Title of Invention	RADIO TRANSMISSION APPARATUS AND RADIO TRANSMISSION METHOD
Abstract	The invention relates to a radio transmission apparatus comprising a multiplication section (103-1, 103-2, 103-3, 103-4) that multiplies a plurality of data streams (#A,#B) by a plurality of weights (Wα, Wβ, Wγ, Wδ) respectively; a transmission section (105-1, 105-2) that transmits the plurality of weighted data streams from a plurality of transmission antennas (106-1, 106-2) simultaneously; and a control section (112) that controls said multiplication section (103-1, 103- 2, 103-3, 103-4) so that at the time of retransmission of said plurality of data streams (#A,#B) said plurality of data streams is multiplied by weights (Wα, Wβ, Wγ, Wδ) different from the weights (Wα, Wβ, Wγ, Wδ) at the time of previous transmission. The said control section (112) selects weights (Wα, Wβ, Wγ, Wδ) at the time of the retransmission from among a plurality of weights (Wα, Wβ, Wγ, Wδ) corresponding to said plurality of data streams (#A,#B) at the time of the previous transmission.

Title of Invention

RADIO TRANSMISSION APPARATUS AND RADIO TRANSMISSION METHOD

Abstract

The invention relates to a radio transmission apparatus comprising a multiplication section (103-1, 103-2, 103-3, 103-4) that multiplies a plurality of data streams (#A,#B) by a plurality of weights (Wα, Wβ, Wγ, Wδ) respectively; a transmission section (105-1, 105-2) that transmits the plurality of weighted data streams from a plurality of transmission antennas (106-1, 106-2) simultaneously; and a control section (112) that controls said multiplication section (103-1, 103- 2, 103-3, 103-4) so that at the time of retransmission of said plurality of data streams (#A,#B) said plurality of data streams is multiplied by weights (Wα, Wβ, Wγ, Wδ) different from the weights (Wα, Wβ, Wγ, Wδ) at the time of previous transmission. The said control section (112) selects weights (Wα, Wβ, Wγ, Wδ) at the time of the retransmission from among a plurality of weights (Wα, Wβ, Wγ, Wδ) corresponding to said plurality of data streams (#A,#B) at the time of the previous transmission.

