JP5106316B2 - Wireless communication method, wireless communication system, and base station - Google Patents

Description

  The present invention relates to a wireless communication method, a wireless communication system, and a base station between a wireless base station that transmits and receives data through wireless communication connection and a plurality of wireless terminals.

  In recent years, ubiquitous networks using short-range wireless communication systems such as wireless tags, Bluetooth, and Zigbee have begun to spread in fields centered on equipment control, transportation, distribution, environmental conservation, food / agriculture, earthquake monitoring, medical welfare, etc. Yes. In the future, with the development of applications and services, the number of users and terminals of this network is expected to increase. Therefore, a wide area ubiquitous network that can provide various applications and services to a larger number of users and terminals and can expand the service area has attracted attention.

  FIG. 5 is a block diagram showing a schematic configuration of a wide area ubiquitous network. In the figure, a wide area ubiquitous network includes a server group 1 that collects data and provides various services, a wired network 2 that is a fixed network to which the server group 1 is connected, and a connection to the wired network 2. A plurality of base stations 3 and a plurality of wireless terminals 4 scattered in a wide area. FIG. 5 shows only one base station 3, and the base station 3 directly accommodates radio terminals 4-1, 4-2,..., 4-N as a plurality of radio terminals 4. Has been.

  The wireless terminals 4 in the wide-area ubiquitous network are mainly low-power consumption / low-function terminals that are battery-powered and have minimum functions such as data measurement and measurement data transmission. For this reason, the traffic from the wireless terminal 4 is characterized by (1) a small amount of data and (2) a relatively long transmission interval. Since there are a large number of such wireless terminals 4 under the control of one base station 3, there is a lot of uplink traffic as traffic characteristics, and the total traffic tends to increase. Furthermore, since the purpose of the wide-area ubiquitous network is to collect data from as many wireless terminals 4 as possible, it is necessary to efficiently accommodate as many wireless terminals 4 as possible in one base station 3. Therefore, the wide area ubiquitous network requires a MAC (Medium Access Control) protocol that can realize a high throughput and a low transmission delay time while efficiently accommodating many low-function wireless terminals 4 in one base station 3. The

  As a MAC protocol that satisfies the above requirements, a dynamic slot assignment (DSA) method, which is one of centralized control methods with high resource utilization efficiency, is known. In the dynamic slot allocation, a base station dynamically allocates a band (slot) according to a request from a wireless terminal.

FIG. 6 is a conceptual diagram illustrating an example of a MAC frame in TDMA-TDD (Time Division Multiple Access-Time Division Duplex). The MAC frame has a fixed length (fixed time), and is divided into a downlink and an uplink. The downlink is a broadcast section and a demand assignment section, and the uplink is a demand assignment (DA) section and a random access ( RA) section. The demand assignment section is a bandwidth allocation region for each wireless terminal or wireless link, and is an area that can be accessed without contention. On the other hand, the random access section is an area used by a plurality of wireless terminals, is a contention-based access area, and includes a plurality of Rch slots.
In order to transmit / receive data, control information, etc., Bch (Broadcast control channel), Fch (Frame control channel), RFch (Random access Feedback channel), Cch (Control channel: control channel), Dch (Data channel: data channel), and Rch (Random access channel) channels are used. Bch informs the radio terminal of the attributes of the base station (base station ID, frame number, etc.), and Fch is for each radio terminal or radio in the demand assignment section in which slot allocation is performed in units of radio terminals or radio links. In order to notify information on bandwidth allocation for each link (for example, ID, allocation position, allocation amount, etc. that can identify a wireless terminal or a wireless link to which a bandwidth is allocated), RFch uses random access information (random access of the previous frame). As a result, it is used to notify the random access start position and the number of slots in this frame). Cch is used for transmitting / receiving user data and control information for each wireless terminal or each wireless link, such as bandwidth request (Resource Request: RREQ) and ARQ (Automatic Repeat Request). Rch has a fixed length and is a channel for random access, and is used for a radio terminal to transmit the RREQ to the radio link.

As the dynamic slot allocation (DSA) method, there is a method in which a wireless terminal uses random access to make a bandwidth request to a base station. The random access method is widely applied as a dynamic slot allocation method because it can flexibly and efficiently accommodate non-periodic data generated in a burst manner.
FIG. 7 is a sequence diagram illustrating an example of an uplink data transmission sequence using a random access method according to the related art. In the illustrated example, the base station 3 transmits Bch, Fch, and RFch in order from the beginning of the MAC frame. The radio terminal 4 under the base station 3 can know the start position of random access and the number of Rch slots in the frame by receiving the RFch.

