MXPA06006570A - Control signal transmitting method in multi-antenna system - Google Patents

Abstract

A method of communication in a Multiple Input Multiple Output (MIMO) system having multiple transmitters including transmitting independent parallel downlink control signals including control information for each data stream, and transmitting the data streams.

Description

METHOD OF TRANSMISSION OF CONTROL SIGNAL IN A MULTIPLE ANTENNA SYSTEM TECHNICAL FIELD The present invention relates to a mobile communication system and more particularly to a method for transmitting a discharge control signal in a mobile communication system using multiple antennas.

TECHNICAL BACKGROUND The rapid growth in mobile wireless communication systems now includes requests for multimedia services, which require an increase in data transmission capacity and a faster data rate. A high-speed downlink packet access (HS-DPA) system is currently used to provide multimedia services and is designed to provide high-speed data transfer. See, for example, JUHUA KORHONEN, INTRODUCTION TO 3G MOBILE COMMUNICATIONS SYSTEMS (2nd ed 2003), whose total contents are incorporated herein by reference in their entirety. In the communication systems described above, a base station refers to a node B, and a mobile terminal, subscriber equipment, etc., refers to a user equipment (UE). However, the current HS-DPA system uses a single antenna and is unable to meet the increased demands for increasingly high data rates.

BRIEF DESCRIPTION OF THE INVENTION Also, an object of the present invention is to address at least the above problems and other previously noted problems. Another object of the present invention is to provide a method for discriminating channels through which control signals are transmitted for separate data streams. To achieve at least the above objectives in whole or in part, the present invention provides a novel method of communication in a multiple input multiple output (MIMO) system having multiple transmitters. The method includes transmitting independent parallel downlink control signals including control information for each data stream, and transmitting the data streams. Advantages, objects and additional features of the invention will be set forth in part in the description that follows and in part will be apparent to those skilled in the art upon examination of the following or can be learned from the practice of the invention. The objects and advantages of the invention can be realized and achieved as is particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in detail with reference to the following drawings in which similar reference numerals refer to similar elements where: Figure 1 is an overview illustrating a transmission end of a multiple input multiple output system (MIMO); Figure 2 is an overview illustrating a receiver end of the MIMO system; Figures 3 and 4 are an overview of transmission antennas using a current speed control method (PSRC) and an antenna speed control method (PARC), respectively; Figure 5 is a flow diagram of a control signal transmission method of a multiple antenna system in accordance with the present invention; and Figure 6 is a block diagram illustrating an apparatus for generating and discriminating the control signals in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, wherein the reference numbers designate identical or corresponding parts throughout the view, the present invention will be described. The present invention provides in one example a novel method for transmitting data at very high data rates using a MIMO system in, for example, an HS-DPA system. The MIMO system includes a plurality of transmit antennas and a plurality of receiver antennas. further, in the MIMO system, the control information such as a modulation method, a code rate, the number of OVSF codes (orthogonal variable spreading factor), and an error re-transmission scheme can be set differently for each transmission current. To achieve this, the MIMO system transmission end according to the present invention transmits control signals for the plurality of transmission streams to inform the receiving end of the MIMO system about the control information used at the transmission end. In more detail, Figure 1 is an overview illustrating an example of a transmission end of the MIMO system. As shown, the transmission end includes a demultiplexer 10, a symbol coding unit 11, a channelization coding unit 12, a symbol combination unit 13, a scrambling unit 14, and a transmission antenna Tx1 to Txn . In this example the demultiplexer 10 branches a data stream to the plurality of transmit antennas Tx1 to Txn, and the symbol coding unit 11 sequentially performs the channel coding, interleaving and mapping operations to generate a symbol, and subsequently multiplexes the generated symbol. In addition, the channelization coding unit 12 assigns the channelization codes C1 ~ Cn to the plurality of symbols that exit the symbol coding unit 11. The assigned symbols-channelization code are then combined in the symbol combination unit 13, are scattered in the scrambling unit 14, and subsequently transferred to the plurality of transmit antennas Tx1 ~ Txn. For example, assuming, that a data stream input to the demultiplexer 10 includes 1920 bits. The demultiplexer 10 then segments the input data stream into two data blocks including 960 bits each, for example. The two 960 bit data are then processed by the symbol combination unit 11 to perform coding, interleaving and mapping. In more detail, each of the 960 bits is encoded based on the coding scheme for that particular antenna (assume a turbo encoding of 1/2 is used for the first Tx1 antenna and a turbo encoding of 1/3 is used for the Txn antenna). Thus, in this example, the first 960 bits can be encoded in 1920 bits (ie, a turbo encoding of 1/2) and the 960 bits of Txn can be encoded in 2880 bits (ie, a turbo encoding of 1 / 3). The two coded data blocks are then stored in an interleaver for mapping. Assuming quadrature amplitude modulation (QAM) is used for the Tx1 antenna and quadrature phase shift modulation (QPSK) is used for the Txn antenna. Subsequently, the first 1920 encoded bits will be mapped into 480 symbols (ie, 16QAM maps 4 bits for a symbol and thus 1920 coded bits