FIG. 2b illustrates an example non-contention based random access procedure for requesting resources in an LTE network. At step 251, prior to the transmission of a random access preamble from the user device in the access request message, the base station allocates a preamble from a non-contention based set of preambles to the user device. This allocation may be performed via a format 1A downlink control information (DCI) message on the PDCCH or in a handover command if the user device has recently entered a cell served by the base station. At step 252 the user device transmits its allocated preamble to the base station. Once the preamble has been received at the base station, the base station transmits a response message, such as for example a random access response, at step 253 where the response message contains similar information to the response message sent at step 202 of FIG. 2a. Once the response message has been received at the user device, the user device then transmits its intended message in the allocated uplink resources indicated in the response message.

Although the access request procedures of FIGS. 2a and 2b has been described with reference to sending a receiving messages directly from a base station, the messages may also be sent and received via one or more relays using the same procedure. For example, the messages may be sent and received via the communications paths illustrated in FIG. 1, where in the uplink a receiving relay either relays a message to another relay or a base station, and in the downlink relays the message to another relay or a user device.

Response Windowing