Short-range cognitive radio network: system architecture and MAC protocol for coexistence with legacy WLAN |
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Authors: | Nan Hao Sang Jo Yoo |
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Affiliation: | (1) Graduate School of Information Technology and Telecommunication, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon, 402-751, Korea |
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Abstract: | To increase possible data transmission rate and to provide non-primary user’s desired throughput in short-range communications,
in this paper we propose new cognitive radio (CR) network architecture with the coexistence with the legacy IEEE 802.11 WLAN.
The legacy WLAN ISM band channel is mostly used for common control channel for cognitive operation on the licensed bands to
manage CR devices when they join the network and to announce the utilization of the licensed band or primary system appearance
on the current used channels. The proposed CR-WLAN MAC protocol is designed to accommodate new CR related features in the
proposed network architecture and it has backward compatibility to the legacy WLAN system: (1) Network entry procedure is
modified to inform CR users the current licensed band status and to manage CR user group separately by AP; (2) During the
operation, two types of CR beacon multicasting mechanisms are proposed, CR beacons help CR users to decide its service change
or spectrum handover and to immediately evacuate from the current used channel when primary signal is detected, (3) When the
CR user need to change the serving CR AP, not only the beacon frame body of neighbor APs but also the licensed and unlicensed
band status is delivered to CR node to search the target CR-WLAN AP fast and (4) A new type of hidden node problem is introduced
that focuses on possible signal collisions between incumbent devices and cognitive radio CR-WLAN devices, and a simple and
efficient sensing information exchange mechanism between neighbor APs is proposed. The simulation results show that the proposed
CR system can provide reliable protection to primary systems, as well as efficient utilization of given licensed spectrum
resources, in which the network throughput can be greatly enhanced. |
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