Research On Cell Interleaving Strategy Based On WATM-OFDM System

Recently, there have been many studies for high speed Asynchronous Transfer Mode (ATM) technology based wireless multimedia services for future broadband multimedia personal communication. ATM cells are generally transmitted over optical channels where the error rate is very low (below 10^-8) and due mostly to random errors. In wireless networks, error rate is high (10^-3 ～10^-6), and bit errors may occur in burst due to multi-path, jamming, and fading, therefore an enhanced error control strategy must be applied to.Firstly, we research on the interleaving method of error control. Some basic principles of interleaving strategy are studied and the interleaving method that is applied to Turbo code is analyzed.Secondly, a hybrid header and data strategy is analyzed based on the ATM cell to resist the burst errors occurred in the channel, reference to the unit interleaving technique in DS3 satellite channels. The interleaving method spread the 40bits-header of every cell to rearrange ATM cell. After deinterleaving at reception, burst errors in transmission are spreaded out as isolated random errors into the data field of different cell. A comparative study of hybrid-cell, intro-cell and traditional interleaving method is analyzed by computer. We can get a low cell loss rate and select proper interleaving depth according to the different traffic type.Lastly, a WATM-OFDM transmission system is designed according to the 802.11a WLAN PHY and DVB. A WATM-OFDM transmitter is added to system, which is used to resist the errors by channel fading and Multi-path interference in wireless system and make full use of the bandwidth efficiently. The performance of every part of WATM-OFDM system is analyzed and simulated . RS coding and hybrid interleaving are used to enhance the system performance, too.