Average external interference in cellular radio CDMA systems

An analytical and numerical evaluation by Gilhoussen et. al.(see IEEE Trans. Veh. Technol, vol.40, no.2, p.303-3121, 1991) of the capacity of a cellular radio CDMA system has been proposed. This evaluation has shown the interest of using spread spectrum techniques in the area of cellular radio systems. However, considering the computations made by Gilhoussen et. al. for the reverse link, we note the following: the calculations lead at a given moment to the evaluation of the average external interference for which a quantity is claimed only intuitively to be an upper bound. We construct a sequence of approximations for the average external interference, where the average external interference is the sequence limit. The claimed upper bound of Gilhoussen is also the first element of this sequence of approximations. We show by numerical means that the sequence is decreasing which justifies the claim of Gilhoussen.