JP2010130186A - Base station and method of arranging sub burst region in the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology with which the arrangement of an HARQ sub burst region can be suppressed over a plurality of sub channels. <P>SOLUTION: A first arrangement part arranges an HARQ burst region in a down sub frame to be transmitted from a transmission part to a communication terminal. A second arrangement part arranges the HARQ (Hybrid Automatic Repeat reQuest) sub burst region 58 allocated to the communication terminal by securing a plurality of slots for sub burst in the order in the HARQ burst region. The second arrangement part secures at least the first slot 59a and the next slot 59b to be secured in the HARQ burst region along a symbol direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a base station in WiMAX (Worldwide Interoperability for Microwave Access) and a method of arranging subburst areas in the base station.

  Conventionally, various techniques relating to wireless communication have been proposed. Some wireless communication technologies use an automatic repeat request (ARQ) method. In this ARQ method, when a terminal receives a downlink frame from a base station and finds an error in data in the frame, the terminal requests the base station to retransmit the erroneous data.

  On the other hand, there is a wireless communication technique called WiMAX, which performs communication using the OFDMA method. In WiMAX, a hybrid automatic repeat request (HARQ: Hybrid Automatic Repeat reQuest) method combining ARQ and an error correction code is defined. For example, as shown in Patent Document 1, a subburst that is data used for HARQ is included in a subburst area in a downlink subframe transmitted from a base station to a communication terminal.

Special Table 2008-527839

  Now, at least one slot composed of one subchannel and at least one symbol is reserved in the downlink subframe, so that the subburst area is arranged in the downlink subframe. Conventionally, the procedure for securing slots in the HARQ subburst area is performed by securing a plurality of slots along the direction in which the subchannel number increases. Therefore, the HARQ subburst region is arranged across many subchannels in the downlink subframe.

  On the other hand, the magnitude of frequency selective fading that deteriorates communication quality generally differs for each subchannel. Therefore, when one HARQ subburst region is arranged across many subchannels, the magnitude of frequency selective fading in one HARQ subburst region varies. As a result, there has been a problem that processing for correcting frequency selective fading, for example, gain adjustment processing becomes complicated.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of suppressing the HARQ subburst region from being arranged across a plurality of subchannels.

  In order to solve the above problems, a base station according to the present invention is a base station for WiMAX (Worldwide Interoperability for Microwave Access), and transmits a signal to a communication terminal and a signal from the communication terminal. Allocating to at least one communication terminal in the predetermined area, a first arrangement section that arranges a predetermined area for subburst in a downlink subframe transmitted from the transmission section to the communication terminal from the transmission section A second arrangement unit that arranges at least one sub-burst area for HARQ (Hybrid Automatic Repeat reQuest), and the second arrangement unit sequentially arranges a plurality of sub-burst slots in the predetermined area. By substituting the subburst area in the predetermined area, the subburst area is reserved in the predetermined area. Continue to ensure along.

  According to an aspect of the base station of the present invention, the transmitter and the receiver share an adaptive array, and the weight for calculating the weight of the adaptive array based on a sounding signal received by the receiver A calculation unit; and an estimation unit configured to estimate a phase rotation amount of a pilot signal received by the reception unit, wherein the transmission unit transmits a signal from the adaptive array based on the weight, and When arranging the subburst area in the downlink subframe, the arranging unit sets the phase rotation amount for all symbols included in all the slots secured in the symbol direction from the first reserved slot to a predetermined value. Slots in the first column are secured along the symbol direction until the threshold value is below the threshold value and approaches the threshold value.

  Also, according to one aspect of the base station according to the present invention, the second arrangement unit has the same symbols as all symbols included in all slots in the first column when securing the second column and subsequent slots. Slots in the symbol are secured in order.

  Further, according to an aspect of the base station according to the present invention, the estimation unit that estimates communication quality on subcarriers in the predetermined region based on a pilot signal received by the reception unit, and the estimation unit A determination unit that determines whether or not the estimated communication quality satisfies a predetermined criterion, and the second arrangement unit includes a second unit that exceeds a predetermined amount of data in the at least one sub-burst region. The first sub-burst area including one sub-burst is determined so that the first sub-burst area includes good sub-carriers that are sub-carriers determined by the determination unit to satisfy communication criteria. It arrange | positions in the said predetermined area | region.

  Also, according to an aspect of the base station according to the present invention, the second arrangement unit includes a second sub-burst including a second sub-burst of a predetermined data amount or less in the at least one sub-burst region. A sub-burst area is arranged in the predetermined area adjacent to the first sub-burst area.

  Also, according to an aspect of the base station according to the present invention, the second arrangement unit includes a second sub-burst including a second sub-burst of a predetermined data amount or less in the at least one sub-burst region. A subburst region is arranged in the predetermined region so as to include the good subcarrier.

  Further, the subburst area allocation method in the base station according to the present invention includes (a) a step of arranging a predetermined area for subburst in a downlink subframe transmitted to a communication terminal; A step of arranging at least one sub-burst region for HARQ (Hybrid Automatic Repeat reQuest) allocated to at least one communication terminal in the predetermined region, and in the step (b), sub-burst in the predetermined region By substituting a plurality of burst slots in order, a sub-burst area is arranged in the predetermined area, and at least the first slot and the next slot are reserved along the symbol direction. It will be done.

  The subburst area allocation method in the base station according to the present invention includes: (c) a step of receiving a sounding signal from a communication terminal by an adaptive array; and (d) the sounding received in step (c). A step of calculating a weight of the adaptive array based on a signal; (e) a step of transmitting a signal from the adaptive array to a communication terminal based on the weight calculated in the step (d); and (f) communication. Receiving a pilot signal from a terminal by the adaptive array; and (g) estimating a phase rotation amount of the pilot signal received in the step (f). In the step (b), The amount of phase rotation in all symbols included in all slots reserved along the symbol direction from the slot reserved in Or less and up closest to the threshold, the first column of the slot along the symbol direction is gradually ensured.

