JP2013078025A - Data distribution method and system for switching base station performing multicast transmission, depending on radio terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data distribution method and system for enabling a radio terminal to switch to a peripheral base station distributing large-volume band candidate data.SOLUTION: A distribution server distributes all of a plurality of band candidate data depending on each base station to the base station. Then, the plurality of base stations distribute any one of the band candidate data selected depending on a communication use band with a radio terminal to the radio terminal, and notify the distribution server of identifiers of the band candidate data. Then, the radio terminal transmits a base station ID of a base station with which the radio terminal is communicating currently and a base station ID of a peripheral base station with which the radio terminal can communicate, to the distribution server. Then, the distribution server transmits a base station ID of a base station which distributes band candidate data having the largest volume multicast data among the peripheral base stations, to the radio terminal. Then, the radio terminal switches from the base station with which the radio terminal is communicating currently to the base station based on the base station ID received from the distribution server.

Description

  The present invention relates to a technique for transmitting multicast data distributed from a distribution server from a base station to a wireless terminal.

  In recent years, a communication environment in which multicast and unicast are mixed has been provided in a wireless network between a base station and a wireless terminal. “Multicast” means that the same data is transmitted by designating a plurality of destination devices. On the other hand, “unicast” means that data is transmitted only to a specific destination device by designating a single address. “Broadcast” refers to transmitting data to an unspecified number of devices. By realizing multicast distribution in a wireless network, it is possible to provide a broadcast service to a number of specific destination terminals with only a minimum bandwidth guarantee.

  Conventionally, there is a technique for selecting a multicast or unicast route (see, for example, Patent Document 1). According to this technique, a multicast route and a unicast route are selected so that a link cost is reduced for a communication network in which a multicast transmission device and a unicast transmission device are mixed.

  There is also a technique for aggregating a plurality of unicast traffic into one multicast traffic at an optimal timing in accordance with a dynamic change relating to the entire network (see, for example, Patent Document 2).

  Furthermore, there is a technique for distributing a specific channel separately using a broadcast infrastructure for broadcast (multicast distribution) and a unicast infrastructure for communication (unicast communication) without being aware of the user (for example, Patent Document 3). reference).

JP 2007-006228 A JP 2004080566 A WO2008 / 120374

  None of the above-described conventional techniques has been studied at all about how to optimize the unicast bandwidth and the multicast bandwidth, and has been a design matter in the system. However, when the unicast communication usage band between the base station and the wireless terminal increases according to the usage conditions of many users, it is necessary to limit the multicast distribution usage band.

  In each of the above prior arts, the distribution server selectively controls multicast / unicast communication. However, when multicast distribution and unicast communication coexist in the wireless network between the base station and the wireless terminal, the distribution server controls the switching, and thus the management cost of the entire system is required. In particular, it is difficult for the distribution server to adaptively manage and control the multicast distribution usage band and the number of channels in real time.

  Further, the wireless terminal receives the multicast data as it is from the base station that has received the unicast data. That is, even if there are other peripheral base stations that can communicate and the peripheral base station distributes large-capacity band candidate data, the wireless terminal cannot know the presence of the peripheral base stations. As a result, the wireless terminal receives multicast data from the base station even if the base station that has received the unicast data distributes small-capacity band candidate data.

  Therefore, according to the present invention, when the base station transmits multicast / unicast data distributed by the distribution server to the wireless terminal, the wireless terminal switches to a neighboring base station that distributes large-capacity band candidate data. An object of the present invention is to provide a data distribution method and system.

According to the present invention, in a data distribution method in a system having a distribution server for distributing data, a wireless terminal, and a plurality of base stations for distributing data received from the distribution server to the wireless terminal,
The base station can distribute both multicast data and unicast data to the wireless terminal,
A first step in which a distribution server generates a plurality of band candidate data obtained by encoding data to be distributed to a wireless terminal using different encoders;
A second step in which the distribution server distributes all of the plurality of band candidate data corresponding to each base station to the base station;
While the plurality of base stations distribute any one band candidate data selected according to the communication use band with the wireless terminal from the plurality of band candidate data received from the distribution server to the wireless terminal. A third step of notifying the distribution server of the identifier of the band candidate data;
A fourth step in which the wireless terminal transmits the base station identifier of the currently communicating base station and the base station identifier of a neighboring base station capable of communication to the distribution server via the base station;
A fifth step in which a distribution server transmits a base station identifier in a base station that distributes candidate bandwidth data having the largest capacity of multicast data among neighboring base stations that can communicate with the wireless terminal to the wireless terminal;
The wireless terminal has a sixth step of switching from the currently communicating base station to the base station based on the base station identifier received from the distribution server.

