JP2008054336A - Radio transmission apparatus and radio transmission method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase a diversity gain at the time of resending data even when a temporal change of a radio signal propagation path environment is moderate. <P>SOLUTION: A data stream stored in a buffer 101 is modulated by a modulation section 102. A multiplier 103 multiplies a signal outputted from the modulation section 102 by weight outputted from a weight control section 112. A signal outputted from the multiplier 103 is added by an addition section 104 and transmitted via an antenna 106 after radio transmission processing is applied thereto by a transmission radio section 105. A buffer control section 111 controls the buffer 101 based on the number of times of resending outputted from a resending time detection section 158. The weight control section 112 outputs a weight different from that of the last transmission to the multiplier 103 every time data are resent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless transmission device and a wireless transmission method.

  In recent years, MIMO (Multi-Input Multi-Output) communication has been actively studied as a technology that enables large-capacity data communication such as images.

  Among them, BLAST (Bell Laboratories Layered Space-Time) is attracting attention as an application that can realize high-speed transmission using a MIMO channel. This is a technique in which streams independent from each other (or encoded) are transmitted from a plurality of transmission antennas, and each stream is detected while repeating spatial filtering and replica removal on the reception side.

  Further, it is known that a larger channel capacity can be obtained when MIMO channel information is known on the transmission side. More specifically, directivity control is performed using eigenvectors obtained by singular value decomposition of a matrix whose elements are MIMO channel responses, and this is realized by forming spatial orthogonal channels (eigenchannels). Is done. That is, when the MIMO channel information is known on the transmission side, the channel capacity can be maximized by forming orthogonal channels by multi-beam formation using eigenvectors and performing transmission power control by the water injection theorem (for example, Non-patent document 1).

  When the above technique is actually applied to a device, a plurality of transmission systems capable of transmitting a plurality of transmission data streams are prepared, and the transmission signals are multiplied by complex weights (hereinafter simply referred to as weights). Thus, the wireless transmission is performed after weighting.

  In addition, when the bit error rate on the receiving side does not satisfy the predetermined value, the receiving side transmits a retransmission request signal to the transmitting side, and the transmitting side transmits the same transmission data again in response to this request. (ARQ: Automatic Repeat reQuest) is also generally performed.

  In particular, in packet transmission for transmitting data traffic, it is necessary to guarantee data transmission without error, so that error control by ARQ is indispensable. In addition, in packet transmission, measurement errors and control delays are also applied when adaptive modulation and error correction are applied to improve throughput by selecting the optimum modulation and coding methods according to the state of the propagation path. Since packet errors caused by the above are unavoidable, the use of hybrid ARQ (hereinafter referred to as HARQ) incorporating a FEC (Forward Error Correction) function is also standardized in 3GPP (3rd Generation Partnership Project).

Therefore, by performing MIMO communication using a plurality of antennas at the time of data transmission, large-capacity data communication is possible. Further, when the reception data is incorrect on the reception side, data is retransmitted, and HARQ is received on the reception side. By combining the received data at the time of initial transmission and retransmission, a large improvement in throughput can be expected as this wireless communication system.
IEICE Technical Report RCS2002-53 (2002-05), The Institute of Electronics, Information and Communication Engineers

  However, in the conventional apparatus, even when data is retransmitted due to an error in received data, the propagation path environment through which the transmission signal passes, such as when the communication apparatus is stopped or moving at a low speed, is used. When the temporal change is gradual (see FIG. 13), the diversity gain obtained in the reception power on the reception side is small, so that there is a problem that the throughput of the wireless communication system is hardly improved even by data retransmission.

  This is because if the time change of the propagation path environment is slow, a signal with a low reception level at the time of initial transmission even at the time of data retransmission has a low reception level at the time of retransmission. This is because it becomes impossible to demodulate correctly. Also, when using multi-antenna technologies such as MIMO and STC (Space-Time Coding), if the time change of the propagation environment is moderate, there is little change in the fading state at the time of initial transmission and retransmission, Even if they are combined, the data cannot be demodulated correctly.

  The present invention has been made in view of such a point, and in a wireless communication system (for example, adaptive array antenna technology, MIMO technology, STC technology, etc.) that transmits a plurality of data streams using a plurality of antennas, HARQ An object of the present invention is to provide a wireless transmission device and a wireless transmission method capable of increasing the diversity gain at the time of data retransmission when the above is applied.

  The radio transmission apparatus of the present invention includes a multiplying unit that multiplies a plurality of data streams by a plurality of weights, a transmission unit that simultaneously transmits a plurality of data streams multiplied by weights from a plurality of transmission systems, and the plurality of the plurality of data streams. And a control unit that controls the multiplying unit to multiply the plurality of data streams by a weight different from the weight at the previous transmission when the data stream is retransmitted.

  According to this configuration, in a wireless communication system that transmits a plurality of data streams using a plurality of antennas (for example, adaptive array antenna technology, MIMO technology, STC technology, etc.), for example, when HARQ is applied, data Diversity gain at the time of retransmission can be increased, and reception performance on the receiving side can be improved.

