Base station, communication method, and communication program

Abstract

To reduce a packet discard rate.SOLUTION: A base station (2) includes a priority calculation unit (224), a resource allocation unit (225), and a communication unit (226). The priority calculation unit calculates a priority metric indicating a priority order in which a plurality of mobile object communication terminals perform wireless communication, based on a future position in which a future position of each of mobile object communication terminals (3) that perform the wireless communication while moving inside a predetermined area (9) is estimated, a radio wave map in which a past channel condition in each of sub-areas included in an area are statistically aggregated, and a maximum waiting time of an un-transmitted packet stored in a buffer in each of mobile object communication terminals. The resource allocation unit allocates a plurality of radio resources obtained by combining a plurality of time slots and a plurality of frequency channels to a plurality of mobile object communication terminals based on the priority metric. The communication unit transmits resource information representing radio resources to the plurality of mobile object communication terminals.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a base station, a communication method, and a communication program, and can be suitably used, for example, in a base station that performs wireless communication with multiple mobile communication terminals, a communication method performed by the base station, and a communication program for realizing the communication method. [Background technology]

[0002] The surrounding wireless environment changes over time and place, and mobile communication terminals require resource allocation that takes communication quality into consideration. Two resource allocation methods have been proposed: Proportional Fair (PF) and Proactive Proportional Fair (PPF).

[0003] In relation to the above, Non-Patent Document 1 (L. Shen, T. Wang, and S. Wang, "Proactive proportional fair: A novel scheduling algorithm based on future channel information in OFDMA systems," in Proc. IEEE / CIC ICCC, Oct. 2019.) describes the PPF method. The PPF method allocates wireless resources by taking into account past, present, and future channel conditions. Compared with the PF method, which allocates wireless resources by taking into account past and present channel conditions, the PPF method can improve throughput. However, it is not suitable for environments where wireless channels change rapidly, such as indoors in a factory where many metal objects are present. The reason for this is that the time length of future channels considered in the PPF method is fixed. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] L. Shen, T. Wang, and S. Wang, “Proactive proportional fair: A novel scheduling algorithm based on future channel information in ofdma systems,” in Proc. IEEE / CIC ICCC, Oct. 2019. Summary of the Invention [Problem to be solved by the invention]

[0005] For example, a scenario in which the present disclosure can be applied is an AGV (Automated Guided Vehicle) used to transport materials in a manufacturing site, warehouse, or the like. The AGV is equipped with a mobile communication terminal that performs wireless communication with a base station while moving within a predetermined area. In indoor environments such as manufacturing sites and warehouses, the presence of many metal objects can lead to a poor communication environment.

[0006] In view of the above circumstances, one object of the present disclosure is to provide a base station, a communication method, and a communication program that reduce the packet discard rate in wireless communication with a mobile communication terminal in a poor communication environment. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0007] The following describes the means for solving the problems using the numbers and symbols used in the description of the invention. These numbers and symbols are added in parentheses for reference purposes to show an example of the correspondence between the claims and the description of the invention. Therefore, the claims should not be interpreted as being limited by the parenthetical descriptions.

[0008] According to one embodiment, the base station (2) includes a priority calculation unit (224), a resource allocation unit (225), and a communication unit (226). The priority calculation unit (224) calculates a priority metric representing the priority of wireless communication for the multiple mobile communication terminals (3) based on estimated future locations of each of the multiple mobile communication terminals (3) that perform wireless communication while moving within a predetermined area (9), a radio wave map statistically aggregating past channel conditions in each of multiple sub-areas included in the area (9), and a maximum waiting time for untransmitted packets stored in a buffer in each of the multiple mobile communication terminals (3). The resource allocation unit (225) allocates multiple wireless resources, each consisting of a combination of multiple time slots and multiple frequency channels, to the multiple mobile communication terminals (3) based on the priority metric. The communication unit (226) transmits resource information representing the wireless resources to the multiple mobile communication terminals (3).

