JP4536706B2 - Bandwidth allocation method - Google Patents

Description

  The present invention relates to a technique of a bandwidth allocation method in a wireless communication system.

In recent years, wireless tags, Bluetooth (Registered Commercial Code), ZigBee (Registered Commercial Code), etc., short-range wireless in fields centering on equipment control, transportation, distribution, environmental conservation, food and beverage industry, agriculture, earthquake monitoring, medical welfare, etc. Ubiquitous networks using communication systems are beginning to spread.
In the future, with the development of applications and services, the number of network users is expected to increase. Thus, a wide area ubiquitous network that can provide various applications and services to a larger number of users and expand the service area has attracted attention.

In such a situation, the network targeted by the present invention is composed of base stations connected to a fixed network and a large number of wireless terminals scattered in a wide area, and the wireless terminals are directly accommodated in the base stations. .
In addition, the wireless terminal in such a network is a battery-powered terminal having a low power consumption and a low function having only minimum functions such as data measurement and transmission of the measured data. Such traffic from a wireless terminal to a base station is characterized by (1) a small amount of data, (2) a relatively long transmission interval, and (3) periodic data generation.

Since a large number of such wireless terminals exist under one base station, the traffic characteristics include a lot of uplink periodic traffic, and the total traffic tends to increase.
Further, in the network, in order to collect data from as many wireless terminals as possible, it is necessary to accommodate as many wireless terminals as possible in one base station.
Therefore, in these networks, a MAC protocol capable of realizing a high throughput and a low transmission delay time while efficiently accommodating a large number of low function wireless terminals in one base station is required.

As a MAC protocol that satisfies this requirement, a dynamic slot assignment (DSA) method, which is one of centralized control methods with high resource utilization efficiency, is used. In this method, TDMA-TDD (Time Division Multiple Access-Time Division Duplex) is used as an access method.
In this method, a base station dynamically allocates slots (bandwidths) according to a request from a wireless terminal.

  FIG. 10 shows an example of the MAC frame configuration. The MAC frame is divided into an uplink and a downlink, the downlink is composed of a broadcast section and a demand assignment section, and the uplink is composed of a demand assignment section and a random access section.

  Also, in order to transmit and receive data and control information, each section includes a BCH (Broadcast Channel), an FCH (Frame Channel), an ACH (Access feedback channel), and an SCH (Short transport port). Channels of Channel: short transmission channel), LCH (Long Transport Channel), and RCH (Random Channel) are used.

  The BCH is used to notify the radio terminal of base station attribute information (base station ID, frame number, etc.), and the FCH is the slot assignment information (assignment) of the demand assignment section in which slot assignment is performed on a radio terminal basis. The ACH is used to notify access information (result of random access in the previous frame).

  The SCH has a fixed length, and is used to transmit and receive control information for each wireless terminal such as a bandwidth request (Resource Request: RREQ) and an ARQ (Automatic Repeat Request). The LCH has a fixed length and is used for transmitting and receiving user data. The RCH is a fixed-length channel for random access, and is used for a wireless terminal to transmit the RREQ.

Further, as a method for improving uplink periodic traffic efficiently, there is a method in which a base station periodically allocates a fixed band based on the periodicity of traffic of a wireless terminal.
As shown in FIG. 11, by exchanging message information between the upper layer of the wireless terminal and the base station before starting communication, the allocation period, allocated channel, allocated band (number of channels), etc. Is determined by negotiating between the wireless terminal and the base station. In the base station, allocation is performed for each allocation period based on the determined allocation information.
Specifically, periodic allocation of a fixed band is realized by transmitting information indicating an allocation start position, an allocation channel, and an allocation band in the FCH to the corresponding wireless terminal for each allocation period.

At this time, the allocation channel is an LCH for data transmission and an SCH for bandwidth request, and a bandwidth (number of channels) is allocated for each channel. In addition, when changing allocation information, negotiation by exchanging message information between higher layers is performed as before the start of communication.
Non-patent document 1 is known as such a prior art.
Development of 5GHz Band Advanced Wireless Access (AWA) System-MAC / DCL Function-2000 Society Conference of IEICE B-5-39 pp. 327

In the conventional method for periodically allocating the fixed band, when accommodating traffic in which the amount of transmission data from the wireless terminal varies, the LCH band for data transmission and the SCH band for band request based on the band information determined by negotiation Each will be secured.
However, when the traffic volume is larger than the LCH allocated band, it is not possible to transmit only with the LCH allocated band, and it is necessary to transmit a band request for the surplus traffic using the SCH band and wait for data transmission band allocation. Therefore, there is a problem that transmission characteristics deteriorate.

On the other hand, when the traffic volume is smaller than the allocated bandwidth of LCH, there is a problem that the use efficiency of radio resources deteriorates because an unnecessary SCH bandwidth is allocated in addition to an excessive LCH bandwidth.
As described above, the bandwidth control method according to the prior art has a problem that high throughput cannot be obtained when the amount of transmission data from the wireless terminal varies.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a bandwidth allocation method capable of obtaining high throughput even when the amount of transmission data from a wireless terminal varies. It is in.

