(12) United States Patent
`Smith et al.
`
`I lllll llllllll Ill lllll lllll lllll lllll lllll 111111111111111111111111111111111
`US006289203Bl
`US 6,289,203 Bl
`Sep.11,2001
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54) METHOD OF CALCULATING SIGNAL
`PROPAGATION LOSS AND CREATING A
`DATA BASE THEREFOR
`
`(75)
`
`Inventors: Jack Anthony Smith, Bedford; John
`Douglas Reed, Arlington; Adam
`Dewhirst, Austin, all of TX (US)
`
`(73) Assignee: Motorola, Inc., Schaumburg, IL (US)
`
`( *)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21)
`
`Appl. No.: 09/030,091
`
`(22)
`
`Filed:
`
`Feb. 25, 1998
`
`Int. Cl.7 ....................................................... H04Q 7/20
`(51)
`(52) U.S. Cl. ............................................ 455/67.1; 455/423
`(58) Field of Search .................................. 455/67.1, 67.3,
`455/67.4, 67.5, 67.7, 423, 446
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`5,179,722 * 1/1993 Gunmar et al. ..................... 455/67.7
`5,491,644 * 2/1996 Pickering et al.
`.................. 455/67.4
`5,561,841 * 10/1996 Markus ............................... 455/67.7
`5,828,960 * 10/1998 Tang et al. ........................... 455/466
`5,953,669 * 9/1999 Stratis et al. ........................ 455/67.3
`
`OIBER PUBLICATIONS
`
`Net Plan RF Engineering User's Manual, Release 3.1, 1197,
`Motorola Inc.
`Census Feature Class Codes, tiger/line files, 1995 Technical
`Documentation, Bureau of the Census, Washington DC,
`1996.
`
`1996 IEEE 46th Vehicular Technology Conference Proceed(cid:173)
`ings, vol. 3, IEEE Service Center, 445 Hoes Lane, PO Box
`1331, Piscataway, NJ 088855, Cat. Nos.: 96CH35894,
`96CB35894.
`
`Wireless Communications Principles and Practice, by T. S.
`Rappaport, pp. 110--120, 1996, Prentice Hall, upper Saddle
`River, New Jersey 07458.
`
`* cited by examiner
`
`Primary Examiner-Daniel S. Hunter
`Assistant Examiner-Myron K. Wyche
`(74) Attorney, Agent, or Firm-Sayed Hossain Beladi;
`Mario J. Donato, Jr.
`
`(57)
`
`ABSTRACT
`
`A method for determining a final propagation loss of a signal
`transmitted from a transmitter (302) and received at a
`receiver (303) located in a proximity of a road (340) in a
`predefined area (350) includes calculating an environmental
`factor based on a transportation network information asso(cid:173)
`ciated with predefined area (350), and determining the final
`propagation loss based on the environmental factor. A
`method of creating a data base used for calculating the
`propagation loss includes providing a preliminary data base,
`calculating a road density constant based on a road profile of
`predefined area (350), calculating a road constant based on
`a road classification profile of road (340), calculating the
`environmental factor by summing the road density constant,
`and the road constant, and modifying the preliminary data
`base according to the environmental factor to produce the
`data base.
`
`13 Claims, 3 Drawing Sheets
`
`202
`
`203
`
`204
`
`205
`
`207
`MODIFY ELEVATION PROFILE BASED
`ON CLUTTER VALUES
`
`209
`CALCULATEENVIRONMENTALFACTORE1
`
`MODIFY ELEVATION PROFILE
`BASEDONENVIRONMENTALFACTORE1
`210
`
`213
`MODIFYPATHLOSSVALUEBASED
`ON CLUTTER VALUES
`
`214
`CALCULATEENVIRONMENTALFACTORE2
`
`MODIFYPATHLOSSVALUE
`BASEDONENVIRONMENTALFACTORE2
`216
`
`Ericsson v. IV II LLC
`Ex. 1025 / Page 1 of 9
`
`