  Further, the subburst region allocation method in the base station according to the present invention is based on (c) receiving a pilot signal from a communication terminal, and (d) based on the pilot signal received in the step (c). And (e) determining whether or not the communication quality estimated in the step (d) satisfies a predetermined standard. In the step (b), a first sub-burst area including a sub-burst exceeding a predetermined data amount out of the at least one sub-burst area has a communication quality predetermined in the step (e). The first subburst region is arranged in the predetermined region so as to include good subcarriers that are subcarriers determined to satisfy the criterion.

  According to the present invention, when a sub-burst area for HARQ is arranged in a predetermined area, at least the first and next slots are secured along the symbol direction. Therefore, it is possible to suppress the HARQ sub-burst region from being arranged across many sub-channels. As a result, since it is possible to prevent the frequency selective fading from being varied in the sub-burst region, it is possible to simplify the process of correcting it.

  In addition, according to one aspect of the present invention, the amount of phase rotation in all symbols included in all slots reserved from the first reserved slot along the symbol direction is equal to or less than a predetermined threshold value. Slots in the first row are secured along the symbol direction to the nearest threshold. Therefore, it is possible to reliably transmit the subburst toward the communication terminal.

  Further, according to one aspect of the present invention, the first subburst region in which the first subburst exceeding the predetermined data amount is included is arranged in the good subcarrier. Thereby, the error data amount of the first sub-burst having a large data amount can be reduced.

  Further, according to one aspect of the present invention, the second subburst area including the second subburst having a predetermined data amount or less is included in the first subburst area arranged so as to include the good subcarrier. Adjacent to each other and placed in a predetermined area. Thereby, the error data amount of the second sub-burst can be reduced.

  In addition, according to one aspect of the present invention, the second subburst area in which the second subburst having a predetermined data amount or less is included is arranged in the predetermined area so as to include good subcarriers. Thereby, the error data amount of the second sub-burst can be reduced.

  FIG. 1 is a diagram showing a configuration of a radio communication system according to an embodiment of the present invention. The wireless communication system includes a base station 1 and a plurality of communication terminals 2. For the sake of simplicity, FIG. 1 shows one terminal among a plurality of communication terminals 2. The base station 1 according to the present embodiment is a base station 1 that is compliant with mobile WiMAX defined in IEEE 802.16e.

  As shown in the figure, the base station 1 includes an adaptive array 3, a transmission unit 4, a reception unit 5, and a control unit 6. The transmission unit 4 and the reception unit 5 share an adaptive array 3 including a plurality of antenna elements 3a. That is, the adaptive array 3 functions as a transmission antenna that transmits a radio signal to the communication terminal 2 and a reception antenna that receives a radio signal from the communication terminal 2. The receiving unit 5 performs amplification processing and down-conversion processing on each of the signals received by the plurality of antenna elements 3 a of the adaptive array 3, and outputs the processed signals to the control unit 6.

  The control unit 6 outputs a transmission weight and a downlink subframe to the transmission unit 4 as a result of an operation described later. The transmission unit 4 transmits the downlink subframe from the control unit 6 from the adaptive array 3 based on the transmission weight from the control unit 6. This operation will be described later.

  FIG. 2 is a diagram illustrating a configuration of the control unit 6 included in the base station 1 according to the present embodiment, and FIG. 3 is a flowchart illustrating an operation of the control unit 6 included in the base station 1. As shown in FIG. 2, the base station 1 includes, in the control unit 6, a weight calculation unit 10, a demodulation unit 11, a HARQ subburst transmission determination unit 12, a first arrangement unit 13, a pilot signal generator 14, The estimation unit 15, the determination unit 16, the second arrangement unit 17, the third arrangement unit 18, the MAP generator 19, and the frame generation unit 20 are provided.

  Based on the sounding signal received by the receiving unit 5, the weight calculating unit 10 sets the reception weight and the transmission weight of the adaptive array 3 for each subcarrier (carrier wave) used for communication with the communication terminal 2. It calculates for every antenna element 3a. The sounding signal is included in an uplink subframe used in WiMAX.

  Here, the frame according to the present embodiment used in WiMAX will be described with reference to FIG. The frame 41 according to the present embodiment includes a downlink subframe 51 transmitted from the base station 1 to the communication terminal 2, and an uplink subframe 71 transmitted from the communication terminal 2 to the base station 1. Each of the downlink subframe 51 and the uplink subframe 71 is represented in two dimensions, a time axis given by an OFDM symbol (unit time) and a frequency axis given by a subchannel. A subchannel is composed of a plurality of subcarriers. Hereinafter, a time axis direction given by a symbol is sometimes referred to as a symbol direction, and a frequency axis direction given by a subchannel is sometimes called a subchannel direction.

  In the upstream subframe 71, a ranging area 72, a CQICH area 73, an ACK area 74, a sounding zone 75, and an upstream burst area 76 are arranged. The ranging area 72 includes a band request and a signal for performing ranging. The CQICH area 73 includes channel quality information. In the ACK area 74, ACK (ACKnowledgement) indicating that the communication terminal 2 does not request the base station 1 to transmit HARQ, or that the communication terminal 2 requests the base station 1 to transmit HARQ. A NACK (Negative ACKnowledgement) to indicate is included. The sounding zone 75 includes a sounding signal used when the weight calculation unit 10 of the base station 1 calculates the weight of the adaptive array 3. Each of the plurality of upstream burst regions 76 is an region allocated by a UL-MAP message included in a UL (UpLink) -MAP region 55 included in the downstream subframe 51, and is transmitted from one or more communication terminals 2 to a base station The data signal transmitted to 1 is included.

