| The mobile communication technology has been developing very fast during last 10 years. Because of the advantage of high efficiency of frequency spectrum, the TDD mode standard which formulated by China has been the major mobile communication standard in 3GPP, and TDD-LTE has deployed globally as one of 4G technologies. As a time division duplexing technology, the TDD system needs very precise timing for normally operating. Till now, base station times from GPS directly, but its disadvantages include high cost, critical implement request, low security, etc. It becomes so urgent that mobile operator requests transform from timing by GPS to timing by carrier network, which will introduce new needs for timing synchronization on traditional carrier network. IEEE 1588 protocol can provide timing synchronization precision within several nano seconds, which can fulfill TELECOM's timing reqirement. The IP transformation of Traditional TELECOM service becomes the global trend, so the PTN networks based on packet switching technology developed so fast on the market. PTN is well compatible with IEEE1588 protocol, but it is limited to deploy in access or aggregation layer of Metropolitan Area Network(MAN) only, because of its traffic capacity. OTN is an asynchronous carrier network technology, it normally deploys at the core layer of MAN, but it meets lots of difficulties to support IEEE1588 protocol. So how to realize the high precise timing synchronization on OTN network is very important.Synchronization is an important concept in telecommunication. The paper analyzes the detail of sync requirement from different telecom applications, introduces the popular sync technology and its theory, emphasizes the importance of IEEE1588 protocol. According to OTN's characteristics, the paper focuses on an OTN's timing sync solution of IEEE1588 over OSC. Firstly, the paper analyzes OTN architecture and OSC processing mechanism, studies the realization possibility from system point of view and puts forward a hardware solution. Then, the paper provides a solution to improve key components' characters related to temperature to enhance timing sync precision and stability during the operation temperature range. Last but not least, the paper states the research on timing sync precision influence factors from clock distribution chain in network, as well as noise resources and noise accumulation.Sync precision becomes to be the keypoint of high precision timng synchronization solution in OTN. The paper does research on below aspects about the keypoint. Firstly, the paper provides a total solution of 1588 over OSC, which can realizes timing synchronization in carrier network. Due to OSC's management and monitoring basic function in OTN, it is necessary to modify OSC solution for 1588 timing message transmission, not only by software but also by hardware. The paper brings forth a solution that realizes the clock frequency synchronization by upgrading OSC to support synchronization Ethernet, decreases the time error by time stamping close to physical media, centralizes synchronizaion processing by create a new timing card. They contribute to improve synchronizaion precision. Secondly, the paper studies synchronizaion stability impact by temperature varation, proposes use OCXO to decrease the time drift when clock node lose its reference requency, provides a compesation solution to increase 1PPS timing signal's phase stability. Finally, the paper does research on synchronization precision influence by noise accumulation when timing message through a several clock nodes, analyzes time error components, provides a reference network model, caculates the noise margin allcation. The outcome can be the guidence to improve synchronization precison in future. |
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