US 5,914,959 AGranted

Digital communications system having an automatically selectable transmission rate

AssigneeGlenayre Electronics, Inc.

InventorsRob Marchetto, Claudio Rey

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Abstract

A system and method for maintaining communication between a paging base station (transceiver) and a mobile paging unit when signal reception is below a level that would otherwise be unacceptable. The system changes from one data transmission rate to another depending upon the quality of the communication channel. In particular, the symbol rate of the transmissions remains the same, but the number of modulation states and bits per symbol is decreased or increased depending upon the bit error rate of the received signal. In some arrangements, the transceiver transmits at the highest bit rate for that particular system. If no response is received from the paging unit or the paging unit sends a response signal back to the transceiver indicating the signal sent is unacceptable, the transceiver retransmits at a lower bit rate. In other arrangements, the receiver determines the highest data rate within the group of data rates available and transmits a signal representative of that data rate to the base station. In response to such a signal, the base station transmits at the requested data rate until a different data rate is requested.

Claims6

Dependent claims

A variable transmission rate communications system comprising:

(a) a base transmitter for transmitting a data signal at an initial constellation pattern and bit rate, said data signal being a digitally encoded data stream, that is divided into frames that include pilot symbol blocks and information symbols, said pilot symbol blocks each including a predetermined symbol sequence;
(b) a mobile receiver including means for receiving said transmitted signal, said mobile receiver further including a demultiplexer for separating said received signal into separate pilot symbol blocks and information symbols, said mobile receiver further including a pilot symbol block processor having:
(i) means for detecting the symbol sequence of a received pilot symbol block and comparing the detected symbol sequence to the predetermined pilot symbol block sequence used in said transmitted data stream;
(ii) means for producing a quality signal according to said comparison, said quality signal being representative of the acceptability of said received data signal;
and
(iii) means for generating a back-off signal if said quality signal is below a threshold level indicating that said received data signal is unacceptable and transmitting said back-off signal;
and
(iv) a demodulator for receiving said information symbols, if said quality signal indicates the received data signal is acceptable;
and
(c) a retransmission means located in said base transmitter for retransmitting the data signal at a next lower constellation pattern rate if said back-off signal is received from said mobile receiver, said backoff indicating that said received data signal has a quality level below said threshold level.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/743,983Filed 31 Oct 1996
Granted: 22 Jun 1999
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

H04L 1/1893
Arrangements specially adapted for the transmitter end: physical mapping arrangements
H04L 1/0003
By adapting the transmission rate: by switching between different modulation schemes
H04L 1/1671
Details of the supervisory signal: the supervisory signal being transmitted together with control information
Y02D 30/50
Reducing energy consumption in communication networks: in wire-line communication networks, e.g. low power modes or reduced link rate