Full Text	DESCRIPTION RADIO TRANSMISSION APPARATUS AND RADIO TRANSMISSION METHOD Technical Field The present invention relates to a radio transmission apparatus and radio transmission method. Background Art As a technology for realizing communications of large-volume data such as images, MIMO (Multi-Input Multi-Output) communications are being studied actively in recent years. Among them, BLAST (Bell Laboratories Layered Space-Time) in particular is a focus of attention as an application capable of realizing high-speed transmission using an MIMO channel. This is a technique for transmittingmutuallyindependent (or coded) streams from a plurality of transmission antennas and detecting the respective streams while repeating spatial filtering and removal of replicas on the receiving side. Furthermore, when the MIMO channel information is known to the transmitting side, it is known that a greater channel capacity can be obtained. More specifically, this is realized by carrying out directivity control using an eigen vector obtained through singular value decomposition of a matrix which consists of the respective channel responses of the MIMO channels as elements and forming a spatially orthogonal channel (eigen channel). That is, when the MIMO channel information is known to the transmitting side, it is possible to form an orthogonal channel through multi-beam formation using the eigen vector, performing transmit power control through an irrigation theorem and thereby maximize the channel capacity (e.g., TECHNICAL REPORT OF IEICE RCS2002-53 (2002-05), Institute of Electronics, Information and Communication Engineers). When the above described technology is applied to an actual apparatus, radio transmission is carried out after preparing a plurality of transmission systems capable of carrying out transmission processing on a plurality of transmission data streams and assigning weights by multiplying the transmission signals by their respective complex weights (hereinafter simply referred to as "weights"). When a bit error rate on the receiving side does not satisfy a predetermined value, an automatic retransmission request (ARQ; Automatic Repeat reQuest) is also generally practiced whereby the receiving side sends a retransmission request signal to the transmitting side and the transmitting side retransmits the same transmission data in response to this request. Especiallypacket transmission which transmits data traffic is required to guarantee error-free data transmission, and therefore error control through ARQ is indispensable. In addition, when an adaptive modulation and error correction intended to improve the throughput by selecting an optimal modulation system or coding system according to the condition of a propagation path (path)are applied to packet transmission, it is not possible to avoid measuring errors or packet errors caused by a control delay, etc., and therefore the 3GPP (3rd Generation Partnership Project) also standardizes the use of a hybrid ARQ (hereinafter referred to as "HARQ") which incorporates an FEC (Forward Error Correction) function. Therefore, by carrying out an MIMO communication using a plurality of antennas during data transmission to realize a large-volume data communication and retransmitting data when received data contains errors on the receiving side and by combining received data at the time of initial transmission with the received data at the time of retransmission using HARQ on the receiving side, a considerable improvement of throughput can be expected for this radio communication system. However, even when received data contains errors and data is retransmitted, if a time variation of an environment of a propagation path which a transmission signal follows is slow (see FIG.1), for example, when the communication apparatus is at rest or moving at a low speed, the diversity gain obtained with reception power on the receiving side is small, and therefore there is aproblemthat the throughput of the radio communication system hardly improves even if data is retransmitted. This is because when the time variation of the propagation path environment is slow, a signal whose reception level is low at the time of initial transmission also has a low transmission level at the time of data retransmission, and therefore data cannot be demodulated correctly even if the data at the time of initial transmission and data at the time of retransmission are combined. Furthermore, when a multi-antenna technology such as MIMO or STC (Space-Time Coding) is used, if the time variation of the propagation path environment is slow, there is little variation in the fading condition between initial transmission and data retransmission, and the combined data cannot be demodulated correctly. Disclosure of Invention It is an object of the present invention to increase a diversity gain obtained through data retransmission when data retransmission is controlled by a radio communication system (e.g., adaptive array antenna technology, MIMO technology, STC technology, etc.) which transmits a plurality of data streams using a plurality of antennas. This object is attained through a radio transmission apparatus and a radio transmission method which artificially changes the environment of a propagation path which data streams follow after the transmission from that at the time of previous transmission. Brief Description of Accompanying Drawings FIG.1 illustrates reception power on a receiving side when a time variation of an environment of a propagation path which a transmission signal follows is slow; FIG.2 is a block diagram showing a configuration of a radio transmission apparatus according to Embodiment 1 of the present invention; FIG. 3 is a block diagram showing a configuration of a radio reception apparatus according to Embodiment 1 of the present invention; FIG. 4 is a sequence diagram showing a flow of radio communication according to Embodiment 1 of the present invention; FIG.5A illustrates weights multiplied on transmission signals by a weight control section; FIG.5B illustrates weights multiplied on transmission signals by the weight control section; FIG. 6 is a conceptual view illustrating directivity of a transmission signal; FIG.7A illustrates quality on the receiving side of a signal transmitted from a conventional radio transmission apparatus; FIG.7B illustrates quality on the receiving side of a signal transmitted from the conventional radio transmission apparatus; FIG.8A illustrates quality on the receiving side of a signal transmitted from the radio transmission apparatus according to Embodiment 1 of the present invention; FIG.8B illustrates quality on the receiving side of a signal transmitted from the radio transmission apparatus according to Embodiment 1 of the present invention; FIG.9 is a block diagram showing a configuration of a radio transmission apparatus according to Embodiment 2 of the present invention; FIG.10A illustrates a delay time of a transmission signal for each transmission system; FIG.10B illustrates a delay time of a transmission signal for each transmission system; FIG.11 illustrates transmission timings of a transmission signal;- FIG.12A illustrates reception power of a conventional apparatus; FIG.12B illustrates reception power of the conventional apparatus; FIG.12C illustrates reception power of the conventional apparatus; FIG.13A illustrates reception power according to Embodiment 2 of the present invention; FIG.13B illustrates reception power according to Embodiment 2 of the present invention; and FIG.13C illustrates reception power according to Embodiment 2 of the present invention. Best Mode for Carrying out the Invention The present invention assumes roughly two cases for a method of changing a propagation path environment of a transmission signal. A first case is a method of changing weights to be multiplied on the transmission signal and a second case is a method of changing timings for transmitting the transmission signal. With reference now to the attached drawings, embodiments of the present invention will be explained in detail below. Note that Embodiment 1 describes a case where a weight to be multiplied on a transmission signal is changed and Embodiment 2 describes a case where a timing for transmitting a transmission signal is changed. (Embodiment 1) FIG.2 is a block diagram showing a configuration of a radio transmission apparatus according to Embodiment 1 of the present invention. Here, a case where two streams; data stream lAand data stream #B are transmitted using two antennas will be explained as an example. The radio transmission apparatus shown in FIG.2 is provided with buffers 101, modulation sections 102, multipliers 103, addition sections 104, transmission radio (RF) sections 105, transmission antennas 106, a retransmission count detection section 110, a buffer control section 111 and a weight control section 112. In FIG.2, the data stream #A is input to the buffer 101-1 and the data stream #B is input to the buffer 101-2. The buffers 101-1 and 101-2 store the input data streams in preparation for a data retransmission request from a radio reception apparatus. Then, upon reception of an instruction for data transmission from the buffer control section 111, the buffers 101-1 and 101-2 output the data to the modulation sections 102-1 and 102-2. The modulation section 102-1 carries out modulation processing on the data stream output from the buffer 101-1 and outputs the data stream. The signal output from the modulation section 102-1 is branched at some midpoint and output to the multipliers 103-1 and 103-2. Likewise, the modulation section 102-2 carries out modulation processing on the data stream output from the buffer 101-2 and outputs the data stream. The signal output from the modulation section 102-2 is branched at some midpoint and output to the multipliers 103-3 and 103-4. The multiplier 103-1 multiplies the signal output from the modulation section 102-1 by a weight output from the weight control section 112 and outputs the weighted signal to addition section 104-1 . On the other hand, the multiplier 103-2 multiplies the signal output from the modulation section 102-1 by a weight output from the weight control section 112 and outputs the weighted signal to addition section 104-2. Likewise, the multiplier 103-3 multiplies the signal output from the modulation section 102-2 by a weight output from the weight control section 112 and outputs the weighted signal to addition section 104-1. On the other hand, the multiplier 103-4 multiplies the signal output from the modulation section 102-2 by a weight output from the weight control section 112 and outputs the weighted signal to addition section 104-2. The weights multiplied on the signals by the multipliers 103-1 to 103-4 will be described in more detail later. The addition section 104-1 adds up the weighted signals output from the multipliers 103-1 and 103-3 and outputs the addition result to the transmission radio section 1 05-1. Likewise, the addition section 1 04-2 adds up the weighted signals output from the multipliers 103-2 and 103-4 and outputs the addition result to the transmission radio section 105-2. The transmission radio section 105-1 carries out predetermined radio transmission processing such as up-conversion on the signal output from the addition section 104-1, converts the signal to a radio signal and sends the radio signal through the antenna 106-1. On the other hand, the transmission radio section 105-2 likewise carries out radio transmission processing on the signal output from the addition section 104-2 and sends the signal through the antenna 106-2. The radio reception apparatus which has received the signals sent from the antennas 106-1 and 106-2 carries out error detection on the received signals and sends a NACK signal to the radio transmission apparatus according to this embodiment when an error is detected or sends an ACK signal when no error is detected. The retransmission count detection section 110 detects a retransmission count of the data from the ACK/NACK signal notified from the above described radio reception apparatus and outputs the retransmission count to the buffer control section 111. The buffer control section 111 outputs control signals of data output to the buffers 101-1 and 101-2 based on the retransmission count output from the retransmission count detection section 110. More specifically, when the radio reception apparatus sends a data retransmission request, the buffer control section 111 controls the buffers 101-1 and 101-2 so as to output the data stored at the time of the previous transmission again. The weight control section 112 includes a table storing a plurality of types of weights, selects a weight to be multiplied on a transmission signal from the table according to the retransmission count detected by the retransmission count detection section 110 and outputs the weight to the multiplier 103. When data is retransmitted, it references the weight table again and outputs weights different from those at the time of initial transmission to the multipliers 103-1 to 103-4. FIG.3 is a block diagram showing a configuration of a radio reception apparatus according to this embodiment. This radio reception apparatus is provided with reception antennas 151, reception radio (RF) sections 152, a MIMO reception section 153, buffers 154, demodulation sections 155, error detection sections 156, ACK/NACK signal generation sections 157 and retransmission count detection sections 158. InFIG.3, the reception radio (RF) sections 152 carry out predetermined radio processing such as down-conversion on signals received through the reception antennas 151 and outputs the signals to the MIMO reception section 153 . The MIMO reception section 153 separates the signals output from the reception radio sections 152 into two substreams, that is, streams #A and #B (MIMO reception processing) using propagation path characteristic information and outputs the streams to the respective buffers 154. This MIMO reception processing causes an inverse matrix of a matrix of 2 rows x 2 columns consisting of characteristics of propagation paths which the respective signals sent from the two antennas on the transmitting side follow as elements to act on the received signals to thereby obtain two substreams. In the case of packet data at the time of initial transmission, the buffers 154 immediately output this data to the demodulation sections 155. When a retransmission packet is sent, this data is temporarily stored and demodulated. When the packet is received correctly and an ACK signal is returned, the buffers are cleared. Being notified of the retransmission count from the retransmission count detection section 158, the buffer 154 can decide whether the packet is sent at the time of initial transmission or at the time of retransmission. The demodulation sections 155 carry out demodulation processing on the data streams output from the buffers 154 and obtain data stream #A and data stream #B. The error detection sections 156 detect errors and notify to the ACK/NACK signal generation sections 157 of the errors. When notified from the error detection section 156 that an error has been detected, the ACK/NACK signal generation sections 157 generate a NACK signal and send the NACK signal to the radio transmission apparatus and retransmission count detection section 158 or when notified from the error detection sections 156 that no error has been detected, the ACK/NACK signal generation sections 157 send an ACK signal to the radio transmission apparatus and retransmission count detection section 158 . FIG. 4 is a sequence diagram showing a flow of radio communication realized by the above described configuration. When sending a data stream, the transmission apparatus decides a weight to be multiplied on the transmission signal for each transmission system first (ST1010). Then, the transmission apparatus multiplies the transmission signal by this weight (ST1020) and sends a data stream (ST1030). The reception apparatus receives the data stream sent from the above described transmission apparatus (ST1040) and detects a data error (ST1050) . When some error is detected, the reception apparatus generates a NACK signal (ST1060) and sends the NACK signal to the above described transmission apparatus (ST1070). The transmission apparatus which has detected the NACK signal notified from the reception apparatus (ST1080) changes the weight decided in ST1010 for each transmission system (ST1090), multiplies it on the transmission signal to be retransmitted (ST1100) and retransmits this signal to the reception apparatus (ST1110) . Then, an example of weights multiplied on a transmission signal under the control of the weight control section 112 will be explained using FIG.5A and FIG.5B. FIG.5A illustrates weights to be multiplied on transmission signals arranged for data stream #A(SA) and data stream #B(SB) . For example, at the time of initial transmission of data, stream #A is multiplied by weight wa for the transmission system on the antenna 106-1 (hereinafter referred to as "antenna #1") side and multiplied by weight wp for the transmission system on the antenna 106-2 (hereinafter referred to as "antenna #2") . Furthermore, stream #B is multiplied by weight wy for the transmission system on the antenna #1 side and multiplied by weight wδ for the transmission system on the antenna #2 side. Then, at the first retransmission, stream #A is multiplied by weight wγ for the transmission system on the antenna #1 side and multiplied by weight wδ for the transmission system on the antenna #2 side. Furthermore, stream #B is multiplied by weight wα for the transmission system on the antenna #1 and multiplied by weight wβ for the transmission system on the antenna #2 side That is, here, the weight used for the data stream #A at the time of initial transmission is used for the data stream #B for the first retransmission. Furthermore, the weight used for the data stream #B at the time of initial transmission is used for the data stream #A for the first retransmission. At the time of the initial transmission and first retransmission, weights used for the stream #A and stream #B are switched round. At the second retransmission, weights used for the stream #A and stream #B are switched round and the same weights as those at the time of initial transmission are used. At the third retransmission, weights used for the stream #A and stream #B are further switched round and the same weights as those at the first retransmission areused. Thatis, every time retransmission is repeated, weights used for the stream #A and stream #B are switched round. Here, weights to be multiplied on transmission signals arranged for the antenna #1 and antenna #2 from the different standpoint are shown in FIG.5B. That is, this figure shows what signals are actually sent from the antenna #1 and antenna #2. The contents shown in FIG.5A and FIG.5B are substantially the same. Then, effects resulting from changes of weights between the initial transmission and retransmission will be explained. When a weight is multiplied on a transmission signal, the transmission signal acquires directivity. However, this directivity does not mean that the transmission signal is actually propagating in a specific direction as seen in the formation of beams by an array antenna technology, but it is a matter of mathematical expressions. This is because while there is a low fading correlation between antennas in the MIMO communication, there is a high fading correlation between antennas in the array antenna technology. However, this expression is used in studying effects of weight multiplication of this embodiment because explaining with an image that a transmission signal is actually propagating with directivity facilitates an understanding. FIG. 6 is a conceptual view illustrating directivity of a transmission signal. Signals sent from a radio transmission apparatus 100 using weights wα and wβ follow a path #1 represented by a thick line, are reflected at some midpoint by a building 191 and reach a radio reception apparatus 150 without any significant reduction of their intensity. On the other hand, signals sent using weights wγ and wδ follow a path#2 represented by a thin line, are reflected at some midpoint by a building 192 and reach the radio reception apparatus 150 affected by the propagation path with their intensity significantly weakened. At the time of initial transmission, the stream #A multiplied by weights wα and wβ follows the path #1 and the stream #B multiplied by weights wα and wβ follows the path #2. Then, at the time of retransmission the weights to be multiplied on the transmission signals are switched round, and therefore the stream #A follows the path #2 and the stream #B follows the path #1. FIG.7A, FIG.7B, FIG.8A and FIG.8B show quality comparisons between signals sent from a conventional radio transmission apparatus and signals sent from the radio transmission apparatus according to this embodiment These figures show conceptual views illustrating the quality (bar graphs) of received signals after being combined on the receiving side and a level L1 at which data can be received correctly. FIG.7A and FIG.7B show cases of the conventional radio transmission apparatus. FIG.7A illustrates reception quality at the time of initial transmission and FIG.7B illustrates reception quality at the time of data retransmission. In FIG.7A, the quality level of the received signal of none of the stream #A and the stream #B exceeds the level L1. At this time, the receiving side cannot receive data correctly, and therefore sends back a NACK signal to the transmitting side and the transmitting side retransmits the data. However, when the time variation of the propagation path environment is small, no significant improvement of the reception quality on the receiving side can be expected even at the time of data retransmission. Thus, as shown in FIG.7B, by combining the received signal at the time of initial transmission and the received signal at the time of data retransmission