U.S. patent application number 13/651557 was filed with the patent office on 2013-02-21 for method and apparatus for wireless router multicast.
This patent application is currently assigned to INTERDIGITAL PATENT CORPORATION. The applicant listed for this patent is INTERDIGITAL PATENT CORPORATION. Invention is credited to Leslie M. Brooks, Kevin L. Farley.
Application Number | 20130044672 13/651557 |
Document ID | / |
Family ID | 47045825 |
Filed Date | 2013-02-21 |
United States Patent
Application |
20130044672 |
Kind Code |
A1 |
Farley; Kevin L. ; et
al. |
February 21, 2013 |
METHOD AND APPARATUS FOR WIRELESS ROUTER MULTICAST
Abstract
A system and method are provided to transmit messages in a
wireless communication network to a multicast group using a single
wireless channel. A base station processor having a plurality of
wireless channels is in communication with a plurality of
subscriber access units in a wireless communication network. The
base station processor allocates the wireless channels to the
subscriber access units for transmitting messages between the
subscriber access units and the base station processor. The base
station processor is also connected to a public access network such
as the Internet via an Internet gateway. Multicast messages are
received via the Internet gateway to be sent to a plurality of the
subscriber access units, denoted as a multicast group, in the
wireless communication network. The multicast message is sent
concurrently to each of the subscriber access units by allocating a
single wireless channel to all subscriber access units in the
multicast group. The message is sent over the single wireless
channel to all the subscriber access units in the multicast group
and received concurrently by the subscriber access units in the
multicast group.
Inventors: |
Farley; Kevin L.; (Melbourne
Beach, FL) ; Brooks; Leslie M.; (West Melbourne,
FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERDIGITAL PATENT CORPORATION; |
Wilmington |
DE |
US |
|
|
Assignee: |
INTERDIGITAL PATENT
CORPORATION
Wilmington
DE
|
Family ID: |
47045825 |
Appl. No.: |
13/651557 |
Filed: |
October 15, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09630024 |
Jul 31, 2000 |
8301137 |
|
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13651557 |
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Current U.S.
Class: |
370/312 |
Current CPC
Class: |
H04L 12/189 20130101;
H04W 76/40 20180201; H04L 45/16 20130101; H04W 40/02 20130101; H04L
12/1868 20130101; H04W 4/08 20130101 |
Class at
Publication: |
370/312 |
International
Class: |
H04H 20/71 20080101
H04H020/71 |
Claims
1. A method of multicasting messages in a wireless network
comprising: receiving a multicast message addressed to a multicast
group at a base station processor having a plurality of wireless
channels; determining a plurality of multicast group members; and
sending, over one of said wireless channels, said multicast
message, wherein the same one of said wireless channels is used to
simultaneously send said multicast message to said plurality of
multicast group members.
2. The method of claim 1 further comprising receiving said message
at each of the plurality of multicast group members via said same
wireless channel.
3. The method of claim 2 wherein receiving said message further
comprises concurrently receiving said multicast message at each of
said plurality of multicast group members.
4. The method of claim 1 wherein sending said multicast message is
preceded by: selecting, from among said plurality of wireless
channels, a multicast channel adapted to transmit said multicast
message; and sending, via one of said plurality of wireless
channels to each of the multicast group members, a paging message
indicative of said multicast channel over which to receive said
multicast message, wherein said paging message is transmitted
simultaneously to each of said multicast group members.
5. The method of claim 1 wherein said base station processor is
operable to communicate with a plurality of subscriber access units
adapted for communication in a wireless network via said plurality
of wireless channels and said multicast group members comprise a
subset of said plurality of said subscriber access units.
6. The method of claim 5 wherein determining further comprises:
performing a lookup in a routing table adapted to store entries
associating a multicast group with an interface identifier; and
performing a lookup in an interface table adapted to associate said
interface identifier with at least one of said plurality of
subscriber access units, wherein each of said plurality of
subscriber access units associated with the same interface
identifier comprises said multicast group members.
