JP2012165301A - Radio base station device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio base station device capable of flexibly accommodating an increase in traffic or an increase in the number of radio relay stations or radio terminal stations and preventing degradation in transmission characteristic.SOLUTION: The radio base station device estimates both or either one of transmission delay time and throughput for both methods different in merits and demerits of transmission characteristic according to traffic characteristic, and selects the optimum system as an access method according to the traffic characteristic, based on the estimated result.

Description

  The present invention relates to a technique for performing communication between a wireless data receiving device (wireless base station) connected via a wireless line and a plurality of wireless data transmitting devices (wireless relay stations or wireless terminal stations). It is.

  An access method applied to packet transmission in a wireless access system used as an access system of a wired network includes a distributed control method in which each wireless terminal station individually determines a transmission timing and performs transmission, and a wireless base station includes all wireless terminals. It can be broadly divided into two systems, a centralized control system that manages the transmission timing of the stations.

  In the distributed control method, the configuration of the radio base station is simplified compared to the centralized control method. Further, since there is no need to control the radio terminal station from the radio base station, no control signal is required, and high band utilization efficiency can be realized. On the other hand, since each wireless terminal station individually determines the transmission timing, there is a possibility that transmission packets collide when packets are transmitted at a plurality of wireless terminal stations. Particularly in a congested state, transmission packet collisions frequently occur, and transmission characteristics deteriorate due to an increase in retransmission. Therefore, a collision avoidance algorithm is used in the distributed control method.

  In IEEE 802.11, random access, which is one of distributed control methods, is used as an access method, and an exponential back off algorithm is used as a collision avoidance algorithm. FIG. 1 shows a back-off operation in the collision avoidance algorithm used in IEEE 802.11. When a packet is transmitted using this algorithm, a random number between 0 and a specified value (window size) is calculated, and the transmission is delayed (backed off) by that value, and the packet is transmitted. The maximum random number for the first transmission is defined as the initial backoff window size. When packet transmission fails due to collision or the like, the window size is multiplied by x, the back-off time is calculated within that range, and the packet transmission is delayed by that value and retransmitted. The value that increases the window size (x above) is called the persistent factor (PF). If the packet transmission fails again, the window size is further multiplied by x, the back-off time is calculated, and the packet transmission is delayed by that value and retransmitted. In the exponential back off algorithm, this operation is repeated until the packet transmission is successful or the number of retransmissions reaches a preset maximum number of retransmissions.

IEEE Std 802.11-2007 (p.256-263)

  In the prior art (distributed control method), wireless terminal stations individually determine the transmission timing and perform transmission, and avoid collision of packets using the exponential back off algorithm, so there are many wireless terminal stations that generate less traffic In such a radio access system, good transmission characteristics can be realized. However, if the traffic added to the radio access system increases, the probability of transmission packet collisions increases. As a result, since the calculated back-off value increases due to an increase in retransmission, there is a problem that transmission characteristics deteriorate.

  On the other hand, in the centralized control method, since the radio base station manages the transmission timings of all radio terminal stations, there is no transmission packet collision. Therefore, in a situation where there is a lot of traffic added to the above-described wireless access system and the transmission characteristics deteriorate when the distributed control method is applied, the centralized control method is applied to avoid the collision of the transmission packets, thereby improving the transmission characteristics. There is a possibility of realization. However, since this method requires a control signal for each wireless terminal station, when there are a large number of wireless terminal stations, the bandwidth for the control signal increases, and a control signal (for example, a polling signal) for each wireless terminal station There is a problem that the allocation period becomes longer and the transmission characteristics deteriorate.

  Therefore, in order to solve the above problem, it is necessary to realize a radio access system that can flexibly cope with an increase in traffic or the number of radio relay stations and radio terminal stations and prevent deterioration of transmission characteristics. . An object of the present invention is to provide a radio base station apparatus that realizes the radio access system.

  In order to achieve the above object, the radio base station apparatus according to the present invention estimates the transmission delay time and / or the throughput for both systems having different transmission characteristics according to the traffic characteristics, Based on the estimation results, the optimum method is selected as the access method according to the traffic characteristics. Hereinafter, the wireless relay station and the wireless terminal station may be collectively referred to as a wireless station.

Specifically, the radio base station apparatus according to the present invention is:
A radio base station apparatus that adopts a random access method or a polling method as an access method and performs radio communication with a plurality of radio stations using radio frames,
The amount of traffic generated within a unit time is measured for each wireless station, and the amount of traffic generated within the unit time exceeds a predetermined reference value as a high traffic wireless station, and is generated within the unit time. A parameter measurement unit that calculates the number of the high traffic radio stations, the radio station having the traffic amount within the reference value as a low traffic radio station,
Based on the number of high traffic radio stations calculated by the parameter measurement unit and the number of polling signals that can be assigned in the radio frame, transmission delay time and throughput when a polling method is applied to the high traffic radio stations An estimation unit that estimates both or either of
Either or both of a state in which the transmission delay time when applying the polling method estimated by the estimation unit is smaller than a predetermined transmission delay time threshold and a state in which the throughput when applying the polling method is larger than a predetermined throughput threshold On the other hand, when a polling method is selected as an access method with the high traffic radio station, a state in which a transmission delay time when the polling method is applied is larger than a predetermined transmission delay time threshold value and when the polling method is applied. A random access method is selected as an access method with the high-traffic radio station when the throughput is lower or lower than a predetermined throughput threshold, and in either case, the access with the low-traffic radio station is selected. A method selection unit for selecting a random access method as an access method;
A communication unit that communicates with the wireless station using the access method selected by the method selection unit;
It is characterized by providing.

