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As the most important technology of the 21st century wireless communication network, the third generation mobile communication technology provides mobile users with more than 2Mbps high speed through advanced wireless technology while realizing mobile network packetization, improving network service realization capability and value-added space. Access enables wireless users to experience the same broadband experience as fixed network broadband users. It is this kind of packetization and high-speed access that makes 3G's requirements for bearer networks, especially transport networks, very different from 2G. Therefore, it is of great significance to construct a transport network adapted to 3G by using appropriate technologies.
At the same time, after nearly 10 years of development, optical transmission technology has far exceeded the concept of SDH circuit crossover and WDM wavelength connection. MSTP proposed in 2000 and intelligent optical network widely used after 2003 have become the hottest light at present. network technology. MSTP is targeted for transport services, and intelligent optical networks are network-oriented, providing the most complete transport solution for next-generation networks.
MSTP is the cornerstone of 3G optical transmission network
The 3G mobile network is oriented towards packet in bearer mode. The core network of WCDMA in R4, R5 and R6 versions is IP-based. The voice network and packet domain of the core network are completely separated. The voice, data and image are realized by the cooperation of MSC Server and IP router. IP bearer and exchange of services such as multimedia. As the capacity of the router continues to increase and the port rate continues to increase, the granulation of the core network connection service becomes more and more obvious. The base station access network is limited to the unified transmission of real-time services such as voice and data. All 3G systems temporarily select ATMs in the bearer technology to ensure higher QoS and end-to-end management capabilities, but with IP technology. Continuous improvement, base station access IP will become an inevitable trend.
The IP network and large granularity of the core network make its transmission network tend to develop in the direction of IP+ wavelength, which directly promotes the transfer of long-distance trunk transmission network from SDH+DWDM to Router+WDM. At the same time, because of the changes in transmission services, the trend of long-distance DWDM multi-service is becoming more and more obvious. Even many industry experts believe that long-distance DWDM network MSTP has become one of the core research of long-distance transmission technology.
Similarly, the base station access network bearer also faces a trend of evolving from ATM bearers to IP bearers. Although the 3G wireless network can quickly open services on the existing transmission network, the ATM cell or IP packet is converted into a 2M circuit to provide the base station 2M access capability, but from the development point of view, the service bearer is costly and efficient. Low will change with the MSTP transformation of the transport network. MSTP is derived from SDH and provides 2M services. It provides ATM cell switching, ATM VP-Ring, Ethernet transparent transmission, aggregation, and switching by adding functional modules. It becomes the main form of 3G base station access.
MSTP is also generated to adapt to different access methods. Regardless of the domestic operators or international mobile operators, the change in frequency selection will lead to a large number of new access points in the 3G base station construction. For these new access points, MSTP can provide different access. Means adapt to the corresponding access resources: MSTP can provide DDN and SHDSL interfaces, provide twisted pair access of N×64Kbps and FE1, up to 3.5Km, and solve suburban counties with cable access resources without fiber resources. MSTP can cooperate with optical Modem and PON technologies to make base station access more diverse. MSTP can also be combined with FSO and microwave to provide wireless access without fiber and cable. Access coverage of the base station.
It can be seen from the transmission requirements of the 3G core network and the base station access network that the common MSTP of the DWDM long-distance network and the SDH local network is the cornerstone for constructing the future 3G mobile optical transmission network.
Conditions for the development of 3G optical transmission networks
As a next-generation mobile service network, 3G mobile network has different characteristics from 2G in terms of user distribution and base station traffic, including dynamic and bursty, and higher requirements for transmission network. . As one of the most important technologies in the next generation optical network, intelligent optical network integrates dynamic routing control organically on the basis of circuit connection and non-blocking cross processing, making the transmission network from static to dynamic, and the development of 3G mobile network. Provide a strong guarantee.
(1) The number of mobile terminal users supported by the 3G single base station is more than 2G. If the base station is cascaded, it is assumed that 3 to 4 base stations and one Hub base station are cascaded, and the number of configured users connected to the Hub base station will reach 500~. 800, in this case, the maximum allowed 20,000 to 30,000 3G users to be active in the coverage of the same base station or the same group of base stations cascaded, this feature directly puts higher requirements on the security of the base station access transmission. Intelligent optical network technology can provide multi-path service recovery in the form of MESH (grid) network while providing ring network protection, ensuring the most complete security considerations for base station access.
