Group communication signal methods and apparatus
Group communications methods and apparatus are described. Multicast operation is supported with the transmission characteristics, e.g., transmission power level, coding rate, and/or modulation method being selected to reliably communicate information to the end nodes in the group but not necessarily to all end nodes within the cell or sector. Thus resources can be conserved by matching transmission requirements with information on the requirements of one or more group members. The requirements for reliably reaching the end node with the worst channel conditions can, and in some embodiments is, used to determine the group transmission requirements. Power level and other transmission resource allocations can change in response to changes in group membership and/or conditions corresponding to existing group members.
This application claims the benefit of U.S. Provisional Patent Application No. 60/601,935, filed Aug. 16, 2004 which is hereby expressly incorporated by reference.
FIELD OF THE INVENTIONThis invention relates to communications systems and, more particularly, to methods and apparatus for implementing group communications and/or controlling transmission of group communication signals.
BACKGROUNDIn a typical cellular communication network, a set of geographically dispersed base stations provide wireless access to a communications infrastructure. Users with wireless communication devices, or terminals, are able to establish a direct communication link with a suitable base station and then exchange information with other users and/or end systems throughout the communication network.
IP multicast technology provides an efficient packet delivery service for group communications (e.g., one-to-many or many-to-many). The use of IP multicast reduces the bandwidth utilization for group communications. This is especially important for supporting group communications over wireless media, where bandwidth is a scarce resource.
When using IP multicast, a group of recipients is associated with an IP multicast address. A data source addresses and sends a single copy of each IP datagram intended for the group of recipients to the IP multicast group address. The routed network will replicate and forward each datagram as needed to deliver it to the routers interconnecting all of the group members. Specialized IP multicast routing protocols are used to form the delivery trees needed for copying and forwarding multicast datagrams.
IP multicast is a receiver-oriented service, in that receivers join a given multicast group to receive datagrams sent to the corresponding IP multicast group address. End systems and access routers communicate with each other via a group membership protocol, e.g., Internet Group Management Protocol (IGMP), to enable the access router to maintain information on active multicast group membership necessary for building the delivery trees.
BRIEF DESCRIPTION OF THE FIGURES
The present invention is directed to methods and apparatus for implementing group communications, e.g., multicast communications methods and apparatus. The methods and apparatus of the present invention are particularly well suited for use in wireless communications systems. In such systems different end nodes, which may be wireless terminals used by different individual users, have different communications requirements, e.g., power, timing coding rate, modulation method and/or other signal requirements. These differing signal requirements are often a function of differences in channel conditions and/or end node location which exist between different end nodes and an access node. The conditions, including channel condition and location, can change over time as an end node moves within the coverage area of an access node. Each end node may be a member of zero, one, or more multicast groups at any point in time. Access nodes serve as the end node's point of attachment, e.g., via a wireless communications link, to a communication system, e.g., cellular network. Group membership may vary with time.
Different multicast applications can be executing on different end nodes with each end node being a member of one, multiple or no multicast groups at any point in time. Within an area serviced by a transmitter, e.g., access node's sector or cell transmitter, group membership may change due to actions by the group member(s), e.g., as a user of an end node decides to enter or exit a group, e.g., by signaling a multicast application to make the desired group membership change or by terminating the multicast application. Membership can also change as the result of an end node dynamics, e.g., a mobile node, entering or leaving a cell.
The methods and apparatus of the invention are directed to the subject matter claimed in the present application.
In accordance with the present invention, transmission requirements for one or more individual group members may be determined and, in the case of a signal directed at the same time to multiple group members, the transmission requirements for the group are primarily determined from the requirements of the group member with the poorest channel conditions. In such cases, the transmission power, coding rate and/or other characteristics of the multicast signal transmitted over the wireless communications link are determined by information relating to at least one group member and the signal is not necessarily intended to reach the transmitter's full coverage area. Thus, assuming the full set of group members are close to the transmitter and experiencing good channel conditions, the transmission power may be much lower than would be required to reach the full transmitter coverage area, e.g., the full sector or cell.