  This radio base station apparatus, for each high-traffic radio station, out of transmission delay time and / or throughput of random access that is one of distributed control methods and polling that is one of centralized control methods. The method that is presumed to be superior is selected as the access method.

  Therefore, the present invention can provide a radio base station apparatus that can flexibly cope with an increase in traffic, or an increase in the number of radio relay stations or radio terminal stations, and can prevent deterioration of transmission characteristics.

The parameter measurement unit of the radio base station apparatus according to the present invention further measures, for the radio station, an average value of data reception intervals, which are intervals of receiving data signals,
The estimation unit further estimates the transmission delay time and / or throughput at the time of applying the random access method using the average value of the data reception interval measured by the parameter measurement unit,
The method selection unit uses the transmission delay time and / or the throughput when the random access method estimated by the estimation unit is applied as the threshold for the predetermined transmission delay and the threshold for the predetermined throughput, respectively. It is characterized by.

  This radio base station apparatus uses the transmission delay time and / or throughput when the random access scheme is applied as a threshold when selecting a polling scheme as an access scheme used by a high traffic radio station. For this reason, the radio base station apparatus is configured to perform high traffic radio when it is estimated that the transmission delay time and / or throughput is superior when the polling method is applied than when the random access method is applied. By selecting the polling method as the access method used by the station, it is possible to prevent the transmission delay time or throughput from deteriorating.

A radio base station apparatus according to the present invention,
A traffic situation in which the transmission delay time when applying the random access method is measured, and when the difference between the transmission delay time when applying the random access method estimated by the estimation unit is larger than a threshold value, it is determined that the traffic is small A detection unit;
The method selection unit selects a random access method even when the polling method is selected as the access method used by the high traffic radio station when the traffic state detection unit determines that the traffic is low. And

A radio base station apparatus according to the present invention,
Of the random access slots set in the radio frame, the number of used slots used is measured, and if the ratio between the number of used slots and the number of random access slots is smaller than a threshold, traffic A traffic condition detection unit that determines that the
The method selection unit selects a random access method even when the polling method is selected as the access method used by the high traffic radio station when the traffic state detection unit determines that the traffic is low. And

  The radio base station apparatus selects the random access method when it is determined that the traffic is low even if the polling method is selected as the access method used by the high traffic radio station. When the traffic is low, the random access method has better transmission delay time or throughput than the polling method. For this reason, this radio base station apparatus can prevent the transmission delay time or the throughput from deteriorating by selecting the random access method as the access method used by the high traffic radio station when it is determined that the traffic is low.

A radio base station apparatus according to the present invention,
A radio base station apparatus that adopts a random access method or a polling method as an access method and performs radio communication with a plurality of radio stations using radio frames,
When there is a connection request in the polling access method from the wireless station, the amount of traffic generated within a unit time is measured for each wireless station, and the amount of traffic generated within the unit time is a predetermined standard. Parameter measurement for calculating the number of the high traffic radio stations, wherein the radio station exceeding the value is a high traffic radio station, the radio station in which the amount of traffic generated within the unit time is within the reference value is a low traffic radio station And
Based on the number of high traffic radio stations calculated by the parameter measurement unit and the number of polling signals that can be allocated in the radio frame, both transmission delay time and throughput when applying the polling method of the high traffic radio station Or an estimation unit for estimating either one of them,
Either or both of a state in which the transmission delay time when applying the polling method estimated by the estimation unit is smaller than a predetermined transmission delay time threshold and a state in which the throughput when applying the polling method is larger than a predetermined throughput threshold On the other hand, a communication unit that starts communication with the wireless station that has requested connection;
It is characterized by providing.

  When the radio base station apparatus receives a connection request from a radio station, the radio base station apparatus assigns the radio station only when a polling cycle that satisfies a desired condition can be assigned to each high traffic radio station. Can be connected.

  Therefore, the present invention can provide a radio base station apparatus that can flexibly cope with an increase in traffic, or an increase in the number of radio relay stations or radio terminal stations, and can prevent deterioration of transmission characteristics.

  The present invention can provide a radio base station apparatus that can flexibly cope with an increase in traffic or an increase in the number of radio relay stations and radio terminal stations and can prevent deterioration in transmission characteristics.

It is a figure explaining the operation | movement of the back-off in the collision avoidance algorithm used by IEEE802.11. It is a figure explaining the radio | wireless access system containing the radio base station apparatus which concerns on this invention. It is a figure explaining the structure of a MAC frame. 1 is a block diagram illustrating a radio access system including a radio base station apparatus according to Embodiment 1. FIG. It is a figure explaining the access sequence at the time of selecting random access as an access method applied to transmission of a bandwidth allocation request. It is a figure explaining an access sequence at the time of selecting polling as an access method applied to transmission of a bandwidth allocation request. It is a figure explaining the back-off sequence in random access. 6 is a flowchart for explaining the operation of the radio base station apparatus according to the first embodiment. It is a figure showing the relationship between the number of wireless relay stations, and the average transmission delay time of a wireless terminal station. 6 is a block diagram illustrating a radio access system including a radio base station apparatus according to Embodiment 2. FIG. 6 is a flowchart for explaining the operation of the radio base station apparatus according to the second embodiment. 10 is a block diagram illustrating a radio access system including a radio base station apparatus according to Embodiment 3. FIG. 10 is a flowchart for explaining the operation of the radio base station apparatus according to the third embodiment. 10 is a block diagram illustrating a radio access system including a radio base station apparatus according to Embodiment 4. FIG. 10 is a flowchart for explaining the operation of the radio base station apparatus in the fourth embodiment. FIG. 10 is a block diagram illustrating a radio access system including a radio base station apparatus according to a fifth embodiment. 10 is a flowchart for explaining the operation of the radio base station apparatus according to the fifth embodiment.

