Data communication apparatus and method with antennas diversity

Abstract: Received signal provided via plural antennas 101 are memorized in memory 102. First weight controller 103 calculates the first weights by which the received signals are weighted, and second weight controller 104 calculates the second weights using the received signals. Multipliers 107 and 108 multiply the memorized received signals by the first weights, while multiply the memorized received signals by the second weights when a channel quality of radio signals deteriorates due to a change of the radio signal's direction of arrival . Adder 109 synthesizes the multiplication results. Propagation path distortion compensator 110 estimates a deterioration of the channel quality using synthesis result to compensate. Detector 111 detects the compensation result that is used as a parameter to calculate the first and second weights, which allows the apparatus to receive radio signals without deteriorating reception qualities when the channel quality deteriorates rapidly due to the change of the radio signal's direction of arrival.

Description: Field of the Invention The present invention relates to a data communication apparatus and data communication method used in a digital radio communication system using a CDMA (Code Division Multiple Access) system and so on. Description of the Related Art Conventionally, in a data communication method, a plurality of received signals provided from a plurality of antennas are synthesized by multiplying each received signal by weights. This processing forms the reception directivity and suppresses unnecessary signals to prevent reception performance from deteriorating. As a configuration of such antennas, there is an adaptive array antenna apparatus. Since the adaptive array antenna apparatus has a function to cancel an affect of multi-path fading and so on, it can reduce a communication performance deterioration caused by interference and multi-path propagation in radio signal environments of mobile communications. As the number of antennas in the adaptive array antenna, 2 to 10 antennas are usually applied, however 2 to more than 1, 000 antennas are sometimes applied. FIG.1 is a block diagram illustrating a configuration of a conventional data communication apparatus. In FIG.1, signals received at plural antennas 1 are subjected to a predetermined radio reception processing, then input to weight controller 2 and multipliers 3 and 4. Weight controller 2 calculates weights , by which the plurality of signals received at plural antennas 1 are weighted, corresponding to electric field intensities and the phase of received signals and outputs the calculated weights to multipliers 3 and 4. In addition, directions from which radio signals are transmitted, i.e., the radio signal's direction of arrival are estimated by calculating the weights. Multipliers 3 and 4 multiply the received signals by the weights. Adder 5 adds the multiplication results in multipliers 3 and 4 and outputs the addition result to propagation path distortion compensator 6. Propagation path distortion compensator 6 estimates a radio signal distortion caused in a propagation path using the addition results, compensates the estimated distortion, and outputs the received signals subjected to the distortion compensation to weight controller 2 and detector 7. Detector 7 detects the received signals subjected to the distortion compensation and outputs the detected results as received signals to a received signal processing circuit (not shown), while outputs weights to synthesize the received signals provided via plural antennas 1 to weight controller 2 to update a parameter of weight controller 2. However, in the above conventional data communication apparatus, in the case where a channel quality deteriorates by a rapid change of the radio signal's direction of arrival and so on, other antenna synthesis weights are calculated. At this time, the channel quality deteriorates when a value obtained before the radio signal is switched is used because incoming directions of arrival are different. Hence, weight controller 2 can not use the value obtained before the radio signal is switched as an initial value. Therefore an initial synthesis of received signals after the radio signal is switched should be performed without directivity. Hence desired radio signals are affected by interference signals of the same channel transmitted from different directions, thereby deteriorating the reception performance. US patent 5,218,359 provides an adaptive array antenna system having a plurality of antenna elements, corresponding weight circuits for weighting amplitude and phase of received signal by each antenna element, and a combiner for combining weighted signals. The system has a plurality of antenna beams at the same time by determining weights of said weight circuits, so that the received signals due to multipath transmission are received while avoiding multipath interference. Received signals are converted to digital form, which is stored in a memory, in which it is first determined whether a received signal in each beam direction exists or not, then selecting at least one direction beam which has less mutual delay time, adjusting phase of selected ones, and determining weights. SUMMARY OF THE INVENTION An object of the present invention is to provide a data communication apparatus and data communication method capable of receiving radio signals without