Abstract:
Group communications methods and apparatus are described. In particular, methods for granting a mobile device access to a communications resource, e.g., the right to transmit data, associated with a group are described. User requests for the communications resource are suppressed by the corresponding mobile device, for periods during which the communications resource has been granted to another mobile device. A mobile device may store a suppressed user request so that a resource request signal may be transmitted after the communications resource has been released by the mobile device that was previously granted the resource. In this manner requests that cannot be granted are not transmitted, increasing communications efficiency as compared to systems where requests are not suppressed at the mobile devices. A priority scheme is used in some embodiments to determine whether or not a request should be suppressed while another device has been granted the communications resource.

Description:
RELATED APPLICATIONS  
       [0001]     The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/301,239, filed on Jun. 27, 2001, titled “METHODS AND APPARATUS FOR USING SIP SIGNALING TO SUPPORT GROUP COMMUNICATIONS OVER FLASH-OFDM”. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to methods and apparatus for supporting group communications.  
       BACKGROUND  
       [0003]     A group communications system allows a plurality of users to participate in a group communication session with each other through a plurality of corresponding user communication devices interconnected through a communications network. Such a system may also include a controller device to facilitate coordination of communications in the group and access to communication resources associated with the group, i.e., the control device may assist with “floor control”. One purpose of floor control is to ensure that only one user communication device is transmitting data at any one time, while other user communication devices associated with the group communication session only receive data during the same time. Floor control also provides the method with which the right to transmit data and access to communication resources associated with the group are shared between the plurality of user devices. This typically involves user communication devices sending “floor request” signals to the controller device and the controller device “granting the floor” to user devices according to some policy, e.g., first come first served.  
         [0004]     While floor control functions can apply to any form of data communications, they are particularly useful in voice communications, since during a conversation amongst a group of people it is beneficial if there is only one speaker at any one time. Note that digitized and packetized voice is simply a subset of data communications.  
         [0005]     The one sender many receivers property of a group communications session is exploited so that communication resources for sending data are only required by a single user communication device at a time, while communication resources for receiving data are required by the other user communication devices in the group. This is particularly beneficial when communication resources from the network to the user communication devices (downlink) are relatively in abundance, while communication resources from the user communication devices towards the network (uplink) are somewhat constrained. This is typical of cellular communications systems, which use wireless technology between the user communication devices and the network.  
         [0006]     Some cellular communication systems, also allow a user communication device to operate in either a receive-only mode or a receive-transmit mode, where a user communication device that is in the receive-only mode consumes less system resources. In such systems, operation in the receive-transmit mode requires the use of additional control channels and thus increases overhead. Typically, transition of a user communication device between modes of operation is not instantaneous; therefore, if a user communication device transitions to the receive-transmit mode even to send a small amount of traffic, the device may remain in that mode consuming a larger percentage of system resources for a longer period of time. Secondly, system resources may also be consumed for signaling associated with the transitions between modes. Finally, a user communication device may consume power at a higher rate while in the receive-transmit mode. Thus the cost associated with sending even a small amount of traffic in the uplink may be significant and should be avoided when possible.  
         [0007]     While group communications may be inherently well suited for cellular communication systems that have an ability to send downlink traffic to multiple user communication devices simultaneously, there is need for a floor control system that minimizes uplink signaling. In particular, there is a need for floor control system that minimizes the likelihood that a user communication device will transition to receive-transmit mode to send a floor request signal that will be rejected by the controller device.  
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0008]      FIG. 1  illustrates a network diagram of a group communications system implemented in accordance with an exemplary embodiment of the invention.  
         [0009]      FIG. 2  illustrates a controller node implemented in accordance with the present invention.  
         [0010]      FIG. 3  illustrates an end node implemented in accordance with the present invention.  
         [0011]      FIG. 4  illustrates signaling performed in the exemplary system as part of the processes of initiating and conducting a group o communication session between a first end node and another end node in accordance with an exemplary embodiment of the invention.  