  The UL-MAP message included in the UL-MAP area 55 has a UL-MAP IE (Information Element, IE is the same hereinafter). The UL-MAP IE is information for allocating the uplink burst region 76 in the uplink subframe 71. Specifically, the burst position (symbol position and subchannel position) and allocated resources (number of symbols and number of subchannels). ). Each communication terminal 2 can know which subchannel is to be used at which time (symbol) to transmit data addressed to the base station 1 by analyzing information in the UL-MAP region 55. Other regions included in the downlink subframe 51 will be described later.

  The weight calculation unit 10 outputs the reception weight among the reception weight and the transmission weight calculated based on the sounding signal received by the reception unit 5 to the demodulation unit 11 and transmits the transmission weight. Output to part 4. The subsequent operation of the transmission unit 4 will be described later.

  The demodulation unit 11 according to FIG. 2 performs FFT (Fast Fourier Transform) processing on each of the same number of baseband signals as the number of antenna elements 3 a output from the reception unit 5, and outputs the plurality of baseband signals. For each, a plurality of subcarriers included therein are separately obtained. The demodulation unit 11 sets, for each of the same subcarriers included in the plurality of baseband signals, the corresponding reception weight calculated by the weight calculation unit 10 for each of the same subcarriers. Then, the phase and amplitude of each subcarrier are controlled. In step S1, the demodulator 11 combines the same subcarriers after the weight setting for each same subcarrier included in the plurality of baseband signals. Thereby, the beam of the adaptive array 3 can be directed to the desired wave.

  As a result of demodulation by the demodulator 11, an ACK or NACK included in the ACK area 74 described with reference to FIG. 4 of the signal received by the receiver 5 is acquired. When the ACK is acquired by the demodulation process in the demodulator 11, the HARQ subburst transmission determination unit 12 does not start the operation of transmitting the HARQ subburst to the communication terminal 2 and proceeds to step S12 described later ( Step S2). On the other hand, the HARQ sub-burst transmission determination unit 12 determines that the operation of transmitting the HARQ sub-burst is started when the NACK is acquired by the weight calculation unit 10.

  When the HARQ subburst transmission determining unit 12 determines to start the HARQ subburst transmission operation, the first arranging unit 13 includes the HARQ in the downlink subframe 51 transmitted from the transmitting unit 4 to the communication terminal 2. The HARQ burst area 57, which is a predetermined area for sub-burst, is arranged (step S3).

  Here, using FIG. 4 again, downlink subframe 51 constituting frame 41 according to the present embodiment will be described. In the downlink subframe 51 transmitted from the base station 1 to the communication terminal 2, in addition to the UL-MAP region 55 described above, a preamble region 52, an FCH region 53, a DL (DownLink) -MAP region 54, a downlink burst region 56, In addition, the HARQ burst region 57 arranged by the first arrangement unit 13 is arranged. The preamble area 52 includes a signal necessary for the communication terminal 2 to synchronize with the base station 1. The FCH region 53 includes a DLFP (DownLink Frame Prefix) indicating the length of the DL-MAP region 54, the error correction code scheme used therein, and the number of repetitions of the repetition code, and the like. Each of the plurality of downlink burst areas 56 is an area allocated by a DL-MAP message included in the DL-MAP area 54. Each of the plurality of downlink burst regions 56 includes a data signal transmitted to one communication terminal.

  The DL-MAP message included in the DL-MAP region 54 includes a DL-MAP IE, a HARQ DL-MAP IE, and a HAQR subburst IE. The DL-MAP IE is information for allocating the downlink burst region 56 for each communication device in the downlink subframe 51, specifically, information for specifying a burst position and an allocated resource. The HARQ DL-MAP IE is information for arranging the HARQ burst region 57 in the downlink subframe 51, and is specifically information for specifying the burst position and the allocated resource.

  The HARQ subburst IE is information for arranging the HARQ subburst area 58 in the HARQ burst area 57. The HARQ subburst area 58 includes a plurality of slots 59. The slot 59 refers to one subchannel in which subcarriers are collected on the frequency axis, a unit region consisting of one symbol on the time axis, or one subchannel in which subcarriers are collected on the frequency axis. It is a unit area composed of a plurality of symbols on the axis. The size of one HARQ sub-burst area 58 is determined according to the data amount of the HARQ sub-burst included in itself. Therefore, the number of slots 59 constituting one HARQ subburst area 58 is determined according to the amount of HARQ subburst data included in the HARQ subburst area 58. Since one HARQ sub-burst area 58 is allocated to one communication terminal 2, HARQ sub-burst IEs are included in the DL-MAP area 54 by the number of communication terminals 2. Each communication terminal 2 can know by using which subchannel the data addressed to itself is transmitted from the base station 1 in which time zone by analyzing the information in the DL-MAP area. .

  The operations of the demodulation unit 11, the HARQ subburst transmission determination unit 12, and the first arrangement unit 13 have been described above. On the other hand, as a result of demodulation in the demodulator 11 shown in FIG. 2, the pilot signal included in the signal received by the receiver 5 is compared with the known pilot signal generated by the pilot signal generator 14. Based on the comparison result, the estimation unit 15 estimates frequency selective fading of a pilot signal included in the signal received by the reception unit 5. FIG. 5 is a diagram illustrating an operation in which the estimation unit 15 according to the present embodiment estimates frequency selective fading of the pilot signal 81 included in the signal received by the reception unit 5. FIG. 5A shows a signal received by the receiving unit, and one circle shows one subcarrier. As shown in FIG. 5A, generally, the pilot signal 81 is included in the signal received by the receiving unit 5 at a rate of one for each of a plurality of subcarriers, for example, every four subcarriers. In the example of FIG. 5A, data 82 is included in three subcarriers between pilot signals 81.