deterioration of reception performance even in the case where an radio signal's direction of arrival changes rapidly. This object is achieved by. a data communication apparatus comprising plural antennas, a memory section for memorizing received signals provided via the plural antennas, a first weight control section, using the memorized received signals, for calculating first weights by which the received signals provided via the plural antennas are weighted to synthesize, a second weight control section for calculating second weights using the received signals provided via the plural antennas, a multiplying section for multiplying the memorized received signals by the first weights, while multiplying the memorized received signals by the second weights when a channel quality of radio signals deteriorates, an adding section for synthesizing the multiplication result, a compensating section for estimating a deterioration of the channel quality of radio signals using the synthesis result to compensate, and a detecting section for detecting the compensation result to output as a parameter to calculate the first and second coefficients to the first and second weight control sections. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is a block diagram illustrating a configuration of a conventional data communication apparatus; FIG.2 is a block diagram illustrating a configuration of a data communication apparatus according to the first embodiment of the present invention; FIG.3 is a block diagram illustrating a configuration of a propagation path distortion compensator of the data communication apparatus according to the first einbodiment of the present invention; FIG.4 is a diagram illustrating a slot configuration of received signals provided via plural antennas; FIG.5 is a block diagram illustrating a configuration of a data communication apparatus according to the second and third embodiments of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of a data communication apparatus and a data communication method are explained below with reference to attached drawings. (First embodiment) FIG.2 is a block diagram illustrating a configuration of a data communication apparatus according to the first embodiment of the present invention. In FIG.2, plural antennas 101 composed of n numbers of antennas are to receive incoming radio signals. Memory 102 is to memorize received signals provided via plural antennas 101, for example, FIFO (First In First Out) memory is used. First weight controller 103 calculates weights, using previous received signals at plural antennas 101 (for example, one slot before) memorized in memory 102, corresponding to electric field intensities and the phase of received signals. Second weight controller 104 calculates optimal weights for the received signals provided via plural antennas 101 that are memorized in memory 102; using current received signals at plural antennas 101 when propagation path switching instruction signal 106 is input. Switch 105 switches first and second weight controllers 103 and 104 corresponding to propagation path switching instruction signal 106. Multipliers 107 and 108 multiply the received signals output from memory 102 by the weights obtained in first weight controller 103 or second weight controller 104, where the weights are input via switch 105. Adder 109 adds the multiplication results of multipliers 107 and 108, and outputs the addition result to first and second weight controllers 103, 104 and propagation path distortion compensator 110. Propagation path distortion compensator 110 estimates a radio signal distortion caused in the propagation path using the addition results, compensates the estimated distortion, and outputs the received signals subjected to the distortion compensation to weight controllers 103, 104 and detector 111. Detector 111 detects the received signals subjected to the distortion compensation and outputs the detected results as received signals to a received signal processing circuit (not shown), while outputs the detection result to first and second weight controllers 103 and 104 as a parameter to update weights. In the constitution described above, the signals received at plural antennas 101 are once memorized in memory 102 then output to firstweight controller 103. The weights, by which the received signal is weighted, output from memory 102 is thus calculated. In this case, switch 105 selects first weights controller 103 according to propagation path switching instruction signal 106. By this selection, the weights obtained in first weight controller 103 input via switch 105 is multiplied by the received signal output from memory 102 in multipliers 107 and 108. The multiplication results are added in adder 109, then the addition result is output to the first and second weight controllers 103, 104 and propagation path distortions compensator 110. Hereinafter, the processing of propagation path distortion compensator 110 is explained with reference to its configuration illustrated in FIG.3. Propagation path distortion estimation circuit 201 estimates a propagation path distortion of the addition result using the pilot signals in or envelop information, and outputs the estimated propagation path distortion to propagation path distortion compensation circuit 202, and first weight controller 103 and second weight controller 104. Propagation path distortion compensation circuit 202 compensates the propagation path distortion estimated by