[0009] According to one embodiment, a communication method includes estimating (S03) the future location of each of a plurality of mobile communication terminals (3) that communicate wirelessly while moving within a predetermined area (9). The communication method further includes detecting (S02) the maximum waiting time of untransmitted packets stored in a buffer in each of the plurality of mobile communication terminals (3). The communication method further includes calculating (S05) a priority metric representing the priority of wireless communication between the plurality of mobile communication terminals (3) based on the future location, the maximum waiting time, and a radio wave map that statistically summarizes past radio wave conditions in each of a plurality of sub-areas included in the area (9). The communication method further includes allocating (S06) multiple radio resources, each consisting of a combination of multiple time slots and multiple frequency channels, to the plurality of mobile communication terminals based on the priority metric. The communication method further includes transmitting (S07) resource information representing the radio resources to the plurality of mobile communication terminals.

[0010] According to one embodiment, a communication program is executed by a computing device to perform a predetermined process. The process includes estimating (S03) the future location of each of a plurality of mobile communication terminals (3) that communicate wirelessly while moving within a predetermined area (9). The process further includes detecting (S02) the maximum waiting time for untransmitted packets stored in a buffer of each of the plurality of mobile communication terminals (3). The process further includes calculating (S05) a priority metric representing the priority of wireless communication for the plurality of mobile communication terminals (3) based on the future location, the maximum waiting time, and a radio wave map that statistically summarizes past radio wave conditions in each of a plurality of sub-areas included in the area (9). The process further includes allocating (S06) multiple radio resources, each consisting of a combination of multiple time slots and multiple frequency channels, to the plurality of mobile communication terminals based on the priority metric. The process further includes transmitting (S07) resource information representing the radio resources to the plurality of mobile communication terminals. [Effects of the Invention]

[0011] According to one embodiment, it is possible to improve throughput by reducing the packet discard rate in wireless communication with a mobile communication terminal in a poor communication environment. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment. [Figure 2] FIG. 2 is a block circuit diagram showing an example of the configuration of a base station according to an embodiment. [Figure 3] FIG. 3 is a block circuit diagram showing an example of the configuration of a mobile communication terminal according to an embodiment. [Figure 4] FIG. 4 is a flowchart showing an example of a configuration of the process of the communication method according to an embodiment. [Figure 5] FIG. 5 is a diagram illustrating radio resources according to an embodiment. [Figure 6] FIG. 6 is a diagram illustrating an example of a radio wave map according to an embodiment. [Figure 7] FIG. 7 is a diagram for explaining the relationship between the waiting time of an untransmitted packet and the allowable delay time. [Figure 8] FIG. 8 is a diagram for explaining the relationship between the waiting time of an untransmitted packet and the allowable delay time. [Figure 9] FIG. 9 is a diagram for explaining the relationship between the waiting time of an untransmitted packet and the allowable delay time. [Figure 10] FIG. 10 is a diagram for explaining the relationship between the waiting time of an untransmitted packet and the allowable delay time. [Figure 11] FIG. 11 is a diagram for explaining the relationship between the waiting time of an untransmitted packet and the allowable delay time. [Figure 12] FIG. 12 is a diagram for explaining a method for calculating an average data rate according to the related art. [Figure 13] FIG. 13 is a diagram for explaining a method for calculating an average data rate according to an embodiment. [Figure 14] FIG. 14 is a diagram showing an example of a computer simulation model of the operation of a communication system according to an embodiment. [Figure 15] FIG. 15 is a table showing an example of specifications of a computer simulation performed on the operation of a communication system according to an embodiment. [Figure 16] FIG. 16 is a graph showing an example of the results of a computer simulation performed on the operation of a communication system according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] With reference to the accompanying drawings, embodiments for implementing a base station, a communication method, and a communication program according to the present disclosure will be described below.

[0014] (Embodiment) As shown in FIG. 1, a communication system 1 according to one embodiment includes a base station 2 and mobile communication terminals 3A, 3B, and 3C. Hereinafter, when there is no need to distinguish between the mobile communication terminals 3A, 3B, and 3C, they may be collectively referred to as a mobile communication terminal 3. The base station 2 is located inside a predetermined area 9. The mobile communication terminal 3 is mounted on an AGV (Automated Guided Vehicle) and performs wireless communication with the base station 2. The AGV moves inside the area 9 even while the mobile communication terminal 3 is performing wireless communication. The AGV may move according to a predetermined movement plan. The movement plan determines in advance when, from where, to where, and at what speed each AGV will move.

