JP5824311B2 - Wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication system that distributes a flow including content from a streaming server to a terminal wirelessly connected to a base station.

  As next-generation high-speed mobile communication systems, WiMAX (Worldwide Interoperability for Microwave Access), LTE (Long Term Evolution), XGP (eXtended Global Platform) and the like are attracting international attention. In these communication systems, OFDMA (Orthogonal Frequency Division Multiple Access), which is a multiple access system that is resistant to multipath fading and can efficiently use band resources, is used.

  In OFDMA, a plurality of subcarriers are grouped together to form a subchannel, and each subchannel is assigned to each terminal for each time slot, whereby a plurality of terminals can communicate simultaneously (see Patent Document 1). In this case, each subcarrier is modulated by a modulation scheme such as BPSK, QPSK, 16QAM, 64QAM, and the data carried by each subcarrier is encoded by 1/2, 2/3, 3/4, etc. Error correction coding at a rate.

  Allocation of subcarriers to subchannels is usually performed by a technique such as FUSC, PUSC, or AMC. FUSC and PUSC are techniques for allocating subcarriers having different frequencies to one subchannel, and can obtain a frequency diversity effect. On the other hand, AMC is a technique for assigning subcarriers that are close in frequency to one subchannel. The modulation scheme and coding rate are adaptively selected according to the propagation environment between the base station and each terminal, and are determined after assignment of subchannels to terminals is determined.

  In such OFDMA, various methods for efficiently allocating band resources to terminals have been proposed.

  For example, in Patent Document 2, the number of subcarriers that is equal to or higher than the required transmission rate of each terminal is determined, and a subcarrier to which transmission data is allocated for each communication partner is selected based on the line quality information for the number of subcarriers. I am doing so.

JP 2010-50967 A JP 2010-16881 A

  However, in the bandwidth resource allocation method disclosed in Patent Document 2, subcarriers each having a number of subcarriers satisfying the transmission rate required by the terminal side are allocated to each terminal. For example, transmission data distributed to a certain terminal Is smaller than the transmission rate of the band resource allocated to the terminal, there is a possibility that an extra subcarrier may be allocated to the terminal.

  The present invention has been made to solve the above-described problems, and each of a flow during distribution including content distributed from the streaming server and a new flow including content newly distributed from the streaming server It is an object of the present invention to provide a wireless communication system capable of efficiently allocating bandwidth resources for each flow based on the data rate required to increase the communication capacity of the entire system.

Wireless communication system according to the present invention includes a base station that connects terminal and non-linear, and the streaming server content is stored that is included in the flow to be delivered to the terminal, acquired from the streaming server, is required to the flow A bandwidth resource management server for allocating bandwidth resources to the flow based on the data rate, the bandwidth resource management server acquires propagation environment information for each subcarrier from the terminal, and based on the propagation environment information, A transmission rate calculation unit that calculates a transmission rate for each subcarrier; a rate table storage unit that stores the transmission rate calculated for each subcarrier as a rate table; and a predetermined subcarrier assigned to the streaming server. To the terminal And a new flow newly delivered from the streaming server to the terminal, the total transmission rate of the subcarriers to be assigned to each flow is requested to each flow based on the rate table. Band resources for selecting the combination of subcarriers that is equal to or higher than each of the data rates and for which the total number of subcarriers allocated to each flow is the smallest, and for assigning the subcarriers of the selected combination to each flow An allocation unit, and a distribution flow table storage unit that stores the data rate of the distribution flow acquired from the streaming server as a distribution flow table, and the streaming server detects the end of distribution of the distribution flow Then, the bandwidth resource management service When the distribution resource management server receives the distribution completion notification, the band resource management server deletes data corresponding to the in-distribution flow related to the distribution completion notification from the distribution flow table, and The resource allocation unit reallocates the subcarriers to the in-distribution flow based on the remaining data rate of the distribution flow table stored in the distribution flow table storage unit and the transmission rate of the rate table. The base station transmits the in-distribution flow and the new flow on each of the subcarriers allocated by the band resource management server.

  In the wireless communication system, when the streaming server detects a change in the data rate of the flow under distribution, the streaming server transmits a rate change notification to the bandwidth resource management server, and the bandwidth resource management server sends the rate change notification. When received, change the data rate of the distribution flow table corresponding to the flow under distribution related to the rate change notification, the bandwidth resource allocation unit, the data rate of the changed distribution flow table, The subcarriers are reassigned to the in-distribution flow based on the transmission rate of the rate table.

  In the wireless communication system, the bandwidth resource allocation unit is updated with the data rate of the distribution flow table when the transmission rate of the rate table is updated based on the propagation environment information acquired from the terminal. Further, the subcarriers are reassigned to the in-distribution flow based on the transmission rate of the rate table.

