JP5292214B2 - Radio resource allocation device, radio resource allocation method, and radio resource allocation program - Google Patents

Description

  The present invention relates to a radio resource allocation technique in the radio communication technical field.

  In a conventional wireless communication system, for example, a mobile communication system, when a transmission error occurs in a wireless link and a receiving side receives an erroneous packet, an ARQ (Automatic Repeat reQuest) that detects the erroneous packet and makes a retransmission request Is used. In order to further improve the communication quality more efficiently, hybrid ARQ (Hybrid Automatic Repeat reQuest) that can suppress the number of retransmissions by transmitting an error correction code and performing error correction is also used.

  As for this hybrid ARQ, two methods, known as a synchronous hybrid ARQ (hereinafter referred to as synchronous HARQ) and an asynchronous hybrid ARQ (hereinafter referred to as asynchronous HARQ) are known (for example, patents). Reference 1). Among them, the synchronous HARQ is a scheme that performs retransmission at a predetermined transmission timing that is a constant interval, and the asynchronous HARQ is a scheme in which the retransmission timing does not become a constant cycle.

  Further, as a method of radio resource allocation by packet retransmission using synchronous HARQ, a non-adaptive retransmission allocation scheme (non-adaptive retransmission allocation scheme) and an adaptive retransmission allocation scheme (adaptive retransmission allocation scheme) are known. (For example, refer nonpatent literature 1).

  The non-adaptive retransmission allocation scheme is a scheme in which the application condition of the retransmission packet is the same as the application condition at the previous transmission when performing synchronous HARQ. That is, the transmission side does not transmit the control information when transmitting the retransmission packet, and the reception side demodulates the radio packet using the control information received last time. Specifically, in the case of the non-adaptive retransmission allocation method, for example, if a data error occurs during the initial transmission of the data packet, the control information is not transmitted again in the second transmission, but transmitted in the initial transmission. Radio resources are allocated according to the control information (radio resource arrangement, radio resource amount, modulation scheme, channel coding scheme, etc.). The receiving side performs demodulation at a timing determined based on the control information received at the time of initial transmission. Thereby, the radio | wireless resource used for control information can be reduced. This non-adaptive retransmission allocation scheme is effective when used in a state where the radio propagation path is moderate. By reducing control information, the utilization efficiency of radio resources can be improved and the system capacity can be increased. .

  On the other hand, the adaptive retransmission allocation scheme is a scheme in which the application conditions for retransmission packets are different from the application conditions for the previous transmission. In other words, the transmission side transmits control information every time a retransmission packet is transmitted, and the reception side demodulates the radio packet using the newly received control information. The adaptive retransmission allocation scheme is a method for determining the optimal radio resource allocation, modulation scheme, etc. according to the state of the propagation path at the time of retransmission in a state where radio channel variation is severe. The probability that the retransmission data can be correctly demodulated increases, and the system capacity can be increased.

  Further, SPS (Semi-Persistent Scheduling) is known in which radio resources determined semi-statically at fixed intervals are fixedly allocated at the time of initial transmission or retransmission (see Non-Patent Document 1). Originally, when allocating radio resources, it is necessary to notify the terminal of the allocation result through a control channel or the like. However, when SPS is used, the radio resource is fixedly allocated, so it is necessary to transmit the control channel each time. Therefore, the radio resources of the control channel can be used effectively. Therefore, the SPS is effective for an application in which packets periodically arrive and the packet size does not change, for example, VoIP (Voice over Internet Protocol).

JP 2007-300504 A

3GPP TS 36.211, “Evolved Universal Terrestrial Radio Access (E-UTRA) Physical Channels and Modulation”

  However, in a radio communication system using synchronous HARQ, when resource allocation is performed by combining SPS and a non-adaptive retransmission allocation scheme, the radio resource of one terminal reserved at a fixed interval by SPS and the non-adaptive type There may be a collision with the radio resource of the other terminal allocated by the retransmission allocation method. In that case, conventionally, SPS is once canceled and reassigned to another radio resource, or another radio resource is assigned by an adaptive retransmission allocation method. Therefore, in any case, it is necessary to transmit control information again, reducing the system capacity.