(2) The download bandwidth of 3G single-user services far exceeds 16Kbps of 2G mobile voice. For each 3G wireless subscriber, the available bandwidth can range from 12.2Kbps of voice to 14.4Mbps provided by HSDPA. You can also experience high-speed wireless services such as video calls, online games, Internet TV, and network downloads. With the wide-scale implementation of 3G services, static circuits obviously cannot meet the burst requirements of bandwidth. The emergence of intelligent optical networks transforms the services provided by optical transmission networks from statically connected circuits to dynamic connected circuits, better adapting to changes in base station access bandwidth caused by user traffic adjustments.
(3) The expansion of the download bandwidth space that 3G users can control will also lead to another change, that is, the bandwidth distribution of the network transport layer is more and more uneven, the regional traffic of economic concentration is rapidly expanding, and the traffic of remote areas is growing slowly. In fact, this feature is also a feature of 2G wireless networks, but because 2G users have little demand for traffic, for 2G base station access, adding or reducing a small number of circuits on the local network SDH ring can achieve regulation. However, the access bandwidth of the 3G base station is very different. The intelligent optical network provides a MESH (grid) transmission networking mode with uneven bandwidth distribution, and the corresponding optical line capacity is configured according to the regional access bandwidth, so that the transmission efficiency is greatly improved.
(4) As a new network, the 3G network must be gradually built. The base station access layer transmission can be rapidly and cost-effectively extended to meet the needs of adding base stations at any time. In the traditional SDH networking, the ring network extension needs to open the ring plus nodes or add a new ring network. Although it has little effect on the end access transmission, it will cause a large number of network adjustments for the transmission backbone network above the aggregation layer. The stability and security of the entire mobile transport network is threatened. The intelligent optical network adopts the MESH structure on the group network, which can expand the network structure "plug and play" and maintain the stability of the original network structure.
(5) With the continuous improvement of maintenance requirements, the shrinking of core switching nodes to a few points is the trend of network development, and this feature of 3G networks is more obvious. In a local network, the base station controller RNC and the core switching equipment are likely to be distributed in one or two exchanges, which reduces the maintenance complexity of the core network, but at the same time makes the circuit path of the base station access longer, so that the transmission circuit The demand for cross-network layer scheduling has increased. The intelligent optical network realizes the non-blocking of network scheduling by improving the scheduling capability of the node equipment, and provides end-to-end circuit establishment and maintenance capabilities, which greatly reduces the maintenance difficulty of the 3G transmission network.
In general, when the 3G network is mainly used to provide voice services and small-capacity data access, the NG characteristics of the transmission network requirements are not obvious. The existing transmission network can provide corresponding circuits to achieve base station access. However, with the extensive development of 3G services, the dynamic and flexible requirements of the transmission network are becoming more and more intense, and the intelligent optical network will become an important condition for the development of 3G transmission networks.
3G transmission network solution
The next generation of service networks require the next generation of transmission networks. The combination of intelligent optical network and MSTP realizes the “soft and hard combination†of software-based control plane and hardware-based multi-service transmission platform to jointly provide a 3G mobile network with a timely transmission solution.
In the 3G network, the core network bearer IP is an important feature. Between the long-distance trunk network and the metro switching center related to the 3G core network, IP Router+WDM provides sufficient bandwidth, routing and switching capabilities for 3G. In terms of service security, the recovery of dual-homed services of the IP Router and the wavelength protection of the WDM network can provide sufficient guarantee for the service security of the core network. The emergence of future wavelength scheduling technologies such as GEADM, ROADM, and OTN provides end-to-end wavelength services for IP Router connections and becomes an important part of future 3G core network transmission solutions.
The UTRAN of the 3G network covers the entire local network, and the local network backbone scheduling layer, aggregation layer, and access layer layered structure composed of the intelligent optical network MESH network dynamically expands the transmission network structure according to the gradual construction of the 3G base station, and expands according to the growth of the base station bandwidth. The transmission network capacity ensures the stability, security, efficiency and dynamic development of the base station access network. As a hardware platform, MSTP provides rich ATM and IP packet processing capabilities to meet the needs of 3G network base station access services. The combination of MSTP and intelligent optical network constitutes the transmission scheme of the 3G base station access network.
Prospects for the future development of 3G transmission networks
It is not only in the field of 3G mobile networks, but the development of optical network technology to multi-service, intelligent, and wavelength scheduling has become an indisputable fact. Even multi-service, intelligent optical network technology has been applied in a large number of service networks. It can be expected that in various service networks including 3G in the future, the transmission network will be more suitable for various needs of the service network. Let us look forward to the bright future of 3G transmission network and prepare for the adoption of optical network technology in the construction of 3G transmission network.
3G optical transport network technology
Summary of 3G and Optical Network Technology Development