7. The method of claim 6 wherein sending further comprises:
performing a lookup in a connection table adapted to store
connection identifier entries indicative of an association between
at least one of said plurality of wireless channels and at least
one of said plurality of subscriber access units.
8. The method of claim 6 further comprising: receiving a join group
request indicative of at least one of said plurality of multicast
group members; and adding an interface entry in said interface
table indicative of an association between said at least one
multicast group member indicated in said join group request and
said multicast group.
9. The method of claim 8 further comprising receiving a join group
request indicative of at least one other of said multicast group
members; and adding an interface entry in said interface table
indicative of an association between at least one other of said
multicast group members and said multicast group.
10. The method of claim 1 wherein determining said multicast group
members further comprises: scanning said multicast message; and
parsing a group address indicative of a multicast group.
11. The method of claim 10 wherein said group address conforms to a
protocol and said parsing comprises parsing in accordance with said
protocol.
12. The method of claim 11 wherein said protocol is the Internet
Group Management Protocol (IGMP).
13. A system for multicasting messages in a wireless network
comprising: a base station processor having a plurality of wireless
channels operable to transmit a wireless message; and a plurality
of subscriber access units in communication with said base station
processor over a wireless connection and adapted to receive
messages via said plurality of wireless channels, wherein said base
station processor is operable to receive a multicast message and
simultaneously transmit said multicast message to at least one of
said plurality of subscriber access units via the same one of said
plurality of wireless channels.
14. The system of claim 13 wherein said base station processor
further comprises a routing table adapted to store entries
indicative of an association between each of said plurality of
subscriber access units and an interface, wherein said subscriber
access units corresponding to the same interface comprise a
multicast group.
15. The system of claim 14 further comprising an interface table
adapted to store entries indicative of an association between each
of said plurality of subscriber access units and a wireless
connection, wherein each of said subscriber access units in said
multicast group correspond to the same interface.
16. The system of claim 15 wherein each of said entries in said
interface table corresponds to a connection indicative of one of
said plurality of wireless channels, and wherein each of said
subscriber access units in said multicast group correspond to the
same one of said plurality of wireless channels.
17. The system of claim 14 wherein said base station processor
further comprises: a connection table adapted to store entries
indicative of an association between at least one of said plurality
of subscriber access units with at least one of said plurality of
wireless channels, wherein said connection table is indicative of a
common channel allocated to said plurality of subscriber access
units which comprise said multicast group.
18. The system of claim 14 wherein said routing table further
comprises entries including a group address and a corresponding one
of said interface IDs, wherein said group address is indicative of
one of said multicast groups.
19. The system of claim 18 wherein said group address conforms to a
predetermined protocol.
20. The system of claim 19 where said predetermined protocol is
IGMP.
21. The system of claim 14 wherein only the subset of the plurality
of subscriber access units in said multicast group decode said
multicast message.
22. The system of claim 13 further comprising a scheduler operable
to designate which of said plurality of subscriber access units
receive said multicast message on a predetermined one of said
plurality of wireless channels.
23. The system of claim 22, wherein said scheduler is further
operable to designate a plurality of subscriber access units to
receive said multicast message over the same one of said plurality
of wireless channels.
24. The system of claim 17, wherein said scheduler is further
operable to query said connection table, wherein said same one of
said plurality of wireless channels corresponds to subscriber
access units associated with a common interface ID.
25. The system of claim 24 further comprising a paging channel in
communication with said scheduler, wherein said paging channel is
operative to send a paging message to each of said plurality of
subscriber access units in said multicast group indicative of one
of said wireless channels to be used for receiving said multicast
message.
26. The system of claim 15 wherein said subscriber access units are
added to said multicast group via a join group message, wherein
said join group message is indicative of an additional subscriber
access unit and said multicast group and said base station
processor is further operative to store a new entry in said
interface table indicative of said additional subscriber access
unit and said multicast group.