Therefore, the present invention has been made in view of the above problems, and in a non-adaptive retransmission allocation system communication system that performs retransmission using synchronous HARQ, the SPS and the non-adaptive retransmission allocation system are efficiently combined. It is an object of the present invention to provide a radio resource allocation device, a radio resource allocation method, and a radio resource allocation program that can allocate radio resources.

In order to solve the above problems, the present invention provides means [1]-[4] below.
[1] In a radio resource allocation apparatus that performs radio resource allocation in a communication system of a non-adaptive retransmission allocation scheme in which a retransmission interval is a fixed period,
Search condition determining means for changing and determining at least one of a search direction and a search start position, which are search conditions for radio resources that can be allocated, for each predetermined period;
Allocating means for searching and allocating radio resources according to the determined search condition;
A radio resource allocation device comprising:
[2] It further comprises input means for inputting a search start position initial value that does not become the same value between adjacent radio base stations or sectors,
The radio resource allocating device according to the above [1], wherein the search condition determining means determines the search start position based on the initial value of the search start position.
[3] In a radio resource allocation method for allocating radio resources in a communication system of a non-adaptive retransmission allocation scheme in which a retransmission interval is a fixed period,
A search condition determining step for changing and determining at least one of a search direction and a search start position, which are search conditions for radio resources that can be allocated, for each predetermined period;
An allocation step of searching and allocating radio resources according to the determined search conditions;
A radio resource allocating method comprising:
[4] A radio resource allocation device that performs allocation of radio resources used in retransmission processing of a fixed period by a non-adaptive retransmission allocation method ,
A search condition determining step for changing and determining at least one of a search direction and a search start position, which are search conditions for radio resources that can be allocated, for each predetermined period;
An allocation step of searching and allocating radio resources according to the determined search conditions;
A radio resource allocation program for executing

Advantageous Effects of Invention According to the present invention, in a non-adaptive retransmission allocation scheme communication system that performs retransmission using synchronous HARQ, radio resources can be allocated by efficiently combining SPS and non-adaptive retransmission allocation scheme.

It is a functional block diagram of the radio | wireless scheduler to which the radio | wireless resource allocation apparatus which is embodiment of this invention is applied. FIG. 2 is a configuration diagram conceptually showing a configuration of radio resources. It is a flowchart about the radio | wireless resource allocation process per radio | wireless frame in a radio | wireless scheduler. It is a flowchart about the search condition determination process in the search condition determination part of a wireless scheduler. 5 is an example of a program model that more specifically represents the search condition determination process shown in FIG. 4. It is a block diagram showing the structure of the radio | wireless resource allocated by this embodiment. It is a figure showing a mode that a resource block is reallocated in the radio | wireless resource allocated by this embodiment. It is a figure showing a mode that the radio | wireless resource is cyclically allocated by this embodiment. It is an example of the block diagram of radio | wireless resource allocation at the time of making another example of search conditions.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 shows a functional configuration diagram of a radio scheduler to which a radio resource allocation device according to an embodiment of the present invention is applied. In the figure, the radio scheduler 1 includes an input information acquisition unit 11, a search condition determination unit 12, an allocation index calculation unit 13, a terminal selection unit 14, a radio resource allocation unit 15, and an allocation result output unit 16. I have.

  The input information acquisition unit 11 acquires various parameters used for radio resource allocation and allocation index calculation information used for calculation of an allocation index of a wireless terminal. The various parameters include, for example, the frame number of the radio frame, the system bandwidth, the search start position initial value, the SPS allocation interval, and the synchronous HARQ retransmission interval. The allocation index calculation information includes, for example, wireless terminal active information (Active / Inactive), wireless terminal performance information (Capability), SINR (Signal-to-Interference and Noise power Ratio), propagation path information, interference information, and arrangement information. Reception power information, GBR (Guaranteed Bit Rate), Delay Budget information, allowable delay information, and the like.

