JP2009290323A - Radio communication device, and interference electric power reducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an interference wave by discriminatingly using power inversion and diversity reception with a plurality of antennas according to bandwidths in use in a state wherein radio communication devices using mutually different bandwidths in the same frequency band are close to each other. <P>SOLUTION: The radio communication device of a first radio communication system, which receives an interference wave from a second radio communication system, includes: a weighting coefficient calculating means of calculating weighting coefficients corresponding to a plurality of antennas performing power inversion from received signals having been filtered with an interference channel when a first bandwidth is wider than a second bandwidth, and calculating weighting coefficients corresponding to a plurality of antennas performing (maximum ratio composition) diversity from received signals having been filtered with a desired wave channel (a) for inputting received signals of the plurality of antennas from a channel selecting means when the first bandwidth is narrower than the second bandwidth; and an arithmetic means of performing weighting processing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radio communication apparatus and an interference power reduction method for reducing the influence of an interference wave by power inversion using a plurality of antennas in a situation where radio communication apparatuses using different bandwidths in the same frequency band are close to each other. .

  Power inversion is performed by multiplying the received power of multiple antennas (array antennas) by a predetermined weighting coefficient so that the null point of the antenna (the drop point of the directivity pattern) faces in the direction of higher received power. This is an adaptive array technique that reduces the influence of an interference wave having a large reception power as compared with a desired wave by controlling to (Non-patent Document 1).

FIG. 6 shows a configuration example of a receiving system that performs power inversion.
In FIG. 6 (1), the received signals of the antennas 1 and 2 are filtered through the filters 3 and 4 set to the desired wave band, and the desired wave components of the received signals are input to the multipliers 5 and 6 and weighted. It inputs into the coefficient calculation part 7, and calculates the weighting coefficient for power inversion. Multipliers 5 and 6 multiply the desired wave component of each antenna by the weighting coefficient calculated by the weighting coefficient calculation unit 7, respectively, synthesize them by the adder 8, and output the result. Such power inversion is effective when the received power of the interference wave is larger than the received power of the desired wave. As shown in FIG. 6 (2), the antenna in the direction of arrival of the interference wave having a large received power is used. By forming a null point, the interference wave is reduced to emphasize the desired wave, and reception of the desired wave with relatively low reception power is enabled.

  In addition, in wireless LANs and the like, a method for expanding the communication band in order to cope with an increase in communication speed has been studied, and a conventional 20 MHz band wireless communication system and two 20 MHz band channels are used. It is assumed that wireless communication systems whose bandwidths have been expanded are mixed in the same environment. Moreover, as shown in FIG. 7 (1), the channels used by the base station 111 and the wireless terminal 112 in the 40 MHz band system are # 1 to # 2, and the channels used by the base station 121 and the wireless terminal 122 in the adjacent 20 MHz band system. Is # 1, and it is assumed that channel # 1 used by both overlaps.

  Here, for example, when the base station 111 of the 40 MHz band system and the wireless terminal 122 of the 20 MHz band system try to transmit each other, there is an obstacle between them and the radio waves do not reach each other, so the carrier sense does not function, It is assumed that the base station 111 transmits to the wireless terminal 112 and the wireless terminal 122 transmits to the base station 121. At this time, in the wireless terminal 112 of the 40 MHz band system, the reception signal from the base station 111 interferes with the reception signal from the wireless terminal 122 in channel # 1, and the wireless terminal 122 becomes an interference source for the wireless terminal 112. Similarly, in the reverse pattern, the wireless terminal 112 becomes an interference source for the wireless terminal 122.

The maximum output of the 40 MHz band system is specified at 5 [mW / MHz], the maximum output of the 20 MHz band system is specified at 10 [mW / MHz], and the total output is both specified at 200 [mW]. In this case (Ministry of Internal Affairs and Communications, Gazette No. 140), as shown in Fig. 7 (2), the peak power is higher in the 20 MHz band system. Therefore, the wireless terminal 112 shown in FIG. 7 (1) is expected to be greatly affected by the interference wave from the wireless terminal 122.
Nobuyoshi Kikuma, "Adaptive signal processing by array antenna", Chapter 6, Science and Technology Publishing, 1998

  Even in a situation where a 40 MHz band radio terminal and a 20 MHz band radio terminal are in an interference relationship with each other as shown in FIG. 7, ideally, as shown in FIG. What is necessary is just to be able to control so that a null point may face. However, the conventional wireless terminal calculates the power inversion weighting coefficient based on the result of filtering in the desired signal band with the configuration shown in FIG. 6 (1). The following problems occur due to the difference in bandwidth and peak power.