         [0012]      FIG. 5  illustrates the state transition diagram of an end node implemented in accordance with an exemplary embodiment of the invention  
         [0013]      FIG. 6  illustrates the state transition diagram of an end node implemented in accordance with another exemplary embodiment of the invention 
     
    
     SUMMARY OF THE INVENTION  
       [0014]     Methods and apparatus of the present invention can be used to support group communications between a plurality of end nodes interconnected via a communications system, e.g., network. End nodes may be implemented as wireless devices that include receiver and transmitter circuitry to support communications with wireless access nodes via a wireless communications channel. End nodes may be, for example, mobile devices and may include an IP host protocol stack. The access nodes may be, for example, base stations in a cellular communications system and may also function as an IP access router. The communications system, e.g., network, implemented in accordance with the invention includes a group communications controller node that assists in coordination of group communications and controls access to communications resources associated with a group and/or group communications session. The group communications controller node may be, for example, a server and may also include an IP protocol stack. IP packets may be used for the exchange of both data and control signaling between nodes in the system. In either case, delivery of IP packets from a source node to the targeted destination node or nodes may use either unicast or multicast addressing and delivery mechanisms. Control signaling implemented in accordance with the present invention may be, for example, based on the Session Initiation Protocol (SIP). In various embodiments, the group communications controller transmits resource grant messages and resource release messages using an IP multicast routing address corresponding to members of a group.  
         [0015]     An end node may include an input/output interface and one or more input/output devices that enable a user to control the device and use it for communications with the users of other similar devices. The end node may be, for example, a wireless phone with a keypad, display, microphone and speaker. In response to user input, e.g., a user resource request, an end node may exchange signaling with the group communications controller node to coordinate access to resources, e.g., the right to transmit data, associated with a group or group communications session. As part of the exchange signaling the end node may transmit a resource request to the controller node.  
         [0016]     An end node implemented in accordance with the present invention is capable of operating such that it suppresses user requests for group communications resources, when the resource request would not be granted by the group communications controller node. This suppress mode of operation may be entered by an end node in response to a message from the controller node indicating a resource grant to another end node in the group. The use of a suppress mode can be advantageous when the cost associated with transmission of even a small amount of information by an end node is relatively high.  
         [0017]     In accordance with the present invention, during the suppress mode of operation an end node may store user requests. In cases where user requests are stored, the end node may later transmit a request for a group communications resources corresponding to the stored user request, after the group communications controller node has signaled that the resources have been released by the node to which they were previously granted. In accordance with the invention, the receipt of a release signal will cause an end node in the suppress mode to transition to another, e.g., idle, mode. This approach to group communications has the advantage of minimizing user interaction required to obtain group communications resources and minimizing the delay associated with obtaining resources. The group communications controller node may also further coordinate and control access to group communications resources by using scheduling techniques or methods to determine the order and timing of sending resource release signals to the end nodes within a group. Depending on the scheduling technique or method, this can be used as a way of ensuring fairness or providing priority access to group communications resources.  
         [0018]     Priority information may be maintained by end nodes and the group communications controller node. In some embodiments, priority information is included in control signaling between nodes to provide greater priority access control. The use of such additional priority information enables an end node to selectively suppress user resource requests, based on the relative priority of the requesting user or end node and the priority at which the group communications resource has been granted. Thus, even if a group communications resource is currently granted to a first user, a second user with sufficient priority may preempt the prior grant.  
         [0019]     Numerous additional embodiments, features, and advantages of the methods and apparatus of the invention are discussed in the detailed description that follows.  
