PTN: A Bearer Technology Revolution

Bearer network technologies are currently evolving in two directions: towards voice bearer networks (also called transport networks), and towards Ethernet. The former is used to transmit voice services, and is highly manageable and reliable, while the latter is the most widely used LAN technology, featuring fast and easy interconnection. The two technologies have been gradually converging due to the fact that they support and complement each other.

Because voice services have small bandwidth change yet require high reliability in the early stage, Plesiochronous Digital Hierarchy (PDH) and Synchronous Digital Hierarchy (SDH) employ “rigid pipes” to ensure high reliability management. The powerful OAM offers management channels for network protection. However, this brings some disadvantages.

All network interconnections are fulfilled by a centralized network management system, and all Point-To-Point (PTP) service connections are configured manually. Whereas network link failure accounted for in the design can be recovered through carrier-class protection switching in less than 50ms, unexpected link failure may result in service discontinuity. Moreover, when network deployment and service configuration have been completed, the occupied bandwidth cannot be changed or released due to the rigid pipes.

Ethernet supports simple and flexible interconnection, but has weak manageability and low accessibility. Therefore, protocols such as STP and RSVP were developed to ensure network reliability and connection efficiency. Without the connectionless feature of Ethernet, the MPLS router (appearing later) was designed to enhance traffic control and network protection. 

PTN leverages the advantages of transport networks, Ethernet, and MPLS routers to enable easy and efficient interconnection between users. It is a manageable and reliable bearer technology offering the bandwidth flexibility to carry multiple services. PTN equipment has the following features:

■    Powerful OAM to ensure efficient network protection and high reliability;

■    Flexible bandwidth adjustment to raise network bearing efficiency;

■    A wide variety of interfaces to support diverse Ethernet, TDM and ATM services;

■    It is low-cost and simple to implement.

The control and manageability required by telecom networks may affect network simplicity and ease of use, while flexible bandwidth change may increase the complexity in network planning and service reliability. PTN, a connection-oriented transport network technology, has been developed to solve these problems. Based on IP, it is applicable to multi-service environments and is capable of accessing, converging and transporting TDM over package services. This represents a revolutionary change in the deployment, operation, and maintenance of bearer networks.

Additionally, the explosive growth of wireless services has also driven the development of PTN technology. Flexible bandwidth control, service bandwidth assurance, and IP-based features required by wireless services have been the development trend of PTN.

Drawing on in-depth understanding of PTN technology, heavy R&D investment, and a wealth of network construction experience, ZTE has achieved outstanding performance with its PTN products.

In August 2009, ZTE announced the formal launch of its new generation IPTN bearer network solution, designed to meet the needs of IP-based services through mobile backhaul and multi-service delivery. The solution features packet kernelling, enables multi-service delivery, and provides customers with mobile backhaul and fixed/mobile convergence. It also allows customers to cut network construction, operation, and maintenance costs, helps carriers implement smooth network evolution, and fully addresses carriers’ current and future requirements for network transmission.

ZTE has been selected by three major operators in China to build PTN commercial trials in various Chinese cities. In December 2009, ZTE emerged as the biggest winner in China Mobile’s massive equipment purchases for the roll out of its next generation mobile transport network, garnering a 35% share of the revenue.

On 18 February 2010, the company announced it had signed a contract with Finland-based telecom carrier Finnet Group, becoming an exclusive supplier of a unified multi-service metro bearer solution in three Finnish cities. This marks another successful commercial application of ZTE’s PTN solution in the high-end European market. ZTE has previously implemented a PTN solution for Promonte, a subsidiary of Telenor. The Finnish project will adopt ZTE’s ZXCTN 6100 PTN solution as a means of offering traditional voice services and interconnection over Finnet’s all-IP-networks.

To date, ZTE has expanded its PTN business into many new countries, including Brazil and Montenegro, and has completed the construction and testing of PTN networks for carriers such as Telefonica and T-Mobile.