Adaptive antenna transmitting/receiving apparatus

The present invention relates to an adaptive antenna transmitter / receiver which is a transmitter / receiver using an adaptive antenna, and more particularly to an adaptive antenna transmitter / receiver which generates a transmit antenna weight based on a receiver antenna weight.

[0002] In general, in a mobile communication system, interference from other users, that is, multi-user interference is a major factor in limiting system capacity. Therefore, in order to increase the system capacity, it is considered that an adaptive antenna technology that suppresses the received signal in a specific direction (interference wave direction) at the time of reception and avoids interference in an unnecessary direction at the time of transmission is effective. ..

[0003] FIG. 2 shows a conventional example of a transmission / reception device (adaptive antenna transmission / reception device) using such an adaptive antenna. This conventional adaptive antenna transmitter / receiver has N antenna elements 101, as shown in FIG.₁~101_NAnd N multipliers 102₁~102_N, Adder 103, receive antenna weight generation circuit 104, antenna weight conversion circuit 105, and N multipliers 106.₁~106_NIt is composed of and.

[0004] Multiplier 102₁~102_NIs the antenna element 101₁~101_NReceived antenna weight W = (w) generated by the receiving antenna weight generation circuit 104 with respect to the received signal from₁, W₂, ..., w_N) Are multiplied to perform weighting multiplication. Adder 103 is a multiplier 102₁~102_NThe received signals for each antenna weighted by are added together and output as one received data.

[0005] The receiving antenna weight generation circuit 104 takes the received data output from the adder 103 as an input, and generates a weighting coefficient as the receiving antenna weight W so that the received data becomes an optimum value.

[0006] The operation of the receiving antenna weight generation circuit 104 is MMSE (Minimum Mean Squared Error) in which the weighting coefficient is adaptively updated so that the mean squared error of the weighted received signal and the reference signal is minimized. Control is commonly used. LMS (Least Mean Square) and RLS (Recursive Least Square) algorithms are known as algorithms that realize MMSE. In the present invention, the algorithm used in the receiving antenna weight generation circuit 104 is not particularly limited.

[0007] The receiving antenna weight W = (w) generated by the receiving antenna weight generation circuit 104.₁, W₂, ..., w_N) Is the multiplier 102₁~102_NIt is used for weighting the received signal and is input to the antenna weight conversion circuit 105.

[0008] The antenna weight conversion circuit 105 transmits the receiving antenna weight W generated by the receiving antenna weight generation circuit 104 to the transmitting antenna weight W'= (w'.₁, W'₂, ..., w'_N). This conversion is to correct the amplitude / phase deviation between the branches of the RF transmission circuit, or to correct the transmission / reception frequency difference when the transmission / reception frequencies are different, as in the FDD (Frequency Division Duplex) system. This is basically performed for the purpose of generating a transmitting antenna weight W'for forming a pattern similar to the directivity pattern formed by reception.

Multiplier 106₁~106_NMultiplies the transmission data and the transmission antenna weight W'output from the antenna weight conversion circuit 105, respectively.

[0010] In the conventional adaptive antenna transmitter / receiver shown in FIG. 2, N antenna elements 101.₁~101_NAre arranged in an array, and each antenna element 101 is processed by signal processing.₁~101_NBy adaptively controlling the weighting coefficient of, the control is performed so as to increase the antenna gain (directivity) in a specific direction. On the other hand, at the time of transmission, the receiving antenna weight is calibrated and the generated transmitting antenna weight is multiplied by the transmission signal of each user to have directivity in the desired wave user direction and reduce interference given to other users. Send to do. An adaptive antenna transmitter / receiver having such a configuration is described in the following document [1].

[0011] For example, as a method of calculating the optimum reception weight, the reception antenna weight is set so that the average square error after RAKE synthesis generated by using the pilot symbol after despreading and the judgment information data symbol as reference signals is minimized. The method of control is shown in the following document [2].

[0012] Further, as a method of generating the transmitting antenna weight, a method of using the transmitting antenna weight generated based on the antenna weight generated above is described in the following document [3].

[0013] [1] NTT DoCoMo Technical Journal Vol.8 No.1 (Apr.2000) [2] S.Tanaka, M.Sawahashi and F.Adachi, Pilot symbol-assisted decision-directed coherent adaptive array diversity for DS-CDMA mobile radio reverse link , IEICE Trans. Fundamentals, Vol.E80-A, pp.2445-2454, (Dec.1997) [3] Tanaka, Harada, Ihara, Sawabashi, Adachi, Adaptation in W-CDMA Outdoor Experimental Characteristics of Antenna Array Diversity Reception , IEICE Technical Report RCS99-127, pp.45-50 (Oct. 1999) In the conventional adaptive antenna transmitter / receiver shown in FIG. 2, the transmitting antenna weight is generated based on the receiving antenna weight generated by reception. The purpose of this is to apply the directivity pattern formed at the time of reception to the transmission as it is. However, for example, (1) when the receiving antenna weight generation is in the process of convergence and the optimum weight is not formed (2) when the receiving line quality is poor and it is difficult to generate the optimum receiving antenna weight (3) shadowing. When the receiving line is momentarily interrupted due to such reasons (4) When the reception is abnormal due to a device failure or the like, or when the optimum receiving antenna weight is not generated, the transmitting antenna weight is also not optimal. Therefore, not only the directivity to the desired station is not formed, but also the interference given to other users becomes large, and it is conceivable that not only the reception characteristics but also the transmission characteristics are significantly deteriorated.

