Introduction
The objective of coverage planning phase in coverage limited network areas is to find a minimum amount of cell sites with optimum locations for producing the required coverage for the target area.
Coverage planning is normally performed with prediction modules on digital map database. The basic input information for coverage planning includes:
• Coverage regions
• Coverage threshold values on per regions (outdoor, in-car, indoor)
• Antenna (tower height limitations)
• Preferred antenna line system specifications
• Preferred BTS specification
Activities such as propagation modeling, field strength predictions and measurements are usually referred to as coverage planning.
Site selection:
Coverage planning and site selection are performed on parallel with the site acquisition in interactive mode. Both network planning team and site acquisition should team have well defined responsibilities and means to communicate.
Propagation models
Propagation models are essentially curve fitting exercises. Propagation tests are conducted at different frequencies, antenna heights, and locations over different periods and distances. The receive signal data is analyzed using mathematical tools and are fitted to an appropriate curve. Formula to match these curve are then generated and used as models.
Some of the major propagation models are:
• Long-distance propagation model
• Longley-Rice model (irregular terrain model)
• Okumara
• Hata
• Cost 231-Hata (similar to Hata: for 1500-2000 MHz band)
• Wolfish-Ikegami Cost 231
• Wolfish-Xia JTC
• XLOS (Motorola proprietary model)
• Bullington
• Du Path loss model
• Diffracting Screens model
Coverage predictions
The possibilities for rough coverage calculations based on propagation curves formulas. These average values are not enough for the detailed network planning; therefore many computer-aided tools based on digital maps usage have been developed to improve the quality of the predictions.
Digital maps
There are different types of information that can be digitized and used for coverage predictions. The most important from the network planning point of view are topography (terrain heights), morphography (area types), rods traffic density.
For the micro cell modeling, which is required in a dense urban environment, more information and heighten resolution maps should be used. Information about the buildings and streets is essential, so the pixel size from 5m to 25m is reasonable. The streets can be stored and used in vector format.
Point to point and cell coverage
Using a given digital map it is not difficult to obtain the path profile between any two points, say BS and MS. Furthermore the profile can be related to the corresponding area types, thus making possible the calculation of specific propagation loss. Normally different corrections, such as the diffraction loss or mixed land-sea path correction are added to the basic propagation loss. the result of such point to point calculations can be used for cell coverage prediction. There are two basic approaches:
• Radial calculations
• Pixel by pixel calculations
The latter one gives better possibilities for the interference predictions, so the results should be transferred to the raster format even if the radial approach is used.
Field strength measurements
The field strength measurements are needed for determination of coverage areas as well as for tuning the propagation model of network planning system. In case of measurement before base station installation the site should equipped with the test transmitter. Possible test transmitter configurations are mobile station base station channel unit signal generator with power amplifier. The selection of routs to be measured depends on the purpose of the measurements. The most critical routs are typical located in urban or hilly areas. Where it is difficult to predict the field strength values with high accuracy.
During the field strength measurement, the measuring system normally takes the samples from the signal received by the antenna. The field strength samples recorded by a control computer with time, location marks. Using the samples it is possible to calculate the average values.
Propagation Model Tuning
The propagation models are not universal. The predictions must be verified by measurements and the models tuned accordingly. The model testing and tuning is a very sophisticated and challenging task, which requires detailed knowledge of the propagation nature. It should be done for every area type in a given country or region before the detailed network planning is started.
Extension of cell coverage area
The cellular area extension can be done with cellular repeaters and preamplifiers.
The cellular repeater amplifies the RF signal in both uplink and downlink directions, i.e. it is a device which compensates the propagation loss between the base station antenna and mobile station antenna. The cellular repeater antenna is connected between two antennas: the first antenna is pointed to the base station site and the second one (reradiating elements) is pointed to the area to be covered. Propagation Model Tuning
The propagation models are not universal. The predictions must be verified by measurements and the models tuned accordingly. The model testing and tuning is a very sophisticated and challenging task, which requires detailed knowledge of the propagation nature. It should be done for every area type in a given country or region before the detailed network planning is started.
Extension of cell coverage area
The cellular area extension can be done with cellular repeaters and preamplifiers.
The cellular repeater amplifies the RF signal in both uplink and downlink directions, i.e. it is a device which compensates the propagation loss between the base station antenna and mobile station antenna. The cellular repeater antenna is connected between two antennas: the first antenna is pointed to the base station site and the second one (reradiating elements) is pointed to the area to be covered.