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

(Embodiment 1)
In the present embodiment, a method will be described in which a radio base station estimates a transmission delay time when random access or polling is applied, and selects a method estimated to be superior in transmission delay time as an access method.

  The configuration of the wireless access system in this embodiment is shown in FIG. The wireless access system shown in FIG. 2 includes one wireless base station 101 connected to a wired network, a plurality of wireless relay stations 102 and wireless terminal stations 103 connected to the wired network via the wireless base station 101, and wireless It comprises a plurality of wireless terminal stations 103 connected to the wireless base station 101 via the relay station 102.

  FIG. 3 shows the configuration of the MAC frame used in the wireless access system in this embodiment. In FIG. 3, TDMA / TDD is used as an access method, and multidimensional connection and bidirectional communication are realized. The length of the MAC frame is fixed, the first half of the MAC frame is a downlink from the radio base station to the radio station, and the second half of the MAC frame is an uplink in the reverse direction.

  The downlink is composed of a broadcast area for transmitting broadcast information and a demand assignment area for transmitting user data. BCCH, FCCH, and RFCH are transmitted in the broadcast area. BCCH is used for reporting system common information such as a radio base station ID and a MAC frame number, FCCH is used for reporting information indicating the configuration of the MAC frame, and RFCH is the success or failure of random access in the previous MAC frame. Is used to report the random access parameters (initial backoff window size, PF) used in the above, the number of random access slots in the MAC frame, and the position of the random access slot.

  The uplink includes a demand assignment area for transmitting user data and a random access area composed of random access slots. That is, user data is transmitted in the demand assignment area for both downlink and uplink. The configuration of the MAC frame used for communication between the radio base station and the radio station is the same as that of the MAC frame used for communication between the radio relay station and the radio terminal station.

  Here, FIG. 5 shows an access sequence when random access is selected as an access method applied to transmission of a bandwidth allocation request in the uplink. The access sequence is roughly divided into three phases: a bandwidth allocation request phase, a data transmission phase, and an ACK reception phase.

  In the bandwidth allocation request phase, the wireless station individually determines a transmission timing and transmits a bandwidth allocation request (random access signal) in the random access area. When the transmission of the bandwidth allocation request is successful, the process proceeds to the data transmission phase. Thereafter, the radio base station performs band allocation processing. At this time, the radio base station also allocates a downlink ACK for the next MAC frame simultaneously with the allocation of the uplink data.

  In the data transmission phase, the radio station waits for a data transmission band to be allocated by the radio base station. Bandwidth allocation is indicated by the FCCH. When the band is allocated, the wireless station transmits data using the band, and proceeds to the ACK reception phase. In the ACK reception phase, the wireless base station waits for an ACK indicating that the data has been received normally from the wireless base station. One access sequence is completed when the wireless station receives the ACK sent from the wireless base station. In addition, an access sequence in the case of transmitting a band allocation request by applying random access in the uplink between the radio base station and the radio station, and applying random access in the uplink between the radio relay station and the radio terminal station Thus, the access sequence when transmitting the bandwidth allocation request is the same.

  When transmitting a bandwidth allocation request by applying random access, backoff is performed in order to avoid collision of packets transmitted from each wireless station. FIG. 7 shows a back-off sequence in random access.

  The communication unit of the radio base station transmits information indicating the initial backoff window size, PF, the number of random access slots in the MAC frame, and the position of the random access slot using the RFCH in the broadcast area located at the head of the MAC frame. Do [1]. The communication unit of the wireless station updates each parameter to the latest value by receiving each MAC frame and RFCH [2].

  Next, when transmission data is generated, the communication control unit of the wireless station calculates the number of backoff slots from the initial backoff window size [3]. Here, the calculated number of back-off slots uses a random number in the range of “0 to {initial back-off window size−1}”.

  The wireless station performs backoff in the random access area of the MAC frame by the calculated number of backoff slots, and then transmits a bandwidth allocation request from the communication unit in the random access slot. When the number of random access slots in the MAC frame in which the transmission data is generated is smaller than the calculated back-off slot number, the back-off operation is continuously performed in the next MAC frame. Note that the back-off sequence used in communication between the radio base station and the radio station is the same as the back-off sequence used in communication between the radio relay station and the radio terminal station.

  On the other hand, FIG. 6 shows an access sequence when polling is selected as an access method applied to transmission of a bandwidth allocation request in the uplink. In the bandwidth allocation request phase, a wireless base station takes the initiative in allocating a bandwidth for transmitting a bandwidth allocation request to the wireless station, and the wireless station uses the bandwidth allocated in the uplink demand assignment area to perform a bandwidth allocation request (polling signal). ) To move to the data transmission phase. Bandwidth allocation is indicated by the FCCH. Thereafter, the radio base station performs band allocation processing. At this time, the radio base station also allocates a downlink ACK for the next MAC frame simultaneously with the allocation of the uplink data.

  In the data transmission phase, the radio station waits for a data transmission band to be allocated by the radio base station. Bandwidth allocation is indicated by the FCCH. When the band is allocated, the wireless station transmits data using the band, and proceeds to the ACK reception phase. In the ACK reception phase, the wireless base station waits for an ACK indicating that the data has been received normally from the wireless base station. One access sequence is completed when the wireless station receives the ACK sent from the wireless base station. In the present embodiment, it is assumed that the bandwidth allocation request is not transmitted by applying polling in the uplink between the radio relay station and the radio terminal station.

  A method of calculating the transmission delay time when applying random access and the transmission delay time when applying polling when such an access method is employed will be described.

  First, a method for calculating a transmission delay time (a time from the start of transmission of a bandwidth allocation request for user data to successful transmission) when random access is applied will be described.