While determining transmission characteristics such as power, coding rate, and/or modulation method as a function of channel condition information related to group members can be used with systems which support the two modes of operation as discussed above, this feature of the invention can be used in embodiments where a single mode of multicast transmissions is supported and each transmission is directed to multiple end nodes in a group, when the group includes more than one end node in the access node's coverage area.
The transmissions implemented by the access node may be OFDM signal transmissions. However, CDMA and other implementations are also supported and possible.
Numerous variations on the above described methods and apparatus of the present invention are possible. The detailed description which follows provides additional description of the invention as well as discussing additional exemplary embodiments, features and benefits of the invention.
DETAILED DESCRIPTION OF THE FIGURES AND THE INVENTION
The
Each access node 130, 140, 150 is depicted as providing connectivity to a plurality of N end nodes (134, 136), (144, 146), (154, 156), respectively, via corresponding access links (135, 137), (145, 147), (155, 157), respectively. In the exemplary communication system 100, each access node 130, 140, 150 is depicted as using wireless technology, e.g., wireless access links, to provide access. A radio coverage area, e.g., communications cell, 138, 148, 158 of each access node 130, 140, 150, respectively, is illustrated as a circle surrounding the corresponding access node.
The exemplary communication system 100 is subsequently used as a basis for the description of an embodiment of the invention. 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 exemplary communication system 100 depicted in
The processor 304 under control of various modules, e.g., routines, included in memory 310 controls operation of the access node 300 to perform various signaling and processing, as discussed below. The modules included in memory 310 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.
The network/internetwork interface 320 provides a mechanism by which the internal components of the access node 300 can send and receive signals to/from external devices and network nodes. The network/internetwork interface 320 includes, a receiver circuit 322 and a transmitter circuit 324 used for coupling the node 300 to other network nodes, e.g., via copper wires or fiber optic lines. The wireless communication interface 330 also provides a mechanism by which the internal components of the access node 300 can send and receive signals to/from external devices and network nodes, e.g., end nodes. The wireless communication interface 330 includes, e.g., a receiver circuit 332 with a corresponding receiving antenna 336 and a transmitter circuit 334 with a corresponding transmitting antenna 338 used for coupling the access node 300 to other network nodes, e.g., via wireless communication channels.
In the
The multicast routing/forwarding module 311 controls the operation of the access node 300 to support routing/forwarding of multicast traffic packets. The multicast routing/forwarding module 311 may use any one of a variety of multicast routing protocols, e.g., Distance Vector Multicast Routing Protocol (DVMRP), Protocol Independent Multicast (PIM), etc. The multicast routing/forwarding information 312 includes, e.g., the multicast routing and/or forwarding tables indicating the interfaces between which multicast packets corresponding to specific groups should be copied and forwarded. The group membership module 313 controls the operation of the access node 300 to support managing group membership information on interfaces of the access node 300. The group information 314 includes, e.g., the set of groups for which there are active members connected to the access node 300 via the wireless interface 330 and specific information pertaining to each such group. The member information 315 includes, e.g., specific information pertaining to each group member connected to the access node 300 via the wireless interface 330. Both the group information 314 and member information 315 are more fully described subsequently.
The transmission cost estimation module 316 computes a cost estimate corresponding to the transmission of multicast information (e.g., packets or a fixed number of information bits) to one or more members in a group. In some embodiments of the invention the estimated cost is a function of one or more determined transmission characteristics, e.g., power, bandwidth, time, code rate. In some embodiments of the invention, the determined transmission characteristics are a function of the channel condition and or channel variation (e.g., signal to noise ratio, error rate). In accordance with some embodiments, information used for cost estimation as well as the results are included in the group information 314 and member information 315 stores.