  When the input information acquisition unit 11 acquires the various parameters and the allocation index calculation information, the input information acquisition unit 11 supplies the various parameters to the search condition calculation unit 12 and the radio resource allocation unit 15, and assigns the allocation index calculation information to the allocation index calculation unit 13 and the radio resource. To the allocation unit 15.

  The search condition determination unit 12 has a function of determining a search condition for searching for an assignable resource block based on various parameters. A resource block is a minimum unit constituting a radio resource. Specifically, the search condition determination unit 12 determines a search start resource block for starting a search for an allocatable resource block and a search direction in the frequency direction.

  The allocation index calculation unit 13 calculates allocation indexes for all wireless terminals that request SPS based on the allocation index calculation information. The terminal selection unit 14 sequentially selects a wireless terminal having a higher priority as a wireless terminal having a higher priority as a wireless terminal having a higher allocation index.

  The radio resource allocation unit 15 is selected by the terminal selection unit 14 based on the search start resource block and search direction determined by the search condition determination unit 12 and the allocation index calculation information and various parameters acquired from the input information acquisition unit 11 Allocation of radio resources of radio terminals is performed. The allocation result output unit 16 converts the radio resource allocation result allocated by the radio resource allocation unit 15 into radio resource allocation data in a format that matches the system specifications, and transmits the radio resource allocation data to each unit in the base station that requires the radio resource allocation data. Output.

  FIG. 2 is a configuration diagram conceptually showing the configuration of radio resources. The figure shows a state in which a radio frame RF having a certain time width is allocated within a certain system bandwidth FB. The radio frame RF indicates that the resource block RB having a certain subcarrier frequency is configured as a minimum unit.

  Next, the operation of a radio scheduler to which the radio resource allocation device according to this embodiment is applied will be described. FIG. 3 shows a flowchart of a radio resource allocation process per radio frame in the radio scheduler 1, and the operation will be described with reference to this flowchart. The allocation index calculation unit 13 that has received the allocation index calculation information acquired by the input information acquisition unit 11 calculates the allocation index for all wireless terminals that request SPS based on the allocation index calculation information (S301). ). This allocation index can be calculated according to various criteria, and can be calculated by a known method. For example, based on the SINR included in the allocation index calculation information, calculation is performed so that a radio terminal having a better signal quality has a higher allocation index.

  Next, the search condition determination unit 12 that has received the various parameters acquired by the input information acquisition unit 11 determines the search start resource block in the designated radio frame RF and the search direction in the frequency direction (S302). Specifically, the search condition determination unit 12 determines the time direction in the two-dimensional radio resource of the frequency vs. time component in a maximum of four sectors (first to fourth sectors) in units of time equal to or shorter than the synchronous HARQ retransmission interval. The search start resource block and the search direction are determined for each sector.

  Here, FIG. 4 shows a flowchart of the search condition determination process in the search condition determination unit 12, and FIG. 5 shows an example of a program model that shows the process more specifically, and will be described in more detail. Note that each variable in FIG. 5 includes frame number i (i is an integer of 0 or more), SPS allocation interval Tss, synchronous HARQ retransmission interval Trs, search start position initial value Jss, search start resource block Js (i), system It means the bandwidth FB and the search direction dir. When a specific example is given, in order to simplify the description, SPS allocation interval Tss = 32 frames, synchronous HARQ retransmission interval Trs = 8 frames, system bandwidth FB = 50 blocks, search start position The initial value Jss = 10 blocks.

