Method and apparatus for multirate data communications

• US 5,974,106 A
• Filed: 09/01/1995
• Issued: 10/26/1999
• Est. Priority Date: 09/01/1995
• Status: Expired due to Term

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Dupont, Pierre B., Gerhards, Ronald H., Spear, Stephen Lee
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): Webster, Bryan
• Application Number:
  US08/522,905
• Time in Patent Office: 1,516 Days
• Field of Search: 375/219, 375/220, 375/222, 375/259, 375/260, 375/287, 375/377, 455/73, 370/442, 370/498, 341/61, 341/60
• US Class Current: 375/377
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0015 characterised by the adaptation strategy
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0027 Scheduling of signalling, e.g. occurrence thereof
• CPC Class Codes: H04W 72/54 based on quality criteria
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

In one embodiment a system is provided for multirate communications allowing for different data rates for each data unit on a channel, including both data units from different mobile units and from the same mobile unit. A sending unit preferably begins by determining the rate at which to start communications, and monitors, for example by use of an RSSI detector, for an indication that the rate should be changed. A rate adjustor implements the change, and can make changes as frequently as every data unit. The encoder applies the appropriate rate and inserts a rate indicator indicative of the data or encoding rate, and sends the data unit. On receiving data units, the receiving unit first determines the rate for each data unit or group of units, then appropriately decodes the data unit(s). As a result, the actual data throughput can be adjusted to permit optimized throughput.

Claims

1. A method of communicating data in a communications system comprising:

encoding a first service data unit into plural packet data units all at a first data rate, including inserting a synchronization sequence and synchronization flag bits wherein the synchronization flag bits form an indicator of the first data rate;

transmitting plural packet data units;

determining that an error measure for at least some of the plural packet data units exceeds a predetermined threshold;

determining a second data rate based on the error measure for at least some of the plural packet data units; and

encoding a second service data unit into plural packet data units at the second data rate, including a further synchronization sequence and further synchronization flag bits wherein the further synchronization flag bits form an indicator of the second data rate.

2. A method of communicating data from multiple senders to a single receiver over a common transmission channel in a communication system comprising:

encoding first data units from a first sender at a first data rate, including inserting into each first data unit a synchronization sequence and synchronization flag bits wherein the synchronization flag bits form an indicator of the first data rate;

transmitting the first data units from the first sender on the common transmission channel to the single receiver;

encoding second data units from a second sender, at a second data rate, including inserting into each second data unit a further synchronization sequence and further synchronization flag bits wherein the further synchronization flag bits form an indicator of the second data rate;

transmitting the second data units from second sender on the common transmission channel to the single receiver;

determining from the synchronization flag bits that were inserted into the first data unit the first data rate; and

determining from the further synchronization flag bits that were inserted into the second data unit the second data rate, wherein the further synchronization flag bits inserted into the second data unit indicate a same data rate as that of the synchronization flag bits inserted into the first data unit.

3. A method of communicating data units from multiple senders at multiple rates to a single receiver over a common transmission channel in a communications system, the method comprising:

receiving a first data unit including a data unit rate indicator, wherein the data unit rate indicator comprises one of a set of synchronization flag bits and the first data unit includes a synchronization sequence and first synchronization flag bits;

determining from the data unit rate indicator a rate at which the first data unit is encoded;

decoding the first data unit based on said rate;

determining that said rate should be changed;

transmitting a response indicative of a need to change said rate;

receiving a second data unit including a further synchronization sequence and further synchronization flag bits;

determining from the further synchronization flag bits that the second data unit is encoded at a second data rate; and

decoding the second data unit based on said second data rate.

4. A communications unit for sending multirate data communications comprising:

a transceiver;

a processor, coupled to the transceiver, comprising an encoder operable to receive data and encode the data in data units each at one of plural rates, and a rate adjuster operable to control the encoder to encode the data units each at a selected rate; and

a rate determination unit, coupled to the processor, operable to determine when to change from a first selected rate for a first data unit to a second selected rate for a following second data unit and communicating to the rate adjuster to change to the second selected rate,

wherein the rate determination unit includes a channel quality detector for determining a channel quality corresponding to a quality measure of at least the first data unit, the channel quality detector comprising a comparison means for receiving error information from another communications unit receiving the data units and comparing the error information with a threshold to determine when to change from the first selected rate.