Chapter1 Network Planning Overview

Wireless Network Planning

Table of contents

Table of contents Chapter 1 Network Planning Overview ......................................................................................2 1.1 Network Planning Flow.....................................................................................................2 1.2 Network Pre-planning .......................................................................................................4 1.2.1 Outline of the Network Pre-planning.......................................................................4 1.2.2 Pre-planning Foundation........................................................................................5 1.2.3 Pre-planning Process.............................................................................................6 1.2.4 Pre-planning Difficulties........................................................................................14

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Chapter 1 Network Planning Overview 1.1 Network Planning Flow The purpose of the network planning is to construct a wireless network, whose capacity and coverage area are both as large as possible and which can adapt to the network development and capacity extension in the future, at a certain cost and guaranteeing the network service quality. The network planning is a systematic engineering, which covers the whole process of the network construction, from the wireless transmission research to the antenna feeder equipment specification analysis, from the network capacity prediction to the detailed project design, from the network performance test to the adjustment and optimization of the system parameters, large as the general design idea, small as each cell parameter; the network planning is also a comprehensive technique, which requires the knowledge in multiple aspects from wired to wireless, and abundant practical experiences. The telecom providers mostly concern the service quality provided by the system, whose most important factor is the coverage area. At the same time, when the wireless frequency resource is limited, how to increase the network capacity and how to meet the requirement of the network development in the future have to be considered while designing. All of the above-mentioned problems need to be solved through the network planning, which will realize the benign balance in coverage, capacity, quality, cost and so on. See Figure 1-1, the Network Planning Flow

Figure 1-1 Network Planning Flow The first phase is traffic coverage analysis. The purpose of traffic coverage analysis is to provide the foundation for the network planning. It needs to collect the following information: cost, capacity, coverage, quality, grade of service (GoS), available frequency band, information of the increase of the system, population distribution, income distribution and the fixed telephone set subscription, etc. The second phase is emulation. The emulation is the site planning of the subscriber distribution with the help of the planning software. The purpose is to guarantee the coverage and capacity of a certain area and avoid the interference. In this phase, the 2

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Huawei Company applies the network planning software ASSET. The third phase is reconnaissance survey. Perform the field examination following the ideal station address book. Record the possible station addresses according to the different construction conditions (including power supply, transmission, electromagnetic background and land taken over, etc.). Consider the range of deviation from the ideal stations, effects on the cell splitting, economic benefit, coverage area prediction and so on. Then recommend a suitable station address plan and make sure if the electromagnetic environment around the base station is pure. The fourth phase is the system design. Set the frequency, the planning of the adjacent cell and running parameters of each cell, according to the actual base station distribution and station type. The fifth phase is installation and debugging. Following the design data, install and debug the system to make it run normally. The sixth phase is optimization. Along with the increase of subscribers, the network needs frequent optimization and adjustment. When the traffic hits a certain amount, the network needs expand the capacity; thus it returns to the phase of traffic coverage analysis.

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1.2 Network Pre-planning 1.2.1 Outline of the Network Pre-planning The pre-planning is the basic of the wireless mobile network. It reflects the systematic design level of the network planning and decides the layout of the future network. The output content of the pre-planning includes: the base station distribution, channel distribution, cell data and so on. Its major tasks are as follows： (1) Analyze the construction unit’s company’s requirements of the coverage area and the capacity. (2) Decide the position of the ideal station according to the cellular structure. You may select several key points in the area, from where you can observe with the help of a local relief map or an administration map, and mark the most dense regions of the subscribers as the addresses of the stations to be constructed at the first step. Then mark other base stations on the map according to the ideal cellular structure. (3) Analyze and decide the structure of the network and the base stations. Firstly, analyze and decide if it’s necessary to construct a Hierarchical Network according to the subscriber distribution, transmission conditions and the city development plan; and then analyze and decide to apply the omnidirectional or directional station to meet the requirement of coverage and capacity according to the different places of the area. (4) Compute the cell channel number of each base station.  Predict the traffic according to the geographic location of each base station, and look up into the ERL table to get the number of channels to be configured for each base station according to the call lost ratio index；  Estimate the type of the largest base station according to the frequency bandwidth provided by the construction unitcompany. If it cannot meet the capacity requirement of the local area, it needs to add the number of base stations following the principle of cell splitting according to the real conditions. It also needs to select the ideal station locations on the map and estimate the base station channel number again. (5) Predict the coverage area and decide the base station project data, namely perform the preliminary emulation  Select the design index: Select the minimum input power and the penetration ratio index at the coverage area edge.  Select the design parameters: antenna height (above the ground), antenna azimuth angle and gain, antenna declination angle, base station height above sea level, base station type, feeder line length and antenna feeder system loss, combining and distribution methods, transmitter output power, receiver sensitivity, base station diversity reception and diversity gains and so on.  Predict the coverage area of each base station cell according to the propagation models of different regions. Deliver the adjustment opinions for the base station address, antenna direction, declination angle, and height according to the potential blind area and weak signals. And get the project data of the real base station in the end. (6) Select the real station address and decide the station type.  Perform the field examination following the ideal station address, according to the different construction conditions (including power supply, 4