`

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`RECEIVE LOCATIONS
`
`DATABASE OF
`
`DISPLAY UNIT
`r102
`
`-
`
`TRANSMIT LOCATIONS
`
`DATABASE OF
`
`160
`
`150
`
`/100
`
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`
`PROCESSING UNIT
`
`CENTRAL
`
`',
`
`101"
`
`KEYBOARD ~ -
`
`1031
`
`DATABASE OF POPULATION
`110,
`
`DATA BY AREA
`
`DIGIT AL TRAFFIC
`140
`
`PROFILE
`
`DIGIT AL CLUTTER
`130
`
`PROFILE
`
`DIGITAL ELEVATION
`120
`
`PROFILE
`
`Ex. 1025 / Page 2 of 9
`
`

`

`U.S. Patent
`
`Sep.11,2001
`
`Sheet 2 of 3
`
`US 6,289,203 Bl
`
`OBTAIN TRANSMIT LOCATION OF
`INTEREST FROM TRANSMITTER DATABASE
`
`OBTAIN RECEIVE LOCATION OF INTEREST
`FROM RECEIVER LOCATION
`
`OBTAIN ELEVATION PROFILE BETWEEN
`TRANSMIT AND RECEIVE FROM DEM
`
`OBTAIN CLUTTER PROFILE BETWEEN
`TRANSMIT AND RECEIVE DEM
`
`202
`
`203
`
`204
`
`205
`
`YES
`
`F JG. 2
`/200
`
`NO
`
`YES
`
`209
`CALCULATE ENVIRONMENTAL FACTOR E1
`
`MODIFY ELEVATION PROFILE
`BASED ON ENVIRONMENTAL FACTOR E1
`210
`
`CALCULATE PATHLOSS USING ELEVATION
`PROFILE AND A STANDARD TECHNIQUE
`
`211
`
`YES
`
`213
`MODIFY PATHLOSS VALUE BASED
`ON CLUTTER VALUES
`
`YES
`
`214
`CALCULATE ENVIRONMENTAL FACTOR E2
`
`MODIFY PA THLOSS VALUE
`BASED ON ENVIRONMENTAL FACTOR E2
`216
`
`PATHLOSS CALCULATION COMPLETE
`220
`
`217
`
`Ex. 1025 / Page 3 of 9
`
`

`

`U.S. Patent
`U.S. Patent
`
`Sep. 11, 2001
`Sep.11,2001
`
`Sheet 3 of 3
`Sheet 3 of 3
`
`US 6,289,203 B1
`US 6,289,203 Bl
`
`500
`/300
`330 a
`320
`320 | 201320
`320
`320
`320
`
`7320
`-
`
`320
`320
`
`340
`
`320
`
`320
`
`350
`350
`
`320 320
`
`TX
`~ if IX
`-1
`3
`302
`302
`
`340
`340
`
`330
`330
`
`010]
`
`
`1
`
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`0]
`4
`1
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`
`320
`320
`
`320
`320
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`311
`3N
`
`311
`jn
`
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`
`
`
`1/010
`362+1])0!2
`
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`303°
`303
`4
`
`210 |i4
`361
`|
`361
`351 0
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`4
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`560
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`F JG. 3
`
`Ex. 1025 / Page 4 of 9
`
`Ex. 1025 / Page 4 of 9
`
`