[0015] As an example, the area 9 is an indoor environment such as a manufacturing site or warehouse where many metal objects are present. In such a case, it is expected that the communication environment between the base station 2 and the mobile communication terminal 3 will be poor. Furthermore, due to the influence of the metal objects present inside the area 9, the communication environment of the mobile communication terminal 3 mounted on the AGV will continue to change as the AGV continues to move.

[0016] In order to efficiently perform wireless communication with a plurality of mobile communication terminals 3, the base station 2 allocates wireless resources, which are combinations of time slots and frequency channels, to each mobile communication terminal 3.

[0017] As shown in Fig. 2, the base station 2 according to one embodiment may be configured as a so-called computer. In the example of Fig. 2, the base station 2 includes a bus 21, a processing unit 22, a storage unit 23, a communication unit 24, and an input / output unit 25. The bus 21 may be configured to realize communication between the processing unit 22, the storage unit 23, the communication unit 24, and the input / output unit 25.

[0018] The arithmetic device 22 executes a communication program according to an embodiment to realize the functions of a location estimation unit 221, a maximum waiting time detection unit 222, a channel condition estimation unit 223, a priority calculation unit 224, a resource allocation unit 225, and a communication unit 226. The location estimation unit 221, the maximum waiting time detection unit 222, the channel condition estimation unit 223, the priority calculation unit 224, the resource allocation unit 225, and the communication unit 226 are virtual functional blocks that execute processes realized by the arithmetic device 22 and the storage device 23 in cooperation with each other.

[0019] The position estimation unit 221 estimates the future position of each mobile communication terminal 3. The maximum waiting time detection unit 222 detects the maximum waiting time of untransmitted packets stored in the transmission buffer of each mobile communication terminal 3. Hereinafter, the transmission buffer may be simply referred to as the buffer. The channel condition estimation unit 223 estimates the future channel condition of each mobile communication terminal 3. The priority calculation unit 224 calculates a priority metric indicating the priority of each mobile communication terminal 3 for wireless communication with the base station 2. The resource allocation unit 225 allocates wireless resources to multiple mobile communication terminals 3. The communication unit 226 transmits resource information indicating the wireless resources allocated to each mobile communication terminal 3 to the corresponding mobile communication terminal 3.

[0020] The storage device 23 includes a program storage unit 231 and a data storage unit 232. The communication program may be read from an external recording medium 230 and stored in the program storage unit 231. The recording medium 230 may be a non-transitory and tangible medium. The data storage unit 232 may store movement plan information representing a movement plan and a radio wave map of the area 9. The radio wave map statistically summarizes past channel conditions in each of a plurality of sub-areas included in the area 9.

[0021] The communication device 24 performs wireless communication with each of the mobile communication terminals 3 via an antenna (not shown). The communication program may be received by the communication device 24 from the outside and stored in the program storage unit 231.

[0022] The input / output device 25 outputs information to the user and accepts operations input by the user. As an example, the input / output device 55 includes a display device that outputs images, a keyboard and / or a mouse that accepts input, etc.

[0023] 3, the mobile communication terminal 3 may be configured as a computer including a bus 31, an arithmetic unit 32, a storage device 33, a communication device 34, and an input / output device 35, similar to the base station 2. The mobile communication terminal 3 may further include a control device 36 that controls the AGV. The mobile communication terminal 3 realizes predetermined processing by the arithmetic unit 32 executing a program stored in the storage device 33. The program may be stored in the storage device 33 from an external source via a recording medium 330 or the communication device 34.

[0024] An example of the processing of the communication method according to one embodiment will be described with reference to the flowchart in Fig. 4. The processing of the communication method may be started when the base station 2 is started up. At this time, the processing of the communication method is realized by the arithmetic device 22 of the base station 2 executing a communication program.

