Forward link capacity of overlaid multiclass CDMA systems and TDMA systems with slots reallocation on the TDMA layer

In this paper we evaluate the forward link Erlang capacity of a multiclass CDMA and TDMA systems when they are overlaid. Additionally, we propose two schemes for the overlay situation, ordered hunt and slots reallocation (reallocation control model). For the ordered hunt scheme we assume that the TDMA slots are numbered 1,2,...,N/sub TS/ in a way that co-channel slots are placed at the end of the list, and each arriving user takes the lowest-numbered idle slot, in order to reduce the TDMA interference to CDMA layer and increase the overlay capacity. In the second scheme, the co-channel slots are placed at the end of the list but with the additional assumption of slots reallocation. It means that if one slot is set free among the first m ordered busy slots, the user who occupies the m-th slot (last position) will be reallocated to the released position. The objective to the slots reallocation is to achieve the occupancy of the co-channel slots as low it is possible. In our results we obtain that the overlay situation in the forward link is possible under the proposed strategies.