`

`US 6,289,203 Bl
`
`1
`METHOD OF CALCULATING SIGNAL
`PROPAGATION LOSS AND CREATING A
`DATA BASE THEREFOR
`FIELD OF THE INVENTION
`The present invention generally relates to a method of
`calculating propagation loss of a signal and creating a data
`base therefor.
`BACKGROUND OF THE INVENTION
`A wireless communication system normally spans its
`coverage over a wide geographical area. A controller of the
`communication system maintains an efficient communica(cid:173)
`tion system operation by utilizing propagation loss charac(cid:173)
`teristics of the coverage area to calculate a transmitted
`power level of various transmitters in the coverage area. In
`addition, propagation loss characteristics are used for initial
`system layout, system modifications, system
`rearrangements, site specific parameter adjustments, and
`adding or eliminating system base station sites. The propa(cid:173)
`gation loss characteristic is affected by terrain of the cov(cid:173)
`erage area. The terrain is very often comprised of different
`categories of terrain irregularities, and some these irregu(cid:173)
`larities change over time. The terrain irregularities normally
`are in the form of man-made objects such as buildings,
`bridges, towers, roads and cars, and natural objects, such as
`hills, mountains, and trees.
`Terrain irregularities have often been given names, such
`as clutter, and elevation irregularities. Such irregularities are
`stored in one or more data profiles. The clutter profile
`generally includes data about objects on the earth's surface
`such as homes, buildings, trees, and agricultural crops. The
`United States Geological Survey has categorized the clutter
`information in many categories and sub-categories. The
`clutter profile of the coverage area changes more often than
`the elevation profile. Clutter profile changes very often
`because man and nature effect the clutter characteristic much
`easier in a short period of time than the elevation charac(cid:173)
`teristic. When the characterization of the propagation envi(cid:173)
`ronment is based on an outdated clutter profile, the results
`are adversely affected. For example, inaccurate signal propa(cid:173)
`gation characterization causes the wireless communication
`system to operate in a less efficient capacity, resulting in a
`less optimal system layout design.
`Since clutter profiles are expensive, and gathered by
`time-consuming aerial and land surveys of the coverage
`area, an up-to-date clutter profile often is unavailable. As
`such, there is a need for a method of efficiently character(cid:173)
`izing a propagation environment without reliance on up-to(cid:173)
`date clutter information, and creating a data base therefor.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 depicts a block diagram of a computer system
`having access to data bases for calculating propagation loss
`of a signal according to various embodiments of the present
`invention.
`FIG. 2 depicts various combinations of a method for
`calculating propagation loss of a signal, and creating a data
`base therefore according to various embodiments of the
`present invention.
`FIG. 3 depicts a transportation network and its elements
`for calculating an environmental factor according to various
`embodiments of the present invention.
`
`DETAILED DESCRIPION OF THE PREFERRED
`EMBODIMENTS
`According to an embodiment of the present invention, a
`propagation loss of a signal transmitted from a transmitter
`
`5
`
`2
`and received at a receiver is determined. The receiver in
`particular is in a predefined area. The predefined area has an
`elevation profile and a clutter profile. The predefined area
`may include one or more roads. At first, an environmental
`factor is calculated based on a road density, a population
`density, a road constant and a road orientation constant, all
`associated with the predefined area. In particular, the road
`constant is based on a predefined road class normally found
`in the predefined area. The road orientation constant is based
`10 on an angle of the signal propagation direction from the
`transmitter to the receiver and a direction of the road where
`the receiver has an adequate proximity. The elevation profile
`is modified according to the environmental factor to produce
`a modified elevation profile. Finally, the propagation loss is
`15 determined based on the modified elevation profile and the
`clutter profile. In addition to the step of modifying the
`elevation profile according to the environmental factor, the
`elevation profile may be modified according to the clutter
`profile. As an advantage of the present invention, any
`20 adverse effect of the clutter profile inaccuracy, due to its
`possible outdated data, accordingly is reduced. Such a result
`is possible by a propagation loss determination that is based
`on the modified elevation profile data.
`In another embodiment of the present invention, a propa-
`25 gation loss of a signal transmitted from a transmitter and
`received at a receiver is determined. The receiver in par(cid:173)
`ticular is in a predefined area. The area has an elevation
`profile and a clutter profile. The predefined area may include
`one or more roads. At first, an environmental factor is
`30 calculated based on a road density, a population density, a
`road constant and a road orientation constant, all associated
`with the predefined area. In particular, the road constant is
`based on a predefined road class normally found in the
`predefined area. The road orientation constant is based on an
`35 angle of the signal propagation direction from the transmit(cid:173)
`ter to the receiver and a direction of a road where the
`receiver has an adequate proximity. A preliminary propaga(cid:173)
`tion loss is determined based on the elevation profile and the
`clutter profile. Then, the preliminary propagation loss is
`40 modified according to the environmental factor to produce
`the propagation loss. In addition to the step of modifying the
`preliminary propagation loss according to the environmental
`factor, the preliminary propagation loss may be modified
`according to the clutter profile. As an advantage of the
`45 present invention, any adverse effect of the clutter profile
`inaccuracy, due to its possible outdated data, accordingly is
`reduced. Such a result is possible by a propagation loss
`determination where its preliminary propagation loss is
`modified according to the environmental factor.
`In another embodiment of the present invention, a propa-
`gation loss of a signal transmitted from a transmitter and
`received at a receiver is determined. The receiver particu(cid:173)
`larly is in a predefined area. The area has an elevation profile
`and a clutter profile. The predefined area may include one or
`55 more roads. At first, a first and second environmental factors
`are calculated based on a road density, a population density,
`a road constant and a road orientation constant, all associ(cid:173)
`ated with the predefined area. In particular, the road constant
`is based on a predefined road class normally found in the
`60 predefined area. The road orientation constant is based on an
`angle of the signal propagation direction from the transmit(cid:173)
`ter to the receiver and a direction of a road where the
`receiver has an adequate proximity. The elevation profile is
`modified according to the first environmental factor to
`65 produce a modified elevation factor. A preliminary propa(cid:173)
`gation loss is determined based on the modified elevation
`factor and the clutter profile. The preliminary propagation
`
`50
`
`Ex. 1025 / Page 5 of 9
`
`