According to another embodiment of the data distribution method of the present invention,
The wireless terminal measures the received signal strength (RSSI (Received Signal Strength Indicator)) of the radio wave received from the base station,
Regarding the fifth step, it is also preferable that a base station whose received signal strength is equal to or greater than a predetermined threshold is a neighboring base station.

  According to another embodiment of the data distribution method of the present invention, it is also preferable that the distribution server transmits a predetermined threshold based on the received signal strength to the wireless terminal in advance.

According to another embodiment of the data distribution method of the present invention,
For the first stage of the first step, the wireless terminal transmits a multicast entry message to the distribution server via the base station,
Regarding the second step, it is also preferable that the distribution server distributes a plurality of band candidate data only to the base station that has received the multicast entry message.

According to another embodiment of the data distribution method of the present invention,
For the third step, the base station
Detect unicast communication bandwidth of unicast data to the wireless terminal,
It is also preferable to perform control so that the band candidate data is not transmitted when the ratio of the unicast communication usage band to the entire communication band for the downlink to the wireless terminal is equal to or greater than a predetermined threshold.

According to another embodiment of the data distribution method of the present invention,
The base station transmits the value of the average bandwidth T of unit time in the downlink unicast communication usage bandwidth for a plurality of wireless terminals to the distribution server,
Distribution server
It is also preferable to select a combination of a plurality of band candidate data based on the multicast distributable band A obtained by subtracting the average band T of the unicast communication band from the entire downlink communication band P from the base station to the wireless terminal. .

According to the present invention, in a data distribution system having a distribution server that distributes data, a wireless terminal, and a plurality of base stations that distribute data received from the distribution server to the wireless terminal,
Distribution server
Band candidate generation means for generating a plurality of band candidate data obtained by encoding data to be distributed to the wireless terminal by different encoders;
Distributes all candidate bandwidth data corresponding to each base station to the candidate bandwidth distribution means for distributing to the base station and the candidate bandwidth data with the largest multicast data capacity among the peripheral base stations that can communicate with the wireless terminal. A base station identifier for transmitting the base station identifier in the base station to the wireless terminal,
The base station
Band candidate selection means for selecting any one band candidate data from a plurality of band candidate data received from the distribution server according to the communication state with the wireless terminal;
Multicast distribution means for distributing one selected band candidate data to the wireless terminal as multicast data and notifying the distribution server of an identifier of the band candidate data;
Unicast communication means for distributing unicast data to a wireless terminal,
Wireless terminal
A neighboring base station notifying means for transmitting a base station identifier of a base station currently communicating and a base station identifier of a neighboring base station capable of communication to the distribution server via the base station;
Base station switching means for switching from the base station currently communicating to the base station based on the base station identifier received from the distribution server.

According to another embodiment of the data distribution system of the present invention,
The wireless terminal can measure the received signal strength (RSSI) of the radio wave received from the base station through the wireless interface,
The neighboring base station notification means preferably sets a base station whose received signal strength is a predetermined threshold or more as a neighboring base station.

  According to another embodiment of the data distribution system of the present invention, it is also preferable that the distribution server transmits a predetermined threshold based on the received signal strength to the wireless terminal in advance.

According to another embodiment of the data distribution system of the present invention,
The base station
A multicast entry receiving means for receiving a multicast entry message from the wireless terminal;
A multicast entry transmitting means for transmitting a multicast entry message to the distribution server;
The bandwidth candidate distribution means in the distribution server preferably distributes the bandwidth candidate data only to the base station that has received the multicast entry message.

According to another embodiment of the data distribution system of the present invention,
The base station
Unicast band detecting means for detecting a unicast communication use band of downlink unicast data from the unicast communication means to the wireless terminal;
A distribution control unit that controls the multicast distribution unit so that the band candidate data is not transmitted when the ratio of the unicast communication usage band to the total communication band of the downlink to the wireless terminal is equal to or greater than a predetermined threshold. It is also preferable.

