Radio communication system
In a radio communication system having a data channel for the transmission of data packets from a primary station to a secondary station, a plurality of downlink control channels are used to signal information relating to packet transmission. A problem with this scheme is that with a fixed control channel allocation system throughput (T) for a given offered load (O) can be significantly reduced in a worst case scenario (for example two secondary stations using the same control channel). One solution uses an indicator signal to inform a secondary station of the control channel it should receive, but this adds significant complexity to the system. The present invention provides a simpler scheme having similar benefits by shuffling the allocation of control channels to secondary stations, according to a defined sequence for each secondary station, thereby avoiding the worst case scenario.
1. A radio communication system having a data channel for the transmission of data packets from a primary station to a secondary station and a plurality of control channels for signaling of control information relating to the data packets from the primary station to the secondary station, wherein the primary station comprises means for allocating one of the control channels to the secondary station and means for changing the allocated control channel according to a defined sequence, and the secondary station comprises means for monitoring the currently allocated control channel to determine information about packet transmissions, and wherein the primary station comprises means for allocating control channels for a plurality of secondary stations according to a plurality of respective defined sequences, all of which are different.
2. The system as claimed in claim 1 , wherein means are provided for repeating the defined sequence.
3. The system as claimed in claim 1 , wherein the radio channels are divided into time frames and wherein means are provided for repeating the defined sequence once per frame.
4. The system as claimed in claim 1 , wherein a timing reference for repetition of the defined sequence is provided by a common downlink channel.
5. A primary station for use in a radio communication system having a data channel for the transmission of data packets from the primary station to a secondary station and a plurality of control channels for signaling of control information relating to the data packets from the primary station to the secondary station, wherein means are provided for allocating one of the control channels to the secondary station and for changing the allocated control channel according to a defined sequence,
wherein means are provided for allocating control channels for a plurality of secondary stations according to a plurality of respective defined sequences, all of which are different.
6. The primary station as claimed in claim 5 , wherein means are provided for scheduling data packets for a plurality of secondary stations by giving priority to the largest data packets.
7. The primary station as claimed in claim 5 , wherein not all of the defined sequences include more than one control channel.
8. The primary station as claimed in claim 5 , wherein means are provided for transmitting at least one of the control channels for only a proportion of the time that data packets are transmitted.
9. A secondary station for use in a radio communication system having a data channel for the transmission of data packets from a primary station to the secondary station and a plurality of control channels for signaling of control information relating to the data packets from the primary station to the secondary station, wherein means are provided for determining which of the control channels is allocated to the secondary station wherein the control channels are allocated for a plurality of secondary stations according to a plurality of respective defined sequences, all of which are different, the allocated control channel being changed according to a respective defined sequence, and for monitoring the currently allocated control channel to determine information about packet transmissions.
10. The secondary station as claimed in claim 9 , wherein means are provided for transmitting a negative acknowledgement to the primary station to indicate that the allocated control channel is successfully detected but cannot be correctly received.
11. The secondary station as claimed in claim 10 , wherein the negative acknowledgement is a different signal from that used to indicate that a data packet could not be correctly received.
12. A method of operating a radio communication system having a data channel for the transmission of data packets from a primary station to a secondary station and a plurality of control channels for signaling of control information relating to the data packets from the primary station to the secondary station, the method comprising the primary station allocating one of the control channels to the secondary station and changing the allocated control channel according to a defined sequence, and the secondary station monitoring the currently allocated control channel to determine information about packet transmissions,
wherein the primary station allocates control channels for a plurality of secondary stations according to a plurality of respective defined sequences, all of which are different.