JP2012231340A - Radio communication method, transmission side communication device, and reception side communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to improve communication quality before performing negotiation of communication capability in a radio communication system where communication devices compliant/noncompliant to a MIMO transmission system are mixed.SOLUTION: A base station BS having a plurality of transmission antennas 101 and 102 comprises: a transmission part 11 performing transmission to a radio terminal MS having one or a plurality of reception antennas, through the transmission antennas 101 and 102; and a control part 30 which performs control to transmit by an STBC system before negotiation of communication capability ends in a connection sequence with the radio terminal MS, and performs control to transmit by a transmission system depending on a result of the negotiation after the negotiation of the communication capability has ended.

Description

  The present invention relates to a radio communication method, a transmission side communication device, and a reception side communication device of a radio communication system.

  In recent years, in a wireless communication system, various multiplexing techniques have been realized in order to improve frequency use efficiency and communication quality.

  For example, a plurality of data signals are transmitted through a plurality of transmission antennas using the same time / frequency resource, and the plurality of data signals are received through a plurality of reception antennas, and separated into data signals. A multiple-input / multiple-output (MIMO) transmission method is known.

  The MIMO transmission method uses a logical transmission path (referred to as a “stream”) that is spatially divided between a transmission side and a reception side by using different transmission antennas or different transmission directivities for each data signal. A plurality of are formed. Such a stream may be referred to as a “layer”.

  Also, for example, XGP1.0, which is the current standard of next generation PHS (XGP), is not compatible with the MIMO transmission method, but XGP2.0 with improved communication capability over XGP1.0 is compatible with the MIMO transmission method. (See Non-Patent Document 1).

ARIB STD-T95 Version 1.3

  By the way, in the transition period from the XGP 1.0 standard to the XGP 2.0 standard, communication devices (base stations or wireless terminals) that support the MIMO transmission method and communication devices that do not support the MIMO transmission method are mixed. .

  For example, since a wireless terminal configured in accordance with the XGP 1.0 standard has only one antenna, it cannot perform transmission / reception using the MIMO transmission scheme even if the base station supports the MIMO transmission scheme.

  Therefore, before the communication capability is negotiated in the connection sequence between the base station and the wireless terminal, single input / single output (SISO) transmission in which each of the transmission side and the reception side uses a single antenna. It is conceivable to apply the method.

  However, such a method has a problem that the communication quality before the negotiation of the communication capability is low.

  Such a problem may occur not only in XGP but also in all wireless communication systems in which communication devices that support / do not support the MIMO transmission scheme are mixed.

  Therefore, the present invention provides a wireless communication method, a transmission side communication device, and a reception side communication capable of improving communication quality before negotiation of communication capability in a wireless communication system in which communication devices that support or do not support the MIMO transmission scheme are mixed. An object is to provide an apparatus.

  In order to solve the above-described problems, the present invention has the following features.

  First, the wireless communication method according to the present invention is characterized in that a transmission side communication device (for example, a base station BS) having a plurality of transmission antennas and a reception side communication device (for example, a wireless communication device) having one or a plurality of reception antennas. A wireless communication method for performing wireless communication with a terminal MS), and a negotiation process (for example, steps S104 and S105) in which communication capability is negotiated in a connection sequence between the transmitting communication device and the receiving communication device. ) And the first transmission / reception step (for example, performing transmission / reception between the transmission-side communication device and the reception-side communication device by a predetermined transmission method before the negotiation of the communication capability is completed) Steps S102 to S105) and after the negotiation of the communication capability is completed, A second transmission / reception step (steps S106 to S114) for performing transmission / reception between the transmission-side communication device and the reception-side communication device by a transmission method according to the above-described specific transmission method, The gist of the present invention is a transmission diversity system using a plurality of transmission antennas, which is applicable even if there is only one reception antenna of the reception side communication apparatus. Here, the transmission antenna is not limited to an antenna dedicated to transmission, but may be an antenna that is also used for reception. Similarly, the reception antenna is not limited to a reception-dedicated antenna but may be an antenna that is also used for transmission.

  According to such a wireless communication method, the transmission diversity method using a plurality of transmission antennas before the negotiation of communication capability is completed, even if the reception side communication apparatus has one reception antenna, is applicable. Send and receive in a possible manner.

  Thus, even when the receiving communication apparatus has one receiving antenna (that is, when the MIMO transmission scheme is not supported), the transmitting communication apparatus has a plurality of transmitting antennas (that is, MIMO transmission). When the communication method is compatible), the communication quality can be improved by the diversity effect even before the communication capability negotiation is completed.

  Therefore, according to the above-described feature, it is possible to improve communication quality before performing communication capability negotiation in a wireless communication system in which communication apparatuses that support or do not support the MIMO transmission scheme are mixed.