  As described above, the pilot signal 81 received by the receiving unit 5 is compared with the known pilot signal 83 generated by the pilot signal generator 14. In the example of FIG. 5 (b), null data 84 is included in three subcarriers between known pilot signals 83. Thus, since the pilot signal 81 is included in the signal received by the receiving unit 5 at a rate of one for each of a plurality of subcarriers, the frequency selective fading estimated based on the pilot signal 81 is performed by a plurality of subcarriers. Only one rate is estimated per carrier. For example, as shown in FIG. 5 (b), according to the pilot signal 81 included at a rate of one for every four subcarriers, as shown in FIG. One subcarrier is estimated at a rate.

Next, the estimation unit 15 according to the present embodiment performs frequency selective fading between the two subcarriers by performing linear interpolation processing on the frequency selective fading of the two subcarriers estimated previously. presume. For example, as shown in FIG. 5C, when the frequency selective fading H ₁ and H ₅ has been estimated _first , the frequency selective fading H between them is obtained as shown in FIG. 5D. _{2 ~H 4} also estimated.

By using this technique, the estimation unit 15 according to the present embodiment performs communication quality for all subcarriers in the HARQ burst region 57 arranged in the first arrangement unit 13, that is, frequency selective fading H _n. Is estimated (step S4). Here, n is a natural number, and the frequency selective fading estimated by the estimation unit 15 is written as H ₁ , H ₂ , H ₃ ,... In the subchannel direction. In FIG. 6, a state where the frequency selective fading H _n is estimated for all the subcarriers 85 in the HARQ burst region 57 arranged in the first arrangement unit 13 in Step 3 is indicated by a solid line. .

The determination unit 16 determines whether or not the frequency selective fading H _n estimated by the estimation unit 15 satisfies a predetermined criterion (step S5). In the present embodiment, the determination unit 16 determines whether or not the frequency selective fading H _n estimated by the estimation unit 15 is smaller than a predetermined value α, based on the HARQ burst arranged by the first arrangement unit 13. All the subcarriers 85 in the region 57 are determined. The predetermined value α used for the determination is set by the user of the base station 1, for example. As a result of the determination in the determination unit 16, a subcarrier corresponding to a small frequency selective fading H _n than a predetermined value alpha (hereinafter, sometimes, referred to as the good subcarriers) 86 is detected. In FIG. 7, only the good subcarrier 86 is indicated by a solid line as a result of the determination by the determination unit 16.

  The estimation unit 15 estimates the amount of phase rotation of the pilot signal 81 received by the reception unit 5 (step S6). The estimation unit 15 according to the present embodiment estimates the phase rotation amount θ of the pilot signal 81 in the good subcarrier 86 detected in step S5 among the pilot signals 81 received by the reception unit 5. As described with reference to FIG. 5, pilot signal 81 is generally included in the signal received by receiving unit 5 at a rate of one for each of a plurality of subcarriers. Therefore, the good subcarrier 86 does not necessarily include the pilot signal 81. Therefore, when the good subcarrier 86 does not include the pilot signal 81, the estimation unit 15 according to the present embodiment applies to each of the two subcarriers closest to the good subcarrier 86, as in FIG. The amount of phase rotation of the included pilot signal 81 is linearly interpolated to estimate the amount of phase rotation θ of the good subcarrier 86.

  After step S6, the second arrangement unit 17 determines the position of the HARQ subburst area 58 in which the first HARQ subburst area 58a in which the first HARQ subburst exceeding the predetermined data amount X is included is arranged. Determine (step S7). In the present embodiment, the second arrangement section includes the good subcarrier 86 in which the first HARQ subburst region 58a is determined by the determination section 16 to have the frequency selective fading smaller than the predetermined value α. The arrangement position of the first HARQ sub-burst area 58a is determined. Note that, in the HARQ subburst area 58, the arrangement position of the second HARQ subburst area 58b in which the second HARQ subburst having a predetermined data amount X or less is included is determined in step S9 described later.

  FIG. 8 is a diagram when the second placement unit 17 places the first HARQ subburst region 58a on the good subcarrier 86 detected in step S5 in step S8 described later. In this figure, a case where the first HARQ subburst exceeding a predetermined data amount X is assigned to # 1, 3, and 5 of the communication terminal 2 is shown.

  After step S7, the second arrangement unit 17 arranges at least one first HARQ subburst region 58a in the HARQ burst region 57 according to the number of communication terminals 2 that should receive the HARQ subburst. Start (step S8). The second arrangement unit 17 arranges the HARQ subburst area 58 in the HARQ burst area 57 by sequentially securing a plurality of HARQ subburst slots 59 in the HARQ burst area 57 in the downlink subframe 51. .

  Here, before explaining the slot securing procedure by the second arrangement unit 17 in the present embodiment, the conventional slot securing procedure will be described with reference to FIG. In the conventional slot securing procedure, the slot 59 is secured in the order of FIGS. Hereinafter, in order to distinguish the slots reserved in the HARQ burst area 57, the first slot 59a, the second slot 59b,... May be written in the order reserved in the HARQ burst area 57.