after the data retransmission, the reception quality after the combination of the stream #A which had original reception quality at a level close to the level L1 at the time of initial transmission exceeds the level L1. On the other hand, even if data is retransmitted, the reception quality of the stream #B after the combination cannot exceed the level L1. Thus, the receiving side sends back an NACK signal to the transmitting side several times more until the reception quality of the stream #B exceeds the level L1 and the transmitting side retransmits data every time the NACK signal is sent. FIG.8A and FIG.8B show the case of the radio transmission apparatus according to this embodiment. FIG.8A illustrates reception quality at the time of initial data transmission and FIG.8B illustrates reception quality at the time of data retransmission. FIG.8A is the same as FIG.7A. None of the reception quality levels of the stream #A and stream #B exceeds the level L1. However, at the time of retransmission, weights used for the stream #A and stream #B are switched round, and therefore the environments of propagation paths which the stream #A and stream #B follow are placed in a condition as if those environments are averaged. In this way, both the reception quality levels of the streams #A and #B after combining the received signals at the time of initial transmission and at the time of retransmission exceed the level L1, and it is therefore possible to receive signals correctly. In the above described configuration, the weight control section 112 of the radio reception apparatus according to this embodiment changes weights to be multiplied on the transmission signal from the weights used for the previous transmission every time data is retransmitted. This causes each data stream to be sent to the receiving side through different propagation path environments between the previous transmission and retransmission, and therefore the probability that the same data may contain errors successively is reduced and as a result, the data error rate characteristic after packet combination improves . In other words, adiversity gain when the retransmission data is combined on the receiving side increases and the reception performance on the receiving side improves. Furthermore, the weight control section 112 of the radio reception apparatus according to this embodiment switches round the weights corresponding to the respective antennas at the time of the previous transmission and multiplies the transmission signals by those weights every time data is retransmitted. For example, as shown in FIG.7A or FIG.8A, even if the receiving side sends back a NACK signal at the time of initial transmission, reception quality of all data streams is not averagely bad but it is often the case that reception quality of only some data streams is bad. At this time, by switching round weights to be multiplied on the transmission signals between previous transmission and retransmission, the propagation path environments for the respective data streams are switched round and averaged, and therefore the reception quality improves at an early stage. Furthermore, since the weights already used at the time of the previous transmission are reused at the time of retransmission by only switching round the signals to be multiplied, and therefore there is no need for processing such as feeding back other information, for example, the propagation path information detected on the receiving side to the transmitting side. Thus, according to this embodiment, weights to be multiplied on transmission signals are switched round between the initial transmission and retransmission, and therefore it is possible to increase a diversity gain obtained through data retransmission and improve reception performance on the receiving side. Note that here a case where transmission data consists of two streams #A and #B has been explained as an example, but the number of data streams can be three or more, and in this case, it is possible to use weights to be used at the time of data retransmission in rotation every time data is retransmitted. That is, in the case of three data streams, the weights used at the time of the initial transmission are reused at the third retransmission. Furthermore, here, a MIMO transmission having a low fading correlation between antennas has been explained, but it is also possible to use an array antenna having a high fading correlation between antennas . At this time, antennas are arranged so that the fading correlation between antennas becomes substantially 1. Directivity patterns as shown in FIG.6 are formed by multiplying transmission signals by weights. The stream #A multiplied by weights wα and wβ at the time of the initial transmission follows the path #1 and the stream #B multiplied byweights wα and wβ follows the path #2. Then, at the time of retransmission, weights to be multiplied on the transmission signals are switched round, and therefore the stream #A follows the path #2 and the stream #B follows the path #1 . This makes it possible to average propagation path environments as with the above described case . Here, a case whereweights of the stream #A and stream #B are switched round at the time of data retransmission has been explained as an example, but it is also possible to select not the weights used at the time of the previous transmission but totally different values as weights for retransmission. Furthermore, here a case where the propagation path information, etc., detected on the receiving side is not fed back to the transmitting side has been explained as an example, but for a radio transmission apparatus in which channel quality information is fed back from the receiving side to the transmitting side for the purpose of increasing the channel capacity and weights are decided so that more power is assigned to channels of good quality, it is also possible to fine-tune weights based on this fed back channel quality information and assign weights so that the channel quality exceeds the minimum level L1 in all paths. (Embodiment 2) FIG.9 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.2 and the same components are assigned the same reference numerals and explanations thereof will be omitted. Features of this embodiment include that it is provided with IFFT sections 201, delay sections 202 and a delay control section 203, it carries out a communication based on an OFDM scheme, adds delay times which differ from one transmission data stream to another, transmits the data streams through their respective antennas at different transmission timings at the time of transmission and thereby drastically changes the characteristic of a received signal on the frequency axis. Therefore, it is possible to drastically change the propagation path environment every time retransmission is performed. Furthermore, transforming data into a multicarrier according to the OFDM scheme makes it possible to multiplex delay signals with different delay times and send the multiplexed signals. Then, an operation of the radio transmission apparatus in the above described configuration will be explained. The modulation section 102-1 carries out modulation processing on a data stream output from the buffer 101-1 and outputs the data stream. The signal output from the modulation section 102-1 is branched at some midpoint and output to the IFFT sections 201-1 and 2 01-2 . Likewise the modulation section 102-2 carries out modulation processing on a data stream output from the buffer 101-2 and outputs the data stream. The signal output from the modulation section 102-2 is branched at some midpoint and output to the IFFT sections 201-3 and 201-4. On the other hand, the delay control section 203 includes a table storing a plurality of types of delay times, selects a delay time for each transmission signal from the table according to a retransmission count notified from the retransmission count detection section 110 and outputs the delay time to the delay sections 202-1 to 202-4. The delay times output from the delay control section 203 will be explained in more detail later. The delay section 202-1 delays the transmission timing of the signal output from the IFFT section 201-1 by a delay time output from the delay control section 203 and outputs the delayed signal to the addition section 104-1. Furthermore, the delay section 202-2 delays the transmission timing of the signal output from the IFFT section 2 01-2 by a delay time output from the delay control section 203 and outputs the delayed signal to the addition section 104-2. Likewise, the delay section 202-3 delays the transmission timing of the signal output from the IFFT section 2 01-3 by a delay time output from the delay control section 203 and outputs the delayed signal to the addition section 104-1. Furthermore, the delay section 202-4 delays the transmission timing of the signal output from the IFFT section 201-4 by a delay time output from the delay control section 203 and outputs the delayed signal to the addition section 104-2. The addition section 104-1 adds up the signals output from the delay sections 202-1 and 202-3, the transmission timings of which have been delayed and outputs the addition result to the transmission radio section 105-1 . Likewise, the addition section 104-2 adds up the signals output from the delay sections 202-2 and 202-4, the transmission timings of which have been delayed and outputs the addition result to the transmission radio section 105-2. The processing thereafter is the same as that in Embodiment 1 . Then, an example of a delay time added to a transmission signal of each system will be explained using FIG.10A and FIG.10B. FIG.10A shows delay times of transmission timings of transmission signals arranged for data stream #A(SA) and data stream #B(SB). For example, at the time of initial data transmission, the delay time of the stream #A is 0 for the transmission system on the antenna #1 side and Τ α for the transmission system on the antenna #2 side. Furthermore, the delay time of the stream #B is 0 for the transmission system on the antenna #1 side and τ β for the transmission system on the antenna #2 side . Then, at the first retransmission, the delay time of the stream #A is 0 for the transmission system on the antenna #1 side and τ β for the transmission system on the antenna #2 side. Furthermore, the delay time of the stream #B is 0 for the transmission system on the antenna #1 side and τ α for the transmission system on the antenna #2 side. That is, the combination of delay times of the data stream #Aat the time of the initial transmission is applied to the data stream #B at the time of the first retransmission. Furthermore, the combination of delay times used for the data stream #B at the time of the initial transmission is applied to the data stream #A at the first retransmission. The combinations of delay times used for the stream #A and stream #B at the time of the initial transmission are switched round at the time of the first retransmission. At the time of 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 the initial transmission are switched round. That is, the delay time of the stream #A is Τ α for the transmission system on the antenna #1 side and 0 for the transmission system on the antenna #2 side, and the delay time of the stream #B is Τ β for the transmission system on the antenna #1 side and 0 for the transmission system on the antenna #2 side. At the third retransmission, the delay times used for the stream #A and stream #B are further switched round. Now, by changing the standpoint, delay times of transmission signals arranged for the antenna #1 and antenna #2 are shown in FIG.10B. That is, this figure shows how signals are actually delayed and sent through the antenna #1 and antenna #2. The contents shown in FIG.10A and FIG.10B are substantially the same. FIG.11 shows transmission timings of signals transmitted from the above described radio transmission apparatus on the time axis. Note that the actual transmi ssion data streams are weighted (e.g., the signals transmitted from the antenna #1 are wαSA+wγSB as described above) , but the same weights at the time of the initial transmission are also used at the time of the retransmission in this embodiment, and therefore notations of weights will be omitted to make it easier to distinguish one signal from another. This figure shows that initial data transmission is performed at time 0 and data retransmission is performed at time t1 afteralapseof acertaintime. From the antenna #1, data stream #A (SA, S'A) and data stream #B (SB, S'B) are transmitted at the same timing for both the initial transmission and retransmission . On the other hand, from the antenna #2, SA and SB are transmitted with delay times Τ α, and Τ β, respectively at the time of initial transmission, while S'A and S'B are transmitted with delay times Τ β and Τ α, respectively at the time of retransmission. Here, when attention is focused on the data stream #A(SA) at the time of the initial transmission, SA is transmitted with a time difference Τ α provided between the antenna #1 and antenna #2. This is intended to reduce a fading correlation between the antennas. On the other hand, when attention is focused on the data stream #A(S'A) at the time of the retransmission, the time difference providedbetween the antenna #1 and antenna #2 is z p. That is, transmission is carried out in such a way that the fading correlation between the antennas is changed at the time of the initial transmission and at the time of the retransmission. The also applies to the data stream #B(SB, S'B) in like fashion. Furthermore, when attention is focused on both SA and SB transmitted from the antenna #2 at the time of the initial transmission, SB is transmitted ( Τ β-Τα) behind SA. On the other hand, at the time of the retransmission, S'A is transmitted (Τ β-Τα) behind S'B on the contrary. This means that transmission is carried out in such a way that the difference in transmission timings between the data stream #A and data stream #B (including the relationship as to which is ahead and which is behind) is changed at the time of the initial transmission and at the time of the retransmission. Here, for simplicity of explanation, attention has been focused only on the data stream transmitted from the antenna #2, but the same thing is also applied when the data stream transmitted from the antenna #1 is taken into consideration together. The effect of changing the difference in transmission timings between data streams at the time of the initial transmission and at the time of the retransmission will be explained below. Speaking plainly, frequency selective fading is a result of signals with the same frequency and a phase difference of 180 degrees weakening each other. Thus, by intentionally delaying transmission timings of transmission signals, that is, shifting phases, it is possible to change a fading characteristic that a signal receives. FIG.12A to FIG.12C show reception power at a conventional apparatus . A stream #A keeps a high reception level both at the time of initial transmission (see FIG.12A) and at the time of retransmission (see FIG.12B), while a stream #B keeps a low reception level both at the time of initial transmission and at the time of retransmission. Therefore, even if the data at the time of the initial transmission and the data at the time of the retransmission are combined (see FIG.12C), only the stream #A reaches the level for correct reception and the stream #B remains at levels where it cannot be received correctly. FIG.13A to FIG.13C show reception power according to this embodiment. The levels of received signals are affected by frequency selective fading which differs between the streams. Therefore, the pattern of the reception level on the frequency axis differs between the streams. At the time of initial transmission (see FIG.13A) and at the time of retransmission ( see FI G . 1 3B ) , delay processes applied to the stream #A and stream #B are switched round, and therefore the levels of signals after being combined on the receiving side are averaged (see FIG.13C) and both the stream #A and stream #B can be demodulated correctly. Here, the figures describe a situation in which the phase of the fading characteristic curve on the frequency axis is shifted by 180 degrees by delaying transmission signals. However, it will be sufficient to change the fading characteristic only to a certain degree by delaying transmission signals in this embodiment, and the phase need not always be shifted by 180 degrees. Note that the fluctuation pitch of the fading characteristic depends on the moving speed of a mobile station and the frequency band used for communications , and therefore it is possible to calculate a delay time for shifting the phase of the fading characteristic curve by 180 degrees. Furthermore, when the propagation path information such as channel quality is fed back from the receiving side to the transmitting side in the above described configuration as in the case of Embodiment 1, it is also possible to fine-tune delay times based on this fed back propagation path information. Thus, according to this embodiment, variations in the reception level are averaged on the frequency axis of each stream for every retransmission, and therefore it is possible to demodulate the combined signal correctly and improve the reception performance on the receiving side . Note that Embodiment 1 and Embodiment 2 can be used in combination. That is, it is possible to further add a delay time to a transmission signal multiplied by a weight to delay the transmission timing and transmit the delayed signal. At this time, the effects of the respective embodiments are superimposed, making it possible to further improve the reception performance. As described above, the present invention allows a radio communication system which transmits a plurality of data streams using a plurality of antennas (e.g., adaptive array antenna technology, MIMO technology, STC technology, etc.) to increase, for example, when HARQ is applied, a diversity gain at the time of data retransmission and improve the reception performance on the receiving side. This application is based on the Japanese Patent Application No.2002-268968 filed on September 13, 2002, entire content of which is expressly incorporated by reference herein. Industrial Applicability The present invention is applicable to a radio transmission apparatus and radio transmission method to which an adaptive array antenna technology, MIMO technology or STC technology, etc., is applied. We Claim: 1. A radio transmission apparatus comprising: a multiplication section (103-1, 103-2, 103-3, 103-4) that multiplies a plurality of data streams (#A,#B) by a plurality of weights (Wα, Wβ, Wγ, Wδ) respectively; a transmission section (105-1, 105-2) that transmits the plurality of weighted data streams from a plurality of transmission antennas (106-1, 106-2) simultaneously; and a control section (112) that controls said multiplication section (103-1, 103-2, 103-3, 103-4) so that at the time of retransmission of said plurality of data streams (#A,#B), said plurality of data streams is multiplied by weights (Wα, Wβ, Wγ, Wδ) different from the weights (Wα, Wβ, Wγ, Wδ) at the time of previous transmission, characterized in that said control section (112) selects weights (Wα, Wβ, Wγ, Wδ) at the time of the retransmission from among a plurality of weights (Wα, Wβ, Wγ, Wδ) corresponding to said plurality of data streams (#A,#B) at the time of the previous transmission. 2. The radio transmission apparatus as claimed in claim 1, wherein said control section (112) performs said control based on propagation path information notified from the receiving side. 3. The radio transmission apparatus as claimed in one of claims 1 or 2, wherein said transmission is diversity transmission. 4. The radio transmission apparatus as claimed in one of claims 1 to 3, wherein said plurality of data streams (#A,#B) is transformed into a multicarrier beforehand. 5. The radio transmission apparatus as claimed in claim 4, wherein said transformation into a multicarrier is OFDM (orthogonal Frequency Division Multiplex) processing. 6. A radio transmission method comprising: a multiplication step (ST1020) of multiplying a plurality of data streams (#A,#B) by a plurality of weights (Wα, Wβ, Wγ, Wδ) respectively; a transmission step (ST1030) of simultaneously transmitting the plurality of weighted data streams from a plurality of transmission antennas (106-1,106-2); and a control step (ST1090) of performing control so that at the time of retransmission of said plurality of data streams (#A,#B), said plurality of data streams (#A,#B) is multiplied by weights (Wα, Wβ, Wγ, Wδ ) different from the weights (Wα, Wβ, Wγ, Wδ ) at the time of previous transmission respectively, characterized in that said control step selects weights (Wα, Wβ, Wγ, Wδ) at the time of the retransmission from among a plurality of weights (Wα, Wβ, Wγ, Wδ) corresponding to said plurality of data streams (#A,#B) at the time of the previous transmission. The invention relates to a radio transmission apparatus comprising a multiplication section (103-1, 103-2, 103-3, 103-4) that multiplies a plurality of data streams (#A,#B) by a plurality of weights (Wα, Wβ, Wγ, Wδ) respectively; a transmission section (105-1, 105-2) that transmits the plurality of weighted data streams from a plurality of transmission antennas (106-1, 106-2) simultaneously; and a control section (112) that controls said multiplication section (103-1, 103- 2, 103-3, 103-4) so that at the time of retransmission of said plurality of data streams (#A,#B) said plurality of data streams is multiplied by weights (Wα, Wβ, Wγ, Wδ) different from the weights (Wα, Wβ, Wγ, Wδ) at the time of previous transmission. The said control section (112) selects weights (Wα, Wβ, Wγ, Wδ) at the time of the retransmission from among a plurality of weights (Wα, Wβ, Wγ, Wδ) corresponding to said plurality of data streams (#A,#B) at the time of the previous transmission.