propagation path distortion estimation circuit 201 to output to detector 111. Detector 111 detects the compensated received signal and outputs the detection result as the received signal to a received signal processing circuit (not shown), while outputs the detection result to first and second weight controllers 103 and 104 as a parameter to update the weights. At this time, it is preferable to output a signal of propagation path distortion compensation output from propagation path distortion compensator 110 to the received signal processing circuit to improve error correction performance. At this time, first weight controller 103 performs the estimation of incoming direction based on pervious slot information because the received signal to be subjected to the estimation was once memorized in memory 102. For example, in the case where signals are received at plural antennas 101 according to the order of Slot 300, Slot 301, Slot 302 and Slot 303, one slot of them is memorized in memory 102 according to the order. It is preferable that memory 102 has a memory capacity of plurality of slots. In this case, at the time when antenna 101 receives Slot 301, first weight controller 103 has already calculated the weights based on information on Slot 300 memorized in memory 102. At this time, multipliers 107 and 108 multiply the received signals output from memory 102 by the weights calculated based on Slot 300. It is assumed that the channel quality deteriorates by a rapid change of radio signal's direction of arrival and so on at the reception time of Slot 302. Then propagation path switching instruction signal 106 is input to switch 105 from the external. At this time, the channel quality is obtained by measuring SNR (Signal to Noise Ratio) , reception power, etc.. Accordingly it is possible to obtain propagation path switching instruction signal 106 from the external when the radio signal's direction of arrival is changed rapidly. In other words, switch 105 to which propagation path switching instruction signal 106 is input performs the switching to connect second weight controller 104 to multipliers 107 and 108. And second weight controller 104 calculates the weights from Slot 302, while first weight controller 103 concurrently calculates the weights from Slot301 memorized in memory 102. At this time, since second weight controller 104 can obtain the content of Slot 302 earlier than first weight controller 103, second weight controller 104 calculates the weights on Slot 302 earlier than first weights controller 103. Thus, at the reception time of Slot 303, multipliers 107 and 108 multiply Slot 302 output from memory 102 by the weights obtained in second weight controller 104 based on Slot 302, and adder 109 adds the multiplication results. Further, at the reception time of Slot 303, switch 105 switches to first weight controller 103 again. It is otherwise preferable to perform the switching by next propagation path switching instruction signal 106. At the time of this switching, first weight controller 103 uses the weights calculated by second weights controller 104. First weight controller 103 calculates the weights again with respect to Slot302, and updates the weights continuously with respect to the following receptions. Meanwhile, in the case where switching has not been performed until next propagation path switching instruction signal 106 is input, first weight controller 103 continues to.update the weights using the weights in second weight controller 104. In addition, it is preferable for saving power consumption that to stop an operation of first weight controller 103 or second weight controller 104 that is not necessary to operate, or until next propagation path switching instruction signal 106 is input from the external. In the case where the channel quality deteriorates by a rapid change of the radio signal's direction of arrival and so on, it is thus possible in the first embodiment that to calculate in advance in second weight controller 104 the weights to be used after the radio signal's direction of arrival is changed, before the addition of multiplication results of received singles provided via plural antennas by the weights to synthesize the received signals, thereby making it possible to receive radio signals without deteriorating the reception property even in the case where the channel quality deteriorates rapidly. In addition, it is designed to operate either of first weight controller 103 or second weight controller 104 that is necessary when an usual state or when the radio signal's direction of arrival changes rapidly, thereby saving power consumption. (Second embodiment) FIG.5 is a block diagram illustrating a configuration of a data communication apparatus according to the second embodiment. In addition, some sections in the second embodiment illustrated in FIG.5 are assigned the same symbols as those of corresponding sections in the first embodiment illustrated in FIG.2 and its explanation is omitted. The different configuration of data communication apparatuses between in the first embodiment illustrated in FIG.2 and the second embodiment illustrated in FIG.5 is that first weight controller 103, second first weight controller 104, and switch 105 illustrated in FIG.2 are replaced with a weight controller composed of one circuit that is indicated by 401 in FIG.5. In this configuration, as illustrated in FIG.4, at the time of receiving Slot 301, since received signals are once memorized