The multicast transmission mode determination module 317 determines the preferred mode for transmission of multicast information (e.g., packets) for a particular multicast group. In some embodiments, the preferred multicast packet transmission mode is determined based on the number of group members. For example, if the number of group members is less than or equal to some threshold N, a separate copy of each multicast packet is transmitted to each group member, while if the number of group members is greater than the threshold N, a single copy of each multicast packet is transmitted to the set of group member. In some embodiments, the preferred multicast packet transmission mode is determined based on the relative estimated costs for transmitting information separately to each member (e.g., unicast directed transmissions) versus transmitting information simultaneously to the set of group members (e.g., multicast directed transmissions). In accordance with some embodiments, information used for multicast transmission mode determination as well as the results are included in the group information 314 and member information 315 stores.
The multicast control module 318 controls the overall operation of the access node 300 to support adaptively controlling the mode and/or characteristics of transmitting multicast information (e.g., packets) via the wireless interface 330.
Thus, the multicast control module 318 exchanges signals and/or information with other modules included in memory 310, e.g., group information 314, member information 315, transmission cost estimation module 316, and multicast transmission mode determination module 317. The multicast control module 318 implements switching between modes of operation, transmission power levels, modulation methods and coding rates based on determinations and/or information provided by the various other modules including the transmission control module 319 and multicast transmission mode determination module 317.
If the number of group members does not exceed the pre-determined threshold N, a separate copy of the multicast packet is transmitted to each group member, steps 706, 708, 710. Thus, in step 706 a separate copy of the multicast packet is made for each member of the group, in step 708 transmission characteristics for sending a copy to each member of the group are determined, and in step 710 the individual copies are separately transmitted to each group member using transmission resources specifically assigned, allocated, or associated with each group member.
Alternatively, if the number of group members does exceed the pre-determined threshold N, a single copy is transmitted to the set of members in the group, steps 712, 714. Thus, in step 712 transmission characteristics for sending a copy to the set of members in the group are determined, and in step 714 a copy of the multicast packet is transmitted to the set of members in the group using shared transmission resources that are monitored by each group member. In either case, processing ends in step 716.
The procedure defined by the first flowchart 800 in
In step 810, the estimated costs, U and M, corresponding to the two modes of operation, are compared. If the estimated cost U is less than the estimated cost M, then the preferred multicast packet transmission mode is set to Unicast in step 812, otherwise the preferred multicast packet transmission mode is set to Multicast in step 814. Step 816 optionally adds a delay, before returning to step 802 and repeating the procedure, to control the frequency of the computations.
The procedure defined by the second flowchart 850 in
If the preferred multicast packet transmission mode is Unicast, a separate copy of the multicast packet is transmitted to each group member, steps 856, 858. Thus, in step 856 a separate copy of the multicast packet is made for each member of the group and in step 858 the individual copies are separately transmitted to each group member using transmission resources specifically assigned, allocated, or associated with each group member and using transmission characteristics as determined during the last execution of step 802.
Alternatively, if the preferred multicast packet transmission mode is Multicast, a single copy is transmitted to the set of members in the group, step 860. Thus, in step 860 a copy of the multicast packet is transmitted to set of members in the group using shared transmission resources that are monitored by each group member and using transmission characteristics as determined during the last execution of step 804. In either case, processing ends in step 862.
In the exemplary group information 314 table, the estimated multicast mode transmission cost in column 1004 may be, and in some embodiments is, a function of the determined multicast transmission characteristics in column 1003. Note however, that the estimated unicast mode transmission cost in column 1007 of the group information 314 table may be, and in some embodiments is, a function of the individual estimated unicast transmission cost corresponding to each group member listed in column 1002, where the individual estimated unicast transmission cost corresponding to each group member is shown in column 1053 of the member information 315 table. For each group, e.g., row, the preferred multicast transmission mode in column 1005 is set to Multicast if the estimated multicast mode transmission cost in column 1004 is lower than the estimated unicast mode transmission cost in column 1007, and is set to Unicast otherwise. Note that alternative cost estimation and mode determination functions are used in various embodiments of the present invention.
