2010 is the most milestone year for the TD-LTE industry. China Mobile completed the TD-LTE trial network deployment and provided high-speed wireless broadband services in the Shanghai World Expo Park. Subsequently, China Mobile will also launch a large-scale TD-LTE trial network construction project in 3 cities, all of which mark the commercial scale of TD-LTE. It is about to unfold. As the next generation wireless communication technology, TD-LTE is the core inheritance and technological innovation of TD-SCDMA standard. Therefore, there is a certain similarity in network deployment and scale commercialization. Through the cooperation with China Mobile on the Expo project and the experience of field testing, Shanghai Bell believes that there are still some difficulties in the deployment of TD-LTE network.
Protecting the network's upfront investment is a problem that operators need to consider when deploying the network. Considering the continuity of TD-LTE and TD-SCDMA, this time China Mobile explicitly requires all RAN equipment in the TD-SCDMA equipment collection. Supports smooth evolution to TD-LTE. However, from the perspective of network construction and computer room layout, Shanghai Bell believes that smooth evolution is not limited to the RAN side, but should also include ePC core network and transport layer equipment, so as to further protect investment and save space.
Nowadays, RAN devices provided by all vendors have already supported TD-LTE in hardware, and SDR technology is used to implement flexible switching between TD-SCDMA and TD-LTE through software. The BBU as a baseband processing unit has fully realized the common platform mixing support, while the RRH as the RF part also adopts the SDR design, but it is limited by the spectrum characteristics of the RF device: TD-SCDMA operates at 1.8 GHz regardless of whether it is A or B band. ~1.9GHz range, while TD-LTE basically works in the 2.3GHz band, so the transition from TD-SCDMA to LTE, RRH equipment needs to be replaced, and broadband devices are difficult to adopt because they have no commercial value, so the smooth evolution is more The ground exists in the BBU radio unit. As a 3G network that has been deployed for less than three years, TD-SCDMA is still in the period of rapid development of users. Therefore, the shared baseband processing unit of TD-LTE and TD-SCDMA is not conducive to rapidly improving the baseband processing performance of 3G networks, so the industry is still considering Smooth evolution capability from GSM to TD-LTE. As a mature 2G network, GSM has reached its peak, so it can fully utilize its huge site resources. At the same time, since TD-SCDMA and TD-LTE only share BBU devices, whether it is to insert BBU devices into GSM racks or Some GSMBBU upgrades are very convenient and smooth evolution methods. Therefore, mainstream equipment manufacturers including Shanghai Bell are vigorously promoting the technological evolution of GSM to TD-LTE.
In the foreseeable future, 2G, 3G, and LTE networks will coexist for a long time. Therefore, whether it is a transmission network or a core network, if each one is built, it will bring serious network level complexity and room space problems. Platform design is the best solution. Many vendors in the industry have introduced corresponding solutions, such as unified core network support for ePC and 3G core, META solutions at the transport level, etc., which have largely relieved operators of confusion.
Site sharing is also a necessary condition for TD-LTE network scale deployment. The choice of base station sites is increasingly difficult, and various vendors have introduced zero-occupancy solutions to make full use of existing resources and reduce the need for base station space. For example, Shanghai Bell's TD-LTE D2U BBU baseband unit is very easy to integrate into the operator's existing 19# cabinet and GSM base station. The TD-LTE eNodeB needs to adopt a flexible BBU+RRH architecture to reduce space and power constraints. The BBU can fully utilize the open space in the carrier's existing base station equipment to be installed on a standard-size rack. The RRU can be installed near the antenna. Reduce the RF loss on the mast. The effective reuse of existing assets such as cabinets, power supplies, backup batteries, RF assets, antennas, and transmissions also facilitates the deployment of the network.
LTE is a pure data network. Compared with the previous mobile communication systems, there are many differences. In the network design and planning, it is necessary to introduce some new network element devices that adapt to the broadband data network, and adopt more flexible and scalable back. It is also necessary to consider compatibility with 2G and 3G networks when transmitting technology. Therefore, the use of a unified network element device compatible with the ePC and the 3G core network is the best solution for improving the quality of the data service. By reducing the network level and implementing flexible scheduling of 3G and LTE data services within the device, the service quality can be further improved and the user satisfaction can be improved. degree. The mobile backhaul technology, which supports TDM and IP hybrid transmission capabilities, can transmit 2G, 3GTDM networks and LTEIP networks through a network, forming a long-term coexistence of multiple technologies. Recently, the mobile backhaul network deployed by NTT DoCoMo is very useful.
The last difficulty lies in the implementation and optimization of interoperability between TD-LTE and existing 2G and 3G networks, as this will affect network performance. In the initial stage of network deployment, when the TD-LTE network is limited in scale, it is necessary to interoperate with the existing network in a step-by-step manner to minimize the impact on the existing network, which requires a large amount of existing network experience. Alcatel-Lucent encountered the same problem in building an LTE network for Verizon Wireless in the United States and accumulated a lot of successful experience to help it achieve a smooth upgrade of the network.
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