       DETAILED DESCRIPTION  
       [0020]      FIG. 1  illustrates an exemplary system  300  in which a plurality of end nodes  334 ,  336 ,  344 ,  346 ,  354 ,  356 , implemented in accordance with the present invention, can participate in group communication sessions coordinated by a group communications control node  100 , also implemented in accordance with the present invention. Each end node  334 ,  336 ,  344 ,  346 ,  354 ,  356  may be a member of one or more communication groups and is capable of initiating a group communication session for the communication groups of which it is a member. The group communications controller node  100  is responsible for floor control between members of each group that are participating in a group communication session. The group communications controller node  100  may also manage access to other communication resources as with a group communication session, e.g., network resources available to a given group communications session.  
         [0021]     The  FIG. 1  exemplary system  300  depicts a network  310  that includes the group communications controller node  100  and an intermediate network node  312  connected by a network link  314 . The intermediate network node  312  in the network  310  also provides interconnectivity to network nodes that are external from the perspective of the network  310  via network link  316 . Network link  316  is connected to another intermediate network node  320 , which provides further connectivity to a plurality of access nodes  330 ,  340 ,  350  via network links  332 ,  342 ,  352 , respectively.  
         [0022]     Each access node  330 ,  340 ,  350  is depicted as providing connectivity to a plurality of N end nodes ( 334 ,  336 ), ( 344 ,  346 ), ( 354 ,  356 ), respectively, via corresponding access links ( 335 ,  337 ), ( 345 ,  347 ), ( 355 ,  357 ), respectively. In the exemplary system  300 , each access node  330 ,  340 ,  350  is depicted as using wireless technology to provide access. A coverage area, e.g., communications cell,  338 ,  348 ,  358  of each access node  330 ,  340 ,  350 , respectively, is illustrated as a circle surrounding the corresponding access node.  
         [0023]     Alternative embodiments of the invention include various network topologies, where the number and type of network nodes, the number and type of links, and the interconnectivity between nodes may differ from that of the system  300  depicted in  FIG. 1 .  
         [0024]      FIG. 2  provides a detailed illustration of the exemplary group communications controller node  100  implemented in accordance with the present invention. The exemplary group communications controller node  100 , depicted in  FIG. 2 , is a more detailed representation of the group communications controller node  100 , depicted in  FIG. 1 . In the  FIG. 2  embodiment, the group communications controller node  100  includes a processor  104 , a network/internetwork interface  106  and memory  108 , coupled together by bus  110 . Accordingly, via bus  110  the various components of the group communications controller node  100  can exchange information, signals and data. The elements  104 ,  106 ,  108 ,  110  of the group communications controller node  100  are located inside a housing  102 . The network/internetwork interface  106  provides a mechanism by which the internal components of the group communications controller node  100  can send and receive signals to/from external devices and network nodes. The network/internetwork interface  106  includes, a receiver circuit  120  and a transmitter circuit  122  used for coupling the node  100  to other network nodes, e.g., via fiber optic lines.  
         [0025]     The processor  104  under control of various modules, e.g., routines, included in memory  108  controls operation of the group communications controller node  100  to perform various signaling, floor control, resource granting and other operations as will be discussed below. The modules included in memory  108  are executed on startup or as called by other modules. Modules may exchange data, information, and signals when executed. Modules may also share data and information when executed. In the  FIG. 2  embodiment, the memory  108  of group communications controller node  100  of the present invention includes a group communications controller module  112  and communications data  114 .  
         [0026]     The group communications controller module  112  controls operation of the group communications controller node  100  to support floor control of group communication sessions. Thus, module  112  controls processing of received signals or messages requesting and/or releasing the communications resource and sending of subsequent signals or messaging as required to grant the resource or announce the release of said resource. Communications data  114  includes, e.g., parameters, configuration information, resource information, communication session information, end node status information and/or other information relating to end node interaction and/or group communications sessions. In particular, communications data  114  may include group information  116 , e.g., information about the members of each group and the status of any corresponding group communication session, and priority information  118 , e.g., information about the relative priority of group members. The group communications controller module  112  may access and/or modify the communications data  114  when executed. Thus, the group communications controller module  112  may access and update the group information  116  and priority information  118 .  