  As shown in FIGS. 9A and 9B, in the conventional slot securing procedure, the first slot 59a secured first and the second slot 59b secured next are in the subchannel direction. Had secured along. The second slot 59b and the third slot 59c secured next are normally secured along the sub-channel direction as shown in FIG. 9C. As a result, since one HARQ subburst region 58 is arranged across many subchannels, the magnitude of frequency selective fading in one HARQ subburst region 58 varies, and the correction process is complicated. There was a problem of becoming.

  A procedure for securing the slot of the second arrangement unit 17 according to the present embodiment to solve the problem will be described with reference to FIG. The slot securing procedure for arranging the first HARQ subburst area 58a and the slot securing procedure for arranging the second HARQ subburst area 58b are substantially the same. Therefore, when the first HARQ subburst area 58a and the second HARQ subburst area 58b are not distinguished, the slot securing procedure will be described below as the HARQ subburst area 58.

  The second placement unit 17 according to the present embodiment secures the slot 59 in the order of FIGS. As shown in FIGS. 10A and 10B, the second arrangement unit 17 according to the present embodiment has at least a first slot 59a and a second slot 59b reserved in the HARQ burst region 57. Will be secured along the symbol direction. Thereby, it can suppress that the HARQ subburst area | region 58 is arrange | positioned ranging over several subchannels. Note that the second arrangement unit 17 according to the present embodiment is arranged so that the first slot 59a included in the first HARQ subburst region 58a includes the good subcarrier 86 detected in FIG. One HARQ sub-burst area 58 a is arranged in the HARQ burst area 57.

  Next, an operation in which the second placement unit 17 according to the present embodiment secures the third and subsequent slots 59 will be described with reference to FIG. In the second arrangement unit 17 according to the present embodiment, the amount of phase rotation in all symbols included in all slots secured along the symbol direction from the first slot 59a secured first is a predetermined threshold value. Slots in the first column are secured along the symbol direction until β is less than or equal to the threshold value β. Here, the slot in the first column means a plurality of slots 59 secured along the symbol direction from the first slot 59a.

In order to perform this operation, the second arrangement unit 17 uses the phase rotation amount θ estimated by the estimation unit 15 in step S6. On the other hand, as shown in FIG. 11A, generally, the pilot signal 81 is received by the receiving unit 5 only at a rate of one for each of a plurality of symbols (hereinafter referred to as N symbols) in the symbol direction. Included in the processed signal. FIG. 11A shows a case where N = 3. Thus, since the pilot signal 81 is included in the signal received by the receiving unit 5 at a rate of one for every N symbols, the estimating unit 15 estimates the total phase rotation amount θ between the N symbols. . For example, in the case of N = 3 shown in FIG. 11A, the estimation unit 15 calculates the total amount of phase rotation for three symbols every three symbols, as shown in FIG. presume. Hereinafter, the phase rotation amount θ estimated by the estimation unit 15 is described as θ ₁ , θ ₂ , θ ₃ ,... In the symbol direction.

Next, the second arrangement unit 17 calculates the amount of phase rotation per symbol. In this embodiment, the phase rotation amount per symbol is a value obtained by dividing the phase rotation amount corresponding to the N symbols including the symbol by N, that is, θ ₁ / N, θ ₂ / N, θ 3 / N, ... is calculated. For example, in the example of FIG. 11 (b), as shown in FIG. _{11 (c), θ 1/} 3 as the phase rotation amount per symbol of the first three symbols, the phase per symbol of the next three symbols as the rotation amount θ _2/3 ..., it is calculated.

  Next, every time the second placement unit 17 secures the slot 59, the total phase rotation amount in all symbols included in all the slots 59 secured so far along the symbol direction is set to a predetermined threshold value. It is determined whether or not β is exceeded.

In FIG. 10B, the second slot 59b is secured along the symbol direction from the first slot 59a secured first. In response to this state, the second placement unit 17 makes two slots 59a and 59b secured from the first slot 59a secured first along the symbol direction so as to be adjacent to the two slots in the symbol direction. It is determined whether the total phase rotation amount of the symbols included in the new third slot 59c to be secured exceeds a predetermined threshold value β. For example, in the case of FIG. 11D, two symbols are included in one slot. Therefore, the symbols included in the three slots are 6 symbols. The second arrangement section 17, as the phase rotation amount of 6 symbols described above, the total amount of phase rotation per one symbol of the 6 symbols obtained in FIG. 11 (c), the _{words, θ 1/3 + θ 1} /3 + θ 1 _{/ 3 + θ 2/3 +} θ 2/3 + θ 2/3 = θ 1 + θ 2 is used.

The second arrangement unit 17 determines whether the total amount of phase rotation of 6 symbols, that is, θ ₁ + θ ₂ exceeds a predetermined threshold value β. In the case of FIGS. 11C and 11D, θ1 + θ2 does not exceed the predetermined threshold value β. In such a case, the second placement unit 17 secures the third slot 59c adjacent to the second slot 59b in the symbol direction.

Next, the second arrangement unit 17 includes three slots 59a, 59b, and 59c that have been secured from the first slot 59a that has been secured to the first along the symbol direction, and is adjacent to the three slots in the symbol direction. It is determined whether the total amount of phase rotation in the symbols included in the new fourth slot 59d to be secured exceeds a predetermined threshold value β. For example, in the case of FIG. 11D, the number of symbols included in one slot is two symbols. Therefore, the symbols included in the four slots are 8 symbols. The second arrangement section 17, as the phase rotation amount of 8 symbols described above, the total amount of phase rotation per one symbol of the 8 symbols obtained in FIG. 11 (c), the _{words, θ 1/3 + θ 1} /3 + θ 1 _{/ 3 + θ 2/3 +} θ 2/3 + θ 2/3 + θ 3/3 + θ 3/3 = θ 1 + θ 2 +2 · θ 3/3 is used.

