Developing a secondary mobile network in the Palestinian GSM band using cognitive radio

In this paper, we study the feasibility of implementing a secondary overlay cognitive radio (CR) network in the primary Palestinian global system for mobile communications (GSM) 900MHz band. In particular, the existing second generation (2G) GSM mobile system is considered as the primary system (PS) whereas a fourth generation (4G) mobile system based on orthogonal frequency division multiplexing (OFDM) is suggested as an overlay secondary system (SS). The interference expression due to the SS at the PS receiver and the interference expression due to the PS at the SS receiver are firstly derived. Then, to eliminate these interferences, a pre-coding technique based on zero forcing beamforming (ZFBF) is inserted at the SS transmitter, while a post-coding is introduced at the SS receiver. To illustrate the performance of the proposed CR system, a comparative simulation study is carried-out with existing CR based on OFDM system for both the PS and SS. It is confirmed that the proposed CR system can utilize the available spectrum efficiently and limit interference levels, and consequently can improve system capacity.