Cooperative Neighbor Discovery in Dynamic Spectrum Access Networks Zaw Htike, Thant Zin Oo, Kyi Thar and Choong Seon Hong Department of Computer Engineering, Kyung Hee University, 1 Seocheon,Giheung, Yongin, Gyeonggi, 449-701 Korea {htike,tzoo,kyithar,cshong}@khu.ac.kr Abstract In dynamic spectrum access networks, neighbor discovery is one of the most challenging tasks and, it becomes more critical when there is no centralized coordinator. Neighbor discovery in a DSA network is normally done by using a common control channel or channel hopping. Since both methods introduce their own drawbacks, in this paper, we propose a cooperative neighbor discovery mechanism without using channel hopping techniques or control channel. In this mechanism, neighboring secondary users collaboratively involve in neighbor discovery process of a pair of users and, thus it can provide relatively small delay. 1. Introduction Dynamic spectrum access (DSA) or cognitive radio technology is one of the most promising wireless technologies. In DSA networks, secondary users (SUs) access the licensed spectrum in an opportunistic manner without causing any interference with primary users’ (PUs) transmission. Normally, SUs sense the free channels or idle portions of a channel and access the channel [1]. Assume that there are  number of channels, = {  ,  ,…,  } and n number of secondary users  = {  ,   ,…,  } in a DSA network. The availability of channel is changing dynamically in frequency, space and time; thus, SUs may operate on different channels independently at any given time. Nonetheless, if a pair of SUs wishes to communicate with each other, they need to operate on the same channel at the same time. Imagine that an SU (     ) wants to communicate with a neighbor SU which is currently dwelling on a different channel (     ), how could the SUs find its neighbor for communication? Neighbor discovery in a DSA network can be achieved by using a common control channel (CCC) [2]. However, this method is not reliable since the CCC can be unavailable at any time because of PUs. Another famous method is using channel hopping (CH), but this mechanism suffers long channel access delay [3, 4]. In this paper, we propose a cooperative neighbor discovery mechanism without using CCC or CH mechanisms. 2. Cooperative Neighbor discovery We assume that network type is ad hoc without a centralized coordinator and n number of SUs are randomly distributed on the available channels. Every SU in the network is equipped with a single transceiver. SUs are within transmission range of each other, i.e., there is no hidden terminal, and SUs dwell only on PU- free channels. All message transmissions follow the principle of the Distributed Coordination Function (DCF) of IEEE 802.11[5]. When an SU (source) needs to communicate with one of its neighbor, it chooses one of the available channels,   , and it will broadcast the neighbor discovery message (NDM). The NDM includes the destination’s ID, the host channel information and the source ID. If the destination SU currently resides on   and receives the NDM, it can simply reply the neighbor discovery acknowledgement (ND-ACK) message and the neighbor discovery has been accomplished between these two SUs. The SU then continue 2014년 동계학술발표회 논문집