  In the above configuration, the wireless transmission device of the present invention employs a configuration in which the control means selects a weight for retransmission from a plurality of weights corresponding to the plurality of data streams at the previous transmission.

  According to this configuration, the propagation path environments of the respective data streams are interchanged and averaged, so that the reception quality can be improved at an early stage.

  The radio transmission apparatus according to the present invention includes a transmission unit that transmits a plurality of data streams from a plurality of transmission systems at a predetermined transmission timing, and a transmission timing difference between the plurality of data streams when the plurality of data streams are retransmitted. Adopts a configuration having control means for controlling the transmission means so as to be different from the difference in transmission timing between the plurality of data streams at the time of previous transmission.

  According to this configuration, it is possible to average variations in the reception level on the frequency axis of each stream at the time of initial transmission and retransmission, so that the signal can be correctly demodulated and reception performance on the receiving side is improved. Can be made.

  The wireless transmission device of the present invention includes a transmission unit that transmits a plurality of data streams from a plurality of transmission systems at different transmission timings depending on a transmission system, and the transmission timing at the time of retransmission is the previous time when the plurality of data streams are retransmitted. And a control unit that controls the transmission unit to be different from the transmission timing at the time of transmission.

  According to this configuration, since the fading correlation between data streams transmitted from a plurality of transmission systems can be made different between the previous transmission time and the retransmission time, the signal can be demodulated correctly, and reception on the receiving side can be performed. Performance can be improved.

  In the above configuration, the wireless transmission device of the present invention employs a configuration in which the control means selects a transmission timing at the time of retransmission from among a plurality of transmission timings corresponding to the plurality of data streams at the time of previous transmission.

  According to this configuration, the propagation path environments of the respective data streams are interchanged and averaged, so that the reception quality can be improved at an early stage.

  The radio transmission apparatus according to the present invention employs a configuration in which, in the above configuration, the control means performs the control based on the notified line quality.

  According to this configuration, since the weight or transmission timing can be adjusted according to the channel quality notified from the wireless reception device or the like, the reception quality can be improved at an early stage.

  The radio transmission apparatus according to the present invention employs a configuration in which, in the above configuration, the transmission is diversity transmission.

  According to this configuration, since diversity transmission is performed, for example, adaptive array antenna technology, MIMO technology, STC technology, and the like can be applied to the present invention.

  The radio transmission apparatus according to the present invention employs a configuration in which the plurality of data streams are converted into multicarriers in advance in the above configuration.

  The radio transmission apparatus according to the present invention employs a configuration in which, in the above configuration, the multi-carrier is OFDM processing.

  According to these configurations, the present invention can be applied to multi-carrier communication (OFDM system or the like). In addition, by making data multi-carrier, it is possible to multiplex and transmit delayed waves with different delay times during retransmission, so that the state of the propagation environment between streams can be changed with each subcarrier. become.

  The wireless receiver of the present invention relates to a receiving means for transmitting a plurality of signals transmitted from a wireless transmitter and passing through different propagation paths simultaneously using a plurality of antennas, and a characteristic of the propagation path through the plurality of signals. Data acquisition for acquiring a reception data stream from a plurality of signals received by the receiving means based on information on propagation path information acquiring means for acquiring information and characteristics of the propagation path acquired by the propagation path information acquiring means Means for combining the received data stream obtained by the data obtaining means and received data stream at the time of previous reception and re-reception, and the characteristics of the propagation path obtained by the propagation path information obtaining means A notification means for notifying the wireless transmission device of information related to the wireless transmission device.

  According to this configuration, for example, HARQ can be applied in MIMO communication or STC communication.

  The wireless transmission method of the present invention includes a multiplication step of multiplying a plurality of data streams by a plurality of weights, a transmission step of simultaneously transmitting a plurality of data streams multiplied by weights from a plurality of transmission systems, A control step of controlling the data streams to be multiplied by a weight different from the weight at the previous transmission when the data stream is retransmitted.

  According to this method, diversity gain at the time of data retransmission can be increased, and reception performance on the receiving side can be improved.

  The wireless transmission method of the present invention includes a transmission step of transmitting a plurality of data streams from a plurality of transmission systems at a predetermined transmission timing, and a difference in transmission timing between the plurality of data streams during retransmission of the plurality of data streams. Has a control step for controlling so as to be different from the difference in transmission timing between the plurality of data streams at the time of previous transmission.

  According to this method, variations in the reception level on the frequency axis of each stream during initial transmission and retransmission can be averaged, so that the signal can be demodulated correctly and reception performance on the receiving side can be improved. Can be made.

  The wireless transmission method of the present invention includes a transmission step of transmitting a plurality of data streams from a plurality of transmission systems at different transmission timings depending on the transmission system, and when the plurality of data streams are retransmitted, the transmission timing at the time of retransmission is the previous time. And a control step for performing control so as to be different from the transmission timing at the time of transmission.

  According to this method, since the fading correlation between data streams transmitted from a plurality of transmission systems can be made different between the previous transmission time and the retransmission time, the signal can be correctly demodulated, and reception on the receiving side can be performed. Performance can be improved.