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transmission, electromagnetic background and land taken over, etc.). Record the possible station address. Then propose a suitable address scheme based on the integrating consideration of the deviation range from the ideal address, effects on the future cell splitting, economic benefit and coverage area prediction and so on.  After selecting the address, decide the real station type according to the number of the base station channel.  After decided the station type, it needs to conduct an antenna feeder configuration scheme. As to the network moving, it needs to investigate sufficiently the antenna feeder combination of the original manufacturer, the development of the planned base station capacity and the antenna combination supported by the current equipments and deliver the best combination scheme of the antenna feeder. (7) Frequency and Adjacent Cell Planning Make the frequency and adjacent cell plan according to the real base station distribution and type. (8) Cell Data Making

1.2.2 Pre-planning Foundation I. Service Area Requirements and Traffic The traffic distribution and coverage requirement of a certain area is one of the foundations of the network planning and generally provided by the construction unitcompany. In the case without clear requirements, you should carry out the field investigation and analysis, make sure which area has coverage and capacity requirements to met meet and which area has so little subscribers that it’s not economical to construct a station. You may ignore or reduce the service quality index. You should distinguish the short-term and long-term objects of the network construction. Mark these data and traffic distribution data on a geographical or a city planning map on the scale of 1/50000 or 1/200000. In the case of lacking traffic distribution data, you can mark how much percent each different area accounts for the assumed total subscriber number. Since the network construction is divided into different phases, the overall coverage and capacity requirements of an area cannot be realized from the very beginning. Generally, at the beginning of the network construction, when there are only a littlea few subscribers, the consecutive covering of the network should be focused on; in the late phase of the construction, improving network service quality is generally the objective.

II. Information of the Adjacent Network For good preparation of the local network planning, it needs to collect the information of the network constructed in the adjacent related areas (including the coverage area design and frequency design of the adjacent base stations along the dividing line.)

III. Landform and Field Object Data  Landform data: champagne, flat, hill, mountainous area and water, etc.;  Field object data: human environment, like city, urban, countryside, transport artery (including the newly built buildings, roads and scene points and so on), etc.; floor building data, like the building type, construction density distribution and ground vegetation (forest, grassland and crops, etc). The pre-planning is in the early stage of the wireless mobile network construction and the most important phase. It reflects the system design level of the network planning. 5

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The pre-planning decides the layout, quality and development space of the future network

1.2.3 Pre-planning Process I. Coverage Analysis (1) Type of the Coverage Area Different signal propagation models are applied for the areas of different types, which decides the design principle, service level and frequency re-use pattern of the wireless network of the coverage area. In order to decide the coverage area of the cell, you can divide the wireless coverage area into several types: big city, middlesized city, small town and countryside. Area type Big city

Middle-sized city

Small town Countryside

Description With dense population, developed economy, large traffic. In the center of the city, high buildings stand in great numbers, and the shopping cente is flourishing. With comparatively dense population, rather developed economy, fairly large traffic. In the center of the city, stand the dense buildings. The shopping center is rather flourishing and very promising. With a big population, promising economic development, moderate amount of traffic. In the center of the town, buildings stand rather densely. The shopping center has a certain scale and rather promising. With a population in low density, developing economy and rather low traffic.