  When the frame number i is designated by the input information acquisition unit 11, the search condition determination unit 12 determines whether or not the radio frame RF of the frame number i corresponds to the first sector (S401). Specifically, for example, when the remainder obtained by dividing the frame number i by the SPS allocation interval Tss is smaller than the synchronous HARQ retransmission interval Trs, that is, a set of radio frames RF starting from the frame number i = 0 every 32 frames. In this case, it is determined whether or not the first sector among the four sectors obtained by dividing each set by 8 frames.

  If it is determined that the radio frame RF of frame number i is in the first sector (YES in S401), the search start position initial value Jss is set in the search start resource block Js (i) (S402). Then, the search direction dir is set in ascending order up, and the search condition determination process is terminated (S403). Here, ascending order means a direction in which the frequency increases in the frequency direction.

  If it is determined in step S401 that the radio frame RF of frame number i is not in the first sector (NO in S401), the search condition determination unit 12 sets the radio frame RF of frame number i to the second sector. It is determined whether it is applicable (S411). Specifically, for example, when the remainder obtained by dividing the frame number i by the SPS allocation interval Tss is smaller than the synchronous HARQ retransmission interval Trs × 2, that is, the radio frame RF starting from the frame number i = 0 is incremented every 32 frames. In the case of a set, it is determined whether or not it is in the second sector among the four sectors obtained by dividing each set by 8 frames.

  If it is determined that the radio frame RF of frame number i is in the second sector (S411 YES), the search start position initial value Jss-1 is set in the search start resource block Js (i) (S412). Then, the search direction dir is set to descending order down and the search condition determination process is terminated (S413). Here, the descending order means a direction in which the frequency decreases in the frequency direction.

  If it is determined in step S411 that the radio frame RF of frame number i is not in the second sector (NO in S411), the search condition determination unit 12 sets the radio frame RF of frame number i to the third sector. It is determined whether it is applicable (S421). Specifically, for example, when the remainder obtained by dividing the frame number i by the SPS allocation interval Tss is smaller than the synchronous HARQ retransmission interval Trs × 3, that is, the radio frame RF starting from the frame number i = 0 is incremented every 32 frames. In the case of a set, it is determined whether or not it is in the third sector among the four sectors obtained by dividing each set by 8 frames.

  If it is determined that the radio frame RF of frame number i is in the third sector (YES in S421), the search start position obtained by adding a predetermined offset to the search start position initial value Jss-1 is set as the search start resource block Js. Set to (i) (S422). Specifically, the value obtained by dividing the system bandwidth FB by 2 and truncating the decimal point is used as an offset value, and the offset value is added to the search start position initial value Jss-1 within the system bandwidth FB. Is set in the search start resource block Js (i). Then, the search direction dir is set to descending order down and the search condition determination process is terminated (S423).

  If it is determined in step S421 that the radio frame RF of frame number i is not in the third sector (NO in S421), the search condition determination unit 12 sets the radio frame RF of frame number i to the fourth sector. It is determined whether it is applicable (S431). Specifically, for example, when the remainder obtained by dividing the frame number i by the SPS allocation interval Tss is smaller than the synchronous HARQ retransmission interval Trs × 4, that is, the radio frame RF starting from the frame number i = 0 is incremented every 32 frames. In the case of a set, it is determined whether or not it is in the fourth sector among the four sectors obtained by dividing each set by 8 frames.

  When it is determined that the radio frame RF of the frame number i is in the fourth sector (YES in S431), the search start resource block Js (i) is obtained by adding a predetermined offset to the search start position initial value Jss. ) Is set (S432). Specifically, the value obtained by dividing the system bandwidth FB by 2 and truncating the decimal point as an offset value, and adding the offset value to the search start position initial value Jss within the range of the system bandwidth FB Is set in the search start resource block Js (i). Then, the search direction dir is set in ascending order up, and the search condition determination process is terminated (S433).