Full Text

DESCRIPTION
RADIO TRANSMISSION APPARATUS
AND RADIO TRANSMISSION METHOD
Technical Field
The present invention relates to a radio
transmission apparatus and radio transmission method.
Background Art
As a technology for realizing communications of
large-volume data such as images, MIMO (Multi-Input
Multi-Output) communications are being studied actively
in recent years.
Among them, BLAST (Bell Laboratories Layered
Space-Time) in particular is a focus of attention as an
application capable of realizing high-speed transmission
using an MIMO channel. This is a technique for
transmittingmutuallyindependent (or coded) streams from
a plurality of transmission antennas and detecting the
respective streams while repeating spatial filtering and
removal of replicas on the receiving side.
Furthermore, when the MIMO channel information is
known to the transmitting side, it is known that a greater
channel capacity can be obtained. More specifically,
this is realized by carrying out directivity control using
an eigen vector obtained through singular value
decomposition of a matrix which consists of the respective

channel responses of the MIMO channels as elements and
forming a spatially orthogonal channel (eigen channel).
That is, when the MIMO channel information is known to
the transmitting side, it is possible to form an orthogonal
channel through multi-beam formation using the eigen
vector, performing transmit power control through an
irrigation theorem and thereby maximize the channel
capacity (e.g., TECHNICAL REPORT OF IEICE RCS2002-53
(2002-05), Institute of Electronics, Information and
Communication Engineers).
When the above described technology is applied to
an actual apparatus, radio transmission is carried out
after preparing a plurality of transmission systems
capable of carrying out transmission processing on a
plurality of transmission data streams and assigning
weights by multiplying the transmission signals by their
respective complex weights (hereinafter simply referred
to as "weights").
When a bit error rate on the receiving side does
not satisfy a predetermined value, an automatic
retransmission request (ARQ; Automatic Repeat reQuest)
is also generally practiced whereby the receiving side
sends a retransmission request signal to the transmitting
side and the transmitting side retransmits the same
transmission data in response to this request.
Especiallypacket transmission which transmits data
traffic is required to guarantee error-free data
transmission, and therefore error control through ARQ