In the connection area between the above-mentioned areas, there are various transport arteries, including: speedway, national highway, major provincial highway, railway and sea-route, common provincial highway, railway and sea-route, and so on. It also includes some roads in the mountainous areas. These areas need covering too. Generally, it is suggested to apply the Omnidirectional Coverage in the countryside on the plain and the areas with limited landform, and the Directional Coverage in the big, middle-sized and small cities and speedways. (2) Define the Field Strength of the Edge of the Coverage Area. The field strength defining of the falling edge of the service area concerns: mobile sensitivity -102dBm, quick fading protection 4dB (3dB for countryside), slow fading protection 8dB (6dB for countryside), and noise (environmental and interfering noises) protection 5dB.In the big and middle-sized cities, consideration should be taken for the indoor requirements; as to the outdoor requirement, the average insertion loss 15 dB; and plus the indoor signal improvement storage, 5dB. Generally speaking, the propagation fading of the GSM1800 signal is averagely more than that of the GSM900 signal by 8dB, the antenna gains of the GSM1800 system is averagely more than that of the GSM900 system by 3dB。Since the wireless links have up and down directions, and the coverage area is defined by the weaker direction, it needs to consider of the balance of the uplink and downlink. Before constructing an ideal network, it’s necessary to make a good power budget and keep the balance of the uplink and downlink as much as possible. (3) Define the Coverage Ratio The defining of the coverage ratio is different according to different coverage areas, and gradually improved along with the consecutive construction of the network. In China, at the beginning, the outdoor full coverage is generally realized in cities, national significant tourism areas, speedways, national roads, areas along the railways with large traffic, as for other major roads, railways and sea-routes, the network planning and construction should be performed for 90% of the object. Along 6

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with the deeper network construction and the increasing subscriber number, the requirement of the network service becomes higher and higher. At the same time of network planning according to the traffic, it needs to gradually enhance the indoor coverage construction of the significant areas (for example, government offices, press centers, airport lounge buildings, subways, top grade commercial office buildings, entertainment centers and large shopping malls. What needs to explain is that, according to the domestic regulations, the network can be accessed from 90% of the area and 99% of the time. This requirement should be enhanced in the outdoor areas of the big cities and simplified in the countryside. As to the transport arteries, different standards should be applied, and the consecutive covered blind areas should be limited according to the different artery types.

II. Network Structure Analysis While considering the layout of the base station, it needs to analyze deeply the network structure. Generally, the network can be divided by layer into high layer, middle layer and low layer station. Most of the network traffic is carried by the middle layer base station. (1) Middle Layer Station The middle layer station of the big and middle-sized cities refers to the base station, whose antenna is generally 25~30 meters high and a little higher than the average height of the buildings, and installed on the top of the buildings, and which generally covers several blocks. Most of the base stations in the small towns and countryside are middle layer stations, except of some special high layer stations constructed because of the traffic direction control or landform. On one hand, the middle layer station can efficiently apply the frequency resource (better than the high layer station), on the other hand, it can efficiently absorb the traffic (better than the low layer station). It has been carrying most of the traffic generated in the network running. Except in the countryside, the average station distance between most of the two middle layer stations ranges from 0.6 to 5km; while in the big cities, there are also some areas, whose average station distance between the middle layer stations is under 0.6km. But even in the big cities, the average station distance between middle layer stations is suggested not to be under 4km0.4Km. If more of the station distance is reduced, the buildings will affects the signal strength between each base stations more obviously, even to a degree out of control and that no suitable floor objects can be applied, thus the network service quality cannot be guaranteed; based on the experiences of the project construction and maintenance, the address selection, design and construction of the base station, network maintenance and quality control will face a very big challenge. (2) High Layer Station The high layer station in the big and middle-sized cities refers to the base station, whose antenna is generally 40 ~ 50 meters high and much higher than the average height of the buildings, and whose coverage area covers several middle layer base stations. Since the high layer station cannot make full use of the frequency resource, it should only be considered of and constructed, or changed from the original base stations, in big cities and some special middle-sized cities with many high buildings. The high layer station address selection should follow the principle of “little but extractive”. The high layer station is constructed mainly to solve the coverage problem of the high buildings in the cities. Some high layer stations are also constructed in the suburb, road, small towns and countryside because of the traffic direction control and wide coverage. (3) Low Layer Station The low layer station refers to the base station, whose antenna is less than 20 meters high and lower than the average height of the buildings. The antennas are generally installed on the outside wall of the lower floors of a building, building group, the top of the low roof garden or somewhere, or the rooms of a building. The coverage area 7

