Method and apparatus for using multiple modulation schemes for a single packet
Techniques for using multiple modulation schemes for a single packet are described. Each data packet is processed and transmitted in up to T blocks, where T>1. Multiple modulation schemes are used for the T blocks to achieve good performance. A transmitter encodes a data packet to generate code bits. The transmitter then forms a block of code bits with the code bits generated for the packet, determines the modulation scheme to use for the block (e.g., based on a mode/rate selected for the packet), maps the code bits for the block based on the modulation scheme to obtain data symbols, and processes and transmits the block of data symbols to a receiver. The transmitter generates and transmits another block in similar manner until the data packet is decoded correctly or all T blocks have been transmitted. The receiver performs the complementary processing to receive and decode the packet.
1. A method of receiving data in a communication system, comprising:
obtaining a plurality of blocks of received data symbols for a data packet, the plurality of blocks being received in succession with each successive block including the data packet with a higher amount of coding redundancy relative to a preceding block;
determining a mode for the data packet that is based on a single channel condition and indicates a modulation scheme to be used for each of the plurality of blocks prior to transmission of any of the plurality of blocks, wherein the mode indicates at least two different modulation schemes to be used for two or more different blocks from the plurality of blocks based on the single channel condition;
performing detection on each of the plurality of blocks of received data symbols in accordance with the modulation scheme used for the block to generate detected data symbols for the block; and
decoding detected data symbols generated from the plurality of blocks of received data symbols to obtain a decoded packet.
2. The method of claim 1 , wherein the performing detection on each of the plurality of blocks of received data symbols comprises
generating a set of log-likelihood ratios (LLRs) for a set of code bits for each received data symbol.
3. The method of claim 1 , wherein the performing detection on each of the plurality of blocks of received data symbols comprises
performing detection on a first block of received data symbols, obtained first, in accordance with a first modulation scheme having a highest order among the at least two different modulation schemes.
4. The method of claim 3 , wherein the performing detection on each of the plurality of blocks of received data symbols further comprises
performing detection on a second block of received data symbols, obtained second, in accordance with a second modulation scheme having a second highest order among the at least two different modulation schemes.
5. The method of claim 1 , wherein the decoding the detected data symbols comprises
after obtaining each of the plurality of blocks of received data symbols, decoding detected data symbols generated for all blocks of received data symbols to obtain the decoded packet.
6. An apparatus in a communication system, comprising:
a receiver unit operative to obtain a plurality of blocks of received data symbols for a data packet, the plurality of blocks being received in succession with each successive block including the data packet with a higher amount of coding redundancy relative to a preceding block;
a controller operative to determine a mode for the data packet that is based on a single channel condition and indicates a modulation scheme to be used for each of the plurality of blocks prior to transmission of any of the plurality of blocks, wherein the mode indicates at least two different modulation schemes to be used for two or more different blocks from the plurality of blocks based on the single channel condition;
a detector operative to perform detection on each of the plurality of blocks of received data symbols in accordance with the modulation scheme used for the block to generate detected data symbols for the block; and
a decoder operative to decode detected data symbols generated from the plurality of blocks of received data symbols to obtain a decoded packet.
7. The apparatus of claim 6 , wherein the detector is operative to perform detection on a block of received data symbols, obtained first, in accordance with a first modulation scheme having a highest order among the at least two different modulation schemes.
8. An apparatus in a communication system, comprising:
means for obtaining a plurality of blocks of received data symbols for a data packet, the plurality of blocks being received in succession with each successive block including the data packet with a higher amount of coding redundancy relative to a preceding block;
means for determining a mode for the data packet that is based on a single channel condition and indicates a modulation scheme to be used for each of the plurality of blocks prior to transmission of any of the plurality of blocks, wherein the mode indicates at least two different modulation schemes to be used for two or more different blocks from the plurality of blocks based on the single channel condition;
means for performing detection on each of the plurality of blocks of received data symbols in accordance with the modulation scheme used for the block to generate detected data symbols for the block; and
means for decoding detected data symbols generated from the plurality of blocks of received data symbols to obtain a decoded packet.
9. A method of receiving data in a communication system, comprising:
obtaining a block of received data symbols for a data packet;
determining a modulation scheme used for the block of received data symbols;
performing detection on the block of received data symbols in accordance with the modulation scheme to generate detected data symbols for the block, wherein each detected data symbol is an estimate of a modulation symbol for the data packet;
decoding detected data symbols generated from all blocks of received data symbols obtained for the data packet to derive a decoded packet; and
repeating the obtaining the block of received data symbols, the determining the modulation scheme used for the block, the performing detection on the block of received data symbols, and the decoding the detected data symbols for another block of received data symbols if the data packet is decoded in error and if a maximum number of blocks of received data symbols have not been obtained for the data packet, wherein the another block of received data symbols includes the data packet in association with a higher amount of coding redundancy relative to the block of received data symbols, and wherein at least two different modulation schemes that are specified by a mode for the data packet are used for the maximum number of blocks of received data symbols, the mode being selected based on a single channel condition prior to any blocks being received for the data packet.
10. The method of claim 9 , further comprising:
combining multiple detected data symbols generated for each modulation symbol.