When transmitting data, the wireless terminal 4 transmits an RREQ including an ID for specifying the wireless terminal or the wireless link by Rch in order to request a band for transmission data. At this time, the wireless terminal 4 autonomously determines a back-off time, which is a transmission standby time based on the exponential back-off algorithm, that is, the number of Rchs to wait, in order to avoid collision with other wireless terminals. Here, the start of the back-off time is the start of back-off control. When the back-off time is completed, the wireless terminal 4 transmits the RREQ in the Rch slot immediately after completion of standby. If this Rch collides with an Rch from another wireless terminal, the wireless terminal 4 retransmits the RREQ by applying the Exponential backoff algorithm. The determination as to whether retransmission is necessary is performed by the wireless terminal 4 receiving the RFch of the next frame and referring to the random access result in the RFch. When the base station 3 can correctly receive the RREQ, the base station 3 notifies the ID for identifying the wireless terminal or the radio link that has successfully received the RREQ by the RFch of the next frame, and assigns the Dch corresponding to the bandwidth request value from the RREQ. Further, in the next frame to which the Dch is assigned, an ARQ Cch for transmitting an arrival confirmation for the Dch to the wireless terminal 4 is assigned.
Development of 5 GHz band advanced wireless access (AWA) system -MAC / DCL function-, 2000, IEICE Society Conference, B-5-39, pp. 327

However, in the uplink data transmission method described above, in particular, when there are a large number of wireless terminals 4-1, 4-2,..., 4-N under the base station 3 as in the wide area ubiquitous network, At the time of RREQ transmission to the random access section, there is a problem that access to the random access section increases and overhead due to Rch collision increases.
This overhead is a transmission standby time based on the exponential back-off algorithm, and is a factor that degrades transmission characteristics.
Therefore, in the above-described uplink data transmission method, since transmission characteristics greatly depend on the traffic situation in the random access section, it is necessary to control random access to guarantee the transmission delay time.
Here, traffic requiring transmission delay time is set as a priority class, and traffic not requiring transmission delay time is set as a non-priority class. As a method for controlling random access, a method for realizing priority control by setting an initial back off window (IBW) size, which is an access parameter of a random access section, to a value smaller than that of a non-priority class ( For example, IEEE 802.11e). However, this priority control has a problem that it is difficult to guarantee the delay time because the control parameter is fixed for each service class and the traffic situation is not considered at all.

  The present invention has been made in view of such circumstances, and its purpose is to provide a wireless communication method, a wireless communication system, and a wireless communication method for guaranteeing a transmission delay time of priority traffic in priority control of communication on a random access basis. And to provide a base station.

In order to solve the above problem, a radio communication method according to the present invention includes a plurality of terminal stations connected to a base station by a common radio channel, and the base station has a bandwidth for uplink communication in a radio frame in the radio channel. The allocated bandwidth is managed as a demand assignment section, the remaining bandwidth is managed as a random access section, and the bandwidth for requesting uplink allocation from the terminal station received in the random access section is the requested bandwidth for uplink communication. the assignment to the demand assignment period, receives the transmission data transmitted in the band of the allocated the demand assignment period from the terminal station, the terminal station, if the transmit data is generated, the band allocation request signal the random transmit an access interval, the transmission delay time based on required value which is required as the data transmission time from the terminal station In the wireless communication method for transmitting the transmission data in the demand assignment section, the measurement section measurement unit of the base station measures a measurement time based on a predetermined measurement section, the request time calculation unit of the base station, A request time corresponding to the measurement interval is calculated based on the request value of the transmission data, and an average value calculation unit of the base station performs average measurement in the measurement interval and the average value calculation interval of the request time, respectively. When the random access area length calculation unit of the base station detects a scheduling frame in the random access section, the average allocated random access area length in a scheduling period composed of a plurality of frames is calculated. Calculate the average measurement time, the average request time, and the average allocated random access area length. The random access area length in the scheduling period is determined, and the random access area length allocation unit of the base station determines the allocated random access area length in units of frames based on the random access area length. To do.

  In the radio communication method according to the present invention, the base station compares a maximum value and a minimum value based on an occupation rate of the random access section in the radio frame with the allocated random access area length in the frame unit. When the allocated random access area length in the frame unit is larger than the maximum value, the maximum value is changed to the allocated random access area length in the frame unit, and the determined allocation in the frame unit is determined. When the random access area length is smaller than the minimum value, the minimum value is changed to the allocated random access area length in the frame unit.

  Further, in the wireless communication method according to the present invention, when the base station determines the random access area length in the scheduling period, “(the average measurement time / the average required time) × the average random access area length” The random access area length in the scheduling period is determined according to the following.

  Further, the wireless communication method according to the present invention is such that, when the base station determines the random access area length in the scheduling period, the average random access area length is set when the average measurement time is larger than a predetermined upper limit threshold. When the average measurement time is smaller than a predetermined lower threshold, the average random access area length is halved to determine the random access area length in the scheduling period. The random access area length is determined.

  In the wireless communication method according to the present invention, when the base station determines the random access area length in the scheduling period, the wireless communication method is smaller than twice the average allocated random access area length in the expected scheduling period. When a predetermined fixed value, which is a value, is set, and the average measurement time is less than or equal to the upper limit threshold and greater than the average request time, the scheduling value is obtained by adding the fixed value to the average allocated random access area length The random access area length corresponding to a cycle is determined, and when the average measurement time is equal to or less than the average request time and larger than the lower limit threshold, the average assigned random access area length is subtracted the fixed value. The random access area length corresponding to the scheduling period is determined And wherein the door.

