Methods and Apparatus for Multicast Transmission

1 . A method of controlling transmission of a set of transmissions from a source device to at least one destination device according to a multicast transmission scheme, the set of transmissions comprising a configurable number of random linear network coded packets that are to be multicast by the source device to the destination devices at a configurable transmission rate, the method comprising:

receiving, from said at least one destination device, data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device; and

selectively adapting one of transmission rate for a current set of transmissions and number of random linear network coded packets in the current set of transmissions on the basis of the received data.

2 . A method according to claim 1 , in which the transmission rate is adapted within an upper transmission rate and a lower transmission rate on the basis of said data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device.

3 . A method according to claim 2 , in which the transmission rate is increased up to a maximum value given by said upper transmission rate in the event that said data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device exceeds a predetermined threshold.

4 . A method according to claim 2 , in which the transmission rate is decreased down to a minimum value given by said lower transmission rate in the event that said data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device less than a predetermined threshold.

5 . A method according to claim 1 , in which the number of transmissions in the current set is selected on the basis of said data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device.

6 . A method according to claim 5 , in which the data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device is used to determine a first number, said first number corresponding to a number of previously transmitted random linear network coded packets that have yet to be decoded, and to determine a second number, said second number corresponding to a number of extra random linear network coded packets that are to be transmitted, in which said number of transmissions in the current set comprises the first number and the second number.

7 . A method according to claim 6 , in which the second number is selectively decreased in the event that:

a) said data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device exceeds a predetermined threshold; and

b) the rate of transmission for said previously transmitted packets is equal to a predetermined upper rate of transmission.

8 . A method according to claim 6 , in which the second number is selectively increased in the event that:

a) said data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device is less than a predetermined threshold; and

b) the rate of transmission for said previously transmitted packets is equal to a predetermined lower rate of transmission.

9 . A method according to claim 1 , further comprising broadcasting a request message to said at least one destination device after transmission of said previously transmitted set of transmissions, said request message requesting data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device.

10 . A method according to claim 1 , in which each transmission in a given set of packets comprises a header, the header being for use in triggering transmission by said at least one destination device of data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device, and comprising data indicative of a number of individual transmissions making up the given set.

11 . A method according to claim 1 , in which the current set of transmissions are multicast to said at least one destination device over a wireless network.

12 . A method according to claim 1 , in which the source transmits the set of transmissions to a plurality of destination devices, and the method comprises selectively adapting one of the transmission rate for a current set of transmissions and the number of random linear network coded packets in the current set of transmissions on the basis of the poorest level of progress in decoding the previously transmitted set of transmissions by all of the destination devices.

13 . Apparatus for controlling transmission of a set of transmissions from a source device to at least one destination device according to a multicast transmission scheme, the set of transmissions comprising a configurable number of random linear network coded packets that are to be multicast by the source device to the destination devices at a configurable transmission rate, the apparatus comprising a processing system, the processing system comprising at least one processor and a memory storing a set of computer instructions, in which the processing system is arranged to:

receive, from said at least one destination device, data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device; and

selectively adapt one of transmission rate for a current set of transmissions and number of random linear network coded packets in the current set of transmissions on the basis of the received data.

14 . Apparatus according to claim 13 , in which processing system is arranged to adapt the transmission rate within an upper transmission rate and a lower transmission rate on the basis of said data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device.

15 . Apparatus according to claim 14 , in which the processing system is arranged to increase the transmission rate up to a maximum value given by said upper transmission rate in the event that said data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device exceeds a predetermined threshold.

16 . Apparatus according to claim 14 , in which the processing system is arranged to decrease the transmission rate down to a minimum value given by said lower transmission rate in the event that said data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device is less than a predetermined threshold.

17 . Apparatus according to claim 13 , in which the data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device is used to determine a first number, said first number corresponding to a number of previously transmitted random linear network coded packets that have yet to be decoded, and to determine a second number, said second number corresponding to a number of extra random linear network coded packets that are to be transmitted, in which the processing system is arranged to configure said number of transmissions in the current set on the basis of the first number and the second number.

18 . Apparatus according to claim 17 , in which the processing system is arranged to decrease said second number in the event that:

a) said data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device exceeds a predetermined threshold; and

b) the rate of transmission for said previously transmitted packets is equal to a predetermined upper rate of transmission.

19 . Apparatus according to claim 17 , in which the processing system is arranged to increase said second number in the event that:

a) said data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device is less than a predetermined threshold; and

b) the rate of transmission for said previously transmitted packets is equal to a predetermined lower rate of transmission.

20 . A computer readable memory storing a computer program comprising:

code for receiving, from said at least one destination device, data indicative of progress in decoding a previously transmitted set of transmissions by said at least one destination device; and

code for selectively adapting one of transmission rate for a current set of transmissions and number of random linear network coded packets in the current set of transmissions on the basis of the received data.