JP2013009386A - Radio communication method and radio communication device - Google Patents

Radio communication method and radio communication device Download PDF

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JP2013009386A
JP2013009386A JP2012171072A JP2012171072A JP2013009386A JP 2013009386 A JP2013009386 A JP 2013009386A JP 2012171072 A JP2012171072 A JP 2012171072A JP 2012171072 A JP2012171072 A JP 2012171072A JP 2013009386 A JP2013009386 A JP 2013009386A
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data rate
terminal
wireless communication
unit
step
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Hoi Do
方偉 童
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Kyocera Corp
京セラ株式会社
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Abstract

In a wireless communication method with a plurality of terminals using an adaptive modulation method using a space division multiple access method, detection of the moving speed of each terminal is unnecessary, and throughput is improved in consideration of the QoS of each terminal. Provided are a wireless communication method and a wireless communication apparatus.
A radio communication apparatus estimates a downlink data rate of each terminal based on a data rate acquisition unit that acquires a downlink data rate of each terminal and an uplink signal quality of each terminal. A data rate estimating unit 140, a data rate difference calculating unit 150 for obtaining a difference between the data rate estimated by the data rate estimating unit and the data rate acquired by the data rate acquiring unit for each terminal, and a data rate difference calculating A channel allocation control unit 180 that controls channel allocation to each terminal based on the data rate difference obtained by the unit.
[Selection] Figure 1

Description

  The present invention relates to a wireless communication method and a wireless communication apparatus.

  In the space division multiple access (SDMA) system, a plurality of users share the same frequency and the same time slot, and a space is formed by a beam pattern formed by an adaptive array antenna (AAA) installed in a base station. Thus, users are separated from each other to achieve multiple access that avoids mutual interference. In this system, a propagation path in a time division multiple access (TDD) communication system is used to appropriately form a beam pattern that avoids mutual interference according to the latest radio wave propagation status of each terminal. Take advantage of the reversibility of That is, the base station calculates the AAA weight based on the uplink signal received from each terminal, corrects as necessary, and multiplies the downlink signal by this weight for transmission. In this way, the weight to multiply the downlink signal is calculated based on the uplink signal, so that when the terminal moves at high speed, the base station uses the base station to calculate the weight when transmitting the downlink signal. In some cases, the terminal is already away from the position at which the terminal transmitted the uplink signal. In this case, the effect of suppressing interference by the beam pattern formed by AAA is weakened, the signal reception quality at each terminal deteriorates, and the system throughput decreases.

  In order to deal with the above-described problems, interference generated by the movement of the terminal by allocating the basic channel and the spatial channel in the order of the moving speed of each terminal in the prior art channel allocation method in consideration of the moving speed of the terminal. Has been proposed to improve the throughput characteristics (see Patent Document 1).

  However, in Patent Document 1, it is necessary to detect the moving speed (that is, fading speed) of each terminal. Several methods for detecting the moving speed have been proposed, but many methods that require further verification in terms of effectiveness, practicality, accuracy, etc. are inconvenient. In addition, there is a method using a GPS (Global Positioning System) with high effectiveness and high accuracy, but there is a problem that the cost is high and the fading speed cannot be detected.

  Further, even if channel allocation is performed considering only the movement of the terminal, a space is allocated to a high-priority terminal (for example, a terminal performing VoIP: Voice over Internet Protocol) that requires QoS (Quality of Service), for example. When a channel is assigned, there is a problem that it becomes easy to receive interference from another spatial channel of the same frequency, and a problem that an appropriate service cannot be provided despite a high priority occurs. In this specification, “basic channel” refers to an available carrier (frequency) and time slot, and “spatial channel” uses the same frequency and time slot as the basic channel, but the AAA of the base station It is assumed that the channel is spatially multiplexed by the antenna beam pattern to be formed. It should be noted that although spatial multiplexing can be performed by performing spatial multiplexing on the basic channel, such a channel is also referred to as a “basic channel” for convenience of explanation.