  In the wireless communication system, the band resource allocation unit allocates the band resource based on the subcarriers and time slots to the delivering flow and the new flow.

  In the wireless communication system of the present invention, a sub flow to be assigned to each flow is assigned to each of a flow being delivered including content to which a predetermined subcarrier is assigned and a new flow containing content newly delivered from a streaming server. Select the subcarrier combination that makes the total of the carrier transmission rates equal to or higher than the data rates required for each flow, and that minimizes the total number of subcarriers assigned to each flow. By allocating to the flow, the flow can be distributed by efficiently using the band resource. As a result, the substantial communication capacity of the entire system can be increased. In addition, the bandwidth resource management server performs the bandwidth resource allocation process, thereby reducing the load on the base station.

It is a schematic block diagram of the radio | wireless communications system which concerns on this embodiment. FIG. 2 is a configuration block diagram of a streaming server and a bandwidth resource management server that constitute the wireless communication system shown in FIG. 1. It is explanatory drawing of the rate table memorize | stored in the rate table memory | storage part of the band resource management server shown in FIG. It is explanatory drawing of the delivery flow table memorize | stored in the delivery flow table memory | storage part of the band resource management server shown in FIG. 5 is a timing chart for creating or updating a rate table of a band resource management server in the wireless communication system according to the present embodiment. 6 is a timing chart for allocating and distributing band resources to a new flow in the wireless communication system according to the present embodiment. FIG. 7A is an explanatory diagram of a distribution flow table in which new flow data is registered, and FIG. 7B is an explanatory diagram of a distribution flow table in which the new flow distribution is completed and the new flow data is deleted. 4 is a timing chart in which a bandwidth resource is allocated and distributed to each of a distribution flow and a new flow in the wireless communication system according to the present embodiment. FIG. 9A is an explanatory diagram of a distribution flow table in which new flow data is registered in addition to the data of the flow being distributed. FIG. 9B is the distribution of the flow being distributed ended and the data of the flow being distributed is deleted. It is explanatory drawing of a delivery flow table.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram of a wireless communication system 10 according to the present embodiment. The wireless communication system 10 includes a base station 14 (BS) connected to the IP network 12, and a plurality of terminals 16a to 16c (MS) including mobile phones and personal computers connected wirelessly within a communication area of the base station 14. The content included in the flow having a predetermined data rate is stored, the streaming server 18 that distributes the flow to the terminals 16a to 16c via the IP network 12 and the base station 14, and the wireless in the communication area of the base station 14 A bandwidth resource management server 20 that manages bandwidth resources for communication and allocates bandwidth resources for each flow based on a data rate required for a flow distributed from the streaming server 18 and an AAA (Authentication Authorization Accounting) server are included. CSN (Connectivity
Service Network) 22.

  Here, “flow” means the flow of data including the content to be distributed, and “content” means data such as video and music that is the distribution target stored in the streaming server.

  FIG. 2 is a configuration block diagram of the streaming server 18 and the band resource management server 20 that constitute the wireless communication system 10 shown in FIG.

  The streaming server 18 includes a content storage unit 24 that stores content, and a distribution destination information storage unit 26 that stores distribution destination information for specifying the terminals 16a to 16c that are distribution destinations for distributing the content. Attribute information indicating the type of content, a flow identifier for identifying a flow including the content, a data rate required for each flow, and the like is added to the content stored in the content storage unit 24. The content includes not only fixed bit rate format content in which the required data rate is fixed, but also variable bit rate format content in which the required data rate is variable.

  In addition, the streaming server 18 includes a transmission control unit 28, and a content storage unit 24 and a delivery destination information storage unit 26 are connected to the transmission control unit 28. The transmission control unit 28 performs bandwidth resource management on the attribute information of the content stored in the content storage unit 24 and the distribution destination information that is information of the terminals 16a to 16c that distribute the content stored in the distribution destination information storage unit 26. While performing control which transmits to the server 20, control which transmits the flow and delivery destination information containing a content to the base station 14 is performed.

  The band resource management server 20 calculates a transmission rate based on CINR (Carrier-to-Interference-plus-Noise Ratio) which is propagation environment information indicating a communication state between each terminal 16a to 16c and the base station 14. The transmission rate calculation part 30 and the rate table memory | storage part 32 which memorize | stores the transmission rate calculated for every subcarrier of each terminal 16a-16c as the rate table 40 (FIG. 3) are provided. Further, the bandwidth resource management server 20 acquires from the streaming server 18, the data rate required for the flow being distributed to the terminals 16 a to 16 c (hereinafter referred to as “flow during distribution”), and the terminals 16 a to 16 c. The distribution flow table storage unit 34 stores a distribution flow table 42 (FIG. 4) including a data rate required for a flow newly distributed to 16c (hereinafter referred to as “new flow”). Furthermore, the band resource management server 20 includes a band resource allocation unit 36 that allocates band resources to each of the delivering flow and the new flow distributed from the streaming server 18, and a transmission / reception control unit 38.