  The wireless reception method of the present invention relates to a reception step in which a wireless transmission device transmits a plurality of signals via different propagation paths and receives simultaneously using a plurality of antennas, and a propagation path characteristic through the plurality of signals. A propagation path information acquisition step for acquiring information, a data acquisition step for acquiring a received data stream from a plurality of received signals based on information on the characteristics of the propagation path acquired in the propagation path information acquisition step, and The combining step of combining the reception data stream acquired in the data acquisition step and the reception data stream at the time of previous reception and re-reception, and information on the characteristics of the propagation path acquired in the propagation path information acquisition step A notification step of notifying the wireless transmission device.

  According to this method, for example, HARQ can be applied in MIMO communication or STC communication.

  According to the present invention, in a wireless communication system that transmits a plurality of data streams using a plurality of antennas (for example, adaptive array antenna technology, MIMO technology, STC technology, etc.), for example, when HARQ is applied, data Diversity gain at the time of retransmission can be increased, and reception performance on the receiving side can be improved.

  The essence of the present invention is that when a plurality of data streams are simultaneously transmitted wirelessly using a plurality of transmission systems, when a data stream is retransmitted, the propagation path environment through which the data stream passes after transmission is intentionally different from the previous transmission. It is to let you.

  The present invention can be broadly divided into two cases as a method of changing the propagation path environment of a transmission signal. The first case is a method of changing the weight to be multiplied by the transmission signal, and the second case is a method of changing the timing of transmitting the transmission signal.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The first embodiment is a case where the weight to be multiplied by the transmission signal is changed, and the second embodiment is a case where the timing for transmitting the transmission signal is changed.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a radio transmission apparatus according to Embodiment 1 of the present invention. Here, a case will be described as an example where two streams of data stream #A and data stream #B are transmitted using two antennas.

  1 includes a buffer 101, a modulation unit 102, a multiplier 103, an addition unit 104, a transmission radio (RF) unit 105, a transmission antenna 106, a retransmission number detection unit 110, a buffer control unit 111, and weight control. Part 112.

  In FIG. 1, data stream #A is input to buffer 101-1, and data stream #B is input to buffer 101-2.

  The buffers 101-1 and 101-2 accumulate the input data stream in preparation for a data retransmission request from the wireless reception device. When receiving a data transmission instruction from the buffer control unit 111, the data is output to the modulation units 102-1 and 102-2.

  Modulation section 102-1 performs modulation processing on the data stream output from buffer 101-1, and outputs the result. The signal output from the modulation unit 102-1 is branched on the way and output to the multipliers 103-1, 103-2. Similarly, the modulation unit 102-2 performs modulation processing on the data stream output from the buffer 101-2 and outputs the data stream. The signal output from the modulation unit 102-2 is branched on the way and output to the multipliers 103-3 and 103-4.

  Multiplier 103-1 multiplies the signal output from modulation section 102-1 by the weight output from weight control section 112 and outputs the result to addition section 104-1. Multiplier 103-2 multiplies the signal output from modulation section 102-1 by the weight output from weight control section 112, and outputs the result to addition section 104-2.

  Similarly, multiplier 103-3 multiplies the signal output from modulation section 102-2 by the weight output from weight control section 112, and outputs the result to addition section 104-1. Multiplier 103-4 multiplies the signal output from modulation section 102-2 by the weight output from weight control section 112, and outputs the result to addition section 104-2. The weights multiplied by the signals in the multipliers 103-1 to 103-4 will be described in detail later.

  Adder 104-1 adds the signals multiplied by the weights output from multipliers 103-1, 103-3, and outputs the result to transmission radio section 105-1. Similarly, the addition unit 104-2 adds the signals output from the multipliers 103-2 and 103-4, and outputs the result to the transmission radio unit 105-2.

  Transmission radio section 105-1 performs a predetermined radio transmission process such as up-conversion on the signal output from addition section 104-1, converts it to a radio signal, and transmits it through antenna 106-1. Similarly, transmission radio section 105-2 performs radio transmission processing on the signal output from addition section 104-2 and transmits the signal via antenna 106-2.

  The radio receiving apparatus that has received signals transmitted from antennas 106-1 and 106-2 performs error detection on the received signal, and if an error is detected, sends a NACK signal to the radio transmitting apparatus according to the present embodiment. If no error is detected, an ACK signal is sent.

  The retransmission number detection unit 110 detects the number of data retransmissions from the ACK / NACK signal notified from the wireless reception device and outputs the detected number of data retransmissions to the buffer control unit 111.

  The buffer control unit 111 outputs a data output control signal to the buffers 101-1 and 101-2 based on the number of retransmissions output from the retransmission number detection unit 110. Specifically, when there is a data retransmission request from the wireless reception device, the buffer 101-1 and 101-2 are controlled to output the accumulated data at the previous transmission again.

  The weight control unit 112 has a table in which a plurality of types of weights are stored, selects a weight to be multiplied by the transmission signal from the table according to the number of retransmissions detected by the retransmission number detection unit 110, and Output. At the time of data retransmission, the weight table is referred again, and the weights different from those at the first transmission are output to the multipliers 103-1 to 103-4.

