On the Communication Performance of Precoder Matrix Index Based Physical Layer Security Schemes

Physical Layer Security is an emerging paradigm in which protocols at Layer 1 of the OSI stack are used to secure transmitted information, increasing time to establish a session among communicating parties. In this work two key-based physical layer security schemes are analyzed in detail: MIMO-OFDM Precoding Matrix Index (PMI) Based Scheme with Rotation Matrix (MOPRO) and the Private Random Precoding (PRP). The theoretical closed form expressions for the Key Bit Error Rates (Key BER) are derived for cellular environments. In addition, an extension of PRP that includes space time block coding (PRP-STBC) is proposed, which shows a 6 dB improvement in Key BER vs SINR performance. These schemes are also analyzed in the context of Rayleigh Fading and closed form expressions for the statistical Key BER are found. Further analysis of these schemes is done in the context of imperfect channel estimation, frequency selective fading, and fast time-varying channels. The maximum theoretical information transmission rate is found for all three schemes. Finally, a network planning approach based on reuse factor is proposed to take into account the newly derived statistical variation of the key BER for each scheme. This analysis and extensions point the way towards incorporating low-error rate physical layer security schemes into the next generation of cellular and IoT networks.