27. The system of claim 15 wherein said subscriber access units are
removed from said multicast group via a leave group message,
wherein the leave group message is indicative of a deleted
subscriber access unit and said multicast group and said base
station processor is further operative to delete an entry from said
interface table indicative of said deleted subscriber access unit
and said multicast group.
28. The system of claim 13 wherein the base station processor is in
communication with an Internet gateway operable to transmit
messages via a public access network.
29. A computer program product having computer program code for
multicasting messages in a wireless network comprising: computer
program code for receiving a multicast message addressed to a
multicast group at a base station processor having a plurality of
wireless channels; computer program code for determining a
plurality of multicast group members; and computer program code for
sending, over one of said wireless channels, said multicast
message, wherein the same one of said wireless channels is used to
simultaneously send said multicast message to said plurality of
multicast group members.
30. A computer data signal including computer program code for
multicasting messages in a wireless network comprising: program
code for receiving a multicast message addressed to a multicast
group at a base station processor having a plurality of wireless
channels; program code for determining a plurality of multicast
group members; and program code for sending, over one of said
wireless channels, said multicast message, wherein the same one of
said wireless channels is used to simultaneously send said
multicast message to said plurality of multicast group members.
31. A system for multicasting messages in a wireless network
comprising: means for receiving a multicast message addressed to a
multicast group at a base station processor having a plurality of
wireless channels; means for determining a plurality of multicast
group members; and means for sending, over one of said wireless
channels, said multicast message, wherein the same one of said
wireless channels is used to simultaneously send said multicast
message to said plurality of multicast group members.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 09/630,024, filed Jul. 31, 2000, which is
incorporated by reference as if fully set forth.
BACKGROUND OF THE INVENTION
[0002] In a telecommunications network, it is often desirable to
send the same message to a group of recipients. Methods are known
for establishing a group of message recipients as a multicast
group. Such a group of recipients share a common group address for
receiving messages sent to the multicast group. A message
designated as a multicast message can then be sent to all members
of the multicast group by simply addressing the message to the
group address.
[0003] Message transmission in a telecommunications network occurs
over a variety of physical media. For example, a telecommunications
network may include wireless communication networks. Wireless
communication networks are notable because message transmission
occurs over a wireless connection via a radio channel, rather than
via a physically conductive, or wired connection which is common in
a telecommunications network. In a typical wireless communication
network, a base station processor is in communication with a
plurality of subscriber access units (subscribers). The base
station processor also maintains a wired connection to the
telecommunications network. Each of the subscriber access units is
connected to a plurality of user computing devices, such as user
PCs. In this manner, a user computing device is provided a wireless
connection to a telecommunications network through the subscriber
access unit and the base station processor in wireless
communication with the subscriber access unit.
[0004] A base station processor includes a plurality of wireless
channels for message transmission between the base station
processor and the subscriber access units. Such wireless channels
are a scarce resource in a base station processor. Accordingly, the
base station processor allocates the wireless channels among the
subscriber access units on a periodic basis as the users demand
access.
[0005] A multicast message received by a base station processor may
require delivery to a multiple of the subscriber access units which
are members of a multicast group. In a typical base station
processor, a separate channel is allocated for each of the
subscriber access units that is a member of the multicast group.
The multicast message therefore must be sent, in an iterative
manner, to each of the subscriber access units over a separate
dedicated channel allocated for each subscriber access unit. In
this manner, a multicast message results in duplicate channel
allocation and duplicate message transmission for each group member
when a multicast message is received by the base station processor
for delivery to each of the subscriber access units in the
multicast group.
SUMMARY OF THE INVENTION
[0006] It would be beneficial, therefore, to provide a method and
system for allocating a single channel for all subscriber access
units that are members of a multicast group, and sending the
message to all the subscriber access units over the single
allocated channel for concurrent receipt by the subscriber access
units that are members of the multicast group.
