Method and apparatus for performing coverage control for multicast services in a wireless network

METHOD AND EQUIPMENT FOR COVERAGE CONTROL FOR MULTI-DIFFUSION SERVICES IN A WIRELESS NETWORK

BACKGROUND OF THE INVENTION

I. FIELD OF THE INVENTION

The present invention relates generally to group messages and more particularly to a method and equipment for efficiently controlling multicast group messages in a wireless network.

II. Description of Related Art

Traditional applications for networked computers involve communication between two computers. In these networks, data is transmitted, point by point, from one computer to another computer. That is, data from one computer is sent to the other computer, and to none else.

However, some recent and important applications, such as LAN TV, videoconferencing, broadcasting internal company communication systems, and collaborative computing, require point-to-multipoint data transmission, ie data transmission to multiple recipients simultaneously. These applications require a huge amount of network bandwidth to be effectively deployed using the peer-to-peer technique. For example, using a traditional peer-to-peer transmission scheme would require the same information to be transmitted n times, where n represents the number of recipients. The bandwidth required to accomplish such a task would grow in proportion to the number of computers receiving the transmission. Such an approach is not feasible for applications where it is necessary to send large data transmissions, such as audio and video, to a large number of recipients.

To effectively implement the transfer of large amounts of data over a point-to-multipoint network, a certain design of broadcasting has been proposed. In a given broadcasting design, data is separated into packets, each packet is addressed to a broadcast address, rather than addressing multiple copies of each packet to each desired recipient. However, if this technique is used, the network should generally send the packets of information throughout the network so that anyone wishing to receive the information can hear the broadcast address and receive the information. Sending information packets everywhere requires significant use of network resources in the event that only a small group of recipients want the information.

To solve this problem, a technique known as IP multicasting has been developed for use in wired IP networks. With IP multicasting, applications can send a copy of each data packet and address it to a group of recipients who wish to receive the information generated by an application. This technique addresses data packets to a group of recipients rather than individual recipients, and relies on the network to only resend data packets for paths that have a subnet that needs the information, ie, a subnet having at least one recipient who wants the particular IP multicast. An example of a subnet is a local broadcast network, such as an Ethernet LAN.

Applications for point-to-multipoint communications in wireless networks have not yet been deployed on a large scale due to the large bandwidth needed to accommodate these communication speeds. In transmission however, increases in wireless data and bandwidth indicate that such applications may eventually be used in such wireless networks.

In a wireless network, users of wireless communication devices communicate over an air interface with a central computer. This can be done directly, as in the case of a wireless LAN in a work environment, or it can be done through cellular infrastructure equipment, as in the case of a wireless telephone application. In such wireless networks, it would be desirable to limit multicast transmissions to a specific geographic area having at least one user interested in receiving. Since the broadcast subnet for a wireless network typically corresponds to a particular geographic area, the process of determining which subnets require transmission determines which geographic areas are covered by multicast transmission, and hence the name control of roof.

Internet Host Extension for IP Multicasting RFC document, No. 1112, pages 1-17 (Deering S, August 1, 1989) discloses a method of sending and receiving IP multicast datagrams for multicasting on the Internet. IP Multicasting for Wireless Mobile Hosts (George Xylomenos and George C. Polyzos) discloses multicasting and mobility support techniques for wireless mobile hosts in TCP / IP networks.

Currently, in order to transmit multicast transmission over a wireless network, the transmission must be sent to all terminal devices, regardless of whether or not multicast transmission is desired.

SUMMARY OF THE INVENTION

The present invention is a method and equipment for providing coverage control for a multicast service in a wireless network. The present invention allows multicast transmissions to be efficiently distributed over a wireless network by limiting multicast information transmissions to a subset of devices available on the wireless network.

In one embodiment, the present invention is an apparatus for providing coverage control for a multicast service in a wireless network, the wireless network comprising a central transceiver and multiple wireless communication devices. The present invention comprises the central transceiver, comprising a receiver for receiving a membership report from a wireless communication device, the membership report identifying a multicast group, the membership report being provided to a processor. 0 The processor generates an indication of the multicast group identified in the membership report and provides the indication to a transmitter for transmitting the indication to at least a portion of multiple wireless communication devices.

In another embodiment, the present invention is a method of providing coverage control for a multicast service in a wireless network, the wireless network comprising a central transceiver and multiple wireless communication devices. The present invention comprises the steps of receiving a membership report from a first wireless communication device, the membership report identifying a multicast group. An indication of the received membership report is generated by a processor contained within the central transceiver. The indication is then transmitted to at least a portion of the multiple wireless communication devices, the indication identifying the multicast group identified in the received membership report.