Japanese Patent Laid-Open No. 9-215052

  The present invention solves the above-described problems and uses a space division multiple access scheme (and a frequency division multiple access scheme) in a wireless communication apparatus (base station) that performs wireless communication with a plurality of terminals using an adaptive modulation scheme. It is an object of the present invention to provide a wireless communication method and a wireless communication device that do not require detection of the moving speed of each terminal and improve the throughput in consideration of the QoS of each terminal.

  In order to solve the above-described problem, a wireless communication method according to a first invention uses a space division multiple access method (and a frequency division multiple access method) to perform wireless communication with a plurality of terminals (mobile stations) using an adaptive modulation method. A wireless communication method in a wireless communication apparatus (base station) for performing a data rate estimation step for estimating a downlink data rate of each terminal based on uplink signal quality of each terminal, and a downlink in each terminal The data rate acquisition step of acquiring (receiving) the data rate, the data rate estimated by the data rate estimation step, and the data rate difference between the data rate acquired by the data rate acquisition step for each terminal (CPU Data rate difference calculation step to be obtained) and using the data rate difference calculation step Meta based on the data rate difference, characterized in that it comprises a channel assignment control step of controlling the channel allocation to each terminal.

  Further, in the radio communication method according to the second invention, the data rate estimation step uses the association between the uplink signal quality and the downlink data rate, from the uplink signal quality of each terminal, A data rate in the downlink of the terminal is estimated.

  The wireless communication method according to a third aspect of the present invention is the wireless communication method (wherein the data rate difference calculating step determines a data rate difference for each of the plurality of terminals), and the allocation control step includes the plurality of terminals. The terminals are preferentially assigned to channels that are not spatially divided (channels for the frequency division multiple access scheme) in descending order of the data rate difference.

  According to a fourth aspect of the present invention, there is provided a wireless communication method (wherein the data rate difference calculating step determines a data rate difference for each of the plurality of terminals), and the allocation control step is configured to connect the plurality of terminals to the plurality of terminals. The terminals are preferentially assigned to the spatially divided channels in order from the smallest data rate difference among the terminals.

  According to a fifth aspect of the present invention, there is provided a wireless communication method for acquiring information on QoS (Quality of Service) of the plurality of terminals (QoS attributes (VoIP, file transfer, video stream, etc.) transmitted by each mobile station). The allocation control step further controls channel allocation to the plurality of terminals based on the data rate difference obtained in the data rate difference calculation step and the QoS information acquired in the QoS acquisition step. It is characterized by.

  As described above, the solving means of the present invention has been described as a method. However, the present invention can be realized as an apparatus, a program, and a storage medium storing the program for carrying out these methods. It should be understood that these are included in the scope.

  For example, a radio communication apparatus (base station) according to the sixth aspect of the present invention that realizes the present invention as an apparatus adapts to a plurality of terminals (mobile stations) using a space division multiple access scheme (and a frequency division multiple access scheme). A wireless communication device (base station) that performs wireless communication using a modulation method, and based on the uplink signal quality of each terminal, a data rate estimation unit that estimates the downlink data rate of each terminal; A data rate obtaining unit for obtaining a downlink data rate, and a data rate for obtaining a data rate difference between the data rate obtained by the data rate obtaining unit and the data rate estimated by the data rate estimating unit for each terminal. Channel allocation control for controlling channel allocation to each terminal based on difference calculation unit and data rate difference obtained by said data rate difference calculation unit Characterized in that it comprises a and.

  As described above, by appropriately assigning the basic channel and the spatial channel to the terminal, it is possible to provide a wireless communication method that can be easily realized at low cost, which can improve throughput and guarantee QoS.

1 is a block diagram of a wireless communication device according to the present invention. It is the figure which showed the basic channel and the spatial channel of the wireless channel used by this invention with the allocation order. It is a flowchart of the channel allocation process of the radio | wireless communication method by this invention. It is a figure of the flowchart of the process which adjusts the arrangement | sequence order of each mobile station based on QoS among the channel allocation processes of the radio | wireless communication method by this invention, and the figure which shows the example of adjustment of an arrangement | sequence order.

