Design and implementation of a novel two-phase spectrum handoff scheme for QoS aware mobile users in cognitive radio networks

Abstract

Quality of Service (QoS) aware spectrum handoff operation is critical for Secondary Users (SUs) executing real-time applications like Voice over IP (VoIP) in Cognitive Radio Networks (CRNs). The problem is aggravated by the inclusion of occasionally mobile SUs where pre-selected target channels are often rendered insignificant during handoff under dynamic conditions. Conventional proactive and reactive schemes may underperform due to channel obsolescence issues and unacceptable handoff latency respectively while a combined approach is not yet explored under the constraints of practical applicability. In view of these challenges and enormous significance of VoIP based CRN in 5G networks, this paper proposes a practically feasible two-phase spectrum handoff methodology with I_Phase and S_Phase operating under alternate conditions. I_Phase deploys a three-level dropping decision scheme followed by a two-tier spectrum handoff policy and is motivated by an integrated approach spanning every CR operation. S_Phase incorporates user mobility and application-oriented aspects where channel drop is governed by a joint two-order Hidden Markov Model — custom Damerau–Levenshtein distance metric based policy and spectrum handoff is monitored by a novel non-cooperative TOPSIS method. These phases are assisted by two proposed prerequisite techniques namely ACT (Adaptive Call Transmission) involving CR timing parameters and VER (VoIP Early Resumption) dealing with early call resumption. Comparative analysis of QoS metrics including per-instance handoff latency, transmission duration per target channel, channel drop and call drop probabilities, etc. in analytical and simulation platforms record significant performance improvement. Novelty of this work further relies on design and execution of SU prototype with the proposed scheme in test-bed that successfully provides QoS guarantees during spectrum handoff.