  The transmission rate calculation unit 30 acquires the CINR for each subcarrier transmitted from the terminals 16a to 16c via the base station 14 at predetermined time intervals via the transmission / reception control unit 38, and acquires the acquired CINR and the subcarriers. Based on the modulation scheme and coding rate MCS (Modulation and Coding Scheme), the transmission rate for each subcarrier of each terminal 16a to 16c is calculated.

  The bandwidth resource allocation unit 36 allocates bandwidth resources to each of the delivering flow and the new flow. That is, the bandwidth resource allocation unit 36 distributes based on the data rate of the distribution flow table 42 stored in the distribution flow table storage unit 34 and the transmission rate of the rate table 40 stored in the rate table storage unit 32. A combination of subcarriers in which the total transmission rate of subcarriers assigned to each flow that is a middle flow and a new flow is equal to or higher than each data rate required for each flow, and the total number of subcarriers assigned to each flow is minimized. And assign the selected combination of subcarriers and time slots to each flow as band resources.

  A transmission rate calculation unit 30, a distribution flow table storage unit 34, and a band resource allocation unit 36 are connected to the transmission / reception control unit 38. The transmission / reception control unit 38 performs control to receive the attribute information and distribution destination information of the flow to be distributed from the streaming server 18 and performs control to receive the CINR for updating the rate table 40 from the terminals 16a to 16c. . Further, the transmission / reception control unit 38 makes an inquiry to the AAA server in the CSN 22 about the base station 14 in which the terminals 16a to 16c, which are flow distribution destinations, make network entries, and receives the base station information. Further, the transmission / reception control unit 38 performs control to transmit the band resource allocation pattern allocated to each flow by the band resource allocation unit 36 to the base station 14. The base station 14 to which the allocation pattern is transmitted uses the bandwidth resource allocation unit 36 of the bandwidth resource management server 20 to distribute the flow being delivered from the streaming server 18 and the new flow newly delivered from the streaming server 18. Transmission is performed using a band resource composed of assigned subcarriers and time slots.

  FIG. 3 is an explanatory diagram of the rate table 40 stored in the rate table storage unit 32. Rate table 40 includes terminals 16a to 16c, base station 14, subcarriers f1 to f3, modulation schemes and coding rates MCS (QPSK1 / 2, 16QAM3 / 4, 64QAM3 / 4) of subcarriers f1 to f3. Is a table in which transmission rates calculated based on CINR for each subcarrier transmitted from the terminals 16a to 16c at predetermined time intervals are set for the allocation patterns 1 to 27 composed of the combinations of Created by. For example, the allocation pattern 1 represents that the transmission rate calculated by the transmission rate calculation unit 30 is 11.5 Mbps when the MCS of the subcarrier f1 between the terminal 16a and the base station 14 is QPSK1 / 2. ing. The rate table 40 is updated at predetermined time intervals by the transmission rate calculation unit 30 based on CINR transmitted from the terminals 16a to 16c. Note that the number of subcarriers is three for the sake of simplicity, but is not limited to this number.

  FIG. 4 is an explanatory diagram of the distribution flow table 42 stored in the distribution flow table storage unit 34. The distribution flow table 42 includes a flow identifier for identifying a flow under distribution or a new flow received from the streaming server 18, a data rate required for each flow (for example, xx Mbps), and a base station 14 through which each flow passes. Is a table in which base station information for identifying and distribution destination information for identifying the terminals 16a to 16c to be distributed are set, and is created by the transmission / reception control unit 38. The flow identifier and the data rate are included in the attribute information added to the flow.

  Next, the operation of the wireless communication system 10 according to the present embodiment will be described. FIG. 5 is a timing chart for creating or updating the rate table 40 of the band resource management server 20 in the wireless communication system 10 according to the present embodiment. FIG. 6 is a timing chart for allocating and distributing band resources to a new flow in the wireless communication system 10 according to the present embodiment. 7A is an explanatory diagram of the distribution flow table 42 in which new flow data is registered, and FIG. 7B is an explanatory diagram of the distribution flow table 42 in which the distribution of the new flow is completed and the new flow data is deleted. FIG. 8 is a timing chart for allocating and distributing band resources to each of the in-distribution flow and the new flow in the wireless communication system 10 according to the present embodiment. FIG. 9A is an explanatory diagram of the distribution flow table 42 in which new flow data is registered in addition to the data of the distribution flow. FIG. 9B is the distribution of the distribution flow is completed and the distribution flow data is deleted. It is explanatory drawing of the distribution flow table 42.

[Create (update) rate table 40]
First, the creation or update processing of the rate table 40 will be described based on the timing chart shown in FIG.