According to another embodiment of the data distribution system of the present invention,
The base station further includes a unicast bandwidth notification means for transmitting the value of the average bandwidth T of unit time in the downlink unicast communication utilization bandwidth for a plurality of wireless terminals to the distribution server,
The distribution server, based on the multicast distribution available band A obtained by subtracting the average band T of the unicast communication usage band from the total downlink communication band P from the base station to the wireless terminal. It is also preferable to further include band candidate selection means for selecting a combination of the band candidate data.

  According to the distribution method and system of the present invention, when a base station transmits multicast / unicast data distributed by a distribution server to a wireless terminal, the wireless terminal distributes a large amount of bandwidth candidate data. It is possible to switch to neighboring base stations.

It is a system configuration diagram in the present invention. It is explanatory drawing showing the band candidate data transmitted to a base station from a delivery server. It is explanatory drawing showing the band candidate data transmitted to a radio | wireless terminal from a base station. It is a functional block diagram of the delivery server in this invention, a base station, and a radio | wireless terminal. It is a sequence diagram in the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a system configuration diagram according to the present invention.

  According to FIG. 1, a distribution server 1 and a plurality of base stations 2 are connected via a communication carrier network. The distribution server 1 is usually a communication facility operated by a communication carrier. The distribution server 1 distributes data to the wireless terminal 3 via the base station 2 connected to the communication carrier network. This data includes, for example, both broadcast type content and communication type content. Therefore, multicast distribution and unicast communication are mixed in the wireless network between the base station 2 and the wireless terminal 3. When viewed from the base station 2, unicast communication between another server and the wireless terminal 3 is relayed.

  Also, according to FIG. 1, the wireless network between the base station 2 and the wireless terminal 3 may be based on various different wireless environments. For example, there are a mobile phone network, a WiMAX (Worldwide Interoperability for Microwave Access) network, a wireless LAN (Local Area Network), and the like.

  In addition, it is preferable that the communication apparatus is arranged in a tree structure in the network corresponding to the multicast. According to FIG. 1, the distribution server, the base station, and the wireless terminal are configured in the hierarchical order of parent-child-grandchild. The That is, the content (or stream) is transmitted from the higher layer distribution server to the lower layer wireless terminal (hierarchical multicast).

  FIG. 2 is an explanatory diagram showing band candidate data transmitted from the distribution server to the base station.

According to FIG. 2, the distribution server 1 prepares a plurality of band candidate data in which data to be distributed to the wireless terminal 3 is encoded by different encoders (see FIG. 2A). The plurality of band candidate data is generated for each base station and / or for each radio environment type. For example, nine types of band candidate data are simply generated as follows.
Communication bandwidth when the wireless environment is a mobile phone network Large / Medium / Small Communication bandwidth when the wireless environment is a WiMAX network Large / Medium / Small Communication bandwidth when the wireless environment is a wireless LAN Large / Medium ·small

  The distribution server 1 transmits all such a plurality of band candidate data to the base station 2 in which multicast entry has been made (see FIG. 2B). Which band candidate data is used is based on the control of the base station 2.

  It is assumed that the wireless terminal 3 can communicate with both the base stations 2A and 2B. In the wireless terminal 3, for example, it is assumed that the received signal strength of a radio wave transmitted from the base station 2A and the received signal strength of a radio wave transmitted from the base station 2B are equal to or greater than a predetermined threshold.

  Further, according to FIG. 2, the bandwidth of the multicast data in the bandwidth candidate data distributed from the base station 2A (see FIG. 2C) is the bandwidth of the multicast data in the bandwidth candidate data distributed from the base station 2B. (Refer to FIG. 2D). Even when the wireless terminal 3 initially receives unicast data from the base station 2A, according to the present invention, the wireless terminal 3 operates to receive multicast data from the base station 2B. As the wireless terminal 3, switching to the base station 2B rather than the base station 2A can receive a large amount of multicast data.

  FIG. 3 is an explanatory diagram showing band candidate data transmitted from the base station to the wireless terminal.

  According to FIG. 3A, a plurality of band candidate data in multicast distribution transmitted from the distribution server 1 is represented.

  According to FIG. 3B, the downlink unicast communication usage band from the base station 2 to the wireless terminal 3 is represented. The unicast communication use band is a use band of existing general communication, and is not limited to unicast communication with the distribution server 1, but includes all unicast communication with other servers and terminals. . The downlink unicast communication usage band changes with the passage of time in response to requests from a large number of user terminals. Here, it can be understood that a vacant band portion obtained by subtracting the unicast communication use band from the total transmission capacity that can be distributed from the base station 2 is a band that can be used for multicast distribution.