`

`US 6,289,203 Bl
`
`3
`loss is modified according to the second environmental
`factor to produce the propagation loss. In addition to the step
`of modifying the elevation profile according to the first
`environmental factor, the elevation profile may be modified
`according to the clutter profile. In addition or as an
`alternative, before the step of modifying the preliminary
`propagation loss according to the second environmental
`factor, the preliminary propagation loss may be modified
`according to the clutter profile. As an advantage of the
`present invention, any adverse effect of the clutter profile
`inaccuracy, due to its possible outdated data, accordingly is
`reduced. Such a result is possible by a propagation loss
`determination where the elevation profile is modified
`according to the first envirornental factor, and the resulting
`preliminary propagation loss is modified according to the
`second environmental factor.
`A method of creating a data base used for calculating a
`propagation loss of a signal transmitting from a transmitter,
`receiving by a receiver located in proximity of a road, and
`propagating through a propagation environment, includes
`providing a preliminary data base including at least: a
`location profile of the transmitter, a location profile of the
`receiver, an elevation profile of the propagation
`environment, and a road profile of the propagation environ(cid:173)
`ment including at least a road density profile and a road
`classification profile. Further steps include defining an area
`a surrounding a location of the receiver located within the
`propagation environment, calculating a road density con(cid:173)
`stant based on the road profile of the area, calculating a road
`constant based on the road classification profile of the road,
`calculating an environmental factor by summing the road
`density constant, and the road constant, and modifying the
`preliminary data base according to the environmental factor
`to produce the data base.
`According to one or more embodiments of the present
`invention, where the preliminary data base further includes
`a clutter profile of the propagation environment, the eleva(cid:173)
`tion profile may be modified according to the clutter profile.
`The preliminary data base further includes a population
`profile of the propagation environment, and the method
`further includes a step of calculating a population density
`constant of the area. The environmental factor then incor(cid:173)
`porates the population density constant. The method further
`includes the step of calculating a road orientation constant
`based on an angle of the signal propagation direction and a
`direction of the road obtained from the road density profile,
`and incorporating the road orientation constant in calculat(cid:173)
`ing the environmental factor.
`In each of these embodiments, the user may selectively
`remove all or part of the clutter information from the
`database for the coverage area, or turn off the inclusion of
`clutter information completely in the propagation loss deter(cid:173)
`mination. This decision is based on the user's evaluation of
`the quality or availability of the clutter data throughout the
`coverage area.
`Referring to FIG. 1, a computer system basic block
`diagram 100 for calculating a propagation loss of a signal
`according to various embodiments of the present invention
`is shown. Computer system 100 normally includes a central
`processing unit 101, a keyboard 103, and a display unit 102 60
`for possible interaction with a user. Central processing unit
`101 has access to various terrain information databases. The
`databases include population data 110 by area, elevation
`profile data 120, clutter profile data 130, traffic profile data
`140, communication system transmitter locations 150 and 65
`receiver locations 160. Elevation profile data 120, clutter
`profile data 130 and traffic profile data 140 may be in a
`
`4
`digital format for ease of usability in the computer system
`100. A computer program loaded in computer system 100
`calculates propagation loss of a signal transmitted and
`received in the communication system according to various
`5 embodiments of the present invention. The signal is trans(cid:173)
`mitted from a transmitter identified in transmitter locations
`150 database and received by a receiver identified in
`receiver locations 160 database.
`Referring to FIG. 2, a flow chart 200 depicts various
`10 combinations of a method, according to various embodi(cid:173)
`ments of the present invention, for calculating propagation
`loss of a signal. The flow chart is implemented by way of a
`computer program in computer system 100. To begin the
`propagation loss calculation, several information parameters
`15 must be retrieved from databases accessible by computer
`system 100. These information parameters are: a transmitter
`location 202, a receiver location 203, an elevation profile
`204 of the signal propagation environment between loca(cid:173)
`tions 202 and 203, and a clutter profile 205 of the signal
`20 propagation environment between locations 202 and 203.
`These information parameters 202-205 may be retrieved in
`any logical order without departing from the scope of the
`present invention. At step 206, depending on a user
`selection, the computer program decides whether to modify
`25 elevation profile 204 before it passes to a next step. If the
`decision is positive, elevation profile 204 is modified in 207
`according to clutter profile 205. After modification in step
`207, a modified version of elevation profile 204 passes to
`step 208. Otherwise, if the decision at step 206 is negative,
`30 elevation profile 204 without any modification passes to step
`208. At step 208, depending on a user selection, the com(cid:173)
`puter program decides whether to modify elevation profile
`204 according to a first environmental factor (El). If deci(cid:173)
`sion step 208 is positive, El factor is calculated at step 209.
`35 The details of calculating El are explained in the following
`paragraphs. The elevation profile received at step 208 is
`modified according to El value calculated in step 210. The
`modified elevation profile at step 210 passes to step 211.
`Otherwise, if the decision at step 208 is negative, the
`40 elevation profile received at step 208 passes to step 211. At
`step 211, a preliminary path loss 218 of a signal propagated
`from transmit location 202 and received at receiver location
`203 is calculated using a standard path loss calculation
`method based on the elevation profile received at step 211.
`45 Other terrain information parameters may be involved in
`calculating path loss at step 211, however, they are not
`shown here. Several methods for calculating path loss at step
`211 are available and have been described fully in published
`literature. Few such methods are Longley-Rice, Durkin's,
`50 and Hata; these methods are described in a book titled:
`Wireless Communications: Principles and Practice, by The(cid:173)
`odore S. Rappaport, IEEE Press, pp. 110-120.
`After path loss 218 is calculated, a decision, according to
`a user selection, is made in step 212 whether to modify path
`55 loss 218 based on clutter information 205. If the decision is
`positive, path loss 218 is modified at step 213 based on
`clutter information 205, and the modified path loss at step
`213 passes to step 215. Otherwise, if the decision at step 212
`is negative, path loss 218 without modification passes to step
`215. Next at step 215, a decision is made according to a user
`selection whether to modify the path loss received at step
`215 according to a second environmental factor (E2). If the
`decision at step 215 is positive, E2 is calculated at step 214,
`and the received path loss at step 215 is modified according
`to a value of E2 calculated at step 216. The modified path
`loss at step 216 passes to a final step 217 for outputting a
`completed path loss calculation 220. Otherwise, if the deci-
`
`Ex. 1025 / Page 6 of 9
`
`