  The present invention has been made to solve the above-described problem, and the invention according to claim 1 is a bandwidth allocation method in a base station of a wireless communication system in which a plurality of terminals communicate by sharing a wireless line. For each terminal, measure the amount of data transmitted from the terminal, and calculate the amount of data and its occurrence probability for the latest N times (N is an integer of 2 or more) measurement results for the band allocation target terminal; By setting a plurality of allocation candidate bands in advance and applying the data amount, the occurrence probability, and the allocation candidate band to each of the allocation candidate bands, a throughput expectation is calculated from the total band amount required to complete transmission. A value is calculated, and an allocation candidate band that maximizes the calculated expected throughput value is determined as allocation information in a next period of the band allocation target terminal. Is that bandwidth allocation method.

  According to a second aspect of the present invention, in a bandwidth allocation method in a base station of a wireless communication system in which a plurality of terminals communicate by sharing a wireless channel, the amount of data transmitted from the terminal is measured for each terminal. For the latest N times (N is an integer greater than or equal to 2) measurement results for the bandwidth allocation target terminal, the data amount and the occurrence probability are calculated, and the allocated bandwidth determined by the data amount, the occurrence probability, and the negotiation is applied. In this case, the throughput expected value at the time of channel assignment for data transmission is calculated from the total bandwidth required for completing transmission, and the data amount when the data amount, the occurrence probability, and the bandwidth request channel are used. From the total amount of bandwidth required to complete the transmission, the expected throughput value when allocating the bandwidth request channel is calculated, and the calculated data transmission channel is calculated. Comparing the expected throughput value at that time with the expected throughput value at the time of channel allocation for bandwidth request, and determining a channel that can obtain a high expected throughput value as allocation information in the next period of the bandwidth allocation target terminal. This is a characteristic bandwidth allocation method.

  According to a third aspect of the present invention, in the comparison of the calculated expected throughput value at the time of channel assignment for data transmission and the expected throughput value at the time of bandwidth request channel assignment, the calculated bandwidth request channel assignment time If the expected bandwidth value is higher, the bandwidth request channel bandwidth is used as allocation information in the next period of the bandwidth allocation target terminal, and the calculated throughput expectation at the time of channel allocation for data transmission 3. The bandwidth allocation method according to claim 2, wherein when the value is higher, the allocated bandwidth determined by the negotiation is used as allocation information in a next period of the bandwidth allocation target terminal. .

  According to a fourth aspect of the present invention, in a bandwidth allocation method in a base station of a wireless communication system in which a plurality of terminals share a wireless channel and perform communication, the amount of data transmitted from the terminal is measured for each terminal. For the latest N times (N is an integer greater than or equal to 2) measurement results for the band allocation target terminal, the data amount and the occurrence probability are calculated, a plurality of allocation candidate bands are set in advance, and each of the allocation candidate bands On the other hand, an expected throughput value is calculated from the total amount of bandwidth required to complete transmission when the data amount, the occurrence probability, and the allocation candidate bandwidth are applied, and the maximum expected value among the calculated expected throughput values. Is selected as the maximum throughput expectation value, and the data amount is transmitted when the data amount, the occurrence probability, and the bandwidth request channel are used. From the total amount of bandwidth required to complete, calculate the expected throughput value when allocating the bandwidth request channel, and compare the selected maximum expected throughput value and the calculated expected throughput value when allocating the bandwidth request channel Then, the bandwidth allocation method is characterized in that a channel for which a high expected throughput value is obtained is determined as allocation information in the next period of the bandwidth allocation target terminal.

According to a fifth aspect of the present invention, in the comparison between the selected maximum expected throughput value and the calculated expected throughput value at the time of channel allocation for bandwidth request, the calculated expected throughput value at the time of channel allocation for bandwidth request. Is higher, the bandwidth request channel bandwidth is assigned information in the next period of the bandwidth allocation target terminal, and if the selected maximum throughput expectation value is higher, the maximum 5. The bandwidth allocation method according to claim 4, wherein an allocation candidate band that is an expected throughput value is used as allocation information in a next period of the band allocation target terminal.

  The invention according to claim 6 is the band allocation method according to claim 1 or 4, wherein the allocation candidate band is determined based on the measured data amount.

  According to the present invention, the base station measures the traffic for each wireless terminal, and assigns a channel based on the measured traffic distribution, so that even when the amount of transmission data from the wireless terminal varies, it is high. There is an effect that the throughput can be obtained.

(principle)
As a method of the present invention, the base station first measures the traffic for each wireless terminal at the base station, and executes a bandwidth control method for obtaining high throughput by the following three methods based on the measured traffic distribution. .

First, in the case of a single communication procedure, the first method is a method of calculating a bandwidth amount that maximizes throughput and assigning it for data transmission.
Further, the second method has a plurality of communication procedures, and when there is a negotiation of a band for data transmission from the communication terminal to the base station, at the time of channel allocation for data transmission determined by the negotiation and for bandwidth request This is a method of selecting and allocating a channel that can obtain a high throughput by comparing the throughput with the channel allocation.