is indispensable. In addition, when an adaptive
modulation and error correction intended to improve the
throughput by selecting an optimal modulation system or
coding system according to the condition of a propagation
path (path)are applied to packet transmission, it is not
possible to avoid measuring errors or packet errors caused
by a control delay, etc., and therefore the 3GPP (3rd
Generation Partnership Project) also standardizes the
use of a hybrid ARQ (hereinafter referred to as "HARQ")
which incorporates an FEC (Forward Error Correction)
function.
Therefore, by carrying out an MIMO communication
using a plurality of antennas during data transmission
to realize a large-volume data communication and
retransmitting data when received data contains errors
on the receiving side and by combining received data at
the time of initial transmission with the received data
at the time of retransmission using HARQ on the receiving
side, a considerable improvement of throughput can be
expected for this radio communication system.
However, even when received data contains errors
and data is retransmitted, if a time variation of an
environment of a propagation path which a transmission
signal follows is slow (see FIG.1), for example, when
the communication apparatus is at rest or moving at a
low speed, the diversity gain obtained with reception
power on the receiving side is small, and therefore there
is aproblemthat the throughput of the radio communication

system hardly improves even if data is retransmitted.
This is because when the time variation of the
propagation path environment is slow, a signal whose
reception level is low at the time of initial transmission
also has a low transmission level at the time of data
retransmission, and therefore data cannot be demodulated
correctly even if the data at the time of initial
transmission and data at the time of retransmission are
combined. Furthermore, when a multi-antenna technology
such as MIMO or STC (Space-Time Coding) is used, if the
time variation of the propagation path environment is
slow, there is little variation in the fading condition
between initial transmission and data retransmission,
and the combined data cannot be demodulated correctly.
Disclosure of Invention
It is an object of the present invention to increase
a diversity gain obtained through data retransmission
when data retransmission is controlled by a radio
communication system (e.g., adaptive array antenna
technology, MIMO technology, STC technology, etc.) which
transmits a plurality of data streams using a plurality
of antennas.
This object is attained through a radio transmission
apparatus and a radio transmission method which
artificially changes the environment of a propagation
path which data streams follow after the transmission
from that at the time of previous transmission.

Brief Description of Accompanying Drawings
FIG.1 illustrates reception power on a receiving
side when a time variation of an environment of a
propagation path which a transmission signal follows is
slow;
FIG.2 is a block diagram showing a configuration
of a radio transmission apparatus according to Embodiment
1 of the present invention;
FIG. 3 is a block diagram showing a configuration
of a radio reception apparatus according to Embodiment
1 of the present invention;
FIG. 4 is a sequence diagram showing a flow of radio
communication according to Embodiment 1 of the present
invention;
FIG.5A illustrates weights multiplied on
transmission signals by a weight control section;
FIG.5B illustrates weights multiplied on
transmission signals by the weight control section;
FIG. 6 is a conceptual view illustrating directivity
of a transmission signal;
FIG.7A illustrates quality on the receiving side
of a signal transmitted from a conventional radio
transmission apparatus;
FIG.7B illustrates quality on the receiving side
of a signal transmitted from the conventional radio
transmission apparatus;
FIG.8A illustrates quality on the receiving side

of a signal transmitted from the radio transmission
apparatus according to Embodiment 1 of the present
invention;
FIG.8B illustrates quality on the receiving side
of a signal transmitted from the radio transmission
apparatus according to Embodiment 1 of the present
invention;
FIG.9 is a block diagram showing a configuration
of a radio transmission apparatus according to Embodiment
2 of the present invention;
FIG.10A illustrates a delay time of a transmission
signal for each transmission system;
FIG.10B illustrates a delay time of a transmission
signal for each transmission system;
FIG.11 illustrates transmission timings of a
transmission signal;-
FIG.12A illustrates reception power of a
conventional apparatus;
FIG.12B illustrates reception power of the
conventional apparatus;
FIG.12C illustrates reception power of the
conventional apparatus;
FIG.13A illustrates reception power according to
Embodiment 2 of the present invention;
FIG.13B illustrates reception power according to
Embodiment 2 of the present invention; and
FIG.13C illustrates reception power according to
Embodiment 2 of the present invention.

Best Mode for Carrying out the Invention
The present invention assumes roughly two cases for
a method of changing a propagation path environment of
a transmission signal. A first case is a method of
changing weights to be multiplied on the transmission
signal and a second case is a method of changing timings
for transmitting the transmission signal.
With reference now to the attached drawings,
embodiments of the present invention will be explained
in detail below. Note that Embodiment 1 describes a case
where a weight to be multiplied on a transmission signal
is changed and Embodiment 2 describes a case where a timing
for transmitting a transmission signal is changed.
(Embodiment 1)
FIG.2 is a block diagram showing a configuration
of a radio transmission apparatus according to Embodiment
1 of the present invention. Here, a case where two
streams; data stream lAand data stream #B are transmitted
using two antennas will be explained as an example.
The radio transmission apparatus shown in FIG.2 is
provided with buffers 101, modulation sections 102,
multipliers 103, addition sections 104, transmission
radio (RF) sections 105, transmission antennas 106, a
retransmission count detection section 110, a buffer
control section 111 and a weight control section 112.
In FIG.2, the data stream #A is input to the buffer

101-1 and the data stream #B is input to the buffer 101-2.
The buffers 101-1 and 101-2 store the input data
streams in preparation for a data retransmission request
from a radio reception apparatus. Then, upon reception
of an instruction for data transmission from the buffer
control section 111, the buffers 101-1 and 101-2 output
the data to the modulation sections 102-1 and 102-2.
The modulation section 102-1 carries out modulation
processing on the data stream output from the buffer 101-1
and outputs the data stream. The signal output from the
modulation section 102-1 is branched at some midpoint
and output to the multipliers 103-1 and 103-2. Likewise,
the modulation section 102-2 carries out modulation
processing on the data stream output from the buffer 101-2
and outputs the data stream. The signal output from the
modulation section 102-2 is branched at some midpoint
and output to the multipliers 103-3 and 103-4.
The multiplier 103-1 multiplies the signal output
from the modulation section 102-1 by a weight output from
the weight control section 112 and outputs the weighted
signal to addition section 104-1 . On the other hand, the
multiplier 103-2 multiplies the signal output from the
modulation section 102-1 by a weight output from the weight
control section 112 and outputs the weighted signal to
addition section 104-2.
Likewise, the multiplier 103-3 multiplies the
signal output from the modulation section 102-2 by a weight
output from the weight control section 112 and outputs

the weighted signal to addition section 104-1. On the
other hand, the multiplier 103-4 multiplies the signal
output from the modulation section 102-2 by a weight output
from the weight control section 112 and outputs the
weighted signal to addition section 104-2. The weights
multiplied on the signals by the multipliers 103-1 to
103-4 will be described in more detail later.
The addition section 104-1 adds up the weighted
signals output from the multipliers 103-1 and 103-3 and
outputs the addition result to the transmission radio
section 1 05-1. Likewise, the addition section 1 04-2 adds
up the weighted signals output from the multipliers 103-2
and 103-4 and outputs the addition result to the
transmission radio section 105-2.
The transmission radio section 105-1 carries out
predetermined radio transmission processing such as
up-conversion on the signal output from the addition
section 104-1, converts the signal to a radio signal and
sends the radio signal through the antenna 106-1. On the
other hand, the transmission radio section 105-2 likewise
carries out radio transmission processing on the signal
output from the addition section 104-2 and sends the signal
through the antenna 106-2.
The radio reception apparatus which has received
the signals sent from the antennas 106-1 and 106-2 carries
out error detection on the received signals and sends
a NACK signal to the radio transmission apparatus
according to this embodiment when an error is detected

or sends an ACK signal when no error is detected.
The retransmission count detection section 110
detects a retransmission count of the data from the
ACK/NACK signal notified from the above described radio
reception apparatus and outputs the retransmission count
to the buffer control section 111.
The buffer control section 111 outputs control
signals of data output to the buffers 101-1 and 101-2
based on the retransmission count output from the
retransmission count detection section 110. More
specifically, when the radio reception apparatus sends
a data retransmission request, the buffer control section
111 controls the buffers 101-1 and 101-2 so as to output
the data stored at the time of the previous transmission
again.
The weight control section 112 includes a table
storing a plurality of types of weights, selects a weight
to be multiplied on a transmission signal from the table
according to the retransmission count detected by the
retransmission count detection section 110 and outputs
the weight to the multiplier 103. When data is
retransmitted, it references the weight table again and
outputs weights different from those at the time of initial
transmission to the multipliers 103-1 to 103-4.
FIG.3 is a block diagram showing a configuration
of a radio reception apparatus according to this
embodiment.
This radio reception apparatus is provided with