[0025] When the flowchart of FIG. 4 starts, step S01 is executed. In step S01, the communication unit 226 of FIG. 2 controls the communication device 24 to synchronize with the mobile communication terminal 3 of FIG. 1. More specifically, the communication unit 226 transmits a synchronization signal for synchronization to the mobile communication terminal 3. The mobile communication terminal 3 starts generating packets from the time it receives the synchronization signal. At this time, the packet generation intervals may be uniform or non-uniform. Furthermore, the packet generation intervals may be different for each mobile communication terminal 3 or may be the same. For example, the packets generated by the mobile communication terminal 3 may include control signals generated by the mobile communication terminal 3 to control the operation of the AGV, sensor information acquired by a sensor mounted on the AGV, etc. Thereafter, the base station 2 can estimate the time at which each mobile communication terminal 3 generates a new packet based on the time at which the synchronization signal is transmitted and the packet generation interval set for each mobile communication terminal 3. The schedule information including the packet generation intervals may be shared in advance between the base station 2 and the mobile communication terminal 3, or may be set by the base station 2 to the mobile communication terminal 3 via a synchronization signal.

[0026] After step S01 in FIG. 4, step S02 is executed. In step S02, maximum waiting time detection unit 222 in FIG. 2 detects the maximum waiting time of untransmitted packets in the buffer for each mobile communication terminal 3 in FIG. 1. Here, an untransmitted packet in the buffer is a packet that was generated by mobile communication terminal 3, stored in the buffer, and then has not been transmitted to base station 2 and has not been discarded. The buffer of mobile communication terminal 3 may be included in storage device 33 shown in FIG. 3. The waiting time of each packet is the time elapsed since the packet was generated. The maximum waiting time of untransmitted packets in the buffer of a certain mobile communication terminal 3 is the maximum waiting time of all untransmitted packets remaining in the buffer of that mobile communication terminal 3. Note that a packet generated by mobile communication terminal 3 is discarded if transmission to base station 2 is not completed even after a predetermined allowable delay time has elapsed since the packet was generated.

[0027] After step S02 in Fig. 4, step S03 is executed. In step S03, the position estimation unit 221 in Fig. 2 estimates the future positions of the mobile communication terminals 3 in Fig. 1. More specifically, the position estimation unit 221 in Fig. 2 refers to the movement plan stored in the data storage unit 232, and estimates where in the area 9 each of the mobile communication terminals 3 shown in Fig. 1 will be located at a future time of interest.

[0028] Step S04 is executed after step S03 in Fig. 4. In step S04, channel condition estimation unit 223 in Fig. 2 estimates the channel condition of mobile communication terminal 3 in Fig. 1. More specifically, channel condition estimation unit 223 in Fig. 2 refers to the radio wave map stored in data storage unit 232, and extracts the channel condition at the future position of mobile communication terminal 3 of interest, estimated in step S03 in Fig. 4, as the estimation result of the channel condition of mobile communication terminal 3.

[0029] After step S04 in Fig. 4, step S05 is executed. In step S05, the priority calculation unit 224 in Fig. 2 calculates a priority metric for the mobile communication terminal 3 in Fig. 1. The priority metric indicates the priority order in which multiple mobile communication terminals 3 perform wireless communication with the base station 2. More specifically, the priority calculation unit 224 in Fig. 2 calculates the priority metric for each mobile communication terminal 3 based on the maximum waiting time detected in step S02 in Fig. 4 and the channel conditions estimated in step S04. A more specific method for calculating the priority metric will be described later.

[0030] Step S06 is executed after step S05 in Fig. 4. In step S06, resource allocation unit 225 in Fig. 2 allocates radio resources to each of mobile communication terminals 3 in Fig. 1. More specifically, resource allocation unit 225 in Fig. 2 preferentially allocates earlier radio resources to mobile communication terminals 3 in Fig. 1 that have higher priority metric values ​​calculated in step S05 in Fig. 4, thereby ensuring fairness in transmission opportunities and reducing the occurrence of discarded packets.

[0031] After step S06 in Fig. 4, step S07 is executed. In step S07, communication unit 226 in Fig. 2 transmits resource information indicating wireless resources to mobile communication terminal 3 in Fig. 1. More specifically, of mobile communication terminals 3 in Fig. 1, mobile communication terminals 3 to which wireless resources corresponding to the received resource information have been allocated store the resource information in data storage unit 232 in Fig. 2, while the other mobile communication terminals 3 discard the received resource information.

