Spread-time code division multiple access technique with arbitrary spectral shaping

• US 5,177,768 A
• Filed: 06/22/1992
• Issued: 01/05/1993
• Est. Priority Date: 11/22/1991
• Status: Expired due to Term

• Current Assignee: Telcordia Technologies Incorporated (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Bell Communications Research, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Honig, Michael L., Crespo, Pedro M., Salehi, Jawad A.
• Primary Examiner(s): Barron, Jr, Gilberto
• Application Number:
  US07/901,827
• Time in Patent Office: 197 Days
• Field of Search: 375/1, 375/60, 370/18, 370/19, 370/21, 370/23
• US Class Current: 375/296
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04L 5/02 Channels characterised by the type of signal

Abstract

A spread-time code division multiple access (ST-CDMA) technique is disclosed for bandlimited access to a channel. With ST-CDMA, pseudo-random (PN) sequences are assigned to each transmitter in the multi-transmitter system, and the Fourier transform of the transmitter pulse for a given transmitter is determined by modulating the phase of the desired transmitter spectrum by the PN sequence assigned to the transmitter. The data symbols produced by the transmitter are conveyed by delayed versions of the transmitter pulse. The transmitted data for a particular transmitter is recovered at a receiver synchronized to the transmitter by sampling the output of a filter matched to the corresponding transmitter pulse.

Claims

1. Circuitry in a transmitter for spectrally encoding a transmitted time signal for propagation over a channel to a receiver, the channel having a given frequency domain characteristic and noise interference, the transmitter providing a source of data symbols operating at a symbol rate, the circuitry comprising

a short pulse generator for generating short pulses at the symbol rate,

a multiplier, responsive to the source of data symbols and said short pulse generator, for generating a stream of modulated pulses at the symbol rate, and

a filter, responsive to said stream of modulated pulses, for producing the transmitted time signal as the output of said filter, said filter having an impulse response characteristic determined from the frequency domain characteristic of the channel, the noise interference, and a pseudonoise sequence so as to maximize a signal-to-interference ratio at the receiver given a power constraint on the energy of said impulse response signal.

2. A method in a transmitter for spectrally encoding a transmitted time signal for transmission over a channel to a receiver, the channel having a given frequency domain characteristic and noise interference, the transmitter supplying a source of data symbols at a symbol rate, the method comprising the steps of

generating short pulses at the symbol rate,

modulating said short pulses with the data symbols to produce a a stream of modulated pulses, and

filtering said stream of modulated pulses with a filter to produce the transmitted time signal, said filter having an impulse response signal determined from the frequency domain characteristic of the channel, the noise interference, and a pseudo-noise sequence so as to maximize a signal-to-interference ratio at the receiver given a power constraint on said impulse response signal.