  FIG. 2 is a block diagram showing a configuration of the radio reception apparatus according to the present embodiment.

  This radio reception apparatus includes a reception antenna 151, a reception radio (RF) unit 152, a MIMO reception unit 153, a buffer 154, a demodulation unit 155, an error detection unit 156, an ACK / NACK signal generation unit 157, and a retransmission number detection unit 158. Have.

  In FIG. 2, a reception radio (RF) unit 152 performs predetermined radio processing such as down-conversion on a signal received via the reception antenna 151 and outputs the result to the MIMO reception unit 153.

  MIMO receiving section 153 separates the signal output from reception radio section 152 into two substreams, that is, streams #A and #B using the propagation path characteristic information (MIMO reception processing), and outputs each to buffer 154 To do. This MIMO reception processing is performed by applying an inverse matrix of a matrix of 2 rows × 2 columns having elements of propagation path characteristics through which signals transmitted from two antennas on the transmission side pass, to received signals. Get a substream.

  The buffer 154 immediately outputs this data to the demodulator 155 in the case of packet data at the time of initial transmission. When a retransmission packet is transmitted, this data is temporarily stored and demodulated. When the packet is correctly received and an ACK signal is returned, the buffer is cleared. Since the buffer 154 is notified of the number of retransmissions from the retransmission number detection unit 158, it can be determined whether the packet is for the first transmission or for the retransmission.

  Demodulation section 155 performs demodulation processing on the data stream output from buffer 154 to obtain data stream #A and data stream #B.

  The error detector 156 detects an error and notifies the ACK / NACK signal generator 157 to that effect.

  When notified from the error detection unit 156 that an error has been detected, the ACK / NACK signal generation unit 157 generates a NACK signal and sends the NACK signal to the wireless transmission device and the retransmission count detection unit 158 at the same time. When notified from the error detection unit 156 that an error has not been detected, an ACK signal is sent to the wireless transmission device and the retransmission count detection unit 158.

  FIG. 3 is a sequence diagram showing a flow of wireless communication realized by the above configuration.

  When transmitting a data stream, the transmitting apparatus first determines a weight by which the transmission signal for each transmission system is multiplied (ST1010). Then, the transmission signal is multiplied by this weight (ST1020), and the data stream is transmitted (ST1030).

  The receiving apparatus receives the data stream transmitted from the transmitting apparatus (ST1040), and detects a data error (ST1050). If there is an error, a NACK signal is generated (ST1060), and the NACK signal is transmitted to the transmitting apparatus (ST1070).

  The transmitting apparatus that has detected the NACK signal notified from the receiving apparatus (ST1080) changes the weight determined for each transmission system in ST1010 (ST1090), and multiplies the retransmitted transmission signal (ST1100). To the receiving apparatus (ST1110).

  Next, an example of the weight multiplied by the transmission signal under the control of the weight control unit 112 will be described with reference to FIG.

FIG. 4A is a diagram illustrating the weights multiplied by the transmission signal for each data stream #A (S _A ) and data stream #B (S _B ). For example, at the time of initial data transmission, the stream #A is multiplied by the weight w _α in the transmission system on the antenna 106-1 (hereinafter referred to as antenna # 1) side, and the antenna 106-2 (hereinafter referred to as antenna # 2). The weight _wβ is multiplied in the transmission system on the) side. Also, the stream #B is multiplied by the weight w _γ in the transmission system on the antenna # 1 side, and is multiplied by the weight w _δ in the transmission system on the antenna # 2 side.

In the first retransmission, the stream #A is multiplied by the weight w _γ in the transmission system on the antenna # 1 side, and is multiplied by the weight w _δ in the transmission system on the antenna # 2 side. Also, the stream #B is multiplied by the weight w _α in the transmission system on the antenna # 1 side, and is multiplied by the weight w _β in the transmission system on the antenna # 2 side.

  That is, here, the weight used for data stream #A at the first transmission is used for data stream #B at the first retransmission. Also, the weight used for data stream #B at the first transmission is used for data stream #A in the first retransmission. In the first transmission and the first retransmission, the weights used for stream #A and stream #B are interchanged.

  In the second retransmission, the weights used for the stream #A and the stream #B are switched, and the same weight as that at the first transmission is obtained. In the third retransmission, the weights used for the stream #A and the stream #B are further switched to be the same weight as the first retransmission. That is, each time retransmission is repeated, the weights used for stream #A and stream #B are switched.

  FIG. 4B shows the weights multiplied by the transmission signal for each antenna # 1 and antenna # 2 from different viewpoints. That is, this figure shows what signals are actually transmitted from antenna # 1 and antenna # 2. The contents shown in FIGS. 4A and 4B are substantially the same.

  Next, the operation of changing the weight between the initial transmission and the retransmission will be described. By multiplying the transmission signal by the weight, the transmission signal has directivity. However, this directivity is not an image in which a transmission signal is actually propagated in a specific direction as seen in the beam forming of the array antenna technology, but is a mathematical story. This is because the fading correlation between antennas is low in MIMO communication, whereas the fading correlation between antennas is high in the array antenna technique. However, in considering the operation of weight multiplication according to the present embodiment, this expression is used because it is easy to understand if it is explained by an image in which a transmission signal is actually propagated with directivity.