Further, the third method has a plurality of communication procedures, and when there is no negotiation of the band for data transmission from the communication terminal to the base station, the amount of band for data transmission is determined in the first method, Similar to the second method, a method of comparing the throughput when the band is allocated as a data transmission band and the band requesting band is allocated, and selecting and allocating an allocation channel that can obtain a high throughput. It is.
Each method will be described in detail later using the first to third embodiments.

(Measurement traffic distribution)
First, a method will be described in which the base station measures the traffic for each wireless terminal and obtains the distribution of the measured traffic.
Here, a case is considered where the wireless terminal transmits data for each frame, and the base station performs band allocation to the corresponding wireless terminal in the allocation cycle 1.
As shown in FIG. 2, the base station stores the amount of data actually transmitted by the wireless terminal for each allocation period (allocation frame) for each wireless terminal. That is, when there is data transmission from the wireless terminal, the base station associates the allocated frame number and the data amount and stores them in the storage unit as a table.
For example, this data amount is the amount of data transmitted by the LCH when the wireless terminal uses only LCH at the time of transmission, and the amount of data transmitted by the LCH when LCH and SCH are used at the time of transmission. And the amount of data requested for bandwidth on the SCH.
In FIG. 2, the allocated frames up to the frame number 50 (# 50) and the data amount at that time are stored in association with each other. Hereinafter, and in FIG. 2, description will be made using “#” as a symbol indicating a frame number.

Next, the base station uses the received data of the latest specified value N times as measurement traffic, generates a histogram representing the occurrence frequency (number of times) for the data amount from the measurement traffic, and stores it as a measurement traffic distribution. Here, the prescribed value N is a predetermined value.
For example, FIG. 3 shows a measurement traffic distribution for the latest 30 times when the above-mentioned specified value N is 30. That is, FIG. 3 shows a measurement traffic distribution with frame numbers # 21 to # 50.

Next, the base station calculates an occurrence probability P (D _i ) for each data amount from the measured traffic distribution. Here, the occurrence probability P (D _i ) is obtained by dividing the occurrence frequency of the data amount D _i by the specified value N. In other words, the occurrence probability P (D _i ) is the occurrence frequency / specified value N (= 30) of the data amount D _i . Here, i is a natural number of i = 1,.
FIG. 4 shows the occurrence probability P (D _i ) for each data amount with respect to the measured traffic distribution of FIG.

Next, the base station uses the measurement traffic distribution of FIG. 3 calculated above to determine allocation information in # 51, which is the next allocation frame, by the first to third methods described above as the principle. The communication with the wireless terminal is executed by allocating the channel with the determined allocation information.
Hereinafter, first to third methods for allocating channels using the measurement traffic distribution of FIG. 3 at the base station will be described through first to third embodiments.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram showing a configuration of a band allocation device in a base station according to the first to third embodiments of the present invention. Since the present invention relates to a band allocation technique for a base station, other configurations of the base station will not be described.

The base station 1 and the wireless terminal 2 are connected via a wireless network 3.
The base station 1 includes a transmission / reception unit 101, a received data amount measurement unit 102, a received data amount storage unit 103, an occurrence probability calculation unit 104, an occurrence probability storage unit 105, a throughput expected value calculation unit 106, an expected throughput value selection unit 107, a setting Part 108.

The transmission / reception unit 101 transmits / receives data to / from the wireless terminal 2 via the wireless network 3.
The reception data amount measurement unit 102 measures the data amount of data transmitted / received by the transmission / reception unit 101 to / from the wireless terminal 2 for each allocation frame, and sends the measured data amount for each allocation frame to the reception data amount measurement unit 102. And the data amount are registered and stored in the received data amount storage unit 103 as a table (received data amount table).

The occurrence probability calculation unit 104 reads the table (reception data amount table) by associating the allocation frame number and the data amount stored in the reception data amount storage unit 103, generates the measurement traffic distribution described above, and Then, the occurrence probability P (D _i ) for each data amount is calculated from the generated measurement traffic distribution.
Further, the occurrence probability calculation unit 104 registers and stores the generated measurement traffic distribution and the occurrence probability P (D _i ) for each calculated data amount in the occurrence probability storage unit 105.

Note that the occurrence probability calculation unit 104 calculates a measurement traffic distribution and an occurrence probability P (D _i ) for the latest N times (N is an integer of 2 or more) measurement results regarding the band allocation target terminal.
When the data amount is less than N times (N is an integer of 2 or more), the occurrence probability calculation unit 104 sets the allocated bandwidth determined by the negotiation before the start of communication as the LCH allocated bandwidth in the next allocated frame, Converted to the number of LCHs, the allocated bandwidth in communication with the wireless terminal 2 is set via the setting unit 108.

In the first embodiment, the expected throughput calculation unit 106 reads the occurrence probability P (D _i ) for each data amount from the occurrence probability storage unit 105, sets a plurality of allocation candidate bands in advance, and sets the set allocation candidate bands. For each of these, an expected throughput value is calculated from the read data amount and occurrence probability P (D _i ) and the total bandwidth required to complete transmission when the allocation candidate bandwidth is applied.