         [0027]      FIG. 3  provides a detailed illustration of an exemplary end node  200  implemented in accordance with the present invention. The exemplary end node  200 , depicted in  FIG. 3 , is a detailed representation of an apparatus that may be used as any one of the end nodes  334 ,  336 ,  344 ,  346 ,  354 ,  356 , depicted in  FIG. 1 . In the  FIG. 3  embodiment, the end node  200  includes a processor  204 , a wireless communication interface  206 , a user input/output interface  230  and memory  208  coupled together by bus  210 . Accordingly, via bus  210  the various components of the end node  200  can exchange information, signals and data. The exemplary end node  200  also includes a user input device  232 , e.g., keypad, a user output device  234 , e.g., display, an audio input device  236 , e.g., microphone, and an audio output device  238 , e.g., speaker, which are coupled to bus  210  via the user input/output interface  230 . Thus, user input/output devices  232 ,  234 ,  236 ,  238  can exchange information, signals and data with other components of the end node  200  via user input/output interface  230  and bus  210 . The elements  204 ,  206 ,  208 ,  230 ,  232 ,  234 ,  236 ,  238 ,  210  of the end node  200  are located inside a housing  202 .  
         [0028]     The wireless communication interface  206  provides a mechanism by which the internal components of the end node  200  can send and receive signals to/from external devices and network nodes. The wireless communication interface  206  includes, e.g., a receiver circuit  220  with a corresponding receiving antenna  224  and a transmitter circuit  222  with a corresponding transmitting antenna  226  used for coupling the node  200  to other network nodes, e.g., via wireless communications channels.  
         [0029]     The processor  204  under control of various modules, e.g., routines, included in memory  208  controls operation of the end node  200  to perform various signaling, resource requesting/releasing, data communications and other operations as will be discussed below. The modules included in memory  208  are executed on startup or as called by other modules. Modules may exchange data, information, and signals when executed. Modules may also share data and information when executed. In the  FIG. 3  embodiment, the memory  208  of end node  200  of the present invention includes a group communications module  212  and communications data  214 .  
         [0030]     The user input/output interface  230  and associated devices  232 ,  234 ,  236 ,  238  provide the means by which a user can operate the end node  200  to accomplish certain tasks. In particular, the user input device  232  and user output device  234  provide the functionality that allows a user to control the end node  200  and applications, e.g., modules, programs, routines and/or functions, that execute in the memory  208  of the end node  200 . The audio input device  236  and audio output device  238  provide the functionality necessary to utilize the end node  200  for a voice communication session with another end node or group of end nodes.  
         [0031]     The group communications module  212  controls operation of the end node  200  to participate in group communication sessions. Thus, module  212  controls sending of signals or messaging as required to request or release group communications resources and processing of received signals or messages granting and releasing group communications resources. Communications data  214  includes, e.g., parameters, configuration information, communication session information and/or other information relating to group communications sessions. In particular, communications data  214  may include configuration information  216 , e.g., group membership information and relative priority of the encompassing end node  200  and/or associated user, and operational information  218 , e.g., status of an active group communication session. The group communications module  212  may access and/or modify the communications data  214  when executed. Thus, the group communications module  212  may access and update the configuration information  216  and operational information  218 .  
         [0032]      FIG. 4  provides an example of the signaling that may occur between an exemplary set of communications nodes  500  implemented according to this invention. The  FIG. 4  embodiment comprises a plurality of end nodes  200 ,  200 ′ implemented according to this present invention, e.g., as shown in  FIG. 3 , and a group communications controller node  100  also implemented according to this present invention, e.g., as shown in  FIG. 2 , where the end nodes  200 ,  200 ′ and the group communications controller node  100  are part of communications system, e.g., as shown in  FIG. 1 , and thus are able to exchange communications signals, e.g., messages.  FIG. 4  also depicts a plurality of users  502 ,  502 ′, each associated with a corresponding end node  200 ,  200 ′, respectively. Although not shown in  FIG. 4 , users  502 , ‘ 502 ’ interact with corresponding end nodes  200 ,  200 ′ via the user input/output interface  230  and the associated devices  232 ,  234 ,  236 ,  238  shown in  FIG. 3 . Users  502 ,  502 ′ operate their corresponding end nodes  200 ,  200 ′ to participate in a group communication sessions, while the group communications controller node  100  is operates to provide floor control of said group communications session.  