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only includes a street, part of a street or the rooms of a building. The low layer stations are frequently used. But they have rather low capacity of absorbing the traffic, mainly because the coverage area of the low layer station is small, when a station departs a little from the hot traffic center, it can hardly have an ideal traffic. Therefore, the low layer station construction needs you to consider if the purpose of construction is to supplement the coverage or solve the problem of high traffic, which will affect the address selection and the scale defining of the low layer station. After the field investigation with the help of the map, the general network structure can be decided. Generally, at the early stage of the network construction, single layer network design is applied, most base stations are middle layer station, when the basic network is established, the new base stations will be added of adjusted according to the traffic and coverage requirement. In the extremely high traffic area of the dense commercial areas, the low layer stations are constructed with the microcell layer and distributed antenna system, which meets the requirement of the indoor coverage, and at the same time avoids the interference and difficulties of station selection due to the too short distance between stations. The low layer stations will develops into the layered network structure.

III. Capacity Analysis (1) Capacity Prediction The network construction requires the consideration of economical feasibility and rationality. Only after predicting the network capacity of the early stage and the late stage, you can make a reasonable investment decision. The network capacity prediction should be based on the integrating consideration of the population distribution, family income, fixed telephone subscription ration, national economical development and city construction, etc. The different charge policy is also an important factor when the subscribers decide to access the network or not. After getting the predicted total capacity of the network construction, you need to predict the subscriber distribution density. Considering the real requirement of the project, the base stations are generally constructed in the city, suburb and transport artery. So the percentage ration can be applied for the prediction. At the early stage of the network construction, the subscribers in the cities account for more percentage of the predicted total subscribers, along with the deeper development of the network construction, the subscribers in the suburbs and along the transport arteries will increase in the percentage. Generally the traffic of each subscriber from a city and a suburb is 0.025Erl and 0.020Erl respectively. ×The traffic calculation formula is: A=（n×）/3600 In this way, the speech channel needed for a special base station can be predicted according to the traffic prediction.

Caution: It’s necessary to consider of the effects of the cell splitting while calculating the speech channel number. In the GSM system, the ERL model is applied to calculate the density of the traffic, which can be carried by the network. The call loss applies 2% or 5% depending on the real conditions. Limited by the cell coverage area and the bandwidth of the available frequency, the cell capacity should be planned reasonably and the channel usage ratio should be raised as much as possible without affecting the good voice quality. As to the traffic share of the two bands in dual band network construction, the looser frequency bandwidth can be used to realize the high usage ratio of the channels. In the real networking, on the premise of guaranteeing the network quality at a certain 8

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level, there are two capacity solutions, namely a few stations with high level configurations and any stations with lower level of configurations. They have obvious superiority and inferiority, which should be considered according to the different conditions of each area. In the network construction, the new base station construction and base station capacity expansion are two methods to increase the capacity. Different capacity expansion strategies, like adding 900M/1800M base station, sector capacity expansion, microcell and indoor coverage and so on, are applied for the areas of different traffic density. After defining the total capacity, decide the number of the base station (cell) and the base station configuration according to the frequency re-use pattern, integrate the coverage requirements (appearing as the antenna interface EIRP requirements), and finally select the suitable base station type and the combination of the Combiner/divider unit, antenna and the feeder line. (2) Cell Splitting The cell splitting is an effective way of network capacity expansion. It includes the performance of splitting a large omnidirectional base station into several sector cells and splitting the sector cells into smaller cells. In another word, it means the planning of different cell radius according to the traffic density of different areas. The cell splitting means to construct more base stations and increase the system construction investment. It’s necessary to consider the following factors: 

Be able to keep the image repetition of the frequency re-use regularity;



Make the existing base stations still usable;



Reduce or avoid the transition area;



Without affecting the consecutive splitting.