FIG. 5 is a diagram conceptually illustrating the directivity of the transmission signal. A signal transmitted from the wireless transmission device 100 using the weights w _α and w _β passes through the thick-line path # 1 in the figure and is reflected by the building 191 on the way, but the wireless reception device does not significantly decrease the intensity. 150 is reached. On the other hand, the signal transmitted using the weights w _γ and w _δ passes through the thin line path # 2 in the figure, is reflected by the building 192 on the way, and is significantly weakened due to the influence of the propagation path. Receiving device 150 is reached.

The first transmission, the weights w _alpha and w as multiplied stream #A is the path # 1 and _beta, the weight w _alpha and w stream #B multiplied with _beta passes through the path # 2. At the time of retransmission, the weight multiplied by the transmission signal is switched, so that stream #A passes path # 2 and stream #B passes path # 1.

  6 and 7 are diagrams for comparing the quality on the reception side of signals transmitted from the conventional radio transmission apparatus and the radio transmission apparatus according to the present embodiment. These diagrams conceptually show the quality (bar graph) of the received signal after synthesis on the receiving side and the level L1 at which data can be correctly received.

  FIG. 6 shows a case of a conventional wireless transmission apparatus. FIG. 6A is a diagram showing the reception quality at the time of initial transmission of data, and FIG. 6B is a diagram showing the reception quality at the time of data retransmission.

  In FIG. 6A, both stream #A and stream #B have received signal quality levels not exceeding level L1. At this time, since the receiving side cannot receive the data correctly, it returns a NACK signal to the transmitting side, and the transmitting side retransmits the data. However, when the temporal change of the propagation path environment is small, it cannot be expected that the reception quality on the receiving side is greatly improved even at the time of data retransmission. Therefore, as shown in FIG. 6 (b), the stream #A whose reception quality was originally close to the level L1 at the time of the first transmission is synthesized by combining the reception signals at the time of the first transmission and the retransmission after the data retransmission. Although the reception quality after combining exceeds level L1, the reception quality of stream #B cannot exceed level L1 even if data is retransmitted. Therefore, the reception side returns a NACK signal to the transmission side several more times until the reception quality of stream #B exceeds level L1, and the transmission side retransmits data each time.

  FIG. 7 shows a case of the wireless transmission device according to the present embodiment. FIG. 7A is a diagram showing the reception quality at the first transmission of data, and FIG. 7B is a diagram showing the reception quality at the time of data retransmission.

  FIG. 7 (a) is the same as FIG. 6 (a). Both stream #A and stream #B have reception quality levels that do not exceed level L1. However, since the weights used for the stream #A and the stream #B are switched at the time of retransmission, the propagation path environment through which the stream #A and the stream #B pass is averaged. As a result, the reception quality levels of the streams #A and #B after combining the reception signals at the time of initial transmission and retransmission are both in a state exceeding the level L1, so that signals can be received correctly.

  In the above configuration, the weight control section 112 of the radio reception apparatus according to the present embodiment changes the weight multiplied by the transmission signal from the weight used at the previous transmission every time data is retransmitted.

  As a result, since each data stream is transmitted to the receiving side via different propagation path environments at the time of previous transmission and at the time of retransmission, the probability that the same data will continue to be erroneous is reduced. The error rate characteristic of the combined data is improved. In other words, diversity gain at the time of combining retransmission data on the receiving side increases, and reception performance on the receiving side improves.

  In addition, every time data is retransmitted, weight control section 112 of the radio receiving apparatus according to the present embodiment multiplies the transmission signal by replacing the weight corresponding to each antenna with the previous transmission.

  For example, as shown in FIG. 6 (a) or FIG. 7 (a), even if the receiving side returns a NACK signal at the time of initial transmission, the reception quality of all data streams is not bad on average. The reception quality of only some data streams is often poor.

  At this time, since the transmission path environments of the respective data streams are replaced with each other and averaged by switching the weights to be multiplied with the transmission signals at the time of the previous transmission and at the time of retransmission, the reception quality is improved at an early stage.

  In addition, since the weights that have already been used are simply used by exchanging the signals to be multiplied, no other information, for example, means for feeding back the propagation path information detected on the reception side to the transmission side is required.

  As described above, according to the present embodiment, since the weights to be multiplied with the transmission signal are switched between the initial transmission and the retransmission, the diversity gain at the time of data retransmission can be increased, and the reception performance on the reception side is improved. be able to.

  Here, the case where the transmission data is two streams #A and #B has been described as an example, but there may be three or more data streams. In this case, the weight used at the time of data retransmission is Rotate and use. That is, when there are three data streams, the weight used at the first transmission for the third retransmission is used again.