  According to FIG.3 (c), either of the zone | band candidate data received from the delivery server 1 can be matched and delivered to the empty zone | band part in FIG.3 (b). According to FIG. 3 (c), it is depicted that one band candidate data is accommodated in the vacant band portion, but of course, it is controlled to accommodate a plurality of band candidate data. May be.

According to FIG.3 (c), the following band candidate data are accommodated for every time range.
Time range 1: Band candidate data 1
Time range 2: Band candidate data 2
(Here, it is assumed that there is no wireless terminal receiving channel 3)
Time range 3: Band candidate data 1 (only channels 1 and 2)
Time range 4: Band candidate data 3 (only channels 1 and 2)
In this way, the base station 2 detects the unicast communication use band for each time range, and selects multicast band candidate data according to the free band portion obtained by subtracting the unicast communication use band from the total transmission capacity. Further, the base station 2 does not distribute a channel that is no longer required to be distributed to the wireless terminal 3 in response to the multicast entry message.

  FIG. 4 is a functional configuration diagram of the distribution server, the base station, and the wireless terminal in the present invention.

[Distribution server 1]
According to FIG. 4, the distribution server 1 includes a content storage unit 101, a carrier network interface 102, a band candidate generation unit 111, a band candidate selection unit 112, a band candidate distribution unit 113, and a unicast communication unit 114. And a base station instruction unit 115. These functional components can be realized by executing a program that causes a computer mounted on the server to function.

  The content storage unit 101 stores content to be distributed to the wireless terminal 3.

  The carrier network interface 102 is connected to the telecommunications carrier network and distributes content to a plurality of base stations 2. The carrier network interface 102 includes a physical layer unit connected to the carrier network, an IP (Internet Protocol) processing unit, and a transport protocol processing unit.

  The band candidate generation unit 111 acquires content to be distributed to the wireless terminal 3 from the content storage unit 101. A plurality of band candidate data in which these are encoded by different encoders are generated from the content to be transmitted as the multicast distribution. That is, encoding is performed at a plurality of different bit rates. Here, the plurality of band candidate data is generated for each base station and / or for each radio environment type. That is, a plurality of band candidate data is generated for each cell between the base station and the wireless terminal. At this time, it is also preferable that the number of multicast channels is optimized. The generated plurality of band candidate data is output to the band candidate selection unit 112.

  The band candidate selection unit 112 inputs a plurality of band candidate data from the band candidate generation unit 111 and also inputs the unicast communication usage band received from the base station 2 via the carrier network interface 102. The band candidate selection unit 112 calculates a multicast distributable band A by subtracting the average band T of the unicast communication band from the entire downlink communication band P from the base station to the wireless terminal. Then, the band candidate selection unit 112 selects a combination of a plurality of band candidate data based on the multicast distributable band A with respect to the band candidate distribution unit 113.

  Then, the band candidate distribution unit 113 distributes all of the plurality of band candidate data corresponding to the base station and / or the radio environment type to the base station.

  Moreover, it is preferable that the band candidate selection unit 112 distributes the band candidate data only to the base station that has received the multicast entry message from the base station 2. Although the present invention is configured on the assumption that the communication band of the carrier network has a margin, it is preferable to reduce the transmission of useless band candidate data.

  The unicast communication unit 114 acquires content from the content storage unit 101 and transmits the content to one wireless terminal 3 via the base station 2. Perform general unicast communication between server and client.

  The base station instruction unit 115 receives the identifier of the selected band candidate data from each base station 2. As a result, the base station instruction unit 115 can know how much multicast data is being transmitted for each base station 2. Moreover, the base station instruction | indication part 115 receives the received signal strength RSSI for every peripheral base station which can communicate from the radio | wireless terminal 3 which has received multicast data. Thus, the base station instruction unit 115 can know which base station the wireless terminal 3 can communicate with.

  In addition, the base station instruction unit 115 transmits, to the wireless terminal 3, the base station identifier in the base station that distributes the band candidate data having the largest multicast data capacity among the neighboring base stations that can communicate with the wireless terminal 3. Send. Thereby, the wireless terminal 3 can receive the multicast data from the base station that distributes the bandwidth candidate data having the largest possible capacity of the multicast data.

[Base station 2]
The base station 2 includes a radio interface 201, a carrier network interface 202, a band candidate selection unit 211, a multicast distribution unit 212, a unicast communication unit 213, a unicast band detection unit 214, and a unicast band notification unit. 215, a distribution control unit 216, a multicast entry reception unit 217, and a multicast entry transmission unit 218. These functional components are also realized by executing a program that causes a computer installed in the base station to function.