[0032] After step S07 in Fig. 4, step S08 is executed. In step S08, communication unit 226 in Fig. 2 receives packets transmitted by mobile communication terminal 3 in Fig. 1. More specifically, each mobile communication terminal 3 transmits untransmitted packets stored in a buffer to base station 2 during a time slot of the radio resource allocated to that mobile communication terminal 3, using the frequency band of the radio resource, and the communication unit 226 of base station 2 receives the packets transmitted in this way.

[0033] After step S08 in Fig. 4, the processing of the communication method by the base station 2 in Fig. 1 returns to step S02, and steps S02 to S08 are executed again. In step S02 in Fig. 4, which is executed for the second time or later, the maximum waiting time detection unit 222 in Fig. 2 estimates whether packets presumed to have originated from each mobile communication terminal 3 still remain in the buffer or have already been discarded, further based on packets received in step S08 executed in the past, and detects the maximum waiting time for unsent packets in the buffer.

[0034] With reference to Fig. 5, a radio resource according to one embodiment will be described. The radio resource is a combination of multiple time slots and multiple frequency channels. In the example of Fig. 5, the horizontal axis represents time, and the vertical axis represents frequency. The time from time t0 to time t1 is called the 0th time slot. Similarly, the time from time t1 to time t2 is called the 1st time slot, and the time from time t2 to time t3 is called the 2nd time slot. Generalizing with the subscript i, the time from time t i From time ti+1 The time from frequency f0 to frequency f1 is called the i-th time slot. The frequency band from frequency f0 to frequency f1 is called the 0th frequency channel. Similarly, the frequency band from frequency f1 to frequency f2 is called the 1st frequency channel, the frequency band from frequency f2 to frequency f3 is called the 2nd frequency channel, and the frequency band from frequency f3 to frequency f4 is called the 3rd frequency channel. Generalizing with the subscript j, the frequency f j to frequency f j+1 The frequency band up to is called the j-th frequency channel. In this case, the radio resource for performing radio communication using the j-th frequency channel during the i-th time slot is called the radio resource R i,j The base station 2 has one radio resource R i,j By allocating the same to one mobile communication terminal 3, it is possible to prevent crosstalk between multiple mobile communication terminals 3.

[0035] A radio wave map according to one embodiment will be described with reference to FIG. 6. The radio wave map is data that statistically summarizes past channel conditions in each of a plurality of sub-areas included in area 9. As an example, the radio wave map is a table of numerical values ​​that represent the channel conditions in each of a plurality of sub-areas obtained by dividing area 9 into a vertical and horizontal mesh. In the example of FIG. 6, the numerical values ​​representing the channel conditions are expressed by the density of the hatching. In this embodiment, only the channel conditions determined by the position in each sub-area included in area 9 are estimated in step S04 of FIG. 4. However, this is merely an example and does not limit this embodiment.

[0036] The maximum waiting time for unsent packets in the buffer according to one embodiment will be described with reference to Figures 7, 8, 9, 10, and 11. In each of Figures 7 to 11, the upper graph shows an example of the change over time in the number of packets in the buffer, and the lower graph shows the change over time in the maximum waiting time for packets corresponding to the upper graph, or more precisely, an example of the change over time in the number of unsent packets in the buffer.

[0037] 7 shows a packet generation time t , which is shared between the base station 2 and the mobile communication terminal 3 at the time of step S01 in FIG. 4, at which the mobile communication terminal 3 generates a packet. g1 , t g2 , t g3 , t g4 , t g5 and the allowable delay time T ADT When generalizing with subscript i, packet occurrence time t g(i) , to the next packet occurrence time t g(i+1) The time until the packet generation interval T gen is equal to.

[0038] FIG. 8 shows the mobile communication terminal 3 receiving the first packet at the time t g1 The graph in the upper right of Figure 8 shows the time change of the number of packets in the buffer when the first packet is generated at t g1 After, the number of packets in the buffer is 1. Also, as shown in the bottom graph of Figure 8, the maximum waiting time of a packet is equal to the waiting time of the first packet and increases over time.