  Another feature of the wireless communication method according to the present invention is that, in the above-described feature, when the receiving-side communication device has a plurality of receiving antennas, the second transmission / reception step includes the plurality of transmitting antennas and the plurality of transmitting antennas. The gist is to perform transmission and reception by a MIMO transmission method using a reception antenna of a book.

  In another aspect of the wireless communication method according to the present invention, in the above-described feature, the first transmission / reception step transmits / receives at least one of broadcast information, a connection request message, a connection request response message, or a communication capability negotiation message. The gist is to do.

  A feature of the transmission side communication apparatus according to the present invention is a transmission side communication apparatus (for example, a base station BS) having a plurality of transmission antennas, and one or a plurality of receptions are received via the plurality of transmission antennas. Before the communication capability negotiation is completed in the connection sequence between the transmission unit (for example, the transmission unit 11) that performs transmission to the reception-side communication device having the antenna and the reception-side communication device, the predetermined identification is performed. A control unit (for example, the control unit 30) that controls to perform transmission by the transmission method according to the result of negotiation after the negotiation of the communication capability is completed. And the specific transmission method is a transmission diversity method using the plurality of transmission antennas, wherein the reception antenna of the reception-side communication apparatus And summarized in that even one which is applicable manner.

  Another feature of the transmission-side communication device according to the present invention is that, in the above-described feature, when the reception-side communication device has a plurality of reception antennas, the control unit, after the negotiation of the communication capability is completed, The gist of the present invention is to control to perform transmission by a MIMO transmission method using the plurality of transmission antennas.

  A feature of the receiving communication device according to the present invention is a receiving communication device (for example, a radio terminal MS) having one or more receiving antennas, and a plurality of receiving communication devices are provided via the one or more receiving antennas. Before the negotiation of the communication capability is completed in the connection sequence between the receiving unit (for example, the receiving unit 45) that performs reception from the transmitting side communication device having the transmitting antenna and the transmitting side communication device. A control unit (for example, the control unit 60) that controls to perform reception by a specific transmission method, and controls to perform reception by a transmission method according to the result of the negotiation after the negotiation of the communication capability is completed. The specific transmission method is a transmission diversity method using the plurality of transmission antennas, and is received by the receiving communication apparatus. Antennas summarized in that a applicable method be one.

  Another feature of the receiving communication device according to the present invention is that, in the above-described feature, when the receiving communication device has a plurality of receiving antennas, the control unit, after the negotiation of the communication capability is completed, The gist is to perform control so as to perform reception by a MIMO transmission method using the plurality of reception antennas.

  Advantageous Effects of Invention According to the present invention, in a wireless communication system in which communication devices that support / do not support the MIMO transmission scheme, a wireless communication method, a transmission-side communication device, and a reception-side communication that can improve communication quality before performing communication capability negotiation. Equipment can be provided.

1 is an overall configuration diagram of a wireless communication system according to an embodiment of the present invention. It is a functional block diagram of the base station which concerns on embodiment of this invention. It is a functional block diagram of the radio | wireless terminal which concerns on embodiment of this invention. It is a functional block diagram of the transmission part and receiving part which concern on embodiment of this invention. It is a figure for demonstrating the operation | movement which performs the radio | wireless communication by a STBC transmission system between the transmission side which has two transmission antennas, and the reception side which has one reception antenna. It is a figure for demonstrating the operation | movement which performs the radio | wireless communication by a STBC transmission system between the transmission side which has one transmission antenna, and the reception side which has one reception antenna. It is a sequence diagram of the connection sequence of the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows schematic structure by the side of the transmission which concerns on the example of a change of embodiment.

  Referring to the drawings, (1) the overall configuration of a radio communication system, (2) each configuration of a base station and a radio terminal, (3) the operation of the radio communication system, and (4) the embodiment of the present invention. Effects and comparative examples will be described in the order of (5) other embodiments. In the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

  In the following, an example in which the present invention is applied to a wireless communication system based on the XGP standard will be described. However, the present invention is not limited to a wireless communication system based on the XGP standard, and is a communication apparatus that does or does not support a MIMO transmission scheme. It should be noted that the present invention can be applied to all wireless communication systems in which.

(1) Overall Configuration of Radio Communication System FIG. 1 is an overall configuration diagram of a radio communication system according to this embodiment.

  As shown in FIG. 1, the radio communication system according to the present embodiment includes a base station BS and radio terminals MS (MS # 1 and MS # 2) configured to perform radio communication with the base station BS. Have. The base station BS corresponds to the receiving communication device for the uplink, and corresponds to the transmitting communication device for the downlink. The radio terminal MS corresponds to the transmission side communication device for the uplink, and corresponds to the reception side communication device for the downlink.

