of up to 16 tvcs are possible basically more channel bandwidth means higher data rate and smaller data packet sizes having a small data frame is important for a csma system thus we suggest that 802 11 of should support variable channel bandwidth for contiguous available tvcs using multiple tvcs together can also improve the spectrum efficiency because there is no need to have guard bands between tvcs the spectrum opportunities in tvws can be classified into two categories which are contiguous and non contiguous in the first case the available tvcs are contiguous for example four contiguous tvcs are available in fig2 a ideally the larger the channel bandwidth the higher the data rate so from this point of view a system should use as many available tvcs as possible obviously a practical system cannot support an infinite number of channel bandwidths we propose that 802 11 of systems support a single tvc and 2 3 4 8 16 contiguous tvcs in urban areas 2 3 and 4 contiguous tvcs can be available with high probability the 8 and 16 tvc cases are provided mainly for rural areas in the second case the available tvcs are non contiguous when the available tvcs are not contiguous but close to each other we still want to use them together to increase data rate and have small packet sizes the csma based systems compete for the medium in the time domain different systems see each other as long as the tvcs used are overlapped the transmission delay performance of the whole system is improved.