  The wireless interface 201 transmits data to the wireless terminal 3 via wireless. The carrier network interface 202 receives data from the distribution server 1 via the communication carrier network. Both interfaces have a physical layer unit, an IP processing unit, and a transport protocol processing unit.

  The band candidate selection unit 211 selects any one of the band candidate data from the plurality of band candidate data received from the distribution server 1 according to the communication state with the wireless terminal. The communication state here refers to the state of the unicast communication band. The band candidate selection unit 211 outputs the selected band candidate data to the multicast distribution unit 212.

  The multicast distribution unit 212 distributes the selected band candidate data to the wireless terminal 3 as multicast data. The multicast data is transmitted from the wireless interface 201 to the wireless terminal 3 via wireless. The multicast distribution unit 212 distributes only the channels required by the multicast entry message in the band candidate data.

  The unicast communication unit 213 distributes the unicast data received from the distribution server 1 to the wireless terminal 3. Unicast data is transmitted from the wireless interface 201 to the wireless terminal 3 via wireless communication. The unicast data is not limited to the unicast data from the distribution server 1, but includes all data between other servers and terminals.

  The unicast band detection unit 214 detects a unicast communication use band of unicast data that is downlinked to the wireless terminal from the unicast communication unit 213. The detected unicast communication usage band is output to the band candidate selection unit 211, the unicast band notification unit 215, and the distribution control unit 216.

  The unicast bandwidth notification unit 215 transmits the value of the average bandwidth T of the unit time of the downlink unicast communication usage bandwidth for a plurality of wireless terminals to the distribution server 1.

  The distribution control unit 216 controls the multicast distribution unit 212 not to transmit the band candidate data when the ratio of the unicast communication usage band to the total communication band for the downlink to the wireless terminal is equal to or greater than a predetermined threshold. To do.

  The multicast entry reception unit 217 receives a multicast entry message from the wireless terminal 3. The fact that multicast distribution is possible is output to the multicast distribution unit 212.

  The multicast entry transmission unit 218 transmits a multicast entry message to the distribution server 1.

[Wireless terminal 3]
The wireless terminal 3 includes a wireless interface 300, a unicast communication unit 301 that communicates unicast data, a multicast reception unit 302 that receives multicast data, a neighboring base station notification unit 311, and a base station switching unit 312. . These functional components are realized by executing a program that causes a computer installed in the wireless terminal to function.

  The neighboring base station notification unit 311 measures the received signal strength RSSI of the radio wave received from each base station 2 via the wireless interface 300. Here, a base station whose received signal strength is equal to or greater than a predetermined threshold is recognized as a communicable peripheral base station. Then, the neighboring base station notification unit 311 transmits the base station identifier of the currently communicating base station and the neighboring base station identifier of the communicable neighboring base station to the distribution server 1 via the base station 2. It is also preferable that the neighboring base station notification unit 311 periodically transmits a base station identifier of a neighboring base station with which communication is possible.

  The predetermined threshold may be received as multicast control data from the base station 2. Alternatively, a plurality of RSSIs that can be reproduced by the wireless terminal in the past (for example, about several days) are stored, and a value having a margin by a predetermined value dB from the lowest value of the RSSI may be set as the predetermined threshold value.

  The base station switching unit 312 receives a base station identifier that is a handover destination from the distribution server 1. Then, the base station switching unit 312 switches from the currently communicating base station to the base station 2 based on the base station identifier.

  FIG. 5 is a sequence diagram in the present invention.