  The base station BS is configured according to the XGP 2.0 standard. The base station BS has two antennas 101 and 102 used for transmission / reception of radio signals and corresponds to the MIMO transmission scheme. The base station BS may be configured according to the XGP 1.0 standard. In this case, the base station BS does not support the MIMO transmission scheme.

  The radio terminal MS # 1 is configured according to the XGP 2.0 standard. The radio terminal MS # 1 has two antennas 201 and 202 used for transmission / reception of radio signals and corresponds to the MIMO transmission scheme.

  The radio terminal MS # 2 is configured according to the XGP1.0 standard. The radio terminal MS # 2 has one antenna 201 used for transmission / reception of radio signals and does not support the MIMO transmission scheme.

  The base station BS broadcasts information indicating the communication capability of the base station BS via the BCCH that is a broadcast channel. Here, the communication capability includes whether or not the MIMO transmission method is supported. Further, the communication capability may include a corresponding retransmission control method (HARQ method) and a used frequency band in addition to the presence / absence of the MIMO transmission method.

  When the radio terminal MS receives broadcast information from a plurality of base stations BS, the radio terminal MS determines a communicable base station BS based on each broadcast information, and among the communicable base stations BS, a received signal at the radio terminal MS Synchronize with the one with the highest power. When there is a call or an incoming call after synchronizing with any of the base stations BS, a link channel allocation request (LCH Assignment request) is sent to the synchronization destination base station BS via the TCCH which is a timing correction channel. Request). A connection sequence is started by transmission of the LCH Assignment Request.

  In the connection sequence, the radio terminal MS includes information indicating the communication capability of the radio terminal MS in a link establishment request (Link Setup Request) and transmits the information to the base station BS via the dedicated control channel (ICCH). Here, the communication capability includes whether or not the MIMO transmission method is supported. Further, the communication capability may include a corresponding hybrid retransmission control scheme (HARQ scheme) and a used frequency band in addition to the presence / absence of the MIMO transmission scheme.

  The base station BS determines various methods to be used for wireless communication with the wireless terminal MS based on information indicating the communication capability of the wireless terminal MS included in the Link Setup Request. Then, the base station BS includes the determined content in a link establishment response (Link Setup Response) and transmits it to the radio terminal MS via the ICCH. The radio terminal MS performs subsequent radio communication according to the contents notified from the base station BS.

  As described above, the communication capability negotiation between the base station BS and the radio terminal MS is completed by transmitting and receiving the Link Setup Request and the Link Setup Response in the connection sequence.

  The base station BS and the radio terminal MS perform transmission / reception by a predetermined transmission method before the negotiation of the communication capability is completed. The specific transmission scheme is a transmission diversity scheme using a plurality of transmission antennas, and can be applied even if there is only one reception antenna on the reception side. Examples of such transmission schemes include a space-time coding (STBC) transmission scheme, a cyclic delay diversity (CDD) transmission scheme, and a frequency space block code (SFBC) transmission scheme.

  In the following embodiments, the base station BS and the radio terminal MS perform transmission / reception by the STBC transmission method before the negotiation of the communication capability is completed. However, in the transmission diversity method using a plurality of transmission antennas, Any other transmission method may be applied as long as the method is applicable even if there is only one receiving antenna on the receiving side. Details of the STBC transmission method will be described later.

  In the connection sequence, the radio terminal MS # 1 and the base station BS negotiate communication capabilities, and when it is confirmed that they are compatible with the MIMO transmission scheme, the wireless terminal MS # 1 and the base station BS thereafter perform transmission / reception using the MIMO transmission scheme. On the other hand, when the wireless terminal MS # 2 and the base station BS negotiate the communication capability in the connection sequence and it is confirmed that the wireless terminal MS # 2 does not support the MIMO transmission method, thereafter, Transmission / reception is performed by a transmission method other than the MIMO transmission method.

  The communication quality is improved by the diversity effect by applying the transmission diversity method as described above before the negotiation of the communication capability is completed. Thereby, for example, since the radio terminal MS # 1 and the base station BS can obtain good communication quality both before and after the negotiation is completed, the communication quality before the negotiation is completed becomes a bottleneck. Can be avoided.

(2) Configuration of Base Station and Radio Terminal Next, the configuration of the base station BS will be described. FIG. 2 is a functional block diagram of the base station BS.

  As illustrated in FIG. 2, the base station BS includes antennas 101 and 102, a wireless communication unit 10, a network communication unit 18, a storage unit 20, and a control unit 30.