reception antennas 151, reception radio (RF) sections
152, a MIMO reception section 153, buffers 154,
demodulation sections 155, error detection sections 156,
ACK/NACK signal generation sections 157 and
retransmission count detection sections 158.
InFIG.3, the reception radio (RF) sections 152 carry
out predetermined radio processing such as
down-conversion on signals received through the reception
antennas 151 and outputs the signals to the MIMO reception
section 153 .
The MIMO reception section 153 separates the signals
output from the reception radio sections 152 into two
substreams, that is, streams #A and #B (MIMO reception
processing) using propagation path characteristic
information and outputs the streams to the respective
buffers 154. This MIMO reception processing causes an
inverse matrix of a matrix of 2 rows x 2 columns consisting
of characteristics of propagation paths which the
respective signals sent from the two antennas on the
transmitting side follow as elements to act on the received
signals to thereby obtain two substreams.
In the case of packet data at the time of initial
transmission, the buffers 154 immediately output this
data to the demodulation sections 155. When a
retransmission packet is sent, this data is temporarily
stored and demodulated. When the packet is received
correctly and an ACK signal is returned, the buffers are
cleared. Being notified of the retransmission count from

the retransmission count detection section 158, the
buffer 154 can decide whether the packet is sent at the
time of initial transmission or at the time of
retransmission.
The demodulation sections 155 carry out
demodulation processing on the data streams output from
the buffers 154 and obtain data stream #A and data stream
#B.
The error detection sections 156 detect errors and
notify to the ACK/NACK signal generation sections 157
of the errors.
When notified from the error detection section 156
that an error has been detected, the ACK/NACK signal
generation sections 157 generate a NACK signal and send
the NACK signal to the radio transmission apparatus and
retransmission count detection section 158 or when
notified from the error detection sections 156 that no
error has been detected, the ACK/NACK signal generation
sections 157 send an ACK signal to the radio transmission
apparatus and retransmission count detection section 158 .
FIG. 4 is a sequence diagram showing a flow of radio
communication realized by the above described
configuration.
When sending a data stream, the transmission
apparatus decides a weight to be multiplied on the
transmission signal for each transmission system first
(ST1010). Then, the transmission apparatus multiplies
the transmission signal by this weight (ST1020) and sends

a data stream (ST1030).
The reception apparatus receives the data stream
sent from the above described transmission apparatus
(ST1040) and detects a data error (ST1050) . When some
error is detected, the reception apparatus generates a
NACK signal (ST1060) and sends the NACK signal to the
above described transmission apparatus (ST1070).
The transmission apparatus which has detected the
NACK signal notified from the reception apparatus
(ST1080) changes the weight decided in ST1010 for each
transmission system (ST1090), multiplies it on the
transmission signal to be retransmitted (ST1100) and
retransmits this signal to the reception apparatus
(ST1110) .
Then, an example of weights multiplied on a
transmission signal under the control of the weight
control section 112 will be explained using FIG.5A and
FIG.5B.
FIG.5A illustrates weights to be multiplied on
transmission signals arranged for data stream #A(SA) and
data stream #B(SB) . For example, at the time of initial
transmission of data, stream #A is multiplied by weight
wa for the transmission system on the antenna 106-1
(hereinafter referred to as "antenna #1") side and
multiplied by weight wp for the transmission system on
the antenna 106-2 (hereinafter referred to as "antenna
#2") . Furthermore, stream #B is multiplied by weight wy
for the transmission system on the antenna #1 side and

multiplied by weight wδ for the transmission system on
the antenna #2 side.
Then, at the first retransmission, stream #A is
multiplied by weight wγ for the transmission system on
the antenna #1 side and multiplied by weight wδ for the
transmission system on the antenna #2 side. Furthermore,
stream #B is multiplied by weight wα for the transmission
system on the antenna #1 and multiplied by weight wβ for
the transmission system on the antenna #2 side
That is, here, the weight used for the data stream
#A at the time of initial transmission is used for the
data stream #B for the first retransmission. Furthermore,
the weight used for the data stream #B at the time of
initial transmission is used for the data stream #A for
the first retransmission. At the time of the initial
transmission and first retransmission, weights used for
the stream #A and stream #B are switched round.
At the second retransmission, weights used for the
stream #A and stream #B are switched round and the same
weights as those at the time of initial transmission are
used. At the third retransmission, weights used for the
stream #A and stream #B are further switched round and
the same weights as those at the first retransmission
areused. Thatis, every time retransmission is repeated,
weights used for the stream #A and stream #B are switched
round.
Here, weights to be multiplied on transmission
signals arranged for the antenna #1 and antenna #2 from

the different standpoint are shown in FIG.5B. That is,
this figure shows what signals are actually sent from
the antenna #1 and antenna #2. The contents shown in
FIG.5A and FIG.5B are substantially the same.
Then, effects resulting from changes of weights
between the initial transmission and retransmission will
be explained. When a weight is multiplied on a
transmission signal, the transmission signal acquires
directivity. However, this directivity does not mean
that the transmission signal is actually propagating in
a specific direction as seen in the formation of beams
by an array antenna technology, but it is a matter of
mathematical expressions. This is because while there
is a low fading correlation between antennas in the MIMO
communication, there is a high fading correlation between
antennas in the array antenna technology. However, this
expression is used in studying effects of weight
multiplication of this embodiment because explaining with
an image that a transmission signal is actually
propagating with directivity facilitates an
understanding.
FIG. 6 is a conceptual view illustrating directivity
of a transmission signal. Signals sent from a radio
transmission apparatus 100 using weights wα and wβ follow
a path #1 represented by a thick line, are reflected at
some midpoint by a building 191 and reach a radio reception
apparatus 150 without any significant reduction of their
intensity. On the other hand, signals sent using weights

wγ and wδ follow a path#2 represented by a thin line, are
reflected at some midpoint by a building 192 and reach
the radio reception apparatus 150 affected by the
propagation path with their intensity significantly
weakened.
At the time of initial transmission, the stream #A
multiplied by weights wα and wβ follows the path #1 and
the stream #B multiplied by weights wα and wβ follows the
path #2. Then, at the time of retransmission the weights
to be multiplied on the transmission signals are switched
round, and therefore the stream #A follows the path #2
and the stream #B follows the path #1.
FIG.7A, FIG.7B, FIG.8A and FIG.8B show quality
comparisons between signals sent from a conventional
radio transmission apparatus and signals sent from the
radio transmission apparatus according to this embodiment
These figures show conceptual views illustrating the
quality (bar graphs) of received signals after being
combined on the receiving side and a level L1 at which
data can be received correctly.
FIG.7A and FIG.7B show cases of the conventional
radio transmission apparatus. FIG.7A illustrates
reception quality at the time of initial transmission
and FIG.7B illustrates reception quality at the time of
data retransmission.
In FIG.7A, the quality level of the received signal
of none of the stream #A and the stream #B exceeds the
level L1. At this time, the receiving side cannot receive

data correctly, and therefore sends back a NACK signal
to the transmitting side and the transmitting side
retransmits the data. However, when the time variation
of the propagation path environment is small, no
significant improvement of the reception quality on the
receiving side can be expected even at the time of data
retransmission. Thus, as shown in FIG.7B, by combining
the received signal at the time of initial transmission
and the received signal at the time of data retransmission
after the data retransmission, the reception quality
after the combination of the stream #A which had original
reception quality at a level close to the level L1 at
the time of initial transmission exceeds the level L1.
On the other hand, even if data is retransmitted, the
reception quality of the stream #B after the combination
cannot exceed the level L1. Thus, the receiving side
sends back an NACK signal to the transmitting side several
times more until the reception quality of the stream #B
exceeds the level L1 and the transmitting side retransmits
data every time the NACK signal is sent.
FIG.8A and FIG.8B show the case of the radio
transmission apparatus according to this embodiment.
FIG.8A illustrates reception quality at the time of
initial data transmission and FIG.8B illustrates
reception quality at the time of data retransmission.
FIG.8A is the same as FIG.7A. None of the reception
quality levels of the stream #A and stream #B exceeds
the level L1. However, at the time of retransmission,

weights used for the stream #A and stream #B are switched
round, and therefore the environments of propagation
paths which the stream #A and stream #B follow are placed
in a condition as if those environments are averaged.
In this way, both the reception quality levels of the
streams #A and #B after combining the received signals
at the time of initial transmission and at the time of
retransmission exceed the level L1, and it is therefore
possible to receive signals correctly.
In the above described configuration, the weight
control section 112 of the radio reception apparatus
according to this embodiment changes weights to be
multiplied on the transmission signal from the weights
used for the previous transmission every time data is
retransmitted.
This causes each data stream to be sent to the
receiving side through different propagation path
environments between the previous transmission and
retransmission, and therefore the probability that the
same data may contain errors successively is reduced and
as a result, the data error rate characteristic after
packet combination improves . In other words, adiversity
gain when the retransmission data is combined on the
receiving side increases and the reception performance
on the receiving side improves.
Furthermore, the weight control section 112 of the
radio reception apparatus according to this embodiment
switches round the weights corresponding to the

respective antennas at the time of the previous
transmission and multiplies the transmission signals by
those weights every time data is retransmitted.
For example, as shown in FIG.7A or FIG.8A, even if
the receiving side sends back a NACK signal at the time
of initial transmission, reception quality of all data
streams is not averagely bad but it is often the case
that reception quality of only some data streams is bad.
At this time, by switching round weights to be
multiplied on the transmission signals between previous
transmission and retransmission, the propagation path
environments for the respective data streams are switched
round and averaged, and therefore the reception quality
improves at an early stage.
Furthermore, since the weights already used at the
time of the previous transmission are reused at the time
of retransmission by only switching round the signals
to be multiplied, and therefore there is no need for
processing such as feeding back other information, for
example, the propagation path information detected on
the receiving side to the transmitting side.
Thus, according to this embodiment, weights to be
multiplied on transmission signals are switched round
between the initial transmission and retransmission, and
therefore it is possible to increase a diversity gain
obtained through data retransmission and improve
reception performance on the receiving side.
Note that here a case where transmission data