In addition, here, the MIMO transmission having a low fading correlation between antennas has been described as an example, but an array antenna having a high fading correlation between antennas may be used. At this time, the antennas are arranged so that the fading correlation between the antennas is 1. By multiplying the transmission signal by a weight, a directivity pattern as shown in FIG. 5 is formed. The time of the first transmission, weights w _alpha and w _beta stream #A multiplied the passes through the path # 1, the weight w _alpha and w stream #B multiplied the _beta passes through the path # 2. At the time of retransmission, the weight multiplied by the transmission signal is switched, so that stream #A passes path # 2 and stream #B passes path # 1. Thereby, the propagation path environment can be averaged similarly to the above.

  Although the case where the weights of the stream #A and the stream #B are exchanged at the time of data retransmission has been described as an example here, the weight used at the time of retransmission may be selected from a completely different value instead of the weight used at the previous transmission. good.

  Furthermore, in order to increase the channel capacity, the channel quality information is fed back from the receiving side to the transmitting side, and when the weight is determined and transmitted so as to allocate more power to the channel with good quality, this feedback is given. It is also possible to finely adjust the weight based on the line quality information and perform weighting so that the line quality exceeds the minimum level L1 in all paths.

(Embodiment 2)
FIG. 8 is a block diagram showing a configuration of a radio transmission apparatus according to Embodiment 2 of the present invention. This radio transmission apparatus has the same basic configuration as that of the radio transmission apparatus shown in FIG. 1, and the same components are denoted by the same reference numerals and the description thereof is omitted.

  A feature of the present embodiment is that it has an IFFT unit 201, a delay unit 202, and a delay control unit 203, performs communication by OFDM scheme, adds a different delay time for each transmission data stream, and transmits from different antennas at the time of transmission. By transmitting at another transmission timing, the characteristic on the frequency axis of the received signal is greatly changed. Therefore, the propagation path environment can be greatly changed every time retransmission is performed.

  Next, the operation of the wireless transmission apparatus having the above configuration will be described.

  Modulation section 102-1 performs modulation processing on the data stream output from buffer 101-1, and outputs the result. The signal output from the modulation unit 102-1 is branched in the middle and output to the IFFT units 201-1 and 201-2. Similarly, the modulation unit 102-2 performs modulation processing on the data stream output from the buffer 101-2 and outputs the data stream. The signal output from modulation section 102-2 is branched halfway and output to IFFT sections 201-3 and 201-4.

  On the other hand, the delay control unit 203 has a table storing a plurality of types of delay times, and selects a delay time for each transmission signal from the table according to the number of retransmissions of data notified from the retransmission number detection unit 110. And output to the delay units 202-1 to 202-4. The delay time output from the delay control unit 203 will be described in detail later.

  The delay unit 202-1 delays the transmission timing of the signal output from the IFFT unit 201-1 by the delay time output from the delay control unit 203, and outputs the delayed signal to the addition unit 104-1. Also, delay section 202-2 delays the transmission timing of the signal output from IFFT section 201-2 by the delay time output from delay control section 203, and outputs the result to adder 104-2.

  Similarly, delay section 202-3 delays the transmission timing of the signal output from IFFT section 201-3 by the delay time output from delay control section 203, and outputs the result to adder 104-1. The delay unit 202-4 delays the transmission timing of the signal output from the IFFT unit 201-4 by the delay time output from the delay control unit 203, and outputs the delayed signal to the adder 104-2.

  Adder 104-1 adds the signals delayed in transmission timing output from delay sections 202-1 and 202-3, and outputs the result to transmission radio section 105-1. Similarly, adding section 104-2 adds the signals output from delay sections 202-2 and 202-4, and outputs the result to transmitting radio section 105-2. The subsequent processing is the same as in the first embodiment.

  Next, the delay time of the transmission timing of each system transmission signal will be described with reference to FIG.

FIG. 9A is a diagram showing the delay time of the transmission timing of the transmission signal for each of the data stream #A (S _A ) and the data stream #B (S _B ). For example, the first transmission of data, the delay time of the stream #A is the transmission system on the antenna # 1 side 0, a tau _alpha for the transmission system on the antenna # 2 side. Further, the delay time of the stream #B is 0 in the transmission system on the antenna # 1 side and τ _β in the transmission system on the antenna # 2 side.

Then, retransmission is first, the delay time of the stream #A is the transmission system on the antenna # 1 side 0, a tau _beta for the transmission system on the antenna # 2 side. The delay time of the stream #B is the transmission system on the antenna # 1 side 0, a tau _alpha for the transmission system on the antenna # 2 side.

  That is, the combination of the delay times of the data stream #A at the first transmission is used for the data stream #B at the first retransmission. Also, the combination of delay times used for data stream #B during the initial transmission is used for data stream #A in the first retransmission. At the first transmission and the first retransmission, the combinations of delay times used for stream #A and stream #B are interchanged.

In the second retransmission, the delay time used for the transmission system on the antenna # 1 side and the delay time used for the transmission system on the antenna # 2 side at the time of initial transmission are interchanged. That is, the delay time of the stream #A is τ _α in the transmission system on the antenna # 1 side and 0 in the transmission system on the antenna # 2 side, and the delay time of the stream #B is τ in the transmission system on the antenna # 1 side. _β is 0 in the transmission system on the antenna # 2 side. In the third retransmission, the delay times used for stream #A and stream #B are switched.

