Planning method of CDMA wireless network

I. Understanding the specific situation on the ground

CDMA Network Wireless planning should make full use of the local population, economy, geography and other basic information, at the same time to reflect the local characteristics, such as reflecting the imbalance of the economic development of a certain characteristics, reflecting a certain key township is very developed, the gap between urban and rural areas of small characteristics. CDMA Network wireless planning should not only achieve better economic benefits, but also consider some social benefits, in order to achieve economic and social benefits on the basis of the above information, the double harvest. In the early stage of network planning, the following information needs to be fully investigated.

1. Investigation of population, distribution, floating population, economic conditions, including economic aggregates, per capita income, distribution of enterprises and so on, on the one hand, these information to provide network planning a scientific construction scale; On the other hand, network planning should fully embody the characteristics of these factors, so that the planned network conforms to the local reality and adapt to them. such as the distribution of the base station and population, economic distribution, so that the network planning with the actual local adaptation, to achieve a reasonable proportion, distribution of science, hierarchical, focused.

2. Understand the geographical topography of the state, is the plains, mountains, lakes or islands. Wireless coverage in CDMA networks is closely related to terrain, such as mountains and plains different terrain on the wireless coverage is very large, mountainous areas due to the block, generally speaking, base station coverage is small, and in the plains, coastal areas, such as the area, base station coverage is very large, in the wireless planning to fully consider the impact of various terrain.

3. Learn about important traffic routes, famous tourist attractions information. Because of the large flow of people in these areas, there is a great impact on the brand of the entire network, which needs special attention in planning. The main traffic lines include Urban Subway, railway, Expressway, National Road line, provincial Road line and other important traffic lines. This information must be investigated clearly prior to the wireless planning and should be considered during planning. (Computer science)

II. utilization of existing network resources

For a completely new CDMA network, although not related to the original network optimization, adjustment, but generally speaking, there are existing mobile networks for reference. So, in this case, CDMA network wireless planning, we should carefully refer to other existing networks (including GSM and CDMA) wireless coverage of the status quo, careful analysis, fully absorb the experience and lessons of the network, and as a CDMA wireless planning of the accurate reference model to greatly improve the accuracy of wireless planning.

For an extended CDMA network wireless programming, it is necessary to test and analyze the existing network comprehensively, and on this basis, propose the optimization and adjustment scheme. In addition to the modification of network management data, wireless optimization mainly includes the following aspects in the engineering hardware.

1. Relocation of the base station. The main point is to adjust some unreasonable base station to give full play to the function of the base station and achieve the coverage target. If a base station antenna is in front of a tall building seriously blocked, a base station antenna hanging high, resulting in serious coverage and pilot-frequency pollution, and so on to consider the relocation base station.

2. Antenna hanging height adjustment, antenna model replacement, antenna azimuth, pitch angle adjustment. If a base station antenna hanging high up or down, will not be charged to the whole antenna replaced with the tilt of the electric antenna, will be the antenna into directional antennas and so on, through the adjustment and replacement of the antenna, control base station wireless coverage area, achieve coverage purposes.

The completion of the above optimization, adjustment so that the current network of resources have been better use, play the potential, but also for the expansion of the CDMA network Wireless planning provides accurate information, so that wireless planning more scientific and accurate. In fact, many of the real network optimization, adjustment planning is often in conjunction with the expansion of wireless planning, together with implementation.

Three, a variety of ways to carry out CDMA network wireless planning

At present, the wireless planning for CDMA networks, the most basic and most important is the base station equipment, it should be said that in the CDMA network wireless planning, the most important thing is to consider the use of Base station equipment, this is no doubt. But at the same time, with the continuous development of technology, new technologies, new products and new means are emerging, in addition to repeater (including wireless and optical), there are various forms of micro-base station, remote module base station, in addition to the indoor distribution system (including the tunnel distribution system), the use of ultra long distance coverage technology, The use of the power amplifier of the base station, the use of the overhead amplifier, the negative pitch angle of the antenna and so on. The details are as follows:

1. Use of micro-base stations and remote modular base stations. CDMA Micro-base station is the same as the micro-cellular base station of GSM, compared with the base station, its price is lower, generally speaking, the volume is smaller and the capacity is less. This kind of micro-base station is generally suitable for areas with relatively small traffic volume and small growth potential, such as rural areas and some transportation routes. The remote module base station is a part of the base station, the RF part is pulled from the optical fiber to 10 kilometers to dozens of kilometers far, this is very similar to the optical fiber repeater, but the fiber repeater can not increase the capacity of the system, while the remote module provides capacity, which is essentially a community of the donor base station. General remote module Price is relatively cheap, easy to use, have a high price, in those traffic demand is not very high area, more suitable for use. However, since the remote module base station requires two conditions for fiber and donor base stations, its use is not very flexible, and the late changes in donor base station will directly lead to the remote module base station to do the corresponding changes, to the future network development has a certain impact, and micro-base stations do not have this limitation.