The transmission delay time D _r at random access applications, by applying the Markov model representing the transmission operation of the radio station, data occurrence probability P _g, transmission probability tau, the transmission failure probability p, the initial backoff window size W _0, A relational expression of the number N of radio stations connected to the radio base station and the maximum number of retransmissions m is obtained and calculated by solving it analytically. The data occurrence probability P _g can be determined by measuring the reception interval of data arriving at the radio base station for each radio station (data generation interval). Transmission delay time period D _r at random access application is determined based on the number 1 and number 2. That is, the transmission probability τ and the transmission failure probability p are calculated by solving the equations 1 and 2 which are simultaneous equations of the transmission probability τ and the transmission failure probability p.

Next, when the transmission probability τ and the transmission failure probability p are obtained from Equations 1 and 2, the number of transmissions of the bandwidth allocation request transmitted by the wireless station from the start of transmission of the bandwidth allocation request for user data to the successful transmission is obtained from Equation 3. A bandwidth allocation request transmission count M to be expressed is obtained.

When the number M of bandwidth allocation request transmissions is obtained from Equation 3, the average backoff slot number bo_slot_num required from the start of transmission of the bandwidth assignment request for user data to successful transmission is obtained from Equation 4.

When obtaining the average backoff slot number bo_slot_num from this number 4, the transmission delay time _{D r} at random access applications than the number 5 is obtained. Note that ra_slot_num is the number of random access slots in each MAC frame. That is, Equation 5 calculates the transmission delay time when random access is applied by obtaining the period of the MAC frame that can transmit the bandwidth allocation request based on the back-off for each wireless station.

Next, a method for calculating a transmission delay time (polling cycle) when applying polling will be described. Transmission delay time D _p at the polling application is calculated from the number N of radio stations generating the assignable bandwidth quantity band _'p to the polling signal traffic exceeds the reference value in each MAC frame (heavy traffic radio station). Here, the bandwidth amount that can be allocated to the polling signal is obtained by subtracting the bandwidth amount allocated to BCCH, FCCH, RFCH, LCCH (for ACK), UDCH, and RACH from the bandwidth amount that can be allocated to one MAC frame. This corresponds to the remaining bandwidth.

The band amount band _p that can be allocated to the polling signal in each MAC frame and the number N of high-traffic wireless stations are calculated by the transmission delay time calculation parameter measurement unit, and band _p is obtained from Equation 6. Note that band _all is the MAC frame size, band _B is the amount of bandwidth allocated to the BCCH in each MAC frame, band _F is the amount of bandwidth allocated to the FCCH in each MAC frame, and band _RF is the amount of bandwidth allocated to the RFCH in each MAC frame. , Band _L is a bandwidth amount allocated to LCCH (for ACK) in each MAC frame, band _U is a bandwidth amount allocated to UDCH in each MAC frame, and band _RA is a bandwidth amount allocated to RACH in each MAC frame.

When the band amount band _p that can be allocated to the polling signal in each MAC frame is obtained from Equation 6, the number p_num of polling signals that are assigned to each MAC frame is obtained from Equation 7. Note that L _p is the size of the polling signal.

When determining the number p_num polling signals allocated to each MAC frame from the number 7, the transmission delay time for the polling from the number 8 apply D _p is obtained. Since this _Dp is the shortest value in the range of polling cycles that can be allocated to each high traffic radio station, the range of polling cycles that can be allocated is _Dp or more. That is, when a band for transmitting polling signals is sequentially assigned to N high-traffic wireless stations, the transmission delay time at the time of polling is obtained by expressing the allocation period as a MAC frame period. .

  Here, FIG. 4 shows a block diagram for explaining the functions of the radio access system shown in FIG. FIG. 8 is a flowchart showing the operation of the radio base station.

  First, the radio base station 101 includes a central processing unit (CPU) and a storage device (memory) as hardware, and transmission delay time calculation parameter measurement unit 11, method selection unit 13, notification signal as functional blocks. It has a generation unit 17 and a communication unit 14. The system selection unit 13 includes a transmission delay time calculation unit 12 a and a desired polling cycle calculation unit 12 b, and the transmission delay time calculation unit 12 a includes a polling cycle calculation unit 16.

  The transmission delay time calculation parameter measurement unit 11 calculates the data generation interval by obtaining the average value of the reception intervals for each radio station when data is received from the radio station (step S11 and step S12). The data generation interval is used to calculate the transmission delay time during random access (Equation 1). Also, the generated traffic volume is measured for each radio station, it is determined whether the generated traffic volume exceeds the reference value, and the number of radio stations (high traffic radio stations) whose generated traffic volume exceeds the reference value is updated. Thus, the number of high traffic radio stations is calculated (step S13). These high traffic radio stations are subject to polling. Note that a value predetermined for each embodiment is used as the reference value, and this value is stored in a predetermined memory area in the transmission delay time calculation parameter measurement unit 11.

  Further, the transmission delay time calculation parameter measurement unit 11 determines the bandwidth amount that can be allocated to the polling signal from the total bandwidth amount allocated to BCCH, FCCH, RFCH, LCCH (for ACK), UDCH, and RACH in each MAC frame. Then, the polling signal band amount is calculated by obtaining the average value (Equation 6, step S14).

  The polling cycle calculation unit 16 calculates a range of a polling cycle (a cycle in which a polling signal is assigned to each high traffic radio station) that can be assigned to each high traffic radio station when applying polling (Equation 8, Step S16). ). The polling cycle calculation unit 16 is included in the transmission delay time calculation unit 12a and plays a role corresponding to the calculation of the transmission delay time when polling is applied.

