Gpon's technical features are in the two layer reference to the ITU-T definition of GFP (Generic Framing Procedure, Universal framing Procedures) technology, Extended Support GEM (General Encapsulation Methods) package format, Any type and any rate of business after reorganization by PON transmission, and GFM frame header contains a frame length indicator byte, can be used for variable-length packet delivery, improve the transmission efficiency, so it can be simpler, more versatile and efficient support of the entire business. The details are as follows:
(1) unprecedented high bandwidth. The GPON rate is as high as 2.5 Gbps, providing enough bandwidth to meet the growing demand for high-bandwidth networks in the future, while asymmetric features are more adaptable to the broadband data Service market.
(2) Full service access for QoS assurance. GPON is capable of hosting ATM beacons and/or gem frames at the same time, providing a good service rating, support for QoS Assurance, and full service access. At present, ATM bearer voice, PDH, Ethernet and other business technology has been very mature; The use of gems to carry a variety of user business technology has been unanimously recognized, has begun to widely used and developed. Gpon can transfer any type and any rate of business in its original format and then through PON. So how is the Gpon data package implemented? ONU receives uplink ETH, TDM, or SDH data from the Uni (user Network Interface, subscriber network Interface), and ONU encapsulates the uplink data as a gem frame and sent to Olt. Olt encapsulates gem frames as ETH, TDM, or SDH data, which are sent through the upper-hand ports. Similar treatment in the downward direction.
(3) Support TDM business well. TDM business is mapped to gem frames, and the TDM business can be directly supported by the Gpon TC frame frame length of 125μs. The TDM business can also be mapped to ATM beacons, and provides real-time transmission with QoS guarantees.
(4) Simple and efficient adaptation package. Adopt gem to realize simple and efficient encapsulation of multi service flow. In APON, all the multiple business flows (voice, data traffic) are required to be transformed into ATM beacons. As we all know, the 5-byte ATM header is more than 10% of the bandwidth loss compared to 48 bytes of data, especially for long packet packets, the packaging process is complex and inefficient. In EPON, although the direct hosting of Ethernet frames, the implementation process is simple, but only consider the $number line code has 20% of bandwidth waste, coupled with the Ethernet frame package and overhead, EPON bandwidth utilization ratio gpon low of about 30%. At the same time, in the transmission TDM business, it is necessary to map it through the Protocol transformation to Ethernet frame, there is no uniform standard for this technology. GPON's gem provides a flexible frame structure package, supports the encapsulation of fixed-length and indefinite-length frames, realizes common mapping for a variety of services, does not require protocol conversion, realizes simple process, low overhead, and achieves a maximum efficiency of 94%, and realizes the full utilization of bandwidth resources.