in memory 302, weight controller 401 calculates weights based on information of a previous slot, i.e., Slot 300. For example, in the constitution where a memory capacity of memory 102 is for one slot, at the time Slot 301 is input to memory 102, weight controller 401 controls the weights based on the information of Slot 300 and multipliers 107, 108 and adder 109 also multiply Slot 301 by the weights generated based on Slot 300. In the case where a radio signal's incoming direction changes rapidly at the time of receiving Slot302, propagation path switching instruction signal 106 is input to weight controller 401 from the external. At this time, weight controller 401 does not update the weights using information of Slot 301 memorized in memory 102, and outputs the weights (fixed value) calculated based on Slot 300 that is the previous one to multipliers 107 and 108. During the period, weight controller 401 calculates the weights using information of Slot 302 input from plural antennas 101 directly not via memory 102, and outputs the weights calculated using the information of Slot 302 input from plural antennas 101 directly to multiplies 107 and 108. It is thus possible in the second embodiment to obtain the same effect as the first embodiment. It is also possible to downsize a circuit configuration as compared to the first embodiment because the first and second weight controllers and the switch are integrated into one circuit (weight controller 401) that responds to the case of a rapid change of the radio signal's incoming direction. (Third embodiment) This embodiment is explained with reference to FIG.5 as well as the second embodiment. When propagation path switching instruction signal 106 is input from the external, weight controller 401 performs concurrently the calculations of the weights on a received signal of a previous slot (one slot before) memorized in memory 102 and the calculation of the weights on a received signal of a current slot. In the case where it is judged that further calculation ability is available, weight controller 401 calculates each weights on the received signal memorized in memory 102 and on the received signal provided via plural antennas 101, in the same manner as the case where propagation path switching instruction signal 106 is not generated. In the case where it is judged that further calculation ability is not available, the estimation accuracy in each slot is decreased. For example, the weights on the previous received signal is calculated in the first half of a slot, and the weights on the current received signal is calculated in the latter half of the slot. It is thus possible, as well as the second embodiment, to downsize a circuit configuration as compared to the first embodiment because the first and second weight controllers and the switch are integrated into one circuit (weight controller 401) that responds to the case of a rapid change of the radio signal's incoming direction. Further according to this constitution, it is possible to calculate the weights using both the received signals memorized in memory 102 and the received signal provided via plural antennas corresponding to the availability of calculation ability. In this manner, in the case where the radio signal's incoming direction is changed rapidly, weight controller 401 can calculate the weights using the received signal memorized in memory 102 to output to multipliers 107 and 108, while calculates the weights using the received signal directly provided from plural antennas 101. It is thus possible in multipliers 107 and 108 to multiply received signals provided via plural antennas 101 by the weights obtained from a received signal closer to the current signal than that in the second embodiment. (Fourth embodiment) In the fourth embodiment, the weights for antenna synthesis calculated according to either of the first embodiment to the third embodiment are multiplied to transmit from plural antennas. This processing improves reception performance of a partner side, thereby making it possible to improve the transmission performance as compared to a conventional data communication apparatus. As described above, according to the fourth embodiment, since the weights to synthesize radio signals provided via plural antennas 101 are used to transmit weighted reception signals from plural antennas 101, it is possible to improve not only reception performance but also transmission performance. As apparent from the above-description, according to the present invention, even in the case where the radio signal's direction of arrival changes rapidly, it is possible to receive radio signals without deteriorating reception performance. In other words, in the case where the channel quality deteriorates by a rapid change of the radio signal's direction of arrival, the second weight control section calculates in advance weights to be used after the channel quality deteriorates before multiplying received signals by weights to synthesize received signals provided via plural antennas. It is thereby possible to receive radio signals without deteriorating reception properties even in the case where the channel quality deteriorates due to the rapid change of the signal's direction of arrival. Further, it is possible to improve not only reception performance but also reception performance by using weights to synthesize radio signals provided via plural antennas to transmit weighted transmission signals from plural antennas.