The member information 315 table includes columns (a) 1051 identifying a group member/end node, (b) 1055 channel condition and/or location information for the individual end node, (c) 1052 indicating the determined transmission characteristics for separately transmitting information to the end node, and (c) 1053 indicating the estimated cost for separately transmitting information to the end node. Each row (1061, 1062, 1063, 1064, 1065) of the member information 315 table, represents the information associated with a particular end node (A, B, C, D or E). The member information 315 may be, and in some embodiments is, updated as the conditions/location corresponding to the end node changes. Note that an end node may be a member of multiple groups, but need not be listed in the member table more than once. For example, end node 10.2.1.10 (row 1063 of the member information 315 table) is indicated as a member of group 224.225.1.6 (row 1021 and column 1002 of the group information 314 table) and group 224.225.1.9 (row 1022 and column 1002 of the group information 314 table).
For group 224.225.1.6, row 1021′″, note that there are changes to the determined multicast transmission characteristics in column 1003′″, the estimated multicast mode transmission cost in column 1004′″, and the estimated unicast mode transmission cost in column 1007′″, as compared to the same row/columns in
For group 224.225.1.9, row 1022′″, note that there are changes to group membership in column 1002′″ and other columns, as compared to the same row/columns in
Thus,
In some 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 the network nodes may use IP packets, e.g., datagrams.
Various features of the present invention are implemented using modules. Such modules may be implemented using software, hardware or a combination of software and hardware. Many of the above described methods or method steps can be implemented using machine executable instructions, such as software, included in a machine readable medium such as a memory device, e.g., RAM, floppy disk, etc. to control a machine, e.g., general purpose computer with or without additional hardware, to implement all or portions of the above described methods. Accordingly, among other things, the present invention is directed to a machine-readable medium including machine executable instructions for causing a machine, e.g., processor and associated hardware, to perform one or more of the steps of the above-described method(s).
Numerous additional variations on the methods and apparatus of the present invention described above will be apparent to those skilled in the art in view of the above description of the invention. Such variations are to be considered within the scope of the invention. The methods and apparatus of the present invention may be, and in various embodiments are, used with code division multiple access (CDMA), orthogonal frequency division multiplexing (OFDM), or various other types of communications techniques which may be used to provide wireless communications links between access nodes and mobile nodes. In some embodiments the access nodes are implemented as base stations which establish communications links with mobile nodes using OFDM and/or CDMA. In various embodiments the mobile nodes are implemented as notebook computers, personal data assistants (PDAs), or other portable devices including receiver/transmitter circuits and logic and/or routines, for implementing the methods of the present invention.
Claims
1. A method of operating an access node servicing a transmission area, the method comprising:
- storing, at a first point in time, a first set of group membership information including a first group identifier corresponding to a first group and a first set of end node identifiers corresponding to a first set of end nodes which are members of said first group at said first point in time;
- receiving a first set of packets including said first group identifier corresponding to said first group;
- determining at least one of a transmission power level, coding rate, and modulation method to be used for transmitting packets to the end nodes which are indicated by said first set of group membership information to be members of said first group, said at least one of a transmission power level, coding rate, and modulation method being determined as a function of information relating to a condition associated with at least one group member; and
- transmitting, using said determined at least one of a transmission power level, coding rate, and modulation method a copy of said first set of packets, said transmitted copy of the first set of packets being directed to a plurality of said group members.
2. The multicast communications method of claim 1, wherein said determined at least one of a transmission power level, coding rate, and modulation method is a power level which is lower than a power level which would be required to reach all end nodes in said serviced transmission area but is sufficient to reach all the end nodes in said first group.
3. The method of claim 2,
- wherein said condition is a channel condition;
- wherein said transmission area is a cell; and
- wherein said determined transmission power level is insufficient to reach all end nodes in said serviced transmission area at a given coding rate but is sufficient to reach all end nodes in said first group.
4. The method of claim 2,
- wherein said condition is a channel condition; and
- wherein said transmission area is a sector.