  The radio communication method according to the present invention is characterized in that the base station measures the time from when data is generated at the terminal station until the transmission data is received as the measurement time.

  The radio communication method according to the present invention is characterized in that the base station measures, as the measurement time, a time from when data is generated in the terminal station until reception of the band allocation request signal. To do.

  In the radio communication method according to the present invention, the base station measures the time from when the first back-off control is started at the terminal station until the band allocation request signal is received as the measurement time. It is characterized by that.

In the wireless communication system according to the present invention, a plurality of terminal stations are connected to a base station through a common wireless channel, and the base station is assigned a band among uplink communication bands in a radio frame in the wireless channel. For the bandwidth assignment request signal from the terminal station received in the random access section, the requested bandwidth for the uplink communication is assigned to the demand assignment section. assignment, receives transmission data transmitted in the band of the allocated the demand assignment period from the terminal station, the terminal station, if the transmit data is generated, the band allocation request signal in the random access period transmitted, the transmission data in transmission delay time based on required value which is required as the data transmission time from the terminal station A wireless communication system that transmits in the demand assignment section, the measurement section measurement unit of the base station that measures a measurement time based on a predetermined measurement section, and a request time corresponding to the measurement section, the transmission time of the transmission data A request time calculation unit of the base station that calculates based on a request value, and an average value calculation unit of the base station that calculates an average measurement time and an average request time, respectively, in the measurement interval and the average value calculation interval of the request time And, when a scheduling frame in the random access section is detected, an average allocated random access area length in a scheduling period composed of a plurality of frames is calculated, and the average measurement time, the average request time, and the average random access area length Based on the random access area in the scheduling period A base station random access area length calculation unit for determining the base station, and a base station random access area length allocation unit for determining the allocation random access area length in frame units based on the random access area length. It is characterized by.

Further, the base station according to the present invention is connected to a plurality of terminal stations through a common radio channel, and the allocated band among the uplink communication bands in the radio frame in the radio channel is used as the demand assign section and the remaining bands are used. In response to a bandwidth allocation request signal from the terminal station that is managed as a random access section and received in the random access section, the requested uplink communication band is allocated to the demand assignment section, and the allocated demand assignment A base station that receives transmission data transmitted from the terminal station in a band of a section, the measurement section measurement unit of the base station that measures a measurement time based on a predetermined measurement section, and a request corresponding to the measurement section said base of time, of the transmission data, is calculated on the basis of the required value which is required as the data transmission time from the terminal station A request time calculation unit, an average value calculation unit of the base station that calculates an average measurement time and an average request time in the measurement interval and an average value calculation interval of the request time, respectively, and a scheduling frame of the random access interval If detected, an average allocated random access area length in a scheduling period composed of a plurality of frames is calculated, and a random access area in the scheduling period is calculated based on the average measurement time, the average request time, and the average random access area length. A random access area length calculation unit for the base station that determines a length; and a random access area length allocation unit for the base station that determines the allocated random access area length in units of frames based on the random access area length. It is characterized by that.

According to the present invention, the random access area length (that is, the number of Rch slots) can be dynamically controlled according to the measurement time and request time of the priority class, and transmission of the priority class in which the request value is set. Delay time can be guaranteed.
Furthermore, according to the present invention, since there is a random access area that is secured preferentially, the delay time characteristics of the non-priority class can be improved.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the radio communication system according to the embodiment of the present invention, in order to guarantee the average transmission delay time, the measurement interval is measured in the priority class, the request time corresponding to the measurement interval of the request value is calculated, and these average values are calculated. The random access area length, that is, the number of Rch slots (random access area length) is dynamically controlled according to the average measurement time and average request time. This is based on the time required for data transmission (average measurement time) and the time based on the required value requested as the average transmission delay time (average request time) in the priority class data transmission for which the average transmission delay time is required. ), The random access area length of RREQ, which is a band allocation request signal, is dynamically controlled to guarantee an average transmission delay time.

FIG. 1 is a block diagram showing a configuration of a wireless communication system according to an embodiment of the present invention. Note that portions corresponding to those in FIG. 6 are denoted by the same reference numerals and description thereof is omitted. In the wireless communication system according to the present invention, a plurality of service classes that provide different quality of service (QoS) are defined by the base station 3, and different conditions are set for each service class. The service class is an index for determining the QoS level for each service using wireless communication, and is determined by the average transmission delay time, throughput, delay fluctuation, packet error rate, etc. according to the type of traffic. Is done.
The base station 30 according to the present embodiment uses the average transmission delay time as a criterion for determining this QoS, and manages, for example, the service class 1 as a priority class and the service class 2 as a non-priority class. (Transmission delay time) is set to 10 seconds or less, and the non-priority class is processed as best effort.

