WCDMA indoor coverage: both internal and external repairs improve user awareness

During the construction of the WCDMA indoor coverage system, we must also consider coordinated development with the outdoor coverage system to achieve "both internal and external repair ".

The data service is the main service carried by the WCDMA network. The performance of data upload and download directly affects the user experience. At present, more than 70% of data services occur indoors. Therefore, it is essential for China Unicom to provide excellent WCDMA network coverage for end users in an indoor environment.

Increasing customer value is the key

In the 3G era, bandwidth is no longer a "bottleneck". How to provide customers with better user experience is the focus of operators. China Unicom's WCDMA network is currently in the fast network construction stage and has completed network infrastructure construction in more than 200 cities. In order to provide users with a good user experience and enhance the value of China Unicom's 3G brand, a high level of WCDMA indoor coverage is essential.

"Like other 3G networks, China Unicom's biggest challenge in WCDMA network optimization is site selection and signal entry. In this regard, China Unicom also has a solution, that is, to improve the user experience by improving the coverage of indoor coverage and hotspot areas. Most of the data traffic is still regular and concentrated in densely populated areas. In this case, we only need to improve indoor network coverage and introduce some new technical equipment to meet users' needs ." Said Zhang Zhongping, deputy general manager of China Unicom's network construction department.

Good Indoor Coverage can also increase the capacity of the WCDMA system, helping operators quickly expand their customer base. "The network characteristics of WCDMA determine that the downlink power and uplink interference will affect the system capacity. A good indoor system can release the downlink power of the outdoor community to share the capacity of the outdoor network. Good Indoor and Outdoor coverage can reduce the uplink interference of the system and increase the system capacity. These two points are critical to the WCDMA system. They are the biggest difference between the WCDMA indoor network and the GSM Indoor network. They also determine that the WCDMA and GSM Indoor network designs are essentially different ." Zhao junna, Technical Manager of Ericsson wireless indoor coverage, told the China Electronics Daily reporter.

Because of its high frequency, WCDMA is more difficult to deploy in-room coverage than 2 GB. The feeder loss and Space Loss of WCDMA in the indoor environment are relatively large, so many power losses are on the transmission path. Currently, most fiber-optic base stations are used in the industry to reduce trunk transmission losses. In some cases, active devices are used as an extension of coverage, but additional system noise is introduced, reducing system capacity is a major problem encountered in the current WCDMA indoor coverage.

Because the WCDMA network has been deployed on a large scale around the world, many manufacturers have accumulated experience in Designing Indoor Coverage systems. From a technical point of view, the WCDMA indoor distribution system is composed of a signal source and a distribution system. Different combinations of the two form a variety of Indoor Coverage solutions.

Wang Youwei, Chief Engineer of zte umts (General Mobile Communication System) network optimization, told the China Electronics Daily reporter: "in terms of the source, macro base station, micro cell, RRU (Wireless Remote Unit) can be used ); in terms of distribution systems, passive distribution systems, Active distribution systems, and leakage cable distribution systems can be used. In the construction of the WCDMA Indoor Distribution System, the RRU + passive distribution system is currently the mainstream deployment method. In this way, the system has good performance and convenient maintenance. In the project, the optical fiber is used as the transmission medium, reducing the line loss, so that the RRU has the same coverage capability as the GSM source. The transformation of the 2G/3G shared road is simple, and the construction progress is accelerated ."

Integrated indoor and outdoor deployment to improve quality

To build a high-quality WCDMA network, it is necessary to achieve perfect continuous coverage of indoor and outdoor networks. To this end, we must also consider coordinated development with the outdoor coverage system during the construction of the WCDMA indoor coverage system to achieve "both internal and external repair ".

"The indoor system has never been independent from the entire network. From the perspective of WCDMA capacity characteristics, it is important to achieve good indoor network performance through coordinated coverage of indoor and outdoor networks. Factors such as the building environment and surrounding WCDMA signal coverage should be taken into account in the WCDMA interior coverage design. On the contrary, during outdoor network planning, some key buildings should be considered together to include indoor systems in the scope of the whole network specification, which will bring great benefits to the improvement of network performance." Said Zhao junna.

Wang Youwei also said that the construction of the WCDMA indoor coverage system can be reasonably planned and designed to form indoor and outdoor collaborative coverage, reduce interference, and effectively ensure the user experience, ensure that users can enjoy continuous service coverage anytime and anywhere. Through the introduction of new residential areas, indoor coverage effectively shares the outdoor network traffic load and increases the System user capacity. WCDMA indoor coverage sites are discrete. If there is no outdoor network, indoor coverage sites are like isolated sites. Therefore, indoor coverage must be integrated with outdoor coverage to form a unity.

At present, there are still some difficulties in implementing indoor and outdoor coordinated coverage of WCDMA.

The first is signal interference and leakage. Similar to the mutual influence between base stations in an outdoor network, indoor and outdoor networks also have an impact on signals. Therefore, interference between indoor and outdoor communities and indoor communities must be controlled to ensure normal operation of indoor and outdoor networks.

Second, problems with the common indoor distribution system. In terms of engineering and cost, the 2G/3G indoor distribution system is the first choice for the construction of WCDMA indoor coverage. Due to the high frequency of 3G, it brings high losses, therefore, you must select a reasonable 3G source networking mode to complete 3G indoor coverage.

The last is the smooth transition. It is necessary to ensure the Business Continuity of users in various indoor and outdoor environments, that is, the smooth transition between multi-carrier, between indoor and outdoor, indoor elevators, and between floors must be ensured. Because it involves many different scenarios, the key point is to provide reasonable switching planning and design solutions based on the scenario.

2G/3G Common indoor system is the first choice

Currently, China Unicom has a complete GSM network and a large indoor coverage system, while the new WCDMA network is still in the initial stage of construction, and the indoor coverage system is very weak. In addition, the current owners are extremely sensitive to base station radiation, making it difficult to create a WCDMA indoor coverage system. To this end, the WCDMA and GSM Indoor systems have become the first choice for WCDMA indoor coverage.

Wang Youwei told reporters: "the biggest difficulty in building an indoor coverage system is to obtain the construction permit of the property. Therefore, for any site that has been built with 2G indoor coverage, the 2G/3G indoor coverage system became the first solution. Even if you create an indoor distribution system, you should first consider the sharing of an indoor distribution antenna system with 2G/3G ."

In order to smoothly achieve 2G/3G indoor coverage, system isolation must be ensured and the allowable loss of various systems must be roughly balanced. First, a good combination of indicators should be adopted to achieve 2G/3G system isolation. Second, the RRU transmitted by optical fiber is used as the source. On the Combination of 2G/3G signals, it can effectively compensate for the high loss caused by high-frequency WCDMA segments and ensure the coverage of WCDMA indoor signals. Finally, it ensures the support of 2G system passive devices for 3G systems, the "multi-antenna and small power" antenna Layout mode is used to ensure elevator coverage and transformation, so that the transformed 3G system can form a uniform indoor signal coverage, and effectively control the outdoor signal leakage.

1. Key elements in the early stage of WCDMA System Construction Planning
2. Analysis on evolution and deployment of WCDMA networks