5. The method of claim 4, wherein said condition is a location condition.
6. The multicast communications method of claim 1, wherein said determined at least one of a transmission power level, coding rate, and modulation method is a power level and wherein said determining step is dynamically performed to adjust the transmission power level as a function of a channel condition associated with the end node in said first group having the worst estimated channel conditions over a period of time.
7. The multicast communications method of claim 1, wherein said determined at least one of a transmission power level, coding rate, and modulation method is a coding rate which is higher than a lower coding rate which would be required to reach all end nodes in said serviced transmission area at a given transmission power level but is sufficient to reach all end nodes in said first group.
8. The multicast communications method of claim 1, further comprising:
- storing, at a second point in time, updated group membership information, said updated group membership information including the first group identifier corresponding to the first group and a second set of end node identifiers corresponding to a second set of end nodes which are members of said first group at said second point in time;
- receiving a second set of packets including said first group identifier corresponding to said first group;
- determining at least one of a transmission power level and coding rate to be used for transmitting a copy of said second set of packets to the end nodes which are indicated by said updated set of group membership information to be members of said first group, said at least one of a transmission power level and coding rate being determined as a function of information relating to a condition associated with at least one group member; and
- transmitting a copy of said second set of packets to the end nodes indicated by said updated set of group membership information to be members of said first group.
9. The method of claim 8, wherein the first group includes different end node at said first and second times.
10. The method of claim 8, wherein the first group has the same end nodes in said first group at said first and second times but there has been a change in the channel condition associated with the at least one group member, said at least one group member being the end node in said first group with the worst channel conditions.
11. The method of claim 8, wherein the power level used to transmit said copy of said second set of packets is different from the power level used to transmit said copy of said first set of packets.
12. The multicast communications method of claim 8,
- wherein said determined at least one of a transmission power level and coding rate to be used for transmitting a copy of said second set of packets is a power level; and
- wherein said determining step is performed to select the transmission power level so that the transmitted copy of said second set of packets will be transmitted with sufficient power to reach each of the end nodes indicated to be members of said first group by said updated set of group membership information.
13. The multicast communications method of claim 11,
- wherein said determined at least one of a transmission power level and coding rate to be used for transmitting a copy of said second set of packets is a coding rate; and
- and wherein said determining step is performed to select the coding rate so that the transmitted copy of said second set of packets will be transmitted with a coding rate sufficient to reach each of the end nodes indicated to be members of said first group by said updated set of group membership information, the determined coding rate being higher than a lower coding rate which would be required to reach all end nodes in said serviced transmission area given a transmission power level which is used to transmit said copy of said second set of packets.
14. The method of claim 1, further comprising:
- storing, at said first point in time, a second set of group membership information including a second group identifier corresponding to a second group and a second set of end node identifiers corresponding to a second set of end nodes which are members of said second group at said first point in time;
- receiving a second set of packets including said second group identifier corresponding to said second group;
- determining at least one of a transmission power level and coding rate to be used for transmitting packets to the end nodes which are indicated by said second set of group membership information to be members of said second group, said at least one of a transmission power level and coding rate being determined as a function of information relating to a condition associated with at least one member of said second group; and
- transmitting a copy of said second set of packets using said determined at least one of a transmission power level and coding rate, said transmitted copy of the second set of packets being directed to a plurality of said group members.
15. An apparatus for servicing a transmission area, comprising:
- memory including, at a first point in time, a first stored set of group membership information including a first group identifier corresponding to a first group and a first set of end node identifiers corresponding to a first set of end nodes which are members of said first group at said first point in time;
- a receiver for receiving a first set of packets including said first group identifier corresponding to said first group;
- a transmission control module for determining at least one of a transmission power level and coding rate to be used for transmitting packets to the end nodes which are indicated by said first set of group membership information to be members of said first group, said at least one of a transmission power level and coding rate being determined as a function of information relating to a condition associated with at least one group member; and
- a transmitter coupled to said transmission control module for transmitting, using said determined at least one of a transmission power level and coding rate, a copy of said first set of packets, said transmitted copy of the first set of packets being directed to a plurality of said group members.