         [0033]     The following describes the events, signals, and operations associated with controlling access to a group communications resource associated with a group communications session. The arrows in  FIG. 4  represent user input operations and signals, e.g., messages, used between users  502 ,  502 ′, end nodes  200 ,  200 ′ and group communications controller node  100  to request and grant access to the resources associated with the group communication session which in this case includes the right to send data. It is assumed that initially the end nodes are in an idle mode of operation and the group communications resource is available, i.e., no users associated with the group communications session are sending data.  
         [0034]     In  FIG. 4 , the user  502  of end node X  200  performs a URR (User Resource Request) input operation  510 , e.g., presses a key, causing an internal signal to be generated by user input device  232  of end node X  200 . The URR input operation  510  and corresponding internal signal indicate that the user  502  of end node X  200  wants to send data. In response to the URR input operation  510 , end node X  200  accesses its internal communications data  214  to determine if the group communications resource is currently granted to another group member. Since its internal communications data  214  indicates that the resource is available (in accordance with the initial assumption of this example), end node X  200  sends a corresponding DRR (Device Resource Request) signal  512  to the group communications controller node  100 . The DRR signal  512  indicates that end node X  200  wants to send data to a particular group.  
         [0035]     Upon reception of the DRR signal  512 , the group communications controller node  100  accesses its internal communications data  114  to determine if the group communications resource should be granted in response to the DRR signal  512 . In one embodiment of the present invention, this operation may simply be a determination of whether the requested group communications resource is available or is currently granted to another group member. In alternative embodiments, this operation may also include an assessment of the relative priority of the requesting group member and other factors to determine if the resource request should be granted, i.e., even if the resource is currently granted the relative priority of the group members could be used to selectively preempt an existing grant upon reception of a request from a higher priority user. In the  FIG. 4  example, since the resource is available, the group communications controller node  100  grants end node X  200  and the corresponding user  502  the right to send data by sending a RG (Resource Grant) signal  514 ,  514 ′ to end nodes, e.g., all end nodes, associated with members of the group. The RG signal  514  sent to end node X  200  includes sufficient information to indicate that the group communications resources has been granted to end node X and/or the corresponding user  502 , while the RG signals  514 ′ sent to end nodes associated with other group members need only indicate that the resource has been granted. In one embodiment of the present invention, the RG signal  514  sent to end node X  200  includes information that can be used to match the RG signal  514  with the previously sent DRR signal  512 , e.g., a sequence number and/or identification value. In alternative embodiments, the RG signal  514  may also include information that identifies end node X  200  and/or the corresponding user  502 . In some embodiments, the RG signals  514 ,  514 ′ may include information that indicates the relative priority of the group member to which the group communications resource has been granted. Also, in some embodiments, the RG signals  514 ,  514 ′ sent to end nodes, e.g., all end nodes, associated with members of the group may contain the same information, in which case the RG signals  514 ,  514 ′ may be sent using broadcast or multicast.  