[0014] As a conventional technique for controlling the transmitting antenna weight so as to have an optimum value, there are those described in JP-A-2000-22611, JP-A-2001-217759 and the like.

[0015] Japanese Unexamined Patent Publication No. 2000-22611 describes an adaptive antenna transmitter / receiver that is provided with an arrival direction estimation circuit and estimates the arrival direction by the arrival direction estimation circuit to correct the transmission antenna weight. However, in this conventional adaptive antenna transmitter / receiver, when the reception line quality deteriorates, the arrival direction cannot be estimated and the optimum transmission weight control cannot be performed. In some cases, erroneous control is performed and the transmission characteristics deteriorate significantly. There is a possibility that it will end up.

[0016] Further, Japanese Patent Application Laid-Open No. 2001-217759 describes an adaptive antenna transmitter / receiver that controls a transmitting antenna weight based on an interference degree calculated by an interference degree calculation unit. However, even with this conventional adaptive antenna transmitter / receiver, if the quality of the receiving line deteriorates, the degree of interference itself cannot be calculated and optimum transmission weight control cannot be performed. In some cases, erroneous control is performed and the transmission characteristics deteriorate significantly. There is a possibility that it will end up.

[0017] [Problem to be Solved by the Invention] In the conventional adaptive antenna transmitting / receiving device described above, if the optimum receiving antenna weight is not generated, the transmitting antenna weight is also not optimal, so that directivity for a desired station is not formed. On the contrary, there is a problem that the interference given to other users becomes large, and not only the reception characteristics but also the transmission characteristics are remarkably deteriorated.

[0018] An object of the present invention is to provide an adaptive antenna transmitting / receiving device capable of preventing significant deterioration of transmission characteristics when an optimum receiving antenna weight cannot be generated.

[Means for Solving the Problems] In order to achieve the above object, the adaptive antenna transmitter / receiver of the present invention has a receiver antenna weight for a plurality of antenna elements and reception signals from the plurality of antenna elements. A plurality of first multipliers that perform weighted multiplication by multiplying each of the above, and additions that add up the received signals for each antenna weighted by the plurality of first multipliers and output as one received data. A device, a reception quality measurement circuit that measures the reception quality of the reception data output from the adder, and a weighting coefficient that takes the reception data output from the adder as input and optimizes the reception data. A receiving antenna weight generation circuit that generates the receiving antenna weight as the receiving antenna weight, and an antenna weight conversion circuit that converts the receiving antenna weight generated by the receiving antenna weight generation circuit into the transmitting antenna weight. When the reception quality measured by the reception quality measurement circuit exceeds a preset threshold value, the transmission antenna weight output from the antenna weight conversion circuit is output as it is, and the reception quality sets the threshold value. If it falls below, instead of the transmitting antenna weight output from the antenna weight conversion circuit,<u style="single">A preset value is used as the transmitting antenna weight.</u>It is provided with a transmitting antenna weight control circuit for output and a plurality of second multipliers for multiplying the transmitting data and the transmitting antenna weight output from the transmitting antenna weight control circuit.

[0022] According to the present invention, the reception quality of the received data is measured by the reception quality circuit, and when the reception quality falls below a preset threshold value, the transmission antenna weight control circuit is performed by the antenna weight conversion circuit. Do not use the generated transmit antenna weight as it is, but use a preset value for the transmit antenna.<u style="single">weight</u>Therefore, it is possible to prevent the antenna element from being controlled by an erroneous transmitting antenna weight and the transmission characteristics from being significantly deteriorated.

Further, the transmitting antenna weight control circuit has a value only for the weight corresponding to a specific antenna element as a preset value, and all the weights corresponding to the other antenna elements are 0. It may be output as such a transmission antenna weight.

[0024] Further, the reception quality measuring circuit measures the reception quality based on any one of the signal power to interference power ratio, the bit error rate, and the block error rate of the received data which is the output of the addition circuit. May be good.

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of an adaptive antenna transmitter / receiver according to an embodiment of the present invention. In FIG. 1, the same components as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

[0027] The adaptive antenna transmission / reception device of the present embodiment is provided with a reception quality measurement circuit 107 and a transmission antenna weight control circuit 108 newly provided with respect to the conventional adaptive antenna transmission / reception device shown in FIG.

