JP2012050106A - Radio device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication technology for suppressing the decline of interference elimination capability while suppressing the increase of a calculation amount.SOLUTION: A radio device includes: a communication part for executing communication by multicarrier signals with a radio device to be a communication object through a plurality of antennas; a division part 30 for dividing the multicarrier signals used for the communication in the communication part into a plurality of groups at least in a frequency domain; and a processing part 16 for executing adaptive array signal processing with each of the plurality of groups divided in the division part as a unit. The division part 30 acquires line quality for the multicarrier signals, and when the line quality is worse than a threshold, allocates continuous subcarriers in the frequency domain included in the multicarrier signals to each group.

Description

  The present invention relates to communication technology, and more particularly to a radio apparatus that receives a multicarrier signal by a plurality of antennas.

  In wireless communication, effective use of limited frequency resources is generally desired. In order to effectively use frequency resources, for example, radio waves of the same frequency are repeatedly used at a distance as close as possible. In that case, communication quality deteriorates due to co-channel interference from a nearby base station apparatus or the like using the same frequency. One technique for preventing deterioration in communication quality due to co-channel interference is the adaptive array antenna technique. The adaptive array antenna technology performs combining after weighting signals received at a plurality of antennas with different weighting factors.

  For adaptive updating of the weighting factor, for example, an adaptive algorithm such as an RLS (Recursive Least Squares) algorithm or an LMS (Least Mean Squares) algorithm is used. The weighting factor may be calculated based on the response characteristics in the transmission path from the transmission side to the reception side. Such adaptive array signal processing may be applied to a multicarrier signal such as an OFDM (Orthogonal Frequency Division Multiplexing) signal (see, for example, Patent Document 1).

JP 2006-186421 A

  In adaptive array signal processing, a reception weight vector is derived. On the other hand, since the multicarrier signal is formed of a plurality of subcarriers, the amount of calculation increases when the reception weight vector is derived for each subcarrier. In order to suppress such an increase in calculation amount, a common reception weight vector is used across a plurality of subcarriers. However, when the interference level is different for each subcarrier, even if a common reception weight vector is used, sufficient interference removal capability is not exhibited.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a communication technique that suppresses a decrease in interference cancellation capability while suppressing an increase in calculation amount.

  In order to solve the above-described problem, a radio apparatus according to an aspect of the present invention includes a receiving unit that receives a multicarrier signal via a plurality of antennas, and a plurality of groups in the frequency domain of the multicarrier signal received by the receiving unit. And a processing unit that executes adaptive array signal processing in units of each of a plurality of groups divided by the dividing unit. The division unit acquires channel quality for each subcarrier in the frequency domain included in the multicarrier signal, and sets a plurality of groups according to the channel quality.

  Another aspect of the present invention is also a wireless device. This device includes a communication unit that performs communication using a multicarrier signal with a wireless device that is a communication target via a plurality of antennas, and a multicarrier signal that is used for communication in the communication unit at least in a frequency domain. A division unit that divides the signal into a plurality of groups, and a processing unit that performs adaptive array signal processing in units of each of the plurality of groups divided by the division unit. The division unit acquires the channel quality for the multicarrier signal, and when the channel quality is worse than the threshold, for each group, continuous subcarriers in the frequency domain included in the multicarrier signal. Assign.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of interference removal capability can be suppressed, suppressing the increase in calculation amount.

It is a figure which shows the structure of the receiver which concerns on the Example of this invention. It is a figure which shows the format of the signal received in the receiver of FIG. It is a figure which shows the structure of the process part of FIG. It is a flowchart which shows the reception process by the receiver of FIG. It is a flowchart which shows the reception process which concerns on the modification of this invention. It is a flowchart which shows the reception process which concerns on another modification of this invention. It is a figure which shows the structure of the base station apparatus which concerns on another modification of this invention. It is a flowchart which shows the allocation process by the base station apparatus of FIG.