In the second embodiment, the throughput expected value calculation unit 106 reads the occurrence probability P (D _i ) for each data amount from the occurrence probability storage unit 105, and reads the read data amount and occurrence probability P (D _i ). Then, from the total bandwidth required to complete the transmission when the allocated bandwidth determined by the negotiation is applied, a throughput expected value at the time of channel allocation for data transmission is calculated, and the read data amount and occurrence probability P ( D _i ) and the total amount of bandwidth required to complete the transmission of the read data amount when the bandwidth request channel is used, the expected throughput value when allocating the bandwidth request channel is calculated.

Further, in the third embodiment, the throughput expected value calculation unit 106 reads the occurrence probability P (D _i ) for each data amount from the occurrence probability storage unit 105, sets a plurality of allocation candidate bands in advance, and sets the assigned allocation. For each of the candidate bands, the expected throughput value is calculated from the read data amount and occurrence probability P (D _i ) and the total bandwidth required to complete transmission when the allocation candidate band is applied. The maximum expected throughput value is selected as the maximum expected throughput value from the expected throughput values, and is read when the read data amount and occurrence probability P (D _i ) and the bandwidth request channel are used. From the total amount of bandwidth required to complete the transmission of the data amount, an expected throughput value at the time of channel allocation for bandwidth request is calculated.

  In the first embodiment, the throughput expectation value selection unit 107 selects a channel and an allocation candidate band having the maximum throughput expectation value from the throughput expectation values calculated by the throughput expectation value calculation unit 106 as a band allocation target terminal. Is selected and determined as allocation information in the next cycle. Further, the expected throughput selection unit 107 sets the selected allocation information as the LCH allocation band in the next allocation cycle, converts it into the number of LCHs, and sets the allocation band in communication with the wireless terminal 2 via the setting unit 108. .

In the second embodiment, the expected throughput value selection unit 107 compares the maximum expected throughput value selected by the expected throughput value calculation unit 106 with the calculated expected throughput value at the time of channel allocation for bandwidth request. A channel from which an expected throughput value is obtained is determined as allocation information in the next cycle of the band allocation target terminal.
Further, in the second embodiment, the throughput expectation value selection unit 107 calculates the throughput expectation value at the time of channel assignment for data transmission calculated by the throughput expectation value calculation unit 106 and the throughput expectation value at the time of channel assignment for bandwidth request. In the comparison, when the calculated expected throughput value at the time of channel allocation for bandwidth request is higher, the bandwidth of the bandwidth request channel is calculated as allocation information in the next period of the bandwidth allocation target terminal. When the expected throughput value at the time of data transmission channel allocation is higher, the allocated bandwidth determined by negotiation is used as allocation information in the next cycle of the bandwidth allocation target terminal.

Further, in the third embodiment, the expected throughput value selection unit 107 compares the maximum expected throughput value selected by the expected throughput value calculation unit 106 with the calculated expected throughput value at the time of channel allocation for bandwidth request. A channel from which an expected throughput value is obtained is determined as allocation information in the next cycle of the band allocation target terminal.
Further, in the third embodiment, the expected throughput value selection unit 107 is calculated by comparing the maximum expected throughput value selected by the expected throughput value calculation unit 106 with the calculated expected throughput value at the time of channel allocation for bandwidth request. If the expected throughput value when allocating the bandwidth request channel is higher, the bandwidth request channel bandwidth is used as allocation information in the next cycle of the bandwidth allocation target terminal, and the selected maximum throughput expectation value If it is higher, the allocation bandwidth candidate that is the maximum expected throughput value is used as allocation information in the next cycle of the bandwidth allocation target terminal.

  The setting unit 108 sets the allocation information selected and determined by the expected throughput value selection unit 107 for communication between the base station 1 and the wireless terminal 2.

[First Embodiment]
In the first embodiment, the base station 1 determines the LCH allocation band (the number of LCHs) for data transmission in the allocation information using the measurement traffic distribution of FIG. The “allocated bandwidth” in the present invention will be described below assuming that it is information indicating “how much data can be sent at one time”.

  The operation of the base station 1 determining the number of LCHs in # 51, which is the next allocation frame, by the first method will be described using the flowchart of FIG. Here, description will be made assuming that the base station 1 measures and stores the data amount of the radio terminal 2 for each allocation frame for each radio terminal 2 before the operation of the flowchart of FIG. That is, description will be made assuming that the received data amount storage unit 103 stores the allocation frame number and the data amount in association with each other as a table (reception data amount table).

First, the occurrence probability calculation unit 104 detects whether or not the stored number of measured allocation frames is equal to or greater than a specified value N (step S101).
When the detection result in step S101 is that the number of measurements is smaller than the specified value N, the occurrence probability calculation unit 104 sets the allocated band determined in the negotiation before the start of communication as the LCH allocated band in the next allocated frame # 51, It converts into the number of LCH (step S102), and ends.

On the other hand, if the detection result in step S101 is that the number of measurements is equal to or greater than the specified value N, the occurrence probability storage unit 105 creates a measurement traffic distribution from the latest N measurement values and calculates the occurrence probability of each data amount. (Step S103).
Next, the expected throughput value calculation unit 106 calculates an expected throughput value for the allocated bandwidth candidate (step S104). The allocation band candidate and a method of calculating the expected throughput value for the allocation band candidate will be described in detail later.