[0039] FIG. 9 shows the time when the mobile communication terminal 3 completes the first packet transmission t t1 After completing the transmission of the first packet at time t g2 The second packet is generated at time t , and the third packet is generated at time t before the second packet is completely transmitted. g3 The third packet is generated at time t t2 This shows the number of packets in the buffer when the transmission of the second packet is completed and the maximum waiting time for a packet.

[0040] As shown in the upper graph of Fig. 9, the number of packets in the buffer increases by the first packet transmission completion time t t1 t g2 t g3 9, the maximum packet waiting time increases to 3. Also, as shown in the bottom graph of FIG. 9, the maximum packet waiting time increases from the first packet transmission completion time tt1 t g2 The value starts increasing from tt2 and decreases to a predetermined value greater than 0 at the time tt2 when the second packet transmission is completed. The value is equal to the waiting time of the third packet and is set to t g3 to the second packet transmission completion time t t2 Thus, the time until the third packet occurs t g3 to the second packet transmission completion time t t2 In the period up to , the maximum waiting time of a packet is equal to the waiting time of the second packet, which occurred first, of the second packet and the third packet that are untransmitted packets in the buffer.

[0041] In the examples so far, the waiting times of the first packet and the second packet are both within the allowable delay time T ADT Note that the time from when the first packet is generated until the transmission is completed is different from the time from when the second packet is generated until the transmission is completed because the channel conditions change as the mobile communication terminal 3 moves by the AGV.

[0042] FIG. 10 shows the mobile communication terminal 3 receiving the fourth packet at the time t g4 After generating the fourth packet at t , the third packet is discarded at time t before the third packet is completely transmitted. d3 The waiting time of the third packet is the allowable delay time T ADT This shows the number of packets in the buffer when the third packet is discarded because the buffer size has reached 1, and the maximum waiting time for the packet.

[0043] As shown in the upper graph of FIG. 10, the number of packets in the buffer is calculated based on the fourth packet occurrence time t g4 The third packet is discarded at the time t d310, the maximum waiting time of a packet decreases from 2 to 1 at the time t t2 From the third packet discard time t d3 The waiting time for the third packet is equal to the time t d3 After the third packet is discarded at , the waiting time is equal to the waiting time of the fourth packet.

[0044] FIG. 11 shows the state in which the mobile communication terminal 3 receives the fifth packet at the time t g5 After generating the fifth packet at t t4 This shows the number of packets in the buffer when the transmission of the fourth packet is completed and the maximum waiting time for a packet.

[0045] As shown in the upper graph of FIG. 11, the number of packets in the buffer is the same as the number of packets in the buffer at the fifth packet occurrence time t g5 The fourth packet transmission completion time t t4 t , the maximum packet waiting time decreases from 2 to 1 at the third packet discard time t d3 From the fourth packet transmission completion time t t4 The waiting time is equal to the waiting time for the fourth packet until the fourth packet is transmitted, and after the fourth packet is transmitted, the waiting time is equal to the waiting time for the fifth packet.

[0046] The base station 2 calculates the time variation of the number of packets in the buffer and the maximum waiting time of packets shown in the examples of FIGS. 7 to 11 for each mobile communication terminal 3, based on the time synchronized with each mobile communication terminal 3 and the packet occurrence interval T gen and the packets received by base station 2.

[0047] A method for calculating the priority metric according to one embodiment will be described. In region 9, the instantaneous data rate R at a certain time t is calculated. i (t) can be calculated using the following formula (1).

number

[0048] The channel gain γ of the link between the i-th mobile communication terminal 3 and the base station 2 at time t i (t) can be calculated using the following formula (2).

number

[0049] The priority metric PM is the instantaneous data rate R calculated by the formula 1. i (t) is the average data rate R i ave This is a value normalized by (t) and can be calculated using the following formula (3).

number

[0050] In step S06 of FIG. 4, among the wireless resources that have not yet been assigned to any mobile communication terminal 3, the number i of the mobile communication terminal 3 to which the wireless resource with the earliest time slot is assigned is determined. * is calculated as shown in the following formula 4.

