Controlled superposition coding in multi-user communication systems

A base station for use in a communications system including a plurality of wireless terminals, a different communications channel existing between each wireless terminal in said plurality of wireless terminals and said base station, the communications channel existing between each particular wireless terminal and the base station having a quality which is the channel quality for the particular wireless terminal, the base station comprising:

• a set of channel condition information indicating the channel quality of each of said plurality of wireless terminals;
• means for examining the set of channel condition information to identify wireless terminals having channel conditions which differ from one another by a pre-selected minimum amount;
• and
• means for assigning a communications channel segment to be used to communicate superimposed signals corresponding to a least two different wireless terminals identified as having channel conditions which differ by at least said pre-selected minimum amount.

A wireless terminal including:

• a receiver for receiving a superimposed assignment signal including a first signal portion and a second signal portion one of said signal portions being intended for said wireless terminals with the other one of said signal portions being intended for another wireless terminal, the first signal portion being received with at a lower power level than said second signal portion;
• a superposition decoder for decoding said first and second signal portions;
• means for determining from information included in one of said first and second signal portions which portion is intended for said wireless terminal;
• and
• a transmitter for transmitting signals in uplink communications channel segments to which received superimposed assignment signals intended for said wireless terminal correspond.

A communications method for use in a communications system including a base station and a plurality of wireless terminals, a different communications channel existing between each wireless terminal in said plurality of wireless terminals and said base station, the communications channel existing between each particular wireless terminal and the base station having a quality which is the communications channel quality for the particular wireless terminal, signals transmitted from the wireless terminals to the base station combining during transmission between, the method comprising:

• operating the base station to:
• assign an uplink communications channel segment to be used simultaneously by a first and second device;
• receive a composite signal from said uplink communications channel segment, said composite signal including a first signal transmitted by said first device and a second signal transmitted by said second device;
• and
• perform a superposition decoding operation on the received composite signal to decode the first and second signals included in said composite signal.