Mobile IP Bearer Networks in Urgent Need to Be Developed
Operators are facing tremendous contradiction between network investment and operating income. The application of mobile broadband services has entered a new stage worldwide, taking up a rising percentage in mobile communications services. The deployment of various fast air interface technologies such as EV-DO and HSxPA generates huge demand for bandwidth. To better meet users' growth in size and demand for bandwidth in the future, operators need to keep expanding radio access networks (RANs). In the current tariff system, the meager revenue from data services that take up massive bandwidth is not commensurate with heavy costs required by network development and maintenance, as shown in Figure 1.
Figure 1 Traffic and revenue
RAN bearer networks over IP are the development trend of mobile access networks. At present, RAN bearer networks are built primarily on the basis of TDM/SDH, suffering from low utilization efficiency of broadband, expansion difficulty and inflexible configuration. Therefore, operators are seeking new solutions to build bearer networks oriented toward IP, to address the pressure of business development and competition. The IP bearer capability of RAN can effectively improve network performance, support a host of new services and user experiences, reduce investment in networks, and ensure mobile networks' long-term evolution and sustainable development.
IP RAN is the core of IP mobile networks, and it is of great significance to optimizing 2G network architecture and deploying 3G access networks. At present, the deployment of IP RAN has expedited significantly. According to statistics from Infonetics, the foremost consulting institution, in 2007, in the new RAN market IP takes up a market share of 15%, while TDM/SDH share falls to 17%. With the development trend of all IP, there is an urgent need for operators to build IP RAN solutions with the deep understanding of the demand for RAN now.
Demand for IP RAN Bearer Networks
At present, there is a variety of interfaces and access methods between RAN network elements (BTS/NodeB and BSC/RNC). For example, interfaces include IMA E1/TDM E1/ML-PPP E1/FE, and access methods include xDSL, optical fiber, microwave and PDH, as shown in Figure 2. Mobile service capability will rely mainly on network elements capability and communication bearing capacity of links between network units. To build excellent IP RAN bearer networks, it is necessary to consider existing mobile access networks and the future development trend of networks, and take into account the characteristics of mobile services and bearer networks.
Figure 2 Present state of mobile access networks
IP RAN clock synchronization is of great importance. Mobile systems like WCDMA based on frequency division duplex (FDD) only require frequency synchronization between nodes while those such as CDMA2000, TD-SCDMA, and WiMAX based on time division duplex (TDD) require clock synchronization, to ensure smooth switching between cells. At present, frequency synchronization is completed through terrestrial clock signals, while clock synchronization requires GPS, which entails heavy spending.
IP RAN bearer networks should be able to effectively prevent various kinds of attacks, viruses and frauds to ensure mobile networks' security and stability. At the same time, it is essential to provide connections that enjoy the quality of private lines, and provide redundancy functionality for mobile services. In the event of node and link failure, failure recovery time should meet business needs. In addition, assurance of time delay, jitters and packet loss ratio should be provided pursuant to 3GPP's specifications on different types of services, to improve user experiences.
At present, an IP RAN's primary trait that distinguishes it from a traditional access network lies in that it offers value-added services based on packet switching. It can bear integrated services, provide multiplexing bandwidth and improve resource utilization. Moreover, mobile bearer networks should be designed and deployed to accommodate future network development. In particular, it is necessary to consider convergence with soft switch networks and other networks, the impact of the introduction of IP multimedia system (IMS) on bearer networks, and demand of the system, to meet the demand of converged services in the future.
TCO is an aspect that carriers must take note in network development, especially for IP RAN with densely distributed nodes, wide coverage and complex scenario. Apart from bearer equipment, the convenience of network operation and maintenance, compatibility with existing networks, equipment replacement and investment protection in the course of evolution are factors that must be considered.
IP RAN Bearer Network Solutions
With various factors taken into account, IP RAN bearer network solutions should be based on the design concept of data communication. This leaves maximum mobile data service to IP bearer networks for routing and transmission, and achieves bandwidth sharing by dynamic data service. Tunneling technology is used for voice services, such as PWE3 and LSP, to provide premium transmission quality. Huawei has unveiled its IP RAN bearer network solution based on the Quidway® CX Metro Services Platform. The solution can both provide reliable connection for traditional services and offer strong support for value-added data services. Meanwhile, a unified control plane is used to ensure reliable protection and recovery time for various kinds of services. As the percentage taken up by IP services that require RAN keeps growing, CX-based IP RAN bearer network solutions will have more superiority.
In view of their existing networks, operators can access base stations into CX through various types of interfaces (IMA E1/TDM E1/ML-PPP E1/FE). Carrier-class ring or tree networks built by CX can carry mobile services accessed by base stations. Eventually, clock and mobile services can pass through TDM/ATM/Eth PWE3 tunnels, and access BSC or RNC through GE/STM-1 links. The solution supports clock priority and synchronization status message (SSM). Meanwhile, at key network connection points, network availability is further enhanced and clock and services are fully protected by deploying trunk, dual homing, clock SSM protocol and enhanced VRRP. A CX-based IP RAN bearer network solution is shown in Figure 3.
Figure 3 IP RAN bearer network solution
Reliable end-to-end connection: The solution utilizes the PWE3 technology to provide end-to-end dedicated line level transmission pipes for all kinds of services. OAM/Ethernet performance monitoring and RPR ring network mechanism based on MPLS and Ethernet make transport networks' operation efficient and transparent, with carrier-class protection and failure recovery. Moreover, carrier-class equipment and network security measures fully improve mobile networks' security and robustness.
Perfect clock synchronization mechanism: The solution optimizes link transmission efficiency, achieves clock synchronization with packet transport clock and synchronous Ethernet clock irrelevant to network congestion. It can meet traditional TDM and 2G/3G mobile access networks' rigid requirements, save GPS expenditure drastically, and ensure that each end user gets fine quality of service.
Born for the future: The solution is compatible with existing services and networks. While ensuring multi-service features and network scalability, it totally conforms to the trend of fixed-mobile convergence (FMC), saving costs for mobile operators. Being homogeneous with core networks, IP RAN bearer networks further cut operation and maintenance costs and offers operators a solution with low total cost of ownership (TCO), paving the way for future development.
Moreover, the solution features powerful QoS mechanism, which meets the differentiated needs of various services in mobile networks, and excellent industrial design, all tailor-made for IP RAN bearer networks. With its own advantages, the CX-based IP RAN solution has been successfully put into commercial use by Shanxi Telecom in China and Thailand's True Move, gaining customers' full recognition. Having made great R&D efforts toward carrier-class product series CX MAN service platforms, Huawei will keep extending its product lineups to build ever-perfect IP RAN bearer networks for the customers.
