Virtual layering of GSM wireless network
1. Disadvantages of the GSM wireless network single-layer structure The single-layer wireless network distribution structure refers to a wireless network in which the base station in the network provides coverage to the service area only once.
This network distribution structure has many disadvantages that cannot be overcome by itself, mainly in the following aspects:
(1) There are few network slacking methods and poor capabilities to effectively distribute burst traffic. The single-layer network slacking method is based on the setting of cell parameters and distributes part of the traffic to neighboring base stations. Due to the location of burst traffic The reasons for geographic location (when the location of the burst traffic is close to the base station and the neighboring cell cannot cover it, it cannot help to shunt) and the affordability of the neighboring cell (the neighboring cell can only help shunt when there is a rich idle channel), this A single method cannot completely solve the problem of traffic diversion.
(2) After the base station fails, coverage blind areas will occur. In order to avoid co-channel interference and adjacent-channel interference, the single-layer wireless network structure can only achieve cross coverage at the edge of the cell, while the other parts of the cell cannot cross cover. Therefore, when a certain sector equipment In the event of a failure, a blind coverage area will be generated.
(3) It is difficult for mobile phone users to communicate in high-rise buildings. Co-frequency adjacent-frequency interference is serious in high-rise buildings. The indoor antenna distribution system usually used can solve the communication problems of some hotels, office buildings and other public places. Coverage, so the problem of difficult communication for mobile phone users cannot be solved in ordinary high-rise houses and general high-rise buildings without indoor antenna distribution systems.
(4) A large increase in high-rise buildings, easily forming coverage dead ends in the urban area. As the network scale expands, the frequency reuse degree increases, the service radius of the community continues to shrink, and the antenna height decreases accordingly, while the large increase in high-rise buildings will directly block The transmission of radio waves in the community has caused obstacles in some areas to block shadows.
Forming coverage dead ends.
2 GSM wireless network structure layering The wireless network structure layering refers to the establishment of a second layer wireless network based on the existing single-layer wireless network to provide secondary coverage to the service area. The original network uses a low antenna position to absorb ground and low-level space activities; the upper network selects a high antenna position to absorb production space traffic and fast transmission traffic, while acting as a secure backup of the underlying network. When the traffic of a certain base station in the bottom network is saturated, it can offload the related services to the relevant base stations in the upper network, thereby reducing the possibility of base station blocking. When the base station of the bottom layer network is obstructed, the base station of the upper layer network will automatically replace the related base station with obstacles to provide services without causing traffic loss. By providing three-dimensional spatial coverage, the communication problem of mobile phone users in high-rise buildings is solved. Due to the higher position of the antenna, the upper layer of the layered network can propagate the radio wave downward at a larger angle, and the chance of being blocked by the obstacle is reduced, thereby improving the coverage of the shadow area in the urban area. By adjusting the access relationship between the upper and lower layers of the network, the layered network can achieve the purpose of balancing network traffic. At the same time, the layered network construction also provides a means of capacity expansion for urban areas where the base station density is saturated and new base stations cannot be built.
The conventional wireless network structure layering is a physical layering, which does not occupy the base station of the original network, but selects an appropriate location.
Reinvest in base station equipment and build new stations to form a physically independent layer. This layered approach takes a long time to build and requires a lot of investment.
It is difficult to realize in a short time, and it is not universally applicable to cities where the network scale is not particularly large and the traffic is not particularly busy.
Therefore, most cities have not yet layered their GSM network wireless structure. The following describes a virtual layering method that is different from conventional physical layering.
3 Virtual layering of GSM wireless network The specific method of virtual layering is to introduce the concept of virtual network, without adding any equipment on the basis of the original network, but selecting a number of base stations with higher antenna positions from the existing wireless network to give these stations new Frequency, increase its transmit power,
Properly adjust the antenna pitch angle to increase the coverage, and modify the handover parameters and access parameters of the relevant cell, so that some base stations physically belonging to the underlying network must not only cover the original service area, but also expand the service range for The other base stations provide secondary coverage, so that it is a base station of the upper layer network and assumes the task of the upper layer network. These virtual base stations of the upper layer network physically use the base stations of the original lower layer network, but at the network level and the tasks undertaken,
Belong to the upper layer network. Virtually establishes a switching relationship between the base stations of the upper-layer network to form a relatively independent complete network stone, and provides secondary coverage of the original network on the original network to become the original network hot backup, thereby implementing the function of the layered network.
Virtual layering does not add any equipment on the basis of the original network. The virtual layering scheme refers to the cell parameter setting of the concentric circle technology in the setting of the cell parameters, and introduces the concept of the virtual network at the network level, which has the characteristics of not adding any equipment and zero investment. By resetting the parameters of the relevant wireless cells of the original network (mainly access control parameters, cell switching parameters, and power control parameters), the second layer network can be virtualized to realize the layered network function, thereby effectively overcoming the Disadvantages. This method of virtual layering is highly flexible and easy to modify, and is a generally applicable method that adapts to the current level of network development. After the network scale has developed to a considerable extent, operators can also choose physical layering according to their needs.
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