number

[0051] The radio wave map used in step S04 in Fig. 4 is a map that divides the area 9 in which the mobile communication terminals 3 operate into meshes and statistically summarizes past channel conditions. By using the radio wave map, it becomes possible to estimate the channel conditions experienced by each mobile communication terminal 3 based on the route that each mobile communication terminal 3 takes based on the movement plan. However, the channel gain γ that can be estimated using the radio wave map i stats (t) is the path loss loss "G" other than the fading loss as shown in the following "Equation 5". pathloss (d 3D ) and shadowing loss "G shadowing (t)"

number

[0052] Average data rate R taking into account future data rates estimated using radio wave maps i ave (t) can be calculated using the following formula (6).

number

[0053] In this embodiment, the time length T wide The remaining allowable delay time T RADT The remaining allowable delay time T RADT is the waiting time of the oldest packet among the unsent packets remaining in the buffer, as the tolerable delay time T ADT In this embodiment, in order to complete as many transmissions of the oldest packets as possible for each mobile communication terminal 3, the current time T Cur The remaining allowable delay time T RADTThe priority metric PM is calculated by taking into account the average value of the data rate for the period up to the time the data rate has elapsed. As shown in the first term on the right side of the above "Equation 6," the allowable delay time for calculating the past average data rate is T ADT Fix it to.

[0054] The results of a computer simulation of a communication method by the base station 2 according to one embodiment will be described with reference to FIGS.

[0055] Fig. 14 is a diagram showing an example of the computer simulation model. As shown in Fig. 14, area 9 is a square closed space with a side length A, base station 2 is located inside area 9, and a total of three mobile communication terminals 3A, 3B, and 3C communicate wirelessly with base station 2 while moving at a constant speed between points C1, C2, C3, and C4.

[0056] 15 is a table showing an example of the specifications of the computer simulation. As shown in FIG. 15, the length A is 50 m, the number I of mobile communication terminals 3 is 3, the moving speed V of the mobile communication terminals 3 is 2 km / h, the transmission power P of each mobile communication terminal 3 is 20 dBm, the number of antennas provided in each mobile communication terminal 3 is 3, the noise power spectral density N0 is −174 dBm / Hz, the bandwidth B of each wireless resource is 10 MHz, the shadowing standard deviation is 5.9 dB, and the packet occurrence interval T gen is 0.03 seconds, and the allowable delay time T ADT is 0.9 seconds.

[0057] Fig. 16 is a graph showing an example of the results of the computer simulation. Fig. 16 includes a total of three graphs G1, G2, and G3. In all of the graphs G1, G2, and G3, the horizontal axis represents the generated packet size and the vertical axis represents the packet discard rate. The first graph G1 shows the results when wireless communication is performed using the PF method, the second graph G2 shows the results when wireless communication is performed using the PPF method, and the third graph G3 shows the results when wireless communication is performed according to this embodiment.

[0058] 16, regardless of the packet size generated, the packet discard rate in wireless communication according to this embodiment is lower than the packet discard rates in the PF method and the PPF method. Furthermore, the larger the packet size generated, the greater the difference in packet discard rate. For example, when the packet size generated is 16 Mbits, it was confirmed that the packet discard rate in this embodiment is 4% or more lower than the packet discard rate in the PF method and the PPF method.

[0059] As described above, according to this embodiment, the priority metric PM is calculated based on the remaining allowable delay time T RADT By taking this into consideration, the packet discard rate can be reduced and throughput can be improved.

[0060] The invention made by the inventor has been specifically described above based on the embodiments, but it goes without saying that the present invention is not limited to the embodiments and can be modified in various ways without departing from the spirit of the invention. Furthermore, the features described in the embodiments can be freely combined within the scope of technical compatibility. [Explanation of symbols]

