JP7434068B2 - Wireless communication system, communication method, and wireless base station - Google Patents

Description

TECHNICAL FIELD This disclosure relates to radio resource allocation for wireless communication systems.

In a wireless communication system, allocation control of wireless resources is performed for each wireless terminal in order to avoid data collision in communication between one wireless base station and a plurality of wireless terminals. For example, the mobile wireless communication standard LTE (Long Term Evolution) and the wireless LAN (Local Area Network) IEEE 802.11ax use OFDMA (Orthogonal Frequency Division Multiple Access). ) has been adopted, and the amount of radio resources is divided into RB (Resource Block). It is assigned to each wireless terminal in units of RU (Resource Unit). The relationship between RB/RU and data rate depends on MCS (Modulation and Coding Scheme) and the number of tones (number of subcarriers).

For RB allocation in LTE, technologies have been proposed that take into account the buffer status of each user and allocate radio resources in proportion to the amount of data addressed to each user, as well as those that take into account communication quality and fairness among users. (For example, see Non-Patent Documents 1 to 4.)

F. Capozzi, “Downlink Packet Scheduling in LTE Cellular Networks: Key Design Issues and a Survey,” IEEE Communications Surv. eys & Tutorials, vol. 15, no. 2, pp. 678-700, Second Quarter 2013. E. Khorov et al. , “A Tutorial on IEEE 802.11ax High Efficiency WLANs,” IEEE Communications Surveys & Tutorials, vol. 21, no. 1, pp. 197-216, First Quarter 2019. G. Piro et al. , “Two-Level Downlink Scheduling for Real-Time Multimedia Services in LTE Networks,” IEEE Transactions on Multimedia, vol. 13, no. 5, pp. 1052-1065, Oct. 2011. Yamashita et al., “Wireless QoS Control Technology,” NTT Technology Journal, Vol. 16, No. 7, pp. 23-28, July 2004.

However, as the number of wireless terminals increases due to the spread of IoT (Internet of Things) and the concentration of access during disasters, OFDMA of the IEEE 802.11ax standard requires efficient wireless resources in real time due to various quality requirements and quality fluctuations. There was a problem that allocation became difficult.

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a wireless communication system, a communication method, and a wireless communication system that can allocate wireless resources while ensuring efficiency and fairness among users by considering the communication quality of each wireless terminal in real time. and wireless base stations.

In order to achieve the above object, the radio communication system according to the present invention determines the radio resource allocation amount between the radio base station and each radio terminal through feedback control, taking into consideration communication quality and buffer status.

Specifically, the wireless communication system according to the present invention is a wireless communication system in which the wireless connection between one wireless base station and a plurality of wireless terminals is Orthogonal Frequency Division Multiple Access (OFDMA). And,
The wireless base station is
an information acquisition unit that acquires information about the queue length and priority in the current buffer;
a calculation unit that uses the queue length and priority information to calculate radio resource allocation with the wireless terminal based on OFDMA at regular time intervals;
a feedback unit that feeds back the radio resource allocation calculation result to the next radio resource allocation calculation performed by the calculation unit;
It is characterized by having the following.

This wireless communication system achieves both real-time performance and fairness by feeding back past wireless resource allocation amounts when calculating wireless resource allocation from the current queue length and priority in the buffer.
More specifically, the present wireless communication system is a wireless communication system that allocates wireless resources based on OFDMA to a plurality of wireless terminals at regular time intervals, in which a wireless base station receives information from each wireless terminal in a buffer. The queue length and priority information is received, and the wireless resources allocated to each wireless terminal are controlled by feedback control that simultaneously considers the received queue length and priority information, the amount of wireless resources allocated in the past, and the amount of wireless resources that can be allocated. Determine the amount of resources.