16. The apparatus of claim 15, wherein said determined at least one of a transmission power level and coding rate is a power level which is lower than a power level which would be required to reach all end nodes in said serviced transmission area but is sufficient to reach all the end nodes in said first group.
17. The apparatus of claim 16,
- wherein said condition is a channel condition; and
- wherein said transmission area is a cell.
18. The apparatus of claim 16,
- wherein said condition is a channel condition; and
- wherein said transmission area is a sector.
19. The apparatus of claim 16, wherein said condition is a location condition.
20. The apparatus of claim 15, wherein said determined at least one of a transmission power level and coding rate is a power level and wherein said transmission control module includes:
- means for adjusting the determined transmission power level in response to changes in channel condition information, as a channel condition associated with the end node in said first group having the worst channel conditions changes over time.
21. The apparatus of claim 15, wherein said determined at least one of a transmission power level and coding rate is a coding rate which is higher than a lower coding rate which would be required to reach all end nodes in said serviced transmission area given a transmission power level which is used but is sufficient to reach all end nodes in said first group.
22. The apparatus of claim 21, further comprising:
- a group membership control module for updating group membership information;
- within said memory, at a second point in time, a stored set of updated group membership information, said updated group membership information including the first group identifier corresponding to the first group and a second set of end node identifiers corresponding to a second set of end nodes which are members of said first group at said second point in time, the first group having different end node membership at said first and second times;
- wherein said receiver includes means for receiving a second set of packets including said first group identifier corresponding to said first group; and
- wherein said transmission control module includes means for determining at least one of a transmission power level and coding rate to be used for transmitting a copy of said second set of packets to the end nodes which are indicated by said updated set of group membership information to be members of said first group, said at least one of a transmission power level and coding rate being determined as a function of information relating to a condition associated with at least one group member.
23. The apparatus of claim 22, wherein the power level determined to be used to transmit said copy of said second set of packets is different from the power level used to transmit said copy of said first set of packets.
24. The apparatus of claim 22,
- wherein said determined at least one of a transmission power level and coding rate to be used for transmitting a copy of said second set of packets is a power level; and
- wherein said transmission control module includes:
- means for selecting the transmission power level so that the transmitted copy of said second set of packets will be transmitted with sufficient power to reach each of the end nodes indicated to be members of said first group by said updated set of group membership information.
25. The apparatus of claim 23,
- wherein said determined at least one of a transmission power level and coding rate to be used for transmitting a copy of said second set of packets is a coding rate;
- and wherein said transmission control module includes: means for selecting the coding rate so that the transmitted copy of said second set of packets will be transmitted with a coding rate sufficient to reach each of the end nodes indicated to be members of said first group by said updated set of group membership information, the determined coding rate being higher than a lower coding rate which would be required to reach all end nodes in said serviced transmission area given a transmission power level which is used to transmit said copy of said second set of packets.
26. The apparatus of claim 15,
- wherein at said first point in time said memory further includes a stored second set of group membership information including a second group identifier corresponding to a second group and a second set of end node identifiers corresponding to a second set of end nodes which are members of said second group at said first point in time; and
- wherein said transmission control module further includes: means for determining at least one of a transmission power level and coding rate to be used for transmitting packets to the end nodes which are indicated by said second set of group membership information to be members of said second group, said at least one of a transmission power level and coding rate being determined as a function of information relating to a condition associated with at least one member of said second group.
Type: Application
Filed: Aug 16, 2005
Publication Date: Mar 9, 2006
Inventors: M. Corson (Gillette, NJ), Rajiv Laroia (Basking Ridge, NJ), Alan O'Neill (Henley Beach), Vincent Park (Budd Lake, NJ), Murari Srinivasan (Palo Alto, CA), Sathyadev Uppala (Whitehouse Station, NJ)
Application Number: 11/204,744
International Classification: H04L 12/56 (20060101); H04L 12/28 (20060101);