Addressing the Exposed Terminal Problem for Heterogeneous Coexistence in White Space

Abstract

Television white space (TVWS) spectrum consists of bands that are reserved for terrestrial television which is licensed TV broadcasting, and it is open to unlicensed secondary users under regulatory conditions. TVWS spectrum sharing approaches focus on protecting the TV bands from the interference caused by the secondary users. To access this TVWS spectrum by secondary users several wireless technologies came into picture ie., IEEE 802.22 (Wireless Regional Area Network) which has a TDM based MAC protocol and IEEE 802.11af (Super WiFi) which has a CSMA based MAC protocol. Different wireless technologies with different PHY/MAC design leads to coexist in the TVWS which faces a hidden terminal problem and exposed terminal problem. In this research work, first analyzed the throughput of 802.22 under the hidden 802.11af and the probability of accessing the channel by 802.11af under exposed 802.22 CPE transmitters. Secondly, proposed a Dynamic Reservation Period (DRP) algorithm which shows that, under exposed terminal of 802.22 CPE transmitters also a fair channel accessing exists to 802.11af and throughput of 802.22 doesn't affect by DRP. Extensive simulation work was carried out in a realistic scenario based on the available TVWS channels in a certain geographical area.