At this time, the information acquired by the information acquisition unit of the wireless communication system according to the present invention is information of the buffer of the wireless base station, and the wireless resource allocation is performed from the wireless base station to the wireless terminal. It can be assigned in the downstream direction.
Further, the information acquired by the information acquisition unit of the wireless communication system according to the present invention is information of the buffer of the wireless terminal, and the wireless resource allocation is performed in an upstream direction from the wireless terminal to the wireless base station. It is also possible to assign
That is, the radio resource allocation described above can be applied to both the downlink and uplink directions.

Further, the communication method according to the present invention is a communication method in a wireless communication system in which the wireless connection between one wireless base station and a plurality of wireless terminals is Orthogonal Frequency Division Multiple Access (OFDMA). There it is,
obtaining information on a queue length and priority in a current buffer of at least one of the wireless base station and the wireless terminal;
Calculating radio resource allocation with the wireless terminal based on OFDMA using the queue length and priority information at regular time intervals; and using the calculation result of the radio resource allocation as the next radio resource allocation. to provide feedback to the calculation of
It is characterized by

Further, the radio base station according to the present invention is a radio base station whose radio connection with a plurality of radio terminals is Orthogonal Frequency Division Multiple Access (OFDMA),
an information acquisition unit that acquires information on the queue length and priority in the current buffer of at least one of itself and the wireless terminal;
a calculation unit that uses the queue length and priority information to calculate radio resource allocation with the wireless terminal based on OFDMA at regular time intervals;
a feedback unit that feeds back the radio resource allocation calculation result to the next radio resource allocation calculation performed by the calculation unit;
It is characterized by having the following.

Note that the above inventions can be combined as much as possible.

The present invention can provide a wireless communication system, a communication method, and a wireless base station that can allocate wireless resources in real time by considering the communication quality of each wireless terminal and ensuring efficiency and fairness among users. .

1 is a diagram illustrating the basic structure of a wireless communication system according to the present invention. FIG. 2 is a diagram illustrating RU arrangement (20 MHz channel) in the IEEE 802.11ax standard. 1 is a diagram illustrating the basic structure of a wireless communication system according to the present invention. 1 is a diagram illustrating the basic structure of a wireless communication system according to the present invention. 1 is a diagram illustrating a wireless communication system according to the present invention. FIG. 2 is a diagram illustrating a communication method according to the present invention.

Embodiments of the invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. Note that components with the same reference numerals in this specification and the drawings indicate the same components.

(Summary of the invention)
Non-Patent Document 3 discloses radio resource allocation based on feedback control theory and scheduling based on PF (Proportional Fair) as a real-time and efficient radio resource allocation technology for LTE. However, it does not support RU allocation for IEEE 802.11ax wireless LAN. Furthermore, since radio resource allocation and scheduling are provided as separate functions, bidirectional information exchange between the functions is not possible, making it difficult to coordinate radio resource allocation and scheduling in real time. Therefore, with the technology disclosed in Non-Patent Document 3, it is difficult to simultaneously ensure efficiency and fairness among users.

The present invention is based on a wireless communication system in which a wireless base station allocates wireless resources to a plurality of wireless terminals based on OFDMA at regular time intervals. The wireless communication system of the present invention simultaneously takes into consideration the queue length and priority information in the current buffer, the amount of wireless resources that can be allocated, and the amount of wireless resources allocated in the past, and performs feedback control on the amount of wireless resources to be allocated to each wireless terminal. Determined by. Since the wireless communication system of the present invention considers current information and past information, it is possible to simultaneously ensure efficiency and fairness among users in real time.

Note that the present invention can be applied to both downlink radio resource allocation from a radio base station to a radio terminal and uplink radio resource allocation from a radio terminal to a radio base station.
In the case of downlink radio resource allocation, the radio base station determines the amount of radio resources to be allocated to each radio terminal based on the downlink queue length and priority information in its own buffer.
In the case of uplink radio resource allocation, a wireless terminal reports the uplink queue length and priority information in a buffer within the wireless terminal to the wireless terminal, and the wireless base station allocates to each wireless terminal based on the reported information. Determine the amount of radio resources and notify each wireless terminal of information on the available frequency and amount of radio resources.

