Multi-channel spread spectrum system
View Patent ↗A multi-channel spread-spectrum system separates a data stream, for example from a convolutional encoder and an interleaver, into sub-channel data-sequence signals. For each sub-channel data-sequence signal, m bits are translated to one code of a unique set of orthogonal chip-sequence signals. The other k bits of the same sub-channel data-sequence signal are translated to a distinct phasor. Each phasor is used to modulate the respective chip-sequence signal. A complex-signal combiner combines the real and imaginary components of all the phase-modulated chip-sequence signals into in-phase (I) and quadrature (Q) spread-spectrum multi-channel signals, which are spread by a cell-site specific signature-sequence. The receiver decorrelates the received spread-spectrum signal, preferably with a bank of matched filter (MF) joint-detectors, to recover the bits from all the spread-spectrum sub-channel signals for remultiplexing into the transmitted data stream. The multi-channel spread-spectrum system supports constant data rate throughout the cell by maintaining a large processing gain, at the demultiplexed sub-channel data sequence level, thus a code-reuse-one type spread-spectrum system can be deployed with the aid of power control.
1. A multi-channel spread-spectrum modulator subsystem, comprising:
a demultiplexer for demultiplexing a representation of an input data stream into first and second sub-channel data-sequence signals;
a first mapping circuit coupled to receive the first sub-channel data-sequence signal, responsive to each segment of the first sub-channel data-sequence for selecting a spreading-code for the first sub-channel from among a plurality of spreading-codes based on a first set of bits of the segment of the first sub-channel data-sequence, and for setting a phase for the selected spreading-code for the first sub-channel to a phase selected from among a plurality of phases based on a second set of bits of the segment of the first sub-channel data-sequence, to produce a first spread-spectrum sub-channel signal;
a second mapping circuit coupled to receive the second sub-channel data-sequence signal, responsive to each segment of the second sub-channel data-sequence signal for selecting a spreading-code for the second sub-channel from among a plurality of spreading-codes based on a first set of bits of the segment of the second sub-channel data-sequence, and for setting a phase for the selected spreading-code for the second sub-channel to a phase selected from among a plurality of phases based on a second set of bits of the segment of the second sub-channel data-sequence, to produce a second spread-spectrum sub-channel signal;
a signal combiner for receiving and combining the first and second spread-spectrum sub-channel signals for transmission.
2. The multi-channel spread-spectrum modulator subsystem of claim 1 , wherein:
the demultiplexer is further for demultiplexing a third sub-channel data sequence signal from the representation of the input signal;
the subsystem further comprises a third mapping circuit coupled to receive the third sub-channel data-sequence signal from the demultiplexer, responsive to each segment of the third sub-channel data-sequence signal for selecting a spreading-code for the third sub-channel from among a plurality of spreading-codes based on a first set of bits of the segment of the third sub-channel data-sequence and for setting a phase for the selected spreading-code for the third sub-channel to a phase selected from among a plurality of phases based on a second set of bits of the segment of the third sub-channel data-sequence, to produce a third spread-spectrum sub-channel signal, and
the signal combiner combines the third spread-spectrum sub-channel signal together with the first and second spread-spectrum sub-channel signals for transmission.
3. The multi-channel spread-spectrum modulator subsystem of claim 1 , wherein each of the first and second mapping circuits comprises:
a code mapping circuit;
a phase mapping circuit; and
a product device for multiplying selected codes output by the code mapping circuit by selected phasors output by the phase mapping circuit.
4. The multi-channel spread-spectrum modulator subsystem of claim 1 , wherein the signal combiner comprises a complex signal combiner for algebraically combining the first and second spread-spectrum sub-channel signals as an in-phase multi-channel spread-spectrum signal and a quadrature multi-channel spread-spectrum signal.
5. The multi-channel spread-spectrum modulator subsystem of claim 4 , further comprising a radio frequency transmitter coupled to the complex signal combiner, for transmission of the in-phase multi-channel spread-spectrum signal and the quadrature multi-channel spread-spectrum signal over a wireless link.
6. The multi-channel spread-spectrum modulator subsystem of claim 5 , wherein the transmitter comprises:
a first spread-spectrum modulator for modulating the in-phase multi-channel spread-spectrum signal with a cover code; and
a second spread-spectrum modulator for modulating the quadrature multi-channel spread-spectrum signal with the cover code.
7. The multi-channel spread-spectrum modulator subsystem of claim 6 , wherein the transmitter further comprises:
a first multiplier for multiplying an output signal from the first spread-spectrum modulator by a carrier wave of a predetermined frequency and having a first phase; and
a second multiplier for multiplying an output signal from the second spread-spectrum modulator by a carrier wave of the predetermined frequency and having a second phase different from the first phase.