consists of two streams #A and #B has been explained as
an example, but the number of data streams can be three
or more, and in this case, it is possible to use weights
to be used at the time of data retransmission in rotation
every time data is retransmitted. That is, in the case
of three data streams, the weights used at the time of
the initial transmission are reused at the third
retransmission.
Furthermore, here, a MIMO transmission having a low
fading correlation between antennas has been explained,
but it is also possible to use an array antenna having
a high fading correlation between antennas . At this time,
antennas are arranged so that the fading correlation
between antennas becomes substantially 1. Directivity
patterns as shown in FIG.6 are formed by multiplying
transmission signals by weights. The stream #A
multiplied by weights wα and wβ at the time of the initial
transmission follows the path #1 and the stream #B
multiplied byweights wα and wβ follows the path #2. Then,
at the time of retransmission, weights to be multiplied
on the transmission signals are switched round, and
therefore the stream #A follows the path #2 and the stream
#B follows the path #1 . This makes it possible to average
propagation path environments as with the above described
case .
Here, a case whereweights of the stream #A and stream
#B are switched round at the time of data retransmission
has been explained as an example, but it is also possible

to select not the weights used at the time of the previous
transmission but totally different values as weights for
retransmission.
Furthermore, here a case where the propagation path
information, etc., detected on the receiving side is not
fed back to the transmitting side has been explained as
an example, but for a radio transmission apparatus in
which channel quality information is fed back from the
receiving side to the transmitting side for the purpose
of increasing the channel capacity and weights are decided
so that more power is assigned to channels of good quality,
it is also possible to fine-tune weights based on this
fed back channel quality information and assign weights
so that the channel quality exceeds the minimum level
L1 in all paths.
(Embodiment 2)
FIG.9 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.2 and the
same components are assigned the same reference numerals
and explanations thereof will be omitted.
Features of this embodiment include that it is
provided with IFFT sections 201, delay sections 202 and
a delay control section 203, it carries out a communication
based on an OFDM scheme, adds delay times which differ

from one transmission data stream to another, transmits
the data streams through their respective antennas at
different transmission timings at the time of
transmission and thereby drastically changes the
characteristic of a received signal on the frequency axis.
Therefore, it is possible to drastically change the
propagation path environment every time retransmission
is performed. Furthermore, transforming data into a
multicarrier according to the OFDM scheme makes it
possible to multiplex delay signals with different delay
times and send the multiplexed signals.
Then, an operation of the radio transmission
apparatus in the above described configuration will be
explained.
The modulation section 102-1 carries out modulation
processing on a data stream output from the buffer 101-1
and outputs the data stream. The signal output from the
modulation section 102-1 is branched at some midpoint
and output to the IFFT sections 201-1 and 2 01-2 . Likewise
the modulation section 102-2 carries out modulation
processing on a data stream output from the buffer 101-2
and outputs the data stream. The signal output from the
modulation section 102-2 is branched at some midpoint
and output to the IFFT sections 201-3 and 201-4.
On the other hand, the delay control section 203
includes a table storing a plurality of types of delay
times, selects a delay time for each transmission signal
from the table according to a retransmission count

notified from the retransmission count detection section
110 and outputs the delay time to the delay sections 202-1
to 202-4. The delay times output from the delay control
section 203 will be explained in more detail later.
The delay section 202-1 delays the transmission
timing of the signal output from the IFFT section 201-1
by a delay time output from the delay control section
203 and outputs the delayed signal to the addition section
104-1. Furthermore, the delay section 202-2 delays the
transmission timing of the signal output from the IFFT
section 2 01-2 by a delay time output from the delay control
section 203 and outputs the delayed signal to the addition
section 104-2.
Likewise, the delay section 202-3 delays the
transmission timing of the signal output from the IFFT
section 2 01-3 by a delay time output from the delay control
section 203 and outputs the delayed signal to the addition
section 104-1. Furthermore, the delay section 202-4
delays the transmission timing of the signal output from
the IFFT section 201-4 by a delay time output from the
delay control section 203 and outputs the delayed signal
to the addition section 104-2.
The addition section 104-1 adds up the signals output
from the delay sections 202-1 and 202-3, the transmission
timings of which have been delayed and outputs the addition
result to the transmission radio section 105-1 . Likewise,
the addition section 104-2 adds up the signals output
from the delay sections 202-2 and 202-4, the transmission

timings of which have been delayed and outputs the addition
result to the transmission radio section 105-2. The
processing thereafter is the same as that in Embodiment
1 .
Then, an example of a delay time added to a
transmission signal of each system will be explained using
FIG.10A and FIG.10B.
FIG.10A shows delay times of transmission timings
of transmission signals arranged for data stream #A(SA)
and data stream #B(SB). For example, at the time of
initial data transmission, the delay time of the stream
#A is 0 for the transmission system on the antenna #1
side and Τ α for the transmission system on the antenna
#2 side. Furthermore, the delay time of the stream #B
is 0 for the transmission system on the antenna #1 side
and τ β for the transmission system on the antenna #2 side .
Then, at the first retransmission, the delay time
of the stream #A is 0 for the transmission system on the
antenna #1 side and τ β for the transmission system on the
antenna #2 side. Furthermore, the delay time of the
stream #B is 0 for the transmission system on the antenna
#1 side and τ α for the transmission system on the antenna
#2 side.
That is, the combination of delay times of the data
stream #Aat the time of the initial transmission is applied
to the data stream #B at the time of the first
retransmission. Furthermore, the combination of delay
times used for the data stream #B at the time of the initial

transmission is applied to the data stream #A at the first
retransmission. The combinations of delay times used for
the stream #A and stream #B at the time of the initial
transmission are switched round at the time of the first
retransmission.
At the time of 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 the initial
transmission are switched round. That is, the delay time
of the stream #A is Τ α for the transmission system on the
antenna #1 side and 0 for the transmission system on the
antenna #2 side, and the delay time of the stream #B is
Τ β for the transmission system on the antenna #1 side
and 0 for the transmission system on the antenna #2 side.
At the third retransmission, the delay times used for
the stream #A and stream #B are further switched round.
Now, by changing the standpoint, delay times of
transmission signals arranged for the antenna #1 and
antenna #2 are shown in FIG.10B. That is, this figure
shows how signals are actually delayed and sent through
the antenna #1 and antenna #2. The contents shown in
FIG.10A and FIG.10B are substantially the same.
FIG.11 shows transmission timings of signals
transmitted from the above described radio transmission
apparatus on the time axis. Note that the actual
transmi ssion data streams are weighted (e.g., the signals
transmitted from the antenna #1 are wαSA+wγSB as described

above) , but the same weights at the time of the initial
transmission are also used at the time of the
retransmission in this embodiment, and therefore
notations of weights will be omitted to make it easier
to distinguish one signal from another.
This figure shows that initial data transmission
is performed at time 0 and data retransmission is performed
at time t1 afteralapseof acertaintime. From the antenna
#1, data stream #A (SA, S'A) and data stream #B (SB, S'B)
are transmitted at the same timing for both the initial
transmission and retransmission . On the other hand, from
the antenna #2, SA and SB are transmitted with delay times
Τ α, and Τ β, respectively at the time of initial
transmission, while S'A and S'B are transmitted with delay
times Τ β and Τ α, respectively at the time of
retransmission.
Here, when attention is focused on the data stream
#A(SA) at the time of the initial transmission, SA is
transmitted with a time difference Τ α provided between
the antenna #1 and antenna #2. This is intended to reduce
a fading correlation between the antennas. On the other
hand, when attention is focused on the data stream #A(S'A)
at the time of the retransmission, the time difference
providedbetween the antenna #1 and antenna #2 is z p. That
is, transmission is carried out in such a way that the
fading correlation between the antennas is changed at
the time of the initial transmission and at the time of
the retransmission. The also applies to the data stream

#B(SB, S'B) in like fashion.
Furthermore, when attention is focused on both SA
and SB transmitted from the antenna #2 at the time of the
initial transmission, SB is transmitted ( Τ β-Τα) behind
SA. On the other hand, at the time of the retransmission,
S'A is transmitted (Τ β-Τα) behind S'B on the contrary.
This means that transmission is carried out in such a
way that the difference in transmission timings between
the data stream #A and data stream #B (including the
relationship as to which is ahead and which is behind)
is changed at the time of the initial transmission and
at the time of the retransmission. Here, for simplicity
of explanation, attention has been focused only on the
data stream transmitted from the antenna #2, but the same
thing is also applied when the data stream transmitted
from the antenna #1 is taken into consideration together.
The effect of changing the difference in
transmission timings between data streams at the time
of the initial transmission and at the time of the
retransmission will be explained below. Speaking
plainly, frequency selective fading is a result of signals
with the same frequency and a phase difference of 180
degrees weakening each other. Thus, by intentionally
delaying transmission timings of transmission signals,
that is, shifting phases, it is possible to change a fading
characteristic that a signal receives. FIG.12A to
FIG.12C show reception power at a conventional apparatus .
A stream #A keeps a high reception level both at the time

