Enhancement of Data Transmission Rates for HSDPA Systems
The enhancement of data transmission rates is relevant to high speed downlink packet access (HSDPA) systems, such as the system shown in Figure 1. In particular, there is growing interest in data rate improvements for Femtocells, for which high data rates and complexity are delivered for localised distribution. New standards are actively evolving to allow these new technologies to be integrated with improved performance. Currently, there are limitations because the signal processing units in Femtocell base-stations offer a high, but limited processing capability.
The inventor has been able to show improvements in the performance of HSDPA systems using the current FPGA (Field Programmable Gate Array) and signal processing technologies and has demonstrated their suitability for HSDPA-based Femtocells.
This present technology improves data rates over multi-code parallel channels by incorporating efficient resource allocation together with algorithms for the power loading.
In previous arrangements, complicated power allocations for the channels (which have varying Signal to Noise Ratios, SNRs), were developed to provide equal energy and data rates for each channel by ensuring that the minimum channel SNR is above a set SNR threshold. This is known as the equal energy loading method. However, equal energy loading causes a significant value of SNR to be wasted (and corresponding wasted data).
In order to eliminate the wasted SNR, the received SNRs for all channels should be made equal and slightly above a chosen threshold, which then requires an unequal energy loading. This results in a substantial amount of residual energy not being used to transmit data (but improving inter-symbol interference, ISI, and multi-access interference, MAI).
The present invention arranges to further increase the data rates, using a “two-group resource allocation scheme,” which utilizes the residual energy to transmit useful information by separating the transmission into high-rate and low-rate channel groups. It is ideally suited for FPGA and signal processing implementations to provide improved performance for the HSDPA-based Femtocells. First results are shown in Figure 2.
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