Balance planning of coverage and capacity of the h

2022-07-30
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Balanced planning of WCDMA system coverage and capacity

wcdma system is a self interference system with the same frequency, which is quite different from GSM. There are also great differences in the planning and development of green technology between the two. The capacity and coverage of GSM system can be planned separately, while the coverage and capacity of WCDMA system are mutually restricted, which determines the method of balanced planning of coverage and capacity in WCDMA system

1. Capacity and coverage of WCDMA system

wcdma system is a self-interference system. The signal of each mobile station is an interference signal to other mobile stations. This interference mainly comes from two parts: the interference of other users in the cell and the interference of users in other cells

the interference level of a cell is closely related to the number of mobile stations. The more mobile stations that can be accessed, the larger the cell capacity and the greater the signal interference. This restriction brings difficulties to network planning

1. Cell load and noise increase

in WCDMA system, with the increase of users, the noise of the cell also increases, and the receiving sensitivity of the base station decreases. As a result, the cell coverage is reduced, forming the so-called breathing effect. Figure 1 illustrates the relationship between cell load and coverage in a certain wireless propagation environment. It can be seen from the figure that when the cell load reaches 50%, the interference increases by 3dB and the coverage decreases to 84% under no-load

2. Service rate and processing gain

wcdma system is the system that the spread spectrum system won the "most innovative enterprise award", and the spread spectrum gain will be generated in the process of spread spectrum and de spread. The higher the service rate, the smaller the processing gain, the larger the CIR required for demodulation, and the smaller the coverage. High rate services are often distributed near the base station, while low rate services can be accessed at a distance from the base station

3. Relationship between capacity and coverage Figure 2 shows the relationship between coverage and capacity of WCDMA macro cells at 144kbit/s. When the cell load increases, due to the increase of interference, the maximum path loss allowed by the cell decreases, that is, the coverage of the cell decreases. When the cell load is relatively low, the uplink coverage radius of the cell is smaller than the downlink coverage radius. At this time, the coverage and capacity of the system are limited by the uplink. With the increase of the load, the interference increases, and the coverage decreases in the uplink direction. In the downlink direction, the coverage decreases faster due to power sharing, so that when the load reaches a certain level, the uplink coverage radius of the cell is larger than the downlink coverage radius, At this time, the coverage and capacity of the system are limited by the downlink

II. Balanced planning of coverage and capacity

wcdma system coverage and capacity are two inseparable key factors. When planning WCDMA wireless network, both capacity and coverage should be considered to meet the requirements of network coverage and network capacity. Figure 3 shows an approach to coverage and capacity balancing planning

in this figure, as the network load increases, the interference increases, the cell coverage decreases, and the number of base stations required increases; On the other hand, the increase of load increases the traffic that a single cell can carry and reduces the number of base stations required. Thus, under an appropriate load L, the number of base stations required to meet coverage is equal to the number of base stations required to meet capacity, that is, the intersection point (L, n) of the two curves in the figure is shown. If N base stations are built in this area, the coverage of the cell will be large when the initial load is less than l, which can meet the demand for coverage and capacity. However, in the later stage, when the network carries a load greater than l, the coverage will shrink due to respiratory effect

it is generally believed that WCDMA has the following two planning methods

1. Low load and small capacity network planning

this method uses the number of base stations that can just meet the coverage and capacity requirements, that is, the intersection of the two curves referred to in Figure 3. Generally, the network planned by this method can carry a low load. When users increase, the cell exceeds the design load and there is a coverage hole. At this time, it is necessary to increase the base to continue to participate in the distilled water station. Of course, other capacity expansion methods without changing the network topology (such as adding a second carrier) are also possible, but due to the low network design load, this will cause a waste of resources

2. High load and large capacity network planning

for WCDMA networks, when the uplink load exceeds 50% or the downlink load exceeds 75%, we consider it an unstable system. During planning, only coverage requirements can be considered to implement planning under this load. In this way, the network can not only meet the coverage, but also meet the maximum uplink load demand of 50% and the maximum downlink load demand of 75%. In this case, when the network load reaches the involved index, other network expansion schemes (such as adding a second carrier) can be considered instead of adding a base station. However, at the initial stage of network operation, the system design load is too large, which will cause a waste of resources

in network design, the location of the base station is generally determined through system simulation to ensure the overall performance. Adding base stations to such a network and changing the network topology can easily increase the interference level of the whole system if the station location is not properly selected, which is unfavorable for WCDMA, a system sensitive to interference. However, it is also unreasonable to plan a large capacity network at the initial stage of construction. In the actual planning and design, the planning method to be adopted should be reasonably selected according to the investment. This paper believes that operators should plan a network with high load and large capacity, so as to avoid the problems caused by adding stations in the future in the emerging new fields such as electronic information, biomedicine, energy conservation and emission reduction, environmental protection and intelligent transportation, and lay a solid foundation for excellent network quality. If for the consideration of investment, the method of one-step planning and step-by-step construction can be adopted, Considering the current and future demand for capacity growth, network construction and base station deployment are carried out in stages and sub regions, but some high traffic and high-value areas can be built in one step. (end)

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