  Returning to the description of the flowchart of FIG. 3, after the process of step S302, the terminal selection unit 14 prioritizes the wireless terminal with the highest allocation index among the allocation indexes calculated by the allocation index calculation unit 13 in the process of step S301. It is determined that the terminal is a high-frequency wireless terminal (S303).

  Next, the radio resource allocation unit 15 selects the terminal selection unit 14 in the process of step S303 based on the search start resource block Js (i) and the search direction dir determined by the search condition determination unit 12 in the process of step S302. The wireless resource is allocated to the wireless terminal that has been performed (S304). Then, the radio resource allocation unit 15 excludes radio terminals to which radio resources are allocated from allocation candidates (S305).

  Next, the radio resource allocation unit 15 determines whether or not the end condition is satisfied such that there is no radio resource that can be allocated, there is no information to be transmitted to all allocation candidate radio terminals, or there is no radio resource of the control channel. Is determined (S306). If the end condition is not satisfied, the process returns to step S303 (NO in S306), and if the end condition is satisfied, the search condition determining process is ended (YES in S306).

  When the wireless scheduler 1 allocates wireless resources by the above processing, the state becomes as shown in FIG. That is, for the radio frame corresponding to the first sector, the resource block is allocated with the search start position initial value Jss as the resource block allocation start position and the search direction in ascending order. The radio frame corresponding to the second sector is allocated with the search start position initial value Jss-1 as the resource block allocation start position and the search direction in descending order. Also, for the radio frame corresponding to the third sector, the resource block is allocated with the position shifted by a predetermined offset value from the search start position initial value Jss-1 as the resource block allocation start position and the search direction in descending order. . Then, for the radio frame corresponding to the fourth sector, the resource block is allocated with the position shifted from the search start position initial value Jss by a predetermined offset value as the resource block allocation start position and the search direction in ascending order.

  By allocating radio resources in this way, resource block positions that are separated from each resource block position by the synchronous HARQ retransmission interval Trs can be made free. Therefore, when packet retransmission processing occurs, the probability that a packet can be retransmitted using the non-adaptive retransmission allocation scheme can be increased.

  Note that the search start position initial value Jss is preferably set to a different value for each radio base station or each sector (management section) in order to reduce interference from adjacent base stations. For example, in each base station or sector, the search start position initial value Jss may be determined based on a random number or may be determined not to overlap by an operator.

  FIG. 7 shows a diagram showing how resource blocks are reallocated. In the figure, when the resource block RB1a allocated in the first sector cannot be normally received and the packet is to be retransmitted, another resource block is located at a position separated from the location by the synchronous HARQ retransmission interval Trs. Therefore, the resource block RB1b can be reassigned by the non-adaptive retransmission assignment method.

  Also, in the figure, when the resource block RB2a allocated in the third sector cannot be normally received and is retransmitted, another resource block is located at a position separated from the location by the synchronous HARQ retransmission interval Trs. Therefore, the resource block RB2b can be reassigned by the non-adaptive retransmission assignment method.

  In the radio resource allocation process of the radio resource allocation unit 15, as shown in FIG. 8, when searching in ascending order from the search start resource block, search is performed up to the resource block at the upper limit of the system bandwidth FB that is the allocatable bandwidth. Then, the search may be performed cyclically from the lower limit resource block of the system bandwidth FB to the designated search start resource block. Similarly, in descending order, after searching from the search start resource block to the lower limit resource block, the search may be performed cyclically from the upper limit resource block to the designated search start resource block. Thereby, radio | wireless resources can be allocated efficiently.

  However, in order to prevent the resource block from colliding when the resource block allocated in the previous sector cannot be normally received and the packet is retransmitted, the above cyclic search can be prohibited. For example, when a state in which many packet retransmissions occur occurs, whether or not to prohibit is determined according to the relationship between the number of users of wireless terminals and the collision rate due to packet retransmission.

