Sub-channel and power allocation method and apparatus for multicast transmission using an orthogonal frequency division multiple access scheme

1. A method of wirelessly multicasting data, said method comprising:

allocating one of a plurality of sub-channels to one of a plurality of multicast group clients for a wirelessly communicated multicast session; and

performing bit-loading for said allocated sub-channel, wherein said performing act further comprises:

finding one of said plurality of multicast group clients having a lowest received bit rate;

finding one of said plurality of sub-channels having a lowest power needed to transmit one more bit to said one of said plurality of multicast group clients having said lowest received bit rate;

comparing said lowest power needed to a residual power;

adding one more transmission bit to said sub-channel if said lowest power needed is not greater than said residual power to increase a multicast rate; and

updating a multicast rate, said residual power and said lowest power needed to transmit one more bit if said lowest power needed is not greater than said residual power;

wherein said allocating act further comprises:

finding one of said plurality of said multicast group clients having a lowest received bit rate;

determining if more than one of said plurality of multicast group clients has said lowest received bit rate;

if more than one of said plurality of multicast group clients has said lowest received bit rate, finding a sub-channel and multicast group client pair having a highest received bit rate, said sub-channel being located from among unassigned sub-channels and the multicast group client of said pair being one of said plurality of multicast group clients having said lowest bit rate, and assigning said located sub-channel to said multicast group client;

finding one of said plurality of sub-channels that can achieve a highest multicast rate if said sub-channel is assigned to said multicast group client and assigning said sub-channel to said multicast group client;

assigning said sub-channel to any of the plurality multicast group clients having a higher received bit rate on said sub-channel than said multicast group client to which said sub-channel had been previously assigned;

updating an achievable multicast rate based on said sub-channel assignment;

recording said achievable multicast rate and said sub-channel assignment as a sub-channel realization;

determining if all sub-channels have been allocated to all multicast group clients for said multicast session; and

selecting one of a plurality of recorded sub-channel realizations if all sub-channels have been allocated to all multicast group clients for said multicast session.

2. The method according to claim 1 , further comprising initializing said sub-channel and multicast group client pairs.

3. The method according to claim 1 , further comprising given a sub-channel allocation, initially determining said residual power and said lowest power needed to transmit one more bit on each of said plurality of sub-channels.

4. An apparatus comprising:

means for allocating one of a plurality of sub-channels to one of a plurality of a multicast group clients for a multicast session; and

means for performing bit-loading for said allocated sub-channel, wherein said performing act further comprises:

means for finding one of said plurality of multicast group clients having a lowest received bit rate;

means for finding one of said plurality of sub-channels having a lowest power needed to transmit one more bit to said one of said plurality of multicast group clients having said lowest received bit rate;

means for comparing said lowest power needed to a residual power;

means for adding one more transmission bit to said sub-channel if said lowest power needed is not greater than said residual power to increase a multicast rate; and

means for updating a multicast rate, said residual power and said lowest power needed to transmit one more bit if said lowest power needed is not greater than said residual power;

wherein said allocating act further comprises:

means for finding one of said plurality of said multicast group clients having a lowest received bit rate;

means for determining if more than one of said plurality of multicast group clients has said lowest received bit rate;

means for finding a sub-channel and multicast group client pair having a highest received bit rate, said sub-channel being located from among unassigned sub-channels and the multicast group client of said pair being one of said plurality of multicast group clients having said lowest bit rate, and assigning said sub-channel to said multicast group client if more than one of said plurality of multicast group clients has said lowest received bit rate;

means for finding one of said plurality of sub-channels that can achieve a highest multicast rate if said sub-channel is assigned to said multicast group client and assigning said sub-channel to said multicast group client if more than one of said plurality of multicast group clients has said lowest received bit rate;

means for assigning said sub-channel to any of the multicast group clients having a higher received bit rate on said sub-channel than said multicast group client to which said sub-channel had been previously assigned;

means for updating an achievable multicast rate based on said sub-channel assignment,

means for recording said achievable multicast rate and said sub-channel assignment as a sub-channel realization;

means for determining if all sub-channels have been allocated to all multicast group clients for said multicast session; and

means for selecting one of a plurality of recorded sub-channel realizations if all sub-channels have been allocated to all multicast group clients for said multicast session.

5. The apparatus according to claim 4 , further comprising means for initializing said sub-channel and multicast group client pairs.

6. The apparatus according to claim 4 , further comprising given a sub-channel allocation, means for initially determining said residual power and said lowest power needed to transmit one more bit on each of said plurality of sub-channels.