The base station 30 is connected to a wireless terminal (terminal station) 4-1 to 4 -N (hereinafter, described as a wireless terminal 4 when described as a representative wireless terminal) through a common wireless line, and is wireless. Of the uplink communication bands in the radio frame on the line, the allocated band is managed as a demand assign section, and the remaining bands are managed as a random access section. The base station 30 allocates the requested uplink communication band to the demand assignment section in response to the band allocation request signal (RREQ) received from the wireless terminal 4 in the random access section, and the bandwidth of the allocated demand assignment section. The transmission data transmitted from the wireless terminal 4 is received.
The base station 30 manages the reception status of a signal (RREQ Rch, etc.) and transmission data (Dch, etc.) transmitted from the wireless terminal 4 for each service class. As shown in FIG. A calculation unit 310, an Rch number range determination unit 320, and an Rch allocation unit 330 are included. The base station 30 determines the Rch number in the measurement unit 300, the Rch number calculation unit 310, and the Rch number range determination unit 320, and preferentially secures a band corresponding to the Rch number in the Rch allocation unit 330, and in the MAC frame Announcement section, demand assignment section, and random section are allocated. The base station 30 schedules Rch for a plurality of frames (N frames) as a timing for calculating, determining, and securing the number of Rch. That is, the base station 30 detects an Rch scheduling frame set at an N frame interval, and executes Rch scheduling at the Rch scheduling period.

  The measurement unit 300 includes a measurement section measurement unit 31, a required time calculation unit 32, an Rch count unit 33, an average value calculation unit 34, and a storage unit 35.

  The measurement section measurement unit 31 measures the measurement time of a predetermined measurement section in the transmission of data transmitted from the wireless terminal 4 and stores the measurement time in the storage unit 35. The measurement interval is defined in the measurement interval measurement unit 31 with a predetermined event as a base point. For example, the data generation time at the wireless terminal 4, the start time of the back-off control at the wireless terminal 4, and the end of the back-off control. There are time points (that is, reception times of Rch (RREQ) at the base station 30), data reception points at the base station 30, and the like. The measurement section measurement unit 31 measures a measurement section defined using such an event. As the measurement interval, for example, (1) an interval from data generation at the wireless terminal 4 to data reception at the base station 30 (corresponding to transmission delay time), (2) data generation at the wireless terminal 4 to base station 30 There are sections until Rch (RREQ: band allocation request signal) reception at (3), (3) sections from the start of backoff control at the radio terminal 4 to Rch (RREQ) reception at the base station 30, and the like. In the present embodiment, the measurement section measurement unit 31 measures the measurement time of the measurement section defined as (1).

  The request time calculation unit 32 is a request time corresponding to the measurement section defined by the measurement section measurement unit 31 and is calculated based on a request value requested as a data transmission time from the wireless terminal 4. In the present embodiment, the request value is an average transmission delay time set for each service class, and is set to 10 seconds or less in the priority class. In addition, since the best effort processing is performed in the non-priority class, the required value is not set. Therefore, in the present embodiment, the request time and average request time are calculated by the base station 30, and the priority method to which the Rch is preferentially assigned is applied to the transmission data of the priority class.

  In addition, the calculation method prescribed | regulated according to the above-mentioned measurement area differs in request | requirement time, and in the measurement area of said (1), request | requirement time is a request value itself as above-mentioned. In the measurement section (2) above, the required time is obtained by subtracting the average Dch allocation time (the average of the time obtained by subtracting the RREQ reception time from the data reception time) from the request value. In the measurement section of (3) above, the required time is obtained by subtracting the average buffering time (the average value of the backoff control start time minus the data generation time) and the average Dch allocation time from the required value. It is.

  The Rch count unit 33 counts the number of Rchs allocated by the base station 30 in the average value calculation section M used by the average value calculation unit 34 to calculate the average value, and stores the counted Rch number in the storage unit 35. Remember.

  The average value calculation unit 34 calls the measurement time measured by the measurement section measurement unit 31 from the storage unit 35 and the request time calculated by the request time calculation unit 32, and calculates an average value of a predetermined length composed of a plurality of frames. In the section M, an average value of measurement time (average measurement time) and an average value of request time (average request time) are calculated.

  The storage unit 35 is calculated by the measurement time measured by the measurement section measurement unit 31, the request time calculated by the request time calculation unit 32, the number of Rch counted by the Rch count unit 33, and the average value calculation unit 34. The average measurement time and average request time are stored.

  The Rch number calculation unit 310 calculates the average allocation Rch number (average allocation random access area length) in the Rch scheduling period based on the past average measurement time, average request time, and Rch number stored in the storage unit 35. In the present embodiment, Rch number calculation section 310 calculates the average assigned Rch number by averaging the total number of Rch assigned within the average measurement time calculation period (average value calculation section M) in the Rch scheduling period. To do. That is, when detecting the Rch scheduling frame indicating the Rch scheduling period, the Rch number calculation unit 310 reads the counted Rch number for the average value calculation section M from the storage unit 35 and calculates the average assigned Rch number. Therefore, for example, when the Rch scheduling cycle N = 200 frames, the Rch number calculating unit 310 counts the Rch counts counted by the Rch counting unit 33 as an average value calculation interval M = 1000 frames for calculating the average measurement time. = 15000 is used to calculate the average assigned Rch number based on Equation 1 below.

