Analysis and enhancement of pair-wise code assignment scheme used in Code Division Multiple Access protocol

•Two pair-wise code assignment schemes are proposed for CDMA based MAC protocol.•A co-channel secondary interference is detected in the existing code assignment schemes.•The proposed schemes deals with the minimum code requirement, spatial reuse of codes and avoidance of secondary interference.•Improves the network performance. Code Division Multiple Access, which allows multiple users to access and transmit data over wireless channel simultaneously, is implemented using different code assignment schemes including Pair-wise Code Assignment. In this paper, the existing pair-wise code assignment procedure is enhanced and a new such scheme is presented with at most ∆ codes, where ∆ is the maximum degree of a network. In addition, a co-channel interference called secondary interference that exists in the existing schemes has been addressed and an interference free pair-wise code assignment procedure is proposed with at most ∆2- c codes, where c is a constant. On simulation over different synthesized, actual and random networks, it is found that our scheme improves successful transmission rate and blocking probability by 17% and 12.5% respectively. Although the code requirement of the proposed interference free scheme is increased by 40%, it would improve the network performance. [Display omitted]