BRIEF DESCRIPTION OF DRAWINGS

The features, objects and advantages of the present invention will be better understood from the detailed description set forth below when made in association with the drawings in which identical reference characters identify corresponding elements throughout the drawings and in which:

FIG. 1 is a block diagram of the present invention as used in a wireless communication system;

FIG. 2 illustrates the concept of IP multicasting as applied to a data network;

FIG. 3 illustrates the present invention as implemented in a wireless network, such as a wireless telephone communication system;

FIG. 4 is a flow chart illustrating a method of a first wireless communication device joining an IP multicast group as used in the wireless communication system of FIG. 3;

FIG. 5 illustrates a flowchart of a central transceiver initiating a membership report search to determine which IP multicast is required within the base station coverage area;

FIG. 6 is a flow chart illustrating the method of the present invention as implemented in the wireless communication device of FIG. 4;

FIG. 7 illustrates the equipment of the present invention as implemented in the wireless communication device of FIG. 4; and

FIG. 8 illustrates the equipment of the present invention as implemented in the central transceiver of FIG. 5

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a method and equipment for providing coverage control for a multicast service in a wireless network. Although the present invention is described in the context of a terrestrial wireless communication system, it should be understood that the present invention may also be used in other wireless communication systems, such as, for example, in a satellite communication system.

In addition, the present invention is not limited to a wireless telephone system, but may also be used in wireless data applications such as a local area network (LAN) or wide area network (WAN).

The present invention allows wireless communication devices in a wireless network to determine which multicast groups other than wireless communication devices in the network are receiving or would like to receive. This is achieved by transmitting from a central transceiver an indication of the desired multicast (s) to other wireless communication devices when the information is received by a central transceiver. This reduces the number of transmissions by other wireless communication devices that also wish to join a multicast group, thereby preventing a processing load on system resources. It also advantageously reduces the bandwidth used for communications.

FIG. 1 is a block diagram of a wireless communication system 100. The wireless communication system 100 may use one of several modulation techniques available, such as code division multiple access (CDMA) or time division multiple access, among others. Communication system 100 comprises a mobile switching center 102 (MSC), one or more base stations 104 and 106, and three wireless communication devices (WCD) 108, 110 and 112. Within the communication system 100 there is typically a high number of WCDs operating, although only three such devices are shown in FIG. 1, for the sake of clarity. WCDs 108, 110 and 112 are cordless phones in one embodiment of the present invention, however, may alternatively comprise a wireless recording device, a wireless camera, a wireless video recorder, a computer, or a combination of these devices.

In communication system 100, WCDs 108, 110 and 112 communicate via an air interface with one or more base stations 104 and / or 106 using one of the well-known modulation techniques mentioned above. Communication system 100 is generally capable of providing both voice and data services to system users. Voice services are standard, point-to-point audio communications, typically between a WCD and another WCD, or a wired communication device, such as a serial telephone. Data services are generally any communications capable of transmitting over a data network, such as the Internet. Data services allow the transmission of data files such as e-mail, database information, maps, executable programs, etc. In addition, audio, video, or any other information may be encapsulated in data packets, also known as datagrams, for air transmission and then over a network.

Transmissions to WCDs may originate either from source application or telephone 116, depending on the nature of the transmission. With respect to data transmissions, the information from the source application 114 is packaged into datagrams and then provided to the data network 118 which, in one embodiment, comprises the Internet. The source application 114 may be any data generating source, such as a computer or computer program, a telephone, a camcorder, or a web site. The source application 114 may generally transmit and receiving data, although in a multicast application, such as a transmission of audio and / or video information, the source application 114 generally only provides multicast data to the data network.

Datagrams from source application 114 are routed through data network 118 via routers 120, 122, and 124. Network 118 typically comprises hundreds, or even thousands of routers, but only three are shown. in FIG. 1 for the sake of clarity. A router is a well-known device for distributing datagrams over data network 118 using information contained within each datagram specifying a destination for the datagram. In the data network 118, each router is generally located at a great distance from other routers and each serves a local area of ​​users.

In one embodiment, the datagrams are routed from router 120 to router 122 and then to router 124 and finally to MSC 102. The datagram is received by an Interrupt Function (IWF, not shown). generally within the MSC 102 or base station 104/106. IWF is a well-known device for sending and receiving data transmissions between a wireless communication system and a terrestrial data network, such as data network 118. In other embodiments, datagrams are routed directly from router 124 to base stations 104 and / or 106, or may be routed through MSC 102 using a custom interface very similar to IWF. In either case, datagrams are routed to base stations 104 and / or 106 using well known techniques.

Datagrams are then transmitted to a desired WCD through at least one base station 104/106, as is well known in the art. For data transmissions from a WCD to the source application 114, the process is reversed.

Voice services between one WCD and another WCD, or for telephone 116, are well known in the art and will therefore not be discussed here.

FIG. 2 illustrates the concept of IP multicasting as applied to data network 118. IP multicasting is a method of efficiently distributing data from a single source, such as the source application 114, to multiple recipients across data network 118. Unlike standard broadcast techniques, data can once be sent from data source 114 to a group of devices that are programmed to receive it. Using this technique, data packets are generated comprising a group destination address identifying a particular multicast group. For example, the source application 114 could comprise a web site with sports scores information and any datagrams transmitted by the application 114 particular reserved destination address, in this example, a source routers would comprise one for such a multicast.

200, 202, and 204 resend sports datagrams from the source application 114 to any router / device that is registered to receive the sports results multicast. Registers typically originate from a terminal device such as a computer. 0 The desire to receive the sports results multicast is transmitted from the terminal device through the various routers comprising the data network 118 and finally to a router in direct communication with the source application, in this case the source application 114.