  The terminals 16a to 16c transmit the measured CINR for all the subcarriers f1 to f3 allocated to the base station 14 to the band resource management server 20 via the base station 14 at predetermined time intervals (step S1). .

  When the band resource management server 20 receives the CINR transmitted from each of the terminals 16a to 16c by the transmission / reception control unit 38, the transmission rate calculation unit 30 determines that all the subcarriers f1 to f3 and the wireless communication system 10 are based on the CINR. The transmission rate for all the combinations with MCS supported by is calculated (step S2). Note that the CINR value is small. For example, in the case of 64QAM, which is a modulation method with a high modulation degree as MCS, the transmission rate may become zero.

  The transmission rate calculation unit 30 creates the rate table 40 using the calculated transmission rate, or updates the transmission rate of the rate table 40 when the transmission rate is already set (step S3). The created or updated rate table 40 is stored in the rate table storage unit 32 as allocation patterns 1 to 27 including the terminals 16a to 16c, the base station 14, the subcarriers f1 to f3, the MCS, and the transmission rate. In addition, since the propagation environment between the base station 14 and the terminals 16a to 16c changes according to the position of the moving terminals 16a to 16c and the radio wave conditions, the rate table 40 is transmitted from the terminals 16a to 16c. Based on CINR, it is updated every predetermined time.

[Band resource allocation for new flows]
Next, based on the timing chart shown in FIG. 6, processing for assigning bandwidth resources to new flows newly distributed from the streaming server 18 using the rate table 40 updated every predetermined time will be described.

  When there is a new flow distribution request from the terminals 16a to 16c via the base station 14 (step S11), the streaming server 18 distributes the information of the terminals 16a to 16c, which is the distribution destination information included in the distribution request information, to the distribution destination. The information is stored in the information storage unit 26 and a trigger for distributing a new flow is generated (step S12). Note that this trigger may be generated at a timing when the new flow is unilaterally distributed from the streaming server 18 to the terminals 16a to 16c.

  When a trigger for distributing a new flow occurs, the transmission control unit 28 of the streaming server 18 transmits a subcarrier allocation request notification for allocating a subcarrier to the new flow to the bandwidth resource management server 20 (step S13). That is, the streaming server 18 selects the content of the new flow designated by the distribution request from the content storage unit 24, and is requested by the flow identifier and the new flow for identifying the new flow added to the selected content. The attribute information including the data rate and the distribution destination information specifying the distribution destination terminals 16a to 16c read from the distribution destination information storage unit 26 are transmitted to the bandwidth resource management server 20 as a subcarrier allocation request notification.

  When the transmission / reception control unit 38 of the bandwidth resource management server 20 receives the subcarrier allocation request notification for the new flow, based on the distribution destination information, the terminals 16a to 16c requesting the distribution of the new flow have entered the network entry. The CSN 22 is inquired about base station information for specifying the station 14. Next, the transmission / reception control unit 38 creates a distribution flow table 42 including a flow identifier for identifying a new flow, a data rate required for the new flow, base station information, and distribution destination information of the new flow. Register in the flow table storage unit 34 (step S14). FIG. 7A exemplifies data in the distribution flow table 42 of a new flow in which the flow identifier is 1, the data rate is 20 Mbps, the base station information is registered as the base station 14, and the distribution destination information is registered as the terminal 16a.

  Next, the bandwidth resource allocation unit 36 of the bandwidth resource management server 20 distributes the rate table 40 created in step S3 (FIG. 5) or updated and stored in the rate table storage unit 32 in step S14. Using the new flow distribution flow table 42 registered in the flow table storage unit 34, band resource allocation processing for the new flow is performed (step S15).

  That is, the band resource allocating unit 36 specifies the data rate required for the new flow registered in the distribution flow table 42 (FIG. 7A), the information specifying the distribution destination base station 14 and the terminals 16a to 16c, and the base station. 14 and the transmission rate of each subcarrier in the rate table 40 (FIG. 3) corresponding to the terminals 16a to 16c, the total transmission rate is equal to or higher than the data rate, and the number of subcarriers allocated to the new flow The combination of subcarriers that minimizes the total is selected. Then, a band resource composed of the selected combination of subcarriers and a predetermined time slot is allocated to the new flow.

  For example, in step S14, as shown in FIG. 7A, a new flow specified by the flow identifier 1 is registered in the distribution flow table 42 and requested for a new flow to be distributed to the terminal 16a wirelessly connected to the base station 14. Assume that the data rate is 20 Mbps. In such a case, all combinations of subcarriers in which the total transmission rate selected from the allocation patterns 1 to 9 of the rate table 40 is 20 Mbps or more, for example, combinations of allocation patterns 1 and 4, combinations of allocation patterns 1 and 7, A combination of the allocation patterns 4 and 7 is an allocation candidate. Therefore, the band resource allocation unit 36 selects an allocation pattern that is a combination of subcarriers that minimizes the number of subcarriers from candidates for allocation to a new flow.

