Erlang capacity of overlaid multiclass CDMA and TDMA systems

In this paper we evaluate the reverse link Erlang capacity of a multiclass CDMA and TDMA systems when they are overlaid. We consider the Poisson nature of the arrivals in both systems and an interesting variation of the Erlang loss model used in TDMA system with the additional assumption of an ordered hunt. That is, we assume that the TDMA slots are numbered 1,2,...,N_TS in a way that co-channel slots are placed at the end of the list, thus each arriving user takes the lowest-numbered idle slot. It is shown that the capacity in the overlay situation considering an ordered hunt can be significantly increased. In our analysis we obtain a capacity increase on the IS-136 system due to the CDMA2000 overlay of a factor equal to 0.58-2.8 for an outage ranging from 10.61% to 19.08% in the IS-136 system and a blocking probability, P_b=2%, in the CDMA2000 system.