  Prior to specific description of the present invention, the principle of the present invention will be described. In the TDD scheme, the same frequency is used for downlink (downlink, transmission from the base station to the terminal) and uplink (uplink, transmission from the terminal to the base station). Therefore, when each terminal is stationary, Reversibility is established. Therefore, the reception quality of the uplink signal at the base station and the reception quality of the downlink signal at the terminal have a certain relationship, and the base station can estimate the response characteristic of the downlink signal from the response characteristic of the uplink signal. it can. Table 1 shows the relationship of the received signal quality between the downlink signal and the uplink signal when this channel reversibility is established. As shown in Table 1, a certain relationship is established between the reception quality of the downlink signal and the uplink signal. Note that this table is provided as an example and is not an exact number.

In wireless communication using adaptive modulation, the radio wave propagation environment (interference, fading, etc.) is monitored, and the modulation method (modulation class) for transmitting and receiving data is adaptively changed according to the state. I am letting. For example, data is transmitted to a terminal that is close to the base station and moves at a low speed in a good radio wave propagation environment (line condition) using a 64QAM modulation method that is suitable when the intensity of the received signal is strong, Data is transmitted to a terminal that is far from the base station and has a poor line condition or is moving at high speed using a BPSK modulation method suitable for a case where the quality of the received signal is weak. Table 2 shows the relationship between the quality of the received signal, the modulation scheme to be taken at that quality, and the data rate that can be taken with that modulation scheme. This table is also shown as an example.

From Tables 1 and 2, the relationship shown in Table 3 is established between the reception quality of the uplink signal and the data rate of the downlink signal.

The base station estimates the circuit state used by the terminal from the uplink signal reception quality received from the terminal, and estimates the modulation scheme, that is, the data rate to be adopted when transmitting the downlink signal based on Table 3. . However, if the terminal is moving, because the base station is already away from where the terminal transmitted the uplink signal used by the base station to estimate the modulation scheme when the base station transmits the downlink signal, The terminal is displaced from the direction of the antenna beam formed by AAA. In this case, the performance of SDMA deteriorates, and the downlink modulation scheme is shifted to a modulation scheme with a small number of multi-values, or a transmission error to the terminal and subsequent retransmission processing occur, and the final downlink signal Quality, that is, the data rate deteriorates. Table 4 shows an example of this phenomenon.

As shown in Table 4, there is a difference between the downlink data rate predicted by the base station and the final downlink data rate due to, for example, the terminal moving as described above. The present invention proposes a new channel allocation method using the phenomenon shown in Table 4, that is, the difference between the downlink data rate predicted by the base station and the final downlink data rate.

  Hereinafter, embodiments of the wireless communication apparatus according to the present invention will be described in detail with reference to the drawings. As a wireless communication apparatus, a base station will be described as an example. FIG. 1 is a block diagram of a wireless communication apparatus according to the present invention. The radio communication apparatus 100 includes an array antenna, an adaptive array antenna AAA transmission / reception unit 110, a signal quality estimation unit 120, a correspondence relationship storage unit 130, a data rate estimation unit 140, a data rate difference calculation unit 150, a QoS control unit 160, and a sorting unit 170. A channel allocation unit 180 and a data rate monitoring unit 190. The adaptive array antenna AAA transmitting / receiving unit 110 is known in the prior art, and a description thereof will be omitted.

  The signal quality estimation unit 120 estimates the reception quality of the uplink signal of each mobile station (terminal) (assuming M pieces). There are many quality estimation methods, but as an example, estimation is performed according to the following equation using a known portion in the received signal frame.

Here, SINR is an indicator (Signal to Interference And Noise Ratio) indicating the quality of the received signal, U (i) (i = 1,..., N) is a known part in the received signal frame, R (i) (I = 1,..., N) is a reference signal, and * is a complex conjugate. The received signal quality may be expressed by CNR (Carrier to Noise Ratio), but here SINR and CNR are not particularly distinguished and are referred to as signal quality. Usually, SINR (or CNR) is displayed in dB. The reception quality of the uplink signal is estimated for all mobile stations connected to the wireless communication line.