  By selecting the combination of subcarrier, time slot and MCS in this way, the minimum necessary bandwidth resources can be allocated to the new flow. As a result, the communication capacity of the entire system can be increased. In addition, since the bandwidth resource management server 20 performs the bandwidth resource allocation processing, an effect of reducing the load on the base station 14 for the allocation processing can be obtained.

  The band resource allocation pattern determined as described above is transmitted from the transmission / reception control unit 38 to the base station 14 (step S16). The base station 14 sets subcarriers, time slots, and MCSs for the new flow according to the received allocation pattern, and determines a band resource (step S17). Next, after determining the band resource, the base station 14 transmits an acknowledge signal ACK to the band resource management server 20 (step S18).

  The band resource management server 20 that has received the acknowledge signal ACK from the base station 14 instructs the streaming server 18 to distribute a new flow to the terminals 16a to 16c (step S19). Upon receiving the distribution instruction, the streaming server 18 distributes the new flow to the base station 14. The base station 14 transmits a new flow to the terminals 16a to 16c to the predetermined terminals 16a to 16c using the allocated band resources (subcarriers and time slots) (step S20).

  On the other hand, the propagation environment between the base station 14 and the terminals 16a to 16c changes according to the position of the moving terminals 16a to 16c and the radio wave conditions. Therefore, the band resource allocation unit 36 distributes a rate table 40 in which a transmission rate is updated every predetermined time and a distribution flow table 42 for a distribution flow that is distributed as a new flow and then distributed. In the same manner as in step S15, the bandwidth resource is reassigned to the in-distribution flow at a predetermined timing, for example, when the rate table 40 is updated (step S21). The reassigned band resource allocation pattern is transmitted to the base station 14 (step S22). The base station 14 changes the band resources of the terminals 16a to 16c according to the received new allocation pattern (step S23). Next, the base station 14 transmits an acknowledge signal ACK to the band resource management server 20 after changing the band resource (step S24). Note that the processing of steps S21 to S24 is repeatedly performed, for example, every time the rate table 40 is updated.

  The content distributed from the streaming server 18 may be a fixed bit rate or a variable bit rate. When the content is a variable bit rate, the following processing is performed as the extended function of steps S13 to S15 described above. In other words, when the streaming server 18 detects a change in the data rate of the delivering flow that has been delivered as a new flow including the content and then is being delivered, the change is triggered by the change in the data rate of the delivering flow. A rate change notification for notifying the change is transmitted to the bandwidth resource management server 20 as an extended function of the new carrier subcarrier allocation request notification processing in step S13. In this case, similarly to the subcarrier allocation request notification, the rate change notification is added with attribute information including a flow identifier for identifying the flow being delivered and a new data rate. Receiving the rate change notification, the bandwidth resource management server 20 uses the distribution flow table 42 corresponding to the in-distribution flow specified by the flow identifier included in the attribute information as an extension function of the creation processing of the distribution flow table 42 in step S14. Change the data rate. Next, the band resource allocation unit 36 uses the distribution flow table 42 with the updated data rate and the data rate table 40 as an extended function of the band resource allocation process for the new flow in step S15, and uses each of the terminals 16a to 16b. By reallocating the band resource to 16c, it is possible to dynamically optimize the use efficiency of the band resource in response to the change in the data rate of the flow being delivered.

  In this way, when the data rate of the flow being delivered is changed based on the rate table 40 updated every predetermined time, or in accordance with the position and radio wave status of the moving terminals 16a to 16c, the delivery is appropriately performed. By reallocating the band resource of the middle flow, the band resource can be efficiently used and the optimum communication state can be maintained. In addition, since appropriate bandwidth resources are efficiently allocated to the flow being delivered, the communication capacity of the entire system can be increased. Furthermore, since the bandwidth resource management server 20 performs the bandwidth resource allocation processing, an effect of reducing the load on the base station 14 with respect to the allocation processing can be obtained.

  Next, when the streaming server 18 detects the end of distribution of the flow being distributed, the streaming server 18 generates a distribution end trigger (step S25), and transmits a distribution end notification of the flow being distributed from the transmission control unit 28 to the bandwidth resource management server 20. (Step S26). The distribution end notification includes a flow identifier for identifying the distribution flow for which distribution has ended.

  When the transmission / reception control unit 38 of the bandwidth resource management server 20 receives the distribution end notification, the transmission / reception control unit 38 distributes, from the distribution flow table storage unit 34, data corresponding to the distribution-in-distribution flow specified by the flow identifier of the distribution end notification. Delete from the table 42 (step S27). FIG. 7B shows a distribution flow table 42 from which data corresponding to a distribution-completed flow identified by the flow identifier 1 in FIG. 7A has been deleted. Therefore, the band resource allocation unit 36 can allocate the band resource only to the currently distributed flow or the new flow that is currently distributed when performing the band resource allocation process next time.

