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Journal of Information Science and Engineering, Vol. 32 No. 6, pp. 1679-1695 (November 2016)

An Efficient Terminal Selection Method for Multi-Hop Synchronization in Direct Communication Networks*

1Department of Computer Science Korea Advanced Institute of Science and Technology
Daejeon, 305-701 Korea
2School of Computer Science and Engineering
Pusan National University
Busan, 609-735 Korea
3Department of Computer Science
Kyonggi University
Suwon, 443-760 Korea
E-mail: {blee; ngkim}

In direct communication, in order to deliver synchronization information to mobile terminals outside the coverage area of the base station, some terminals should propagate the synchronization signal through the synchronization channel. In general, a mobile terminal transmits a synchronization signal based on the received synchronization signal. If the received signal strength is below the propagation threshold, the mobile terminal sends a synchronization signal to extend the coverage of the direct communication net-work. Therefore, the propagation threshold value is closely related to the performance of direct communication networks. If the threshold value is too low, only a minimal number of terminals transmit synchronization information. Thus, the coverage of that direction communication network is limited. On the other hand, if the threshold value is too high, most terminals will transmit synchronization messages, triggering collisions. However, it is difficult to find the optimal propagation threshold value over the entire direct commu-nication network. Therefore, we propose a heuristic method for finding the most efficient threshold value after declaring the decision variables. The proposed method minimizes the probability of collisions between the mobile terminals°¶ signals on the synchronization channel. By comparing our simulation results with the numerical ones, we show the va-lidity of the proposed synchronization method.

Keywords: synchronization, collision, direct communication, PPDR, IEEE 802.16n

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Received June 22, 2015; revised October 11, 2015; second revised February 24, 2016 accepted June 3, 2016.
Communicated by Ce-Kuen. Shieh.
+ Corresponding authors: Namgi Kim, Yoon-Ho Choi
* This work was supported by basic science research program through national research foundation Korea (NRF) funded by the ministry of science, ICT and future planning (NRF-2015R1D1A1A01057888); and by R&D Pro-gram (S2357639) funded by the Small and Medium Business Administration (SMBA, Korea).