A cell planning scheme along railway tracks in CDMA systems

There are many active mobile users today in trains, especially during the rush hour, hence the potential for mobile communication traffic in trains to rocket in the near future; as applications become diversified and communication tariffs becomes cheaper due to flat rate pricing. The increase in such traffic within a train will mean a mass of accessing users, moving along the railway tracks. In CDMA systems, the signal-to-noise ratio (SNR) of users in the train is greatly influenced by the fluctuation in the number of users accessing the base station. With this in mind, we propose a cell planning scheme using integer linear programming and taking account of the movement of a train containing many accessing users. The scheme minimizes the number of base stations, ensuring the SNR of a user within a target train remains equivalent to or exceeds the required SNR. Finally, simulations using the proposed scheme verify that the SNR of a user in a train for all areas calculated based on optimally-sited base stations reaches a constant value when the interference from other accessing users in a train is much larger than that of those outside the train