BRIEF REVIEW OF ADAPTATION AND PROTECTION STRATEGIES AT DIFFERENT LAYERS
Numerous solutions have been proposed for efficient multimedia streaming over wireless networks. Potential solutions for robust wireless multimedia transmission over error-prone networks include application-layer packetization, (rate-distortion optimized) scheduling, joint source-channel coding, error resilience, and error concealment mechanisms. An excellent review of channel-adaptive multimedia streaming research is provided in.
Transport issues for wireless (multimedia) transmission have been examined in. At the PHY and MAC layers, significant gains have been reported by adopting cross-layer optimization, such as link adaptation, channelaware scheduling, and optimal power control. However, these contributions are aimed at improving throughput or reducing power consumption without taking into consideration multimedia content and traffic characteristics. Explicit consideration of multimedia characteristics and requirements can further enhance the important advances achieved in cross-layer design at the lower layers. Possible solutions and architectures for cross-layer optimized multimedia transmission have been proposed in.
To provide QoS for multimedia applications, the IEEE 802.11 Working Group has currently defined a new supplement to the existing legacy 802.11 MAC sublayer, called IEEE 802.11e. Note that even though emerging MAC standards provide QoS support, there are no QoS guarantees for multimedia applications, and systemwide resource management is not always fair or efficient. This is due to the time-varying nature of the wireless channel and multimedia characteristics, and also the lack of cross-layer awareness of the application and MAC layers about each other.