  In addition, FIG. 9B shows an arrangement of delay times for delaying transmission signals for each antenna # 1 and antenna # 2 from a different viewpoint. That is, this figure is a diagram showing how signals are actually delayed and transmitted from antenna # 1 and antenna # 2. The contents shown in FIGS. 9A and 9B are substantially the same.

FIG. 10 is a diagram showing, on the time axis, the transmission timing of the signal transmitted from the wireless transmission device. Although the actual transmission data stream is weighted (for example, the signal transmitted from antenna # 1 is w _α S _A + w _γ S _{B as} described above), in this embodiment, at the time of retransmission Since the weights are the same as those at the first transmission, the weights are not shown so that the signals can be easily distinguished.

This figure shows that the first data transmission is performed at time 0 and the data is retransmitted at time t ₁ after a certain time has elapsed. From the antenna # 1, the data stream #A (S _A , S ′ _A ) and the data stream #B (S _B , S ′ _B ) are transmitted at the same timing both during the initial transmission and during the retransmission. On the other hand, from the antenna # 2, S _A is transmitted with a time τ _α and S _B with a delay of time τ _β at the first transmission, whereas S ′ _A is transmitted with a time τ _β and S ′ _B at the time of retransmission. There are transmitted are respectively delayed time tau _alpha.

Here, focusing on data stream #A at the time of initial transmission (S _A), S A is transmitted with a time difference tau _alpha antenna # 1 and antenna # 2. This is to reduce the fading correlation between the antennas. On the other hand, paying attention retransmission time of the data stream #A (S _'A), the time difference provided between the antenna # 1 and antenna # 2 has a tau _beta. That is, transmission is performed such that the fading correlation between antennas is changed between the initial transmission and the retransmission. The same applies to the data stream #B (S _B , S ′ _B ).

When attention is paid to both S _A and S _B transmitted from antenna # 2 at the time of initial transmission, S _B is transmitted with a delay of (τ _β −τ _α ) from S _A. On the other hand, at the time of retransmission, S ′ _A is transmitted with a delay of (τ _β −τ _α ) from S ′ _B. This means that transmission is performed such that the transmission timing is changed between the initial transmission and the retransmission. Here, for the sake of simplicity of explanation, only the data stream transmitted from antenna # 2 has been described. However, the same can be said for the data stream transmitted from antenna # 1. .

  Next, an operation by changing the transmission timing between the initial transmission and the retransmission will be described. In short, frequency selective fading is a result of the waves having the same frequency but being 180 degrees out of phase weakening each other. Therefore, the fading characteristic received by the signal can be changed by intentionally delaying the transmission timing of the transmission signal, that is, by shifting the phase. FIG. 11 is a diagram showing reception power in the conventional apparatus. Stream #A has a high reception level both during initial transmission (see FIG. 11A) and retransmission (see FIG. 11B), while stream #B has a low reception level during both initial transmission and retransmission. Therefore, even if the data at the initial transmission and the data at the time of retransmission are combined (see FIG. 11C), only the stream #A reaches a level at which it is correctly received, and the stream #B remains unable to be received correctly.

  FIG. 12 is a diagram showing reception power in the present embodiment. The level of the received signal is subjected to frequency selective fading that differs for each stream. Accordingly, the reception level pattern on the frequency axis differs for each stream. At the time of initial transmission (see FIG. 12 (a)) and retransmission (see FIG. 12 (b)), the delay processing applied to stream #A and stream #B is interchanged. Are averaged (see FIG. 12C), and it is possible to correctly demodulate both stream #A and stream #B.

  Here, it is a diagram illustrating a situation in which the phase of the fading characteristic curve on the frequency axis is shifted by 180 degrees by delaying the transmission signal. However, in the present embodiment, it is sufficient that the fading characteristics change to some extent by delaying the transmission signal, and the phase does not necessarily have to be shifted by 180 degrees. However, since the fluctuation pitch of the fading characteristic depends on the moving speed of the mobile station and the frequency band used for communication, it is possible to calculate a delay time for shifting the phase of the fading characteristic curve by 180 degrees. .

  As described above, according to the present embodiment, since the variation of the reception level on the frequency axis of each stream is averaged for each retransmission, the combined signal can be correctly demodulated, and the reception performance on the reception side Can be improved.

  Note that Embodiment 1 and Embodiment 2 can be used in combination. That is, the transmission signal multiplied by the weight may be transmitted with the transmission timing delayed. At this time, the effect of each embodiment is superimposed, and reception performance can be further improved.

