High rate Reed-Solomon concatenated trellis coded 16 star QAM system for transmission of data over cellular mobile radio

• US 5,659,578 A
• Filed: 11/23/1994
• Issued: 08/19/1997
• Est. Priority Date: 11/23/1994
• Status: Expired due to Term

• Current Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Original Assignee: AT&T Wireless Services Incorporated (AT&T, Inc.)
• Inventors: Wright, Andrew S., Alamouti, Siavash M., Haymond, William D.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Kim, Kevin
• Application Number:
  US08/344,156
• Time in Patent Office: 1,000 Days
• Field of Search: 375/261, 375/262, 375/265, 375/341, 375/268, 375/273, 375/298, 375/300, 375/302, 371/43-46, 332/145
• US Class Current: 375/261
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 27/3427 in which the constellation is the n - fold Cartesian product of a single underlying two-dimensional constellation
• CPC Class Codes: H04L 7/04 Speed or phase control by synchronisation signals H04L7/0075 takes precedence

Abstract

A cellular communication system provides for trellis encoding/decoding of a 16 Star QAM signal. The system includes a transmitter circuit and a receiver circuit. The transmitter circuit has a Reed-Solomon encoder, an outer interleaver circuit for spreading burst errors, a cyclic trellis encoder, an inner interleaver circuit for reducing channel memory, a 16 Star QAM mapper and a radio frequency transmitter. The receiver circuit has a radio frequency receiver, equalization and filtering circuitry and timing and synchronization recovery circuitry. The receiver also has an inner deinterleaver, a trellis decoder, an outer deinterleaver, and a Reed-Solomon decoder.

Claims

1. A wireless communication system for transmission of signals mapped according to 16 star QAM modulation scheme, said communication system comprising:

a transmitting circuit, said transmitting circuit comprising;

a Reed-Solomon (63,53) block encoder;

an outer block interleaver coupled to said Reed-Solomon encoder;

a rate 3/4 trellis encoder coupled to said outer interleaver;

an inner block interleaver coupled to said trellis encoder;

a frame synchronization insertion circuit coupled to said inner interleaver;

a pilot word insertion circuit coupled to said frame synchronization insertion circuit;

a 16 star QAM mapper coupled to said pilot word insertion circuit;

a first baseband filter coupled to said 16 star QAM mapper; and

a transmitter coupled to said filter; and

;

a receiver circuit, said receiver circuit comprising;

a receiver;

a second baseband filter coupled to to said receiver;

an equalizer filter which receives input from said second baseband filter, said equalizer filter also receiving input from an equalizer estimator circuit;

a symbol timing recovery circuit coupled to receive input from said second baseband filter and to provide outputs to said equalizer estimator circuit and to a sampler circuit;

an automatic frequency control circuit which receives input from said equalizer filter, and provides output to said sampler, said frequency control circuit further receiving input from an oscillator circuit;

a pilot word extraction circuit and a frame synchronization extraction circuit which receive inputs from said sampler,

a channel estimator circuit which receives input from said pilot word extraction circuit and provides control outputs to said oscillator circuit and said equalizer estimator;

a multiplier circuit which receives inputs from said sampler and said channel estimator;

an inner deinterleaver circuit which receives inputs from said multiplier circuit, said frame synchronization extraction circuit, and said channel estimator circuit;

a trellis decoder circuit coupled to said inner deinterleaver;

an outer deinterleaver coupled to said trellis decoder; and

a Reed-Solomon decoder coupled to said outer deinterleaver.

2. A mobile radio communication system, comprising:

a trellis encoder which receives data and trellis encodes said data;

a 16 star QAM mapper coupled to said trellis encoder and configured to encode data from said trellis encoder and to map said encoded data into a 16 star QAM signal constellation;

a transmitter configured to accept the encoded and map data and to transmit said encoded and mapped data over a communication channel;

a receiver configured to receive the transmitted data from said communication channel;

a trellis decoder coupled to said receiver; and

an inner interleaver coupled between said trellis encoder and said 16 star QAM mapper and an inner deinterleaver coupled between said radio frequency receiver and said trellis decoder.

3. A communication system as defined in claim 2, further comprising a frame synchronization insertion circuit between said inner interleaver and said 16 star QAM mapper.

4. A communication system as defined in claim 3, further comprising a pilot word insertion circuit between said frame synchronization insertion circuit and said 16 star QAM mapper.

5. A communication system as defined in claim 4, wherein said pilot word insertion circuit inserts a differential pilot word comprising at least two adjacent pilot channel symbols.

6. A communication system as defined in claim 5, further comprising a feedback controlled equalizer filter, a sampler circuit, a pilot word extraction circuit and a frame synchronization extraction circuit coupled between said radio frequency receiver and said inner deinterleaver.

7. A mobile radio communication system, comprising:

a trellis encoder which receives data and trellis encodes said data;

a 16 star QAM mapper coupled to said trellis encoder and configured to encode data from said trellis encoder and to map said encoded data into a 16 star QAM signal constellation;

a transmitter configured to accept the encoded and map data and to transmit said encoded and mapped data over a communication channel;

a receiver configured to receive the transmitted data from said communication channel;

a trellis decoder coupled to said receiver; and

a pilot word insertion circuit coupled between said trellis encoder and said 16 star QAM mapper.

8. A communication system as defined in claim 7, wherein said pilot word insertion circuit inserts a differential pilot word comprising at least two adjacent pilot channel symbols.

9. A method of rate 3/4, cyclic trellis encoding a 16 star QAM signal by means of a 16-state cyclic trellis encoder, said method comprising the steps of:

receiving a three-bit input signal which is to be encoded into a four-bit output signal, said three-bit input signal corresponding to eight possible input values and said four-bit output signal corresponding to 16 possible output values;

compiling an output look-up circuit wherein said 16 possible output values are defined as a function of said eight input values and 16 present states of said cyclic trellis encoder, said output table outputting consecutively increasing even output values upon the application of consecutively increasing input values while in an even present state, and said output table outputting consecutively increasing odd output values upon the application of consecutively increasing input values while in an odd present state;

compiling a state transition look-up circuit wherein 16 next state values of said cyclic trellis encoder are defined as a function of said eight input values and said 16 present states of said cyclic trellis encoder, said state transition circuit outputting the first eight consecutive next state values upon consecutive application of said eight input values when in a first even present state, and outputting next state values which are cyclicly shifted by one value from the next state values defined for the immediately previous even present state value upon application of said eight consecutive input values for consecutively increasing even present state values, and said state transition circuit outputting the second eight consecutive next state values upon consecutive application of said eight input values when in a first odd present state, and outputting next state values which are cyclicly shifted by one value from the next state values defined for the immediately previous odd present state value upon application of said eight consecutive input values for consecutively increasing odd present state values;

applying said three-bit input signal to an input of said state transition circuit, thereby generating a next state value;

storing said next state value over the duration of one input cycle until said stored next state value becomes a present state value;

applying said present state value to an input of said output look-up circuit while simultaneously applying said three-bit input signal to another input of said output look-up circuit, thereby generating one of said 16 possible output values; and

assigning a phase and amplitude coordinate in a 16 star QAM signal constellation to each of said output values generated by said output look-up circuit.