         [0036]     Upon reception of the RG signal  514 , end node X  200  enables its corresponding user  502  to start transmitting data to the group, e.g., sending voice via the audio input device  236  shown in  FIG. 3 . In some embodiments, end nodes  200 ,  200 ′ may also provide an indication, e.g., visual and/or auditory signal, to their corresponding users  502 ,  502 ′, respectively, that the group communications resource has been granted. Reception of the RG signal  514 ′ by end node Y  200 ′ indicates that the group communications resource has been granted to another member of the group, in this case user  502  of end node X  200 . Upon reception the RG signal, end node Y  200 ′ changes from an idle mode to a suppression mode of operation, during which end node Y  200 ′ will suppress resource request attempts made by its corresponding user  502 ′. While in the suppression mode, end node Y  200 ′ may receive data sent to the communications group, e.g., voice data sent from the user  502  of end node X  200 . In the exemplary embodiment end node Y also provides the received data to its corresponding user  502 ′, e.g., sending voice via the audio output device  238  shown in  FIG. 3 .  
         [0037]     The  FIG. 4  example further illustrates the events, signals and operations that occur when the user  502 ′ of end node Y  200 ′ attempts to request resources associated with the same communications group for which the resources have already been granted to the user  502  of end node X  200 . The user  502 ′ of end node Y  200 ′ performs a URR input operation  516 , e.g., presses a key, causing an internal signal to be generated by user input device  232 ′ of end node Y  200 ′. The URR input operation  516  and corresponding internal signal indicate that the user  502 ′ of end node Y  200 ′ wants to send data. In response to the URR input operation  516 , end node Y  200 ′ accesses its internal communications data  214 ′ to determine if the group communications resource is currently granted to another end node, i.e., if end node Y  200 ′ is in the suppression mode. According to one embodiment of the present invention, since its internal communications data  214 ′ indicates that the resource is currently granted to another end node and end node Y  200 ′ is in the suppression mode, end node Y  200 ′ immediately returns an error signal  518  to its corresponding user, e.g., a visual and/or auditory signal via the respective output device  234 ′,  238 ′. In an alternative embodiment, end node Y  200 ′ may store an indication that a URR input operation  516  was performed by its corresponding user  502 ′ and not return an error message. If the group communications resource is subsequently released, the stored indication that a URR input operation  516  was performed will be used to determine if a DRR signal should be sent to the group communications controller node. Also, in some embodiments, in response to the URR input operation, end node Y  200 ′ may compare the relative priority of its corresponding user  502 ′ with the priority at which the group communications resource is currently granted to another user, to determine whether a DRR signal (not shown) should be sent to the group communications controller node  100  to preempt the existing resource grant, as opposed to either sending an error signal  518  or storing an indication that a URR input operation was performed.  
         [0038]     The  FIG. 4  example also illustrates the events, signals and operations that occur when the user  502  of end node X  200  releases the resources that have been granted to it. At some point later the user  502  of end node X  200  ends its transmission of data and releases the resources by performing a URREL (user Resource Release) input operation  520  e.g., presses or releases a key, causing an internal signal to be generated by user input device  232  of end node X  200 . In response to the URREL input operation  520 , end node X  200  end node X  200  sends a corresponding DRREL (Device Resource Release) signal  522  to the group communications controller node  100 . Upon reception of the DRREL signal, the group communications controller node  100  notifies members, e.g. all members, of the group that resources for that group are now available by sending a RREL (Resource Release)  524 ,  524 ′ signal to end nodes associated with members of the group. The group communications controller node may use a variety of scheduling methods to determine the order and timing with which RREL signals  524 ,  524 ′ are sent to end nodes associated with group members. In some embodiments, the RREL signals  524 ,  524 ′ sent to end nodes associated with group members may contain the same information, in which case the RREL signals  524 ,  524 ′ may be sent using broadcast or multicast Upon reception of the RREL signal  524 ′, end node Y  200 ′ changes from suppression mode to an idle mode of operation. Provided that end node Y  200 ′ had stored an indication that a URR input operation was performed while end node Y  200 ′ was in the suppression mode, end node Y  200 ′ would immediately send a DRR signal (not shown) to the group communications controller node  100 . In some embodiments, end nodes  200 ,  200 ′ may also provide an indication, e.g., visual and/or auditory signal, to their corresponding users  502 ,  502 ′, respectively, that the group communications resource has been released. The  FIG. 4  example further illustrates a resource request from end node Y  200 ′ that occurs after the group communications resource has been released by end node X  200 . The user  502 ′ of end node X  200 ′ performs a URR input operation  526  to end node Y  200 ′. In response to the URR input operation  526 , end node Y  200 ′ sends a DRR signal  528  to the group communications controller node  100 . Upon reception of the DRR signal  528 , the group communications controller node  100 , will determine whether the resource should be granted to end node Y  200 ′, as it did for end node X  200  at the beginning of the  FIG. 4  description.  
