Adaptive modulation and coding for broadcast DVB-H systems

Broadcasting live digital TV to a small battery-powered handheld device is very challenging. One of the evolving technologies to provide such services is DVB-H (Digital Video Broadcasting over Handheld). Wireless channels constitute a fast varying environment that is hostile to reliable communications. Adaptive Modulation and Coding (AMC) is one of the most promising mechanisms to cope with the dynamic fading of wireless channels. However, the broadcast nature of DVB-H systems restricts the use of AMC as the transmitter must adapt to the user experiencing the worst channel. This would constitute a penalty to other users experiencing good channels. In this paper, a novel framework for AMC is proposed for broadcast DVB-H systems. The transmitted frames are arranged such that higher modulation symbols are transmitted followed by lower modulation symbols. Each group of symbols having the same modulation technique are arranged such that higher code rates (i.e. weaker codes) are transmitted first and then incremental symbols (constituting stronger codes) are transmitted afterwards. The proposed framework is then deployed as a power saving mechanism since power consumption has always been a crucial challenge for handheld devices. The proposed adaptive receiver adjusts its modulation and coding configuration to receive and detect the minimal amount of bits that guarantee a target Bit Error Rate (BER) performance. This is shown to result in significant potential for saving of reception and processing powers (up to 71.875%). Numerical analysis for the power saving potential and BER performance of the proposed scheme is performed for flat Rayleigh fading channel. Simulation results for the operation of DVB-H under the proposed scheme in a Typical Urban 6-paths (TU6) channel are presented. Finally, the effect of adaptation rate (i.e. how often the modulation and coding are allowed to change) on power saving potential is investigated.