[0028] In the adaptive antenna transmitter / receiver of the present embodiment, the antenna weight conversion circuit 105 and the multiplier 106₁~106_NSince the transmitting antenna weight control circuit 108 is provided between the and, the multiplier 106 in the present embodiment₁~106_NRather than multiplying the transmit data and the transmit antenna weight W'output from the antenna weight conversion circuit 105, respectively, is multiplying the transmit data by the transmit antenna weight W'output from the transmit antenna weight control circuit 108. Are done respectively.

[0029] The present embodiment is characterized in that a reception quality measurement circuit 107 and a transmission antenna weight control circuit 108 are provided in an adaptive antenna transmission / reception device that generates a transmission antenna weight based on a reception antenna weight.

[0030] The reception quality measurement circuit 107 determines the reception quality of the reception data output from the adder 103 as SIR (Signal-to-Noise power Ratio) and BER (Bit Error Rate). Rate), BLER (BLock Error Rate), etc. are measured and notified to the transmitting antenna weight control circuit 108.

The transmitting antenna weight control circuit 108 determines the transmitting antenna weight W by inputting the transmitting antenna weight W'which is the output of the antenna weight conversion circuit 105 and the receiving quality which is the output of the receiving quality measuring circuit 107. Specifically, the transmitting antenna weight control circuit 108 determines whether or not the transmitting antenna weight W'converted by the antenna weight conversion circuit 105 is actually used. As a criterion for the determination, the reception quality measurement circuit is used. Use the reception quality measured in 107.

When the reception quality measured by the reception quality measurement circuit 107 exceeds a preset threshold value, the transmission antenna weight control circuit 108 receives the transmission antenna weight W'from the antenna weight conversion circuit 105. As is the multiplier 106₁~106₂Output to.

Then, when the reception quality is lower than the threshold value, the transmitting antenna weight control circuit 108 performs control so that the transmitting antenna weight, which is the output of the antenna weight conversion circuit 105, is not used as it is.

[0034] As an example of this control, for example, when the reception quality falls below a certain threshold value, the previously calculated antenna weight can be continuously used as it is, and the transmitting antenna weight can be prevented from being updated. .. In this case, the transmitting antenna weight control circuit 108 compares the reception quality, which is the output of the reception quality measurement circuit 107, with the preset threshold value, and if the reception quality exceeds the threshold value, Multiplier 106 the transmit antenna weight, which is the output of the antenna weight conversion circuit 105.₁~106_NThe output is output as it is, and the output transmission antenna weight is stored internally. Then, when the reception quality falls below the threshold value, the transmitting antenna weight control circuit 108 replaces the transmitting antenna weight which is the output of the antenna weight conversion circuit 105 with the stored transmitting antenna weight (finally received). Output the transmitting antenna weight when the quality exceeds the threshold value).

[0035] This makes it possible to prevent erroneous detection of the arrival direction due to deterioration of the reception characteristic from spreading to the transmitting antenna weight.

Alternatively, the transmitting antenna weight control circuit 108 outputs the transmitting antenna weight W output from the antenna weight conversion circuit 105 when the receiving quality measured by the receiving quality measuring circuit 107 falls below a predetermined threshold value. Instead of', the preset value is set as the transmitting antenna weight W'and the multiplier 106₁~106_NIt may be output to.

[0037] This preset value is, for example, W = (1, 0, ..., 0), that is, w.₁= (1.0,0.0), w₂~ w_NA weighting coefficient such as = (0.0, 0.0) that has a value only for the weight corresponding to a specific antenna element and 0 for all others.

[0038] When such control is performed, the directivity gain at the time of transmission obtained when the receiving antenna weight generation circuit 104 correctly estimates the arrival direction is lost, but the receiving antenna weight is lost. It is possible to avoid the risk that the generation circuit 104 mistakenly estimates the arrival direction and erroneously forms a directivity other than the desired station at the time of transmission, causing interference to other users. Further, when the receiving line is momentarily interrupted for a long time and the arrival direction is significantly changed, it is possible to avoid deterioration of the characteristics because the transmission directivity cannot follow.

[Effect of the Invention] As described above, according to the present invention, when the reception quality of the received data deteriorates and the optimum receiving antenna weight cannot be generated, the transmission generated based on the receiving antenna weight is performed. Since the stored transmitting antenna weight, that is, the transmitting antenna weight when the reception quality finally exceeds the threshold value is used without using the antenna weight, or the preset value is used as the transmitting antenna weight. It is possible to prevent the transmission characteristics from being significantly deteriorated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of an adaptive antenna transmitter / receiver according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional adaptive antenna transmitter / receiver.

[Description of Code] 101₁~101_N Antenna element 102₁~102_N Multiplier 103 Adder 104 Receive antenna weight generation circuit 105 Antenna weight conversion circuit 106₁~106_N Multiplier 107 Reception quality measurement circuit 108 Transmit antenna weight control circuit