOFDM通信システム用のダイバーシティ通信システム
- English
- Diversity communication system for MIMO OFDM communication system
Classification
- CPC, 11
- H04L5/0028
- H04B7/0413
- H04B7/0669
- H04B7/0678
- H04B7/0697
- H04L1/0001
- H04L1/0618
- H04L5/0007
- H04L5/0016
- H04L5/0023
- H04L27/26
- IPC, 11
- H04J99 00
- H04J11 00
- H04B7 04
- H04B1 00
- H04B7 02
- H04B7 06
- H04B7 12
- H04B7 26
- H04L1 00
- H04L1 06
- H04L27 26
