Synchronous CDMA transmitter/receiver
First Claim
1. A synchronous CDMA transmitting station which is comprised of:
- a modulator circuit that modulates data siqnals with a spreading code to thereby generate CDMA signals;
a transmitter circuit, coupled to said modulator circuit, for sending, a replica of said CDMA signals on a CDMA channel;
an error receiver circuit, for receiving an error signal from a feedback channel; and
,an error correction circuit, coupled to said error receiver circuit, which time shifts said replica of said CDMA signals on said CDMA channel in response to said error signal.
9 Assignments
0 Petitions
Accused Products
Abstract
A multipoint-to-point CDMA communication system comprises a plurality of CDMA transmitting stations and a single CDMA receiving station, all of which are intercoupled to each other over one CDMA channel and one feedback channel. On the one CDMA channel, the plurality of CDMA transmitting stations simultaneously send respective CDMA signals to the receiving station. In the receiving station, respective time differences are measured between a reference clock signal and the spreading codes in the CDMA signals from each of the CDMA transmitting stations; and these time differences are indicated in respective error signals which the CDMA receiving station sends on the feedback channel to each of the CDMA transmitting stations. Each CDMA station responds to its error signals by time shifting its spreading code such that it arrives in the receiving station in synchronization with the reference clock signal. This synchronization enables interference between the spreading codes at the receiving station to be reduced by using codes which have minimal cross-correlation when their time difference is zero; and consequently, the maximum number of stations that can simultaneously transmit is increased.
62 Citations
6 Claims
-
1. A synchronous CDMA transmitting station which is comprised of:
-
a modulator circuit that modulates data siqnals with a spreading code to thereby generate CDMA signals; a transmitter circuit, coupled to said modulator circuit, for sending, a replica of said CDMA signals on a CDMA channel; an error receiver circuit, for receiving an error signal from a feedback channel; and
,an error correction circuit, coupled to said error receiver circuit, which time shifts said replica of said CDMA signals on said CDMA channel in response to said error signal. - View Dependent Claims (2, 3)
-
-
4. A synchronous CDMA receiving station which is comprised of:
-
a receiver circuit for receiving a CDMA signal over a CDMA channel where said CDMA signal includes the sum of a plurality of data signals which are modulated with respective spreading codes; an error detection circuit, coupled to said receiver circuit, which detects respective time differences between said spreading codes in said received CDMA signal and a single reference clock signal; and
,an error sending circuit, coupled to said error detection circuit, which sends respective error signals on a feedback channel that indicate said time differences. - View Dependent Claims (5, 6)
-
Specification