(Embodiment)
FIG. 1 is a diagram illustrating the basic structure of a wireless communication system 301 of this embodiment. The wireless communication system 301 includes one wireless base station 10 and multiple wireless terminals 20. In the wireless communication system 301, the wireless connection between the wireless base station 10 and the wireless terminal 20 is Orthogonal Frequency Division Multiple Access (OFDMA).

FIG. 2 is a diagram illustrating an OFDMA RU arrangement according to the IEEE 802.11ax standard. The minimum RU size R _RU1 in the IEEE 802.11ax standard is 26 tones, and for example, a maximum of 9 RUs can be allocated in a 20 MHz channel. It is possible to allocate one RU per user, and the RU size can be changed from 26 tones (RU1), 52 tones (RU2), 106 tones (RU4), and 242 tones (RU9) as the amount of radio resources that can be allocated. It shall be possible to choose. The data rate of each wireless terminal is determined by the number of tones of the assigned RU and the MCS. Note that the wireless resource allocation function of this embodiment is provided in the wireless base station 10.

FIG. 3 is a diagram illustrating the functions of the wireless terminal 20. The wireless terminal 20 includes a wireless receiver 21, a buffer 22, and a wireless transmitter 23.
The radio receiver 21 receives radio resource allocation information including the allocated RU size from the radio base station 10.
The buffer 22 stores input uplink data and outputs data based on radio resource allocation information received from the radio base station 10. The wireless terminal 20 may include multiple buffers for each priority. The wireless terminal 20 obtains queue length information q[k] and priority information QoS[k] for each buffer or each flow (k represents time).
The wireless transmitter 23 transmits queue length information q[k] and priority information QoS[k] output from the buffer 22 to the wireless base station 10. When multiple buffers exist, the wireless transmitter 23 may transmit queue length information q[k] and priority information QoS[k] for each buffer or each flow.

FIG. 4 is a diagram illustrating the basic functions of the wireless base station 10. The wireless base station 10 includes a wireless receiver 11, a resource allocation computer 12, and a wireless transmitter 13.
The wireless receiving means 11 receives queue length information q[k] and priority information QoS[k] from each wireless terminal 20.
The resource allocation computer 12 assigns each queue length based on the queue length information q[k] obtained from the buffer (not shown) of the wireless base station 10 or the queue length information q[k] obtained from each wireless terminal 20. RU size proportional to is calculated and allocated to downlink communication or uplink communication with each wireless terminal 20. As the scheduling method, for example, a PF (Proportional Fair) method is adopted.
In addition, the resource allocation computer 12 determines whether the transmission data or Received data can be distributed to multiple buffers, and different scheduling methods can be applied to each buffer.
The wireless transmitter 13 transmits wireless resource allocation information including the RU size allocated to each wireless terminal 20.

FIG. 5 is a diagram illustrating additional functions of the wireless base station 10. Note that in this embodiment, for ease of explanation, uplink communication will be explained. The wireless base station 10 includes an information acquisition unit that acquires information on the queue length and priority in the current buffer;
a calculation unit that uses the queue length and priority information to calculate radio resource allocation with the wireless terminal based on OFDMA at regular time intervals;
a feedback unit that feeds back the radio resource allocation calculation result to the next radio resource allocation calculation performed by the calculation unit;
Equipped with.

Specifically, the radio base station 10 further includes a quality factor calculator 14, a fairness factor calculator 15, and a weighting factor calculator 16. The information acquisition unit is a functional unit (not shown) that acquires queue length information q[k] and priority information QoS[k] from a buffer (not shown) of the wireless receiver 11 or the wireless base station 10. The calculation units include a quality factor calculator 14, a weighting factor calculator 16, and a resource allocation calculator 12. The feedback unit is a fairness coefficient calculator 15.