Claims: A data communication apparatus comprising: a plurality of antennas (101); memorizing means (102) for memorizing signals received through said plurality of antennas (101); first weight controlling means (103) for calculating first weights to weight and synthesize the signals memorized in said memorizing means (102), characterized by, second weight controlling means (104) for calculating second weights from said signals received through said plurality of antennas (101); multiplying means (107, 108) for multiplying said signals memorized in said memorizing means (102) by said first weights, while multiplying said signals received through said plurality of antennas (101) by said second weights when there is a deterioration in channel quality, corresponding to the propagation path switching instruction signal (106); adding means (109) for synthesizing the multiplication results; compensating means (110) for estimating said deterioration in channel quality from the synthesis result and compensating said deterioration; and detecting means (111) for determining and outputting the compensation result to said first weight controlling means (103) and said second weight controlling means (104) as a parameter for the calculation of said first weights and said second weights. The data communication apparatus according to claim 1, wherein said compensating means (110) estimates and compensates a distortion of a propagation path. The data communication apparatus according to any one of claims 1 and 2, wherein, when said deterioration in channel quality occurs, said second weight controlling means (104) calculates the weights. The data communication apparatus according to any one of claims 1-3, wherein while one of said first weight controlling means (103) and said second weight controlling means (104) operates, the other one of said first weight controlling means (103) and said second weight controlling means (104) does not operate. The data communication apparatus according to any one of claims 1-4, wherein a predetermined number of slots of said signals received through said plurality of antennas (101) are memorized in said memorizing means (102) according to an order said signals are input, and output to said first weight controlling means (103) according to the order said signals are memorized. The data communication apparatus according to any one of claims 1-5, wherein said first weight controlling means (103) and said second weight controlling means (104) estimate arrival directions of said signals received through said plurality of antennas (101) by calculating the weights. A data communication apparatus comprising: a plurality of antennas (101); memorizing means (102) for memorizing signals received through said plurality of antennas (101); and weight controlling means (401) for calculating first weights to weight and synthesize the signals memorized in said memorizing means (102) characterized in that said weight controlling means (401), when there is a deterioration in channel quality, suspends the calculation of said first weights and calculates second weights from said signals received through said plurality of antennas (101); and said data communication apparatus further comprises: multiplying means for multiplying said signals memorized in said memorizing means (102) by said first weights, while multiplying said signals received through said plurality of antennas (101) by said second weights when said deterioration in channel quality occurs, corresponding to the propagation path switching instruction signal (106); adding means (109) for synthesizing the multiplication results; compensating means (110) for estimating said deterioration in channel quality from the synthesis result and compensating said deterioration; and detecting means (111) for determining and outputting the compensation result to said weight controlling means (401) as a parameter for the calculation of said first weights and said second weights. The data communication apparatus according to claim 7, wherein, when said weight controlling means (401) is capable of further calculation of the weights, said weight controlling means (401) calculates said first weights and said second weights. The data communication apparatus according to one of claims 7 and 8, wherein when said weight controlling means (401) is not capable of said further calculation of the weights, said weight controlling means (401) calculates said first weights using a first half of a slot of a received signal, said slot being a unit of weight calculation, and said second weights using a second half of the slot of the received signal. The data communication apparatus according to one of claims 1-9, wherein said apparatus multiplies a transmission signal by a weight used to synthesize said signals received through said plurality of antennas (101) and transmits said transmission signal from said plurality of antennas (101). A data communication method comprising the steps of: memorizing signals received through a plurality of antennas (101); and calculating first weights from the memorized signals to weight and synthesize said signals received through said plurality of antennas; characterized by calculating second weights from said signals received through said plurality of antennas; multiplying said memorized signals by said first weights, while multiplying said signals received through said plurality of antennas by said second weights when there is a deterioration in channel quality, corresponding to the propagation path switching instruction signal (106); synthesizing the multiplication results; estimating said deterioration in channel quality from the synthesis result and compensating said deterioration; and detecting the compensation result and outputting said compensation result to said first weight controlling means and said second weight controlling means as a parameter for the calculation of said first weights and said second weights. The data communication method according to claim 11, wherein said second weights are calculated when said deterioration in channel quality occurs. The data communication method according to any one of claims 11 and 12, wherein one of said first weights and said second weights is calculated, the other one of said first weights and said second weights is not calculated. The data communication method according to any one of claims 11-13, wherein a predetermined number of slots of said signals received through said plurality of antennas are memorized according to an order said signals are input, and said first weights are calculated according to the order said signals are memorized. The data communication method according to any one of claims 11-14, wherein arrival directions of said signals received through said plurality of antennas are estimated by the calculation of said first weights and said second weights. The data communication method according to any one of claims 11-15, wherein a transmission signal is multiplied by a weight used to synthesize said signals received through said plurality of antennas, and transmitted from said plurality of antennas.

Inventors: HIRAMATSU KATSUHIKO, MIYA KAZUYUKI, TAKAKUSAKI KEIJI, YUKITOMO HIDEKI, HIRAMATSU, KATSUHIKO, MIYA, KAZUYUKI, TAKAKUSAKI, KEIJI, YUKITOMO, HIDEKI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1998
Main classification: H04B7
IPC codes: H04B7, H04J13, H04B1, H01Q3