  Antennas 101 and 102 are used for transmitting and receiving radio signals. The wireless communication unit 10 is configured to perform wireless communication via the antennas 101 and 102. The radio communication unit 10 performs up-conversion and amplification of the baseband signal input from the control unit 30 and outputs the radio signal from the antennas 101 and 102, and the reception signal input from the antennas 101 and 102. And a receiving unit 15 that outputs a baseband signal to the control unit 30 after performing amplification and down-conversion.

  The network communication unit 18 is connected to a communication network and performs communication with the communication network side. The storage unit 20 is configured using, for example, a memory, and stores various types of information used for control by the control unit 30 and the like. The control unit 30 is configured using, for example, a CPU, and controls various functions of the base station BS.

  Next, the configuration of the wireless terminal MS will be described. Since the radio terminals MS # 1 and MS # 2 have the same configuration except for the number of antennas, the configuration of the radio terminal MS # 1 will be described here.

  FIG. 3 is a functional block diagram of the radio terminal MS # 1.

  As illustrated in FIG. 3, the radio terminal MS # 1 includes antennas 201 and 202, a radio communication unit 40, a storage unit 50, and a control unit 60.

  Antennas 201 and 202 are used for transmitting and receiving radio signals. The wireless communication unit 40 is configured to perform wireless communication via the antennas 201 and 202. The radio communication unit 40 performs up-conversion and amplification of the baseband signal input from the control unit 60 and outputs a radio signal from the antennas 201 and 202, and a reception signal input from the antennas 201 and 202. And a receiving unit 45 that outputs the baseband signal to the control unit 60 after performing amplification and down-conversion.

  The storage unit 50 is configured using, for example, a memory, and stores various types of information used for control by the control unit 60 and the like. The control unit 60 is configured using a CPU, for example, and controls various functions of the wireless terminal MS # 1.

  Next, the configurations of the transmitting unit and the receiving unit of the base station BS and the radio terminal MS # 1 will be described. The transmission unit 41 of the radio terminal MS # 1 is configured in the same manner as the transmission unit 11 of the base station BS, and the reception unit 45 of the radio terminal MS # 1 is configured in the same manner as the reception unit 15 of the base station BS. Each configuration of the transmission unit 11 and the reception unit 15 will be described.

  FIG. 4 is a functional block diagram of the transmission unit 11 and the reception unit 15. In FIG. 4, a MAC (Media Access Control) / PHY (Physical) IF unit 31, a layer control unit 32, and a MAC / PHY IF unit 33 are provided in the control unit 30. Each of the transmission unit 11 and the reception unit 15 is configured to be able to execute signal processing according to the MIMO transmission scheme and signal processing according to the STBC transmission scheme. Each of the transmission unit 11 and the reception unit 15 is configured to perform signal processing according to an orthogonal wave frequency division multiplexing (OFDM) system.

  As illustrated in FIG. 4, the transmission unit 11 includes a cyclic redundancy check (CRC) addition unit 111 to which an output of the MAC / PHY IF unit 31 is input, and a scrambling unit 112 to which an output of the CRC addition unit 111 is input. The channel encoder 113 to which the output of the scrambling unit 112 is input, the bit interleaving unit 114 to which the output of the channel encoder 113 is input, and the primary modulation unit to which the output of the bit interleaving unit 114 is input 115. The CRC adding unit 111, the scrambling unit 112, the channel encoding unit 113, the bit interleaving unit 114, and the primary modulation unit 115 constitute a data encoding unit.

  The CRC adding unit 111 is configured to add an error detection bit to data in order to determine whether or not the data has an error on the receiving side. The scrambling unit 112 is configured to perform encryption and bit balancing. The channel encoding unit 113 is configured to add an error correction code in order to increase error tolerance. The bit interleaving unit 114 is configured to convert a burst error generated by fading into a random error in order to improve error correction capability. The primary modulation unit 115 is configured to change bit data to symbol data. In the OFDM system, converting bit data into symbol data is defined as primary modulation, and converting from the frequency domain to the time domain is defined as secondary modulation. In the case of a MIMO scheme that requires a plurality of streams such as SM-MIMO, a data encoding unit is provided for a plurality of streams.

  Further, the transmission unit 11 includes a known signal generation unit 116, a primary modulation unit 117 to which an output of the known signal generation unit 116 is input, a boosting unit 118 to which an output of the primary modulation unit 117 is input, and guard symbol modulation. Unit 119, combining unit 120 to which the outputs of primary modulation unit 115, boosting unit 118, and guard symbol modulation unit 119 are input, layer mapping unit 121 to which the output of combining unit 120 is input, and layer mapping Transmission precoding unit 122 to which the output of unit 121 is input, resource mapping unit 123 to which the output of transmission precoding unit 122 is input, and inverse fast Fourier transform (IFFT) unit to which the output of resource mapping unit 123 is input 124 and guard interval (GI) insertion to which the output of the IFFT unit 124 is input. Unit 125, a finite impulse response (FIR) filter unit 126 to which the output of the GI insertion unit 125 is input, a digital / analog conversion unit (DAC) 127 to which the output of the FIR filter unit 126 is input, and the output of the DAC 127 And an input transmission radio frequency (RF) processing unit 128.