  In the 40 MHz band wireless terminal, as shown in FIG. 8 (1), the overall filtering is performed with the desired 40 MHz band (channels # 1 to # 2), not the 20 MHz band (channel # 1) where interference actually occurs. Will be compared. At this time, if the total power of the interference wave is larger than the desired wave, the null point of the antenna faces the direction of the interference wave as shown in FIG. 8 (2), and the interference wave can be reduced by power inversion. Become. However, if the total power difference between the interference wave and the desired wave is small or the desired wave is larger, the null point of the antenna does not always face in the direction of the interference wave. May fail.

  On the other hand, in the 20 MHz band wireless terminal, the power is compared by filtering in the 20 MHz band of the desired signal as shown in FIG. 9 (1). At this time, the interference power in the part where no interference occurs (channel # 2) is discarded. End up. For this reason, the probability that the power of the desired wave in the 20 MHz band with the high peak power is relatively greater than the power of the interference wave increases, and the direction of arrival of the desired wave is increased by power inversion as shown in FIG. 9 (2). The null point of the antenna will be pointed.

  When the wireless terminal is compatible with both 20 MHz and 40 MHz systems, communication is performed in the 40 MHz band if two channels can be secured, and communication is performed in the 20 MHz band if only one channel is secured. In this case as well, in the method of performing power inversion based on the result of filtering in the band of each desired wave, interference reduction by power inversion is performed with the antenna null point facing the direction of arrival of the desired wave as described above. May fail.

  In particular, in a 20 MHz band wireless terminal, the received power of the desired signal is large, and the probability of directing the null point of the antenna in the direction of arrival of the desired signal due to power inversion increases. Taking advantage of the small size, it is more beneficial to use multiple antennas for diversity reception instead of power inversion.

  The present invention suppresses interference waves by properly using power inversion and diversity reception by a plurality of antennas according to the bandwidth to be used in a situation where wireless communication apparatuses using different bandwidths in the same frequency band are close to each other. An object of the present invention is to provide a wireless communication device and a method for reducing interference power.

  The first invention includes a first wireless communication system that uses a first bandwidth and a second wireless communication system that uses a second bandwidth different from the first bandwidth. In a wireless communication device of a first wireless communication system that receives an interference wave from a communication system, a plurality of antennas and a desired wave channel a having a first bandwidth are grasped, and the first bandwidth is a second bandwidth. Channel selection means for detecting an interference wave channel b having a second bandwidth that overlaps the desired wave channel a from reception signals of at least one of the plurality of antennas when the bandwidth is wider than the first bandwidth; Is a weight corresponding to a plurality of antennas for performing power inversion from a reception signal obtained by filtering the reception signals of a plurality of antennas using an interference wave channel b input from the channel selection means when the signal is wider than the second bandwidth. When the first bandwidth is narrower than the second bandwidth, the maximum ratio combining diversity is obtained from the received signal obtained by filtering the received signals of the plurality of antennas with the desired wave channel a input from the channel selection means. Weighting coefficient calculating means for calculating weighting coefficients corresponding to a plurality of antennas, a plurality of received signals obtained by filtering received signals of the plurality of antennas by a desired wave channel a, and a plurality of weighting coefficients calculated by the weighting coefficient calculating means. And an arithmetic means for outputting a received signal of a desired wave that has been multiplied and further added to suppress the interference wave.

  The weighting coefficient calculating means may be configured to calculate weighting coefficients corresponding to a plurality of antennas that perform maximum ratio combining diversity when the channel selection means does not detect the interference wave channel b that overlaps the desired wave channel a.

  When the first bandwidth corresponds to a plurality of n channels and the second bandwidth is one channel among the n channels, the channel selection means is configured to receive power density P0 in the n channel and the n channel. It is also possible to compare the received power densities P1 to Pn in each one channel obtained by dividing the channel i and set the channel i satisfying Pi> P0 (i is an integer of 1 to n) as the interference wave channel b.

