Communication system and methods using multiple-in-multiple-out (MIMO) antennas within unitary braid divisional multiplexing (UBDM)

A method of performing unitary braid divisional multiplexing (UBDM) with a plurality of multiple-in-multiple-out (MIMO) antennas, the method comprising:

• generating, via at least one processor, a plurality of initial vectors, each initial vector from the plurality of initial vectors including N elements, N being a positive integer;
• applying, via the at least one processor, a code map to each initial vector from the plurality of initial vectors to produce an associated spreading code vector of a plurality of spreading code vectors, each spreading code vector from the plurality of spreading code vectors including M elements, M being a positive integer having a value of at least N, the code map defined such that an inner product of:
• (1) a first spreading code vector from the plurality of spreading code vectors, based on a first initial vector from the plurality of initial vectors;
• and (2) a second spreading code vector from the plurality of spreading code vectors, based on a second initial vector from the plurality of initial vectors, is equal to a product of (i) an inner product of the first initial vector and the second initial vector, and (ii) a positive constant;
• producing, using the first spreading code vector, a spread signal based on a complex baseband signal;
• storing the spread signal in a memory operably coupled to the processor;
• splitting the spread signal into a plurality of spread signals, each spread signal from the plurality of spread signals being uniquely associated with a MIMO antenna from the plurality of MIMO antennas;
• and
• transmitting the plurality of spread signals, via a communications channel and the plurality of MIMO antennas, to a signal receiver that is configured to detect the first complex baseband signal based on the first spreading code vector.

An apparatus comprising:

• a plurality of antennas;
• at least one processor configured to:
• generate a plurality of initial vectors, each initial vector from the plurality of initial vectors including N elements, N being a positive integer;
• apply a code map to each initial vector from the plurality of initial vectors to produce an associated spreading code vector including at least M elements, M being a positive integer having a value of at least N, the code map defined such that an inner product of:
• (1) a first spreading code vector from the plurality of spreading code vectors, based on a first initial vector from the plurality of initial vectors;
• and (2) a second spreading code vector from the plurality of spreading code vectors, based on a second initial vector from the plurality of initial vectors, is equal to a product of (i) an inner product of the first initial vector and the second initial vector, and (ii) a positive constant;
• produce a first spread signal based on a first complex baseband signal;
• and
• produce a second spread signal based on a second complex baseband signal;
• and
• a splitter coupled to the code generator and the plurality of antennas, the splitter configured to:
• split the first spread signal into a first plurality of spread signals, each spread signal from the first plurality of spread signals being uniquely associated with an antenna from the plurality of antennas;
• split the second spread signal into a second plurality of spread signals, each spread signal from the second plurality of spread signals being uniquely associated with an antenna from the plurality of antennas;
• the plurality of antennas configured to transmit the first spread signal to a first signal receiver, and to transmit the second spread signal to a second signal receiver different from the first signal receiver, such that each of the first signal receiver and the second signal receiver, upon receiving the first spread signal and the second spread signal detects the first complex baseband signal and the second complex baseband signal, respectively.