will be mapped into 480 symbols). The 2880 bits of Txn will be mapped into 1440 symbols (that is, QPSK maps 2 bits into a symbol and thus 2880 encoded bits will be mapped into 1440 symbols). The two separate coded and modulated data blocks are then processed by the channelization coding unit 12. In the current HS-DPA, one frame includes three slots and the spreading factor is set to 16. Subsequently, the number of symbols per frame with a code is 480 symbols. Therefore, the first 480 symbols are transmitted with a code and the second 1440 symbols are transmitted with 3 multi-codes. The channelization coding unit 12 uses a variety of spreading codes such as OVSF (orthogonal variable spreading factor) codes to spread the data blocks to discriminate between the different channels of each antenna. In addition, the receiving side shown in Figure 2 of! MIMO system has the same spreading codes and despaces the received data using the same codes. In this way, the MIMO system is able to select a different MCS (modulation and coding set) for each respective antenna to increase the performance of the system. The scattered symbols are then combined in the symbol combination unit 13 and randomized in the scrambling unit 14 before being transmitted from the respective antennas Tx1 and Txn. Note that the scrambling codes are used to discriminate cell regions (for example, received information is received from node B A instead of node B B, for example). The receiving operation inverts the transmission operation to finally obtain the data initially transmitted. In more detail, with reference to Figure 2, the receiver side includes a least mean square error detector (MMSE) 21, a despread unit 22, a multiplexer (MUX) 23, a current detection unit 24, a unit signal re-construction 25 and a signal assembly unit 26. An interference signal removal unit 20 is also included that removes a substream (interference signal), which has been reconstructed in the detection unit current 24 from a receiving signal by using a plurality of regulators. In addition, the MMSE detector 21 detects a signal having the signal-to-noise plus interference (SINR) ratio between the removed interference signals and performs a linear MMSE conversion in the signal. An output of the MMSE detector 21 is de-spreading in the de-spreading unit 22 and subsequently multiplexed in the multiplexer 23. In addition, the current detection unit 24 detects a transmission symbol from a signal emitted from the multiplexer 23 and performs deviation operations. mapping and de-interleaving in the detected symbol to detect a first sub-stream. Subsequently, the signal reconstruction unit 25 reconstructs the first sub-current detected by the current detection unit 24 in a form of receiving signal and outputs it to the interference removal unit 20. To minimize the mutual influence between the symbols, the interference removal unit 20 removes a first detected signal component (reconstructed signal) from the receiving signal previously stored in the regulator and subsequently the detected signal-signal component to the MMSE detector 21. Subsequently, the MMSE detector 21 MMSE-linear converts the signal that has the greater SINR between the removed signals-reconstructed signal. An emission of the MMSE detector 20 is input to the current detection unit 24 through the de-spreading unit 22 and the muitiplexer 23, and the current detection unit 24 detects a second sub-current. The signal reconstruction unit 25 then reconstructs the second substream, which has been detected by the current detection unit 24, and outputs it to the reference removal unit 20.

Subsequently, the interference removal unit 20 removes the reconstructed signal from a signal previously stored in the regulator and outputs it to the MMSE detector 20. Hereinafter, by repeatedly performing the operations described above, the current detection unit 24 detects sequentially sub-currents. After all sub-currents are detected by the current sensing unit 24, the signal assembly unit 26 assembles the plurality of detected sub-streams to form a data stream. In this way, in the MIMO system, in order to transfer sequentially generated data independently through each transmission antenna, the vector coding is performed in each transmission data. Mainly, the sequentially generated data passes through parallel and serial circuits (demultiplexer and symbol coding units) so that each antenna can transfer the data in parallel. In addition, since the quality of the channels of each transmission antenna is potentially different, the modulation and coding set (MCS) and the number of OVSF codes can be set differently for each antenna. In other words, the transmitting end may determine the channel states of different antennas by receiving quality information from the receiving end channel. Based on the received channel quality information, the base station (transmit end) applies a QAM scheme (quadrature amplitude modulation) or many OVSF codes, for example, to transmit data of a high code rate through of the transmission antenna with a good channel state, and applies a QPSK (quadrature phase shift keying modulation) or a small number of OVSF codes, for example, to transmit data of a low code rate. Furthermore, as noted above, when the mobile terminal detects a signal transmitted from a specific transmission antenna, the terminal treats a signal transmitted from a different transmission antenna as an interference signal and detects the signals having a higher SINR first as transmitted from each transmission antenna (mainly, in the order of magnitude of SINR). For this purpose, the terminal calculates each vector of the weight of the receiving antennas for the signal transmitted from each transmission antenna and at the same time uses an SIC (successive interference cancellation) method to remove an influence of the first detected signal. Since the base station sets different MCS schemes and the number of OVSF codes used for each transmit antenna are based on a downlink channel state, the present invention also provides useful downlink control information corresponding to each MCS scheme established differently, OVSF codes, retransmission schemes, etc. That is, the control information on each data stream separately is transmitted to the terminal.