  The second invention includes a first wireless communication system that uses the first bandwidth and a second wireless communication system that uses a second bandwidth different from the first bandwidth. In a method for reducing interference power of a wireless communication apparatus of a first wireless communication system that receives an interference wave from a communication system, the wireless communication apparatus of the first wireless communication system includes a plurality of antennas and a first bandwidth request. When the wave channel a is grasped and the first bandwidth is wider than the second bandwidth, the second bandwidth overlapping the desired wave channel a from the received signal of at least one antenna of the plurality of antennas. Channel selection means for detecting the interference wave channel b, and when the first bandwidth is wider than the second bandwidth, the interference wave channel b is input from the channel selection means to the weighting coefficient calculation means, and the plurality of antennas Receiving When the first bandwidth is narrower than the second bandwidth, a weighting factor is calculated from the channel selection means when the weighting factor corresponding to a plurality of antennas for performing power inversion is calculated from the received signal obtained by filtering the signal with the interference wave channel b The desired wave channel a is input to the calculating means, the weighting coefficient corresponding to the plurality of antennas for performing maximum ratio combining diversity is calculated from the received signal obtained by filtering the received signals of the plurality of antennas with the desired wave channel a, and the reception of the plurality of antennas is performed. Multiply each of the plurality of received signals obtained by filtering the signal with the desired wave channel a and the plurality of weighting coefficients calculated by the weighting coefficient calculating means, and further add them to output the received signal of the desired wave with the interference wave suppressed. To do.

  The weighting coefficient calculation means may calculate the weighting coefficients corresponding to a plurality of antennas for performing maximum ratio combining diversity when the channel selection means does not detect the interference wave channel b overlapping the desired wave channel a.

  When the first bandwidth corresponds to a plurality of n channels and the second bandwidth is one channel among the n channels, the channel selection means is configured to receive power density P0 in the n channel and the n channel. It is also possible to compare the received power densities P1 to Pn in each of the channels obtained by dividing the channel i and set the channel i satisfying Pi> P0 (i is an integer of 1 to n) as the interference wave channel b.

  The present invention performs power inversion using a plurality of antennas when a radio communication apparatus using a wide bandwidth detects an interference wave, and interferes even when using a radio communication apparatus using a narrow bandwidth or a wide bandwidth. A wireless communication device that does not detect waves performs diversity reception using a plurality of antennas. In this way, by properly using the interference power reduction method according to the bandwidth to be used and the presence / absence of detection of the interference wave, it is possible to effectively suppress the interference wave and improve the reception quality.

  Moreover, in power inversion, by calculating a weighting coefficient using the received signal filtered in the interference wave band, the probability of directing the null point of the antenna in the direction of arrival of the interference wave is increased, and the power inversion function effectively Thus, the interference wave can be suppressed.

  The wireless communication apparatus of the present invention is characterized by using a weighting coefficient that becomes power inversion or maximum ratio combining diversity according to a bandwidth to be used when combining reception signals of a plurality of antennas. For example, the wireless communication apparatus of the present invention using the 40 MHz band calculates a weighting coefficient for power inversion and increases the probability of directing the null point of the antenna in the direction of arrival of the interference wave, in the desired wave band (40 MHz). The reception signal filtered in the interference wave band (20 MHz) is used. Further, for example, the wireless communication device of the present invention using a 20 MHz band calculates a weighting coefficient that achieves maximum ratio combining diversity using the fact that the influence of interference from a wireless communication device of 40 MHz band is small. And

  Hereinafter, in the 40 MHz band wireless communication device, the desired wave channel is set to # 1 to # 2, and the 20 MHz band interference wave channel is set to # 1 or # 2, and in the 20 MHz band wireless communication device, the desired wave is set. However, the channel of the desired wave and the interference wave and the respective bandwidths are not limited to this. Absent.

