Distributed radio relay for communication and control with physical-layer security in smart grid

  • Authors:

  • Terry N. Guo

  • Affiliations:

  • Tennessee Technological University

  • Venue:
  • Proceedings of the Seventh Annual Workshop on Cyber Security and Information Intelligence Research
  • Year:
  • 2011

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Abstract

Information security has become a prominent issue, and this is especially critical for communications in the smart grid. For wideband connections with substations or end users, short and medium range radio communication can offer great convenience and flexibility. However, compared to network security of wired networks, achieving wireless security is more difficult. In general confining a radio signal in a desired space is infeasible, thus wireless information leakage is a critical problem. Encryption and authentication based security techniques have been proved effective, but all of them need to consume additional radio resources. In this research a physical-layer security technique complementary to the security means implemented at upper layers is proposed and examined. It takes advantage of rich multipath environment to focus radio energy on some desired spatial spot, while achieving nulling at other spots. What makes spatial focusing and nulling possible is transmit waveform optimization based on propagation environments. In particular, radio relay is considered for outdoor wireless communication, not only due to its range extension ability, but its virtual radio mirror function. The use of radio relay makes a virtually rich multipath environment thus validates the proposed physical-layer security scheme. Using a matched filter receiver at test points, the optimization problem is actually the Quadratically Constrained Quadratic Program (QCQP) which is known as an NP-hard problem, thus the Semidefinite Program (SDP) as a relaxation technique is used to obtain suboptimal results. Physical-layer security in terms of channel gain discrimination is numerically validated using the IEEE802.15.4a outdoor NLOS outdoor channel model, considering worst-case (maximal) information leakage at the eavesdropping location.