Delivery of multicast and uni-cast services in an OFDMA system

1. A method of operating a radio telecommunications network including, a plurality of base transceiver stations (BTSs) each transmitting on a respective transmission bandwidth, and one or more user equipments (UEs) each having a respective maximum reception bandwidth,

defining a common multicast frequency band within the respective transmission bandwidth of at least a first group of BTSs of the radio telecommunications network on which a multicast service is to be transmitted;

transmitting a multicast service in the common multicast frequency band from each BTS within the first group of BTSs; and

enabling each base station having a bandwidth greater than the width of the common multicast frequency band to transmit a uni-cast service in portion of its transmission bandwidth falling outside the multicast frequency band.

2. The method of operating a radio telecommunications network as claimed in claim 1 , wherein a frequency of the common multicast frequency band is predefined.

3. The method of operating a radio telecommunications network as claimed in claim 1 , wherein a common multicast frequency band has a bandwidth equal to the lowest maximum reception bandwidth amongst the UEs.

4. The method of operating a radio telecommunications network as claimed in claim 1 , wherein the first group of BTSs includes all BTSs in the radio telecommunications network.

5. A radio telecommunications network including a plurality of base transceiver stations (BTSs) each transmitting on a respective transmission bandwidth, and one or more user equipments (UEs) each having a respective maximum reception bandwidth, said network being configured to implement a method as claimed in any one of claims 1 to 4 .

6. A method of transmitting a multicast service on a base transceiver station (BTS) having a first transmission bandwidth, to one or more user equipment (UEs) each having a respective maximum reception bandwidth, the method including:

transmitting a multicast service in a predefined multicast frequency band; and

transmitting a uni-cast service in one or more frequency bands falling outside the multicast frequency band, in the event that the first transmission bandwidth is larger than the bandwidth of the multicast frequency band.

7. The method of transmitting a multicast service on a base transceiver station as claimed in claim 6 , wherein the method further includes:

adding a long cyclic prefix to a time domain signal including multicast data.

8. The method of transmitting a multicast service on a base transceiver station as claimed in claim 6 , wherein the method further includes:

combining signals representing said uni-cast service and said multicast service to generate a transmitted signal where such that the orthogonality of a plurality of subcarriers forming the signals representing said uni-cast service and said multicast service is maintained in the transmitted signal.

9. The method of transmitting a multicast service on a base transceiver station as claimed in claim 6 , wherein the method further includes:

multiplexing data representing said uni-cast service and data representing said multicast service in the frequency domain; and

converting a multiplexed frequency domain signal into a time domain signal.

10. The method of transmitting a multicast service on a base transceiver station as claimed in claim 9 , wherein the step of, converting the multiplexed frequency domain signal, includes:

performing an inverse fast Fourier transform (IFFT) having a size dependent on the first transmission bandwidth.

11. The method of transmitting a multicast service on a base transceiver station as claimed in claim 9 which further includes:

adding a long cyclic prefix to the time domain signal generated from a signal obtained by multiplexing data representing said uni-cast service and data representing said multicast service in the frequency domain.

12. The method of transmitting a multicast service on a base transceiver station as claimed in claim 11 which further includes:

adding a short cyclic prefix to the time domain signal generated from a signal obtained by multiplexing data representing said uni-cast service and data representing said multicast service in the frequency domain, in the event that no multicast service is to be transmitted in a particular time transmission interval.

13. The method of transmitting a multicast service on a base transceiver station as claimed in claim 6 , wherein the method further includes:

converting data representing said uni-cast service to a time domain signal; and

converting data representing said multicast service to a time domain signal separately to said data representing said uni-cast service.

14. The method of transmitting a multicast service on a base transceiver station as claimed in claim 13 , wherein the step of, converting the data representing said uni-cast service to a time domain signal, includes:

performing an inverse fast Fourier transform (IFFT) having a size dependent on the first transmission bandwidth.

15. The method of transmitting a multicast service on a base transceiver station as claimed in claim 13 , wherein the step of converting the data representing said multicast service to a time domain signal, includes:

performing an inverse fast Fourier transform (IFFT) having a size dependent on the first transmission bandwidth.

16. The method of transmitting a multicast service on a base transceiver station as claimed in claim 13 which further includes:

adding a first cyclic prefix having a first length to the time domain signal carrying the uni-cast service;

adding a second cyclic prefix having a second length to the time domain signal carrying the multicast service, wherein the second length is longer than said first length; and

adding said time domain signals prior to transmission to said UE.

17. A method of transmitting a multicast service on a base transceiver station as claimed in claim 6 which further includes signaling signalling to one or more UEs whether a multicast service is to be transmitted in a particular time transmission interval.

18. A base transceiver station configured to transmit a multicast service using a method as claimed in any one of claims 6 to 17 .