Next, the expected throughput selection unit 107 selects an allocation bandwidth candidate that provides the maximum expected throughput value from among the expected throughput values of all allocation bandwidth candidates, and selects the selected allocation bandwidth candidate as an LCH. The number is converted to a number (step S105), and the process ends.
In the next allocation frame, the setting unit 108 allocates the allocated bandwidth for data transmission (number of LCHs) determined in this processing flow to the corresponding wireless terminal 2.

Next, a method for calculating the expected throughput value for the allocated bandwidth candidate, which is executed by the expected throughput value calculation unit 106 in step S104, will be described in detail.
In this method, allocation band candidates C _i (i = 1, 2,..., M) are determined in advance from the range of the measurement data amount (D _i ). Here, M is an integer of 2 or more.
Here, as an example, the bandwidth allocation candidate C _i is set as the measurement data amount D _i . That is, allocation band candidate C _i = measurement data amount D _i (i = 1,..., 8). Then, the expected throughput value when the allocated bandwidth candidate is applied is calculated. The expected throughput value E _thr (C _i ) of the allocation band candidate C _i (i = 1,..., 8) is calculated by the following equation (1). In Equation 1, n represents the number of measurement data amounts that are equal to or smaller than the allocation band candidate.

Here, B (C _i ) is the total amount of bandwidth required until data transmission of the wireless terminal 2 is completed when the allocation bandwidth candidate C _i is used. The total bandwidth B (C _i ) will be described later in detail using FIG.

In the above, as an example of a method for determining the allocation bandwidth candidate C _i (i = 1, 2,..., M) from the range of the measurement data amount (D _i ), the bandwidth allocation candidate C _i is determined as the measurement data amount. It was described as the D _i, but is not limited to this. The allocation band candidate C _i is not particularly limited except that it is selected from the range of the data amount D _i of the measurement traffic distribution. for that reason. The value of the allocation bandwidth candidate C _i does not necessarily match the value of the measurement data amount D _i .

Next, the total bandwidth B (C _i ) will be described in detail with reference to FIG. FIG. 6 shows a data transmission sequence as an example when allocating an LCH band for data transmission.
As shown in FIG. 6, first, in the allocation frame, allocation information is notified to the corresponding wireless terminal by FCH, and the corresponding wireless terminal transmits data to the LCH band of the demand assignment area specified by FCH. .
When receiving data from the wireless terminal, the base station transmits the reception result on the SCH of the next frame.

In the data transmission sequence of FIG. 6, data transmission is completed using the first and second MAC frames. In FIG. 6, B represents communication in the BCH band, F represents the FCH band, A represents the ACH band, and DA represents the LCH band in the demand assignment area.
Note that the number of frames required to complete transmission varies depending on traffic conditions. The sequence shown here is the shortest case.

From the above, as the total bandwidth B (C _i ) required until the data transmission is completed, the FCH band indicating the LCH band allocation information of the first MAC frame, the LCH band of the first MAC frame, the second The total amount of the FCH band indicating the allocation information of the SCH band of the second MAC frame and the SCH band of the second MAC frame.
Note that the FCH band indicating the allocation information of the LCH band of the first MAC frame and the FCH band indicating the allocation information of the SCH band of the second MAC frame are different from the radio terminal to be allocated. It is a band of FCH used between.
In addition, the 1st method in 1st Embodiment is also a method of estimating the band which a communication terminal uses.

[Second Embodiment]
In the second embodiment, the base station 1 determines an allocation channel in the allocation information using the measurement traffic distribution of FIG.
The operation of the base station 1 in the second method will be described using the flowchart of FIG. Here, it is assumed that the base station 1 measures and stores the data amount of the wireless terminal 2 for each allocation frame with respect to each wireless terminal 2 before the operation of the flowchart of FIG. That is, description will be made assuming that the received data amount storage unit 103 stores the allocation frame number and the data amount in association with each other as a table (reception data amount table).

First, the occurrence probability calculation unit 104 detects whether or not the stored number of measured allocation frames is equal to or greater than a specified value N (step S201).
When the detection result in step S201 indicates that the number of measurements is smaller than the specified value N, the occurrence probability calculation unit 104 sets the allocated channel as the LCH for data transmission, sets the band determined in the negotiation before the start of communication as the allocated band, It converts into the number of LCH (step S202), and complete | finishes.
In step S202, LCH is selected as the allocation channel, but SCH for bandwidth request may be selected. That is, in step S202, either channel may be selected using LCH or SCH.

On the other hand, if the detection result in step S201 indicates that the number of measurements is equal to or greater than the specified value N, the expected throughput calculation unit 106 creates a measurement traffic distribution from the latest N measured values, and determines the occurrence probability of each data amount. Calculate (step S203).
Next, the expected throughput calculation unit 106 calculates the expected throughput value E _{thr_LCH} when assigning a channel for data transmission (step S204). A method of calculating the expected throughput value E _{thr_LCH} at the time of channel assignment for data transmission will be described later.