2. Use of repeater (including optical fiber and wireless). Because the price is low, the use is convenient, the repeater has occupied the place in the mobile communication system. For those areas with small capacity and small coverage, the use of repeater has high economic, and, because there is no complex network planning, repeater project implementation fast, can quickly meet the requirements of market business development. Plus the relocation is easy, repeater can be a transitional solution (in the base station before the opening of the rapid opening of the repeater station, the base station after the relocation to the new site), has a better flexibility and mobility. It should be said that in the initial stage of construction, considering a number of repeater settings is an important means to solve the problem of network coverage. Since the CDMA system is a self jamming system, the use of repeater will definitely increase the donor base station to introduce noise level, reduce system capacity, if the use of improper, will lead to the performance of donor base station drop, so the use of repeater must be cautious.

3. The use of indoor distribution systems (including tunnel distribution systems). Because of the high density of modern buildings, the construction area is very large, CDMA signal penetration loss is very large (often reached more than 20db), completely rely on outdoor base station to solve the indoor deep coverage is not realistic. In addition, there are a number of tunnels (including underground areas such as subways) also have the same problem. In order to solve the coverage of this part, we can solve the indoor distribution system, the signal source of indoor distribution system can be repeater station, micro Base station and remote module base station, and the specific selection should be determined according to the actual conditions.

4. The use of ultra long distance covering technology. Because of the unique advantages of CDMA technology, it has more advantages than other mobile communication systems in the application of ultra long distance covering technology. According to the current test situation, the CDMA base station with ultra long distance coverage technology is more than 100 kilometers. Using this technological advantage, opening this function in China's vast grasslands, deserts and long coastal waters will greatly enlarge the coverage of CDMA networks and enhance the brand image.

5. The use of power amplifiers and overhead amplifiers for base stations. The power amplifier can increase the budget of downlink, the overhead amplifier can increase the budget of the uplink, increase the coverage of the base station by increasing the budget of the upper and the downlink, while avoiding the budget imbalance of the upstream and downstream links. At present this kind of product is more, generally can improve downlink link budget 10db or so. Increasing the base station's power amplifier and tower top amplifier can effectively enlarge the coverage of the base station, especially with the combination of the ultra long distance coverage technology of the front CDMA, and can give full play to the advantages of CDMA coverage.

6. The use of antenna negative pitching angle. With the rapid development of modern city, skyscraper is rising rapidly, because of the serious pilot-frequency pollution, it is a problem to ensure that the CDMA network is unblocked in high-rise building. Of course, the problem can be solved by the indoor distribution system mentioned above, but it can also be solved by using the negative pitching angle of the antenna. Antenna negative pitching angle, namely the antenna upward "sky" radiation, by selecting a specific waveform antenna, toward a specific high-rise building, for high-rise buildings to provide dominant frequency. The method of adopting antenna negative pitching angle has many advantages, such as small implementation difficulty, less investment, convenient and flexible.

Through the full use of new technology, new products, new means, in a variety of ways to carry out CDMA network wireless planning, integrated use, reduce construction costs, speed up the construction speed.

Four, the appropriate antenna is the key to network coverage

In the CDMA network, the antenna is directly decided to cover the network, the correct and reasonable use of the antenna is the key. The mobile communication antenna includes omnidirectional antenna and directional antenna, and the main antenna index has the following several.

1. Antenna gain. Antenna gain is used to measure the antenna's ability to send and receive signals in a particular direction, which is one of the most important parameters for selecting a base station antenna. Generally speaking, the increase of gain mainly relies on reducing the half power angle of the vertical radiation-oriented, while maintaining the omni-direction radiation performance on the horizontal plane. The antenna gain is very important to the operation quality of the mobile communication system, because it determines the signal level of the cellular edge. Increasing the gain can increase the coverage of the network in a certain direction, or increase the gain margin in a certain range.

2. Antenna half power angle. Half power angle is a very important parameter commonly used in directional antenna, it refers to the antenna in the radiation map below the peak 3dB of the width of the angle (antenna radiation map is the measurement of the antenna in all directions of the signal capacity of an index, usually graphically expressed as the relationship between power intensity and angle). The vertical half power angle of the antenna is generally related to the coverage radius of the corresponding direction of the antenna. Therefore, in a certain range through the antenna verticality (pitch angle) adjustment, can achieve the goal of improving the coverage quality of the community, this is our network optimization is often used as a means