  Based on the data generation interval measured by the transmission delay time calculation parameter measurement unit 11, the transmission delay time calculation unit 12a performs transmission delay time (bandwidth for user data) when applying random access by performing Equations 1 to 5. A time from the start of transmission of the allocation request to the successful transmission is calculated (step S15). Also, the polling cycle calculation unit 16 calculates a transmission delay time when applying each polling cycle that can be assigned to each high traffic radio station (this polling cycle is regarded as a transmission delay time when applying polling) (step). S17).

  The desired polling period calculation unit 12b calculates a polling period (desired polling period) that satisfies a desired condition when applying polling (step S18). In the present embodiment, the desired condition is that the transmission delay time when applying random access is superior (shorter than the transmission delay time when applying random access). The transmission delay time calculation unit 12a and the polling period calculation unit 16 are also collectively referred to as an estimation unit.

  The method selection unit 13 compares the calculated range of the assignable polling period with a desired polling period. As a result of the comparison, if the desired polling period is assignable, that is, if there is a period shorter than the desired polling period (transmission delay time when applying random access) within the range of the assignable polling period, Select polling. On the contrary, if the desired polling cycle is not assignable, that is, there is no cycle shorter than the desired polling cycle within the range of assignable polling cycles, random access is selected as the access method (step S19).

  The notification signal generation unit 17 generates a notification signal representing the selected access method.

  The communication unit 14 has a function of communicating with a wireless station and a function of transmitting a notification signal representing the selected access method generated by the notification signal generation unit 17 to the wireless station.

  On the other hand, the radio relay station 102 includes a central processing unit (CPU) and a storage device (memory) as hardware, and includes a communication unit 51 and a communication control unit 52 as functional blocks.

  The communication unit 51 communicates with the wireless base station 101 or the wireless terminal station 103.

  The communication control unit 52 performs control to transmit a band allocation request according to a notification signal indicating the selected access method transmitted from the radio base station 101.

  On the other hand, the wireless terminal station 103 includes a central processing unit (CPU) and a storage device (memory) as hardware, and includes a communication unit 51 and a communication control unit 52 as functional blocks.

  The communication unit 51 of the wireless terminal station 103 connected to the wireless base station 101 communicates with the wireless base station 101. The communication unit 51 of the wireless terminal station 103 connected to the wireless relay station 102 communicates with the wireless relay station 102.

  The communication control unit 52 of the wireless terminal station 103 connected to the wireless base station 101 performs control to transmit a bandwidth allocation request in accordance with the notification signal indicating the selected access method transmitted from the wireless base station 101. The communication control unit 52 of the wireless terminal station 103 connected to the wireless relay station 102 performs control for transmitting a bandwidth allocation request by applying random access.

  FIG. 9 shows a relationship between the number of wireless relay stations and the average transmission delay time of wireless terminal stations.

  Here, it is assumed that all wireless terminal stations are connected to the wireless base station via wireless relay stations. Also, if there is no polling cycle that can realize a transmission delay time shorter than the transmission delay time of the wireless relay station when applying the estimated random access within the range of polling cycles that can be assigned to each estimated wireless relay station Select random access as the access method, and conversely, within the range of polling cycles that can be allocated to each estimated radio relay station, transmission shorter than the transmission delay time of the estimated radio relay station when applying random access When there is a polling cycle that can realize the delay time, polling is selected as the access method. It can be confirmed that the average transmission delay time can be reduced by the access method selection method of this embodiment.

  According to this embodiment, the radio base station estimates the transmission delay time when applying random access based on the measured data generation interval. Also, based on the amount of bandwidth that can be allocated to polling signals and the number of high traffic radio stations in each measured MAC frame, the radio base station estimates the range of polling cycles that can be allocated to each high traffic radio station. Then, the transmission delay time when each polling period is applied is estimated. Next, the wireless base station calculates a desired polling period that satisfies a desired condition when applying polling. Then, the estimated range of the assignable polling cycle is compared with the calculated desired polling cycle, and an optimum method is selected as an access method among random access and polling. For example, when the desired condition is that the transmission delay time when applying polling is shorter than the transmission delay time when applying random access, it is possible to reduce the transmission delay time of the wireless terminal station.

(Embodiment 2)
In the present embodiment, a method will be described in which a radio base station estimates a throughput when random access or polling is applied, and selects a method that is estimated to be excellent in throughput as an access method. Note that the configuration of the wireless access system, the MAC frame configuration, the access sequence, and the back-off sequence are the same as those in the first embodiment described above, and a description thereof will be omitted. FIG. 10 is a block diagram illustrating functions of the wireless access system in the present embodiment. Also, the operation of the base station is shown in FIG. Here, the description of the same functions as those in the first embodiment will be omitted, and differences will be described below.

  In this embodiment, the radio base station 101 has a throughput calculation parameter measurement unit 21 instead of the transmission delay time calculation parameter measurement unit 11 and a throughput calculation unit 22a instead of the transmission delay time calculation unit 12a. The throughput calculation unit 22a and the polling cycle calculation unit 16 are also collectively referred to as an estimation unit.

  The throughput calculation parameter measurement unit 21 calculates a data generation interval by obtaining an average value of the reception interval for each wireless station when data is received from the wireless station (step S11 and step S12). Also, the generated traffic volume is measured for each radio station, it is determined whether the generated traffic volume exceeds the reference value, and the number of radio stations (high traffic radio stations) whose generated traffic volume exceeds the reference value is updated. Thus, the number of high traffic radio stations is calculated (step S13). These high traffic radio stations are subject to polling. Note that a value predetermined for each embodiment is used as the reference value, and this value is stored in a predetermined memory area in the throughput calculation parameter measurement unit 21.

  Further, the throughput measurement parameter measurement unit 21 calculates the average of the bandwidth amount that can be allocated to the polling signal from the total bandwidth amount allocated to BCCH, FCCH, RFCH, LCCH (for ACK), UDCH, and RACH in each MAC frame. By obtaining the value, the polling signal bandwidth is calculated (step S14).