  Before describing the present invention specifically, an outline will be given first. Embodiments described herein relate generally to a receiving apparatus that includes a plurality of antennas and receives an OFDM signal. The OFDM signal forms a packet signal or a burst signal (hereinafter, the OFDM signal forming the packet signal or the burst signal is also referred to as “OFDM signal”) in the time domain. The receiving apparatus receives OFDM signals with a plurality of antennas, and performs adaptive array signal processing on the OFDM signals. In adaptive array signal processing, a reception weight vector is derived. However, when it is derived for each subcarrier, the amount of calculation increases. On the other hand, interference removal capability is required by adaptive array signal processing. In order to suppress a decrease in interference cancellation capability while suppressing an increase in calculation amount, the receiving apparatus according to the present embodiment executes the following processing.

  The receiving apparatus performs carrier sense in advance for each subcarrier, and acquires an interference level for each subcarrier. Further, if the interference level between adjacent subcarriers is close, the receiving apparatus collects them as one group. Further, by repeating and executing the same processing for the next subcarrier, the receiving apparatus divides the OFDM signal into a plurality of groups. That is, subcarriers with close interference levels are grouped together. It is assumed that a plurality of subcarriers included in one group are continuous, and the maximum value of the number of subcarriers included in one group is predetermined. The receiving apparatus generates a common reception weight vector for each group, and performs adaptive array signal processing using the generated reception weight vector.

  FIG. 1 shows a configuration of a receiving apparatus 100 according to an embodiment of the present invention. The receiving apparatus 100 includes a first antenna 10a, a second antenna 10b, a third antenna 10c, a fourth antenna 10d, and a first RF unit 12a, a second RF unit 12b, and a third RF. Including a first processing unit 16a, a second processing unit 16b, an N-th processing unit 16n, a combining unit 18, a measuring unit 20, and a control unit 22, which are collectively referred to as a unit 12c, a fourth RF unit 12d, a dividing unit 14, and a processing unit 16. . The control unit 22 includes a determination unit 24.

  The plurality of RF units 12 are connected while being associated with the plurality of antennas 10. The RF unit 12 receives the OFDM signal via the antenna 10. The OFDM signal is transmitted from a transmission device (not shown). Further, the OFDM signal forms a burst signal in the time domain, and a known signal may be arranged in the front part of the burst signal, and a data signal may be arranged subsequently. Furthermore, the OFDM signal has a radio frequency. When receiving the OFDM signal in the radio frequency band, the RF unit 12 performs frequency conversion on the OFDM signal in the radio frequency band. As a result, the RF unit 12 generates a baseband OFDM signal.

  Furthermore, the RF unit 12 performs FFT (Fast Fourier Transform) on the baseband OFDM signal. As a result, the time-domain OFDM signal is converted into a frequency-domain OFDM signal. An OFDM signal in the frequency domain (hereinafter simply referred to as “OFDM signal”) has values corresponding to a plurality of subcarriers, and each value is formed by an in-phase component and a quadrature component. Should be indicated by twice as many signal lines. However, here, for the sake of clarity, the OFDM signal is shown by one signal line. The RF unit 12 outputs the OFDM signal to the dividing unit 14. In the carrier sense period, the RF unit 12 outputs an interference signal converted into the frequency domain (hereinafter simply referred to as “interference signal”) to the measurement unit 20.

  FIG. 2 shows a format of a signal received by receiving apparatus 100. This corresponds to the frequency domain OFDM signal generated in the RF unit 12. The vertical axis in the figure corresponds to the frequency axis. As illustrated, X subcarriers having subcarrier (hereinafter referred to as “SC”) number “1” to SC number “X” are arranged in the frequency axis direction. Further, the horizontal axis in the figure corresponds to the time axis. As shown in the figure, Y symbols from symbol number “1” to T number “Y” are arranged in the time axis direction. Hereinafter, in order to clarify the explanation, a combination of a subcarrier and a symbol is referred to as “data”. Further, the data includes the aforementioned known signal. Returning to FIG.