(S501) The distribution server 1 and other servers or terminals are communicating unicast data with the base station 2 (similar to the unicast communication unit 114 in FIG. 4).
(S502) The base station 2 distributes unicast data to a plurality of wireless terminals 3 (similar to the unicast communication unit 213 in FIG. 4). At this time, the base station 2 detects the average band T of the downlink unicast communication usage band (similar to the unicast band detection unit 214 in FIG. 4).
(S503) The base station 2 transmits the average band T of the unicast communication usage band to the distribution server 1 (similar to the unicast band notification unit 215 in FIG. 4).
(S504) The wireless terminal 3 transmits a multicast entry message to the base station 2 based on a user operation (similar to the multicast entry receiving unit 217 in FIG. 4). On the other hand, the base station 2 transmits a multicast entry message to the distribution server 1 (similar to the multicast entry transmission unit 218 in FIG. 4).
(S505) The distribution server 1 generates a plurality of band candidate data in which data to be distributed to the wireless terminal 3 is encoded by different encoders for each base station and / or for each radio environment type (band candidates in FIG. 4). The same as the generation unit 111).
(S506) The distribution server 1 uses a plurality of band candidate data based on the multicast distributable band A obtained by subtracting the average band T of the unicast communication band from the entire downlink communication band P from the base station to the wireless terminal. (Similar to the band candidate selection unit 112 in FIG. 4).
(S507) The distribution server 1 distributes all the selected plurality of band candidate data to the base station 2 (similar to the band candidate distribution unit 113 in FIG. 4).
(S508) The base station 2 selects one of the plurality of band candidate data received from the distribution server 1 according to the communication use band with the wireless terminal 3 (FIG. 4). Similar to the band candidate selection unit 211).
(S509) The base station 2 transmits the selected band candidate data to the wireless terminal 3 (similar to the multicast distribution unit 212 in FIG. 4). Further, the base station 2 transmits the identifier of the selected band candidate data to the distribution server 1. As a result, the distribution server 1 can know how much multicast data is being transmitted to each base station 2.

(S510) At this time, the wireless terminal 3 searches for neighboring base stations (2B) other than the base station 2A. Specifically, the received signal strength RSSI of the radio wave received from each base station is measured. Here, a base station whose received signal strength is equal to or greater than a predetermined threshold is recognized as a communicable peripheral base station. The predetermined threshold may be received as multicast control data from the base station 2.

(S511) The wireless terminal 2 transmits the base station identifier of the currently communicating base station and the base station identifier of the communicable peripheral base station to the distribution server 1 via the base station 2.

(S512) The distribution server 1 transmits the base station identifier in the base station 2B that distributes the bandwidth candidate data having the largest multicast data capacity among the neighboring base stations that can communicate with the wireless terminal 3 via the base station 2A. Transmit to the wireless terminal 3.

(S512) The radio terminal 3 switches from the currently communicating base station 2A to the base station 2B based on the base station identifier.

  As described above in detail, according to the distribution method and system of the present invention, when the base station transmits the multicast / unicast data distributed by the distribution server to the wireless terminal, the wireless terminal has a large capacity. It is possible to switch to a neighboring base station that distributes the band candidate data. The distribution server can control the base station according to the communication state of the wireless network with the wireless terminal without controlling the multicast / unicast communication. As a result, multicast distribution using different communication bandwidths efficiently for each base station becomes possible.

  Various changes, modifications, and omissions of the above-described various embodiments of the present invention can be easily made by those skilled in the art. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

DESCRIPTION OF SYMBOLS 1 Distribution server 101 Content storage part 102 Provider network interface 111 Band candidate production | generation part 112 Band candidate selection part 113 Band candidate delivery part 114 Unicast communication part 115 Base station instruction | indication part 2 Base station 201 Wireless interface 202 Provider network interface 211 Band Candidate selection unit 212 Multicast distribution unit 213 Unicast communication unit 214 Unicast band detection unit 215 Unicast band notification unit 216 Distribution control unit 217 Multicast entry reception unit 218 Multicast entry transmission unit 3 Wireless terminal 300 Wireless interface 301 Unicast communication unit 302 Multicast receiver 311 Neighboring base station notification unit 312 Base station switching unit

Claims (12)

