{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T01:55:08Z","timestamp":1760147708026,"version":"build-2065373602"},"reference-count":40,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2023,2,22]],"date-time":"2023-02-22T00:00:00Z","timestamp":1677024000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Defense Acquisition Program Administration(DAPA)","award":["KRIT-CT-21-030","NRF2021R1A4A1032580"],"award-info":[{"award-number":["KRIT-CT-21-030","NRF2021R1A4A1032580"]}]},{"name":"Korea Government (MSIT)","award":["KRIT-CT-21-030","NRF2021R1A4A1032580"],"award-info":[{"award-number":["KRIT-CT-21-030","NRF2021R1A4A1032580"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Time-division multiple access (TDMA)-based medium access control (MAC) protocol has been widely used for avoiding access conflicts in wireless multi-hop ad hoc networks, where the time synchronization among wireless nodes is essential. In this paper, we propose a novel time synchronization protocol for TDMA-based cooperative multi-hop wireless ad hoc networks, which are also called barrage relay networks (BRNs). The proposed time synchronization protocol is based on cooperative relay transmissions to send time synchronization messages. We also propose a network time reference (NTR) selection technique for improving the convergence time and average time error. In the proposed NTR selection technique, each node overhears the user identifier (UID) of other nodes, hop count (HC) from them to itself, and network degree, which denotes the number of 1-hop neighbor nodes. Then, the node with the minimum HC from all other nodes is selected as the NTR node. If there are multiple nodes with the minimum HC, the node with the larger degree is selected as the NTR node. To the best of our knowledge, the proposed time synchronization protocol with the NTR selection is introduced for the first time for cooperative (barrage) relay networks in this paper. Through computer simulations, we validate the proposed time synchronization protocol in terms of the average time error under various practical network scenarios. Furthermore, we also compare the performance of the proposed protocol with the conventional time synchronization methods. It is shown that the proposed protocol significantly outperforms the conventional methods in terms of the average time error and convergence time. The proposed protocol is shown to be more robust against packet loss as well.<\/jats:p>","DOI":"10.3390\/s23052447","type":"journal-article","created":{"date-parts":[[2023,2,23]],"date-time":"2023-02-23T02:01:25Z","timestamp":1677117685000},"page":"2447","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["A Time Synchronization Protocol for Barrage Relay Networks"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9332-2102","authenticated-orcid":false,"given":"Woong","family":"Son","sequence":"first","affiliation":[{"name":"Department of Electronics Engineering, Chungnam National University, Daejeon 34134, Republic of Korea"}]},{"given":"Jungwook","family":"Choi","sequence":"additional","affiliation":[{"name":"LIG Nex1, Yongin 16911, Republic of Korea"}]},{"given":"Soobum","family":"Park","sequence":"additional","affiliation":[{"name":"LIG Nex1, Yongin 16911, Republic of Korea"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5509-9202","authenticated-orcid":false,"given":"Howon","family":"Lee","sequence":"additional","affiliation":[{"name":"School of Electronic and Electrical Engineering and IITC, Hankyong National University, Anseong 17579, Republic of Korea"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4485-9592","authenticated-orcid":false,"given":"Bang Chul","family":"Jung","sequence":"additional","affiliation":[{"name":"Department of Electronics Engineering, Chungnam National University, Daejeon 34134, Republic of Korea"}]}],"member":"1968","published-online":{"date-parts":[[2023,2,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"45","DOI":"10.1109\/MNET.2004.1316761","article-title":"Time synchronization in sensor networks: A survey","volume":"18","author":"Sivrikaya","year":"2004","journal-title":"IEEE Netw."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"82","DOI":"10.1109\/MWC.2011.5714029","article-title":"Synchronization of multihop wireless sensor networks at the application layer","volume":"18","author":"Marco","year":"2011","journal-title":"IEEE Wirel. 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