  The measurement unit 20 receives an interference signal from the RF unit 12 during the carrier sense period. Since four RF units 12 are included, four types of interference signals are input to the measurement unit 20. Here, each interference signal is also formed by X SCs and Y Ts as shown in FIG. The measurement unit 20 derives the power of the interference signal (hereinafter referred to as “interference level”) for each data unit. Specifically, since each data is formed by an in-phase component and a quadrature component, the measurement unit 20 calculates the size of each data. Furthermore, since there are three other data corresponding to the same symbol as the same subcarrier, the measurement unit 20 derives an interference level for one data by integrating these data. When the measurement unit 20 derives the interference level for the interference signal, the measurement unit 20 outputs the interference level to the determination unit 24.

  The determination unit 24 receives the interference level from the measurement unit 20. The determination unit 24 predefines a plurality of stages with respect to the interference level. For example, threshold values “A1” and “A2” (A1 <A2) are defined, and three stages such as a stage less than A1, a stage greater than A1 and less than A2, and a stage greater than A2 are defined. . The determination unit 24 associates each piece of data with one of a plurality of stages by comparing the interference level with the threshold value for each data unit. Such processing is performed not only on the data in the frequency axis direction but also on the data in the time axis direction, but in the following, in order to simplify the description, it will be described as processing for a predetermined symbol. That is, the determination unit 24 associates each piece of data in the frequency axis direction included in a predetermined symbol with one of the stages.

  The determination unit 24 determines whether or not the steps in adjacent subcarriers are the same. If they are the same, the determination unit 24 further determines whether or not the adjacent subcarrier stages are also the same. For example, the determination unit 24 compares the lowest frequency SC1 with the adjacent SC2. If both stages are the same, SC3 is added to the comparison. By repeating such processing, the determination unit 24 divides the OFDM signal into a plurality of groups. Here, the group is a set of continuous subcarriers corresponding to the same stage. Hereinafter, a group included in the group is also referred to as a “group”.

  That is, the determination unit 24 acquires the interference level of the interference signal for each subcarrier, and sets a plurality of groups according to the interference level. Note that the determination unit 24 determines in advance the maximum number of subcarriers (hereinafter referred to as “maximum number”) that can be included in one group, and when the maximum number is reached, the adjacent subcarriers are in the same stage. Even so, this is not included in the group. The determination unit 24 generates a correspondence between the group and the subcarrier as group information. Further, the determination unit 24 outputs group information to the dividing unit 14, the processing unit 16, and the combining unit 18.

  The dividing unit 14 receives the OFDM signal from each of the four RF units 12. The dividing unit 14 receives group information from the determining unit 24. The dividing unit 14 divides each of the OFDM signals into a plurality of groups based on the group information. For example, when the first group is defined as SC numbers “1” to “3” for a predetermined symbol, the dividing unit 14 changes the SC numbers “1” to “3” from each OFDM signal. A corresponding signal is extracted and output to the first processing unit 16a. The dividing unit 14 outputs each of the plurality of groups to each processing unit 16.

  The processing unit 16 is provided while being associated with each of the plurality of groups. Each processing unit 16 performs adaptive array signal processing on the group received from the dividing unit 14. In adaptive array signal processing, a reception weight vector is generally calculated from four signals (hereinafter referred to as “input vectors”) corresponding to one subcarrier and a reference signal. In adaptive array signal processing, input vectors are weighted by reception weight vectors, and then they are combined. The processing unit 16 outputs the combined result (hereinafter referred to as “combined signal”) to the combining unit 18.

  An adaptive algorithm, such as an LMS algorithm, is used to calculate the received weight vector. Here, in each processing unit 16, one type of reception weight vector is calculated and applied to all subcarriers in the group. That is, the reception weight vector for one subcarrier in the group is calculated, and this is also used for other subcarriers. The first processing unit 16a to the Nth processing unit 16n execute the above processing in common, but the groups to be processed are different from each other.

