When the mobile station is in the state of this frequency soft switching

Then if there is no outside interference factors from many cell signal in the region, resulting in poor Ec / Io, coverage is not good, and this is the pilot pollution case. Ec / Io difference is generally considered as <-12dB. Consider, therefore, can be a strong guide frequency with 4 guide frequency to compare effective Rake receiver of the cell phone number of three, is generally believed that if the difference is less than 3dB is considered to be the existence of pilot pollution. In CDMA networks, pilot pollution into the pilot phase of pollution and the pilot strength of pollution. Pilot pollution we usually referred to the guidance of the frequency of intensity of pollution. The pilot phase contamination. Forward channel in the CDMA system, each sector is different short PN code to distinguish between different PN offset.
The location of the base station is very important. With the development of the city and network clouds, originally covered by high station to base station can be considered to reduce the antenna height adjust the inclination, to transmit power and other methods to reduce the coverage. If we can in strict accordance with the above proposed network construction and maintenance, it would have prevented the excessive pilot pollution problems relative to the pilot pollution problem and then solve optimization can save a lot of time and resources. With the CDMA wireless network coverage more widely, the pilot pollution phenomenon become more frequent, more and more influence on our network. Therefore, we will be in the planning and engineering design, attention to pilot the impact of pollution on the network to minimize.
When the mobile station is in the state of this frequency soft switching, you need at the same time, and several base stations to communicate, although the diversity gain can improve the call quality of the mobile station, but some negative effect on system capacity. Moreover, the mobile station dropped calls most cases, the switching process, frequent switching is bound to increase the probability of dropped calls mobile station. This case, the capacity of the system will not only reduce, and the rate of dropped calls will be increased, resulting in user complaints, while a waste of network resources. Solve the pilot pollution in general to adjust various parameters of the system. Mainly taken to reduce pollution of the pilot signal strength and enhance the useful to the pilot signal strength so that the intensity of the fourth pollution pilot frequency pollution beyond the conduction threshold, so as to eliminate the purpose of the pilot pollution.  Similarly, adjusting the inclination of the two of which sector (reducing the inclination), make it reach far to guide the frequency of the contaminated area of the pilot power improve the remaining two sectors of the Ec / Io, will naturally be a corresponding reduced. Of course, the antenna tilt adjustable range is limited.