Adaptive techniques with cross-layer design for multimedia transmission.

Abstract

Wireless communication is a rapidly growing field with many of its aspects undergoing constant enhancement. The use of cross-layer design (CLD) in current technologies has improved system performance in terms of Quality-of-Services (QoS) guarantees. While multimedia transmission is difficult to achieve, CLD is capable of incorporating techniques to achieve multimedia transmission without high complexity. Many systems have incorporated some form of adaptive transmission when using a cross-layer design approach. Various challenges must be overcome when transmitting multimedia traffic; the main challenge being that each traffic type, namely voice; image; and data, have their own transmission QoS; delay; Symbol Error Rate (SER); throughput; and jitter requirements. Recently cross-layer design has been proposed to exchange information between different layers to optimize the overall system performance. Current literature has shown that the application layer and physical layer can be used to adequately transmit multimedia over fading channels. Using Reed-Solomon coding at the application layer and Rate Adaption at the physical layer allows each media type to achieve its QoS requirement whilst being able to transmit the different media within a single packet. The following dissertation therefore strives to improve traffic through-put by introducing an unconventional rate adaption scheme and by using power adaption to achieve Symbol Error Rate (SER) QoS in multimedia transmission. Firstly, we introduce a system which modulates two separate sets of information with different modulation schemes. These two information sets are then concatenated and transmitted across the fading channel. The receiver uses a technique called Blind Detection to detect the modulation schemes used and then demodulates the information sets accordingly. The system uses an application layer that encodes each media type such that their QoS, in terms of SER, is achieved. Simulated results show an increase in spectral efficiency and the system achieves the required Symbol Error Rate constraint at lower Signal to Noise Ratio (SNR) values. The second approach involves adapting the input power to the system rather than adapting the modulation scheme. The two power adaptive schemes that are discussed are Water- Filling and Channel Inversion. Channel Inversion allows the SER requirement to be maintained for low SNR values, which is not possible with Rate Adaption. Furthermore, the system uses an application layer to encode each media type such that their QoS is achieved. Simulated results using this design show an improvement in through-put and the system achieves the SER constraint at lower SNR values.