FIG. 1 shows an example of power inversion control of the wireless communication apparatus of the present invention using a 40 MHz band.
The wireless communication apparatus of the present invention using the 40 MHz band does not filter in the conventional desired 40 MHz band (here, channels # 1 to # 2), but instead of the 20 MHz band of the interference wave as shown in FIG. Filter by (channel # 1 here). That is, the evaluation range of the received power used for power inversion is narrowed from the 40 MHz band of the desired wave to the 20 MHz band of the interference wave. As a result, the reception power of the interference wave in the 20 MHz band is often evaluated higher than the reception power of the desired wave, and the probability that the null point of the antenna is directed toward the arrival direction of the interference wave as shown in FIG. And can suppress the interference wave.

FIG. 2 shows an example of diversity control of the wireless communication apparatus of the present invention using the 20 MHz band.
The wireless communication apparatus of the present invention using the 20 MHz band performs maximum ratio combining diversity by filtering in the conventional desired signal 20 MHz band (here, channel # 1) without using power inversion. As a result, as shown in FIG. 2 (2), it is possible to obtain a diversity effect by combining the maximum ratios of received signals of a plurality of antennas without directing the null point of the antenna in the direction of arrival of a desired wave having a large received power. . In the wireless communication apparatus of the present invention using the 40 MHz band of FIG. 1, maximum ratio combining diversity is performed without using power inversion when no interference wave is detected in the desired wave band.

FIG. 3 shows a configuration example of the wireless communication apparatus of the present invention.
In FIG. 3, antennas 1 and 2 and an antenna characteristic control unit 10 are connected, and one of the antennas (here, antenna 1) and a channel selection unit 20 are connected. The channel selection unit 20 grasps the use bandwidth (20 MHz / 40 MHz) of the own station and the desired wave channel a. When the use bandwidth is 40 MHz, the received signal of the antenna 1 is monitored and the power inversion is performed. The target interference wave channel b is detected, and the desired wave channel a (40 MHz), the interference wave channel b (20 MHz), and the mode switching signal c1 instructing the power inversion are output. When the use bandwidth is 20 MHz or when the use bandwidth is 40 MHz and no interference wave is detected, the desired wave channel a (20 MHz / 40 MHz) and the mode switching signal c2 instructing the maximum ratio combining diversity are output.

  The antenna characteristic control unit 10 includes filters 3 and 4 in which the band (40 MHz / 20 MHz) of the desired wave channel a is set from the channel selection unit 20 and filters 11 and 12 in which the band (20 MHz) of the interference wave channel b is set. And the received signals of the antennas 1 and 2 are respectively filtered. Outputs of the filters 3 and 4 (desired wave channel a: 40 MHz / 20 MHz) are connected to the multipliers 5 and 6 and to the selector 13. Outputs of the filters 11 and 12 (interference wave channel b: 20 MHz) are connected to the selector 13. The selector 13 selects the outputs of the filters 11 and 12 according to the mode switching signal c1 set from the channel selection unit 20, selects the outputs of the filters 3 and 4 according to the mode switching signal c2, and calculates the weighting coefficients respectively. Input to section 14. The weighting coefficient calculation unit 14 calculates the power inversion weighting coefficient from the outputs of the filters 11 and 12 (interference wave channel b: 20 MHz) in accordance with the mode switching signal c1 set from the channel selection unit 20, and switches the mode. The weighting coefficient of the maximum ratio combining diversity is calculated from the outputs of the filters 3 and 4 (desired wave channel a: 40 MHz / 20 MHz) according to the signal c2, and set in the multipliers 5 and 6, respectively. The multipliers 5 and 6 multiply the received signals of the desired wave channel a by the corresponding weighting coefficients, and add the respective multiplication results by the adder 8 so that the interference wave is generated by power inversion or maximum ratio combining diversity. The suppressed received signal is sent to the signal processing unit 30 at the next stage.

FIG. 4 shows a processing procedure of the wireless communication apparatus of the present invention.
In FIG. 4, the channel selection unit 20 grasps the use bandwidth (20 MHz / 40 MHz) of the own station and the information on the desired wave channel a, and performs processing according to the use bandwidth (S1, S2). When the bandwidth used is 40 MHz, the received signal of the antenna 1 is monitored to detect the interference wave channel b that is the target of power inversion (S3), and if there is an interference wave, the desired wave channel a and the interference wave channel b The mode switching signal c1 is notified to the antenna characteristic control unit 10 (S4, S5). The antenna characteristic control unit 10 filters the reception signals of the antennas 1 and 2 with the filters 11 and 12 in the band of the interference wave channel b, and inputs them to the weighting coefficient calculation unit 14 via the selector 13 (S6). The weighting coefficient calculation unit 14 calculates a power inversion weighting coefficient from the received signal of the interference wave channel b, and sets it in the multipliers 5 and 6 (S7).

