Telecommunications – Transmitter and receiver at separate stations – Having measuring – testing – or monitoring of system or part
Reexamination Certificate
2001-05-21
2004-12-21
Kincaid, Lester G. (Department: 2682)
Telecommunications
Transmitter and receiver at separate stations
Having measuring, testing, or monitoring of system or part
C455S446000, C455S422100, C455S423000, C455S424000
Reexamination Certificate
active
06834180
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to software, systems and methods used to determine the coverage of cell sites for cellular phones and, more particularly, to a method and system used to generate and calibrate site specific coverage models.
2. Description of the Related Technology
Cellular radio systems provide wireless connections between portable cellular telephones and a cellular radio infrastructure of cell sites and interconnecting network facilities. In an ideal environment with uniform frequency usage and cell coverage, cell sites might be arranged in a honeycomb-like pattern to maximize individual cell utilization. However, such an ideal arrangement is seldom, if ever, applicable in real world environments. Instead, geographic coverage of cell sites is dictated by many factors, including density of users, topology, interference, and other factors. Thus, simulation systems are used to model cell sites and cellular networks as part of cellular network design, upgrade and maintenance procedures. However, because of the variability between and among even similar locations, models must be calibrated to conform to the actual planned cell site environment.
Hoque, U.S. Pat. No. 5,410,736, entitled “Method For Determining Radio Transmitter Sites With Signals That May Potentially Interfere With An Intended Signal At A Radio Receiver Site”, issued Apr. 25, 1995 describing a method for conducting radio transmission systems interference studies by modifying a conventional two-step process of conducting a simple analysis on all potentially interfering systems to eliminate those clearly not causing interference into radio receiver under study, and then conducting a detailed analysis on the remaining systems. The disclosure describes replacing the first step with a method using pre-calculated average terrain elevations over a geographic block for determining whether the loss should be calculated using a smooth terrain calculation method with a simulated single knife edge diffraction obstacle in the path, or a rough terrain calculation method that substitutes a pre-calculated block roughness factor in place of the path roughness factor. The disclosure also describes substituting a new effective antenna height for the actual antenna height in propagation loss calculations.
U.S. Pat. No. 5,787,350 to van der Vorm, et al. entitled “Method for Determining Base Station Locations, and Device for Applying the Method” issued Jul. 28, 1998 describing automated determination of base station locations by calculating, for each location, a number which is a function of a parameter associated with that location (telephone traffic, field strength, motor traffic) and of parameters belonging to adjoining locations, and by assigning a base station to the location having the most extreme number. Then the parameter associated with that location, and the parameters associated with adjoining locations are each adjusted on the basis of an adjustment function associated with the base station, and new numbers are calculated which are a function of the new, adjusted parameters, etc.
Brockel, et al., U.S. Pat. No. 5,794,128, entitled “Apparatus and Processes For Realistic Simulation Of Wireless Information Transport Systems” issued Aug. 11, 1998 describing models and processes for simulating wireless information transport systems using time and frequency dynamic effects on stationary and mobile communications systems. A modeling system includes a data entry module, a communications traffic selection module, a driver database, and voice and data input modules furnishing a simulation input to a network simulation module. The network simulation module has communications “realism” effects, a it distributed interactive simulation structure, a channel error-burst model to transmit random errors, and a multipath modeling module to integrate deterministic and stochastic effects. The multipath modeling module, having a digital radio model and a Terrain-Integrated Rough Earth Model, influences the simulation inputs forming a multipath output, which is adjusted by voice and data inputs to provide a real-time simulation output signal to a module displaying the simulated communications network and link connectivity.
Lee, et al., U.S. Pat. No. 6,032,105 entitled “Computer-Implemented Microcell Prediction Modeling with Terrain Enhancement” issued Feb. 29, 2000 describing a computer-implemented modeling tool for cellular telephone systems that predicts signal strength by considering the effects of terrain and man-made structures on transmitted signals. The modeling tool gives predictions under line of sight conditions, when obstructions occur due to terrain contours, and when mobile or transmitter antennas are blocked by buildings or other structures.
As described in these four disclosures, all of which are incorporated herein by reference in their entirety, various methods and techniques are used to model cellular telephone system operation including predicting coverage of each of the radio transceiver cell sites forming the mosaic network of microwave frequency radio stations communicating with the portable cellular telephones. Such models are critical because, although the cellular service provider measures the signal strength directly, individual measurements would not enable the provider to know the signal strength at every point within the cell to confirm cell coverage and identify and address problem locations.
Unlike theoretical free space propagation, actual signal depends on local up environmental characteristics within the cell. Cellular service providers use models to estimate the signal strength at any point within the cell. These models predict system coverage and potential interference at points within the cell by determining the signal path loss from the cell site to the specific point within the cell. Cellular service providers use this information for a variety of purposes including initial cell site location, placement of addition cell sites, frequency planning, and to determine the power required at specific sites.
Many factors are included in the determination of signal path loss to a specific point within the cell. Three main concerns are transmission, environment and losses due to multiple signal paths (multi-path) causing self-destructive interference. Transmission modeling is used to predict the power available from the antenna at locations within the intended cell site coverage space. In general, the amount of power at the output of the antenna is a function of the amount of power provided to the antenna and the antenna radio frequency radiation pattern. These two factors, power output and antenna gain, sometimes expressed as Effective Radiated Power (ERP), are crucial in determining the signal strength along various radials from the antenna.
Methods for calculating ideal transmission loss are well known. Transmitter power output, transmission cable loss, antenna gain, free space propagation loss, antenna and receiver gain can all be calculated and used to predict a theoretical, best case cell coverage.
Environment modeling involves determining the effects of the terrain features between the cell site and the specific position within the cell. (Contrary to its designation, environmental modeling at typical cellular radio operating frequencies does not normally encompass weather conditions such as humidity, precipitation, temperature, etc.) While signal path losses attributable to dispersion increase as the inverse square of the distance from the cell site increases, environment factors can greatly affect these losses. Modeling of the environment includes the signal reduction due to the distance from the cell site as well as defraction losses caused by buildings or other terrain features between the cell site and the specific point within the cell. Furthermore, since radio propagation conditions vary significantly in typical operating environments, signal path loss models normally account for the statistical variability of the received signal (which is defined
Cellco Partnership
Fulbright & Jaworski LLP
Kincaid Lester G.
Pan Yuwen
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