  The throughput calculator 22a calculates the throughput when random access is applied according to the following Equation 9 (step S25). Here, the ratio between the bandwidth required for user data transmission (user data signal size) and the bandwidth required from the start of transmission of the bandwidth allocation request to the completion of transmission of user data is regarded as the throughput when applying random access. . Further, according to the following formula 10, the throughput at the time of applying each polling period that can be allocated to the high traffic radio station calculated by the polling period calculation unit 16 is calculated (step S27). Here, the ratio of the amount of bandwidth required for user data transmission (user data signal size) and the amount of bandwidth required from the generation of user data to the completion of user data transmission is regarded as the throughput at the time of polling application.

  The desired polling period calculation unit 12b calculates a polling period (desired polling period) that satisfies a desired condition when applying polling (step S18). In this embodiment, the desired condition is that the throughput is higher than the throughput when applying random access (higher than the throughput when applying random access).

  Here, a method for calculating the throughput when applying random access and the throughput when applying polling will be described.

  First, a method for calculating the throughput when applying random access (the ratio of the user data signal size and the amount of bandwidth necessary from the start of transmission of a bandwidth allocation request to user data until the completion of transmission of user data) is described.

  The throughput calculation unit 22a obtains a bandwidth allocation request transmission count M indicating the number of transmissions of the bandwidth allocation request transmitted by the wireless station from the start of transmission of the bandwidth allocation request for user data to the successful transmission according to the procedure described in the first embodiment. . Note that the data occurrence probability necessary for obtaining the bandwidth allocation request transmission count M is obtained from the data generation interval calculated by the throughput calculation parameter measurement unit 21.

When the bandwidth allocation request transmission count M is obtained, the throughput _Tr when random access is applied is obtained from Equation 9. Note that L _d is a user data signal size, and L _r is a random access signal size.

  Next, a method for calculating the throughput when applying polling (the ratio of the user data signal size and the amount of bandwidth necessary from the generation of user data to the completion of transmission of user data) will be described.

  The throughput calculation unit 22a obtains a polling cycle range that can be allocated to each high traffic radio station according to the procedure described in the first embodiment (step S16). It should be noted that the amount of bandwidth that can be allocated to the polling signal and the number of high-traffic radio stations in each MAC frame necessary for obtaining the range of assignable polling cycles are calculated by the parameter calculation unit 21 for calculating throughput.

When the range of the polling period that can be allocated is obtained, the throughput T _p when each polling period is applied is obtained from Equation 10. L _d is the user data signal size, L _p is the polling signal size, C _d is the data generation interval, and C _p is the polling period. The data generation interval is calculated by the parameter calculation unit 21 for throughput calculation.

  According to this embodiment, the radio base station estimates the throughput when applying random access based on the measured data generation interval. Also, based on the amount of bandwidth that can be allocated to polling signals and the number of high traffic radio stations in each measured MAC frame, the radio base station estimates the range of polling cycles that can be allocated to each high traffic radio station. Then, based on the measured data generation interval, the throughput when applying each polling period is estimated. Next, the wireless base station calculates a desired polling period that satisfies a desired condition when applying polling. Then, the estimated range of the assignable polling cycle is compared with the calculated desired polling cycle, and an optimum method is selected as an access method among random access and polling.

(Embodiment 3)
In the present embodiment, a method will be described in which a radio base station estimates a transmission delay time and throughput when random access or polling is applied, and selects a method that is estimated to have excellent transmission delay time and throughput as an access method.

  FIG. 12 is a block diagram illustrating functions of the wireless access system in the present embodiment. FIG. 13 shows the operation of the base station. Here, the description of the same function as the embodiment (1-2) is omitted, and the difference will be described below.

  In the present embodiment, the radio base station 101 uses a transmission delay time / throughput calculation parameter measurement unit 31 instead of the transmission delay time calculation parameter measurement unit 11 of the first embodiment and the throughput calculation parameter measurement unit 21 of the second embodiment. The transmission delay time / throughput calculation unit 32a is provided instead of the transmission delay time calculation unit 12a of the first embodiment and the throughput calculation unit 22a of the second embodiment. The transmission delay time / throughput calculation unit 32a and the polling cycle calculation unit 16 are also collectively referred to as an estimation unit.

  The transmission delay time / throughput calculation parameter measurement unit 31 calculates the data generation interval by obtaining the average value of the reception interval for each wireless station when data is received from the wireless station (step S11 and step S12). Also, the generated traffic volume is measured for each radio station, it is determined whether the generated traffic volume exceeds the reference value, and the number of radio stations (high traffic radio stations) whose generated traffic volume exceeds the reference value is updated. Thus, the number of high traffic radio stations is calculated (step S13). These high traffic radio stations are subject to polling. Note that a value predetermined for each embodiment is used as the reference value, and this value is stored in a predetermined memory area in the transmission delay time / throughput calculation parameter measurement unit 31.

  Further, the transmission delay time / throughput calculation parameter measurement unit 31 can be assigned to the polling signal from the total amount of bandwidths assigned to BCCH, FCCH, RFCH, LCCH (for ACK), UDCH, and RACH in each MAC frame. By calculating the average value of the bandwidth, the bandwidth for polling signal is calculated (step S14).

  The transmission delay time / throughput calculation unit 32a calculates the transmission delay time and throughput when random access is applied (step S35). Here, the time from the start of transmission of a bandwidth allocation request for user data to the successful transmission is regarded as a transmission delay time when random access is applied, and the bandwidth required for user data transmission (user data signal size) and bandwidth allocation The ratio of the amount of bandwidth required from the start of request transmission to the completion of user data transmission is regarded as the throughput when applying random access. Further, the transmission delay time and the throughput are calculated when applying each polling period that can be allocated to the high traffic radio station calculated by the polling period calculation unit 16 (step S37). Here, this polling cycle is regarded as a transmission delay time when polling is applied, and the amount of bandwidth required for user data transmission (user data signal size) and the amount of bandwidth required from user data generation to the completion of user data transmission. Is the throughput when applying polling.