It is important to note that after a device has a multicast group of terminal devices requesting membership, the other terminals on the same local subnet do not need to be included in the multicast, since the source application data 114 is already will be resent to the local subnet as a result of the previous request.

In IP multicasting, a protocol known as Internet Group Management Protocol (IGMP) is used to add and delete end devices from multicast as well as to communicate this information between routers.

In the case of communications between routers and their respective terminal devices, an IGMP Terminal Device Adherence Scan is periodically sent to all terminal devices using a predetermined destination address, such as an IP address of 224.0.0.1, and having a duration time value (ITL) of 1. Adherence Search is used to determine which multicast is required by at least one terminal device within the local router. Each endpoint device, in response to the Membership Survey, transmits a membership report to the local router, identifying the desired multicast groups. In order to prevent a flood of adhesion reports from the end devices in response to the Adhesion Search, each end device initiates a randomly chosen report delay timer for each of the multicast group memberships. If, during the delay period, a report identifying a first multicast group is transmitted from another terminal device within the local terminal device group, each terminal device resets its associated timer, thereby preventing the other devices. terminals generate a membership report for the first multicast group. When the membership report is sent to the local router, all other local terminal devices on the local network also hear the membership report. This ensures that membership reports are spread over a period of time and that reporting traffic is minimized for each local endpoint device group.

When there is no membership report identifying a given multicast group after a predetermined number of polls, the router assumes that none of the end devices want the information from the given multicast group, and therefore the router no longer resends datagrams referring to it. this multicast to local terminal devices.

It should be understood that any terminal device can join a multicast group by simply generating a request and sending it to the local network to the local router. You don't have to wait for a membership search from the local router to join a multicast group.

The foregoing discussion can now be illustrated with reference to FIG. 2. The source application 114 is assumed to generate a multicast related to a sporting event, comprising both audio and visual information. Users of individual terminal devices, typically home or work computers, may wish to receive multicast transmission from the source application 114. These individual terminal devices are shown in FIG. 2 as the terminal devices 218, 220, 222, 210, 212, 214 and 216. Terminal devices 218, 220, and 222 comprise a local area network, each terminal device being networked with each other and with a local router 206. Likewise, terminal devices 210, 212, 214 and 216 comprise a local area network, each terminal device being networked with each other and with a local router 208. 0 Local router 206 or 208 may also be known as Ethernet or plug-in star-local area network.

Local router 206 is connected to router 204, and local router 208 is connected to router 202. Routers 204 and 202, in turn, are connected to each other as well as router 200. Router 200 is connected to application 114 source. Routers 200, 202, and 204 are generally connected to other routers, Internet access ports, local routers, and source applications.

Specifically with respect to local router 206, at a predetermined time interval, local router 206 will send an IGMP adhesion scan to all local terminal devices, in the present example, to terminal devices 218, 220, and 222. When a terminal device receives a membership poll, it responds with a membership report for each multicast group to which it belongs. For example, terminal device 218 and terminal device 220 may already belong to a sports results related multicast group.

However, terminal devices 218 and 220 do not immediately respond to the adhesion search. Instead, each terminal device initiates an independent and randomly chosen report delay timer for the sports score multicast group. For example, terminal device 218 chooses a timeout value of 1 second and terminal device 220 chooses a timeout of 1.5 seconds. When the first timer lets 1 second pass on the terminal device 218, it responds to the membership search by alerting the local router 206 that it belongs to the sports results multicast group. The 220 and 222 terminal devices also hear this report. 0 device 220, upon hearing that the terminal device 218 has already reported its membership in the sports scores multicast group, resets its timer to zero and does not respond to the membership scan even though it is also a member of the multicast sports score group. sports results. Terminal device 222 also does not respond to the adhesion search because it does not belong to any multicast group. This reduces the number of responses to membership surveys that need to be submitted.

The response from terminal device 218 is generally provided to router 200 through a series of routers in addition to router 204. As each router receives the response that terminal device 218 is a member of the multicast of sports results, routers know how to resend any sports results multicast information to the next router in the chain. For example, router 200, upon receiving sports result group-related multicast traffic from the source application 114, knows that at least router 204 wishes to receive sports results multicast reception. Therefore, information from the source application 114 is forwarded to router 204. No requests or membership status has been received from router 202, therefore, the sports score information is not forwarded to that router. Router 204, having received information from local router 206 saying that at least one terminal device in its local network requests multicast sports results, resends the information to local router 206. 0 Local router 206 then forwards the multicast information to the local network, where all terminal devices receive the information, but only the terminal devices that wish the information will process it.

It should be noted that multicast routers do not need to be directly addressed as their interfaces are configured to receive all IP multicast traffic. Likewise, a router does not need to keep a detailed list of which terminal devices belong to each multicast group; The router only needs to know that at least one member of the group is present on a network interface. Multicast routers periodically transmit polls to update their knowledge of the group members present on each network interface.

If the router does not receive a report for a particular multicast group after several polls, the router assumes that group members are no longer present at the interface and the group is removed from the group membership list for the directly attached local network. .

