A single-letter characterization is provided for the capacity region of finite-state multiple access channels, when the channel state is a Markov process, the transmitters have access to delayed state information, and channel state information is available at the receiver. The delays of the channel state information are assumed to be asymmetric at the transmitters. We apply the result to derive power control strategies to maximize the capacity region for finite-state addtive Gaussian multiple access channels.

Abstract-A single-letter characterization is provided for the capacity region of finite-state multiple access channels. The channel state is a Markov process, the transmitters have access to delayed state information, and channel state information is available at the receiver. The delays of the channel state information are assumed to be asymmetric at the transmitters. We apply the result to obtain the capacity region for a finite-state Gaussian MAC, and for a finite-state multiple-access fading channel. We derive power control strategies that maximize the capacity region for these channels.

Let (S 1,i , S 2,i ) ∼ i.i.d p(s 1 , s 2 ), i = 1, 2, . . . be a memoryless correlated partial side information sequence. In this work we study channel coding and source coding problems, where the encoder is informed with the encoder's side information (ESI, S 1 ) and the decoder is informed with the decoder's side information (DSI, S 2 ), and additionally, either the encoder or the decoder is also informed with a version of the other's side information with a rate limited toR s . We derive six special cases of channel coding and source coding problems and we provide a single-letter characterization for the capacity or the rate distortion function for the different cases. We then present a duality between the channel capacity and the rate distortion for the cases we study.

DVB-S2 is the most accepted standard in the satellite market today. Recently, a new extension, DVB-S2X was approved. It was designed to cope with increased demand introduced by HDTV and data services. However, DVB-S2X is not backward compatible with DVB-S2, and that poses a problem for manufacturers and operators. In this paper we propose using lower roll-off factor (ROF) for the DVB-S2 waveform, considering that reduced ROF contributes significantly to the spectral efficiency obtained by DVB-S2X in typical scenarios. That will keep it backward compatible, with slight degradation, but without forcing the market to implement full scale replacement of deployed equipment. In this paper we study the expected degradation in performance, as well as implementation issues that might be encountered. We demonstrate, by measurements using standard equipment, that this degradation is small and that the proposed migration path from DVB-S2 to a more advanced technology is a viable solution. I. INTRODUCTIONFor satellite communication systems, the most costly and scarce resource is spectral allocation. Hence, in such a system, spectral efficiency is the most important value factor, as it determines the data capacity that can be allocated per a given amount of satellite spectral bandwidth leased to a user. The DVB-S2 satellite communication standard [1], which is more efficient than its predecessor, DVB-S, by over 30%, is currently the standard that has been adopted nearly universally by the satellite industry for both broadcast and data communication purposes.Between 50 and 70 million satellite set-top boxes (STBs) are shipped each year. The market trend favors DVB-S2 enabled STBs that support High Definition TV. In the coming years, they are expected to become the majority of STBs shipped. This trend will impose even greater demands for bandwidth and spectral efficiency (SE).The newly approved extension of the standard, DVB-S2X [2] further improves spectral efficiency. However, it is not backward compatible with DVB-S2 and requires a relatively sizeable investment before it can be used.The waveform used by DVB-S2 is the root raised cosine (RRC) waveform with three roll-off factor (ROF) options: 35%, 25% and 20%. A large contributor to spectral efficiency (especially in linear multi-carrier channels) of the DVB-S2X standard stems from reduced ROF, which reduces the occupied bandwidth of the transmitted signal and allows denser packing of channels.

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