FIG. 6 is a diagram illustrating a radio resource allocation method performed by the radio base station 10. This wireless resource allocation method is
acquiring information on the queue length and priority in the current buffer of at least one of the wireless base station 10 and the wireless terminal 20 (step S01);
Calculating wireless resource allocation with the wireless terminal 20 based on OFDMA at regular time intervals using the queue length and priority information (step S02);
Feedback of the radio resource allocation calculation result to the next radio resource allocation calculation (step S03); Allocating radio resources between the radio base station 10 and the wireless terminal 20 based on the calculation result (step S04) ).

[Step S01]
The wireless receiver 11 receives queue length information q[k] and priority information QoS[k] from each wireless terminal 20.

[Step S02]
The quality factor calculator 14 creates an N-dimensional priority vector {QoS[k]} whose elements are priority information QoS _i [k] (1≦i≦N) obtained from each wireless terminal 20, and calculates the quality An N-dimensional quality coefficient vector {K _P [k]} whose elements are coefficients K P _i (1≦i≦N) is calculated. However, N is the number of wireless terminals for which priority can be set, the total number of buffers of each wireless terminal, or the total number of flows of each wireless terminal. Also, { } represents a vector.

The priority can be set for each wireless terminal, each buffer of each wireless terminal, or each flow of each wireless terminal. When set for each wireless terminal, the number of elements of the priority vector, N, is equal to the number of wireless terminals; when set for each wireless terminal's buffer, the number of elements, N, of the priority vector is equal to the number of buffers for each wireless terminal. If it is set for each flow of each wireless terminal, the number of elements of the priority vector N is equal to the total number of flows of each wireless terminal.

ただし、太字はベクトルを表わし、Ｘ［ｋ］は各変数の時刻ｋにおけるＸの値を示す。また、係数ａ_０、ａ_１、ａ_２は、１からｐまでのＱｏＳ_ｉの範囲で品質係数Ｋ_Ｐｉが単調減少となるように設定する。 When calculating the quality factor vector {K _P [k]}, the quality factor calculator 14 calculates the quality factor of a high priority wireless terminal, buffer, or flow to be high.
For example, assuming that the priority is p levels from 1 to p, and 1 is the highest priority and the priority decreases in ascending order, the quality factor vector {K _P [k]} at time k is the priority vector at time k. It can be calculated using the following formula using {QoS[k]}.

However, bold letters represent vectors, and X[k] represents the value of X at time k for each variable. Further, the coefficients a ₀ , a ₁ , and a ₂ are set so that the quality coefficient K _Pi monotonically decreases in the QoS _i range from 1 to p.

Equation 1 is just an example, and the quality factor calculator 14 may set the quality factor K _Pi to arbitrary equally spaced or unevenly spaced values for each priority, without relying on the above equation. Furthermore, the quality factor calculator 14 can use a polynomial function or an exponential function of the priority vector {QoS[k]} other than Equation 1 for the quality factor vector {K _P [k]}.

[Step S03]
The fairness coefficient calculator 15 calculates a fairness coefficient from an N-dimensional allocated RU size vector {r ₃ [k]} whose elements are allocated RU sizes r _3i (1≦i≦N) output from the resource allocation calculator 12. An N-dimensional fairness coefficient vector {b[k]} whose elements are b _i (1≦i≦N) is calculated. The allocated RU size is, for example, "1" when the RU size is 26 tones, "2" when the RU size is 52 tones, "4" when the RU size is 106 tones, and "9" when the RU size is 242 tones.

ただし、Ｘ［ｋ］は時刻ｋにおける変数Ｘの値を示す。 The fairness coefficient calculator 15 calculates so that the fairness coefficients of wireless terminals, buffers, or flows to which radio resources have not been allocated at the previous sampling time are increased. For example, if the penalty coefficient is "penalty", the fairness coefficient b _i [k+1] at time k+1 is calculated using the fairness coefficient b _i [k] at time k and the allocated RU size r _3i [k] at time k. It can be calculated using the following formula.

However, X[k] indicates the value of variable X at time k.