Referring to FIG. 3, a wireless network such as a wireless communication system according to a preferred embodiment of the present invention is described. As explained above, multicast information is sent from the source application 114, in this example, sports score information. Multicast information is provided to the data network 118 in one embodiment comprising the Internet.

WCDs throughout the wireless communication system send and receive information wirelessly through one or more base stations 104 and / or 106. In a wireless LAN or WAN environment, base station 104 is equivalent to a wireless central station or central transceiver with respect to the present invention. Throughout this document, it should be understood that references to base stations 104 and 106 are equally applicable to a central transceiver.

Base stations often provide coverage to WCDs by dividing a geographic coverage area into multiple coverage areas known as geographic regions. Each geographic region uses a different frequency, time slot setting, code set, or code time lag to communicate with WCDs in their coverage areas, depending on the type of modulation used in the wireless communication system. Base station 104 is shown in FIG. 3 in a form where its coverage area is divided into three geographic regions, geographic region 302, geographic region 303, and geographic region 304. Geographic region 302 is shown as having a WCD 310 covered by its coverage area, geographical region 303 having a WCD

<td>312 covered by</td><td>your area of</td><td colspan="3">coverage, and region 304</td>

<td>having a</td><td>WCD 306 and WCD</td><td> 308</td><td>covered by</td><td>your area</td>

<td>of coverage.</td><td></td><td></td><td></td><td></td>

<td>In the system of</td><td>Communication</td><td>without</td><td>threads of FIG.</td><td>3, can</td>

<td>offer yourself services</td><td>without group</td><td>wires.</td><td>The services of</td><td>group without</td>

wires involve the transmission of information to multiple users simultaneously. They can also allow each WCD to send information to all WCDs or a subset of them in the system.

At least two types of group communication services are possible. One type uses a dedicated downlink, ie an air interface from a base station to a WCD, to be used as a broadcast channel. The information is transmitted on one or more broadcast channels and is received by any WCD who wishes the information. This allows for an efficient method for transmitting group data because only a single channel is used to communicate information to many WCDs.

A second method for providing group services is to independently establish a downlink with each WCD. This method consumes more system resources than the first method, but is more easily implemented on existing wireless communication systems. WCDs that want group information establish a downlink to a base station. The group information is then provided by the base station for each WCD that has established a downlink and desires the information.

In uplink, ie the air interface from a WCD to a base station, identical transmission schemes are available. A dedicated broadcast channel can be used by all WCDs within a predefined geographical area to relay information to a base station, or each WCD can establish its own uplink. The downlink and uplink scenarios can be mixed and matched. That is, in one embodiment, a dedicated broadcast channel may be used on the downlink, while on the uplink, each WCD establishes its own uplink.

In the wireless communication system of FIG. 3, WCDs are capable of communicating with base stations 104/106 using voice services or data services. Voice services are commonly used in wireless communication systems to allow audio information, typically human voice, to be transmitted by air. Typically, a frequency, time slot, or spreading code is assigned to each call by the base station 104 during the start of a voice service call. A dedicated air resource, or channel, is established between a WCD and a base station. The channel is maintained for the duration of the call. When the call ends, the channel is unassigned, or the channel is dropped down so it can be used for another call.

Data services allow WCDs to communicate by transmitting information using data packets such as Internet Protocol (IP) packets. Generally, only one channel is established between a WCD and a base station long enough to transmit data packets. After the channel is idle, for example, there is no data transmission over the channel for a predetermined time, the channel is dropped so that further data calls can be made. During data communication, WCDs are typically assigned an IP address, as would be assigned to any terminal device in the data network 118. Addresses assigned in the wireless network are often temporary addresses that are established after a WCD initiates a data connection with one or more base stations.

To receive multicast information belonging to a particular multicast group, such as sports scores, a WCD 306 user, for example, will initiate a communication with base station 104 in geographic region 304, using either voice service or the data service. A channel is established between the WCD and, for example, base station 104. If a data call has been initiated, an IP address is generally assigned to WCD 306 by router 300, or alternatively using other methods well known in the art. The user then sends a transmission to the base station 104 indicating his desire to receive the sports results multicast. The request to join a particular multicast group may be transmitted on a shared access channel, a dedicated traffic channel, a control channel, an SMS channel, or any other means of transmitting the request from WCD 306 to 104 base station. These channels are received by base station 104, but not generally by other WCDs, unlike most data networks.

The request is received by base station 104 and resubmitted to MSC 102. If the request was received as a result of a voice service call, the request may be resubmitted to MSC 102 and provided to switch 314. Switch 314, It then resends the request to PSTN 316 according to the information contained in the request, such as a telephone number associated with the source application 318. The source application 318 is generally an audio or video broadcast intended for many terminal devices simultaneously.

If the request was received by base station 104 as a result of a data service call, the request may be resubmitted to Interrupt Function (router) 300 on MSC 102. Alternatively, router 300 may not be physically connected to the service. MSC 102. Router 300 generally comprises any device capable of interfacing between data network 118 and base station 104. Router 300 is often co-positioned within MSC 102, however, this need not be the case. Routers are devices well known in the art and therefore will not be described in more detail herein.

