Method and apparatus for selecting link adaptation parameters for CDMA-based wireless communication systems
A method and apparatus enhance the selection of transport block set size (TBSS), number of spreading codes, and modulation type, referred to collectively as transport format resource combination (TFRC), in a medium access control (MAC) layer for transmission of data in a code division multiple access (CDMA) wireless communication system, preferably a Universal Mobile Telecommunications Systems (UMTS) high speed downlink packet access (HSDPA) communication system. The maximum number of spreading codes available for transmission and the set of possible TFRCs are preferably determined based on a channel characteristics provided in part by a channel quality indicator (CQI). For each TBSS value in the set of possible TFRCs, a TFRC is selected with the largest number of spreading codes within the maximum number of spreading codes for which the corresponding coding rate is preferably at least ⅓. The corresponding code rate for each selected TFRCs is compared to a threshold to select a corresponding type of modulation. One of the selected TFRCs is selected to be provided to the PHY layer that best matches the CQI and preferably has a maximum TBSS.
1. A method for use in wireless communication, the method comprising:
selecting a transport format resource combination (TFRC) based on a transport block set size (TBSS) associated with the TFRC, such that:
an expected data rate associated with the TFRC is maximized and is not greater than a maximum expected data rate,
a transport block (TB) success rate probability associated with the TFRC is not less than a minimum TB success rate probability,
a number of spreading codes associated with the TFRC is maximized and is not greater than a maximum number of spreading codes, and
a code rate associated with the TFRC is maximized, is not less than a minimum code rate, and is not greater than a maximum code rate; and
transmitting via a code division multiple access (CDMA) channel using the selected TFRC.
2. The method of claim 1 , wherein the selecting a TFRC includes determining the maximum expected data rate based on a channel quality indicator (CQI) value corresponding to the CDMA channel.
3. The method of claim 1 , wherein the selecting a TFRC includes determining the maximum code rate by evaluating a measured throughput for a received signal-to-noise ratio (SNR).
4. The method of claim 1 , wherein the selecting a TFRC includes:
generating a plurality of group TFRCs by selecting a group TFRC for each of a plurality of TBSSs; and
selecting the TFRC from the plurality of group TFRCs.
5. The method of claim 1 , wherein the selecting a TFRC includes selecting the TFRC such that the TBSS associated with the TFRC is maximized.
6. A wireless transmit/receive unit (WTRU) comprising:
a processor configured to select a transport format resource combination (TFRC) based on a transport block set size (TBSS) associated with the TFRC, such that:
an expected data rate associated with the TFRC is maximized and is not greater than a maximum expected data rate,
a transport block (TB) success rate probability associated with the TFRC is not less than a minimum TB success rate probability,
a number of spreading codes associated with the TFRC is maximized and is not greater than a maximum number of spreading codes, and
a code rate associated with the TFRC is maximized, is not less than a minimum code rate, and is not greater than a maximum code rate; and
a transmitter configured to transmit via a code division multiple access (CDMA) channel using the selected TFRC.
7. The WTRU of claim 6 , wherein the processor is configured to determine the maximum expected data rate based on a channel quality indicator (CQI) value corresponding to the CDMA channel.
8. The WTRU of claim 6 , wherein the processor is configured to determine the maximum code rate by evaluating a measured throughput for a received signal-to-noise ratio (SNR).
9. The WTRU of claim 6 , wherein the processor is configured to:
generate a plurality of group TFRCs by selecting a group TFRC for each of a plurality of TBSSs; and
select the TFRC from the plurality of group TFRCs.
10. The WTRU of claim 6 , wherein the processor is configured to select the TFRC such that the TBSS associated with the TFRC is maximized.