  The known signal generator 116 is configured to generate a pilot / training signal. Since the pilot / training signal is used for channel estimation / RSSI / timing synchronization on the reception side, it is a signal (known signal) prepared in advance on the reception side. The primary modulation unit 117 is configured to perform primary modulation of the pilot / training signal. The boosting unit 118 is configured to increase the power of the pilot / training signal higher than the data power in a weak electric field in order to improve channel estimation accuracy and increase error tolerance. The guard symbol modulation unit 119 is basically configured to modulate a guard symbol used as a symbol that is not allocated in data / pilot / training. The combining unit 120 is configured to combine data, training, and pilot. The layer mapping unit 121 is configured to determine which layer data, training, and pilot are mapped to. The layer mapping unit 121 also has a function as an STBC encoding unit (STBC Enc) described later. The transmission precoding unit 122 is configured to perform weighting processing when a transmission weight is applied as in SVD-MIMO. The resource mapping unit 123 is configured to map to an allocated area (PRU in XGP). The IFFT unit 124 is configured to transform from the frequency domain to the time domain by performing inverse Fourier transform. The GI insertion unit 125 is configured to copy and add a part of the symbol time in order to obtain multipath (delayed wave) tolerance. The FIR filter unit 126 is configured to apply a filter to cut off unused frequency bands. The DAC 127 is configured to convert a digital signal into an analog signal. The transmission RF processing unit 128 is configured to up-convert an analog signal and transmit it at a corresponding radio frequency.

  Note that the layer control unit 32 is configured to perform layer control, and is configured to instruct to which layer training and pilot are allocated during MIMO transmission.

  Next, the configuration of the receiving unit 15 will be described. As shown in FIG. 4, the reception unit 15 includes a reception RF processing unit 151, an analog / digital conversion unit (ADC) 152 to which the output of the reception RF processing unit 151 is input, and an FIR filter to which the output of the ADC 152 is input. 153, the GI removal unit 154 to which the output of the FIR filter unit 153 is input, the fast Fourier transform (FFT) unit 155 to which the output of the GI removal unit 154 is input, and the data to which the output of the FFT unit 155 is input. A subchannelization unit 156, a reference pilot / training symbol holding unit 157, a channel estimation unit 158 to which outputs of the desubchannelization unit 156 and the reference pilot / training symbol holding unit 157 are input, and a desubchannelization Unit 156 and the channel estimator 158 are input. And a MIMO decoding unit (channel equalizer) 159 which it is.

  The reception RF processing unit 151 is configured to down-convert the received radio signal and convert it to a baseband frequency. The ADC 152 is configured to convert an analog signal into a digital signal. The FIR filter unit 153 is configured to apply a filter to cut off unused frequency bands. The GI removal unit 154 is configured to remove the GI. The FFT unit 155 is configured to convert a time signal into a frequency signal. The desubchannelization unit 156 is configured to extract for each PRU in XGP. The reference pilot / training symbol holding unit 157 is configured to hold a reference pilot / training symbol in advance. Channel estimation section 158 is configured to perform data symbol channel estimation from the received training / pilot signal and known training / pilot signal. Note that the channel estimation unit 158 is configured to receive information from the layer control unit 32 because it is necessary to know to which layer training or pilot is assigned in the case of MIMO transmission. The MIMO decoding unit 159 is configured to separate these signals in this block and equalize the signals because different signals are combined from the respective transmitting antennas and received in the MIMO transmission. The MIMO decoding unit 159 also has a function as an STBC decoding unit (STBC Dec) described later.

  Furthermore, the receiving unit 15 receives the output of the symbol demapping unit 160 to which the output of the MIMO decoding unit 159 is input, the debit interleaving unit 161 to which the output of the symbol demapping unit 160 is input, and the output of the debit interleaving unit 161. It includes an input channel decoding unit 162, a descrambling unit 163 to which an output of the channel decoding unit 162 is input, and a CRC unit 164 to which an output of the descrambling unit 163 is input.

  The symbol demapping unit 160 is configured to convert a symbol into bits (hard decision bit / soft decision bit). The debit interleaving unit 161 is configured to perform the work of returning to the original on the receiving side since bit interleaving is applied on the transmitting side. Since the channel decoding unit 162 has applied the error correction code on the transmission side, it is configured to perform error correction decoding on the reception side. Since the descrambling unit 163 scrambles on the transmission side, the descrambling unit 163 is configured to perform a restoration operation on the reception side. The CRC unit 164 is configured to calculate a CRC and detect whether there is an error in this data. The output of the CRC unit 164 is input to the MAC / PHY IF unit 33.