[0007] According to the invention, a system and method are provided
to transmit messages in a wireless communication network to a
multicast group. A base station processor having a plurality of
wireless channels is in communication with a plurality of
subscriber access units in a wireless communication network. The
base station processor allocates the wireless channels to the
subscriber access units for transmitting messages between the
subscriber access units and the base station processor on a demand
basis. The base station processor is also connected to a public
access network such as the Internet via an Internet gateway.
Multicast messages are received via the Internet gateway to be sent
to a plurality of the subscriber access units, denoted as a
multicast group, in the wireless communication network. The
multicast message is sent concurrently to each of the subscriber
access units by allocating a single wireless channel for the
multicast message to all subscriber access units in the multicast
group. The message is sent over the single wireless channel to all
the subscriber access units in the multicast group and received
concurrently by the subscriber access units in the multicast group.
A routing table stores entries associating subscriber access units
with an interface; an interface is associated with a subscriber
access units; and a wireless channel is associated with the
interface. Multiple subscriber access units can therefore be
associated with the same wireless channel used to send the
multicast message. Subscriber access units which are members of a
multicast group are associated with the same multicast group
address in the routing table.
[0008] The multicast message traffic is determined by the base
station processor which parses the incoming message traffic. The
multicast message traffic conforms to a predetermined protocol such
as the Internet Group Management Protocol (IGMP). Multicast message
conforming to this protocol is used to identify multicast groups,
identify requests for subscribers to leave and join the multicast
groups, and determine which group a particular message is directed
to.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The foregoing and other objects, features and advantages
will be apparent from the following more particular description of
particular embodiments of the invention, as illustrated in the
accompanying drawings in which like reference characters refer to
the same parts throughout the different views. The drawings are not
necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention.
[0010] FIG. 1 is a block diagram of a wireless communication system
suitable for performing multicast message transmission as defined
herein;
[0011] FIG. 2 shows a base station processor in communication with
a plurality of subscriber access units;
[0012] FIG. 3 is a flowchart depicting multicast message
transmission as defined herein; and
[0013] FIG. 4 shows the sequence of messages for establishing and
transmitting to a multicast group.
DETAILED DESCRIPTION OF THE INVENTION
[0014] A description of a preferred embodiment of the invention
follows. FIG. 1 is a block diagram of a communication system 10
operable for multicast message transmission in a wireless network
as defined herein. The communication system includes local
computing devices, generally user PCs 12, subscriber access units
14, a base station processor 16, and an internetworking gateway 18.
The user PCs 12 are in communication with the subscriber access
units 14 via a wired connection 20. The subscriber access units 14
are in communication with a base station processor 16 via a
wireless connection 26. The base station processor is in
communication with an internetworking gateway 18 via a wired
connection 24. The internetworking gateway 18 is adapted for
communication via a public access network 28 such as the
Internet.
[0015] The user PCs 12 may therefore be provided access to the
internetworking gateway 18, which may be any remote entity located
on the Internet or other network, through a combination of the
wired 20, 24 and wireless connection 26 provided. The wired
connection 20,24 is typically supported by a protocol such as
TCP/IP or UDP/IP. The wireless connection is supported by a
wireless link protocol such as IS95 or another wireless link
protocol such as the protocol described in pending U.S. Patent
Application entitled "Dynamic Frame Sizing Settings for
Multichannel Transmission," published as PCT application No. WO
99/44341, Sep. 2, 1999.
[0016] Typically, the PC 12 provides a data packet, which may for
example be an Internet Protocol (IP) packet, to the subscriber
access unit 14 over the wired connection 20, which may for example
be an Ethernet type connection. The subscriber access unit 14
removes the framing of the data packet and transfers the data in
the data packet to the base station processor 16 over the wireless
connection 26 in accordance with the wireless link protocol. The
base station processor 16 extracts the wireless connection frames
and forwards them, in data packet form, over the wired connection
24 to the internetworking gateway 18.
[0017] Similarly, packets sent from the public access network are
sent to the base station processor 16 over the wired link 24,
transmitted to the corresponding subscriber access unit 14 over the
wireless link 26, and sent to the user PC 12 over the wired link
20. The subscriber access unit 14 and the base station processor 16
therefore denote endpoints of the wireless connection 26, providing
a wireless link from the user PC 12 to the public access network 28
such as the Internet.