[Band resource allocation for current flow and new flow]
Next, based on the timing chart shown in FIG. 8, band resource allocation processing in the case where a flow being delivered from the streaming server 18 is being delivered and a new flow is delivered will be described.

  Similar to the processing in steps S11 to S14 (FIG. 6) described above, when there is a new flow distribution request (step S31), the streaming server 18 stores the distribution destination information in the distribution destination information storage unit 26, and also creates a new flow. A trigger for distributing the flow is generated (step S32).

  When a trigger for distributing a new flow occurs, the transmission control unit 28 of the streaming server 18 transmits a subcarrier allocation request notification of the new flow to the bandwidth resource management server 20 (step S33). When receiving the subcarrier allocation request notification, the band resource management server 20 additionally registers data corresponding to the new flow in the distribution flow table 42 of the distribution flow table storage unit 34 (step S34). For example, in FIG. 9A, if the data specified by the flow identifier 1 is data corresponding to the in-distribution flow registered in the process of step S14 (FIG. 6), the data corresponding to the new flow is the flow identifier 2 Is added to the distribution flow table 42 as the data specified in (1).

  Next, the bandwidth resource allocation unit 36 of the bandwidth resource management server 20 uses the rate table 40 stored in the rate table storage unit 32 and the distribution flow table 42 registered in the distribution flow table storage unit 34. Then, bandwidth resource allocation processing is performed for the flow being delivered and the new flow (step S35).

  That is, the bandwidth resource allocation unit 36 determines the data rate required for the flow being delivered (flow identifier 1) and the new flow (flow identifier 2) registered in the delivery flow table 42 (FIG. 9A), and the delivery destination base station. 14 and the information of the terminals 16a to 16c and the transmission rate of each subcarrier in the rate table 40 (FIG. 3) corresponding to the base station 14 and the terminals 16a to 16c, Select the combination of subcarriers that makes the total transmission rate of subcarriers assigned to each flow equal to or higher than the data rates required for each flow and minimizes the total number of subcarriers assigned to each flow. To do. Then, band resources composed of the selected combination of subcarriers and predetermined time slots are allocated to the delivering flow and the new flow, respectively.

  For example, in FIG. 9A, assuming that the data rate required for the flow being delivered (flow identifier 1) delivered to the terminal 16a is 20 Mbps, the rate table 40 related to the base station 14 in which the terminal 16a is network-entry. All combinations of subcarriers whose total transmission rate in FIG. 3 is 20 Mbps or more, for example, combinations of allocation patterns 1 and 4, allocation patterns 1 and 7, combinations of allocation patterns 4 and 7, etc. Can be a candidate.

  Also, assuming that the data rate required for the new flow (flow identifier 2) distributed to the terminal 16b is 10 Mbps, the transmission of the rate table 40 (FIG. 3) related to the base station 14 with which the terminal 16b has entered the network. All combinations of subcarriers with a total rate of 10 Mbps or more, for example, allocation pattern 10, allocation pattern 11, combination of allocation patterns 12 and 14, and combination of allocation patterns 12 and 18 may be candidates for reassignment. it can.

  Then, a combination of subcarriers that minimizes the sum of the number of subcarriers constituting a reassignment candidate for a flow being delivered and the number of subcarriers constituting a candidate for assignment to a new flow is selected. For example, in the above-described example, a subcarrier of a combination of allocation patterns 1 and 4 or a combination of allocation patterns 1 and 7 is reassigned to a flow under delivery, and an allocation pattern 10 is assigned to a new flow. Alternatively, by assigning 11 subcarriers, a total of 3 subcarriers are assigned. By selecting a combination of subcarriers and predetermined time slots in this way, it is possible to allocate the minimum necessary bandwidth resources to the current flow and the new flow. As a result, the communication capacity of the entire system can be increased. In addition, since the bandwidth resource management server 20 performs the bandwidth resource allocation processing, an effect of reducing the load on the base station 14 for the allocation processing can be obtained.

  The bandwidth resource allocation pattern determined as described above is transmitted from the transmission / reception control unit 38 to the base station 14 (step S36), and the base station 14 performs the distribution flow and the new flow according to the received allocation pattern. Then, the subcarrier, time slot, and MCS are set, and the band resource is determined (step S37). In this case, the in-distribution flow is distributed to the terminals 16a to 16c using the reallocated bandwidth resource.