(3) Operation of Radio Communication System Next, the operation of the radio communication system according to the present embodiment will be described. FIG. 5 is a diagram for explaining an operation of performing wireless communication by the STBC transmission method between a transmission side having two transmission antennas and a reception side having one reception antenna. The transmission side is either the base station BS or the radio terminal MS, and the reception side is either the base station BS or the radio terminal MS.

As shown in FIG. 5, the STBC encoding unit (STBC Enc) on the transmission side receives input transmission signals S ₁ and S ₂ , S ₁ and S ₂ ^* for transmission antenna # ₁ , and transmission antenna # 2. Encodes to S ₂ , -S ₁ ^* and transmits. Here, “ ^* ” represents a complex conjugate. The propagation path characteristics from the transmission antenna # 1 to the reception antenna are H ₁ and H ₃ , and the propagation path characteristics from the transmission antenna # 2 to the reception antenna are H ₂ and H ₄ .

Since the received signals Y ₁ and Y ₂ are combined signals of the signal output from the transmission antenna # 1 and the signal output from the transmission antenna # 2, it can be expressed by the following equation.

Y ₁ = H ₁・ S ₁ + H ₂・ S ₂ (Formula 1)
Y ₂ = H ₃・ S ₂ ^* -H ₄・ S ₁ ^* (Formula 2)
Here, Equation 2 can be modified as follows.

Y ₂ ^* =-H ₄ ^*・ S ₁ + H ₃ ^*・ S ₂ (Formula 3)
When Expression 1 and Expression 3 are changed to determinants, they can be expressed as follows.

S₁, S₂を求める為には、式４の両辺から、

To find S ₁ and S ₂ , from both sides of Equation 4,

の逆行列を求めればよい。

The inverse matrix of

このように、受信アンテナ１本でも、ＳＴＢＣ復号部（ＳＴＢＣ Dec）は復号を行うことができ、送信ダイバーシティの効果が得られる。

Thus, even with one receiving antenna, the STBC decoding unit (STBC Dec) can perform decoding, and the effect of transmission diversity can be obtained.

In general literature, H ₁ = H _{3 and} H ₂ = H ₄ are described. However, in an actual environment, different propagation path characteristics are used, and therefore, different parameters are described. When H ₁ = H _{3 and} H ₂ = H ₄ , full diversity can be obtained.

  As described above, in the present embodiment, the STBC transmission method is uniformly applied before the negotiation of the communication capability is completed. Therefore, the STBC transmission scheme is also applied to a combination of one transmitting antenna on the transmitting side (not supporting MIMO) and one receiving antenna on the receiving side (not supporting MIMO). If configured, the STBC transmission method can be applied to such a combination.

  FIG. 6 is a diagram for explaining an operation of performing wireless communication by the STBC transmission method between a transmission side having one transmission antenna and a reception side having one reception antenna. The transmission side is either the base station BS or the radio terminal MS, and the reception side is either the base station BS or the radio terminal MS.

As shown in FIG. 6, since there is only one transmitting antenna, it can be considered that H ₂ = H ₄ = 0 on the receiving side. Substituting into Equation 5,

となり、１本送信でも受信側では同じアルゴリズムにより計算することが可能である。

Thus, even the single transmission can be calculated by the same algorithm on the receiving side.

  Next, a connection sequence of the wireless communication system according to the present embodiment will be described. FIG. 7 is a sequence diagram of a connection sequence of the wireless communication system according to the present embodiment.

  As shown in FIG. 7, in step S101, the radio terminal MS is in an idle state or a sleep state. Here, it is assumed that a call is made by the radio terminal MS, and a connection sequence is started in the following.

  In step S102, the radio terminal MS transmits an LCH Assignment Request, which is a message for requesting LCH assignment, to the base station BS using the STBC transmission scheme via the TCCH. The base station BS receives the LCH Assignment Request.

  In step S103, the base station BS transmits an LCH Assignment Response, which is a response message to the LCH Assignment Request, via the SCCH to the radio terminal MS using the STBC transmission method. The radio terminal MS receives the LCH Assignment Response. Here, it is assumed that the radio terminal MS performs carrier sense for the assigned LCH and determines that the interference with the LCH is small and can be used for communication.

  In step S104, the radio terminal MS transmits a Link Setup Request, which is a message for notifying the start of communication, via the ICCH to the base station BS by the STBC transmission method. At that time, the radio terminal MS transmits the communication capability information and the terminal ID included in the Link Setup Request. The base station BS receives the Link Setup Request.

