Relay device and method

1. A relay device for wirelessly relaying data from a terminal device to a base station, the relay device comprising:

a receiver; and

a transmitter, responsive to an access request message of a second type being received at the receiver from the terminal device to transmit a relayed access request message to the base station to request the base station to allocate uplink resources to the terminal device; wherein

the access request message of the second type is transmitted by the terminal device if no response to a transmitted access request message of a first type is received from the base station;

the access request messages of the first type include Random Access Channel preambles selected from a first group of Random Access Channel preambles;

the access request messages of the second type include Random Access Channel preambles selected from a second group of Random Access Channel preambles, which are different from the first group of Random Access Channel preambles; and

the base station is responsive to either an access request message of the first type received from the terminal device or the relayed access request message from the relay device to transmit an allocation of uplink resources to the terminal device.

2. A relay device according to claim 1 , wherein

the terminal device is operable to transmit uplink data to the relay device on the allocated uplink resources; and

the relay device is operable to relay to the base station the up data received from the terminal device.

3. A relay device according to claim 1 , wherein

the relay device is operable to determine an identifier for the terminal device from which the access request message of the second type was received and include the identifier in the relayed access request message transmitted to the base station; and

the base station uses the identifier to transmit an allocation of uplink resources to the terminal device.

4. A relay device according to claim 3 , wherein

the access request messages are transmitted on a random access channel; and

the relay device is operable to determine an identifier for the terminal device from the time and/or frequency resource within the random access channel used to transmit the access request message of the second type.

5. A relay device according to claim 1 , wherein

the relay device is operable

to measure a received signal power of the access request message of the second type received from the terminal device; and

to set power control information in the relayed access request message for controlling a power level of a subsequent transmission from the terminal device to the relay device on the allocated uplink resources.

6. A relay device according to claim 5 , wherein the power control information specifies a power offset from the received signal power of the access request message of the second type.

7. A relay device according to claim 5 , wherein the allocation of uplink resources transmitted from the base station to the terminal device comprises the power control information for controlling the transmission power of the subsequent transmission from the terminal device to the relay device.

8. A relay device according to claim 1 , wherein

the relay device is operable

to measure a propagation time delay between the terminal device and the relay device of the access request message of the second type;

to determine, based on the propagation time delay, a required timing advance offset for a subsequent transmission from the terminal device to the relay device so that a receive time of the subsequent transmissions at the relay device is synchronised with a receive time of transmissions from other terminal devices; and

to specify said timing advance offset in the relayed access request message.

9. A relay device according to claim 8 , wherein the allocation of uplink resources transmitted from the base station to the terminal device comprises the timing advance offset for controlling the timing of a subsequent transmission from the terminal device to the relay device.

10. A relay device according to claim 1 , wherein the relayed access request message comprises an identification of the terminal device which transmitted the message.

11. A relay device according to claim 1 , wherein

the relay device is responsive to an access request message of the second type received from the terminal device to request the base station to allocate uplink resources to the relay device to transmit the relayed access request message;

the base station is responsive to the request from the base station to allocate uplink resources to the relay device; and

the relay device is operable to transmit the relayed access request message to the base station using the uplink resources allocated to the relay device by the base station.

12. A relay device according to claim 2 , wherein

the allocation of uplink resources transmitted from the base station to the terminal device is a Random Access Response; and

the uplink data transmitted by the terminal device on the allocated uplink resources is a Message 3 .

13. A relay device according to claim 2 , wherein the uplink data comprises one or both of control information and data.

14. A relay device according to claim 2 , wherein

the relay device is operable

to measure a received signal power of the uplink data received from the terminal device; and

to set power control information in the relayed uplink data for controlling a power level of a subsequent transmission from the terminal device to the relay device.

15. A relay device according to claim 2 , wherein

the relay device is operable

to measure a propagation time delay between the terminal device and the relay device of the uplink data;

to determine, based on the propagation time delay, a required timing advance offset for a subsequent transmission from the terminal device to the relay device so that a receive time of the subsequent transmission at the relay device is synchronised with a receive time of transmissions from other terminal devices; and

to specify said timing advance offset in the relayed uplink data.

16. A relay device according to claim 2 , wherein the relayed uplink data comprises an identification of the terminal device which transmitted the uplink data.