  The desired polling period calculation unit 12b calculates a polling period (desired polling period) that satisfies a desired condition when applying polling (step S18). In this embodiment, the desired condition is that the transmission delay time and throughput are higher than when random access is applied (shorter than the transmission delay time when random access is applied and higher than the throughput when random access is applied).

  According to this embodiment, the radio base station estimates the transmission delay time and throughput when applying random access based on the measured data generation interval. Also, based on the amount of bandwidth that can be allocated to polling signals and the number of high traffic radio stations in each measured MAC frame, the radio base station estimates the range of polling cycles that can be allocated to each high traffic radio station. Then, the transmission delay time when each polling period is applied is estimated, and further, the throughput when each polling period is applied is estimated based on the measured data generation interval. Next, the wireless base station calculates a desired polling period that satisfies a desired condition when applying polling. Then, the estimated range of the assignable polling cycle is compared with the calculated desired polling cycle, and an optimum method is selected as an access method among random access and polling.

(Embodiment 4)
In this embodiment, a method for selecting random access as an access method when a traffic situation in which a change in transmission characteristics is not observed even when either random access or polling is applied will be described.

  FIG. 14 is a block diagram illustrating functions of the wireless access system in the present embodiment. FIG. 15 shows the operation of the radio base station. Here, descriptions of the same functions as those in the embodiments (1 to 3) are omitted, and differences will be described below.

  In the present embodiment, a traffic status detection unit 45 is newly added to the radio base station 101 described in the embodiments (1 to 3). The traffic situation detection unit 45 detects a traffic situation (low traffic situation) in which there is little traffic and no change is seen in the transmission characteristics even if either random access or polling is applied to the access method. As a detection method, for example, the transmission delay time at the time of applying random access estimated according to the method described in Embodiment 1 is compared with the measured average transmission delay time at the time of applying random access. If the difference in the measured average transmission delay time is equal to or greater than the threshold value, it is detected that the traffic situation is low. In addition, the average usage status (number of used random access slots / total number of random access slots) in units of MAC frames for random access is measured, and if it is equal to or less than a threshold, it is detected that the traffic status is low. There is a way. Note that a predetermined value for each embodiment is used as the threshold value, and this value is stored in a predetermined memory area in the traffic state detection unit 45.

  In addition, a function described below is added to the method selection unit 43 of the radio base station.

  The method selection unit 43 selects random access as the access method when the traffic condition detection unit 45 detects a low traffic condition. Conversely, when the low traffic situation is not detected, as described in the embodiments (1 to 3), in addition to estimating the transmission delay time and / or the throughput when applying random access, A transmission delay time and / or a throughput at the time of applying each polling period that can be assigned to a radio station whose generated traffic exceeds a reference value is estimated. Then, a desired polling period is calculated, and the range of the assignable polling period is compared with the desired polling period, thereby selecting an optimum method as an access method from random access and polling.

  According to this embodiment, when a traffic situation is detected in which there is little traffic and no change in transmission characteristics is observed even if either random access or polling is applied to data transmission, random access is selected as the access method. I tried to do it. Therefore, only when the transmission data is generated in the case where the traffic supplied to the radio access system to which the present invention is applied is small and no change is seen in the transmission characteristics even if either random access or polling is applied. By selecting random access for transmitting a bandwidth allocation request, high bandwidth utilization efficiency can be expected.

(Embodiment 5)
In the present embodiment, when the radio base station receives a connection request from the radio station, it estimates the transmission delay time and / or throughput at the time of applying the polling, and can satisfy a desired condition. Only the method of connecting the radio station will be described.

  FIG. 16 is a block diagram illustrating functions of the wireless access system in the present embodiment. FIG. 17 shows the operation of the radio base station. Here, the description of the same functions as those of the embodiments (1 to 4) is omitted, and differences will be described below.

  In the present embodiment, a wireless station connection availability determination unit 53 is provided instead of the method selection unit (13, 23, 33, 43) of the wireless base station 101 in the embodiment (1-4). The wireless station connection possibility determination unit 53, when receiving a connection request from a wireless station, a range of polling cycles that can be assigned to each wireless station whose generated traffic calculated by the polling cycle calculation unit 16 exceeds a reference value, The desired polling period calculated by the desired polling period calculation unit 12b is compared. In the comparison result, if the desired polling period is assignable, that is, if there is a period shorter than the desired polling period within the range of assignable polling periods, the connection of the relevant radio station is permitted and polling is performed as the access method. Select. On the other hand, if the desired polling period cannot be assigned, that is, if there is no period shorter than the desired polling period within the range of the assignable polling period, the connection of the radio station is prohibited.

  In addition, the desired polling cycle calculation unit 12b, the notification signal generation unit 17, and the communication unit 14 of the radio base station 101 have the functions described below.

  The desired polling period calculation unit 12b calculates a polling period (desired polling period) that satisfies a desired condition when polling is applied. Here, the desired condition is to satisfy a specified transmission delay time, to satisfy a specified throughput, etc. When there are a plurality of conditions, the most severe condition is applied to calculation of a desired polling period. .

  The broadcast signal generation unit 17 generates a broadcast signal representing the connection result of the radio station and a broadcast signal representing the selected access method.

  The communication unit 14 has a function of communicating with a wireless station, and a function of transmitting a notification signal indicating a connection result of the wireless station generated by the notification signal generation unit 17 and a notification signal indicating a selected access method to the wireless station. .