`

`US 6,289,203 Bl
`
`6
`from the scope of the present invention. The size, shape and
`relationship of subregion 350 containing receiver 303 loca(cid:173)
`tion may be modified, in certain geographical situations, to
`place edge 351 at a furthest location from transmitter 302
`5 and nearest to receiver 303. Subregion 350 is divided into a
`number of tiles, such as 360, 361, 362, and 363. A nominal
`size of a square tile is approximately 100 m on a side.
`However, other tile shapes and sizes may be used. Each tile
`is evaluated according to a road that lies within the tile. If
`10 more than one road is contained within a tile, the largest road
`is used for evaluating the tile. To evaluate a tile is to assign
`a reference number to the tile. The reference number is
`selected according to the CFCC road classification of the
`road lying in the tile. For example, tile 360 does not contain
`15 any road, therefore, it is assigned a tile reference number
`equal to zero. Tile 361 contains road class 330, a road class
`of 2 according to CFCC, representing a secondary and
`connecting road, therefore, it is assigned a reference number
`equal to two. Tile 362 contains a road class 340, a road class
`20 of 1 according to CFCC, representing a primary highway,
`therefore, it is assigned a tile reference number equal to one.
`Tile 363 contains a road class 311, a road class of 4
`according to CFCC, representing a residential road class,
`therefore, it is assigned a tile reference number equal to four.
`25 Although a CFCC classification system is followed here,
`any other type of classification system may equally be
`substituted.
`Generally, El or E2 may be represented by a summation
`as follows:
`
`a*f(RD)+b*f(PD)+c*f(RC)+d*f(RO),
`
`where a, b, c and d are weighting factors. The weighting
`factors are specified by a user to scale contribution of each
`35 parameter in the summation. The f(RD) is a predefined
`function of the road density (RD). RD defines a percentage
`number of tiles in subregion 350 that contains a road. The
`f(RD) is represented by:
`
`5
`sion at step 215 is negative, the received path loss at step 215
`passes directly to final step 217 for outputting a completed
`path loss calculation 220.
`To calculate El or E2, informations about transportation
`networks, such as roads, railways, waterways and alike,
`which are laid out in the signal propagation environment are
`needed. Normally, such networks are at or near the surface
`of the earth. In addition, information about population
`density of the signal propagation environment may be
`needed when calculating El or E2. Databases describing
`transportation networks and population densities of various
`areas are readily available. Moreover, these databases are
`easily and inexpensively updated. According to one advan(cid:173)
`tage of the present invention, use of such inexpensive and
`updated databases for calculating a propagation path loss
`involving El or E2 eliminates, or reduces, a need for
`updating clutter information which is expensive and time
`consuming to obtain. In the event that an off-the-shelf
`database for the transportation network is not available due
`to unimportance of the remote or undeveloped area, a road
`map of the area may be used to generate the transportation
`network database. Generating a transportation network data(cid:173)
`base is much easier than generating a clutter information
`database.
`El or E2 is a function of road density (RD), population
`density (PD), road category (RC), and road orientation (RD)
`parameters. Summation of RD, PD, RC and RD, while
`multiplying a weight factor to each parameter, produces El
