Method and apparatus for time efficient retransmission using symbol accumulation

• US 6,101,168 A
• Filed: 11/13/1997
• Issued: 08/08/2000
• Est. Priority Date: 11/13/1997
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tiedemann, Edward G. Jr., Chen, Tao, Odenwalder, Joseph P., Willenegger, Serge
• Primary Examiner(s): MARCELO, MELVIN C
• Application Number:
  US08/969,319
• Time in Patent Office: 999 Days
• Field of Search: 370/227, 370/228, 370/335, 370/342, 370/479, 714/748-751
• US Class Current: 370/228
• CPC Class Codes: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• 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 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/0068 by puncturing
• CPC Class Codes: H04L 1/0069 Puncturing patterns
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04L 1/1816 with retransmission of the same, encoded, message
• CPC Class Codes: H04L 1/1819 with retransmission of additional or different redundancy
• CPC Class Codes: H04L 1/1825 Adaptation of specific ARQ protocol parameters according to transmission conditions
• CPC Class Codes: H04L 1/1845 Combining techniques, e.g. code combining
• CPC Class Codes: H04L 1/1867 Arrangements specially adapted for the transmitter end
• CPC Class Codes: H04L 1/1893 Physical mapping arrangements physical resource mapping in general H04L5/00
• CPC Class Codes: H04W 52/44 in connection with interruption of transmission

Abstract

An efficient retransmission of data using symbol accumulation wherein the packet received in error is retransmitted at a lower energy-per-bit level concurrently in the same frame with the new packet. The destination device receives the data transmission and retransmission, demodulate the signal, and separates the received data into the new and retransmitted packet. The destination device then accumulates the energy of the retransmitted packet with the energy already accumulated for the packet received in error and decodes the accumulated packet. The accumulation of the additional energy provided by the subsequent retransmissions improves the probability of a correct decoding. The throughput rate can be improved since the packet received in error is retransmitted concurrently with the transmission of the new data packet. The capacity is maximized since the retransmission of the packet received in error is at a lower energy level than that of the new packet.

Claims

1. A method for decoding a data packet comprising the steps of:

first receiving a transmission of said data packet to obtain a received packet;

second receiving at least one retransmission of said data packet to obtain retransmitted packets;

accumulating said received packet with said retransmitted packets to obtain an accumulated packet; and

decoding said accumulated packet

scaling code symbols of said received packet with a first gain factor;

scaling code symbols of each of said retransmitted packets with second gain factors; and

combining said code symbols of said received packet with said code symbols of said retransmitted packets to obtain said accumulated packet.

2. The method of claim 1 wherein said first receiving step comprises the steps of:

demodulating at least one signal path of said transmission of said data packet to obtain first pilot signals and first filtered data symbols;

performing a dot product of said first pilot signals and said first filtered data symbols for each of said at least one signal path to obtain first scalar values; and

combining said first scalar values of said least one signal path to obtain first combined scalar values;

said first combined scalar values comprising said received packet.

3. The method of claim 1 wherein said second receiving step comprises the steps of:

demodulating at least one signal path of said at least one retransmission of said data packet to obtain second pilot signals and second filtered data symbols;

performing a dot product of said second pilot signals and said second filtered data symbols for each of said at least one signal path to obtain second scalar values; and

combining said second scalar values of said least one signal path to obtain second combined scalar values;

said second combined scalar values comprising said retransmitted packets.

4. The method of claim 1 wherein said first gain factor is defined in accordance with a signal-to-noise measurement of a received signal of said transmission and said second gain factors are defined in accordance with signal-to-noise measurements of received signals of said at least one retransmissions.

5. The method of claim 1 wherein said accumulating step comprises the steps of:

replacing selected symbols of said received packet with symbols of said retransmitted packets to obtain said accumulated packet.

6. The method of claim 1 wherein said accumulating step comprises the steps of:

interleaving symbols of said received packet with symbols of said retransmitted packets to obtain said accumulated packet; and

wherein said decoding step is performed in accordance with a rate of said accumulated packet.

7. The method of claim 1 wherein said at least one retransmission of said data packet is concurrent with a transmission of a second data packet.

8. The method of claim 7 wherein said at least one retransmission of said data packet is achieved by replacing repeated symbols of said second data packet with code symbols of said data packet.

9. The method of claim 7 wherein said at least one retransmission of said data packet is achieved by encoding said second data packet with a modified code rate.

10. The method of claim 7 wherein said at least one retransmission of said data packet is achieved by transmitting said data packet on an additional code channel.

11. The method of claim 1 wherein each of said at least one retransmission is at a lower energy-per-bit than said transmission.

12. The method of claim 11 wherein each of said at least one retransmission is at a minimal energy-per-bit which still allows for correct decoding of said data packet.

13. The method of claim 12 wherein said minimal energy-per-bit is computed in accordance with a required E_s /I_o and a measured E_s /I_o of a received signal of said transmission.

14. The method of claim 12 wherein said minimal energy-per-bit is computed in accordance with a required E_s /I_o and an accumulated E_s /I_o of received signals of said transmission and said at least one retransmission.

15. The method of claim 1 wherein each of said retransmitted packets comprises a portion of said received packet.

16. The method of claim 15 wherein each of said retransmitted packets is based on a measured E_s /I_o for a duration of said received packet.

17. The method of claim 1 wherein decoding step is performed for a constraint length of 9.

18. The method of claim 1 wherein decoding step is performed for a code rate of 1/2.

19. An apparatus for decoding a data packet comprising:

demodulation means for receiving and demodulating a transmission of said data packet to obtain a received packet and for receiving and demodulating at least one retransmissions of said data packet to obtain retransmitted packets;

accumulation means for accumulating said retransmitted packets with said received packet to produce an accumulated packet; and

storage means for receiving and storing said received packet and/or said accumulated packet;

decoding means for receiving and decoding said accumulated packet;

transmission means for concurrently retransmitting said at least one retransmission of said data packet with a transmission of a second data packet and for adjusting a transmission power of said at least one retransmission of said data packet to be lower than a transmission power of said transmission of said data packet.

20. The apparatus of claim 19 further comprising:

scaling means for receiving and scaling said received packet and said retransmitted packets to produce a scaled received packet and scaled retransmitted packets;

wherein said accumulation means received and accumulate said scaled retransmitted packets with said scaled received packets to produce said accumulated packet.