  The correspondence relationship storage unit 130 stores, as a table in advance, the relationship between the downlink modulation scheme determined from the reception quality of the uplink signal and the corresponding data rate as shown in Table 3. Based on the reception quality of the uplink signal of the mobile station estimated by the signal quality estimation unit 120 and the table of Table 3 stored in the correspondence relationship storage unit 130, the data rate estimation unit 140 is configured to determine whether the downlink of the mobile station Estimate the data rate. For example, based on Table 3, if the reception quality of an uplink signal of a certain mobile station is -4.9 dB or more and less than -0.1 dB, the downlink signal modulation method of this mobile station is estimated as QPSK. The data rate is estimated to be 245 kbps. The downlink modulation scheme and data rate estimation are performed for all mobile stations connected to the wireless communication line.

  The data rate monitoring unit 190 acquires the data rate of the actual downlink signal and outputs it to the data rate difference calculation unit 150. When the base station has information related to the data rate of the downlink signal in advance, the corresponding data rate may be output to the data rate difference calculation unit 150 from the information. Here, a data rate monitoring unit 190 is provided in the sense that information on the data rate of the actual downlink signal is necessary for the data rate estimated by the base station. If there is no information about the data rate, it can be calculated by the following formula.

Data rate = (Number of bits successfully transmitted) / (Calculation period)
The “calculation period” in the above equation indicates a time range for calculating the data rate, and is set to 0.1 to 0.2 seconds, for example. “The number of bits successfully transmitted” refers to the number of bits successfully transmitted within the calculation period, that is, the number of bits successfully received by the mobile station. Note that the calculation of the data rate is not limited to the number of bits, and may be the number of frames.

  The data rate difference calculation unit 150 calculates the difference between the data rate estimated by the data rate estimation unit 140 and the actual downlink signal data rate of the corresponding mobile station input from the data rate monitoring unit 190 by the following equation. calculate.

Data rate difference = (predicted data rate)-(actual data rate)
Further, the calculation of the above equation may be performed for all connected mobile stations, tabulated, and stored in the storage unit (not shown) or the correspondence storage unit 130.

  A large data rate difference means that the radio wave propagation environment when the mobile station transmits the uplink signal used by the base station to estimate the data rate of the downlink signal changes due to the movement of the mobile station, and the like. , Which means that the degree of change is great. Therefore, a mobile station with a large data rate difference should adopt a more durable channel because the channel state may be degraded. Considering this, the result of the data rate difference calculated by the data rate difference calculation unit 150 is output to the sorting unit 170, and the sorting unit 170 arranges the mobile stations in descending order of the data rate difference. The arrangement order may be tabulated and stored in a storage unit (not shown). For example, if there are M (# 1, # 2,... #M) mobile stations and the calculated data rate difference is assumed to be # 1> # 2>. The result is # 1, # 2,... #M, and a table as shown in Table 5 is created.

When there are multiple mobile stations with the same data rate difference, the data rate estimated by the base station or the actual data rate is compared between the mobile stations, and the mobile stations with the lowest data rate are ordered. Arrange. When mobile stations having the same data rate exist, these mobile stations may be arranged at random.

  The QoS control unit 160 includes information on QoS acquired from the mobile station (for example, whether the data transmitted / received by the mobile station is any one of VoIP, video streaming, file transfer, Web browsing, etc., and The identification number of each mobile station) is output to sorting section 170. Based on the QoS information input from the QoS control unit 160, the sorting unit 170 adjusts the arrangement order so that important mobile stations that require QoS (for example, mobile stations performing VoIP) are prioritized. For example, among the mobile stations arranged based on the data rate difference, the important mobile stations that require QoS are rearranged so as to be placed at the top of the arrangement order. When there are a plurality of important mobile stations, the plurality of important mobile stations are arranged in the order of the data rate difference, and the arrangement order in which all of them are placed in the higher order while maintaining the order is rearranged.

