AG Kommunikationstheorie


SDR Implementation of Resource Allocation in COFDM Systems


The waterfilling solution offers optimal power and rate allocation over subcarriers when continuous rates are available. Since practical systems do not allow for transmission of any real number of data bits over subcarriers, several efficient solutions for optimal (discrete) bit and power loading over subcarriers is proposed in recent years.

The performance of OFDM transmission can be also optimized through the use of channel codes, forming Coded OFDM (COFDM) system. In such a way, a deep spectral fade is spreaded over all subcarriers introducing only the slight distortion over them which can be correctly decoded. An additional improvement of the system performance can be achieved by efficient combination of adaptive bit/power loading and channel codes by including coding rates and coding gains into optimization procedures.

The development issues and evaluation results of an effective method for joint coding and bit/power allocation in OFDM systems will be presented. Furthermore, efficient deployment of proposed solution in GNU Radio-based OFDM testbed gave insight into implementation impairments which are common for real communication systems.

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