         [0039]      FIGS. 5 and 6  depict exemplary state machines that may operate in an end node  200  implemented according to this present invention, e.g., as shown in  FIG. 3 . The end node is operated by a user member of a communications group as part of communication system, e.g., as shown in  FIGS. 1 and 4 . Group communications sessions are controlled by a group communications controller node  100  implemented according to the present invention, e.g., as shown in  FIG. 2 . In  FIGS. 5 and 6 , operational states are depicted as circles, while arrows between the states indicate state transitions according to this invention. Dotted arrows and text in parenthesis “( )” indicate features present in an alternative embodiment of this invention which is also described in detail below.  
         [0040]     The  FIG. 5  embodiment depicts three operational states, idle  602 , suppress  604  and send  606 . While in any of these states, an end node implemented according to this invention monitors the input/output interface  230  for user input operations and the communication channel for floor control signals, e.g., messages, from the group communications controller node. In idle state  602 , the end node monitors for input operations and other signals that may trigger a change in operational state. In suppress state  604 , the end node additionally operates such that it suppresses requests for resources from the user. The end node  200  transitions to the send state  606  when it has been granted the communications resource; thus, while in the send state  606 , the end node may transmit data to the group.  
         [0041]     In one embodiment of this invention, when signal RGTO (Resource Grant to Other) is received while in the idle state  602 , the end node makes a transition  620  to the suppress state, since signal RGTO indicates that resources were granted to another member of the group. In one embodiment of this invention, reception of a URR input operation while in the suppress state  604  results in the suppression of the resource request and transmission of an error message to the user indicating that resources for that group are not available and the return  622  to the same suppress state  604 . Upon reception of a RREL signal while in the suppress state  604 , indicating that the resources for said group have been released, the end node makes a transition  624  back to the idle state  602 . Reception of a RREL signal while in idle state causes the end node to return  626  to the same idle state  602 . According to this invention, when a URR input operation is received while in the idle state  602 , the end node sends a DRR signal to the group communications controller node and returns  628  to the same idle state  602 . If the controller grants the resources requested, a RGTS (Resource Grant to Self) signal will be received while the end node is still in the idle state  602 . When a RGTS signal is received while in the idle state  602 , the end node makes a transition  630  to the send state  606  and the user can now transmit data to the group. When the user data transmission is complete and the user releases the resources by performing a URREL input operation. When a URREL input operation is received while in the send state  606 , the end node makes a transition  632  from the send state  606  to the idle state  602  and sends a DRREL signal to the group communications controller node.  
         [0042]     In some alternative embodiments of this invention, a relative priority may be associated with each group member and some of the signals sent between nodes may also include an indication of relative priority. In one particular embodiment of this invention reception of a RGTO signal by a end node while in idle state  602 , cause a transition  620  to the suppress state  604  only if the priority level indicated in the RGTO signal is higher than or equal that owned by the user of the said end node. A RGTO signal indicating a lower relative priority than that owned by the user of the said end node causes the end node to return  650  to the same idle state  602 . In the latter case, the user can still request resources for this group by performing a URR input operation and interrupt, e.g., preempt, the user with a lower relative priority that has been granted access to the resources. Accordingly, reception of a RGTO signal by an end node while in the send state  606 , may indicate that the resource has been granted to another user with a higher relative priority that of said end node. In which case, the end node makes a transition  652  from the send state  606  to the suppress state  604 .  