In greater detail, according to the present invention, the base station assigns a plurality of high-speed shared control channels (HS-SCCH), for example, to each HSDPA user, and each user (eg, terminal, UE). , subscriber unit, etc.) simultaneously monitors four HS-SCCHs, for example. From here on, if the transmission of data to a user is required, the base station adds a UE ID to one of the assigned HS-SCCHs and transmits a control signal in the assigned HS-SCCH so that the terminal can recognize that the HS-SCCH is for her. As noted above, the MIMO system according to the present invention is capable of differently setting the MCS scheme, the number of OVSF codes used, the retransmission scheme to be used etc. This can be achieved using an antenna speed control (PARC) method or using a current speed control (PSRC) method, which is a general concept of PARC. Figures 3 and 4 illustrate examples of the PSRC and PARC methods, respectively. As shown in Figure 3, a current 40 is applied with weight values w1 and w2 of a weight unit 46 and is transmitted by means of the antennas 42 and 44. That is, the same current is transmitted for each antenna, but multiply with different weight values. A next stream (not shown) is then processed in a similar manner. As shown in Figure 4, in the PARC method, currents 50 and 52 are multiplied with codes from a coding unit 54 and transmitted by means of antennas 56 and 58. Note, that the codes may be the same codes or different codes, which will be discussed in more detail later. In addition, the MIMO system according to the present invention implements in one example, an error correction code (CRC) added to a plurality of packet streams transmitted through each antenna or where a CRC is transmitted through several antennas See, for example, application of E.U.A. Serial No. 10 / 845,086 filed on May 14, 2004, which as noted above is incorporated by reference in its entirety. In addition, since there is a plurality of parallel data streams transmitted in the MIMO system, the present invention in one example applies different spreading codes, such as different spreading codes OVSF, to each control data stream corresponding to the plurality of parallel data streams. In this way, the terminal, UE, subscriber unit, etc., is capable of discriminating the different control signals. In more detail, Figure 5 is a flow chart illustrating a method for transmitting control signals that correspond to different data streams. As shown, the transmit end of the MIMO system (eg, base station) first allocates a shared control channel (HS-SCCH) for each separate data stream (step S10 and In addition, the transmit end (base station) it discriminates the respective control signals (eg, the respective HS-SSCHs) using different OVSF codes, for example (step S12) Subsequently, the transmitting end transmits the separate control signals to the terminal through the antenna transmission (step S13) In this way, the transmitting end transmits independent parallel downlink control signals including control information over the data streams transmitted from the multiple antennas.Figure 6 illustrates an apparatus for performing the steps shown in Figure 5. As shown in Figure 6, the transmission end of the MIMO system includes a control signal generator 60 to generate / assign r the required control signals, a unit for discriminating 62 for discriminating the control signals, and a demultiplexing unit 64 for distributing the discriminated control signals. Note that the demultiplexing unit 64 can occur before the discrimination unit 62. The different methods for discriminating the control signals are discussed in more detail below. Thus, in accordance with the present invention, the base station transmits information about each transmit antenna and discriminates each control signal (eg, HS-SCCH) using different spreading codes such as OVSF codes. For example, a control signal corresponding to antenna # 1 is discriminated using a # 1 code of OVSF, a control signal corresponding to antenna # 2 is discriminated using another code # 2 of OVSF, etc. Furthermore, it is particularly useful that the present invention uses different OVSF codes to distinguish the control signals from each other, since this method provides downward compatibility with mobile terminals configured for HS-DPA using a single antenna. In more detail, in accordance with the present invention each transmission antenna has a corresponding control signal so that the parallel control signals are transmitted. This differs from a serial control signal where the information on each antenna can be transmitted in a serial control signal in different time slots, for example. However, assume that a UE1 is configured for an HS-DPA system that uses a single transmit antenna and an UE2 is configured for a system that uses a MIMO system. In this example, UE1 may not be able to discriminate what a portion of a single stream in series is to it without changing the UE1 software. That is, UE1 can be reconfigured and may not be compatible with the HS-DPA system using a MIMO transmitter. On the contrary, the present invention uses in a useful way parallel transmitted control signals, which may allow UE1 to be compatible with a system using a MIMO transmitter. For example, the base station may insert a UE ID into the control signal to inform UE1 that the control signal is for it.