[0018] FIG. 2 shows a base station processor in communication with
a plurality of subscriber access units and operable to perform
multicast message transmission as defined herein. Multicast
messages are typically transmitted according to a protocol such as
the Internet Group Management Protocol (IGMP), as defined in
Internet RFC 2236. The base station processor 16 is in
communication with a plurality of subscriber access units 14a-14f
over a wireless connection 26. The base station processor 16 has a
plurality of wireless channels 22a-22j (channels) operable to
perform wireless communication between the subscriber access units
14 and the base station processor 16. The wireless channels 22
generally are allocated by the base station processor 16 to the
subscriber access units 14 for sending and receiving wireless
messages. Typically, the base station processor rapidly allocates
and deallocates channels 22 to accommodate channel requests for
messages sent between the subscriber access units 14 and the base
station processor 16.
[0019] Typical wireless systems employ a shared paging and access
method, common to all subscriber access units 14, that is used to
provide communication with subscriber access units 14 when no
dedicated wireless traffic channels 22 are allocated to send and
receive messages. In such a system, a common paging channel 32 is
used to notify a subscriber access unit 14 that it is being
allocated a traffic channel 22. Also in such a system, a common
access channel 30 is used by a subscriber access unit 14 to request
a traffic channel 22 from the base station processor 16. Once
traffic channels 22 are allocated, and the subscriber access unit
14 has been notified, the waiting messages are then forwarded by
the subscriber access units 14 to the PC 12 or to the base station
processor 16, depending on message direction.
[0020] In the example shown, described further below, channel 22c
is allocated to subscriber access unit 14d on connection ID C14.
Channel 22a is allocated to subscriber access unit 14b on
connection ID C5. There are no channels allocated to subscriber
access unit 14e on connection ID C11. Channel 22f is allocated to
the multicast group indicated as subscriber ID 15 on connection ID
C23. Connection ID C23 refers to a multicast group containing
member connection IDs C14 and C11 which correspond to subscriber
access units 14d and 14e respectively. The multicast message is
sent via channel 22f, providing both wireless connections 26a and
26b, and is received concurrently by subscriber access units 14d
and 14e, respectively. In this manner, multiple redundant message
transmissions, each entailing a separate channel allocation, are
avoided.
[0021] Referring in more detail to FIG. 2, the base station
processor 16 has a routing table 34, a connection table 36, and a
multicast group table 38. The routing table associates a network
address 40, indicative of a user PC 12 (FIG. 1) with a connection
ID 42. The connection table 36 associates connections with
channels. For each connection ID 42, a corresponding channel ID 46
is stored. The subscriber ID 44 for which a channel 22 is allocated
is also stored. For connection IDs 42 corresponding to multicast
groups, a separate connection table 36 entry is maintained for each
multicast group. Note that since the channels 22 are allocated on a
demand basis as messages are received, the connection table 36
entries corresponding to a connection ID may be added and deleted
as messages arrive and are sent on, as will be discussed further
below. The group management table 38 associates a multicast group
address 40 with a connection ID 42 and a list of group member
connection IDs 48. Each connection ID 42 from the connection table
36 that is included in the membership of the multicast group
indicated by multicast group address 40 is listed in the group
member connection IDs 48. Note that since groups and group
membership are dynamic, the group management table 38 entries may
be added, deleted and updated as groups are formed and members join
and leave the group as will be discussed further below.