of initial transmission (see FIG.12A) and at the time
of retransmission (see FIG.12B), while a stream #B keeps
a low reception level both at the time of initial
transmission and at the time of retransmission.
Therefore, even if the data at the time of the initial
transmission and the data at the time of the retransmission
are combined (see FIG.12C), only the stream #A reaches
the level for correct reception and the stream #B remains
at levels where it cannot be received correctly.
FIG.13A to FIG.13C show reception power according
to this embodiment. The levels of received signals are
affected by frequency selective fading which differs
between the streams. Therefore, the pattern of the
reception level on the frequency axis differs between
the streams. At the time of initial transmission (see
FIG.13A) and at the time of retransmission ( see FI G . 1 3B ) ,
delay processes applied to the stream #A and stream #B
are switched round, and therefore the levels of signals
after being combined on the receiving side are averaged
(see FIG.13C) and both the stream #A and stream #B can
be demodulated correctly.
Here, the figures describe a situation in which the
phase of the fading characteristic curve on the frequency
axis is shifted by 180 degrees by delaying transmission
signals. However, it will be sufficient to change the
fading characteristic only to a certain degree by delaying
transmission signals in this embodiment, and the phase
need not always be shifted by 180 degrees. Note that the

fluctuation pitch of the fading characteristic depends
on the moving speed of a mobile station and the frequency
band used for communications , and therefore it is possible
to calculate a delay time for shifting the phase of the
fading characteristic curve by 180 degrees.
Furthermore, when the propagation path information
such as channel quality is fed back from the receiving
side to the transmitting side in the above described
configuration as in the case of Embodiment 1, it is also
possible to fine-tune delay times based on this fed back
propagation path information.
Thus, according to this embodiment, variations in
the reception level are averaged on the frequency axis
of each stream for every retransmission, and therefore
it is possible to demodulate the combined signal correctly
and improve the reception performance on the receiving
side .
Note that Embodiment 1 and Embodiment 2 can be used
in combination. That is, it is possible to further add
a delay time to a transmission signal multiplied by a
weight to delay the transmission timing and transmit the
delayed signal. At this time, the effects of the
respective embodiments are superimposed, making it
possible to further improve the reception performance.
As described above, the present invention allows
a radio communication system which transmits a plurality
of data streams using a plurality of antennas (e.g.,
adaptive array antenna technology, MIMO technology, STC

technology, etc.) to increase, for example, when HARQ
is applied, a diversity gain at the time of data
retransmission and improve the reception performance on
the receiving side.
This application is based on the Japanese Patent
Application No.2002-268968 filed on September 13, 2002,
entire content of which is expressly incorporated by
reference herein.
Industrial Applicability
The present invention is applicable to a radio
transmission apparatus and radio transmission method to
which an adaptive array antenna technology, MIMO
technology or STC technology, etc., is applied.

We Claim:
1. A radio transmission apparatus comprising:
a multiplication section (103-1, 103-2, 103-3, 103-4) that multiplies a
plurality of data streams (#A,#B) by a plurality of weights (Wα, Wβ, Wγ,
Wδ) respectively;
a transmission section (105-1, 105-2) that transmits the plurality of
weighted data streams from a plurality of transmission antennas (106-1,
106-2) simultaneously; and
a control section (112) that controls said multiplication section (103-1,
103-2, 103-3, 103-4) so that at the time of retransmission of said plurality
of data streams (#A,#B), said plurality of data streams is multiplied by
weights (Wα, Wβ, Wγ, Wδ) different from the weights (Wα, Wβ, Wγ, Wδ) at
the time of previous transmission,
characterized in that
said control section (112) selects weights (Wα, Wβ, Wγ, Wδ) at the time of
the retransmission from among a plurality of weights (Wα, Wβ, Wγ, Wδ)
corresponding to said plurality of data streams (#A,#B) at the time of the
previous transmission.

2. The radio transmission apparatus as claimed in claim 1, wherein said
control section (112) performs said control based on propagation path
information notified from the receiving side.
3. The radio transmission apparatus as claimed in one of claims 1 or 2,
wherein said transmission is diversity transmission.
4. The radio transmission apparatus as claimed in one of claims 1 to 3,
wherein said plurality of data streams (#A,#B) is transformed into a
multicarrier beforehand.
5. The radio transmission apparatus as claimed in claim 4, wherein said
transformation into a multicarrier is OFDM (orthogonal Frequency Division
Multiplex) processing.
6. A radio transmission method comprising:
a multiplication step (ST1020) of multiplying a plurality of data streams
(#A,#B) by a plurality of weights (Wα, Wβ, Wγ, Wδ) respectively;
a transmission step (ST1030) of simultaneously transmitting the
plurality of weighted data streams from a plurality of transmission
antennas (106-1,106-2); and

a control step (ST1090) of performing control so that at the time of
retransmission of said plurality of data streams (#A,#B), said plurality of data
streams (#A,#B) is multiplied by weights (Wα, Wβ, Wγ, Wδ ) different from
the weights (Wα, Wβ, Wγ, Wδ ) at the time of previous transmission
respectively,
characterized in that
said control step selects weights (Wα, Wβ, Wγ, Wδ) at the time of the
retransmission from among a plurality of weights (Wα, Wβ, Wγ, Wδ)
corresponding to said plurality of data streams (#A,#B) at the time of the
previous transmission.

The invention relates to a radio transmission apparatus comprising a
multiplication section (103-1, 103-2, 103-3, 103-4) that multiplies a plurality of
data streams (#A,#B) by a plurality of weights (Wα, Wβ, Wγ, Wδ) respectively; a
transmission section (105-1, 105-2) that transmits the plurality of weighted data
streams from a plurality of transmission antennas (106-1, 106-2) simultaneously;
and a control section (112) that controls said multiplication section (103-1, 103-
2, 103-3, 103-4) so that at the time of retransmission of said plurality of data
streams (#A,#B) said plurality of data streams is multiplied by weights (Wα, Wβ,
Wγ, Wδ) different from the weights (Wα, Wβ, Wγ, Wδ) at the time of previous
transmission. The said control section (112) selects weights (Wα, Wβ, Wγ, Wδ) at
the time of the retransmission from among a plurality of weights (Wα, Wβ, Wγ,
Wδ) corresponding to said plurality of data streams (#A,#B) at the time of the
previous transmission.

Documents:

771-KOLNP-2004-ABSTRACT 1.1.pdf

771-kolnp-2004-abstract.pdf

771-KOLNP-2004-AMANDED PAGES OF SPECIFICATION.pdf

771-KOLNP-2004-CLAIMS.pdf

771-KOLNP-2004-CORRESPONDENCE 1.2.pdf

771-KOLNP-2004-CORRESPONDENCE 1.3.pdf

771-KOLNP-2004-CORRESPONDENCE-1.1.pdf

771-kolnp-2004-correspondence.pdf

771-kolnp-2004-correspondence1.4.pdf

771-KOLNP-2004-DESCRIPTION (COMPLETE) 1.1.pdf

771-kolnp-2004-description (complete).pdf

771-KOLNP-2004-DRAWINGS 1.1.pdf

771-kolnp-2004-drawings.pdf

771-KOLNP-2004-EXAMINATION REPORT REPLY RECIEVED.pdf

771-kolnp-2004-examination report.pdf

771-kolnp-2004-form 1.1.pdf

771-kolnp-2004-form 1.pdf

771-KOLNP-2004-FORM 13.pdf

771-kolnp-2004-form 18.1.pdf

771-kolnp-2004-form 18.pdf

771-KOLNP-2004-FORM 2 1.1.pdf

771-kolnp-2004-form 2.pdf

771-kolnp-2004-form 3.1.pdf

771-kolnp-2004-form 3.pdf

771-kolnp-2004-form 5.1.pdf

771-kolnp-2004-form 5.pdf

771-kolnp-2004-gpa.pdf

771-kolnp-2004-granted-abstract.pdf

771-kolnp-2004-granted-claims.pdf

771-kolnp-2004-granted-description (complete).pdf

771-kolnp-2004-granted-drawings.pdf

771-kolnp-2004-granted-form 1.pdf

771-kolnp-2004-granted-form 2.pdf

771-kolnp-2004-granted-specification.pdf

771-kolnp-2004-intenational publication.pdf

771-kolnp-2004-international search report.pdf

771-KOLNP-2004-OTHERS.pdf

771-KOLNP-2004-PA.pdf

771-kolnp-2004-pct priority document notification.pdf

771-kolnp-2004-pct request form.pdf

771-KOLNP-2004-PETITION UNDER RULE 137.pdf

771-kolnp-2004-reply to examination report.pdf

771-kolnp-2004-reply to examination report1.1.pdf

771-kolnp-2004-specification.pdf

771-KOLNP-2004-TRANSLATED COPY OF PRIORITY DOCUMENT 1.1.pdf

771-KOLNP-2004-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf

771-kolnp-2004-translated copy of priority document1.2.pdf

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Patent Number

251190

Indian Patent Application Number

771/KOLNP/2004

PG Journal Number

09/2012

Publication Date

02-Mar-2012

Grant Date

29-Feb-2012

Date of Filing

07-Jun-2004

Name of Patentee

PANASONIC CORPORATION

Applicant Address

1006, OAZA KADOMA, KADOMA-SHI, OSAKA 571 8501

Inventors:

#	Inventor's Name	Inventor's Address
1	MIYOSHI KENICHI	11-4-1305, NOKENDAIHIGASHI, KANAZAWA-KU, YOKOHAMA-SHI, KANAGAWA 236-0058

PCT International Classification Number

H04B 7/06

PCT International Application Number

PCT/JP2003/010200

PCT International Filing date

2003-08-11

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2002-268968	2002-09-13	Japan