         [0043]      FIG. 6  depicts an alternative exemplary state machine that may operated in an end node according to this invention. States and signals are the same with that of the  FIG. 5  example, with the following exceptions: the addition of a new state called the store state  608 , the addition of new transitions  640 ,  642 ,  644 , and the removal of return  622 . In this alternative embodiment of the invention, reception of a URR input operation by the end node while in suppress state  604 ′, causes a transition  640  to the store state  608 . In the store state  608 , the end node effectively stores the user requests for resources. Any additional URR input operations received while in the store state  608  cause the end node to replace the stored URR input operation information with information regarding the new URR input operation before it returns  642  to the same store state  608 . When aRREL signal is received while in this store state  608 , the end node sends a DRR signal to the group communications controller node according to the last URR input operation that was received and makes a transition  644  to the idle state  602 .  
         [0044]     In an alternative embodiment of this present invention, when the end node is in the store state  608 , it can also receive a URREL signal from the user indicating that the user no longer requires resources for this group, in which case the end node will transition (not shown in the figure) back to suppress state.  
         [0045]     In some alternative embodiments of the present invention, communications between nodes is based all, or in part, on the Internet Protocol (IP). Thus, communication of both data and/or control signaling between members of a communications group, end nodes associated with group members and the group communications controller node may use IP packets, e.g., datagrams. IP packets may be delivered to the their intended destination nodes using either unicast or multicast addressing and delivery mechanisms. The use of IP multicast is particular useful when the same information is sent from one node to a plurality of other nodes. This is typically the case for data communications between group members, and may also be the case for certain control signals that target a plurality of nodes, e.g., the RG signal  514 ,  514 ′ and the RREL signal  524 ,  524 ′ depicted in  FIG. 4 . In cases where the same information, e.g., packet payload data, is sent to a plurality of targeted nodes using unicast delivery, a separate IP packet with a copy of the information is sent by the source node to each targeted node. Alternatively, when the same information is sent to a plurality of targeted nodes using multicast delivery, a single IP packet with the information is sent by the source node and network nodes replicate the packet as required for delivery to each targeted node. Thus, IP multicast provides a more efficient means of delivering information from a source node to a group of destination nodes.  
         [0046]     In some alternative embodiments of the present invention, the exchange of control signals, e.g., messages, between nodes is based all, or in part, on the Session Initiation Protocol (SIP). SIP messaging may be used both for the initial establishment of a group communications session and for the signaling associated with arbitration and control of access to group communications resources. SIP messaging may be sent using either unicast or multicast delivery mechanisms. Group communications resource control messaging may also be unified and/or integrated with control messaging associated with establishment, maintenance and teardown of group communications session and/or with control messaging associated with maintenance of group member presence information.  
         [0047]     Additional aspects, features, methods, apparatus and exemplary embodiments which are part of the inventive methods and apparatus, to which the present patent application is directed, are described in U.S. Provisional Patent Application Ser. No. 60/301,239, filed on Jun. 27, 2001, titled “METHODS AND APPARATUS FOR USING SIP SIGNALING TO SUPPORT GROUP COMMUNICATIONS OVER FLASH-OFDM” which is cited in the related applications section of the present application and which is hereby expressly incorporated by reference.  
         [0048]     As a result of the above incorporation by reference, the text and figures of the listed provisional patent application form part of the present description. It is to be understood that the reference numerals used in the text and figures of the provisional patent application are to be interpreted in the context of the incorporated provisional application and are not to be interpreted as the same as any similarly numbered element or elements described in the above text or the figures which are included herein without the use of an incorporation by reference. It is to be further understood that mandatory language, if any, in the incorporated provisional application such as “must”, “only”, etc., is to be interpreted as being limited to the exemplary embodiments described in the provisional application and is not to be interpreted as a limitation on the embodiments, figures, and claims of the present application which are not incorporated by reference.