Next, the expected throughput value calculation unit 106 calculates the expected throughput value E _{thr_SCH} at the time of bandwidth allocation channel allocation (step S205). A method of calculating the expected throughput value E _{thr_SCH} at the time of channel allocation for bandwidth request will be described later.

Next, the throughput expectation value selection unit 107, the expected throughput value _{E Thr_LCH} in channel allocation for data transmission calculated in step S204, the expected throughput value _{E Thr_SCH} in channel allocation for the calculated bandwidth request in step S205 , Are compared (step S206), and a channel capable of obtaining a high throughput is selected as an assigned channel (steps S207 and S208).

In the comparison of step S206, when the throughput request value E _{thr_SCH} at the time of channel allocation for bandwidth request is higher and the SCH channel is selected as an allocation channel that can obtain a high throughput, the throughput expected value selection unit 107 The bandwidth is set as the SCH allocated bandwidth (step S207).
On the other hand, when the throughput expectation value E _{thr_LCH} at the time of data transmission channel assignment is higher in the comparison of step S206 and an LCH channel is selected as an assignment channel that _provides a higher throughput, the expected throughput value selection unit 107 Then, the allocated band NB determined by the negotiation is set as the allocated band and converted into the number of LCHs (step S208).
In the next allocation frame, the setting unit 108 allocates the allocation channel and the allocation band determined by the expected throughput value selection unit 107 in this processing flow to the corresponding wireless terminal 2.

Next, a method in which the expected throughput value calculation unit 106 calculates the expected throughput value E _{thr_LCH} at the time of channel assignment for data transmission executed in step S204 will be described.
The throughput expected value E _{thr_LCH} at the time of channel allocation for data transmission is the throughput expected value E _{thr_LCH} (NB) of the allocated band NB determined by negotiation, and is calculated by the following equation (2). In Equation 2, n represents the number of measurement data amounts that are equal to or smaller than the allocated band NB.

Here, B _LCH (NB) in Expression 2 is the total bandwidth required until the data transmission of the wireless terminal 2 is completed when the allocated bandwidth NB determined by negotiation is used.
As the total bandwidth B _LCH (NB) required until this data transmission is completed, the FCH band indicating the LCH band allocation information, the LCH band, and the SCH band allocation information are indicated as in the first embodiment. This is the total amount of the FCH band and the SCH band.

Next, a method of calculating the expected throughput value E _{thr_SCH} at the time of channel allocation for bandwidth request in step S205 will be described.
The expected throughput value E _{thr_SCH} at the time of channel allocation for bandwidth request is calculated by the following equation (3). In Equation 3, n represents the type of data amount.

B _{SCH in} Equation 3 is the total amount of bandwidth required until data transmission of the wireless terminal 2 is completed when the bandwidth requesting SCH channel is used. Next, the total bandwidth B _SCH will be described with reference to FIG.

FIG. 8 shows a data transmission sequence as an example at the time of SCH band allocation for bandwidth request.
From FIG. 8, first, in the allocation frame, allocation information (SCH channel for bandwidth request) is notified to the corresponding wireless terminal by FCH, and the corresponding wireless terminal is in the SCH band of the demand assignment area specified by FCH. In response to this, a bandwidth request for data transmission is transmitted.

When the base station receives the bandwidth request from the wireless terminal, the base station transmits the reception result using the SCH in the next frame. Next, the base station allocates the requested band as the LCH band to the demand assignment area, and notifies the corresponding wireless terminal by the FCH of the allocation frame.
Next, the corresponding wireless terminal performs data transmission to the base station using the LCH band of the demand assignment area specified by the FCH. Next, when receiving data from the wireless terminal, the base station transmits the reception result to the wireless terminal on the SCH of the next frame.

In the data transmission sequence of FIG. 8, data transmission is completed using the first to third MAC frames. In FIG. 8, B represents communication in the BCH band, F represents the FCH band, A represents the ACH band, and DA represents the LCH band in the demand assignment area.
Note that the number of frames required to complete transmission varies depending on traffic conditions. The sequence shown here is the shortest case.

From the above, the total bandwidth B _SCH necessary for completing the data transmission includes the FCH band indicating the SCH band allocation information of the first MAC frame, the SCH band of the first MAC frame, and the second MAC. FCH band indicating allocation information of SCH band of frame, SCH band of second MAC frame, FCH band indicating allocation information of LCH band of second MAC frame, LCH band of second MAC frame, third This is the total amount of the FCH band indicating the allocation information of the SCH band of the second MAC frame and the SCH band of the third MAC frame.
The FCH band indicating the allocation information of the SCH band of the first MAC frame, the FCH band indicating the allocation information of the SCH band of the second MAC frame, and the LCH band allocation information of the second MAC frame are indicated. The FCH band indicating the allocation information of the FCH band and the SCH band of the third MAC frame is an FCH band used with a radio terminal to be allocated.

