We extended the TRACE framework to allow users to select the appropriate trade-off among energy dissipation, delay and data quality, enabling TRACE to be much more responsive to end-user requirements and adaptive as these requirements change over time. Coupled with scalable video or audio coding, this multi-rate TRACE (MR-TRACE) enables users to receive high quality video/audio with a potential delay increase. This was accomplished through the use of a non-uniform quadrature amplitude modulation (QAM) scheme to provide simultaneous transmission of both low-rate and high-rate data, as shown in the figure below.
In a broadcast channel the same transmission can lead to different information rates to different users depending on the channel capacity between the transmitter and receiver pair, which is mainly determined by the distance between them. According to coding theory, there is a certain channel capacity that limits the rate of information that can be sent through the channel. We utilize the superposed coding scheme (shown above) in a MANET multicasting scenario to provide different rates for multicast group members. This multi-rate multicasting approach enables the multicast group members to appropriately trade-off delay vs. quality while keeping energy consumption at the same level.
The figure above shows that for two different requests, different multicast branches are formed between the members and the source. These branches can be supported by MMC-TRACE without having to send two different transmissions. This is the main advantage of MMC-TRACE over single-rate multicasting.
This work was supported in part by the University of Rochester Center for Electronic Imaging Systems and in part by Harris Corporation, RF Communications Division. For further information please contact with Tolga Numanoglu.