Since the cell splitting is fairly important, we hereunder make some more description of the common cell splitting measure of 1 into 4. The cell splitting is a way to split the congested cell into smaller cells. Each cell has its own base stations. The antenna should be shortened and the transmitter power should be reduced accordingly. Because the cell splitting increases the re-use time of the channel, the system capacity is increased. The number of channels in a unit area is increased through setting new cells with smaller radius than the original ones and fitting these cells (called as microcells) among the original cells. And the system capacity is increased accordingly. Suppose each cell is split by half of its radius, see Picture 1-2:

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Figure 1-2 Cell Splitting (1 in 4) Schematic Diagram In order to cover the whole service area with these smaller cells, about 4 times of the original cells are needed Ddraw a circle with the radius R to make it easier to understand. 以 The circle with the radius R covers the area 4 times large as the area covered by the circle with a radius of R/2. The increasing number of the cell increases the cluster number in the coverage area and then the channel number in the coverage area, thus the capacity is increased. The cell splitting allows the system growing through the smaller cells, instead of the larger cells, without affecting the channel distribution strategy necessary for keeping the minimum co-channel re-use genes between the co-channel cells. The Picture 1-2 is an example of cell splitting, the base station is placed on the corner of the cell. Suppose that the traffic in service area of the base station A is saturated (namely the congestion of base station A is over the acceptable value). Therefore new base stations are needed to increase the channel number in the area and reduce the coverage area of each single base station. In the example showed in Picture 1-2, the smaller cells are added on the premise of not changing the frequency re-use plan of the system. The cell splitting just zooms out the geometric shape of the cluster pro rata. Thus, the radius of each new cell is half of that of the original ones. As to the new smaller cells, the transmission power should be reduced. The transmission power of the new cell, whose radius is half of that of the original one, can be given by checking the power Pr received from the edge between the new and original cells, and letting them equal. This needs to ensure that the frequency re-use scheme of the new microcell is the same as that of the original cell. As to the Picture 1-2: Pr[at the edge of the original old cell] ∝ P t1 R

10

−n

（1）

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and Pr[at the edge of the new cell] ∝ P t2 (R/2)

−n

（2）

Here, Pt1 and Pt2 represent the base station transmission power of the larger and smaller cells respectively, n represents the path attenuation index. If let n=4, and let all powers received equal, then Pt2=Pt1/16 （3） That is to say, in order to cover the original coverage area with the microcells and reach the S/I requirements, the transmission power should be reduced by 12dB. In fact, not all cells split at the same time. Generally, it’s very difficult for the service providers to find the exact period suitable for the cell splitting. So the cells in different scales exist simultaneously. Under this condition, it needs to maintain the minimum distance between the co-channel cells, therefore the frequency distribution becomes even more complex. At the same time, attention should be paid to the problem of handover so that the high speed and low speed mobile subscribers can enjoy the service simultaneously. As shown in the Picture 1-2, when there are two scales of cells in one area, the formula (3) tells that the original transmission power cannot be simply applied for all of the new cells and the new transmission power also cannot be applied for all of the original ones. If all cells apply the bigger transmission power, some channels used by the smaller cells won’t be able to separate from the cochannel cells. 另 On the other hand, if all cells apply the lower transmission power, part of the area of the bigger cell will be excluded from the service area. Accordingly, the channels in the original cell should be divided into two groups, one of which meets the re-use requirement of the smaller cells, and the other one of which the bigger cells. When the bigger cells are used for high speed mobile communication, the time of handover will be reduced. The size of the two channel groups is decided by the splitting progress. At the early stage of the splitting progress, the channels in the low power group are less. However, more channels of the lower power group are needed to meet the increasing demand. The splitting progress will not stop until all channels in the area are used in the lower power group, and then the cell splitting will cover the whole area and the radius of each cell in the system becomes smaller. The antenna is often declined to focus the emission energy toward the ground, instead of on the horizontal direction, in order to limit the wireless coverage of the newly formed microcell. The above analysis tells that the coverage area design of the wireless network will not only solve the problem of the coverage area, but also meet the subscriber capacity requirement. The problem of the coverage area will be solved through constructing multiple base stations/cells. However, the construction of the base station is limited by the investment and restricts with each other. While the subscriber capacity is decided by the channel configuration, limited by the frequency resource and restricting each other. Therefore a unified planning is necessary.