  In step S105, the base station BS transmits a Link Setup Response, which is a message for notifying a function (various methods) used in communication with the radio terminal MS, via the ICCH to the radio terminal MS using the STBC transmission method. To do. The radio terminal MS receives the Link Setup Response.

  In the present embodiment, step S104 and step S105 correspond to a negotiation process for negotiating communication capability. Steps S102 to S105 correspond to a first transmission / reception process in which transmission / reception is performed before the negotiation of communication capability is completed.

  In each step after step S106, transmission / reception is performed by a transmission method in accordance with the negotiation result of the communication capability. In other words, in this embodiment, each step after step S106 corresponds to a second transmission / reception process in which transmission / reception is performed after negotiation of communication capability is completed. For example, when both the radio terminal MS and the base station BS support the MIMO transmission scheme, transmission / reception is performed by the MIMO transmission scheme in each step after step S106. On the other hand, when at least one of the radio terminal MS and the base station BS does not support the MIMO transmission scheme, transmission / reception may be performed by the STBC transmission scheme in each step after step S106.

  In each step from step S106 to step S112, authentication information and key information used for communication are transmitted and received. Refer to Non-Patent Document 1 for details of each step.

  Thereafter, the radio terminal MS shifts to an active state (step S113), and the radio terminal MS and the base station BS communicate (step S114).

(4) Effect and Comparative Example of Embodiment As described above, according to the present embodiment, the base station BS and the radio terminal MS perform transmission / reception by the STBC transmission method before the negotiation of the communication capability is completed. As a result, even when there is one receiving antenna on the receiving side (that is, when the MIMO spatial multiplexing transmission method is not supported), there are a plurality of transmitting antennas on the transmitting side (that is, MIMO spatial multiplexing transmission). When the communication method is compatible), the communication quality can be improved by the diversity effect even before the communication capability negotiation is completed.

  Therefore, according to the present embodiment, it is possible to improve the communication quality before performing communication capability negotiation in a radio communication system in which base stations BS and radio terminals MS that support / do not support the MIMO spatial multiplexing transmission scheme are mixed.

  In addition, since the number of transmitting antennas is one and only one receiving side algorithm is required, the processing on the receiving side can be made common, and the cost and processing amount can be reduced. Furthermore, as the number of antennas on the receiving side increases, the communication quality improves due to the reception diversity effect.

  Next, in order to clarify the effect of this embodiment, a comparative example will be described.

  The first comparative example is a method of changing the signal pattern according to whether or not the radio terminal MS supports the MIMO transmission scheme in the LCH Assignment Request (step S102) in FIG. According to the first comparative example, the base station BS can quickly know whether or not the radio terminal MS is compatible with the MIMO transmission scheme. However, since such a signal pattern is finite, one base station BS When a large number of MIMO-compatible terminals are connected to the BS, the signal pattern is insufficient and the entire capacity of the TCCH is reduced.

  The second comparative example is a method for forcibly instructing the radio terminal MS whether it is a non-MIMO scheme or a MIMO scheme in the LCH Assignment Response (step S103) in FIG. In Comparative Example 2, if the radio terminal MS does not support the MIMO scheme, the base station BS cannot receive the Link Setup Request, so the radio terminal MS communicates with another base station or is separated by the base station BS. Since it is necessary to request the base station BS to change to this transmission method, a connection delay occurs.

(5) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the radio communication between the base station BS and the radio terminal MS is mainly described. However, when a radio relay device (relay node) is provided between the base station BS and the radio terminal MS, The present invention may be applied to wireless communication between the base station BS and the wireless relay device, and may be applied to wireless communication between the wireless terminal MS and the wireless relay device.

  In the embodiment described above, the configuration in which the number of transmission antennas is two has been mainly described, but the number of transmission antennas may be three or more. FIG. 8 is a diagram illustrating a schematic configuration on the transmission side according to a modification of the embodiment.

  As shown in FIG. 8, the transmission side has four transmission antennas, and the output of the STBC encoding unit (STBC Enc) is input to the antenna coding unit. The antenna coding unit is configured to perform antenna coding after applying the STBC code. There are various antenna coding methods. In order to obtain the effect of frequency diversity in the method of gaining gain by performing beamforming toward the receiving antenna (this method requires feedback information on the reverse side link), in flat fading environment, the delay amount is changed for each transmitting antenna There are methods. That is, if the number of transmission antennas increases, diversity gain can be obtained. On the other hand, since STBC encoding is performed in two layers, the STBC decoding unit on the receiving side can perform decoding as shown in Equation 5. Note that when there are four or more antennas, a four-layer format is possible, but this reduces the number of known signals per layer. Alternatively, there is a problem that the amount of information to be transmitted is reduced in order to secure a known signal equivalent to the two-layer format. When the number of known signals decreases, deterioration due to the quality of channel estimation errors increases. This presents a considerable penalty for terminals moving at high speed.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein.

