In cognitive radio networks (CRNs), dynamic spectrum handoff requires efficient path planning to minimize the overhead of frequent channel switching. This paper proposes a polynomial-time approximation algorithm for spectrum handoff scheduling, based on an improved Traveling Salesman Problem (TSP) modeling of the channel switching sequence. A two-phase cooperative mechanism is designed to minimize frequency-hopping overhead. We rapidly generate diverse candidate channel-switching sequences using a probabilistic method guided by real-time spectrum availability distributions. We dynamically merge locally optimal sub-paths by leveraging historical channel quality data and predicted primary user... More >