Two-Hop Transmissions in Asynchronous Channel-Hopping Cognitive Radio Wireless Networks With Buffer-Aided Relays

Due to physical constraints or channel impairments, direct (one-hop) communications among secondary nodes may not be possible in cognitive-radio wireless networks (CRWNs). In this letter, the rendezvous problems of two-hop transmissions using a relay node with buffer of different sizes in channel-hopping (CH) CRWNs are studied. A two-hop rendezvous protocol operating with suitable asynchronous CH sequences is proposed. A new performance metric, maximum time-to-rendezvous-with-relay (MTTR r ), and throughput are derived for different buffer sizes. The studies find that (i) both MTTR r and throughput improve as the buffer size increases but see no further improvement beyond a certain buffer size, and (ii) the proposed two-hop rendezvous model has only slight performance penalties as compared to the conventional (one-hop) counterpart.