つまり、平均割当Ｒｃｈ数は、１５０００／１０００×２００＝３０００となる。
なお、Ｒｃｈカウント部３３によりカウントされたＲｃｈ数には、残帯域によるＲｃｈの追加数も含まれるものとする。

That is, the average assigned Rch number is 15000/1000 × 200 = 3000.
Note that the number of Rchs counted by the Rch counting unit 33 includes the number of Rch additions due to the remaining bandwidth.

  The Rch number calculation unit 310 uses the calculated average allocated Rch number and the average measurement time and average request time read from the storage unit 35 to calculate the Rch number (random access area length) in the scheduling period based on the following equation 2. calculate.

なお、Ｒｃｈ数算出部３１０は、Ｒｃｈスケジューリングフレームを検出する方法として、例えば、次フレームのフレーム番号とＲｃｈスケジューリング周期のフレーム数（Ｎ）の剰余をとり、所定の値（例えば０：余りなし）と一致することでＲｃｈスケジューリングフレームを検出する方法を利用している。

As a method for detecting the Rch scheduling frame, the Rch number calculation unit 310 takes, for example, the remainder of the frame number of the next frame and the number of frames (N) of the Rch scheduling period, and a predetermined value (for example, 0: no remainder). Is used to detect the Rch scheduling frame.

  The Rch number range determination unit 320 determines the Rch number so as to be within the allocation range based on the Rch number calculated by the Rch number calculation unit 310 and stores the Rch number in the storage unit 35. In the present embodiment, as the threshold value for determining the Rch allocation range, a maximum value based on the upper limit value of the Rch occupation ratio in one frame and a minimum value based on the lower limit value are set in advance. The Rch number range determination unit 320 compares the Rch number calculated by the Rch number calculation unit 310 with a preset maximum value and minimum value, thereby determining the number of Rchs that fall within the allocation range. That is, when the Rch number calculated by the Rch number calculation unit 310 is larger than the maximum value, the Rch number range determination unit 320 changes the Rch number to the maximum value, and the Rch number calculation unit 310 calculates the minimum Rch number. If it is smaller than the value, the Rch number is changed to the minimum value.

  The Rch allocation unit 330 calculates the allocation Rch number (allocation random access area length) in units of frames based on the Rch number determined by the Rch number range determination unit 320, and preferentially secures the corresponding slot number. In the present embodiment, Rch assigning section 330 assigns each frame evenly based on the number of Rch determined by Rch number range determining section 320, and when the assignment cannot be made evenly (when a fraction is generated), The Rch number corresponding to the fraction is allocated one by one from the frame in order. For example, when the Rch scheduling period is N = 10 frames and the number of Rchs determined by the Rch number range determination unit 320 is 102, 11 Rchs for the first two frames and for the remaining frames Assigns 10 Rch. The Rch allocation unit 330 allocates a random section in the MAC frame based on the number of Rchs secured with priority. The Rch allocating unit 330 performs additional allocation of Rch when there is a remaining bandwidth at the time of allocation.

When transmission data is generated, the wireless terminal 4 starts back-off control, and transmits RREQ Rch as a band allocation request signal in a random access section. When the wireless terminal 4 succeeds in transmitting the RREQ Rch within the random access section, the wireless terminal 4 transmits the transmission data in the demand assignment section allocated from the base station 30.
The wireless terminal 4 transmits the start time of backoff control together with RREQ together with the data to which the generation time of transmission data is transmitted to the base station 30. Based on this information, the measurement section measuring unit 31 can measure the measurement section. For example, the wireless terminal 4 can use a frame number as time information.

  In the present embodiment, the calculation method of the average measurement time in the base station 30 is (A) a method of measuring the average measurement time for data arriving within an average section divided by a predetermined time (frame) unit. Although the present invention is not limited to this, for example, (B) a method for measuring an average measurement time for each number of received data, (C) a sliding window is provided for the method (A) or (B). A method of calculating an average measurement time for the data in this window can be used. The average request time can also be calculated in the same manner as described above.

  FIG. 2 is a Siemens diagram showing an example of an uplink data transmission sequence using a random access method in the wireless communication system of the present embodiment. As shown in FIG. 2, the base station 30 transmits Bch, Fch, and RFch in order from the beginning of the MAC frame. By receiving the RFch, the wireless terminal 4 under the base station 30 can know the random access start position and the number of slots in the frame.

When transmitting data due to data generation, the wireless terminal 4 transmits RREQ by Rch to request an area length for transmission data. At this time, when the back-off control is performed, the wireless terminal 4 transmits the RREQ in the corresponding slot of the Rch when the back-off time that is the transmission standby time is completed. Although not shown, if this Rch collides with an Rch from another wireless terminal, the wireless terminal 4 retransmits the RREQ. This determination as to whether or not retransmission is necessary is made based on whether or not the wireless terminal 4 has received the RFch of the next frame.
When the RREQ is correctly received, the base station 30 notifies the success of the RREQ reception using the RFch of the next frame, and allocates a Dch corresponding to the bandwidth request value from the RREQ. Further, in the next frame to which the Dch is assigned, an ARQ Cch for transmitting an arrival confirmation for the Dch to the wireless terminal 4 is assigned.
In such a sequence, the measurement intervals (1) to (3) described above are distinguished as shown in the figure in the event of data generation, backoff control start, RREQ reception, and data reception of the base station 30. .

