3G Indoor Coverage Analysis

This paper first analyzes the importance of 3G indoor coverage from the operator's point of view, and then according to the planning principle of 3G indoor coverage, considering the selection of signal source and distribution system, finally briefly introduces the construction flow of 3G indoor cover.

With the 3G pace approaching, 3G network planning in-depth, indoor coverage has become the focus of major operators.

1. The importance of 3G indoor coverage

The next step is to analyze the importance of indoor coverage.

First, with the popularity of mobile communications, the interior absorbs most of the traffic. According to DoCoMo's latest statistics, indoor venues absorb nearly 70% of the traffic, mainly office buildings, stations and families. From the current 2g/2.5g network operation experience, mobile user 60% is also distributed indoors. Second, from the use of 3G business, indoor provide a comfortable environment, waiting time is mostly spent indoors, so that indoor users prefer to use 3G rich business. So in the above several aspects, the indoor coverage for the 3G has greater importance, and in the existing network coverage has been relatively perfect situation, users will require a better network of 3G coverage, so that users will consider using 3G network. Therefore, in order to better meet the user experience and establish a good image, operators should pay enough attention to the construction of 3G indoor coverage. (Computer science)

For operators, through the construction of 3G indoor distribution, can compete for indoor traffic volume, open up new traffic volume. According to DoCoMo's statistics, the volume of traffic in the buildings covered by the interior has increased 1.43 times times. Indoor coverage can also disperse the volume of traffic in the dense area, thus reducing the pressure of the outdoor base station and reducing the number and configuration of the outdoor base station. From the network capacity, indoor coverage also reduces the outdoor system load, because of the 3G self interference characteristics, also reduces the outdoor network overall interference level, thereby improving the entire system capacity. Therefore, the indoor coverage of 3G network construction has a vital role.

2.3G Indoor Coverage Planning principles

3G system and 2G in the use of frequency bands, coding technology, and so on, so 3G indoor coverage has some new features. 3G indoor coverage to cover, capacity, quality of the unified planning, and 2G system only to consider the level of indoor strength signal to meet user access level requirements, network quality can be adjusted through the later frequency planning. Because of different business link losses, 3G system should also consider the user's business needs, according to business development forecasts for indoor coverage planning. In the indoor distribution, site planning and outdoor planning should be harmonized. 3G indoor coverage will also focus on the 2G system or PHS system and cluster system of mutual interference.

3G Indoor coverage planning should adhere to the following principles:

The first is the unified principle, including indoor and outdoor site planning, design unity, in the construction of indoor coverage to consider the impact of outdoor signals, but also to take into account the indoor coverage of the outdoor interference level of ascension.

The second is the principle of difference. Because the network construction is restricted by the investment, it is impossible to enlarge the indoor coverage blindly, and to take the customer satisfaction as the measure standard, to set up different quality goals. Some places can accept the cover blind spot situation, may in the construction strategy and the construction stage adjusts.

Third, the economic principle, for a specific building, indoor coverage solutions may have a variety of options, can not simply in pursuit of technical perfection blindly expand investment, but also can not be in order to save investment and choose unsuitable indoor coverage scheme.

3, the signal source and indoor distribution system considerations

The indoor covering system consists of two parts, the signal source and the indoor distribution system. The main signal source of 3G indoor cover system is the macro-honeycomb plus rru, micro-honeycomb, repeater station several ways. In the selection of indoor coverage system source, the need to be considered from the capacity and coverage, the selection of the following principles:

√ For low traffic density, small-scale coverage and more closed scene, the priority to use repeater as a signal source (can make full use of the capacity of the outdoor macro-base station)

√ for medium traffic density and medium coverage of the scene, the first choice of micro-honeycomb as a signal source;

√ For high traffic density and large coverage of the scene, the first choice of Acer station +RRU as a signal source (a single rru capacity and a single macro cell capacity equivalent).

In the construction of indoor distribution system, if there are 2G indoor distribution system, the shared indoor distribution system between 2g/3g should be given priority. For 3G indoor distribution system, it is a simple, effective and economical and rapid construction scheme to share with GSM, but some specific problems need to be considered.

(1) How to close the road with active equipment

At present, the coverage system has been built, the passive distribution of the working frequency band mostly covers the 800~2500mhz, no need to change. Increase 3G in the signal source part of the use of dual-frequency or multiple-frequency coupler to the signal after the road (for the downlink is closed, for the uplink is shunt) sent to the distribution system can be completed.