In Equation 2, the determination is made based on the presence or absence of allocation of radio resources to wireless terminals, buffers, or flows, but a threshold is set and the determination is made based on whether allocations exceeding the threshold have been made in the past. Also good. Moreover, only the value before one sampling may be used, or the values before multiple sampling may be used in any combination. The size of the penalty coefficient is determined by the number of wireless terminals, the number of buffers, or the number of flows. For example, if there are 10 wireless terminals, it can be set to 0.1 by "1/number of connected devices."

[Step S02]
The weighting factor calculator 16 creates an N-dimensional queue length vector {q[k]} whose elements are queue length information q _i [k] (1≦i≦N) obtained from each wireless terminal 20, and , the quality coefficient vector {K _P [k]} output by the quality coefficient calculator 14, and the fairness coefficient vector {b[k]} output by the fairness coefficient calculator 15, _from ] (1≦i≦N), an N-dimensional weighting coefficient vector {w[k]} is calculated.

ただし、［ｋ］は各変数の時刻ｋにおける値を示す。また、演算子“〇”はアダマール積を表していて、要素毎の積を計算する。 The weighting factor can be calculated in combination with the quality factor and the fairness factor so that it is proportional to the queue length. For example, when making it proportional to the queue length, the weighting coefficient vector {w[k]} at time k is the queue length vector {q[k]} at time k, the quality coefficient vector {K _P [k]} at time k, and It can be calculated using the following formula using the fairness coefficient vector {b[k]} at time k.

However, [k] indicates the value of each variable at time k. Furthermore, the operator “〇” represents Hadamard product, and calculates the product for each element.

Further, in addition to calculating the equation 3, the weighting coefficient may be calculated by combining the change rate of the queue length and the cumulative value of the queue length. In this case, terms of the differential value or integral value of {q[k]} can be linearly combined.

[Step S02]
Additional functions of the resource allocation computer 12 will be explained. The resource allocation computer 12 calculates the allocated RU size vector {r ₃ [k]} from the weighting factor vector {w[k]} output from the weighting factor calculator 16. An example of calculating the allocated RU size vector {r ₃ [k]} will be described below.

First, among the N elements of the weighting coefficient vector {w[k]}, M elements, which are the maximum number of available RUs, are selected in order of increasing value. For example, M=9 for FIG. 2(A), M=5 for FIG. 2(B), M=3 for FIG. 2(C), and M=1 for FIG. 2(D). Become. If multiple elements have the same value, they are selected randomly. For the selected M elements, the same value is assigned to the same element of the newly defined N-dimensional weighting coefficient vector {w'[k]}. Assign 0 to unselected elements.

ただし、［ｋ］は各変数の時刻ｋにおける値を示す。また、Ｒ_Ｔは利用可能なデータレートである。例えば、２０ＭＨｚチャネルで１６－ＱＡＭ、符号化率３／４の場合はＲ_Ｔを４８．８Ｍｂｐｓとする。 Radio resources are allocated to each wireless terminal, buffer or flow in proportion to the weighting factor. For example, the following formula calculates an N-dimensional provisional allocation rate vector {r ₁ [k]} at time k whose elements are provisional allocation rates r _1i [k] (1≦i≦N).

However, [k] indicates the value of each variable at time k. Also, _RT is the available data rate. For example, in the case of a 20 MHz channel, 16-QAM, and a coding rate of 3/4, _RT is set to 48.8 Mbps.

また、［ｋ］は各変数の時刻ｋにおける値を示す。Ｒ_ＲＵ１は２６トーンの場合のデータレートを表している。端数処理には、四捨五入以外に切り上げや切り捨てを用いても良い。 Next, from the provisional allocation rate vector {r ₁ [k]}, the provisional allocation RU size vector {r _{2 [k]} at the N-dimensional time k has the provisional allocation RU size r 2i (} 1≦i≦N) as an element. Calculate. Since the provisional allocation RU size _r2i takes only integer values, rounding is performed to the decimal point. For example, when rounding is used for fraction processing, the provisional allocation RU size vector {r ₂ [k]} can be calculated as follows.

Further, [k] indicates the value of each variable at time k. _RRU1 represents the data rate in the case of 26 tones. In addition to rounding, rounding up or down may be used for fraction processing.