  BS ... base station, MS ... wireless terminal, 10 ... wireless communication unit, 11 ... transmission unit, 15 ... reception unit, 18 ... network communication unit, 20 ... storage unit, 30 ... control unit, 31 ... MAC / PHY IF unit, 32 ... Layer control unit, 33 ... MAC / PHY IF unit, 40 ... Wireless communication unit, 41 ... Transmission unit, 45 ... Reception unit, 50 ... Storage unit, 60 ... Control unit, 101, 102 ... Antenna, 111 ... CRC addition , 112 ... scrambling section, 113 ... channel coding section, 114 ... bit interleaving section, 115 ... primary modulation section, 116 ... known signal generation section, 117 ... primary modulation section, 118 ... boosting section, 119 ... guard Symbol modulation unit, 120 ... synthesis unit, 121 ... layer mapping unit, 122 ... transmission precoding unit, 123 ... resource mapping unit, 124 ... IFFT unit, 1 25: GI insertion unit, 126: FIR filter unit, 127: DAC, 128: processing unit, 151 ... processing unit, 152 ... ADC, 153 ... FIR filter unit, 154 ... GI removal unit, 155 ... FFT unit, 156 ... de Subchannelization unit, 157 ... reference pilot / training symbol holding unit, 158 ... channel estimation unit, 159 ... MIMO decoding unit, 160 ... symbol demapping unit, 161 ... debit interleaving unit, 162 ... channel decoding unit, 163 ... desk Rambling unit, 164 ... CRC unit, 201, 202 ... antenna

Claims (7)

A wireless communication method for performing wireless communication between a transmission side communication device having a plurality of transmission antennas and a reception side communication device having one or a plurality of reception antennas,
In the connection sequence between the transmission side communication device and the reception side communication device, a negotiation step for negotiating communication capability;
A first transmission / reception step for performing transmission / reception between the transmission-side communication device and the reception-side communication device by a predetermined transmission method before the negotiation of the communication capability is completed;
A second transmission / reception step of performing transmission / reception between the transmission-side communication device and the reception-side communication device by a transmission method according to a result of the negotiation after the negotiation of the communication capability is completed;
Have
The specific transmission method is a transmission diversity method using the plurality of transmission antennas, and is a method applicable even if there is only one reception antenna of the reception-side communication device. Communication method.   When the receiving-side communication apparatus has a plurality of receiving antennas, the second transmitting / receiving step performs transmission / reception by a MIMO transmission method using the plurality of transmitting antennas and the plurality of receiving antennas. The wireless communication method according to claim 1.   The wireless communication method according to claim 1 or 2, wherein the first transmission / reception step transmits / receives at least one of broadcast information, a connection request message, a connection request response message, or a communication capability negotiation message. A transmission side communication device having a plurality of transmission antennas,
A transmission unit that performs transmission to a reception-side communication apparatus having one or a plurality of reception antennas via the plurality of transmission antennas;
Before the communication capability negotiation is completed in the connection sequence with the receiving-side communication device, control is performed so that transmission is performed according to a predetermined transmission method, and after the communication capability negotiation is completed, A control unit that controls transmission by a transmission method according to the result of the negotiation;
Have
The specific transmission scheme is a transmission diversity scheme using the plurality of transmission antennas, and is a scheme applicable even if there is only one reception antenna of the reception-side communication apparatus. Side communication device.   When the receiving-side communication apparatus has a plurality of receiving antennas, the control unit performs control so that transmission is performed by a MIMO transmission scheme using the plurality of transmitting antennas after the negotiation of the communication capability is completed. The transmission-side communication apparatus according to claim 4, wherein A receiving side communication device having one or more receiving antennas,
A receiving unit that performs reception from a transmission-side communication device having a plurality of transmission antennas via the one or more reception antennas;
Before the communication capability negotiation is completed in the connection sequence with the transmission side communication device, control is performed so that reception is performed by a predetermined transmission method, and after the communication capability negotiation is completed, A control unit that controls reception by a transmission method according to the result of the negotiation;
Have
The specific transmission method is a transmission diversity method using the plurality of transmission antennas, and is a method applicable even if there is only one reception antenna of the reception side communication device. Side communication device.   When the receiving-side communication apparatus has a plurality of receiving antennas, the control unit controls to perform reception by a MIMO transmission method using the plurality of receiving antennas after the communication capability negotiation is completed. The receiving-side communication device according to claim 6.

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