In the previous example, different OVSF codes are used, however, the present invention also applies a method using code reuse to discriminate the control signals (or control channels) by means of currents (antennas). A more detailed explanation of the methods of discrimination will now be given. The discrimination of different control signals using different OVSF codes, transmission diversity or weight values. First, in the PARC method (see Figure 4), if the number of transmission streams to be transmitted to a terminal (UE) is' C, the base station assigns a number 'C' of the control channels (HS-). SCCH) to transmit the 'C number of transmission currents. In addition, the HS-SCCH signals assigned to the different data streams are discriminated by different OVSF codes respectively. That is, the base station multiplies different OVSF codes with HS-SCCH, and subsequently the HS-SCCHs are transmitted. In one example, each transmitted HS-SCCH signal is transmitted from a transmit antenna separately so that the ratio between the HS-SCCH signals and the transmit antennas is 1: 1. If the number of the transmit antennas is greater than the number of transmission streams (i.e., M> C), the base station transmits the HS-SCCH signals through a 'C number of transmit antennas selected from the number 'M' of the transmission antennas.

In addition, HS-SCCHs that discriminate by different codes can be transmitted by transmission diversity for more efficient transmission. Furthermore, for the PSRC method where the weight vectors are multiplied by the transmission currents (see figure 3), which are subsequently distributed to several hundred, the base station multiplies different OVSF codes by the HS-SCCH signals and subsequently transmit the control signals. Alternatively, the transmitting end may multiply the weight vectors and the same OVSF codes with the HS-SCCHs more than the different OVSF codes and subsequently transmit the control signals. In addition, when the control signals are discriminated using different OVSF codes, it is possible that the number of downlink OVSF codes available is insufficient. In this example, the OVSF codes of a secondary set of scrambling codes, as well as the OVSF codes of a set of primary scrambling codes may be used. Thus, in this first example, different OVSF codes can be used to discriminate different control signals in the PARC method. For the PSRC method, different OVSF codes or weight values can be used to discriminate different control signals.

Code reuse transmission First, in the PARC method (see Figure 4), to transmit the 'C' number of the HS-SCCH signals, a code reuse transmission may be used to transmit the data stream. In this example, the same OVSF code is multiplied by the separate control signals and subsequently transmitted through each different antenna. Note that this differs from the previous examples where different OVSF codes are used. Subsequently, the terminal discriminates the control signals using a difference of fading channels that each current suffers. In addition, since there is an interference component in the received current due to a current transmitted from another antenna, the terminal is able to detect the transmission current using a successive interference cancellation method (SIC). In addition, if the weight vectors are multiplied by the transmission current as in the PSRC method (see Figure 3), and then distributed to several antennas, the base station (transmit end) multiplies the same OVSF code with HS-SCCH signals and transmit signals. In an alternative example, the transmitting end can multiply the weight vectors with the HS-SCCH signals rather than using the OVSF codes and subsequently transmits the signals. When the weight vectors are multiplied by the HS-SCCHs and subsequently transmitted, even when the same OVSF code is used, if the weight vectors are orthogonal, the terminal can receive transmission currents without interference. As already described, the method for transmitting a discharge control signal in a mobile communication system using multiple antennas of the present invention has the following advantages. That is, for example, by maintaining the existence of the shared control channels (HS-SCCH) rather than adding new separate control channels, a downward compatibility of the previous communication systems is achieved. Furthermore, if the data streams transmitted to each antenna is made by means of a packet or several packets, the present invention can be applied. This invention can be conveniently implemented using a conventional general-purpose digital computer or a microprocessor programmed in accordance with the teachings of the present specification, as will also be apparent to those skilled in the art of computers. An appropriate software coding can be easily prepared by the expert programmers based on the teachings of the description herein, as will be apparent to those skilled in the art of software. The invention can also be implemented by preparing specific application integrated circuits or by interconnecting an appropriate network of conventional component circuits, as will be apparent to those skilled in the art.