  The combining unit 18 receives a combined signal from each of the plurality of processing units 16. The synthesizer 18 synthesizes a plurality of synthesized signals. Since each combined signal corresponds to a different subcarrier, the combining unit 18 arranges them in the order of the SC number. The synthesizing unit 18 demodulates and outputs the synthesized result. The control unit 22 controls timing for the entire receiving apparatus 100.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it is realized by a program having a communication function loaded in the memory. Describes functional blocks realized by collaboration. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 3 is a diagram illustrating a configuration of the processing unit 16. The processing unit 16 includes a first multiplication unit 40 a, a second multiplication unit 40 b, a third multiplication unit 40 c, a fourth multiplication unit 40 d, an addition unit 42, and a weight calculation unit 44 that are collectively referred to as the multiplication unit 40.

  The weight calculation unit 44 derives a reception weight vector by executing the LMS algorithm. Since the LMS algorithm is a known technique, a description thereof is omitted here. The weight calculation unit 44 calculates a reception weight vector for one subcarrier in the group. The weight calculation unit 44 outputs the received weight vector to the multiplication unit 40.

  The multiplier 40 receives the input vector and the reception weight vector. In addition, the multiplication unit 40 weights the input vector with the reception weight vector, and then outputs the input vector to the addition unit 42. The multiplication unit 40 receives an input vector corresponding to at least one subcarrier included in the group, and receives one type of value as a reception weight vector corresponding to these. The adder 42 receives the weighting results from the adder 42 and integrates them to generate the above-described combined signal.

  The operation of the receiving apparatus 100 having the above configuration will be described. FIG. 4 is a flowchart showing a reception process by the reception device 100. The measurement unit 20 performs carrier sense in all sections (S10). The determination unit 24 divides the OFDM signal into a plurality of groups based on the carrier sense result (S12). The determination unit 24 sets i to 0 (S14). The processing unit 16 derives a reception weight vector using the data in the group (S16). The processing unit 16 and the synthesizing unit 18 perform demodulation processing (S18). If i> n is not satisfied (N in S20), the determination unit 24 adds 1 to i (S22), and returns to Step 16. On the other hand, if i> n (Y in S20), the process is terminated.

  Hereinafter, modifications of the present invention will be described. Similar to the embodiment, the modification relates to a receiving apparatus that divides an OFDM signal into a plurality of groups and performs adaptive array signal processing on the groups. The receiving apparatus according to the embodiment performs adaptive array signal processing for each group. However, the receiving apparatus according to the modification performs adaptive array signal processing only for some groups in order to reduce the amount of calculation. Specifically, the receiving apparatus selects a group having a high interference level, and performs adaptive array signal processing on the selected group.

  The receiving apparatus 100 according to the modification is the same type as the receiving apparatus 100 shown in FIG. Therefore, here, the description will focus on the differences. After defining a plurality of groups, the determination unit 24 confirms the stage for each group. Based on the stage, the determination unit 24 identifies a group having a high interference level among the plurality of groups. The number of groups to be specified may be determined in advance, or all groups having an interference level greater than the threshold value may be specified. The determination unit 24 adds the identified group to the above-described group information. Further, the determination unit 24 outputs group information to the dividing unit 14, the processing unit 16, and the combining unit 18.

  The processing unit 16 receives group information from the determination unit 24. The processing unit 16 corresponding to the identified group performs adaptive array signal processing. That is, adaptive array signal processing is preferentially executed for a group whose line quality is deteriorated. Note that the processing unit 16 corresponding to the unidentified group selects one of the OFDM signals corresponding to each of the plurality of antennas 10 and outputs it as a combined signal to the combining unit 18. Even if adaptive array signal processing is not performed on a group with a low interference level, it is considered that the degradation of reception quality is small.

  FIG. 5 is a flowchart showing a reception process according to a modification of the present invention. The measurement unit 20 performs carrier sense in all sections (S50). The determination unit 24 divides the OFDM signal into a plurality of groups based on the carrier sense result (S52). The determination unit 24 selects a group with a high interference level (S54). The processing unit 16 derives a reception weight vector using the data in the group (S56). The processing unit 16 and the synthesizing unit 18 perform demodulation processing (S58).

