Patent ID: 8774113

Claim:
A method in a mobile communication device for accessing a wireless communication system, the method comprising detecting random-access information transmitted by a base station node, transmitting a random-access preamble to the base station node according to the random-access information, and receiving a random-access response from the base station node, the random-access response including an allocation of uplink resources, wherein an improvement comprises: selecting by the mobile communication device, a reference signal sequence index from a pre-determined set of reference signal sequence indexes; transmitting a first message to the base station node using the uplink resource allocation provided in the random-access response, the first message comprising a device identifier for the mobile communication device and a first demodulation reference signal derived from a base reference sequence shifted according to the selected sequence index; detecting feedback from the base station node indicating that the first message was not successfully received; and re-transmitting the first message to the base station node, the re-transmitted first message comprising a second demodulation reference signal shifted according to the selected sequence index.