The request from WCD 306 is received by router 300 and forwarded to data network 118 via one or more routers within data network 118, and finally to the router or access port connected to the source application 114. .

When multicast information is sent by the source application 114, it is routed through the data network 118, and then to router 300. Router 300 knows that a WCD in the coverage area of ​​base station 104, region 304 geographic, desires the multicast. The multicast information is then provided to base station 104, where it is forwarded to at least WCD 306. In another embodiment, multicast information is provided to all WCDs within the geographic region 304 coverage area using a broadcast channel dedicated to broadcast the sports results multicast. In another embodiment, multicast information is provided on a general broadcast channel dedicated to all multicast transmissions, regardless of the multicast to be transmitted.

If more than one WCD in a particular geographic region wishes to receive the same multicast as already requested by another WCD, that WCD does not have to send a request to station 104 ba if it is to receive the multicast. As explained previously, when a first WCD requests its inclusion in a multicast group, the request, or an indication thereof, is provided to all WCDs, or a subset thereof, generally by base station 104. It is desirable for base station 104 to alert WCDs to a membership request due to mutual visibility constraints. In other words, base station 104 has the ability to contact all WCDs within its coverage area, but any WCD does not necessarily have to be able to directly control other WCDs due to geographical and power constraints. Any WCD who subsequently wishes to participate in that particular multicast need not apply for multicast if he or she knows that a request from at least one other WCD within the geographic region has already requested multicast. .

In another embodiment, when a first WCD requests to be included in a particular multicast group, the request, or an indication thereof, is resubmitted to all or a subset thereof within the base station coverage area that receives the request. For example, if WCD 306 sends a request to base station 104 to receive the sports score multicast, base station 104 will resubmit the request to router 300 and will also provide an indication of the request to all WCDs, or a subset thereof, covered by the base station 104 coverage area, regardless of the geographic region in which the WCDs are operating. Therefore, if another WCD operating within the base station 104 coverage area wishes to join the same multicast group, in this example sporting results, there is no need to transmit a request to join the multicast since the previous request was provided to all or a subset of the WCDs within the coverage area of ​​the base station 104. This reduces the number of requests to be processed and transmitted by WCDs.

In addition to resubmitting a request to join a multicast group coming from a WCD to data network 118 or PSTN 316, the present invention also provides an indication to other WCDs that the request has been initiated. Thus, when a subsequent WCD wishes to join the same multicast group, the subsequent WCD does not need to transmit a request. 0 Subsequent WCD is aware that multicasting is already being provided as a result of receiving the indication stating that a previous WCD had already requested particular multicasting.

The indication that a WCD has already applied for membership in a multicast group can be transmitted to other WCDs in one of several ways. In one embodiment, when the request to join a particular multicast group is received by the base station 104, an indication of the request is sent to router 300 and also provided to all other WCDs operating within region 304. geographical This can be achieved by sending a paging message to all WCDs in the geographic region 304, or it can be achieved by any other method of transmission, including sending a SMS, or sending the request via a dedicated or common channel, traffic channel, or control channel. In another embodiment, the request is selectively provided to only certain WCDs in the geographic region 304, such as WCDs that are able to communicate using data services, or WCDs that are allowed to receive multicast, group, or broadcast communications.

In another embodiment, the indication is provided to all WCDs operating within the base station 104 coverage area, regardless of the geographic region in which the WCD is operating. In another embodiment, the request is only provided to a selected subset of WCD operating within the coverage area of ​​the base station 104.

The indication may be generated by one of a number of methods known in the art. In one embodiment, a request to join a particular multicast group is received by base station 104. Base station 104 resends the request to MSC 102, and also resends the same request to other WCDs as described above. In this embodiment, the request is received and relayed to other WCDs using one of the methods described above. In another embodiment, the indication is generated by the base station 104 when creating a message using the information contained in the request, such as an identification of the multicast group to be accessed. The indication is then created comprising the identified multicast group. Other information may be included in the indication, such as the time the request, or the indication was generated, an ID of the requesting WCD, and / or a location of the requesting WCD (such as GPS information , geographic region, or base station with which the requesting WCD is working). In another embodiment, the indication is generated in MSC 102.

From time to time, the base station 104 should search the WCDs in its coverage area to determine if multicast services are still accurate. In one embodiment, base station 104 sends a membership scan to all WCDs covered by one or more geographic regions. The adhesion search may be transmitted using a well known flood paging technique, or it may be transmitted using any other technique for sending messages through an air interface.

The membership search essentially probes each WCD to determine which multicast groups each WCD is currently interested in receiving. Each WCD responds to the membership search with a membership report indicating the multicast group (s) to which it currently belongs. However, the

WCD does not submit a membership report immediately upon receiving the membership survey. The membership report for each WCD is transmitted at different times so that other WCDs can hear the report and use the information to decide whether or not to make the report.