The second arrangement section 17 determines whether the amount of phase rotation of 8 symbols total, that is, the _{θ 1 + θ 2 +2 · θ} 3/3, exceeds a predetermined threshold value beta. FIG. 11 (c), the case of (d), θ1 + θ2 + 2 · θ 3/3 is greater than a predetermined threshold value beta. In such a case, as shown in FIG. 10D, the second arrangement unit 17 changes the new fourth slot 59d in the subchannel adjacent to the subchannels included in the three slots 59a to 59c. The same symbols as the above six symbols are secured. In the present embodiment, as shown in the figure, the second placement unit 17 secures the fourth slot 59d adjacent to the first slot 59 in the subchannel direction.

  Thus, the second placement unit 17 according to the present embodiment has a predetermined amount of phase rotation in all symbols included in all slots secured along the symbol direction from the first slot 59a secured first. Slots in the first column are secured along the symbol direction until the threshold value β is equal to or less than the threshold value β. Although not shown, the second placement unit 17 according to the present embodiment secures the fifth slot adjacent to each other in the symbol direction on the right side of the fourth slot 59d, and the sixth slot, It is secured adjacent to each other in the symbol direction on the right side of the fifth slot. Thereby, the second placement unit 17 according to the present embodiment always places the rectangular HARQ sub-burst region 58.

  In addition, when the second arrangement unit 17 according to the present embodiment secures the second and subsequent rows of slots, it sequentially secures slots within the same symbols as all symbols included in all slots of the first row. I will do it. As a result, the second placement unit 17 places the first HARQ sub-burst region 58a in the HARQ burst region 57 as shown in FIG.

  In addition, the second arrangement unit 17 according to the present embodiment is arranged so that the first slot 59a included in the first HARQ subburst region 58a includes the good subcarrier 86 detected in FIG. One HARQ sub-burst area 58 a is arranged in the HARQ burst area 57. Therefore, as shown in FIG. 8, the first row slot included in the first HARQ subburst area 58a arranged by the second arrangement unit 17 according to the present embodiment is the good one detected in FIG. Subcarrier 86 is included.

  After step S8, the second arrangement unit 17 determines the arrangement position of the second HARQ subburst area 58b in which the second HARQ subburst having a predetermined data amount or less is included in the HARQ subburst area 58. (Step S9). Similarly to step S8, the second arrangement unit 17 sets at least one second HARQ subburst region 58b in the HARQ burst region 57 according to the number of communication terminals 2 that should receive the HARQ subburst. Arrangement is started (step S10).

  FIG. 12 is a diagram when the second placement unit 17 places the second HARQ sub-burst region 58b in the HARQ burst region 57 according to FIG. 8 in step S10. Here, a case is shown in which the second HARQ sub-burst having a predetermined data amount X or less is assigned to # 2, 4, 6 of communication terminal 2.

  In FIG. 12, the second arrangement unit 17 replaces the second HARQ subburst area 58b assigned to # 2 of the communication terminal 2 with the first HARQ subburst area 58a assigned to # 1 of the communication terminal 2. The HARQ burst regions 57 are arranged adjacent to each other in the direction. At this time, the second arrangement unit 17 includes the second HARQ subburst area 58b allocated to # 4 of the communication terminal 2 in the first HARQ subburst area 58a allocated to # 1 of the communication terminal 2. The HARQ burst region 57 is arranged so as to include the good subcarrier 86. Also, the second arrangement unit 17 assigns the second HARQ subburst area 58b assigned to # 6 of the communication terminal 2 to the first HARQ subburst area 58a assigned to # 1 of the communication terminal 2 and the subchannel direction. Adjacent to the HARQ burst region 57.

  After the HARQ sub-burst regions 58 corresponding to all the communication terminals 2 are arranged in the HARQ burst region 57 by steps S7 to S10, the third arrangement unit 18 includes the downlink burst region in the downlink sub-frame 51. 56 is determined, and the upstream burst area 76 in the upstream subframe 71 is determined (step S11). In addition, when it is determined in step S2 that the HARQ sub-burst transmission determination unit 12 has acquired ACK, the third arrangement unit 18 similarly arranges the downlink burst region 56 in the downlink sub-frame 51, and the uplink An upstream burst area 76 in the subframe 71 is determined.

  After step S11, the MAP generator 19 generates a HARQ DL-MAP IE based on the arrangement of the HARQ burst region 57 in the downlink subframe 51 in step S3 (step S12). In step S3, information specifying the HARQ burst region 57 arranged by the first arrangement unit 13 is input from the first arrangement unit 13 to the MAP generator 19, but is omitted in FIG. .

  Further, the MAP generator 19 generates a HARQ subburst IE based on the arrangement of the HARQ subburst region 58 in the HARQ burst region 57 in steps S7 to S10. Further, the MAP generator 19 generates a DL-MAP IE based on the arrangement of the downlink burst region 56 in the downlink subframe 51 in step S11. Thus, the MAP generator 19 generates a DL-MAP message including the DL-MAP IE, the HARQ DL-MAP IE, and the HAQR sub-burst IE.

  Further, the MAP generator 19 generates a UL-MAP IE based on the determination of the upstream burst region 76 in the upstream subframe 71 in step S11. In this way, the MAP generator 19 generates a UL-MAP message including the UL-MAP IE.

  After step S12, the frame generation unit 20 generates the downlink subframe 51 by including the HARQ subburst in the HARQ subburst region 58 and including the data to be transmitted to the communication terminal 2 for each downlink burst region 56. (Step S13).