Next, a measurement flow at the base station 30 will be described with reference to FIG.
As shown in FIG. 3, the measurement section measurement unit 31 measures the measurement time of a predetermined measurement section and stores it in the storage unit 35 (S1). The request time calculation unit 32 calculates a request time corresponding to the measurement section measured by the measurement section measurement unit 31, and stores it in the storage unit 35 (S2). The Rch count unit 33 counts the number of Rchs allocated by the base station 30 in the frame corresponding to the measurement interval measured by the measurement interval measurement unit 31 (average value calculation interval M), and stores the counted Rch number. Store in the unit 35 (S3). The average value calculation unit 34 is an average measurement time that is an average value of measurement times measured by the measurement section measurement unit 31 in the predetermined average value frame M, and an average value of the request times calculated by the request time calculation unit 32. Is calculated and stored in the storage unit 35 (S4).

Next, the Rch allocation processing flow in the base station 30 will be described using FIG.
The Rch number calculation unit 310 detects whether or not the next frame is an Rch scheduling frame (S5), and if the next frame is an Rch scheduling frame (S5-YES), the average stored in the storage unit 35 The past average measurement time, average request time, and Rch number for the value calculation section M frames are read, and the average assigned Rch number in the Rch scheduling period N is calculated (S6). The Rch number calculation unit 310 calculates the Rch number based on the above equation 2 using the calculated average allocated Rch number, the average measurement time and the average request time for the average value calculation section M frames read from the storage unit 35. (S7).
The Rch number calculation unit 310 outputs the calculated Rch number to the Rch number range determination unit 320. The Rch number range determination unit 320 compares the input Rch number with a preset maximum value (S8), and if the Rch number is equal to or less than the maximum value (S8-NO), the Rch number range is determined in advance. Further comparison is made with the set minimum value (S9). When the Rch number is equal to or greater than the minimum value (S9-NO), the Rch number range determination unit 320 determines the input Rch number as it is as the Rch number and stores it in the storage unit 35.
The Rch allocating unit 330 reads the Rch number determined by the Rch number range determining unit 320 from the storage unit 35, calculates the allocated Rch number for each frame based on the Rch number, and preferentially secures the corresponding band. Rch allocation processing is executed (S10).

On the other hand, when the Rch number is larger than the maximum value in step S8 (S8-YES), the Rch number range determination unit 320 determines the preset maximum value as the Rch number and stores it in the storage unit 35. In step S10, the Rch allocation unit 330 reads the determined Rch number from the storage unit 35, and executes the Rch allocation process based on the read Rch number.
In step S9, when the Rch number is smaller than the minimum value (S9-YES), the Rch number range determination unit 320 determines the preset minimum value as the Rch number and stores it in the storage unit 35. In step S10, the Rch allocation unit 330 reads the determined Rch number from the storage unit 35, and executes the Rch allocation process based on the read Rch number.
Furthermore, when the next frame is not an Rch scheduling frame in step S5 (S5-NO), the process proceeds to step S10, and the number of Rchs already determined in the Rch scheduling is read from the storage unit 35. Based on the read Rch number, the Rch allocating unit 330 calculates the allocated Rch number for each frame in the subsequent frames according to the Rch allocation processing method as described above, and preferentially secures the corresponding band.

In the scheduling of the next frame, the base station 30 allocates bandwidths for the broadcast section and the demand assignment section according to the number of Rchs secured as described above. Thereby, the base station 30 can preferentially secure the bandwidth of the Rch number (random access section) of the priority class for which the request value is set.
In addition, the base station 30 performs additional allocation of Rch when there is a remaining band when allocating Rch, broadcast section, and demand assignment section.
Further, the base station 30 may be configured to use the average measurement time, the average required time, and the Rch number measured using FIG. 3 when calculating the average allocated Rch number in step S6. It may be configured to use what is measured by and stored in the storage unit 35.
Furthermore, the measurement flow at the base station 30 described with reference to FIG. 3 does not limit the order of steps S1 to S4, and the measurement unit 300 generates the average measurement time, the average request time, and the Rch number. It is an example explaining the method for doing.

  Next, different examples of the Rch number calculation process of the Rch number calculation unit 310 will be described with reference to FIG. This Rch number calculation process can be used in the radio communication system according to the present invention, instead of the Rch number calculation process described using Equation 2 and step S7 shown in FIG. At this time, the Rch number calculation unit 310 stores two preset threshold values (an upper threshold value and a lower threshold value). Note that these threshold values are set in advance with an average request time calculated by the average value calculation unit 34 under a magnitude relationship such that upper limit threshold> average request time> lower limit threshold.