In one embodiment, each WCD contains a random timer associated with each multicast group to which it belongs. When the membership search is received, each of these timers starts. When the first timer, of all WCDs, times out, a membership report is transmitted by the associated WCD. The membership report is a message that indicates which multicast groups the reporting WCD belongs to. 0 The membership report is transmitted by the reporting WCD to base station 104, which forwards the message to the MSC 102 as well as to the other WCDs operating in at least the same geographic region where the WCD is operating. In another embodiment, an indication of the accession report is transmitted to the WCDs operating in the reporting WCD geographical region. 0 The indicator comprises a list of the multicast groups of which the WCD reporting was a member. In yet another embodiment, the membership report, or an indication thereof, is transmitted from base station 104 to all WCDs operating within the coverage area of ​​base station 104.

When a membership report or its indicator is received by a WCD operating in, for example, the same geographic region as the reporting WCD, the membership report or its indicator is interrogated to determine the multicast groups. that were mentioned earlier. If any of these groups are equivalent to a multicast group of which the current WCD is a member, or wish to become a member, the random timer associated with that multicast group is reset. In other words, the current WCD will not send a membership report if it knows that another WCD in the same geographic region has already reported joining the common multicast group. If the current WCD is a member of a multicast group not mentioned in the membership report, or its indicator, the timer associated with the non-referred group will continue to count down until it times out. If the WCD does not receive any membership reports for the multicast group concerned, the current WCD will send a membership report after the associated timer has timed out.

In another embodiment, a single associated timer on each WCD is started after receiving a membership search. When the first WCD times out, it sends a membership report to base station 104 indicating all the multicast groups to which it currently belongs. In an alternative embodiment, the membership report also includes any additional multicast groups that the WCD would like to join. The base station resends the membership report to MSC 102 as well as to other WCDs operating within at least the same geographic region where the reporting WCD is operating as before.

In yet another embodiment, a first membership report is sent to base station 104 using any of the methods just described by a first WCD. However, base station 104 does not immediately send the first membership report to other WCDs (although it can immediately send the first membership report to MSC 102).

In this embodiment, base station 104 waits until at least one other membership report (a second membership report) is received from a WCD operating in the same geographic region as the first WCD. In another embodiment, base station 104 waits until at least one second membership report is received from a WCD operating in the same base station coverage area as the first WCD.

In either case, base station 104 creates a list of active multicast groups within a geographic region or coverage area, whatever the case. When the first membership report is received, the identified multicast groups are added to the list. When the second membership report is received, the identified multicast groups are also added to the list. If a multicast group identified in the second membership report is already in the list, a redundant entry is not entered. After the second membership report is received and the identified multicast groups are stored in the list, a message is transmitted from base station 104 to WCDs operating within the corresponding geographic region (or base station coverage area) the two accession reports. The message indicates the sum of the multicast groups to which the first and second WCDs belong. The message is received by the WCD and interrogated to determine if transmission of a membership report is required. This is determined in the same manner as described above.

The base station 104 may, of course, collect more than two membership reports before sending the message. As each membership message is received, the identified multicast groups are added to the list. When a predetermined number of membership reports is received and processed, the message is transmitted to the geographic region (or base station coverage area) corresponding to the membership reports received.

Base station 104 (as well as other control base stations of MSC 102) periodically informs MSC 102 of multicast groups that are required by at least one WCD operating in a coverage area of ​​the respective base station. This can be accomplished in one of several embodiments.

In a first embodiment, base station 104 periodically compares active multicast groups as reported by the WCDs during membership reports to a list of multicast groups that had previously been referred to base station 104 by the WCDs, here designated as the first list. The multicast information associated with each multicast group in the first list is forwarded, as needed, by the base station 104 to the required WCD (s), geographic region, or base area coverage area. Base station 104 periodically compares active multicast groups as reported by one or more membership reports for the first list. If any multicast group listed in the first list is not identified in said or more membership reports, then multicast information associated with that group is no longer required for WCDs operating within the coverage area of ​​base station 104. . Therefore, base station 104 sends a message to MSC 102 to delete the identified multicast group from a memorized multicast group list on both router 300 and switch 314. The multicast group list memorized on router 300 or switch 314 is a list of multicast groups required for one or more base stations covered by MSC control 102. If no base station operating under the control of MSC 102 requires the identified multicast group, a message may be sent to either data network 118 or PSTN 316 indicating that the information associated with the identified multicast is no longer required. .

In a second embodiment, MSC 102 sends a message to each base station requiring the identification of any desired multicast by WCDs operating within the respective coverage area of ​​each base station. The desired new or existing multicast by at least one WCD operating within the coverage area of ​​each base station is identified in one of the methods described above and then identified in a message to MSC 102. Any multicast not identified in the message for MSC 102 is assumed to be inactive within the base station coverage area. A multicast previously forwarded to a base station is interrupted by MSC 102 if the return message from a base station does not identify that multicast as the desired multicast.

FIG. 4 is a flow chart illustrating a method of joining a first WCD to an IP multicast group as used in wireless communication system 100. In step 400, a first WCD transmits a request to join a first IP multicast to which it does not currently belong. The first WCD may already be a member of one or more other IP multicast by the time the new request is generated. The request generally comprises an identification of the requesting WCD and an identification of the first IP multicast.