`or E2. Although the weight factors or value of parameters
`may be different for El and E2 calculations, a process of 30
`calculating El is equally applicable to a process of calcu(cid:173)
`lating E2.
`Referring to FIG. 3, a transportation network is illus(cid:173)
`trated. A transportation network may include many different
`categories of transportation networks such as roads,
`waterways, and alike. Furthermore, each category of trans(cid:173)
`portation network may be divided into many classifications.
`For example, the Census Feature Class Code (CFCC) clas(cid:173)
`sification system, available from the United States Geologi-
`cal Survey, provides approximately 44 different classifica- 40
`tions of roads. Primary highways with and without limited
`access, secondary and connecting roads, local and neigh(cid:173)
`borhood roads are several examples of such road classifi(cid:173)
`cations. FIG. 3 depicts a road network 300 which is com(cid:173)
`prised of a number of small roads 320, generally indicating 45
`a residential road class, a number of medium sized roads
`330, generally indicating a secondary and connecting road
`class, and a large road 340, generally indicating a primary
`highway class. It may be observed in FIG. 3 that each road
`class is shown by a different line thickness.
`A subregion 350 is selected for further analysis of the
`transportation network between a receiver location 303 and
`a transmitter location 302. Subregion 350 at least includes
`receiver 303. Receiver 303 may be a cellular mobile
`receiver, and transmitter 302 may be a cellular base station 55
`in a cellular communication system. Subregion 350 lies
`primarily along a signal propagation path between transmit-
`ter 302 and receiver 303. Subregion 350 is selected such that
`receiver 303 lies generally at an edge or near an edge of an
`area defined by subregion 350. An edge 351 is shown to be 60
`the nearest edge to receiver 303. Also, edge 351 of subregion
`350 is on a side of subregion 350 that is furthest from
`transmitter 302. It is envisioned that the size, shape and
`relationship of subregion 350 containing receiver location
`303 may be modified to account for terrain fluctuations or 65
`unique properties, such as non-uniform road categories or
`population densities of subregion 350, without departing
`
`j-k*RD,
`
`where j and k are predefined constants. The f(PD) defines a
`predefined function of a population density (PD) of subre(cid:173)
`gion 350. The population density PD may be defined accord(cid:173)
`ing to a time of day, and is normally in unit of people per unit
`area. The f(PD) is represented by:
`
`n-m*PD,
`
`where n and m are predefined. The f(RC) is a predefined
`50 function of a road class (RC) of a tile where the receiver is
`located. The RC is the evaluated road class assigned to tile
`361. If RC value is greater than or equal to a constant "p"
`and less than or equal to a constant "q", f(RC) is equal to a
`constant "r", otherwise, f(RC) is equal to a constant "s". The
`constants p, q, r and s are predefined. The f(RO) is a
`predefined function of a road orientation (RO). Each
`receiver, such as receiver 303, normally is located on or near
`a road as shown in FIG. 3. The road near receiver 303 would
`have an orientation angle, theta, 370 with respect to a line of
`signal propagation from transmitter 302 to receiver 302. The
`f(RO) is represented by:
`
`t*cos(theta),
`
`where t is a predefined constant.
`To calculate El, the constants in f(RD), f(PD), f(RC), and
`f(RO) are in units of height, such as meter or feet; and to
`calculate E2, the constants are in unit of decibels.
`
`Ex. 1025 / Page 7 of 9
`
`

