Link adaptive multimedia encoding in wireless networks: A survey of theory and approaches

The bandwidth in wireless networks is usually shared by a number of wireless nodes. The channel capacity depends on the number of accessing nodes, time, environmental conditions and location of nodes. Due to varying channel conditions, several issues are observed in the transmission of real time multimedia. The existing research on multimedia streaming can be classified into adaptation techniques at the Physical and MAC layer, cross layered architecture, application layer coding techniques and frames scheduling. The adaptation techniques use various metrics such as signal to noise ratio (SNR), Bit Error Rate (BER) for link adaptation and available bandwidth estimation to adapt source coding rate at application level. Moreover, there exist certain network layer parameters such as packet delay, packet losses and jitter to achieve the required QoS for multimedia traffic. The paper has discussed the existing protocols which have significantly contributed in supporting multimedia traffic in wireless networks. In addition, a comparative analysis is presented to observe the performance, limitations and future prospects of research in this domain.