  As another rearrangement method, while monitoring the spatial multiplexing number and communication speed of an important mobile station, first, the arrangement order is rearranged by one, and the spatial multiplexing number of the mobile station is reduced, or It is possible to check whether or not the communication speed has been improved. If the communication speed has been improved, the adjustment of the arrangement order is terminated.

  The channel assignment unit 180 assigns a basic channel and a spatial channel to each mobile station based on the arrangement result by the sort unit 170. A specific example will be described below. FIG. 2 is a table showing basic channels and spatial channels that can be used for wireless communication, together with channel numbers and the order of assignment to each channel. As shown in the figure, assuming that there are N basic channels (C10, C20,..., CN0), the spatial channel of the basic channel C10 (the spatially separated channel having the same frequency and the same time slot as C10) ) Is assumed to be L (C11, C12,..., C1L) (in this case, referred to as L + 1 spatial multiplexing). Similarly, the basic channel C20 has L spatial channels (C21, C22,..., C2L), the basic channel C30 has L spatial channels (C31, C32,..., C3L), and N basic channels. Assume that there are L spatial channels for each. In this case, as shown in the figure, a basic channel is preferentially assigned to each mobile station, and a spatial channel is assigned when there is no basic channel to be assigned. Here, it is assumed that the number of mobile stations M> the number N of basic channels. When M ≦ N, the number of basic channels is sufficient for the mobile station, and assignment of a spatial channel to the mobile station becomes unnecessary.

  The channel assignment unit 180 is arranged by the sorting unit 170 and adjusted based on the QoS information from the QoS control unit 160, and the arrangement order of the mobile stations (for convenience of explanation, the arrangement order is # 1,. 2), the basic channel and the spatial channel are allocated in the allocation order shown in FIG. For example, among mobile stations # 1,... #M, channel C10 (basic channel) of allocation order 1 is allocated to # 1 which is the highest priority, and channel C20 of allocation order 2 is allocated to # 2. To the mobile station #M.

  The above-described channel allocation method will be described using a flowchart. FIG. 3 shows a flowchart of channel assignment control of the wireless communication method according to the present invention. First, each mobile station transmits a session start request to the wireless communication apparatus (base station) 100 (and a radio access network including its control system), is permitted to start the session, and the session is started. To do. The radio communication apparatus 100 estimates the reception quality of the uplink signal of each connected mobile station, for example, by calculating the SINR described above (step S11). Next, based on the relationship between the modulation class of the downlink signal to be adopted according to the quality of the uplink signal, which is stored in advance as a table, and the corresponding data rate, the downlink of each mobile station is estimated based on the estimated uplink signal quality. The data rate of the link signal is estimated (step S12). Thereafter, the data rate monitoring unit 190 acquires the data rate of the actual downlink signal of each mobile station (step S13), and the data rate difference calculation unit 150 calculates the data rate estimated by the data rate estimation unit 140 and the data A difference from the actual downlink signal data rate of each mobile station input from the rate monitoring unit 190 is calculated numerically (using a calculation means such as a CPU) (step S14). Since the processing from steps S11 to S14 is performed for all connected mobile stations, it is determined whether or not all mobile stations have been processed (step S15).

  When the calculation of the data rate difference for all the mobile stations is completed, the sorting unit 170 arranges the mobile stations in descending order of the data rate difference based on the calculated data rate difference (step S16). Next, the QoS control unit 160 acquires the QoS attribute of each mobile station, and outputs the QoS attribute to the sorting unit 170. The sorting unit 170 performs a process of adjusting the arrangement order based on the data rate difference based on the QoS attribute. This is performed (step S17). The adjustment process will be described with reference to the flowchart of FIG. 4A and the adjustment example of each mobile station in FIG. The sorting unit 170 acquires information on QoS attributes (such as identification numbers of important mobile stations that require QoS) from the QoS control unit 160 (step S21), and determines whether there is an important mobile station (step S21). Step S22). If there is an important mobile station, the arrangement order created in step S16 is adjusted so that the important mobile station is in the higher rank (step S23). When there are a plurality of important mobile stations, they are arranged higher while maintaining the arrangement order due to the data rate difference. For example, in the example of FIG. 4B, the arrangement order based on the data rate difference is from the highest priority (# 2, # 1, # 4, #A, # 3, #B). Since #A and #B are important mobile stations that require QoS, the arrangement order is adjusted, and the arrangement order (#A, #B) based on the data rate difference between #A and #B is adjusted. While maintaining this, it is rearranged in the order of arrangement (#A, #B, # 2, # 1, # 4, # 3). Note that the above processing is not performed when there is no mobile station that requires QoS.

