CDMA demodulation by satellite in heavy co-channel interference using matrix pencil

Global mobile communications necessarily requires satellites to supplement or replace terrestrial cellular systems. These systems continue to rely on code division multiple accesses (CDMA) to allow multiple users to share the same bandwidth. Detection of CDMA signals from space, however, is a challenging problem because of excessive co-channel interference, which is due to code reuse in the large coverage area of the satellite antenna footprint on the ground. In this paper, an efficient, robust method of separating these co-channel users based on angle-of-arrival (AoA) using a simple multiple element linear array and the matrix pencil (MP) technique is applied. This new technique overcomes the limitations of its predecessors such as MUSIC and joint MLSE, which cannot detect signals in heavy co-channel interference. It is shown that using this technique enables rapid joint demodulation of up to 20 co-channel users employing the same code, thereby enabling one satellite beam to cover the same area formerly covered by 20 base stations (up to 1000 users per beam with a code length of N=64). The technique will enable future global mobile communications by satellite as well as enhance commercial and military communications systems employing CDMA