The objective of coverage planning phase in coverage limited network areas is to find a minimum amount of cell sites with optimum locations for producing the required coverage for the target area.
Coverage planning is normally performed with prediction modules on digital map database. The basic input information for coverage planning includes:
• Coverage regions
• Coverage threshold values on per regions (outdoor, in-car, indoor)
• Antenna (tower height limitations)
• Preferred antenna line system specifications
• Preferred BTS specification
Activities such as propagation modeling, field strength predictions and measurements are usually referred to as coverage planning.
Site selection:
Coverage planning and site selection are performed on parallel with the site acquisition in interactive mode. Both network planning team and site acquisition should team have well defined responsibilities and means to communicate.
Propagation models
Propagation models are essentially curve fitting exercises. Propagation tests are conducted at different frequencies, antenna heights, and locations over different periods and distances. The receive signal data is analyzed using mathematical tools and are fitted to an appropriate curve. Formula to match these curve are then generated and used as models.
Some of the major propagation models are:
• Long-distance propagation model
• Longley-Rice model (irregular terrain model)
• Okumara
• Hata
• Cost 231-Hata (similar to Hata: for 1500-2000 MHz band)
• Wolfish-Ikegami Cost 231
• Wolfish-Xia JTC
• XLOS (Motorola proprietary model)
• Bullington
• Du Path loss model
• Diffracting Screens model
Coverage predictions
The possibilities for rough coverage calculations based on propagation curves formulas. These average values are not enough for the detailed network planning; therefore many computer-aided tools based on digital maps usage have been developed to improve the quality of the predictions.
Digital maps
There are different types of information that can be digitized and used for coverage predictions. The most important from the network planning point of view are topography (terrain heights), morphography (area types), rods traffic density.
For the micro cell modeling, which is required in a dense urban environment, more information and heighten resolution maps should be used. Information about the buildings and streets is essential, so the pixel size from 5m to 25m is reasonable. The streets can be stored and used in vector format.
Point to point and cell coverage
Using a given digital map it is not difficult to obtain the path profile between any two points, say BS and MS. Furthermore the profile can be related to the corresponding area types, thus making possible the calculation of specific propagation loss. Normally different corrections, such as the diffraction loss or mixed land-sea path correction are added to the basic propagation loss. the result of such point to point calculations can be used for cell coverage prediction. There are two basic approaches:
• Radial calculations
• Pixel by pixel calculations
The latter one gives better possibilities for the interference predictions, so the results should be transferred to the raster format even if the radial approach is used.
Field strength measurements
The field strength measurements are needed for determination of coverage areas as well as for tuning the propagation model of network planning system. In case of measurement before base station installation the site should equipped with the test transmitter. Possible test transmitter configurations are mobile station base station channel unit signal generator with power amplifier. The selection of routs to be measured depends on the purpose of the measurements. The most critical routs are typical located in urban or hilly areas. Where it is difficult to predict the field strength values with high accuracy.
During the field strength measurement, the measuring system normally takes the samples from the signal received by the antenna. The field strength samples recorded by a control computer with time, location marks. Using the samples it is possible to calculate the average values.
Propagation Model Tuning
The propagation models are not universal. The predictions must be verified by measurements and the models tuned accordingly. The model testing and tuning is a very sophisticated and challenging task, which requires detailed knowledge of the propagation nature. It should be done for every area type in a given country or region before the detailed network planning is started.
Extension of cell coverage area
The cellular area extension can be done with cellular repeaters and preamplifiers.
The cellular repeater amplifies the RF signal in both uplink and downlink directions, i.e. it is a device which compensates the propagation loss between the base station antenna and mobile station antenna. The cellular repeater antenna is connected between two antennas: the first antenna is pointed to the base station site and the second one (reradiating elements) is pointed to the area to be covered. Propagation Model Tuning
The propagation models are not universal. The predictions must be verified by measurements and the models tuned accordingly. The model testing and tuning is a very sophisticated and challenging task, which requires detailed knowledge of the propagation nature. It should be done for every area type in a given country or region before the detailed network planning is started.
Extension of cell coverage area
The cellular area extension can be done with cellular repeaters and preamplifiers.
The cellular repeater amplifies the RF signal in both uplink and downlink directions, i.e. it is a device which compensates the propagation loss between the base station antenna and mobile station antenna. The cellular repeater antenna is connected between two antennas: the first antenna is pointed to the base station site and the second one (reradiating elements) is pointed to the area to be covered.
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