For large buildings, signals in the transmission and distribution process, the signal is low to a certain extent need to use the trunk amplifier to amplify the signal, then need to use a dual-frequency or multi-channel circuit to separate the signal (for the downlink is shunt, for the uplink is the road), through their respective amplifiers for signal amplification, Then the two-frequency or multiple-frequency combination of the road (for the downlink is closed, for the uplink is a shunt).

(2) Impact on the original system coverage

The effect of adding new system on the existing coverage system is mainly to reduce the transmitting power of the original system. Regardless of the 2G signal source or the trunk amplifier, the output of the new system is directly connected to the distribution system, and the output of the active device after adding a new system must be connected to the system by a dual-frequency or multiple-frequency circuit. The dual-frequency or multiple-frequency circuit has insertion loss, which reduces the effective output power of 2G active equipment. The insertion loss of a dual-frequency or multi-frequency combined device is related to the requirements of the bandwidth of the band interval, the width of the working band, and the isolation of the interface, in addition to the manufacturing process and technology.

(3) Power matching problem

In practical applications, the biggest problem of multiple systems sharing a distributed system is the power matching problem: including the output power matching of the signal source, the influence of different frequency bands ' transmission loss in the distribution system, the different requirements of the edge covering field strength, the influence of different frequency radio waves in the air loss and so on. Designers need to be based on the different requirements of operators and the actual situation of the building to consider comprehensively.

(4) Interference problem of multi-system common Distributed system

2G, PHS, 3G and WLAN share a distribution system, which will interfere with each other. Each system of active equipment in the launch of useful signals at the same time, in the working band will also produce spurious, harmonics, intermodulation and other useless signals, these signals fall into the work of other systems in the frequency band, the other system will be formed interference. Active equipment produced by the Out-of-band, harmonic, the size of the unwanted signals such as intermodulation is related to the quality of the device itself, mainly related to two factors, that is, the output of their own power (the larger the output power, the larger the output of the useless signal) and the degree of deviation from the working bandwidth (the farther away from the work bandwidth, the smaller The ability of the system to absorb external disturbances is also related to two factors, that is, the signal intensity (the greater the chance of interference is smaller) interference signal size (the smaller the interference signal level, the lower the signal interference degree).

The interference can be reduced by isolating the space of different systems and reducing the transmitting power of the jamming source. Increasing the filter at the transmitter or receiver can also reduce the interference between the systems effectively. In addition, the use of RF performance of the transmitter, receiver and later network optimization is also an effective means to reduce interference.

4.3G Indoor Cover Construction process

Finally, a brief introduction of the 3G indoor coverage of the construction process. First of all, according to the overall network construction strategy and construction objectives for 3G indoor coverage of the selection, outdoor coverage planning as a 3G indoor coverage site choice. After planning for indoor coverage, the buildings will be surveyed, including physical size, building interior structure (including distribution pattern, elevator pattern, wall partition, etc.), the use of buildings (user type, user's geographical distribution, user time distribution and user's business model and business needs), the surrounding environment of buildings ( Understand the facilities attached to the building, the construction of the surrounding Acer cellular base station, etc. Then the electromagnetic environment test and the outdoor signal evaluation are carried out to evaluate the interaction between the outdoor signal and the indoor signal, and to make the system design index and system acceptance index. The construction of a 2G indoor coverage system can be directly tested.

After the building survey and electromagnetic environment test, it is necessary to evaluate the multiple system combined road, in addition to evaluating whether the system can be combined with other factors, including investment, construction difficulty, construction period and impact on the existing network and the impact on the system performance. In the selection of signal sources, the first is the technical factors, including the building cover demand, capacity requirements, the surrounding network environment, the location of the signal source installation, but also the project implementation factors, including the requirements of the owners and construction and other factors, as well as long-term development factors, to give due consideration to the long-term business development needs of the building.

After the selection of the signal source, the design of multiple systems, integrated consideration of coverage and capacity, to meet all the requirements of the system, the original distribution system, if the introduction of 3G under normal circumstances to increase the number of antenna points to meet 3G coverage. In addition, minimize interference between systems. After detailed design, the next step for network optimization and acceptance.