Rate and power adaption techniques for wireless communication systems
Ong, Lay Teen
arxiv: Computer Science::Information Theory
Attaining the most spectrally efficient form of data transmission over a time- varying channel remains as fundamentally important target in wireless systems. Link adaptation (LA) is a promising approach to increase spectral efficiency. In general, the transmitter adjusts its parameter such as rate, power and coding in accordance with the channel state information (CSI) fed back from the receiver. Consequently, the accuracy of the CSI is prevalent in LA design. In this thesis, an investigation of the performance of a variable rate variable power (VRVP) multi-level quadrature amplitude modulation (MQAM) scheme is performed for a single antenna system. Then, a novel VRVP-MQAM system is proposed that employs a rate and power adaptation algorithm based on the statistical characterization of CSI imperfection. Instead of using the conventional signal-to-noise ratio (SNR) estimate as a CSI parameter, the proposed system is based on both an SNR estimate and a bit error rate (BER) estimate, as BER is a more direct representation for quality of service (QoS) of a communication system. The pro posed rate and power adaptation algorithm is then generalized to incorporate a pilot symbol assisted modulation (PSAM) based channel predictor. The BER and SNR estimates are then employed within a code division multiple access (CDMA) based rate and power adaptation system. Finally, the performances of the pro posed systems are shown to achieve higher spectral efficiency when compared to the alternative systems derived based on conventional approach. Another requirement in today's wireless digital communication systems is to provide services for integrated voice and data traffic. The QoS requirement for voice and data can be application specific. For example, real-time traffic is delay-constrained, whereas non-real time traffic has a relaxed requirement on delay but may be capacity-constrained. With this motivation, a rate and power adaptation technique is proposed for a multiple-input multiple-output (MIMO) based integrated voice and data service. On the basis of analytical and simulation results, the performance of the proposed scheme is assessed for a Rayleigh fading environment. Finally, the results demonstrated that the MIMO based system is suitable for integrate voice and data traffic with different requirements and specification.
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