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The residual energy in multi-code CDMA systems is not used to transmit any useful information and may increase up to the incremental energy multiplied with the number of multi-code channels. A two-group resource allocation scheme is developed to reduce this upper bound on the residual energy down to as low as a single-channel incremental energy, resulting higher energy utilization to improve the sum capacity. Since the incremental energy is the additional energy required to increase a data rate to a higher data rate by an additional amount called bit granularity, a new design of modulation and coding scheme based on the rate multiplication of outer and inner codes can be developed to produce different data rates such that the bit granularity is reduced, hence decreasing the incremental energy to further maximize the sum capacity. The two-group resource allocation scheme implemented with the proposed modulation and coding scheme is observed to have a 4 dB gain over the current HSDPA systems.
Date of Conference: 13-16 Sept. 2009