[Third Embodiment]
In the third embodiment, the base station 1 determines an allocation channel in the allocation information using the traffic distribution of FIG. Here, when the base station 1 selects a channel for data transmission, the base station 1 assigns a bandwidth amount corresponding to the traffic distribution.
The operation of the base station 1 in the third method will be described using the flowchart of FIG. Here, description will be made assuming that the base station 1 measures and stores the data amount of the wireless terminal 2 for each assigned frame with respect to each wireless terminal 2 before the operation of the flowchart of FIG. 9. That is, description will be made assuming that the received data amount storage unit 103 stores the allocation frame number and the data amount in association with each other as a table (reception data amount table).

First, the occurrence probability calculation unit 104 detects whether or not the stored number of measurements in the allocation period is greater than or equal to a specified value N (step S301).
When the detection result in step S301 is that the number of measurements is smaller than the specified value N, the occurrence probability calculation unit 104 sets the allocated channel as the LCH for data transmission, sets the band determined by the negotiation before the start of communication as the allocated band, Conversion to the number of LCHs (step S302) and the process ends.
In step S302, LCH is selected as the allocation channel, but SCH for bandwidth request may be selected. That is, in step S302, either channel may be selected.

On the other hand, if the detection result in step S301 is that the number of measurements is equal to or greater than the specified value N, the occurrence probability storage unit 105 creates a measurement traffic distribution from the latest N measurement values and calculates the occurrence probability of each data amount. (Step S303).
Similar to the first embodiment, in this method, the allocation band candidate C _i (i = 1,..., M) is determined in advance from the range of the measurement data amount (D _i ). The allocation band candidate is not particularly limited except that it is selected from the range of the data amount of the measurement traffic distribution. Here, the bandwidth allocation candidate is the measurement data amount, and the allocation bandwidth candidate C _i = D _i (i = 1,..., 8).

Next, the expected throughput value calculation unit 106 calculates an expected throughput value when the allocated bandwidth candidate is applied (step S304). Note that the expected throughput value E _{thr_LCH} (C _i ) of the allocation band candidate C _i (i = 1,..., 8) is calculated by the equation (1) described in the first embodiment.
Next, the expected throughput calculation unit 106 _selects the maximum expected throughput value E _{MAX_thr_LCH} among the expected throughput values E _{thr_LCH} (C _i ) of all allocation band candidates (step S305).

Next, the throughput expected value calculation unit 106 calculates the throughput expected value E _{thr_SCH} at the time of channel allocation for bandwidth request using the equation (3) described in the second embodiment (step S306).
Next, the throughput expectation value selection unit 107 _{compares the} maximum expected throughput value E _{MAX_thr_LCH} with the expected throughput value E _{thr_SCH} at the time of bandwidth request channel allocation (step S307), and _selects a channel that can obtain high throughput. It selects as an allocation channel (step S308, S309).

In the comparison in step 307, if the expected throughput value E _{thr_SCH} at the time of bandwidth request channel allocation is higher, the expected throughput value selection unit 107 sets the allocated bandwidth as the allocated bandwidth of the SCH (step S308).
On the other hand, if the maximum expected throughput value E _{MAX_thr_LCH} is higher in the comparison in step 307, the expected throughput value selection unit 107 assigns the allocated bandwidth candidate C _i that becomes the maximum expected throughput value E _{MAX_thr_LCH} to the allocated bandwidth. And converted into the number of LCHs (step S309).
In the next allocation frame, the setting unit 108 allocates the allocation channel and the allocation band determined by the expected throughput value selection unit 107 in this processing flow to the corresponding wireless terminal 2.

  In the first to third embodiments, the case where the channel length for transmission data is fixed has been described as an example. However, the present method is also applicable to the case where the channel length for data transmission is variable. In this case, conversion of the number of LCHs becomes unnecessary.

As described above, the features of the processing at the base station in the present invention are the following points.
First, a measurement traffic distribution is created for each wireless terminal, and allocation information is determined based on the distribution. Next, the expected throughput value is calculated, and allocation information (channel, bandwidth) is determined so that high throughput can be obtained.
In addition, this method can be realized only by the base station. That is, there is no need to change the wireless terminal.

There are the following two effects as the common effects of the first to third embodiments.
First, since the allocation information is determined based on the measurement traffic distribution for each wireless terminal, there is an effect that the wireless resource can be effectively used in consideration of the traffic fluctuation of the wireless terminal.
Secondly, since the allocation information is determined based on the measurement traffic distribution for each wireless terminal, there is an effect that negotiation between higher layers becomes unnecessary.

In addition, each of the above first to third embodiments has the following effects.
In the first embodiment, since the bandwidth amount that maximizes the expected throughput value is allocated based on the measurement traffic distribution, it is possible to cope with fluctuations in the data amount during the measurement period, and to improve the bandwidth utilization rate. effective.
In the second embodiment, a channel with a high expected throughput value is assigned based on the measurement traffic distribution, so that it is possible to cope with fluctuations in the amount of data during the measurement period and to improve the bandwidth utilization rate. .
In the third embodiment, channels and bands with high expected throughput values are assigned based on the measurement traffic distribution, so that it is possible to cope with fluctuations in the amount of data during the measurement period and to improve the bandwidth utilization rate. There is.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within a scope not departing from the gist of the present invention.