`

`US 6,289,203 Bl
`
`7
`Accordingly, El modifies an elevation profile in units of
`height, and E2 modifies a propagation loss in units of
`decibels.
`The values of a, b, c, and d, are generally specified for a
`given range depending on the characteristics of the coverage 5
`area. They may also be a function of the values stored in the
`clutter database for the location being evaluated. The values
`for a, b, c and d, are designed to adjust contribution of each
`parameter in El and E2. Based on some actual field
`measurements, the values of a, b, c, and d are adjusted to
`achieve the minimum root mean squared (rms) error for the
`propagation prediction of multiple locations throughout a
`test area. Adjusting or tuning parameters in this way to
`achieve the best (rms) fit to actual measurements is a well
`known engineering principal. As such, it is expected that the
`a, b, c, and d values be different for different areas depending 15
`on the nature of the environment, the density of the city, and
`the size of the roads, and alike. Once a, b, c, and d values are
`determined for different area, they may be stored in a table.
`In some cases, for example, the population data 110 may not
`be available in certain country. Thus, the value for b may be 20
`set to zero, so that the contribution from f(PD) would be
`equal to zero in calculating El or E2. The values for a, b, c,
`and d for calculating El and E2 may be different.
`A computer program based on various embodiments of
`the present invention may be incorporated in a simulation
`tool predicating a cellular communication system coverage
`area. Such tools, normally, predict signal propagation path
`loss between a base station and various mobile units in the
`coverage area. As such, a communication system designer is
`able to determine the number of users that may be served in 30
`the coverage area before base station installation takes place.
`Moreover, as various objects, such as homes, buildings,
`bridges and roads are erected or demolished in the coverage
`area, the system designer is able to maintain the communi(cid:173)
`cation system efficiency by assuring adequate service to the 35
`users by continuously adjusting the system capacity based
`on the simulation results. A computer program known as
`Netplan is available from Motorola Inc. that performs propa(cid:173)
`gation simulation. Information about Netplan is available by
`contacting Motorola Inc. Technical Education & 40
`Documentation, 1501 West Shure Dr., Suite 3223A, Arling(cid:173)
`ton Heights, Ill. 60004. The computer program in Netplan
`executing methods of various embodiments of the present
`invention allows the communication system designers a
`better system planning without resorting to expensive, and 45
`often times inaccurate, clutter information. Simulation
`results show at least 10% improvement in predicting cov(cid:173)
`erage areas when the system is planned by Netplan incor(cid:173)
`porating various embodiments of the present invention.
`While the invention has been particularly shown and 50
`described with reference to a particular embodiment, it will
`be understood by those skilled in the art that various changes
`in form and details may be made therein without departing
`from the spirit and scope of the invention. The correspond(cid:173)
`ing structures, materials, acts and equivalents of all means or 55
`step plus function elements in the claims below are intended
`to include any structure, material, or acts for performing the
`functions in combination with other claimed elements as
`specifically claimed.
`What is claimed is:
`1. A method for determining a final propagation loss of a
`signal transmitted from a trnmitter and received at a receiver
`located in a proximity of a road in a predefined area,
`comprising the steps of:
`calculating a first environmental factor based on a trans- 65
`portation network information associated with said
`predefined area; and
`
`8
`determining said final propagation loss based on said first
`environmental factor.
`2. The method as recited in claim 1 wherein the step of
`determining said final propagation loss, said determining is
`further based on an elevation profile of said predefined area
`which is modified according to said first environmental
`factor.
`3. The method as recited in claim 1 further comprising the
`step of calculating a second environmental factor, and
`wherein the step of determining said final propagatio