Applied Physical Layer Orthogonal frequency division multiplexing Encryption

Future telecommunication products promise increased data rates and signal quality, enabling the convergence of services including voice, data and video on wireless platforms. The majority of these fourth generation systems (4G) systems, including Long Term Evolution (4G mobile systems), employ Orthogonal Frequency Division Multiplexing (OFDM) modulation because of its robustness to a number of transmission physical impairments. For the success of these systems, a key, user-oriented requirement is security in the wireless transmission. Security in current wireless systems is achieved by cryptographic algorithms that are employed at upper layers of the network.

Encryption is a discipline that has undergone a rapid and extensive growth in the last 20 years. Commonly encryption algorithms rely on – unproven – assumptions about the difficulty in solving certain mathematical problems. An increasing number of widespread encryption algorithms were recently compromised and proved inefficient for secure wireless transmission. Such issues prohibit the expansion of services such as secure mobile banking. On the other hand, it has been rigorously demonstrated that encryption at the physical layer (signal level) can offer unconditional security. Physical layer encryption approaches are unbreakable, invoking perfect secrecy in the wireless transmission of data of any kind.

The principal aim of this research program is to investigate theoretical, technical and practical aspects of a novel approach for physical layer encryption for systems that use OFDM modulation, termed Masked-OFDM (MOFDM). As a result, the proposed project is relevant to 4G wireless systems. The ultimate objective of this is work is to address theoretical, technical and practical aspects of the MOFDM systems. The means by which these aims will be achieved can be grouped into three main themes:

  1. Building on previous work, a thorough analysis of the signal properties and possible variations of MOFDM systems will be performed.
  2. Using knowledge gained from the first activity, the development of realistic system scenarios will be investigated. The main issue to be addressed is the reduction of power consumption and therefore the prolongation of the device battery duration.
  3. Finally, the proposal of practical designs for 4G systems is envisaged.