[0022] Prior to discussing message transmission as indicated in
FIG. 2, a brief discussion of channel allocation and message
transmission using the base station processor 16 and the wireless
protocol would be beneficial. As indicated above, the base station
processor 16 allocates channels 22 among different subscriber
access units 14 to accommodate message transmission requests. Each
of the subscriber access units 14, therefore, is operable to
receive a message over any of the channels 22 as determined by the
base station processor 16. Since the wireless protocol used to
transmit the message signals uses a non-selective RF medium, all
the subscriber access units 14 are actually capable of processing
the message signals, unlike a switched network in which only the
intended recipient actually receives the message signals. Further,
multiple channels 22 may be allocated to the same subscriber access
unit 14. The connection table 36, therefore, stores the connection
ID 42 and corresponding entry to indicate which subscriber access
units 14 should process, or listen, to a particular channel 22.
Note that the connection ID 42 may also be used to associate other
connection parameters (not shown) used in conjunction with the
wireless link protocol.
[0023] Typically, all subscriber access units 14 are responsive to
the paging channel 32, as indicated above. When the base station
processor 16 allocates a channel 22 to a subscriber access unit 14,
a paging message is sent via the paging channel 32 to indicate to
the subscriber access unit 14 that a message is about to be
transmitted on a particular channel 22. For a unicast message, only
a single subscriber access unit 14 is involved. Therefore, while
all subscriber access units 14 will receive, demodulate and decode
the paging message on the paging channel 32, only the subscriber
access unit 14 indicated in the paging message need act on it. When
the message indicated in the paging message is sent, only the
subscriber access unit 14 indicated by the paging message will
demodulate and decode the message. The other subscriber access
units 14, while capable of receiving the RF signals carrying the
message, will not decode and may need not fully demodulate the
message because the paging message did not designate them.
[0024] During a multicast message transmission, multiple subscriber
access units 14 process the message. Therefore, the corresponding
paging message is indicative of the collection of the subscriber
access units 14 in the multicast group to whom the message is
directed. The group members may be indicated specifically by
individual subscriber access unit reference, or by a group
designator known to each of the subscriber access units 14 in the
group. In this manner, the same channel 22 is used to transmit to
multiple subscriber access units 14 because multiple subscriber
access units 14 are told to receive, or listen, on the same channel
22.
[0025] Continuing to refer to FIG. 2, a multicast group address 40
corresponding to IP address 224.27.4.6 is listed in the routing
table 34. The actual addresses used are exemplary and any suitable
address supported by the underlying protocol, here TCP/IP, can be
used. Consistent with the IGMP protocol indicated above, 224 is
typically the first part of the network number for a multicast
group. IP address 224.27.4.6 is associated with the connection ID
C23 in column 42. The multicast group IP address 224.27.4.6 in
column 40 and connection ID C23 in column 42 are associated in the
group management table 38 with connection IDs C14 and C11 in the
group connection list 48. The connection IDs C14 and C11 correspond
to subscriber access units 14d and 14e respectively. In the
example, connection ID 23 in column 42 is associated with
subscriber access unit 15 in column 44. Subscriber access unit 15
is used as a designation of a multicast group user. This
designation is exemplary and other suitable designations can be
employed. As depicted in the connection table 36, connection ID C23
is allocated channel 22f. In the group management table 38,
connection ID C23 is associated with group members having
connection IDs C14 and C11. These two multicast connections are
illustrated as wireless connections 26a and 26b, respectively.
[0026] Therefore, a multicast message sent to multicast group
224.27.4.6 results in the message being sent via channel 22f to
both subscriber access unit 14d and 14e, because both subscriber
access unit 14d and 14e are receiving, or listening, on channel
22f. Group establishment and the transmission of a multicast
message will be described in more detail below.
[0027] FIG. 3 shows a flowchart depicting the sequence of multicast
message transmission processing. Referring to FIGS. 3 and 2, a
message is received at the base station processor 16, as shown in
step 100. A check is made to determine if the message is a
multicast message, as depicted in step 102. If the message is not a
multicast message, unicast transmission continues, as disclosed at
step 104. If the message is a multicast message, a check is made to
determine whether the message contains control information or data
traffic, as depicted in step 106. Control information is indicative
of new multicast groups and additions and deletions of group
members. If the message contains control information, multicast
group join/delete processing is performed, as shown at step 108.