  Another modification of the present invention will be described. Another modified example relates to a receiving apparatus that divides an OFDM signal into a plurality of groups and performs adaptive array signal processing on the groups, as in the embodiment. Up to now, a plurality of groups have been defined in the frequency domain. However, in another modification, a plurality of groups are defined even in the time domain. That is, in one subcarrier, the front and rear of the burst signal are associated with different groups.

  In that case, a group with a small number of input vectors used for deriving a reception weight vector, that is, a group with a small number of data may occur. If the received weight vector is derived using such data when the number of data is small, the accuracy of the received weight vector may be reduced. Therefore, a receiving apparatus according to another modification increases the number of data by combining a group with a small number of data with another group.

  The receiving apparatus 100 according to another modification is the same type as the receiving apparatus 100 shown in FIG. Therefore, here, the description will focus on the differences. The determination unit 24 defines a plurality of groups. Here, the stage is determined for each data, and the data may be divided into a plurality of groups in the time direction. The determination unit 24 compares the number of data included in each group with a threshold value. When the number of data is smaller than the threshold value, that is, when the group size is small, the determination unit 24 joins the group to another group. Here, the determination unit 24 combines the group with the group corresponding to the subcarrier adjacent to the group or the adjacent symbol. When there are a plurality of such groups, the determination unit 24 preferentially couples to a group having a higher interference level than the interference level of the group. Such a combination is repeatedly executed until the number of data reaches a threshold value or more.

  FIG. 6 is a flowchart showing a reception process according to another modification of the present invention. The measurement unit 20 performs carrier sense in all sections (S100). The determination unit 24 divides the OFDM signal into a plurality of groups based on the carrier sense result (S102). The determination unit 24 sets i to 0 (S104). If the number of data in the group is smaller than the threshold value (Y in S106), the determination unit 24 moves the data in group i to group i + 1 (S112). Further, the determination unit 24 adds 1 to i (S116), and returns to Step 106. On the other hand, if the number of data in the group is not smaller than the threshold (N in S106), the processing unit 16 derives a reception weight vector using the data in the group (S108). The processing unit 16 and the synthesizing unit 18 perform demodulation processing (S110). If i> n is not satisfied (N in S114), the determination unit 24 adds 1 to i (S116), and returns to Step 106. On the other hand, if i> n (Y in S114), the process is terminated.

  Still another modification of the present invention will be described. The reception device has been described so far, but in another modification, a base station device having the reception function described so far will be described. The base station apparatus performs communication with the terminal apparatus by assigning a channel to the terminal apparatus to be communicated. Here, it is assumed that the base station apparatus executes OFDMA in the frequency domain and TDMA in the time domain. There are a downlink channel from the base station apparatus to the terminal apparatus and an uplink channel from the terminal apparatus to the base station apparatus. Here, these channels are collectively referred to simply as “channels”. Sometimes.

  The base station apparatus measures the interference level of the entire OFDM signal, and compares the measured interference level with a threshold value. When the interference level is larger than the threshold value, one group is defined by a certain number of consecutive subcarriers and a certain number of consecutive symbols. A group is assigned as a channel for one terminal device. On the other hand, if the interference level is not greater than the threshold value, an arbitrary subcarrier or symbol is assigned to the terminal device as a channel.

  FIG. 7 shows a configuration of base station apparatus 150 according to still another modification of the present invention. The base station apparatus 150 includes a first antenna 10a, a second antenna 10b, a third antenna 10c, a fourth antenna 10d, and a first RF unit 12a, a second RF unit 12b, 3RF unit 12c, fourth RF unit 12d, first allocation unit 30, first processing unit 16a, second processing unit 16b, N-th processing unit 16n, second allocation unit 32, measurement unit 20, A control unit 22 is included. The control unit 22 includes a determination unit 24 and an allocation unit 26.

