Use tailor-made TD-SCDMA transmission solutions
The transmission network is the basic network of the telecommunications network. In line with the principle of "transmission first", the first to bear the brunt of 3G network construction is the deployment of a transmission platform that can meet business development.
The trend of 3G network development is all-IP. High-speed and large-capacity data services are the main feature tags of 3G. Building a transmission network that carries 3G network operations is the "first mover" in the construction of the entire network. The process of 3G transmission network planning and construction is roughly as follows: 1) Combine 3G business development needs, conduct transmission technology research and determine the overall plan strategy; 2) actual mobile network planning, transmission network planning; 3) network construction implementation; 4) continuous network optimization , Expansion.
At present, how to adapt to the current and future continuous evolution of 3G and formulate an overall bearer strategy is a hot topic in the industry. Because, at present, the 3G network is still the most ATM standard in the world, including the domestic TD network built in 2007. The bearer business is still dominated by voice. However, in the future, 3G networks will gradually evolve towards IP, and mobile data services will gradually become the focus of operators' development. After the transmission network is newly opened, it usually meets the needs of recent business development. However, with the passage of time and the development of business, there will be a need for continuous optimization and expansion of the transmission network later.
1. TD's demand for transmission network
According to the development of the TD network, it can be divided into three stages: R4, R5, and R6. The different network interface requirements and base station access bandwidth requirements at each stage are as follows:
TD's demand for transmission networks
From this point of view, the transmission network access layer needs to have STM-4 capacity and support E1 and FE interfaces; the core network needs to have high-speed access and processing capabilities at GE, STM-N and even 10GE rates. The transmission network will face changes in business requirements from low-capacity, small-particle, TDM-based to high-capacity, large-particle, and all-IP. Therefore, the focus of the TD transmission solution planning is to meet the resilience of the initial network, support for future data services, and reduce the oscillations on the transmission network caused by the continuous upgrade of the TD network.
1.1, UTRAN's demand for transmission access to the aggregation network
Access point site planning requirements
Due to the large capacity of the 3G core network and the concentration of settings, the transmission backbone layer is concentrated. As can be seen from the figure below, the distance from RNC to Node B is relatively long, and the transmission from Node B to RNC requires access and aggregation of the two-layer network. The coverage radius of TD base stations is smaller than that of GSM and WCDMA, and there is little difference between the latter two when deploying stations in urban areas, but in the suburban and rural stations, there will be situations where additional stations are needed.
UTRAN's requirements for transmission access to the aggregation network
Therefore, due to limitations in coverage capabilities and planning methods, some TD base stations and 2G base stations have different addresses, and MSTP needs to be used to build a new network.
Clock transfer requirements
Both CDMA2000 and TD-SCDMA are base station synchronization systems, but the synchronization design is different. TD only has built-in GPS in the base station to achieve synchronization between the base stations. The synchronization between the base station and the RNC uses frame synchronization like WCDMA, which requires SDH to provide the clock.
Adapt to the needs of complex business environments
The access layer equipment should be able to support a variety of interfaces to cater for different needs.
1.2 CN's demand and impact on the transmission core network
Business scheduling needs
In the large local network structure, the service particles between MGWs are usually GE, and the flow and direction are both changing. Therefore, providing high-quality transmission to support the flexible scheduling of large particle data services has become an urgent need.
Convergence and protection needs of IP services
The transmission network must be able to converge and access various services from multiple directions, and protect the IP services at the 50ms level in the core / trunk network to ensure high QOS of the services.
Network management needs
With the development of the network, the scale of 3G and other networks is increasing. In addition, operators hope to achieve unified management and scheduling of the entire network and provide fast E2E services, which puts new requirements on the management capabilities of EMS.
2. TD network construction principles and recommendations
2.1, transmission network construction principles
The transmission core layer carries the CN part of the TD network, and the transmission convergence and access layer carries the UTRAN part of the TD network;
The transmission network architecture is a unified transmission platform of TDM + IP. The core network interface of the TD system is mainly high-speed POS port and GE port, and the core layer focuses on the introduction of WDM to carry large-particle services;
Deploy on the capacity to meet the service capacity of the TD network in the mid-term evolution;
Network construction is mainly new.
2.2. Transmission network recommendations
The NODE B side uses customized equipment, which can be built into the TD base station equipment. It can flexibly support the rate upgrade of 155M to 622M through software settings, and supports rich E1, FE, HDSL and other interfaces;
The core network adopts the IP OVER DWDM solution, which can support dynamic ROADM (reconfigurable OADM) + GSS (general service switching platform) to achieve arbitrary up and down and scheduling of 2.5G / 10G wavelength-level services and can directly provide sub-wavelength services such as GE / POS Flexible scheduling.
3. ZTE TD transmission solution
While providing high-quality TD-SCDMA system equipment, ZTE Corporation provides the most appropriate TD transmission bearer solution. The solution adopts a unified platform architecture and incorporates TD transmission feature functions, which not only meets the current TD network construction needs, but also adapts to mid- and long-term technological evolution and network development applications.
First of all, the MSTP solution is adopted on the UTRAN side to reduce the complexity of the transmission equipment without any improvement to the existing MSTP equipment, so that the transmission network is separated from the service network and the interface is clear. This way is very suitable for TD-SCDMA business transmission in R4 stage. The core network adopts MSTP or IP OVER DWDM scheme.
The capacity is deployed to meet the service capacity of the TD network during the mid-term evolution. Hotspot areas consider the capacity requirements after HSDPA is loaded.