Otherwise, a lookup is performed in the routing table 34 to find
the group address, as disclosed at step 110. The connection ID
corresponding to the multicast group is retrieved, as shown at step
112. The connection ID corresponds to a group entry in the group
management table 38. A channel 22 is scheduled to be used to
transmit the message, as shown at step 114. For each connection ID
corresponding to the group connection list in the group entry of
the group management table 38, a lookup is performed to find an
entry in the connection table 36, as disclosed at step 116. For
each connection, the subscriber access unit corresponding to the
connection is retrieved, as depicted at step 118. The channel 22 to
be allocated to transmit the message is stored in the connection
table 36, as indicated at step 120. The channel 22 and subscriber
access unit 14 are then added to the paging message corresponding
to the multicast message, as shown at step 122. A check is made to
determine if all connection IDs corresponding to this multicast
group have been processed, as shown at step 124. If there are more
connection IDs corresponding to the group connection list 48 in the
group entry in the group management table 38, control reverts to
step 116 to process the additional connection IDs, as depicted at
step 126. When all subscriber access units 14 corresponding to the
multicast group have been implicated in the paging message, the
paging message is sent, as disclosed at step 128. Following the
paging message, the multicast message is sent over the channel 22
scheduled in step 114, as depicted at step 130. The message is
received by each of the subscriber access units indicated in the
paging message, as shown at step 132. In this manner, a single
channel allocation and a single message transmission provide a
message which is received by each of the subscriber access units 14
in the wireless multicast group.
[0028] FIG. 4 shows the sequence of messages used to establish and
send multicast group messages in more detail. As indicated above,
in one embodiment, multicast groups are defined by the IGMP
protocol. IGMP messages are indicative of requests to add and
delete groups and to add and delete group members, defined by an IP
address, to and from a multicast group. Referring to FIG. 4, the
base station processor 16 scans incoming messages for IGMP
messages, and updates the routing table 34, the connection table
36, and the group management table 38 accordingly. Incoming
messages from the Internet or other public access network are
received by the base station processor 16 via the internetworking
gateway 18. An add group message 200 is received by the base
station processor 16 for the multicast group identified by IP
address 224.27.4.6. An entry 202 is written to the routing table to
identify the new multicast group address, and connection C23 is
created and entry 204 is written to the connection table 36. Since
this is a new group, an entry 206 is written to the group
management table 38. As a multicast group may have zero or more
members at any time, no members are yet established for this
multicast group and the group connection list 48 stored in the
group management table entry 206 is empty.
[0029] An add member to group message 208 is received, indicative
of a request to add user PC 12d, served by subscriber access unit
14e, to the multicast group 224.27.4.6. More specifically, the add
member request message is indicative of an IP address served by
subscriber access unit 14e, since a single subscriber access unit
14 may serve many user PCs 12. The routing table 34 is scanned, and
the entry 202 for multicast group 224.27.4.6 is found to exist. The
routing table 34 indicates that connection ID C23 serves the
multicast group 224.27.4.6. The group management table 38 is
scanned, and the entry 206 for connection ID C23 is found to exist.
User PC 12d has an associated IP address of 218.114.3.7. The
routing table 34 is scanned for IP address 218.114.3.7, and the
entry is found to exist associated with connection ID C11. The
group management table 38 entry 206 is then updated to include
connection ID C11 in the group connection list 48.
[0030] Another add member to group message 210 is received,
indicative of a request to add user PC12c, served by subscriber
access unit 14d to the multicast group 224.27.4.6. The routing
table 34 again indicates that connection ID C23 is associated with
this multicast group. The group management table 38 is scanned, and
the entry 206 for connection ID C23 is found to exist. User PC 12c
has an associated IP address of 205.152.52.3. The routing table 34
is scanned for IP address 205.152.52.3, and the entry is found to
exist associated with connection ID C14. The group management table
38 entry 206 is then updated to include connection ID C14 in its
connection list.