  The base station 14 that has determined the band resource transmits an acknowledge signal ACK to the band resource management server 20 (step S38). The band resource management server 20 that has received the acknowledge signal ACK from the base station 14 instructs the streaming server 18 to distribute a new flow to the terminals 16a to 16c (step S39). Upon receiving the distribution instruction, the streaming server 18 distributes the new flow to the base station 14, and the base station 14 uses the allocated bandwidth resource to send the new flow to the terminals 16 a to 16 a along with the distributed flow being distributed. 16c (step S40).

  On the other hand, the bandwidth resource allocation unit 36 uses a rate table 40 in which the transmission rate is updated every predetermined time with respect to the flow being delivered, at a predetermined timing, for example, at a timing at which the rate table 40 is updated. In the same manner as in S35, band resources are reassigned to the flow being delivered (step S41). The reassigned band resource allocation pattern is transmitted to the base station 14 (step S42), and the base station 14 changes the band resources of the terminals 16a to 16c according to the received allocation pattern (step S43). Next, the base station 14 transmits an acknowledge signal ACK to the band resource management server 20 after changing the band resource (step S44). Note that the processing in steps S41 to S44 is repeated, for example, every time the rate table 40 is updated.

  Next, when the streaming server 18 detects the end of distribution of the flow being distributed, the streaming server 18 generates a distribution end trigger (step S45), and transmits a distribution end notification of the flow being distributed from the transmission control unit 28 to the bandwidth resource management server 20. (Step S46).

  When the transmission / reception control unit 38 of the bandwidth resource management server 20 receives the distribution end notification, the transmission / reception control unit 38 distributes, from the distribution flow table storage unit 34, data corresponding to the distribution-in-distribution flow specified by the flow identifier of the distribution end notification. Delete from the table 42 (step S47). FIG. 9B shows a distribution flow table 42 in which data corresponding to the flow under distribution specified by the flow identifier 1 in FIG. 9A is deleted and data of the flow under distribution specified by the flow identifier 2 remains. Show.

  When the data corresponding to the distributed flow for which distribution has been completed is deleted from the distribution flow table 42, the bandwidth resource allocation unit 36 of the bandwidth resource management server 20 transmits the rate table 40 stored in the rate table storage unit 32. Using the rate and the data rate of the remaining distribution flow table 42 stored in the distribution flow table storage unit 34, band resource reallocation processing is performed for the flow under distribution (step S48). The reassigned band resource allocation pattern is transmitted to the base station 14 (step S49), and the base station 14 changes the band resources of the terminals 16a to 16c according to the received allocation pattern (step S50). Next, after changing the band resource, the base station 14 transmits an acknowledge signal ACK to the band resource management server 20 (step S51).

  In the present embodiment, by allocating the band resources as described above, it is possible to efficiently use the band resources, particularly when compared with the allocation method disclosed in Patent Document 2.

  That is, in the allocation method disclosed in Patent Document 2, for example, the number of subcarriers is determined with respect to the transmission rate requested by the terminal, not the data rate requested by the flow. In this case, assuming that the data rate required for distributing the flow is 20 Mbps and the transmission rate requested by the terminal is 30 Mbps, for example, the allocation pattern 1 of the subcarrier f1 having a transmission rate of 11.5 Mbps, Allocation pattern 4 of subcarrier f2 having a transmission rate of 11.0 Mbps and allocation pattern 7 of subcarrier f3 having a transmission rate of 11.5 Mbps are allocated to the terminal. Therefore, in Patent Document 2, band resources of three subcarriers f1 to f3 are allocated to the terminal.

  On the other hand, in the case of the present embodiment, since only the bandwidth resources of the two subcarriers f1 and f2 are allocated to the terminals 16a to 16c to which a flow having a data rate of 20 Mbps is distributed, the terminals 16a to 16c are allocated. The bandwidth resources of 16c can be used efficiently.

  Here, when band resources are allocated to the terminals 16a to 16c, there are the following restrictions. (1) A subcarrier already assigned to one flow cannot be assigned to another flow. This is to avoid interference between different flows. (2) The number of subcarriers satisfying the data rate required for each flow is such that the total transmission rate of each allocation pattern is equal to or greater than the data rate required for each flow, and the number of subcarriers allocated for each flow. Is set so that the sum of With this restriction (2), it is possible to efficiently use the bandwidth resource by setting the bandwidth resource allocated to the flow to the necessary minimum.

  The present invention is not limited to the above-described embodiment, and can be modified without departing from the gist of the present invention.

  For example, although the band resource management server 20 has been described as managing and controlling band resources by one base station 14, it can also manage and control band resources of a plurality of base stations. Therefore, for convenience of explanation, the rate table 40 in FIG. 3 shows the relationship among the three terminals 16a to 16c, the one base station 14, the three subcarriers f1 to f3, and the three types of MCS. However, the number of terminals 16a to 16c and the base station 14, the number of subcarriers, and the type of MCS are not limited to these.

