(Solved): 2. It is proposed to build a cellular system for data communication based on the CDMA. Specifically ...

2. It is proposed to build a cellular system for data communication based on the CDMA. Specifically, the system with a maximum vocoder rate of $9.6\mathrm{Kbps}$ and a spreading ratio of $?=128$ will be modified by reducing the bit time sufficiently to provide $28.8\mathrm{Kbps}$ data services. The only proposed change to the system parameters is the change of the bit rate. (a) What is the spreading ratio for the proposed data system? 1 (b) Without considering voice activity, the current voice system can support $K_v$ voice users. Because the data services require a lower BER, the required $E_b/N_0$ for this proposed data system is $4\mathrm{dB}$ greater than the required for the current voice system. What is the approximate number of users that can be supported by the data-oriented system (i.e., $K_d$ )? (c) In the proposed data system, active users will be transmitting at $28.8\mathrm{Kbps}$ continuously in time (i.e., no bursty traffic). If the effects of voice activity are considered, will this reduce or increase the above estimate of $K_d$ ? (d) Based on these rough calculations (excluding voice activity effects), how much should a service provider charge for a data user relative to a voice user? How does this price ratio compare to the ratio of data rates?