Due to limitations in coverage capabilities and planning methods, some TD base stations and 2G base stations have different addresses; BBU + RRU distributed base station methods that are mostly used in dense commercial areas and Olympic venues have led to a sharp increase in bandwidth demand; some devices on the existing network do not support MSTP or use 155M system design, difficult to upgrade or expensive, etc., network construction is mainly based on new construction.
3.1. Convergence and access transmission network solutions
In the first phase [R4 phase], E1 transparently transmits Node B's ATM E1.
In the R4 phase, the wireless side of the network is based on ATM bearers and the interface is IMA E1. After the introduction of HSDPA, the bandwidth requirements increased, the interface transitioned to FE, and finally realized the wireless side of IP. The MSTP solution can continue to meet the transmission requirements of TD at different stages, and adapt to the smooth evolution and scale application of TD networks.
The transmission network transparently transmits IMA E1 of Node B and converges into a channelized STM-1 at the convergence layer to connect with RNC, reducing the interface pressure of RNC and quickly building the network.
The second stage [Stage R5], split transmission (applicable to the introduction of HSDPA version).
NODE B-side voice and data services are separately transmitted by E1 and FE. The voice service continues to use the E1 / T1 interface and uses a static circuit configuration to minimize the impact of a large number of data services on the voice service and protect the QOS of the most important services. The newly added FE completes support for high-speed data services, and uses the embedded MSTP function for bandwidth convergence and processing.
The third stage [R6 stage] fully supports packet service transmission.
The Iub interface has finally evolved to a high-speed FE interface, and the bandwidth of the base station has reached tens of Mbit / s. MSTP layer 2 switching, embedded MPLS, RPR and other technologies to achieve statistical multiplexing of bandwidth, security isolation, and ensure the corresponding QOS. Considering the possibility of constructing WiMAX high-speed wireless access in hotspot areas in the future, CWDM can be introduced at the access layer and DWDM can be introduced at the convergence layer to solve the need for high-speed access bandwidth.
Features of ZTE's MSTP system to build access and aggregation networks:
With the ability to smoothly upgrade the bandwidth, to meet the continuous increase in the bandwidth of the access / aggregation layer;
Access to the convergence layer equipment adopts STM-1 / 4, STM-4 / 16, STM-16 / 64 compatibility design. It can speed up 155M online to 622M, 622M online speed to 2.5G, 2.5G online speed to 10G, to adapt to the significant bandwidth demand of TD technology evolution and scale application;
Compatible with TDM and data processing capabilities, MSTP is powerful;
Support E1, STM-N, FE, GE and other interfaces. In addition to supporting Ethernet over SDH transparent transmission, it supports large-aggregation ratio layer 2 switching to implement statistical multiplexing of high-speed packet services after the introduction of HSDPA and improve transmission bandwidth utilization. Support embedded MPLS, RPR, after wireless access IP, business security isolation, to ensure the QOS requirements of different levels of business;
The access layer equipment is specially designed for TD base stations and highly adapts to TD access requirements;
The access layer transmission equipment is compact in size, only 1U high, has low power consumption, flexible installation, and various power access methods. It can be embedded in ZTE standard TD base station equipment.
3.2 Core transmission network solution
The TD core network equipment uses GE / STM-N interface, and the core realizes full packet switching. The WDM system is used to build the core transmission network, which not only meets the needs of broadband and IP of the TD service network, but also smoothly evolves to the subsequent stage, and finally builds an all-optical transmission network. The core network WDM construction can be divided into the following three stages:
In the first stage, the static N × 2.5G WDM system is adopted;
In the second stage, it is smoothly upgraded to N × 10G WDM system + dynamic ROADM / GSS network;
In the third stage, upgrade to a multi-dimensional dynamic WDM system + OXC all-optical cross-connect machine.
The characteristics of ZTE's WDM system to build the core transmission network:
Support transparent transmission of all services such as GE / 10GE / POS / ATM / SDH / SAN / FISCON / ESCON / FC, support 4 × STM-16 / 8 × ANY convergence, improve wavelength utilization;
Eliminate the SDH / MSTP device level, simplify the network level, greatly improve the network carrying efficiency and reduce construction costs;
ZTE's WDM system supports all optical layer protection methods, especially the unique channel sharing protection technology. In the IP OVER WDM test organized by China Mobile, the protection switching time of the 2000Km ultra-distance test is less than 20ms, which fully meets the requirements of carrier-class protection time. At the same time, compared with other optical layer protection methods, channel shared protection not only saves channel resources, saves protection boards, but also saves relay OTU, greatly reducing network construction costs;
WDM network can be upgraded to dynamic ROADM (reconfigurable OADM) + GSS (general service switching platform), complete any up and down and scheduling of 2.5G / 10G wavelength level, and can be directly to sub-wavelength services such as FC, GE, 2.5GPOS, SAN, etc. Perform access, aggregation, and crossover, support the establishment and management of sub-wavelength level crossover and end-to-end links, and achieve X-ADM to provide flexible and reliable networking solutions and perfect service aggregation and scheduling capabilities for the network;
The WDM-based bearer network can eventually evolve smoothly to OXC  all-optical network, which not only provides a solution for China Mobile's recent TD core network construction, but also guarantees the future network evolution and sustainable development.
4. Summary
ZTE tailored a transmission solution tailored for TD, using MSTP solution on the UTRAN side, IP OVER DWDM solution for the core network, adapting to both ATM and IP standards, continuing to meet the needs of TD actual network construction and smooth evolution, avoiding the late stage Business expansion caused by frequent expansion and upgrade.
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