In a data distribution method in a system having a distribution server for distributing data, a wireless terminal, and a plurality of base stations for distributing the data received from the distribution server to the wireless terminal,
The base station can deliver a mixture of multicast data and unicast data to the wireless terminal,
A first step in which the distribution server generates a plurality of band candidate data in which data to be distributed to the wireless terminal is encoded by different encoders;
A second step in which the distribution server distributes all of the plurality of band candidate data corresponding to each base station to the base station;
A plurality of base stations distribute, to the wireless terminal, any one of the plurality of band candidate data received from the distribution server according to the communication usage band with the wireless terminal. And a third step of notifying the distribution server of the identifier of the bandwidth candidate data;
A fourth step in which the wireless terminal transmits a base station identifier of a currently communicating base station and a base station identifier of a communicable peripheral base station to the distribution server via the base station;
Fifth step of transmitting, to the wireless terminal, the distribution server transmits a base station identifier in a base station that distributes candidate band data having the largest multicast data capacity among neighboring base stations capable of communicating with the wireless terminal. When,
A data distribution method comprising: a sixth step in which the wireless terminal switches from the currently communicating base station to the base station based on the base station identifier received from the distribution server. The wireless terminal measures the received signal strength (RSSI (Received Signal Strength Indicator)) of the radio wave received from the base station,
The data distribution method according to claim 1, wherein in the fifth step, a base station whose received signal strength is equal to or greater than a predetermined threshold is set as the neighboring base station.   The data distribution method according to claim 1, wherein the distribution server transmits the predetermined threshold based on the received signal strength to the wireless terminal in advance. For the first stage of the first step, the wireless terminal transmits a multicast entry message to the distribution server via the base station,
4. The second step, wherein the distribution server distributes the plurality of band candidate data only to the base station that has received the multicast entry message. 5. The data distribution method described in 1. For the third step, the base station
Detecting a unicast communication usage band of unicast data downstream to the wireless terminal,
5. The control is performed so that the band candidate data is not transmitted when a ratio of the unicast communication use band to a total communication band of the downlink to the wireless terminal is equal to or greater than a predetermined threshold. The data distribution method according to any one of the above. The base station transmits a value of an average bandwidth T of unit time in a downlink unicast communication usage band for a plurality of wireless terminals to the distribution server,
The distribution server
Selecting a combination of a plurality of band candidate data based on a multicast distributable band A obtained by subtracting an average band T of the unicast communication use band from the entire downlink communication band P from the base station to the wireless terminal. The data distribution method according to claim 1, wherein the data distribution method is a data distribution method. In a data distribution system having a distribution server for distributing data, a wireless terminal, and a plurality of base stations for distributing the data received from the distribution server to the wireless terminal,
The distribution server
Band candidate generation means for generating a plurality of band candidate data obtained by encoding data to be distributed to the wireless terminal using different encoders;
Band candidate distribution means for distributing all of the plurality of band candidate data corresponding to each base station to the base station and a band candidate having the largest multicast data capacity among the peripheral base stations that can communicate with the wireless terminal A base station identifier for transmitting data to a base station identifier in a base station that distributes data;
The base station
Band candidate selection means for selecting any one band candidate data according to a communication state with the wireless terminal from among a plurality of band candidate data received from the distribution server;
Multicast distribution means for distributing one selected band candidate data as multicast data to the wireless terminal, and notifying the distribution server of an identifier of the band candidate data;
Unicast communication means for distributing unicast data to the wireless terminal,
The wireless terminal is
A neighboring base station notifying means for transmitting a base station identifier of a currently communicating base station and a neighboring base station identifier of a communicable neighboring base station to the distribution server via the base station;
A data distribution system comprising: base station switching means for switching from the currently communicating base station to the base station based on the base station identifier received from the distribution server. The wireless terminal can measure a received signal strength (RSSI) of a radio wave received from a base station through a wireless interface,
8. The data distribution system according to claim 7, wherein the neighboring base station notifying means sets the neighboring base station to be a base station whose received signal strength is equal to or greater than a predetermined threshold.   The data distribution system according to claim 7 or 8, wherein the distribution server transmits the predetermined threshold based on the received signal strength to the wireless terminal in advance. The base station
Multicast entry receiving means for receiving a multicast entry message from the wireless terminal;
Multicast entry transmitting means for transmitting a multicast entry message to the distribution server,
The bandwidth candidate delivery means in the delivery server delivers the bandwidth candidate data only to the base station that has received the multicast entry message. Data distribution system. The base station
Unicast bandwidth detection means for detecting a unicast communication usage bandwidth of downlink unicast data from the unicast communication means to the wireless terminal;
Distribution control for controlling the multicast distribution means so that the band candidate data is not transmitted when the ratio of the unicast communication usage band to the total communication band of the downlink to the wireless terminal is equal to or greater than a predetermined threshold. The data distribution system according to any one of claims 7 to 10, further comprising: means. The base station further has a unicast bandwidth notification means for transmitting a value of an average bandwidth T of unit time in a downlink unicast communication utilization bandwidth for a plurality of wireless terminals to the distribution server,
The distribution server is based on a multicast distributable band A obtained by subtracting an average band T of the unicast communication use band from the entire downlink communication band P from the base station to the wireless terminal to the band candidate distribution unit. The data distribution system according to claim 7, further comprising band candidate selection means for selecting a combination of a plurality of band candidate data.

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