  The antenna 10, the RF unit 12, the first allocating unit 30, the processing unit 16, and the second allocating unit 32 are configured to receive the antenna 10, the RF unit 12, the dividing unit 14, the processing unit 16, and the combining unit shown in FIG. The same processing as that of the unit 18 is executed. That is, the first assigning unit 30 corresponds to the dividing unit 14, and the second assigning unit 32 corresponds to the combining unit 18. On the other hand, the 2nd allocation part 32, the process part 16, the 1st allocation part 30, RF part 12, and the antenna 10 perform the process reverse to a reception process as a transmission process. Here, the processing unit 16 derives a transmission weight vector during the transmission process. That is, the RF unit 12, the first allocation unit 30, the processing unit 16, and the second allocation unit 32 execute communication using an OFDM signal with a terminal device (not shown) via the plurality of antennas 10.

  The measurement unit 20 measures the interference level for the entire interference signal shown in FIG. This can be said to be an integrated value of interference levels for each data. The measurement unit 20 outputs the measured interference level to the determination unit 24. The determination unit 24 compares the interference level with a threshold value. When the interference level is larger than the threshold value, the determination unit 24 defines one group by a certain number of consecutive subcarriers and a certain number of consecutive symbols. For example, one group is defined by three consecutive subcarriers and three consecutive symbols. Here, a group corresponds to a channel. On the other hand, when the interference level is not greater than the threshold value, the determination unit 24 defines any subcarrier or symbol as a channel. The determination unit 24 outputs information on the specified channel to the allocation unit 26. The assigning unit 26 assigns a channel to the terminal device. Since a well-known technique should just be used for channel allocation, description is abbreviate | omitted here.

  FIG. 8 is a flowchart showing allocation processing by the base station apparatus 150. The measurement unit 20 performs carrier sense in all sections (S150). If the interference level is greater than the threshold value (Y in S152), the determination unit 24 defines a group formed by a fixed number of data (S154). The assigning unit 26 assigns consecutive groups to one terminal device (S156). On the other hand, if the interference level is not greater than the threshold (N in S152), the assigning unit 26 assigns an arbitrary group to one terminal device (S158).

  According to the embodiment of the present invention, since the OFDM signal is divided into a plurality of groups and adaptive array signal processing is executed in units of groups, an increase in the amount of calculation can be suppressed. In addition, since groups are defined according to the interference level in units of subcarriers, subcarriers having similar interference levels can be combined into one group. Further, since subcarriers having the same interference level are grouped into one group, it is possible to suppress a decrease in interference removal capability even if a common reception weight vector is used for each group. In addition, since the decrease in interference removal capability is suppressed, the reception quality can be improved. Further, since a common reception weight vector is used for each group, it is possible to suppress a decrease in interference removal capability while suppressing an increase in calculation amount.

  Also, if the group size is small, the group is integrated into another group, so that it is possible to suppress a decrease in the estimation accuracy of the received weight vector. In addition, since adaptive array signal processing is preferentially executed for a group whose line quality has deteriorated, the amount of calculation can be further reduced while suppressing a decrease in interference removal capability. Also, since the channel allocation unit is changed according to the interference level of the entire OFDM signal, it is possible to suppress a decrease in interference removal capability while suppressing an increase in the amount of calculation. Also, if the interference level is high, consecutive subchannels and symbols are allocated to one terminal device, so that it is possible to suppress a decrease in interference removal capability while suppressing an increase in calculation amount.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the determination unit 24 defines a plurality of groups in the frequency domain. However, the present invention is not limited to this. For example, the determination unit 24 may define a plurality of groups in the time domain. According to this modification, the interference removal capability can be improved.

  10 antenna, 12 RF unit, 14 dividing unit, 16 processing unit, 18 combining unit, 20 measuring unit, 22 control unit, 24 determining unit, 40 multiplying unit, 42 adding unit, 44 weight calculating unit, 100 receiving device.

Claims (1)

A communication unit that performs communication using a multicarrier signal with a wireless device that is a communication target via a plurality of antennas;
A division unit that divides a multicarrier signal used for communication in the communication unit into a plurality of groups at least in a frequency domain;
A processing unit that performs adaptive array signal processing in units of each of the plurality of groups divided by the dividing unit,
The division unit obtains channel quality for a multicarrier signal, and when the channel quality is worse than a threshold value, for each group, a continuous subband in the frequency domain included in the multicarrier signal is obtained. A radio apparatus characterized by allocating a carrier.

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