[0061] 1. Communication Systems 2 base station 21 Bus 22 Arithmetic unit 221 Position estimation part 222 Maximum waiting time detector 223 Channel Condition Estimation Unit 224 Priority calculation unit 225 Resource Allocation Department 226 Communications Department 23 Storage device 230 Recording Media 231 Program Memory Unit 232 Data storage unit 24 Communication equipment 25 Input / Output Devices 3, 3A, 3B, 3C mobile communication terminal 31 Bus 32 Arithmetic unit 33 Storage device 330 Recording Media 34 Communication equipment 35 Input / Output Devices 36 Control device 9 areas A. Length B. Bandwidth C1, C2, C3, C4 points f0, f1, f2, f3 frequency G1, G2, G3 graphs I Number N0 noise power spectral density P transmit power R 0,0 , R 0,1 , R 0,2 , R 1,0 , R 1,1 , R 1,2 , R 2,0 , R 2,1 , R 2,2 , R 3,0 , R 3,1 , R 3,2 Radio Resources t0, t1, t2, t3 time T ADT Allowable delay time t Cur Current time t d3 Packet discard time t1, t g2 , t g3 , t g4 , t g5 Packet generation time T gen Packet occurrence interval t t1 , t t2 , t t4 Packet sending time T RADT Remaining allowable delay time V Movement speed

Claims

1. a priority calculation unit that calculates a priority metric representing a priority order for the plurality of mobile communication terminals to perform wireless communication based on future positions estimated from the future positions of each of the plurality of mobile communication terminals that perform wireless communication while moving within a predetermined area, a radio wave map that statistically aggregates past channel conditions in each of a plurality of sub-areas included in the area, and a maximum waiting time for untransmitted packets stored in a buffer in each of the plurality of mobile communication terminals; a resource allocation unit that allocates a plurality of radio resources, each combining a plurality of time slots and a plurality of frequency channels, to the plurality of mobile communication terminals based on the priority metric; a communication unit that transmits resource information representing the wireless resources to the plurality of mobile communication terminals; Equipped with Base station.

2. 2. The base station according to claim 1, a maximum waiting time detection unit that detects a maximum waiting time of packets in a buffer of each of the plurality of mobile communication terminals based on a packet generation interval at which each of the plurality of mobile communication terminals generates a packet and a time at which the latest packet is received from each of the plurality of mobile communication terminals; Further equipped Base station.

3. 2. The base station according to claim 1, a position estimation unit that estimates the future positions based on movement plans assigned to the plurality of mobile communication terminals; Further equipped Base station.

4. 2. The base station according to claim 1, a channel condition estimation unit that estimates future channel conditions for each of the plurality of mobile communication terminals based on the future positions of each of the plurality of mobile communication terminals and the radio wave map; Furthermore, the priority calculation unit calculates the priority metric based on an average data rate from a current time until a remaining allowable delay time, which is calculated by subtracting a waiting time of the oldest packet remaining in a buffer of each of the plurality of mobile communication terminals from an allowable delay time, has elapsed; Base station.

5. 2. The base station according to claim 1, The communication unit further receives a packet transmitted by the mobile communication terminal using the radio resource. Base station.

6. Estimating future positions of each of a plurality of mobile communication terminals that perform wireless communication while moving within a predetermined area; Detecting a maximum waiting time of untransmitted packets stored in a buffer in each of the plurality of mobile communication terminals; calculating a priority metric representing a priority order for the plurality of mobile communication terminals to perform the wireless communication based on the future positions, the maximum waiting time, and a radio wave map that statistically summarizes past radio wave conditions in each of a plurality of sub-areas included in the area; Allocating a plurality of radio resources, each of which is a combination of a plurality of time slots and a plurality of frequency channels, to the plurality of mobile communication terminals based on the priority metric; transmitting resource information representing the wireless resources to the plurality of mobile communication terminals; Contains Communication method.

7. A communication program for causing a computing device to execute a predetermined process, The process comprises: Estimating future positions of each of a plurality of mobile communication terminals that perform wireless communication while moving within a predetermined area; Detecting a maximum waiting time of untransmitted packets stored in a buffer in each of the plurality of mobile communication terminals; calculating a priority metric representing a priority order for the plurality of mobile communication terminals to perform the wireless communication based on the future positions, the maximum waiting time, and a radio wave map that statistically summarizes past radio wave conditions in each of a plurality of sub-areas included in the area; Allocating a plurality of radio resources, each of which is a combination of a plurality of time slots and a plurality of frequency channels, to the plurality of mobile communication terminals based on the priority metric; transmitting resource information representing the wireless resources to the plurality of mobile communication terminals; Contains Communications program.

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