  The communication control unit 51 included in the wireless relay station 102 has a function described below. When the notification signal indicating the connection result of the radio station transmitted from the radio base station 101 indicates that the connection between the radio base station 101 and the radio relay station 102 is permitted, the communication control unit 51 In accordance with the broadcast signal indicating the selected access method transmitted from, the control for transmitting the bandwidth allocation request is performed.

  The communication control unit 53 included in the wireless terminal station 103 has a function described below. The communication control unit 53 of the wireless terminal station 103 connected to the wireless base station 101 indicates that the notification signal indicating the connection result of the wireless station transmitted from the wireless base station 101 is a connection between the wireless base station 101 and the wireless terminal station 103. In the case where it represents that the access is permitted, control is performed to transmit the band allocation request according to the broadcast signal indicating the selected access method transmitted from the radio base station 101. The communication control unit 53 of the wireless terminal station 103 connected to the wireless relay station 102 performs control to transmit a bandwidth allocation request by applying random access.

  According to the present embodiment, when the wireless base station receives a connection request from the wireless station, a polling period that satisfies a desired condition can be assigned to each wireless station whose generated traffic exceeds a reference value. Only connected to the radio station. Therefore, the wireless access system to which this embodiment is applied can maintain the communication quality defined in advance.

11: Transmission delay time calculation parameter measurement unit 12a: Transmission delay time calculation unit 12b: Desired polling cycle calculation unit 13: Method selection unit 14: Communication unit 16: Polling cycle calculation unit 17: Notification signal generation unit 21: For throughput calculation Parameter measurement unit 22a: Throughput calculation unit 23: Policy selection unit 31: Transmission delay time / throughput calculation parameter measurement unit 32a: Transmission delay time / throughput calculation unit 33: Method selection unit 43: Method selection unit 45: Traffic condition detection unit 51: Communication unit 52: Communication control unit 53: Wireless station connection availability determination unit 101: Wireless base station 102: Wireless relay station 103: Wireless terminal station

Claims (5)

A radio base station apparatus that adopts a random access method or a polling method as an access method and performs radio communication with a plurality of radio stations using radio frames,
The amount of traffic generated within a unit time is measured for each wireless station, and the amount of traffic generated within the unit time exceeds a predetermined reference value as a high traffic wireless station, and is generated within the unit time. A parameter measurement unit that calculates the number of the high traffic radio stations, the radio station having the traffic amount within the reference value as a low traffic radio station,
Based on the number of high traffic radio stations calculated by the parameter measurement unit and the number of polling signals that can be assigned in the radio frame, transmission delay time and throughput when a polling method is applied to the high traffic radio stations An estimation unit that estimates both or either of
Either or both of a state in which the transmission delay time when applying the polling method estimated by the estimation unit is smaller than a predetermined transmission delay time threshold and a state in which the throughput when applying the polling method is larger than a predetermined throughput threshold On the other hand, when a polling method is selected as an access method with the high traffic radio station, a state in which a transmission delay time when the polling method is applied is larger than a predetermined transmission delay time threshold value and when the polling method is applied. A random access method is selected as an access method with the high-traffic radio station when the throughput is lower or lower than a predetermined throughput threshold, and in either case, the access with the low-traffic radio station is selected. A method selection unit for selecting a random access method as an access method;
A communication unit that communicates with the wireless station using the access method selected by the method selection unit;
A radio base station apparatus comprising: The parameter measurement unit further measures an average value of data reception intervals, which are intervals of receiving data signals, for the wireless station,
The estimation unit further estimates the transmission delay time and / or throughput at the time of applying the random access method using the average value of the data reception interval measured by the parameter measurement unit,
The method selection unit uses the transmission delay time and / or the throughput when the random access method estimated by the estimation unit is applied as the threshold for the predetermined transmission delay and the threshold for the predetermined throughput, respectively. The radio base station apparatus according to claim 1. A traffic situation in which the transmission delay time when applying the random access method is measured, and when the difference between the transmission delay time when applying the random access method estimated by the estimation unit is larger than a threshold value, it is determined that the traffic is small A detection unit;
The method selection unit selects a random access method even when the polling method is selected as the access method used by the high traffic radio station when the traffic state detection unit determines that the traffic is low. The radio base station apparatus according to claim 2. Of the random access slots set in the radio frame, the number of used slots used is measured, and if the ratio between the number of used slots and the number of random access slots is smaller than a threshold, traffic A traffic condition detection unit that determines that the
The method selection unit selects a random access method even when the polling method is selected as the access method used by the high traffic radio station when the traffic state detection unit determines that the traffic is low. The radio base station apparatus according to claim 2. A radio base station apparatus that adopts a random access method or a polling method as an access method and performs radio communication with a plurality of radio stations using radio frames,
When there is a connection request in the polling access method from the wireless station, the amount of traffic generated within a unit time is measured for each wireless station, and the amount of traffic generated within the unit time is a predetermined standard. Parameter measurement for calculating the number of the high traffic radio stations, wherein the radio station exceeding the value is a high traffic radio station, the radio station in which the amount of traffic generated within the unit time is within the reference value is a low traffic radio station And
Based on the number of high traffic radio stations calculated by the parameter measurement unit and the number of polling signals that can be allocated in the radio frame, both transmission delay time and throughput when applying the polling method of the high traffic radio station Or an estimation unit for estimating either one of them,
Either or both of a state in which the transmission delay time when applying the polling method estimated by the estimation unit is smaller than a predetermined transmission delay time threshold and a state in which the throughput when applying the polling method is larger than a predetermined throughput threshold On the other hand, a communication unit that starts communication with the wireless station that has requested connection;
A radio base station apparatus comprising:

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