  On the other hand, when the use bandwidth is 20 MHz or there is no interference wave in step S4, the channel selection unit 20 notifies the antenna characteristic control unit 10 of the desired wave channel a and the mode switching signal c2 (S2, S4, S8). . The antenna characteristic control unit 10 filters the reception signals of the antennas 1 and 2 with the filters 3 and 4 in the band of the desired wave channel a, and inputs them to the weighting coefficient calculation unit 14 via the selector 13 (S9). The weighting coefficient calculation unit 14 calculates the weighting coefficient for maximum ratio combining diversity from the received signal of the desired wave channel a, and sets the weighting coefficient in the multipliers 5 and 6 (S10).

  Here, a method of detecting the interference wave channel b by the channel selector 20 when the use bandwidth is 40 MHz will be described with reference to FIG.

  In FIG. 5 (1), the channel selection unit 20 when the use bandwidth is 40 MHz branches the received signal of the antenna 1 into three and inputs it to the received power density comparison unit 24 through the filters 21, 22, and 23. Here, the band of the filter 21 is set to the desired wave channels # 1 to # 2, the band of the filter 22 is set to the channel # 1, and the band of the filter 23 is set to the channel # 2. The reception power density comparison unit 24 compares the reception power densities P0, P1, and P2 of the outputs of the filters 21, 22, and 23 to determine an interference channel.

  FIG. 5 (2) shows a case where there is no interference wave in the desired wave channels # 1 to # 2, and the received power densities P0, P1, and P2 are all the desired wave power density, and P0 = P1 = P2. Become.

  FIG. 5 (3) shows the case where there is an interference wave (20 MHz) in channel # 1, and the received power density P0 is the sum of the power density of the desired wave and the power density of the interference wave, and the received power density P1 is The sum of the power density of the desired wave and the power density of the interference wave, and the received power density P2 is the power density of the desired wave, and P1> P0> P2.

  FIG. 5 (4) shows a case where there is an interference wave (20 MHz) in channel # 2, and the received power density P0 is the sum of the power density of the desired wave and the power density of the interference wave, and the received power density P1 is The power density of the desired wave is obtained, and the received power density P2 is the sum of the power density of the desired wave and the power density of the interference wave, and P2> P0> P1.

  As described above, the channel selection unit 20 when the used bandwidth is 40 MHz sets the desired wave channel a (channels # 1 to # 2) in the filters 3 and 4. Further, when P1> P0 is detected, channel # 1 is set in filters 11 and 12 as interference wave channel b. Further, when P2> P0 is detected, channel # 2 is set in filters 11 and 12 as interference wave channel b. Further, when P0 = P1 = P2, there is no interference wave in the desired wave channels # 1 to # 2, so the mode switching signal c2 is input to the selector 13 and the weighting coefficient calculation unit 14, and the maximum ratio combining is performed. Control to perform diversity.

The figure which shows the power inversion control example of the radio | wireless communication apparatus of this invention using a 40-MHz band. The figure which shows the diversity control example of the radio | wireless communication apparatus of this invention using a 20 MHz band. The figure which shows the structural example of the radio | wireless communication apparatus of this invention. The figure which shows the process sequence of the radio | wireless communication apparatus of this invention. The figure which shows the function of the channel selection part 20 whose use bandwidth is 40 MHz. The figure which shows the structural example of the receiving system which performs power inversion. The figure explaining the interference relationship of a 40 MHz band radio | wireless terminal and a 20 MHz band radio | wireless terminal. The figure explaining the power inversion in a 40 MHz band radio | wireless terminal. The figure explaining the power inversion in a 20 MHz band radio | wireless terminal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Antenna 3, 4 Filter 5, 6 Multiplier 7 Weighting coefficient calculation part 8 Adder 10 Antenna characteristic control part 11, 12 Filter 13 Selector 14 Weighting coefficient calculation part 20 Channel selection part 21, 22, 23 Filter 24 Reception power Density comparison unit 30 Signal processing unit