  As illustrated in FIG. 5, the Rch number calculation unit 310 compares the average measurement time read from the storage unit 35 with the upper threshold (S21), and when the average measurement time is equal to or lower than the upper threshold (S21-NO), the average The measurement time and the average required time are further compared (S22). When the average measurement time is equal to or less than the average required time (S22-NO), the Rch number calculation unit 310 further compares the average measurement time with the lower limit threshold value (S23). A value (average assigned Rch number / 2) obtained by dividing the average assigned Rch number (see step S6 in FIG. 3) by 2 is determined as the Rch number and stored in the storage unit 35 (S24).

On the other hand, when the average measurement time is larger than the upper limit threshold value in step S21 (S21-YES), Rch number calculation unit 310 multiplies the previously calculated average allocation Rch number by 2 (average allocation Rch number × 2). The Rch number is determined and stored in the storage unit 35 (S25).
In step 22, when the average measurement time is larger than the average required time (S22-YES), the Rch number calculation unit 310 adds a predetermined fixed value α to the previously calculated average allocation Rch number (average allocation Rch). (Number + α) is determined as the number of Rch and stored in the storage unit 35 (S26).
Furthermore, when the average measurement time is larger than the lower limit threshold in step 23 (S23-YES), the Rch number calculation unit 310 is a value obtained by reducing the production of a predetermined fixed value α to the previously calculated average allocation Rch number (average allocation Rch number). -Α) is determined as the number of Rch and stored in the storage unit 35 (S27).

That is, the Rch number calculation unit 310 compares the average measurement time with the upper limit threshold value, the average request time, or the lower limit threshold value, and sets the Rch number as the average assigned Rch number × 2 when the average measurement time is larger than the upper limit threshold value. If the average measurement time is less than or equal to the upper limit threshold and greater than the average required time, the number of Rch is the average assigned Rch number + α, and if the average measurement time is less than or equal to the average request time and greater than the lower limit threshold, the number of Rch is averaged The number of assigned Rch is −α, and when the average measurement time is equal to or lower than the lower limit threshold, the number of Rch is set to the average assigned Rch number / 2.
The fixed value α is determined in advance within a range that is smaller than twice the assumed average assigned Rch number (for example, the maximum value described in step S8 in FIG. 3), and the Rch number calculating unit 310 Is remembered.

Note that the radio communication system according to the present invention can be applied even when the random access section area is different for each service class. That is, when two priority classes and non-priority classes are set and the random access sections are different, the random access section of the priority class is preferentially allocated using the method of the present invention, which occurs during scheduling. The remaining bandwidth can be allocated to the random access section area of the non-priority class.
In the present embodiment, a configuration in which only one priority class is set has been described. However, the present invention is not limited to this, and a plurality of service classes with different request values, for example, request values (average) Service class 1 (priority class) with a transmission delay time) of 10 seconds or less, service class 2 (priority class) with a request value of 10 seconds to 20 seconds or less, and service class 3 (non-classification) for performing best effort processing The priority class may be set. In this case, since the radio communication system according to the present invention can control the random access area length for each priority class, the number of assigned Rch can be calculated for each priority class, and the corresponding band can be preferentially secured. it can.

It is a block diagram which shows the structure of the radio | wireless communications system concerning this Embodiment. It is a Siemens figure which shows an example of the data transmission sequence of the uplink using the random access method in the radio | wireless communications system concerning this Embodiment. It is a flowchart explaining an example of the measurement flow in the base station concerning this Embodiment. It is a flowchart explaining an example of the Rch allocation processing flow in the base station concerning this Embodiment. It is a flowchart explaining an example of the Rch number calculation process concerning this Embodiment. It is a block diagram which shows the schematic structure of a wide area ubiquitous network. It is a conceptual diagram which shows an example of the MAC frame in TDMA-TDD. It is a sequence diagram which shows an example of the data transmission sequence of the uplink using a random access method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Server group 2 Wired network 3 Base station 4 Wireless terminal 30 Base station 31 Measurement section measurement part 32 Request time calculation part 33 Rch count part 34 Average value calculation part 35 Storage part 300 Measurement part 310 Rch number calculation part 320 Rch number range determination Section 330 Rch allocation section

Claims (10)

