Multiple access communications system and method using code and time division

Claim 2

A communication method using Code Division Multiple Access comprising the steps of: assembling information into blocks of digital data; coding the blocks of digital data to form spread spectrum codewords; adding at least two of the spread spectrum codewords to form a composite signal; and time-compressing the composite signal for transmission in a timeslot.

Claim 3

The communication method of claim 1, further comprising the step of scrambling the spread spectrum codewords.

Claim 4

The communication method of claim 1, further comprising the step of selectively activating a receiver to receive the time-compressed composite signal during a selected time slot.

Claim 5

The communication method of claim 1, further comprising the steps of: receiving the time-compressed composite signal; determining a signal strength order corresponding to the spread spectrum codewords contained in the composite signal; and decoding the spread spectrum codewords in order of greatest to smallest signal strength and subtracting the spread spectrum codewords from the composite signal.

Claim 10

The method of claim 6, wherein said reconstructing step comprises error correction decoding.

Claim 11

The method of claim 7, wherein the error correction decoding is carried out with a Reed-Solomon decoder.

Claim 12

The method of claim 7, wherein the error correction decoding comprises convolutional decoding.

Claim 13

The method of claim 6, wherein the reconstructing step comprises digital voice decoding using at least one of Residual Excited Linear Predictive Coding, Sub-band, and Vector Code Book Excited Linear Predictive Coding speech decoding to produce an analog speech waveform.

Claim 14

The method of claim 6, wherein the reconstructing step includes transcoding digitally coded voice from at least one of Adaptive Delta Pulse Code Modulation, Residual Excited Linear Predictive Coding, Sub-band, and Vector Code Book Excited Linear Predictive Coding format to at least one of standard U-Law and A-Law Pulse Code Modulation format for interfacing with a public switched telephone network.

Claim 15

A communication apparatus comprising: block spreading means for assembling digital information into blocks and coding the blocks to produce spread spectrum codewords; timing means for allocating a timeslot in a repetitive frame period for transmission of the spread spectrum codewords; and burst formatting means for selecting at least two of the spread spectrum codewords and for time-compressing the at least two of the spread spectrum codewords for transmission in the allocated timeslot.

Claim 16

A communication apparatus comprising: block spreading means for assembling digital information into blocks and coding the blocks to produce spread spectrum codewords; timing means for allocating a timeslot in a repetitive frame period for transmission of the spread spectrum codewords; and burst formatting means for selecting at least two of the spread spectrum codewords and for time-compressing the at least two of the spread spectrum codewords for transmission in the allocated timeslot.

Claim 17

The communication apparatus of claim 12, further comprising scrambling means for combining the spread spectrum codewords with an access code to form scrambled spread spectrum codewords.

Claim 20

The apparatus of claim 14, wherein the spread spectrum coding means is located at the fixed station and the memory is located at the mobile station.

Claim 21

The apparatus of claim 14, further comprising source coding means which includes at least one of Adaptive Delta Pulse Code Modulation, Residual Excited Linear Predictive Coding, Sub-band, and Vector Code Book Excited Linear Predictive Coding speech coding means.

Claim 22

The apparatus of claim 14, further comprising at least one of convolutional error correction coding means, Reed-Solomon error correction coding means, bit time interleaving means, and symbol time interleaving means.

Claim 23

The apparatus of claim 14, wherein the spread spectrum coding means comprises at least one of orthogonal block spreading means, bi-orthogonal block spreading means, and chipwise modulo-2 adding means for scrambling the spread spectrum codewords using an access code.

Claim 24

A receiver comprising: an antenna for receiving a composite signal, the composite signal comprising at least two spread spectrum codewords which are time-compressed into a timeslot; radio receiver means connected to the antenna for filtering and amplifying the composite signal received by the antenna and for converting the composite signal into complex numerical samples; timing control means for activating the radio receiver means during the timeslot to thereby reduce power consumption; a memory for storing the complex numerical samples converted during the timeslot; and processing means coupled to the memory for processing the stored complex numerical samples, the processing means comprising: prediction means for predicting a signal strength of each of said spread spectrum codewords and for ordering the spread spectrum codewords in order of strongest to weakest signal strength; and iterative decoding means for decoding a strongest of the spread spectrum codewords and for subtracting the strongest of the spread spectrum codewords from the composite signal before decoding a next strongest of the spread spectrum codewords.