IV. Station Address Planning The purpose of the station address planning is to select the best location for the base station. After the field examination, construct the base station in the center of a city with a safe subscriber prediction, then gradually enlarge the number of the base station on the map based on the principle of the cell mesh radius. Thus the ideal station address is selected. In the areas of different traffic density, the space between the base stations is different. Generally, in the area of high traffic density, the space between stations should be small, and the microcell and distributed antenna are applied in part of the hot spots to provide the multi-layer coverage and meet the capacity requirement. In a real project, it’s difficult to select the address. This is firstly because the irregularity of the landform and buildings causes the uneven signal coverage figure. On the other hand, the interference has to be avoided. In other words, not only the coverage but the interference should be considered before positioning the antenna. As to the whole network, you cannot only think of the location 11

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of one base station, instead, you should consider of the possibility of many addresses. Since the change of one address will affect the location of other base stations, the address selection of the base station should be based on a certain principle. After the address has been selected, the real station type will be defined according to the traffic distribution and the channel number of the base station.

V. Parameter Design of the Base Station Engineering Decide the height of antenna hanging position according to the different coverage area types, network structures and average height of the buildings. As to the base station moving, the necessity of height adjustment of the antenna is decided according to the network construction condition, objects required by subscribers to cover and the installation environment. In some mountainous area, because of the landform, the base station has to be constructed on the mountain, it's better to select the directional antenna or the omnidirectional antenna with an electric declination angle, and avoid the “blind under tower”. The base station antennas are divided into two types, omnidirectional and directional antenna based on the horizontal direction. 在 In the vertical plane, all antennas have directions. Generally the gain of the omnidirectional antenna is 6dBd~9dBd; the gain of the directional antenna is 9dBd~16dBd. The gain of the directional antenna refers to the gain in the maximum transmission direction. Generally, the omnidirectional base station is constructed only in the villages on the plain or some special landform, while the directional antenna is used in the base station of other areas on the whole. In the subscriber density cities, the common base stations (excluding the microcell and indoor distributed antenna system) are installed with the directional antenna at the angle of 65 degree. In order to avoid the antenna interference, the antenna gain doesn’t need to be too high. The base station, with a few centralized subscribers and needing a wide coverage, generally applies the directional antenna with high gain. The antenna direction angle and the declination angle (electronic declination or mechanical declination) should be designed reasonably. In order to guarantee the normality of the network structure design and avoid the interference as much as possible, the antennas of each sector in each base station of the local area is recommended to have the same direction, for example designed as 0°/120°/240° or 30°/150°/270°. While the antenna direction needs to be adjusted in the base stations close to the sea, along the river, transport artery and the city-suburb combination, areas with uneven traffic and center of city with many high buildings. What’s need highlighting is that because there are high buildings along many streets in cities in different size, the base station cell antennas nearby cannot be installed with an azimuth angle facing the street in order to avoid the wave-guide effect. The antenna declination angle should be decided according to the special conditions on the premise of reducing the interference to the co-channel cell and covering the whole coverage area without unnecessary blind area; when it declines too much, the ratio emission in front of and behind the antenna must be considered, avoiding the back lobe interfering the cell behind or the side lobe interfering the neighbor sector. Generally speaking, design a rather big declination angle for the cells near to the water surface to avoid the interference to the opposite side of the water; the obliquity of 3~6 degree for the dense city center; no declination for the suburb and artery cell in order to widen the coverage area. In addition, the suitable feeder line, combiner and the tower amplification unit should be selected according to the special conditions.