17. A relay device according to claim 1 , wherein

the relay device is responsive to the uplink data received from the terminal device to request the base station to allocate uplink resources to the relay device to transmit the relayed uplink data;

the base station is responsive to the request from the base station to allocate uplink resources to the relay device; and

the relay device is operable to transmit the relayed uplink data to the base station using the uplink resources allocated to the relay device by the base station.

18. A terminal device for wirelessly communicating data to a base station via a relay device, the terminal device comprising:

a transmitter operable

to transmit one or more access request messages of a first type to request uplink resources from the base station, and

if no response to the transmitted access request messages of the first type is received from the base station, to transmit an access request message of a second type; and

a receiver operable to receive from the base station an allocation of uplink resources allocated at the base station in response to one of an access request message of the first type or a relayed access request message transmitted to the base station by the relay device in response to an access request message of the second type being received from the terminal device, the relayed access request message requesting the base station to allocate uplink resources to the terminal device, wherein

the access request messages of the first type include Random Access Channel preambles selected from a first group of Random Access Channel preambles, and

the access request messages of the second type include Random Access Channel preambles selected from a second group of Random Access Channel preambles, which are different from the first group of Random Access Channel preambles.

19. A terminal device according to claim 18 , wherein

the terminal device is operable to transmit uplink data to the relay device on the allocated uplink resources; and

the relay device is operable to relay to the base station the uplink data received from the terminal device.

20. A terminal device according to claim 18 , wherein the terminal device is operable

to repeatedly transmit access request messages of the first type at successively higher power levels until a response is received from the base station or until a maximum power level is reached; and

if no response to the access request message of the first type at the maximum power level is received from the base station, to transmit the access request message of the second type.

21. A terminal device according to claim 20 , wherein the access request message of the second type is transmitted at the maximum power level.

22. A terminal device according to claim 20 , wherein the maximum power level for transmitting the access request messages of the first type is less than the maximum transmission power of the terminal device.

23. A terminal device according to claim 19 , wherein

the allocation of uplink resources transmitted from the base station to the terminal device is a Random Access Response; and

the uplink data transmitted by the terminal device on the allocated uplink resources is a Message 3 .

24. A terminal device according to claim 19 , wherein the uplink data comprises one or both of control information and data.

25. A terminal device according to claim 19 , wherein

the received allocation of uplink resources transmitted from the base station to the terminal device comprises power control. information determined from a received signal power of the access request message of the second type received at the relay device; and

the terminal device transmits the uplink data at a power level specified by the power control information.

26. A terminal device according to claim 25 , wherein the power control information specifies a power offset from the received signal power of the access request message of the second type received at the relay device.

27. A terminal device according to claim 19 , wherein

the received allocation of uplink resources transmitted from the base station to the terminal device comprises a required timing advance offset for the terminal device to transmit to the relay device so that a receive time of the transmission at the relay device is synchronised with a receive time of transmissions from other terminal devices, the timing advance offset being determined at the relay device from a propagation time delay between the terminal device and the relay device of the access request message of the second type.

28. A method of wirelessly relaying data from a terminal device to a base station, comprising:

responsive to an access request message of a second type being received from the terminal device, transmitting a relayed access request message to the base station to request the base station to allocate uplink resources to the terminal device; wherein

the access request message of the second type is transmitted by the terminal device if no response to a transmitted access request message of a first type is received from the base station; the access request message of the first type includes Random Access Channel preambles selected from a first group of Random Access Channel preambles;

the access request message of the second type includes Random Access Channel preambles selected from a second group of Random Access Channel preambles, which are different from the first group of Random Access Channel preambles; and

the base station is responsive to either an access request message of the first type received from the terminal device or the relayed access request message from the relay device to transmit an allocation of uplink resources to the terminal device.

29. A method of wirelessly communicating data to a base station via a relay device, comprising:

transmitting one or more access request messages of a first type to request uplink resources from the base station, and

if no response to the transmitted access request messages of the first type is received from the base station, transmitting an access request message of a second type; and

receiving from the base station an allocation of uplink resources allocated at the base station in response to one of an access request message of the first type or a relayed access request message transmitted to the base station by the relay device in response to an access request message of the second type being received from the terminal device, the relayed access request message requesting the base station to allocate uplink resources to the terminal device, wherein

the access request messages of the first type include Random Access Channel preambles selected from a first group of Random Access Channel preambles, and

the access request messages of the second type include Random Access Channel preambles selected from a second group of Random Access Channel preambles, which are different from the first group of Random Access Channel preambles.