[0031] As indicated above in FIG. 3, the wireless channels 22 are
allocated on demand as needed for messages. Accordingly, connection
entries in the connection table 36 need not indicate that any
traffic channels are allocated for a particular connection,
including the multicast group connection. A message 212 is received
at the base station processor 16 for the multicast group
224.27.4.6. A lookup in the routing table 34 indicates entry 202,
referencing the connection ID C23. Mapping the connection ID C23
into the group management table 38 yields two connections
corresponding to members of the multicast group as indicated by
entry 206. Multiple connections identified in the connection list
of the group management table 38 entry are indicative of a
multicast group. Connections C14 and C11 denote subscriber access
units 14d and 14e, respectively, as members of the multicast group.
A channel request to deliver the multicast message allocates
channel 22f for this multicast message. Accordingly, connection
table 36 entry 204 is updated with the allocated channel ID 22f. A
paging message 218 is created to alert subscriber access units 14d
and 14e to receive on channel 22f, and sent on the paging channel
32 to subscriber access units 14d and 14e, respectively. After
receipt of the paging message by the subscriber access units 14d
and 14e, the multicast message 220 is sent on the allocated channel
22f. Subscriber access units 14d and 14e will send the received
multicast message over the wired connection 20 to user PCs 12c and
12d, respectively, as indicated by messages 222 and 224. In a
typical messaging session, the subscriber access units 14 in a
multicast group may each receive many multicast messages in
sequence. These messages may be segmented to correspond to portions
of packets or the entire packet as received from the
internetworking gateway 18. It is possible that not all the
subscriber access units 14 in a multicast group will correctly
receive the message on the wireless channels, due, for example, to
interference or other transmission aspects common to the medium
which supports the wireless connection. In another embodiment, each
message is associated with a sequence number. Referring again to
FIG. 4, in this embodiment, each subscriber access unit 14 which
does not receive the multicast message correctly sends a negative
acknowledgment back to the base station processor 16. If one or
more negative acknowledgments are received at the base station
processor 16, the base station processor 16 will resend the message
in a manner similar to the original wireless multicast
transmission, on either the same channel or a newly allocated
channel. Subscriber access units 14 which did correctly receive the
message will recognize the sequence number as having been received
already, and will ignore the message, so that duplicate messages
are avoided.
[0032] It should be noted that exemplary IGMP messages are
described herein, and that other messages and protocols exist which
are indicative of requests to create and delete multicast groups,
and to join and remove members from the multicast groups. Such
messages include, but are not limited to, group query, group member
list, join host group, leave host group, and others. The system and
methods described herein are illustrative of the notion that a
wired line multicast group protocol, such as IGMP used in a TCP/IP
network, can be employed in a base station processor to provide
efficient multicast group transmission in a wireless network.
Through examining the group management messages in the base station
processor as defined herein, wireless channels, wireless
connections, and wireless interfaces can be employed in an optimal
manner.
[0033] Those skilled in the art should readily appreciate that the
programs defining the operations and methods defined herein are
deliverable to a base station processor in many forms, including
but not limited to a) information permanently stored on
non-writeable storage media such as ROM devices, b) information
alterable stored on writeable storage media such as floppy disks,
magnetic tapes, CDs, RAM devices, and other magnetic and optical
media, or c) information conveyed to a computer through
communication media, for example using baseband signaling or
broadband signaling techniques, as in an electronic network such as
the Internet or telephone modem lines. The operations and methods
may be implemented in a software executable out of a memory by a
processor or as a set of instructions embedded in a carrier wave.
Alternatively, the operations and methods may be embodied in whole
or in part using hardware components, such as Application Specific
Integrated Circuits (ASICs), state machines, controllers or other
hardware components or devices, or a combination of hardware and
software components.
[0034] While the system and method for transmitting multicast
messages in a wireless communication network have been particularly
shown and described with references to embodiments thereof, it will
be understood by those skilled in the art that various changes in
form and details may be made therein without departing from the
scope of the invention encompassed by the appended claims.
Accordingly, the present invention is not intended to be limited
except by the following claims.
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