  Thus, the operation of the control unit 6 included in the base station 1 is completed. As a result of the operation in the control unit 6, the transmission weight calculated by the weight calculation unit 10 and the downlink subframe 51 generated by the frame generation unit 20 are output to the transmission unit 4 as shown in FIG. Is done. The transmission unit 4 sets, for each of the same subcarriers included in the plurality of subcarrier groups, a corresponding transmission weight calculated by the weight calculation unit 10 for each of the same subcarriers. Then, for each of the plurality of subcarrier groups, the transmission unit 4 generates a baseband signal by combining the plurality of subcarriers after weight setting included in the subcarrier group. The transmission unit 4 performs up-conversion processing and amplification processing on the generated baseband signal, and then inputs the signals subjected to the correction processing to the plurality of antenna elements 3a.

  Thus, the transmission unit 4 transmits the downlink subframe 51 generated by the frame generation unit 20 from the adaptive array 3 based on the transmission weight calculated by the weight calculation unit 10. Thereby, a radio signal is transmitted from the adaptive array 3 toward the communication terminal 2 to be communicated.

  According to the base station 1 as described above, when the HARQ sub-burst region 58 is arranged in the HARQ burst region 57, at least the first slot 59a and the second slot 59b are arranged along the symbol direction. Secure it. Thereby, it can suppress that the HARQ subburst area | region 58 is arrange | positioned ranging over many subchannels. As a result, the process of correcting frequency selective fading can be simplified.

  Generally, when the movement amount of the communication terminal 2 increases, the phase rotation amount θ also increases. Then, when the phase rotation amount θ increases, the directivity of the adaptive array 3 deteriorates at the position of the communication terminal 2 at the timing when the base station 1 tries to transmit. On the other hand, according to base station 1 according to the present embodiment, the amount of phase rotation in all symbols included in all slots 59 secured from the first slot 59a secured first up to that point in the symbol direction. Slots 59 in the first column are secured along the symbol direction until θ is equal to or less than a predetermined threshold value β and closest to the threshold value β. Therefore, the HARQ subburst can be reliably transmitted toward the communication terminal 2.

  Also, base station 1 according to the present embodiment reserves the second row of slots in the same symbol as the six symbols in the subchannel adjacent to the subchannel included in the first row of slots. In general, sub-channels adjacent to each other have no significant difference in the amount of phase rotation corresponding to each sub-channel. Therefore, as for the slot in the second row, as in the case of the slot in the first row, it is not necessary to detect the phase rotation amount θ or compare the total phase rotation amount with the predetermined threshold value β. The communication terminal 2 can almost receive the second row of slots.

  In general, when data having a large amount of data is arranged on a subcarrier having a large influence of frequency selective fading, the amount of error data becomes large compared to data having a small amount of data. On the other hand, the base station 1 according to the present embodiment uses the first HARQ subburst region 58a in which the first HARQ subburst exceeding the predetermined data amount X is included in the frequency selective fading more than the predetermined α. It arrange | positions to the favorable subcarrier 86 determined to be small. Thereby, it is possible to reduce the error data amount of the first HARQ sub-burst having a large data amount that tends to have a large error data amount.

  Further, the base station 1 according to the present embodiment includes the HARQ burst region so that the second HARQ subburst region 58b including the second HARQ subburst having a predetermined data amount X or less is included in the good subcarrier 86. 57. Thereby, it is possible to reduce the error data amount of the second HARQ sub-burst having a small data amount that tends to have a small error data amount.

  In addition, the base station 1 according to the present embodiment has at least the second HARQ subburst region 58b in which the second HARQ subburst having a predetermined data amount X or less is included adjacent to at least the first HARQ subburst region 58a. And arranged in the HARQ burst region 57. As a result, the second HARQ sub-burst with a small amount of data is arranged in the HARQ burst region 57 so as to include the good sub-carrier 86 or arranged in a sub-carrier having frequency selective fading close to the good sub-carrier 86. Is done. Therefore, the error data amount of the second HARQ sub-burst with a small data amount can be reduced to some extent.

  In the present embodiment, the second placement unit 17 secures the fourth slot 59 adjacent to the first slot 59 and provides the fifth slot 59 and the sixth slot 59 as the fourth slot. The slot 59 is secured to the right along the symbol direction. However, the present invention is not limited to this, and the second arrangement unit 17 according to the present embodiment secures the fourth slot 59 adjacent to the third slot 59 and secures the fifth slots 59, 6. The second slot 59 may be secured by securing the fourth slot 59 to the left along the symbol direction from the fourth slot 59.

  Further, in the above description, the second arrangement unit 17 defines the first HARQ subburst region 58 as the HARQ burst region so that the slot 59 in the first column of the HARQ subburst region 58 includes the good subcarrier 86. 57. However, the second arrangement unit 17 according to the present embodiment is not limited to this, and the first HARQ subburst region 58 is set so that the slots 59 other than the first column include the good subcarrier 86. May be arranged in the HARQ burst region 57.

  In the above description, the first arrangement unit 13 arranges the HARQ burst region 57 in which the HARQ subburst region 58 is arranged in the slot securing procedure according to FIG. 9 in one downlink subframe 51. However, the first arrangement unit 13 according to the present embodiment is not limited to this, and the HARQ burst region in which the HARQ sub-burst region 58 is arranged in the slot securing procedure according to the present embodiment according to FIG. 57 and the HARQ burst region 57 in which the HARQ sub-burst region 58 is arranged in the conventional slot securing procedure according to FIG. 8 may be arranged side by side in one downlink subframe 51.