Claim 25

A receiver comprising: an antenna for receiving a composite signal, the composite signal comprising at least two spread spectrum codewords which are time-compressed into a timeslot; radio receiver means connected to the antenna for filtering and amplifying the composite signal received by the antenna and for converting the composite signal into complex numerical samples; timing control means for activating the radio receiver means during the timeslot to thereby reduce power consumption; a memory for storing the complex numerical samples converted during the timeslot; and processing means coupled to the memory for processing the stored complex numerical samples, the processing means comprising: prediction means for predicting a signal strength of each of said spread spectrum codewords and for ordering the spread spectrum codewords in order of strongest to weakest signal strength; and iterative decoding means for decoding a strongest of the spread spectrum codewords and for subtracting the strongest of the spread spectrum codewords from the composite signal before decoding a next strongest of the spread spectrum codewords.

Claim 26

The receiver of claim 19, wherein the processing means comprises a Fast Walsh Transform circuit.

Claim 27

The receiver of claim 19, wherein the iterative decoding means subtracts the spread spectrum codewords by setting to zero a transform component computed from the complex numerical samples.

Claim 28

The receiver of claim 19, wherein the iterative decoding means subtracts the spread spectrum codewords by despreading the spread spectrum codeword to produce a narrowband signal and removing the narrowband signal with at least one of a notch filter and a bandstop filter.

Claim 29

The receiver of claim 19, wherein; the prediction means predicts the signal strength of individual rays of the composite signal, the rays being received via relatively delayed paths, and orders the rays in order of strongest to weakest signal strength, the signal strength being determined by computing a total energy of the rays of a particular spread spectrum codeword; and wherein the iterative decoding means subtracts rays of already decoded signals until a predetermined spread spectrum codeword is decoded.

Claim 30

A receiver for receiving and decoding information signals comprising: multiple-element antenna means for receiving and resolving signals from different directions; multiple-channel processing means, connected to the antenna means, for filtering, amplifying, and digitizing a portion of the received information signals to produce sequences of complex numbers for storage in a memory; multi-dimensional decimating means for processing the stored sequences of complex numbers to separate the information signals according to channel frequency, time of arrival, and direction of arrival and for producing numerical sequences representative of overlapping Code Division Multiple Access signals; CDMA signal processing means for processing the numerical sequences to separate individual channel signals transmitted by a single transmitter to produce information symbols; and source decoding means for processing the information symbols to reconstruct the information signals transmitted by the individual transmitter.

Claim 31

A receiver for receiving and decoding information signals comprising: multiple-element antenna means for receiving and resolving signals from different directions; multiple-channel processing means, connected to the antenna means, for filtering, amplifying, and digitizing a portion of the received information signals to produce sequences of complex numbers for storage in a memory; multi-dimensional decimating means for processing the stored sequences of complex numbers to separate the information signals according to channel frequency, time of arrival, and direction of arrival and for producing numerical sequences representative of overlapping Code Division Multiple Access signals; CDMA signal processing means for processing the numerical sequences to separate individual channel signals transmitted by a single transmitter to produce information symbols; and source decoding means for processing the information symbols to reconstruct the information signals transmitted by the individual transmitter.

Claim 32

The receiver of claim 24, wherein the CDMA signal processing means iteratively decodes the CDMA signals in descending order of received signal strength.

Claim 33

The receiver of claim 24, wherein the source decoding means is located at a remote mobile communications gateway exchange and information signals are transmitted to the remote mobile communications gate exchange via a public switched telephone network.

Claim 36

The method of claim 27, further comprising the steps of: receiving the time-compressed burst and time expanding the time-compressed burst to reform a narrowband CDMA signal; and processing the restored narrowband CDMA signal to restore the information signals.

Claim 39

The method of claim 29, wherein said predetermined dynamic range defines a maximum difference in power level between a highest power CDMA signal and a lowest power CDMA signal.

Claim 40

The method of claim 29, wherein the power levels are spread such that each timeslot contains a substantially even distribution of low and high power signals.

Claim 41

The method of claim 29, wherein in each timeslot on the same frequency channel, a total transmitted power is substantially equal.

Claim 42

The method of claim 32, wherein on each frequency channel, the total transmitted power is substantially equal.

Claim 43

The method of claim 29, in which said first station is a base station serving a cell in a cellular mobile communications network.

Claim 44

The method of claim 29, wherein a first base station in a first cell transmits a relatively high total transmitted power on a first frequency, and a second base station in a second cell adjacent to the first cell transmits a relatively low total transmitted power on the first frequency.