  Further, although the bandwidth resource management server 20 has been described as managing bandwidth control according to the data rate requested by the flow distributed from one streaming server 18, a plurality of devices connected to the IP network 12 are used. It is also possible to manage and control bandwidth resources in accordance with data rates required by a plurality of flows distributed from the streaming server.

  Also, in the process of deleting data relating to the flow for which distribution has been completed from the distribution flow table 42, the streaming server 18 transmits a distribution end notification to the band resource management server 20, and the band resource management server 20 receives the distribution end notification. However, it is also conceivable that the flow distribution from the base station 14 to the terminals 16a to 16c is continuing when deleting the data related to the flow. However, the band resource allocation unit 36 reallocates the band resources using the distribution flow table 42 (step S48), transmits a new band resource allocation pattern to the base station 14 (step S49), and the base station 14 Since it takes a certain amount of time to change the band resources of 16a to 16c (step S50), if distribution of the flow from the base station 14 to the terminals 16a to 16c is completed during that time, what is the problem? Don't be. It is also possible to set so that the distribution flow table 42 is updated after the flow distribution is reliably completed in consideration of the communication processing time between the base station 14 and the terminals 16a to 16c.

  Furthermore, the wireless communication system of the present invention can be realized by using Open Flow, which is an existing network control technology. That is, the allocation of bandwidth resources according to the CINR, which is propagation environment information between the terminals 16a to 16c, which are flow distribution destinations, and the base station 14, and the data rate required by the flow, is a controller that controls the open flow. Therefore, it is possible to realize the radio communication system according to the embodiment of the present invention by notifying the OpenFlow switch mounted on the base station 14 in the form of change of the flow table.

DESCRIPTION OF SYMBOLS 10 ... Wireless communication system 12 ... IP network 14 ... Base station (BS)
16a-16c ... Terminal (MS)
18 ... Streaming server 20 ... Band resource management server 24 ... Content storage unit 26 ... Distribution destination information storage unit 28 ... Transmission control unit 30 ... Transmission rate calculation unit 32 ... Rate table storage unit 34 ... Distribution flow table storage unit 36 ... Band resource Allocation unit 38 ... transmission / reception control unit 40 ... rate table 42 ... distribution flow table

Claims (4)

And a base station that connects terminal and non-linear,
A streaming server for storing content included in a flow delivered to the terminal;
A bandwidth resource management server that obtains from the streaming server and allocates bandwidth resources to the flow based on a data rate required for the flow;
With
The bandwidth resource management server
A transmission rate calculation unit that acquires propagation environment information for each subcarrier from the terminal and calculates a transmission rate for each subcarrier based on the propagation environment information;
A rate table storage unit that stores the transmission rate calculated for each subcarrier as a rate table;
Based on the rate table, a predetermined subcarrier is allocated to each of a flow being delivered distributed from the streaming server to the terminal and a new flow newly delivered from the streaming server to the terminal. The sum of the transmission rates of the subcarriers allocated to each flow is equal to or greater than the data rates required for the flows, and the total number of subcarriers allocated to the flows is the minimum. A band resource allocation unit that selects a combination and allocates the subcarriers of the selected combination to the flows;
A distribution flow table storage unit that stores the data rate of the flow under distribution acquired from the streaming server as a distribution flow table;
Have
When the streaming server detects the distribution end of the flow under distribution, the streaming server transmits a distribution end notification to the bandwidth resource management server,
When the bandwidth resource management server receives the distribution end notification, the bandwidth resource management server deletes data corresponding to the in-distribution flow related to the distribution end notification from the distribution flow table,
The band resource allocating unit assigns the subcarrier to the flow under distribution based on the data rate of the remaining distribution flow table stored in the distribution flow table storage unit and the transmission rate of the rate table. Reassign,
The base station transmits the in-distribution flow and the new flow on each of the subcarriers assigned by the band resource management server. The wireless communication system according to claim 1 , wherein
When the streaming server detects a change in the data rate of the flow under delivery, the streaming server sends a rate change notification to the bandwidth resource management server,
When the bandwidth resource management server receives the rate change notification, the bandwidth resource management server changes the data rate of the distribution flow table corresponding to the in-distribution flow related to the rate change notification,
The bandwidth resource allocating unit reallocates the subcarrier to the in-distribution flow based on the changed data rate of the distribution flow table and the transmission rate of the rate table. system. The wireless communication system according to claim 1 or 2 ,
The bandwidth resource allocation unit, when the transmission rate of the rate table is updated based on the propagation environment information acquired from the terminal, the data rate of the distribution flow table and the updated rate table of the rate table A wireless communication system, wherein the subcarrier is reassigned to the delivering flow based on a transmission rate. In the radio | wireless communications system of any one of Claims 1-3 ,
The wireless communication system, wherein the bandwidth resource allocation unit allocates the bandwidth resources based on the subcarriers and time slots to the delivering flow and the new flow.