It is a block diagram which shows the structure of the radio | wireless communications system which concerns on embodiment. It is a block diagram which shows the structure of the control part with which the base station which concerns on embodiment is provided. It is a flowchart which shows operation | movement of the control part with which the base station which concerns on embodiment is provided. It is a figure which shows the example of a frame structure in mobile WiMAX. It is a figure which shows operation | movement of the control part with which the base station which concerns on embodiment is provided. It is a figure which shows operation | movement of the control part with which the base station which concerns on embodiment is provided. It is a figure which shows operation | movement of the control part with which the base station which concerns on embodiment is provided. It is a figure which shows operation | movement of the control part with which the base station which concerns on embodiment is provided. It is a figure which shows the conventional slot ensuring operation | movement. It is a figure which shows the slot ensuring operation | movement which concerns on embodiment. It is a figure which shows operation | movement of the control part with which the base station which concerns on embodiment is provided. It is a figure which shows operation | movement of the control part with which the base station which concerns on embodiment is provided.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base station 2 Communication terminal 3 Adaptive array 4 Transmission part 5 Reception part 6 Control part 11 Weight calculation part 13 1st arrangement part 15 Estimation part 16 Judgment part 17 2nd arrangement part 51 Downlink subframe 57 HARQ burst area 58 HARQ Sub-burst area 58a First HARQ sub-burst area 58b Second HARQ sub-burst area 59 slots

Claims (9)

WiMAX (Worldwide Interoperability for Microwave Access) base station,
A transmission unit for transmitting a signal to the communication terminal;
A receiving unit for receiving a signal from a communication terminal;
A first arrangement unit that arranges a predetermined region for subburst in a downlink subframe transmitted from the transmission unit to the communication terminal;
A second arrangement unit that arranges at least one sub-burst area for HARQ (Hybrid Automatic Repeat reQuest) allocated to at least one communication terminal in the predetermined area;
The second arrangement part is:
A sub-burst area is arranged in the predetermined area by sequentially securing a plurality of slots for sub-burst in the predetermined area,
A base station that secures at least the first and next slots reserved in the predetermined area along the symbol direction. The base station according to claim 1, wherein
The transmitter and the receiver share an adaptive array,
A weight calculating unit that calculates a weight of the adaptive array based on a sounding signal received by the receiving unit;
An estimation unit that estimates a phase rotation amount of a pilot signal received by the reception unit;
The transmission unit transmits a signal from the adaptive array based on the weight,
The second arrangement part is:
When placing the subburst region in the downlink subframe,
Along the symbol direction until the amount of phase rotation in all symbols included in all slots secured along the symbol direction from the first secured slot is less than or equal to a predetermined threshold and approaches the threshold. A base station that secures slots in the first row. The base station according to claim 2, wherein
The second arrangement part is:
When securing slots for the second and subsequent rows,
A base station that sequentially secures slots in the same symbols as all symbols included in all slots in the first row. The base station according to claim 1, wherein
An estimation unit for estimating communication quality on subcarriers in the predetermined region based on a pilot signal received by the reception unit;
A determination unit that determines whether or not the communication quality estimated by the estimation unit satisfies a predetermined standard;
The second arrangement unit includes a first sub-burst region that includes a first sub-burst that exceeds a predetermined amount of data among the at least one sub-burst region, and the determination unit has a communication quality of a predetermined reference The base station arranges the first subburst area in the predetermined area so as to include good subcarriers that are subcarriers determined to satisfy The base station according to claim 4, wherein
The second arrangement unit makes a second sub-burst area including a second sub-burst having a predetermined data amount or less included in the at least one sub-burst area adjacent to the first sub-burst area. A base station arranged in the predetermined area. The base station according to claim 4, wherein
The second arrangement unit includes the predetermined sub-burst region in which the second sub-burst region including a second sub-burst having a predetermined data amount or less is included in the at least one sub-burst region so as to include the good sub-carrier. A base station located in the area. WiMAX (Worldwide Interoperability for Microwave Access) base station subburst area allocation method,
(A) a step of arranging a predetermined region for subburst in a downlink subframe transmitted to a communication terminal;
(B) In the predetermined area, at least one sub-burst area for HARQ (Hybrid Automatic Repeat reQuest) allocated to at least one communication terminal is disposed,
In the step (b),
A plurality of slots for subburst are secured in order in the predetermined area, so that the subburst area is arranged in the predetermined area,
A method of arranging sub-burst areas in a base station, which is reserved along the symbol direction for at least the first and next slots reserved in the predetermined area. A method for arranging sub-burst areas in a base station according to claim 7,
(C) receiving a sounding signal from the communication terminal with an adaptive array;
(D) calculating a weight of the adaptive array based on the sounding signal received in the step (c);
(E) transmitting a signal from the adaptive array to a communication terminal based on the weight calculated in the step (d);
(F) receiving a pilot signal from the communication terminal at the adaptive array;
(G) further comprising estimating a phase rotation amount of the pilot signal received in the step (f),
In the step (b),
In the symbol direction, the phase rotation amount in all symbols included in all the slots reserved along the symbol direction from the first reserved slot is equal to or less than a predetermined threshold value and is closest to the threshold value. A method of arranging sub-burst areas in a base station, in which slots in the first row are secured along the base station. A method for arranging sub-burst areas in a base station according to claim 7,
(C) receiving a pilot signal from a communication terminal;
(D) estimating communication quality on subcarriers in the predetermined region based on the pilot signal received in step (c);
(E) further comprising a step of determining whether or not the communication quality estimated in the step (d) satisfies a predetermined standard,
In the step (b), a communication quality of the first sub-burst region including a sub-burst exceeding a predetermined amount of data among the at least one sub-burst region satisfies a predetermined standard in the step (e). Then, the subburst region allocation method in the base station, in which the first subburst region is disposed in the predetermined region so as to include the good subcarrier that is determined as the subcarrier.

Images