The present invention includes a computer program product that is a storage medium that includes instructions that can be used to program a computer to perform a method of the invention. The storage medium may include, but is not limited to, any type of disc including portable discs, optical discs, CD-ROMs, and magneto-optical discs, ROM, RAM, EPROM, EEPROM, magnetic or optical cards, or any type of suitable medium for storing electronic instructions. The above embodiments and advantages are merely exemplary and are not intended to be construed as limiting the present invention. The teaching of the present can easily be applied to other types of apparatus. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications and variations will be apparent to those skilled in the art.

Claims (26)

NOVELTY OF THE INVENTION CLAIMS

1. - A communication method in a multiple input multiple output (MIMO) system, comprising: transmitting independent parallel downlink control signals that include control information for each data stream; and transmit the data streams.

2. The method according to claim 1, further characterized in that the control information corresponds to at least one modulation method used to modulate the data streams, a number of OVSF codes (orthogonal variable spreading factor) used. for spreading the data streams, and a retransmission scheme used to request retransmissions of at least one of the data streams.

3. The method according to claim 1, further characterized in that the control signals are transmitted in respective high-speed shared control channels (HS-SCCH).

4. The method according to claim 1, further characterized in that the number of independent parallel downlink control signals equalizes a number of the data streams so that the ratio of the data streams to the control signals of Independent parallel downlink is 1: 1.

5. - The method according to claim 1, further characterized in that transmitting the independent parallel downlink control signals comprises: discriminating each control signal using different spreading codes.

6. The method according to claim 5, further characterized in that the spreading codes comprise OVSF codes (orthogonal variable spreading factor).

7. The method according to claim 6, further characterized in that transmitting the independent parallel downlink control signals further comprises: transmitting each control signal using transmission diversity.

8. The method according to claim 1, further characterized in that transmitting the independent parallel downlink control signals comprises: discriminating each control signal using a code reuse transmission

9. The method according to claim 8 , further characterized in that the code reuse transmission uses the same OVSF code (orthogonal variable spreading factor).

10. The method according to claim 1, further characterized in that transmitting the independent parallel downlink control signals comprises: discriminating each control signal using a separate weight vector.

11. - The method according to claim 1, further characterized in that transmitting the independent parallel downlink control signals comprises: discriminating each control signal using the same spreading code and using different weight values applied to the control signals.

12. The method according to claim 11, further characterized in that the same spreading code comprises an OVSF code (orthogonal variable spreading factor).

13. The method according to claim 1, further characterized in that if a number "C" of control signals to be transmitted is less than a number "M" of multiple transmit antennas of the MIMO system, the control signals are transmit by means of a "C" number of the selected transmit antennas of the number "M" of multiple transmit antennas.

14.- Multiple input multiple output communication system (MIMO) having multiple before transmission, comprising: a discrimination unit configured to discriminate independent parallel downlink control signals includes control information for each data stream transmitted by multiple antennas.

15. The system according to claim 14, further characterized in that the control information corresponds to at least one of a modulation method used to modulate the data streams, a number of OVSF codes (orthogonal variable spreading factor) used to scatter the data streams, and a retransmission scheme used to request re-transmission of at least one of the data streams.

16. The system according to claim 14, further characterized in that the control signals are transmitted in respective high-speed shared control channels (HS-SCCH).

17. The system according to claim 14, further characterized in that a number of independent parallel downlink control signals equalize a number of data streams so that a ratio of the data streams to the link control signals independent parallel descending is 1: 1.

18- The system according to claim 14, further characterized in that the discrimination unit discriminates each control signal using different spreading codes.

19. The system according to claim 18, further characterized in that the spreading codes comprise OVSF codes (orthogonal variable spreading factor).

20. The system according to claim 19, further characterized in that each control signal is transmitted using transmission diversity.

21. The system according to claim 14, further characterized in that the discrimination unit discriminates each control signal using a code reuse transmission.

22. - The system according to claim 21, further characterized in that the code reuse transmission uses the same OVSF code (orthogonal variable spreading factor).

23. The system according to claim 14, further characterized in that the discrimination unit discriminates each control signal using a separate weight vector.

24. The system according to claim 14, further characterized in that the discrimination unit discriminates each control signal using the same spreading code and using different weight values applied to the control signals.

25. The method according to claim 24, further characterized in that the same spreading code comprises an OVSF code (orthogonal variable spreading factor).

26. The system according to claim 14, further characterized in that if a number "C" of the control signals to be transmitted is less than a number "M" of multiple antennas, the control signals are transmitted by means of a "C" number of antennas selected from the "M" number of multiple antennas.