  Returning to the flowchart of FIG. Thereafter, in step S18, the channel allocating unit 180 allocates basic channels from the mobile stations with higher priority based on the arrangement order by the sorting unit 170. When there is no free basic channel to be allocated, spatial channels are sequentially allocated using FIG. The uplink signal quality estimation, downlink signal data rate estimation, data rate difference calculation, arrangement, and channel assignment are performed in a predetermined cycle. This predetermined cycle depends on the communication system, but may be set to 1 to 2 seconds, for example.

  The effect of the present invention will be described again. According to the present invention, in a wireless communication method with a plurality of terminals using an adaptive modulation method using a space division multiple access method, it is possible to perform channel assignment control in consideration of the radio wave environment of the channel used by each terminal. Throughput can be improved. Also, since a channel that is resistant to interference is preferentially assigned to terminals that require QoS, QoS can be guaranteed. Furthermore, in the present invention, it is not necessary to detect the moving speed and fading speed of each terminal, so that the method and apparatus according to the present invention can be realized at low cost and easily.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each means, each step, etc. can be rearranged so as not to be logically contradictory, and a plurality of means, steps, etc. can be combined into one or divided. .

DESCRIPTION OF SYMBOLS 100 Wireless communication apparatus 110 Adaptive array antenna (AAA) transmission / reception part 120 Signal quality estimation part 130 Correspondence relation preservation | save part 140 Data rate estimation part 150 Data rate difference calculation part 160 QoS control part 170 Sort part 180 Channel allocation part 190 Data rate monitoring part C10, C20, ..., CN0 basic channel C11, C12, ..., C1L spatial channel C21, C22, ..., C2L spatial channel C31, C32, ..., C3L spatial channel # 1 to # 4, #A, # B terminal (mobile station)

Claims (2)

  1. A wireless communication method in a wireless communication device that performs wireless communication with a plurality of terminals by an adaptive modulation method using a space division multiple access method,
    A data rate estimating step for estimating the downlink data rate of each terminal based on the uplink signal quality of each terminal;
    A data rate acquisition step of acquiring a downlink data rate in each terminal;
    A data rate difference calculating step for obtaining a data rate difference between the data rate estimated by the data rate estimating step and the data rate acquired by the data rate acquiring step for each terminal;
    A channel assignment control step for controlling channel assignment to each terminal based on the data rate difference obtained in the data rate difference calculating step;
    A wireless communication method comprising:
  2. A wireless communication device that performs wireless communication with a plurality of terminals using an adaptive modulation method using a space division multiple access method,
    A data rate estimation unit that estimates the downlink data rate of each terminal based on the uplink signal quality of each terminal;
    A data rate acquisition unit for acquiring a downlink data rate in each terminal;
    A data rate difference calculation unit for obtaining a data rate difference between the data rate acquired by the data rate acquisition unit and the data rate estimated by the data rate estimation unit for each terminal;
    A channel assignment control unit that controls channel assignment to each terminal based on the data rate difference obtained by the data rate difference calculation unit;
    A wireless communication apparatus comprising:

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JP2004531976A (en) * 2001-06-14 2004-10-14 クゥアルコム・インコーポレイテッドQualcomm Incorporated Method and apparatus for processing data for transmission in a multi-channel communication system using selective channel inversion
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