Claims (6)

There are a first wireless communication system that uses the first bandwidth and a second wireless communication system that uses a second bandwidth different from the first bandwidth, and an interference wave from the second wireless communication system. In the wireless communication device of the first wireless communication system that receives
Multiple antennas,
When the desired wave channel a of the first bandwidth is grasped and the first bandwidth is wider than the second bandwidth, the desired wave channel a is received from the received signals of at least one of the plurality of antennas. Channel selection means for detecting an interference wave channel b of the second bandwidth overlapping the wave channel a;
When the first bandwidth is wider than the second bandwidth, the power inversion is performed from the reception signal filtered by the interference wave channel b input from the channel selection means, the reception signals of the plurality of antennas A weighting coefficient corresponding to a plurality of antennas is calculated, and when the first bandwidth is narrower than the second bandwidth, the received signal of the plurality of antennas is input to the desired wave channel a from the channel selection means. Weighting coefficient calculating means for calculating a weighting coefficient corresponding to the plurality of antennas that performs maximum ratio combining diversity from the filtered received signal;
The interference signals are obtained by multiplying the plurality of reception signals obtained by filtering the reception signals of the plurality of antennas with the desired wave channel a by the plurality of weighting coefficients calculated by the weighting coefficient calculating means, respectively, and adding them together. And a calculation means for outputting a received signal of a desired wave with suppressed noise. The wireless communication device according to claim 1,
The weighting coefficient calculating means calculates the weighting coefficients corresponding to the plurality of antennas that perform the maximum ratio combining diversity when the channel selecting means does not detect the interference wave channel b overlapping the desired wave channel a. There is a wireless communication device. The wireless communication device according to claim 1,
The channel selection means, when the first bandwidth corresponds to a plurality of n channels and the second bandwidth is one of the n channels, the received power density P0 in the n channel, The received power density P1 to Pn in each channel obtained by dividing the n channel is compared, and the channel i satisfying Pi> P0 (i is an integer of 1 to n) is defined as the interference wave channel b. A wireless communication device. There are a first wireless communication system that uses the first bandwidth and a second wireless communication system that uses a second bandwidth different from the first bandwidth, and an interference wave from the second wireless communication system. In the method of reducing interference power of the wireless communication device of the first wireless communication system that receives
The wireless communication device of the first wireless communication system grasps a plurality of antennas and a desired wave channel a of the first bandwidth, and the first bandwidth is wider than the second bandwidth. And channel selection means for detecting the interference wave channel b of the second bandwidth overlapping the desired wave channel a from the reception signals of at least one of the plurality of antennas,
When the first bandwidth is wider than the second bandwidth, the interference wave channel b is input from the channel selection means to the weighting coefficient calculation means, and the reception signals of the plurality of antennas are transmitted to the interference wave channel b. Calculating a weighting coefficient corresponding to the plurality of antennas that performs power inversion from the received signal filtered in step, and when the first bandwidth is narrower than the second bandwidth, the channel selection means calculates the weighting coefficient calculation means. The desired wave channel a is input to the received signal obtained by filtering the received signals of the plurality of antennas by the desired wave channel a to calculate a weighting coefficient corresponding to the plurality of antennas for performing maximum ratio combining diversity, A plurality of received signals obtained by filtering antenna received signals by the desired wave channel a, and the weighting coefficient; Interference power reduction method characterized by leaving a plurality of weighting coefficients calculated by means multiplies each further outputs the reception signal of the desired wave suppressing the interference wave by adding them. The interference power reduction method according to claim 4,
The weighting coefficient calculating means calculates the weighting coefficients corresponding to the plurality of antennas for performing the maximum ratio combining diversity when the channel selecting means does not detect the interference wave channel b overlapping the desired wave channel a. A characteristic interference power reduction method. The interference power reduction method according to claim 4,
The channel selection means, when the first bandwidth corresponds to a plurality of n channels and the second bandwidth is one of the n channels, the received power density P0 in the n channel, The received power densities P1 to Pn in each one channel obtained by dividing the n channel are compared, and the channel i satisfying Pi> P0 (i is an integer of 1 to n) is defined as the interference wave channel b. Interference power reduction method.

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