  The present invention is suitable for use in a base station of a wireless communication system.

It is a block diagram which shows the structure of the band control apparatus in the base station by one Embodiment of this invention. It is a table | surface which shows the data amount for every allocation frame by an example of this invention. FIG. 3 is a distribution diagram of measurement traffic in the table of FIG. 2. 4 is an occurrence probability table for each data amount in the measured traffic distribution diagram of FIG. 3. It is a flowchart figure in 1st Embodiment of this invention. It is a data transmission sequence diagram as an example at the time of LCH band allocation for data transmission. It is a flowchart figure in 2nd Embodiment of this invention. It is a data transmission sequence diagram as an example at the time of SCH bandwidth allocation for bandwidth request. It is a flowchart figure in the 3rd Embodiment of this invention. It is a block diagram which shows the MAC frame structure as an example. It is a sequence diagram which shows the procedure of the negotiation between a radio | wireless terminal and a base station.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base station 2 Wireless terminal 3 Wireless network 101 Transmission / reception part 102 Reception data amount measurement part 103 Reception data amount storage part 104 Generation probability calculation part 105 Generation probability storage part 106 Throughput expected value calculation part 107 Throughput expected value selection part 108 Setting part

Claims (6)

In a bandwidth allocation method in a base station of a wireless communication system in which a plurality of terminals share a wireless line for communication,
For each terminal, measure the amount of data transmitted from the terminal,
For the latest N times (N is an integer greater than or equal to 2) measurement results for the band allocation target terminal, calculate the data amount and its occurrence probability,
Set multiple allocation candidate bands in advance,
For each of the allocation candidate bands, calculate the expected throughput value from the total amount of bandwidth required to complete transmission when the data amount, the occurrence probability, and the allocation candidate band are applied,
Determining an allocation candidate band that maximizes the calculated expected throughput value as allocation information in a next period of the band allocation target terminal;
A bandwidth allocation method characterized by the above. In a bandwidth allocation method in a base station of a wireless communication system in which a plurality of terminals share a wireless line for communication,
For each terminal, measure the amount of data transmitted from the terminal,
For the latest N times (N is an integer greater than or equal to 2) measurement results for the band allocation target terminal, calculate the data amount and its occurrence probability,
From the total amount of bandwidth required to complete transmission when adapting the allocation amount determined by the amount of data, the occurrence probability, and negotiation, calculate the expected throughput value at the time of channel allocation for data transmission,
When using the data amount, the occurrence probability, and the bandwidth request channel, from the total bandwidth required to complete transmission of the data amount, calculate the expected throughput value when allocating the bandwidth request channel,
The calculated throughput expected value at the time of channel allocation for data transmission is compared with the expected throughput value at the time of channel allocation for bandwidth request, and a channel for which a high expected throughput value is obtained is the next period of the band allocation target terminal. Determine as allocation information in
A bandwidth allocation method characterized by the above. In comparing the calculated throughput expected value at the time of channel allocation for data transmission and the expected throughput value at the time of channel allocation for bandwidth request,
If the calculated throughput request channel throughput expectation value at the time of channel allocation is higher, the bandwidth request channel bandwidth is set as allocation information in the next period of the bandwidth allocation target terminal,
When the calculated throughput expected value at the time of channel assignment for data transmission is higher, the assigned bandwidth determined by the negotiation is assigned information in the next period of the bandwidth assignment target terminal,
The bandwidth allocation method according to claim 2, wherein: In a bandwidth allocation method in a base station of a wireless communication system in which a plurality of terminals share a wireless line for communication,
For each terminal, measure the amount of data transmitted from the terminal,
For the latest N times (N is an integer greater than or equal to 2) measurement results for the band allocation target terminal, calculate the data amount and its occurrence probability,
Set multiple allocation candidate bands in advance,
For each of the allocation candidate bands, calculate the expected throughput value from the total amount of bandwidth required to complete transmission when the data amount, the occurrence probability, and the allocation candidate band are applied,
Select the maximum expected throughput value from the calculated expected throughput values as the maximum expected throughput value,
When using the data amount, the occurrence probability, and the bandwidth request channel, from the total bandwidth required to complete transmission of the data amount, calculate the expected throughput value when allocating the bandwidth request channel,
The selected maximum throughput expectation value is compared with the calculated throughput expectation value at the time of channel allocation for bandwidth request, and a channel from which a high throughput expectation value is obtained is assigned information in the next cycle of the band allocation target terminal decide,
A bandwidth allocation method characterized by the above. In comparison between the selected maximum expected throughput value and the expected throughput value at the time of channel allocation for the calculated bandwidth request,
If the calculated throughput request channel throughput expectation value at the time of channel allocation is higher, the bandwidth request channel bandwidth is set as allocation information in the next period of the bandwidth allocation target terminal,
If the selected maximum throughput expectation value is higher, the allocation candidate band that becomes the maximum throughput expectation value is assigned information in the next period of the band allocation target terminal,
The bandwidth allocation method according to claim 4, wherein: Determining the allocation candidate band based on the measured data amount;
5. The bandwidth allocation method according to claim 1 or 4, wherein:

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