Energy efficient cross layer time synchronisation in cognitive radio networks

Time synchronisation is a vital concern for any cognitive radio network (CRN) to perform dynamic spectrum management. Each cognitive radio (CR) node has to be environment-aware and self-adaptive and must have the ability to switch between multiple modulation schemes and frequencies. Achieving same notion of time within these CR nodes is essential to fulfil the requirements for simultaneous quiet periods for spectrum sensing. Current application layer time synchronisation protocols require multiple timestamp exchanges to estimate skew between the clocks of CRN nodes. The proposed symbol timing recovery method already estimates the skew of hardware clock at the physical layer and uses it for skew correction of application layer clock of each node. The heart of application layer clock is the hardware clock and hence application layer clock skew will be same as of physical layer and can be corrected from symbol timing recovery process, so one timestamp is enough to synchronise two CRN nodes. This conserves the energy utilised by application layer protocol and makes a CRN energy efficient and can achieve time synchronisation in short span.