The strategy of constructing WCDMA wireless network

The construction of 3G mobile network is a complex project, considering all kinds of factors, also need to deal with the emerging problems, so technology and experience are equally important. Alcatel Shanghai Bell by virtue of its strong in the field of telecommunications research and development strength and accumulated many years of experience in the field, will be in the future 3G network construction to assist operators to complete the construction goals, and jointly create a new phase of mobile communications.

River and Bridge

1. The river

The main problem of river cover is because of the open terrain and the spread of the water surface, it is very easy to make the base station signal on both sides of the cross over, so that the formation of the district cover and interfere with each other. In addition, because of its single transmission environment, the effective reflection signal can not make up the cover blind zone formed by the antenna flap, causing the overlay confusion and increasing interference, so the system can't reach the design capacity. Therefore, the Yangtze River area may be a pilot-frequency pollution of the region, for the same frequency UMTS system, when the UMTS mobile phone active set to 6, the river on both sides of the base station signal more and more cover and interfere with the situation is not too much, but when the strong signal number of more than 6 will cause pilot pollution.

Alcatel Shanghai Bell suggested that in the beginning of the construction network can consider the use of wide-wave flap antenna to prevent possible cover holes, and strictly control the base station on both sides of the antenna height, direction, dip, pilot power and other parameters, to prevent the area cover too far. In addition, should also be tested on both sides of the river, especially difficult to control the more areas covered, mobile phone switching is very easy to drop the area, you can and the surrounding community unified consideration, to increase the setting of adjacent areas to ensure that the switch. (Computer science)

2. The bridge

As the terminal is constantly switching between multiple communities, the large number of motor vehicles on the bridge, fast fading phenomenon is obvious, power control can not achieve the desired effect, but will cause acceptance of the signal easily disturbed. Due to the presence of specular reflection on the surface of the river, the signal is strong and the dispersion is very strong, which causes some interference in the bridge's signal is particularly powerful but poor quality.

You can generally resolve this by:

* Remove unreasonable switching relationship, straighten out the switching order.

* Turn off the power control along the line.

* Reduce the maximum transmit power.

* To provide a good service community for the bridge by adjusting height, dip angle, azimuth angle and switching relationship.

* Can be built at both ends of the dedicated community or on the bridge to increase micro-honeycomb, to reduce interference in other communities.

Subways and tunnels

The subway and tunnel signal basically spreads along the straight line, is easy to be occluded to form the shadow, its reflection signal is absorbed quickly, the subway, the tunnel inside is narrow, the signal incidence angle is small, the signal is uneven, the local signal declines fast, therefore the ordinary city, the highway coverage system is difficult to satisfy the In addition, Subway, tunnel transmission environment is special, the surrounding environment is complex, so need special solution to cover. At the same time, it should be noted that the capacity of the subway is higher, its covering means should be different from the ordinary tunnel.

1. Subway Project: Leakage cable +repeater Scheme

Because of the large number of Metro users, the impact of a large, service quality is particularly important. The underground part of the subway can use the leaking cable, the distribution system of the leakage cable is used in the subway. The leakage cable cover the signal evenly, the beam transverse transmission, can make up the tunnel wireless transmission insufficiency flaw, is suitable specially for the city subway system. Considering that the subway system is underground and that it forms an independent system on the cover and the ground, it is entirely possible to classify all the stations in the subway as one RNC. This treatment to the network management, maintenance has brought great convenience, can be the subway network as a separate network to manage. But the leakage cable scheme is more expensive than the traditional "micro-honeycomb + indoor Distribution" solution.

2. General Tunnel Programme

In the city, there may be a river tunnel, crossing the street Tunnel this special environment, the main solution for the micro-honeycomb, leakage cables, repeater stations. For tunnels with long length and large curvature, it is recommended to use distributed antennas or leakage cables to resolve them. This paper introduces another way: the use of micro-cell (or Acer station) as a signal source, along the direction of the track to establish distribution system, subsection amplification to ensure the transmission of signals.

For the shorter tunnel, because the traffic density is not large, can be used "micro-cell/repeater + coupler + indoor distribution antenna" way to solve. If the distance is slightly longer, you can add a two-way amplifier.

For long tunnels, the scheme of "Repeater + Photoelectric conversion module + power Amplifier" can be adopted. Taking the optical fiber as the carrier, the optical signal is converted by the Photoelectric conversion module, and the signal is amplified and output by amplifying module. If a power amplifier is used, the noise coefficient of the device needs to be considered, such as the bidirectional amplifier T-BDA which the Alcatel chooses for the tunnel, and the noise coefficient is 6dB when the maximum gain of the system is.

Intensive residential Area

Generally speaking, the residential area of the building arrangement comparison rules. For the building arrangement rules of residential area coverage, it is recommended that the antenna installed in the wall outside the walls of the corner, so that the main lobe of the antenna directly to the space between the building, to avoid the main lobe of the antenna in the vicinity of the wall and generate reflection, resulting in unnecessary interference.

Also can use the way of the power divider, so that a plot has two coverage direction, but the corresponding splitter will bring 3dB loss. For the irregular arrangement of the residential area, the antenna can be installed in the problem area of a building on the wall, is opposite the building wall, using its reflected signal to provide coverage, antenna hanging high about two floors and three stories high. For different types of residential areas need to have different considerations, combined with the importance of coverage area, considering input-output ratio to use the corresponding equipment to solve the coverage problem.