1 is a block diagram showing a configuration of a wireless transmission device according to Embodiment 1 of the present invention. FIG. 2 is a block diagram showing a configuration of a radio reception apparatus according to Embodiment 1 of the present invention. The sequence diagram which shows the flow of the radio | wireless communication which concerns on Embodiment 1 of this invention. The figure which shows the weight by which a transmission signal is multiplied by a weight control part A diagram conceptually explaining the directivity of the transmitted signal The figure which shows the quality in the receiving side of the signal transmitted from the conventional radio | wireless transmitter. The figure which shows the quality in the receiving side of the signal transmitted from the radio | wireless transmitter which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of the radio | wireless transmitter which concerns on Embodiment 2 of this invention. The figure which shows the delay time of the transmission signal for every transmission system Diagram showing transmission timing of transmission signal The figure which shows the reception power in the conventional device The figure which shows the receiving power in Embodiment 2 of this invention The figure which shows the reception power of the reception side when the time change of the propagation path environment where the transmission signal passes is slow

Explanation of symbols

103-1 to 103-4 Multipliers 104-1 and 104-2 Addition units 105-1 and 105-2 Transmission radio units 106-1 and 106-2 Transmission antenna 110 Retransmission count detection unit 112 Weight control unit 201-1 201-4 IFFT unit 202-1 to 202-4 delay unit 203 delay control unit

Claims (14)

Multiplying means for multiplying a plurality of data streams by a plurality of weights;
Transmitting means for simultaneously transmitting a plurality of data streams multiplied by weights from a plurality of transmission systems;
Control means for controlling the multiplying means so as to multiply the plurality of data streams by a weight different from the weight at the time of previous transmission when retransmitting the plurality of data streams;
A wireless transmission device comprising: The control means includes
Selecting a retransmission weight from a plurality of weights corresponding to the plurality of data streams at the previous transmission;
The wireless transmission device according to claim 1. Transmission means for respectively transmitting a plurality of data streams from a plurality of transmission systems at a predetermined transmission timing;
Control means for controlling the transmission means so that a difference in transmission timing between the plurality of data streams differs from a difference in transmission timing between the plurality of data streams at the time of previous transmission when retransmitting the plurality of data streams;
A wireless transmission device comprising: Transmission means for transmitting a plurality of data streams from a plurality of transmission systems, respectively at different transmission timings depending on the transmission system,
At the time of retransmission of the plurality of data streams, control means for controlling the transmission means so that the transmission timing at the time of retransmission is different from the transmission timing at the time of previous transmission;
A wireless transmission device comprising: The control means includes
Selecting a transmission timing at retransmission from a plurality of transmission timings corresponding to the plurality of data streams at the previous transmission;
The wireless transmission device according to claim 3 or 4, wherein   The radio transmission apparatus according to claim 1, wherein the control unit performs the control based on the notified line quality.   The radio transmission apparatus according to claim 1, wherein the transmission is diversity transmission.   The radio transmission apparatus according to any one of claims 1 to 7, wherein the plurality of data streams are converted into multicarriers in advance.   9. The radio transmission apparatus according to claim 8, wherein the multi-carrier is OFDM (Orthogonal Frequency Division Multiplex) processing. A receiving means for transmitting a plurality of signals transmitted by a wireless transmission device and passing through different propagation paths simultaneously using a plurality of antennas;
Propagation path information acquisition means for acquiring information on the characteristics of the propagation path through the plurality of signals;
Data acquisition means for acquiring a reception data stream from a plurality of signals received by the reception means based on information on the characteristics of the propagation path acquired by the propagation path information acquisition means;
A combining unit that combines the reception data stream acquired by the data acquisition unit and received data stream at the time of previous reception and re-reception;
Notification means for notifying the wireless transmission device of information related to the characteristics of the propagation path acquired by the propagation path information acquisition means;
A wireless receiver characterized by comprising: A multiplication step of multiplying a plurality of data streams by a plurality of weights, respectively;
A transmission step of simultaneously transmitting a plurality of data streams multiplied by weights from a plurality of transmission systems;
A control step of controlling to multiply the plurality of data streams by a weight different from the weight at the time of previous transmission when retransmitting the plurality of data streams;
A wireless transmission method comprising: A transmission step of transmitting a plurality of data streams respectively from a plurality of transmission systems at a predetermined transmission timing;
A control step of controlling the difference in transmission timing between the plurality of data streams to be different from the difference in transmission timing between the plurality of data streams at the previous transmission when retransmitting the plurality of data streams;
A wireless transmission method comprising: A transmission step of transmitting a plurality of data streams from a plurality of transmission systems, respectively at different transmission timings depending on the transmission system;
At the time of retransmission of the plurality of data streams, a control step for controlling the transmission timing at the time of retransmission to be different from the transmission timing at the time of previous transmission;
A wireless transmission method comprising: A reception step in which a wireless transmission device transmits and receives a plurality of signals via different propagation paths simultaneously using a plurality of antennas;
A propagation path information obtaining step for obtaining information on propagation path characteristics through the plurality of signals;
A data acquisition step of acquiring a reception data stream from a plurality of received signals based on information on the characteristics of the propagation path acquired in the propagation path information acquisition step;
A combining step of combining the reception data stream acquired in the data acquisition step and the reception data stream at the time of previous reception and re-reception;
A notification step of notifying the wireless transmission device of information related to the characteristics of the propagation path acquired in the propagation path information acquisition step;
A wireless reception method comprising:

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