The values that the allocated RU size r _3i [k] can take are limited to predetermined integer values. For example, in the case of a 20MHz channel, the RU size is 1, 2, 4, or 9 (26 tones (RU1), 52 tones (RU2), 106 tones (RU4), 242 tones (RU9)) as shown in Figure 2. Therefore, the values that each element of the allocated RU size vector {r ₃ [k]} can take are also 1, 2, 4, and 9.

Finally, the allocated RU size vector {r ₃ [k]} is generated as follows.
Values are assigned to the same elements of the allocated RU size vector {r ₃ [k]} in descending order of the value of the provisional allocated RU size vector {r ₂ [k]}. If multiple elements have the same value, they are selected randomly. The values of each element assigned to {r ₃ [k]} are accumulated, and the value substitution is repeated as long as the accumulated value does not exceed the maximum number M of available RUs. When the integrated value exceeds M, the assignment is stopped and 0 is assigned to the remaining elements.

[Step S04]
The wireless transmitter 13 receives the allocated RU size vector {r ₃ [k]} calculated by the resource allocation calculator 12, and transmits wireless resource allocation information including the RU size allocated to each wireless terminal, buffer or flow to the wireless terminal. Send to 20.

(Other embodiments)
In the above embodiment, the wireless resource allocation method for uplink communication has been described, but it is clear that the method can also be applied to downlink communication.
Although the above embodiments describe a wireless communication system based on the IEEE 802.11ax standard, it is clear that the embodiments are applicable to any communication system that employs OFDMA.
Furthermore, the wireless base station 10 can be realized by a computer and a program, and the program can be recorded on a recording medium or provided through a network.

10: Wireless base station 11: Wireless receiver 12: Resource allocation computer 13: Wireless transmitter 14: Quality factor calculator 15: Fairness factor calculator 16: Weighting factor calculator 20: Wireless terminal 21: Wireless receiver 22: Buffer 23: Wireless transmitter 301: Wireless communication system

Claims (5)

A wireless communication system in which a wireless connection between one wireless base station and a plurality of wireless terminals is Orthogonal Frequency Division Multiple Access (OFDMA),
The wireless base station is
an information acquisition unit that acquires queue length and priority information for each flow in the current buffer;
a calculation unit that uses the queue length and priority information to calculate radio resource allocation with the wireless terminal based on OFDMA at regular time intervals;
a feedback unit that feeds back the radio resource allocation calculation result to the next radio resource allocation calculation performed by the calculation unit;
A wireless communication system comprising: The information acquired by the information acquisition unit is information of the buffer of the wireless base station,
The wireless communication system according to claim 1, wherein the wireless resource allocation is a downlink allocation from the wireless base station to the wireless terminal. The information acquired by the information acquisition unit is information in the buffer of the wireless terminal,
The wireless communication system according to claim 1, wherein the wireless resource allocation is an uplink allocation from the wireless terminal to the wireless base station. A communication method in a wireless communication system in which a wireless connection between one wireless base station and a plurality of wireless terminals is Orthogonal Frequency Division Multiple Access (OFDMA), comprising:
acquiring queue length and priority information for each flow in a current buffer of at least one of the wireless base station and the wireless terminal;
Calculating radio resource allocation with the wireless terminal based on OFDMA using the queue length and priority information at regular time intervals; and using the calculation result of the radio resource allocation as the next radio resource allocation. to provide feedback to the calculation of
A communication method characterized by: A wireless base station whose wireless connection with a plurality of wireless terminals is Orthogonal Frequency Division Multiple Access (OFDMA),
an information acquisition unit that acquires queue length and priority information for each flow in the current buffer of at least one of itself and the wireless terminal;
a calculation unit that uses the queue length and priority information to calculate radio resource allocation with the wireless terminal based on OFDMA at regular time intervals;
a feedback unit that feeds back the radio resource allocation calculation result to the next radio resource allocation calculation performed by the calculation unit;
A wireless base station comprising:

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