Multiple terminal stations are connected to the base station via a common radio link,
The base station manages the allocated band among the uplink communication bands in the radio frame in the radio channel as a demand assignment section and the remaining band as a random access section, and receives from the terminal station received in the random access section. In response to the bandwidth allocation request signal, the requested uplink communication band is allocated to the demand assignment section, and the transmission data transmitted from the terminal station in the allocated bandwidth of the demand assignment section is received,
Said terminal station, transmit when data is generated, and transmits the band allocation request signal in the random access period, the transmission data in transmission delay time based on required value which is required as the data transmission time from the terminal station In the wireless communication method for transmitting in the demand assignment section,
The measurement section measurement unit of the base station is
Measure the measurement time based on the predetermined measurement interval,
The required time calculation unit of the base station,
Calculating a required time corresponding to the measurement interval based on the required value of the transmission data;
The average value calculation unit of the base station,
In the measurement interval and the average value calculation interval of the required time, respectively, the average measurement time and the average required time are calculated,
The random access area length calculation unit of the base station,
When a scheduling frame in the random access section is detected, an average allocated random access area length in a scheduling period composed of a plurality of frames is calculated, and the average measurement time, the average request time, and the average allocated random access area length are calculated. And determining a random access area length in the scheduling period,
The random access area length allocation unit of the base station,
A wireless communication method, comprising: determining an assigned random access area length in a frame unit based on the random access area length. The base station
Comparing the maximum and minimum values based on the occupancy rate of the random access section in the radio frame and the allocated random access area length in the frame unit,
When the allocated random access area length in the frame unit is larger than the maximum value, the maximum value is changed to the allocated random access area length in the frame unit,
2. The minimum value is changed to the assigned random access area length in the frame unit when the assigned random access area length in the frame unit is smaller than the minimum value. The wireless communication method described. The base station
When determining the random access area length in the scheduling period,
3. The radio communication method according to claim 1, wherein the random access area length in the scheduling period is determined according to (the average measurement time / the average required time) × the average random access area length. The base station
When determining the random access area length in the scheduling period,
If the average measurement time is greater than a predetermined upper threshold, the average random access area length doubled is determined as the random access area length in the scheduling period;
3. The random access area length in the scheduling period is determined by halving the average random access area length when the average measurement time is smaller than a predetermined lower threshold. The wireless communication method described. The base station
When determining the random access area length in the scheduling period,
A predetermined fixed value that is smaller than twice the average allocated random access area length in the assumed scheduling period is set;
When the average measurement time is equal to or less than the upper limit threshold and greater than the average request time, a value obtained by adding the fixed value to the average allocated random access area length is determined as the random access area length corresponding to the scheduling period. And
When the average measurement time is equal to or less than the average request time and greater than the lower limit threshold, a value obtained by subtracting the fixed value from the average allocated random access area length is determined as the random access area length corresponding to the scheduling period. The wireless communication method according to claim 4, wherein: The base station
The radio communication method according to claim 1, wherein a time from when data is generated in the terminal station to reception of the transmission data is measured as the measurement time. The base station
The wireless communication according to any one of claims 1 to 5, wherein as the measurement time, a time from when data is generated in the terminal station to reception of the band allocation request signal is measured. Method. The base station
6. The measurement time according to any one of claims 1 to 5, wherein a time from when the first back-off control is started in the terminal station until the band allocation request signal is received is measured. The wireless communication method described. Multiple terminal stations are connected to the base station via a common radio link,
The base station manages the allocated band among the uplink communication bands in the radio frame in the radio channel as a demand assignment section and the remaining band as a random access section, and receives from the terminal station received in the random access section. In response to the bandwidth allocation request signal, the requested uplink communication band is allocated to the demand assignment section, and the transmission data transmitted from the terminal station in the allocated bandwidth of the demand assignment section is received,
Said terminal station, transmit when data is generated, and transmits the band allocation request signal in the random access period, the transmission data in transmission delay time based on required value which is required as the data transmission time from the terminal station In a wireless communication system for transmitting in the demand assignment section,
A measurement interval measurement unit of the base station that measures a measurement time based on a predetermined measurement interval;
A request time calculation unit of the base station that calculates a request time corresponding to the measurement interval based on the request value of the transmission data;
An average value calculation unit of the base station for calculating an average measurement time and an average request time in the measurement interval and an average value calculation interval of the request time, respectively,
When a scheduling frame in the random access section is detected, an average allocated random access area length in a scheduling period composed of a plurality of frames is calculated, and based on the average measurement time, the average request time, and the average random access area length A random access area length calculation unit of the base station that determines a random access area length in the scheduling period;
A wireless communication system comprising: a random access area length allocation unit of the base station that determines the allocated random access area length in frame units based on the random access area length. Connected to multiple terminal stations via a common wireless line,
Of the uplink communication bands in the radio frame in the radio channel, the allocated band is managed as a demand assignment section, the remaining bands are managed as a random access section, and the band allocation request signal from the terminal station received in the random access section On the other hand, in the base station that receives the transmission data transmitted from the terminal station in the allocated bandwidth of the demand assignment section, assigning the requested uplink communication band to the demand assignment section,
A measurement interval measurement unit of the base station that measures a measurement time based on a predetermined measurement interval;
A request time calculation unit of the base station that calculates a request time corresponding to the measurement interval based on a request value of the transmission data requested as a data transmission time from the terminal station ;
An average value calculation unit of the base station for calculating an average measurement time and an average request time in the measurement interval and an average value calculation interval of the request time, respectively,
When a scheduling frame in the random access section is detected, an average allocated random access area length in a scheduling period composed of a plurality of frames is calculated, and based on the average measurement time, the average request time, and the average random access area length A random access area length calculation unit of the base station that determines a random access area length in the scheduling period;
A base station comprising: a random access area length allocation unit of the base station that determines the allocated random access area length in frame units based on the random access area length.

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