At step 402, the request is received by a base station in communication with the first WCD. At step 404, an indication of the first IP multicast is transmitted to all or a subset of WCDs operating within or within a geographic region or a full coverage area of ​​the base station that received the request. The indication comprises an identification of at least one IP multicast that the first WCD wants or is currently receiving. In another embodiment, two or more multicast groups are identified in the indication, the two or more groups obtained from either a single request or from two or more different WCD requests.

&gt; In step 406, the base station resends a list of active multicast groups to MSC 102. The list comprises one or more desired IP multicast groups by at least one WCD within the base station's coverage area. At step 408, the list is received by MSC 102, either by router 300 or switch 314, depending on whether the requested IP multicast (s) is a voice or data application. The list of IP multicast groups is then forwarded to individual routers on network 118. In step 410, one or more desired IP multicast is routed through network 118 through MSC 102 to the base station that provided the list. IP multicast group information and then either for all or a subset of all WCDs operating within a geographic region, or within a full coverage area of ​​the base station.

FIG. 5 illustrates a flowchart of a base station initiating a membership scan to determine which IP multicast is required within the base station's coverage area. In step 500, a base station initiates an adhesion search by transmitting the search to all WCDs, or a subset thereof, within one or more geographic regions or a full coverage area. The membership survey invites WCDs to mention which IP multicast groups WCDs are, or would like to receive. In one embodiment, a base station countdown timer is started within the base station as shown in step 502. 0 base station countdown timer represents the maximum time that the base station has to wait to receive replies from the various WCDs in its coverage area before initiating further action on joining the various multicast.

In one embodiment, each WCD receiving membership search initiates a countdown timer for each multicast group to which it currently belongs. When the first timer within any WCD times out, a membership report is transmitted by the associated WCD. The membership report is a message indicating to which multicast group the reporting WCD belongs. 0 The membership report is transmitted by the reporting WCD to the base station.

At step 504, the base station waits for membership reports to be received from various WCDs operating within the base station's coverage area. As each membership report is received, the information associated with each report is stored in a memory device within the base station. For example, at a minimum, an identification of the referred multicast group is memorized. In addition, in one embodiment, as each membership report is received, a message is transmitted to other WCDs operating within the base station coverage area to alert the other WCDs of the multicast group just mentioned. The message can also at this time be transmitted to MSC 102.

At step 506, the base station determines whether or not the base station countdown timer has expired. If not, the base station continues to wait for incoming membership reports as shown in step 504. If the base station countdown timer has expired, the time the WCD has to respond to the last membership poll has expired, and the processing continues to step 508.

In one embodiment, at step 508, the base station generates a message indicating that multicast group (s) are desired for at least one WCD operating within the coverage area or geographic region. , from the base station. This step is an alternative to the embodiment in which a message is generated each time a membership report is received, as described in step 504. The message is transmitted to MSC 102 and then to router 300 so that the multicast can be directed to the base station and WCD wishing for multicast information.

FIG. 6 is a flow chart illustrating the method of the present invention as implemented in a WCD. In step 600, a WCD monitors a communication channel to determine if an adhesion poll has been issued by a base station. The communication channel is generally a paging channel that is available to all WCDs operating within a full base station coverage area, or in a geographic region of a base station coverage area. 0 WCD continues to listen to the communication channel until a membership survey is received.

After a membership lookup is received, processing continues to step 602 where one or more random countdown timers are started, each timer being associated with a single multicast group to which the WCD currently belongs. Each timer is set to a random value so it is highly unlikely that any two timers inside the WCD will be set to the same value. The countdown timer (s) allow an alternate response to adhesion polls. In another embodiment, only a single countdown timer is used within a WCD, regardless of how many multicast groups the WCD belongs to.

At step 604, the WCD determines whether or not any membership reports have been received. A membership report is transmitted by the base station, alerting WCDs to a previous multicast record made by another WCD. If a membership report has been received, processing continues to step 606.

At step 606, the membership report is interrogated to determine if it identifies any multicast groups to which the current WCD belongs. If there are no multicast groups identified in the membership report, processing continues to step 608. If one or more multicast groups are identified in the membership report, processing continues to step 610.

In step 610, the timer associated with the corresponding multicast group (s) is reset so that a membership report is not generated for the multicast group (s). multicast affected. Processing then continues back to step 600, where the WCD awaits further membership searches.

If no multicast group matches the current WCD multicast group list to which it currently belongs, as shown in step 606, or if a membership report is not received in step 604, processing continues to step 608.

At step 608, WCD determines if any of its countdown timers have expired. If any countdown timer has expired, a membership report is transmitted to the base station in step 612. The membership report identifies the multicast group to which the current WCD belongs. The membership report is received by the base station, where it is used to alert other WCDs not to make membership reports to the referred multicast group, as these reports are redundant. If no countdown timer has expired at step 608, processing continues back to step 604.