  As described above, according to the radio scheduler to which the radio resource allocation device according to the embodiment of the present invention is applied, the SPS and the non-adaptive retransmission allocation scheme are efficiently used in a system in which retransmission is performed using synchronous HARQ. It is possible to allocate radio resources in combination. As a result, collisions of radio resources are reduced, control channels for transmitting control information can be reduced, and the throughput of the entire radio communication system can be improved. That is, it is possible to increase the number of wireless terminals accommodated by users.

  In the present embodiment, an example has been described in which the search condition determination unit 12 uses both the search start resource block Js (i) and the search direction dir as search conditions. Besides this, for example, as shown in FIG. 9, a method of adjusting only the search direction (FIG. 9A), or a method of adjusting only the search start position while fixing the search direction (FIG. 9B). However, the desired effect can be achieved.

  In the present embodiment, the example in which the search condition determination unit 12 manages a maximum of four sectors has been described. However, the maximum number of sectors is not limited to four. Similarly, when the offset value is obtained, the system bandwidth FB is divided by 2. However, this calculation is only an example, and a desired offset value may be used. Furthermore, in the present embodiment, the designation order of the search direction is ascending order → descending order → descending order → ascending order, but other patterns such as ascending order → descending order → ascending order → descending order may be used.

  In the present embodiment, the search start position and the search direction during the period of the synchronous HARQ retransmission interval Trs are the same. However, the search start position or the search direction may be different for each retransmission interval. Therefore, the search start position or search direction may be changed for each RF.

  Moreover, you may make it implement | achieve the function of a part of radio | wireless resource allocation apparatus which is embodiment mentioned above, for example, a search condition calculation part, and a radio | wireless resource allocation part. In this case, the wireless resource allocation program for realizing the control function is recorded on a computer-readable recording medium, and the wireless resource allocation program recorded on the recording medium is read by the computer system and executed. May be. Here, the “computer system” includes an OS (Operating System) and hardware of peripheral devices. The “computer-readable recording medium” refers to a portable recording medium such as a flexible disk, a magneto-optical disk, an optical disk, and a memory card, and a storage device such as a hard disk built in the computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case may be included and a program that holds a program for a certain period of time may be included. Further, the above program may be for realizing a part of the functions described above, or may be realized by a combination with the program already recorded in the computer system. .

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design etc. of the range which does not deviate from the summary of this invention are included.

DESCRIPTION OF SYMBOLS 1 Radio scheduler 11 Input information acquisition part 12 Search condition determination part 13 Allocation index calculation part 14 Terminal selection part 15 Radio | wireless resource allocation part 16 Allocation result output part

Claims (4)

In a radio resource allocation apparatus that allocates radio resources in a communication system of a non-adaptive retransmission allocation scheme in which a retransmission interval is a fixed period,
Search condition determining means for changing and determining at least one of a search direction and a search start position, which are search conditions for radio resources that can be allocated, for each predetermined period;
Allocating means for searching and allocating radio resources according to the determined search condition;
A radio resource allocation device comprising: It further comprises input means for inputting a search start position initial value that does not become the same value between adjacent radio base stations or sectors,
The radio resource allocation device according to claim 1, wherein the search condition determination unit determines the search start position based on the initial value of the search start position. In a radio resource allocation method for allocating radio resources in a non-adaptive retransmission allocation scheme communication system in which a retransmission interval is a fixed period,
A search condition determining step for changing and determining at least one of a search direction and a search start position, which are search conditions for radio resources that can be allocated, for each predetermined period;
An allocation step of searching and allocating radio resources according to the determined search conditions;
A radio resource allocating method comprising: To a radio resource allocating apparatus that performs non-adaptive retransmission allocation scheme to allocate radio resources used in a fixed-cycle retransmission process,
A search condition determining step for changing and determining at least one of a search direction and a search start position, which are search conditions for radio resources that can be allocated, for each predetermined period;
An allocation step of searching and allocating radio resources according to the determined search conditions;
A radio resource allocation program for executing

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