隨著智慧型行動裝置以及行動網路的普及，各種應用的流量也迅速提升。其中許多應用，通訊的裝置雙方位置並不遙遠，如能夠雙方直接通訊，而不經過基地台，將可使通訊的效能更加提升。此即所謂的D2D通訊，近年來受到高度矚目，3GPP也將其列入Release 12的目標中。除了蜂巢式網路系統的授權頻寬，在許多應用情境下，使用者也可能想透過無授權頻寬進行D2D通訊。不管是哪種使用情境，通訊前裝置要能搜尋到彼此的存在，才能進行後續通訊，因此裝置搜尋成為D2D通訊中的重要議題。本文旨在探討各種情境下，不同類型的裝置搜尋機制效率，並在知名的平台完成模擬。

As intelligent mobile devices become popular, traffic of applications grows quickly today. In many of the applications, the communicating devices are in proximity. Therefore, the idea of D2D communication, which means that one device communicates directly to another device instead of communicating via eNB, has been proposed. However, before a device starts communication with the other one, they must discover the presence of each other. The above process is so-called device discovery. There are many device discovery mechanisms proposed so far, which can be classified into synchronous and asynchronous ones, having their own respective properties. Thus we implement different types of device discovery mechanisms on famous simulation platform, expecting to provide an insight among the mechanisms in series of possible situations.

[1] Lei Lei, Zhangdui Zhong, Chuang Lin and Xuemin Shen, “Operator controlled device-to-device communications in LTE-advanced networks,” Wireless Communications, IEEE, June 2012 .
[2] Ziyang Liu, Tao Peng, Hao Chen and Wenbo Wang, ” Device-to-device communication as an underlay to LTE-advanced networks,” Global Communications Conference (GLOBECOM), Dec 2012.
[3] Daniel Camps-Mur, Andres Garcia-Saavedra and Pablo Serrano, "Device to device communications with WiFi Direct: overview and experimentation," Wireless Communications, IEEE, June 2013.
[4] Jaehoon Jeong; Tian He; David Du, “3GPP LTE Traffic Offloading onto WiFi Direct,“IEEE WCNC Workshop on Mobile Interne, April 2013.
[5] Michael J. McGlynn and Steven A. Borbash, “Birthday Protocols for Low Energy Deployment and Flexible Neighbor Discovery in Ad Wireless Networks,” MobiHoc ,June 2001 .
[6] Baccelli, F., Khude, N. ; Laroia, R., Junyi Li ; Richardson, T., Shakkottai, S., Tavildar, S. and Xinzhou Wu, ” On the Design of Device-to-Device Autonomous Discovery,” Communication Systems and Networks (COMSNETS), Jan 2012.
[7] Wi-Fi Direct Optional Services Technical Specification Package v1.0
[8] Sohrabi, K., Gao, J., Ailawadhi, V. and Pottie, G.J., “Protocols for self-organization of a wireless sensor network ,“Personal Communications, IEEE, Oct 2000.
[9] Steven A. Borbash, Anthony Ephremides and Michael J. McGlynnc, “An Asynchronous Neighbor Discovery Algorithm for Wireless Sensor Networks,” Ad Hoc Networks, Volume 5, Issue 7, September 2007.