新式的電信網路主參考信號源; New Approaches to Primary Reference Source in Telecommunications Networks

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Title:	新式的電信網路主參考信號源;New Approaches to Primary Reference Source in Telecommunications Networks
Authors:	施江霖;Jiang-Lin Shi
Contributors:	電機工程研究所
Keywords:	NFS;GPS;PRS;SONET;SDH
Date:	2002-05-24
Issue Date:	2009-09-22 11:36:53 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	由於高速網路時代的來臨，今日電信網路對於高準確度的主參考信號源(PRS)的要求比以往更為殷切。在第三章完成一個藉由GPS共同觀測技術同步於國家標準頻率系統的主參考信號源，這是一項非常強而有力的時間與頻率傳送方式。依據ITU-T G.811規定，一個電信主參考信號源的頻率準確度必需優於1×10-11，在這種狀況下，對於64 kbit/s的通路，70天不能大於一個信號滑失(slip)。但為達到相同的滑失率，高速網路其準確度必定少於1×10-13，例如SDH或SONET。這對於現存的大部分網路架構是無法符合的。本文所完成的電信主參考信號源追溯國家頻率標準，準確度達到5×10-14以上。本系統是以低成本，其性能追溯國家頻率標準為5×10-14。而這頻率性能顯示，電信主參考源的頻率偏移優於5×10-14 ±1×10-14，而在這種情形下，幾乎沒有犧牲到頻率穩定度。第四章，提出利用光纖系統傳送時間及頻率。這系統利用SONET/SDH的 overhead比次(bytes)框架來傳送定時信號。這系統在溫度控制下利用折返(loop back)方式完成測試。試驗結果顯示不管使用5米或35公里長的光纖，其短期時間穩定度達到5 ps，長期頻率穩定度優於1×10-14。而且在35公里的折返實驗，其遲延變化少於1.4 ns。在這篇論文，提出一個電信主參考源以較便宜的價錢同步到國家標準頻率的高準確度，以大幅提升電信網路性能；同時利用光纖電纜傳送高準確度的時間及頻率，以提供高速網路的需求。以上兩項均得到非常良好的結果。 With the introduction of high-speed networks, today’s telecommunications networks require a more accurate primary reference source (PRS) than conventional ones. A PRS synchronized to the national frequency standard (NFS) based on the technique of global positioning system (GPS) common view, a powerful means for time and frequency transfer, is proposed in chapter 3. According to ITU-T G.811 [2], the frequency accuracy of a PRS should be better than . At this order, the network is allowed to have not greater than one slip in 70 days for any 64 kbit/s channel. To achieve the same slip rate, the accuracy should be less than for a high-speed network such as synchronous digital network (SONET) or synchronous digital hierarchy (SDH). This is not achievable for most existing schemes [3], [4]. The proposed PRS achieves performance comparable to the NFS, which is at present accurate to better than . Our method achieves performance comparable to the NFS, which has frequency accuracy of the order up to , with a lower cost. Performance results indicate that the frequency offset of the PRS is improved to almost without sacrificing the stability. Indicate that a PRS with frequency offset can be improved to . An optical system for time and frequency transfer via optical fibers, presented in chapter 4. The system used a number of unused overhead bytes of the SONET/SDH frame, in transmitting a timing signal. The system completed the loop-back test in temperature-controlled conditions. Experimental results showed that short-term time stability can be achieved at 5 ps, and long-term frequency stability is better than , regardless of whether the loop-back is a 5 meter or 35 km long optical fiber. Moreover, the delay variation in the 35 km loop-back test was less than 1.4 ns. In this dissertation, a PRS synchronized to the NFS with high performance and lower cost, used optical fiber to transmitted high precise time and frequency are proposed. All got good results.
Appears in Collections:	[Graduate Institute of Electrical Engineering] Electronic Thesis & Dissertation

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