FIG. 7 illustrates the equipment of the present invention as implemented in a WCD shown in a functional block diagram format. WCD 700 is shown comprising processor 702, memory device 704, interface 706, transmitter 708, receiver 710, display 712 and optional countdown timer 714. The WCD 700 receives wireless transmissions from the central transponder 104 and / or 106, including adhesion searches, adhesion status indications, voice, and data information, as explained above. Transmitter 708 transmits wireless information from the WCD 700 as needed, such as adhesion status, voice, and data information when required. Transmitter 708 and receiver 710 are devices well known to those skilled in the art, and are not intended to be limited to any particular modulation technique or Industrial Standard.

Receiver 710 monitors one or more predefined communication channels to receive information from the central transceiver. Occasionally, the central transceiver broadcasts a membership poll to determine which multicast groups are required among the WCDs in the communication system 100. When the WCD 700 receives an adhesion search from the central transceiver, it is supplied to processor 702. Processor 702 in response activates one or more optional countdown timers 714, each timer 714 being associated with a single multicast group to which WCD 700 currently belongs, ie, it wishes to receive a multicast transmission. Alternatively, processor 702 executes a set of preprogrammed instructions for implementing said or more optional countdown timers. In either case, the time associated with each countdown timer is a randomly assigned value to prevent multiple simultaneous responses from multiple WCDs in the communication system 100. In an alternative embodiment, only one countdown timer is activated, regardless of how many multicast groups the WCD 700 belongs to.

Membership in multicast groups is initiated by the WCD 700 by transmitting a request to the central transceiver. The request contains information that identifies the desired multicast group (s). A WCD 700 user can select multicast groups using interface 706 (typically a keyboard or speech recognition system) and display 712. A list of available multicast groups is provided from time to time by the central transceiver, with each multicast group generally identified by a unique identifier, such as an IP address. Multicast groups are generally identified by their IP address, although other identification schemes can be used.

The receiver 710 also monitors said or more communication channels for an indication of a membership report from the central transceiver. The central transceiver transmits an indication of a membership report at predetermined intervals, such as when a membership report is received from a single WCD. In another embodiment, an indication of a membership report is transmitted upon receipt of multiple membership reports, or at predefined time intervals. In either case, the receiver 710 receives the indication of a membership report and provides the indication to processor 702. 0 Processor 702 determines which multicast group or groups are identified in the indication, and compares it with a list of multicast groups of which WCD 700 is currently a member, as stored in memory device 704. If a match is found with at least one multicast group, the countdown timer associated with the corresponding multicast group is reset, or otherwise canceled, which means that a membership report identifying the multicast group corresponding multicast will not be transmitted. In an embodiment in which a single membership report is transmitted comprising multiple multicast groups, an identification of the corresponding multicast group is not included in the membership report.

When a countdown timer expires, processor 702 generates a membership report and transmits this information to the central transceiver. The membership report identifies which multicast group WCD 702 currently belongs to. A membership report can be generated for each multicast group to which the WCD 700 currently belongs, or a single membership report containing identifying information for multiple multicast groups to which the WCD 700 currently belongs. Multicast information is stored in memory device 704 when WCD 700 registers as a member of a multicast group.

FIG. 8 illustrates the equipment of the present invention as implemented in a central transceiver shown in a functional block diagram format. Central transmitter 800 is shown, comprising transmitter 802, receiver 804, processor 806, memory device 808, and interface.

810. The central transceiver 800 may comprise a base station, wireless central station, or any other central communications point for one or more WCDs.

processor 806 occasionally generates and broadcasts an adhesion search for all or a subset of all WCDs operating within a coverage area of ​​the central transceiver 800. The coverage area can be divided into geographic coverage areas, typically known by sector. The adhesion search may be transmitted to a sector or to the full coverage area of ​​the central transceiver 800.

In response to the membership survey, WCDs transmit a membership report to the central transceiver 800 as described above. When a membership report is received by the central transceiver 800 through the 804 receiver, it is provided to the 806 processor. 0 Processor 806 may store a multicast group identified in the storage device 808, which comprises random access memory (RAM), a disk drive, a magnetic tape drive, or any other means for storing information known in the art. In one embodiment, processor 806 generates an indication of the identified multicast group (s) that is provided to transmitter 802. 0 Transmitter 802 transmits the indication to all or a subset of all WCDs operating in the full coverage area, or in one or more sectors of central transmitter 800. The alert alerts WCDs that multicast groups are currently being used by at least one WCD so that redundant membership reports can be avoided.

processor 806 may not generate an indication immediately upon receipt of a single membership report. Instead, processor 806 will wait until a predetermined event occurs. This may include receiving multiple membership reports or expiring a predetermined timer.

In addition to transmitting an indication to the WCDs, the 806 processor will occasionally provide a second WCD membership report indication to an outside entity such as a Mobile Switching Center, IWF, or a router. The second indication provides information identifying the multicast groups that are currently active by at least one WCD in the coverage area of ​​the central transceiver 800. The identifying information is then forwarded by the outside entity to the data network 118, specifically to other routers, so that the multicast information of the identified multicast groups can be provided to the central transceiver 800 and finally to any WCD that desire multicast transmission.

The foregoing description of the preferred embodiment is provided to enable any person skilled in the art to realize or use the present invention. The various modifications of these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of inventive ability. Accordingly, the present invention is not intended to be limited to the embodiments described herein but should be encompassed by a broader scope as defined by the claims.