VI. Coverage Prediction The coverage prediction is to predict the coverage of the network to be constructed, according to the address selected and the type designed, and to see if it can meet the demand of the subscribers. The coverage can be predicted with the help of the ASSET Network Planning Tools to select a map with a suitable accuracy. The coverage area of a base station mainly concerns the following factors: service quality 12

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index; transmitter output power; available sensibility of the receiver; the direction and gain of the antenna; frequency band applied; emission environment (landform, city construction and other man-made environment); application of the diversity reception. In case the result of the network coverage prediction cannot meet the requirements, the adjustment should be done. The usual measures include: (1) When there are subscribers outside the cell coverage area, where is not economical to construct a site, broadcast station can be applied to solved the problem. When the signal in the coverage area is weak or there is blind area in it, the microcell can be considered to solve the problem according to the conditions. (2) If the cell coverage areas don’t overlap one another enough, it should be considered to increase the height of the antenna position or the number of the base station according to the cell splitting principle. (3) When the cell coverage area cannot hit the co-channel reference index, make adjustment as follow: 

Adjust the cell channel configuration;



Adjust the station address or other design parameters (including the antenna type, height of position, azimuth angle, the declination angle and transmission power). Accordingly the effects between the base stations need considering.

VII. Frequency Planning The frequency re-use pattern is one of the important factors to be considered in the cell system planning. The frequency re-use refers to the application of the wireless channels at the same frequency in the cells of different coverage areas. The cells of frequency re-use should have a certain interval between each other to meet the requirement of the adjacent frequency carrier-to-interference ratio. The re-use degrees of the same frequency are different in the different re-use patterns. Different frequency re-use patterns are applied in areas of different types. In a certain area, on the promise of enough coverage, the number of the base station (cell) is decided by the frequency planning pattern. Generally speaking: (1) In the big and middle-sized cities, different aggressive frequency re-use patterns, like MRP, 1×3, etc., are applied according to the different equipment functions. At the same time, reserve part of the frequency band for the microcell to construct layered network. Its frequency re-use coefficient is rather small. (2) In the small and middle-sized cities, different aggressive frequency re-use patterns, are applied according to the different equipment functions. Whether it’s necessary to construct the layered network depends on the real condition. Its frequency re-use coefficient is a little bigger than that of the big and middle-sized cities. (3) In the towns and villages, which are rich in the resources, the standard 4×3 frequency re-use pattern can be applied. The stations, constructed on the mountains for some geographic reasons, can be allocated some independent frequency bands. At the pre-planning stage, the planners should present the application for the frequency resource according to the scale and frequency planning pattern of the wireless network.

VIII. LAC Planning LAC is also an important resource. At the pre-planning stage, the planners should present the initial allocation and resource application of the LAC based on the consideration of network structure and scale.

IX. Cell Data Making In order to guarantee the good and stable running of the network, it’s also necessary 13

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to configure the relevant data for each base station cell. What has to be highlighted is: the cell attribute parameters, cell handover band selection, channel allocation algorism selection, turn on which handover algorism, and whether to use the functions, like frequency hopping, power control and DTX, should have been decided in the above base station design, coverage prediction and frequency planning. In the GSM system of Huawei, as to the detailed data design and configuration, please read the Data Configuration Criterion of the GSM900, 1800 BSS network planning for reference.

1.2.4 Pre-planning Difficulties As shown in the above progress, the pre-planning difficulties are reflected in the following aspects: (1) Complex emission environment, severely fluctuate signal, big difference of the multi-approach emission caused by the various man-made buildings, and the difficulties in theoretic prediction of the coverage area. (2) Severe interference. Except for the human noises, all adjacent frequency interference, intermodulation interference and other wireless interference should be considered and controlled in the permitted index during the engineering design. (3) Limited frequency resources. It’s getting more serious along with the big increasing of the subscriber. (4) There are strict rules for the cell structure and the cell splitting behavior designed for the frequency re-use. The station address planning can hardly be carried out in the real project due to various reasons. (5) The investment control is the technical and economical issue of the network construction, which can be by no means ignored.

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