AU8929198A - Method for estimating cell covering in wireless network planning system - Google Patents

Description

If AU98B929 1 (12) PATENT ABSTRACT (11) Document No. AU-A892 9 l /98 (19) AUSTRALIAN PATENT

OFFICE

Title METHOD FCG. ESTIMATING CELL COVERING IN WIRELESS NETWORK PLANNING

SYSTEM

International Patent Classification(s) (51)6 H040 00 7 /36 H04B 007/ 2 6 (21) Application No.: 8 9291 /9B (22) Application Date: 14/10/98 priority Data (31) Number (32) Date (33) Country 9752952 15/10197 KR REPUBLIC OF KOREA 9777205 29/12/97 KR REPUBLIC OF KOREA (43) Publication Date:- 06105199 (71) Applicant(s) KOREA

TELECOM

inventor(s) jIN $00 PARK; YOUNG HO BAE; WON TAlK HWANG; YOUNG HEE SHIN; HYUN MEEN JUNG;

MI

YOUNG JEONG; JUN CHiUL KIM; YEONG KWUN

KIM

(74) Attorney or Agent CULLEN CO, GPO Box 1074, BRISBANE OLD 4001 (57) Method for estimuatin~g cell coverage applied in a wirelessnetwork planning system, the method includes the Steps of' a) searchinlg LOS (Line Of Sight) path for a plUrality of radials with reference to geographical information; b) connecting all LOS points anid findirig cell uoverage area; and c) displaying the cell coverage. Using the method for estimating cell coverage as described above, a calculation time is considerably saved. Also, a much more accurate estima~~tionl value can be obtained within a certain calciilation time in comparison with a conventional estimation algorithm of cell coverage.

3

N

,I i~

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT .4

V..

r~.

Name of Applicant: Actual Inventors: Address for Service: Invention Title: KOREA TELECOM Jin Soo PARK, Yeong Kwun KIM, Jun Chul KIM, Mi Young JEONG, Hyun Meen JUNG, Young Hee SHIN, Won Taik HWANG, Young Ho BAE CULLEN CO., Patent Trade Mark Attorneys, 240 Queen Street, Brisbane, QId. 4000, Australia.

METHOD FOR ESTIMATING CELL COVERAGE IN WIRELESS NETWORK PLANNING SYSTEM The following statement is a full description of this invention, including the best method of performing it known to us MTHOD Ro !ESTIXhTING CELL C1OTEPAGE f IEESNTO PLhNNING

SYSTEM

BACKGROUM OF THE INVEINT

ION

1Technical Field of the Invention The present inivention relates to a mesthod for planning a wireless network, more particularly relates to a method for 'j.

estimating cell coverage applied to a wireless network planning 0 system, which. improves calculation speed of propagation analysis.

2. Descriptionl of the Prior Art First of all, to diefinition of the key words used in this invention, LOS (Line Of Sight) indicates such a condition that there is no barrier on the straight propagation line of wireless signal GIS- (Geographical Information System) gives a general name to systems for handling the informfations of natural and geographical f eatures in order to effectively manage FX (Facilities management) and geographical informations, which are mostly handled in forms of digital because they are planned and managed by use of comTputers.

GIs for wireless network planning must include the Informrations for natural and geographical features and, especially, be to handle informations for locations5, altitudes, directions, materials and etc. of structures -and Morphology of natural and geographical features.

DTH (Digital Terrain M~odel) is a geographical model resulted from digitalized geographical profile represented by numerical value. Specifically, this is a geographical data model in which the value above the sea level dnd property informations are stored at an interval of lattice which is composed of appropriate intervals according to the use.

Cell Coverage means area to which a wireless base station(hereiflafter is referred to base station) provides its s ervices, which can be illustrated, as shown in Fig. 1, as a circle having radius d centering around the base station when using an omnidirectional antenna. However, the real shape of cell coverage has irregular shapes due to the geographical and structural features. As the wireless signal propagates away from the base station, the strength of the wireless sign~al becomes weak. So, A there is a point that, it may not be pbssible to communicate due to the weakened signal strength. That point is the border of the cell coverage.

Cell planning is, as shown in Fig. 2, to make any regions within the service areas provided with services by one or more .J stations by properly arranging certain base stations in all regions to provide wireless communication services (personal communication services mobile com~municationl services, CT-2 services) on the basis of the analysis of cell coverage for each base stationi.

2 IM1 i ":20 At this time, the distance between base stations had better be maximumly longer because the fewer the base stations necessary to cover the service areas become, the more the investment fees may be saved. On the contrary, too excessively long distance between base stations may occur the shadow of communication and have the communication impossible. Therefore, the best location of the station has to be decided through precise analysis of the cell coverage a station handles. Generally, the analysis of cell coverage by a base station takes an advantage of wireless network planning system, which presumes, through by GIS data, the received electric field intensity of each area.

Most wireless network planning systems, which are currently under general use for wireless common carriers, provide essential functions for wireless analysis, but there is an essential problem of covering a great amount of analysis time. That is, a method for analyzing a precise cell coverage for each base station by use of wireless network planning system generally needs very much time.

Therefore, in the case of necessity of deciding the rough location of cell site unnecessary, time and functions are spent. Under such a circumstance, much faster estimating method of rough cell coverage has been required.

Fig, 3 is a view of explaining general propagation analysis and Bin. The prior method for estimating cell coverage will be described with reference to Fig. 3.

In a method for estimating cell coverage, implemented in most wireless network planning system currently used, an area having a fixed calculation radius 31 is divided into small regular square 32, what is called Bin, which is an essential unit of received electric power estimation. The value of received electric power at the center point of the Bin represents the whole area of the Bin. Accordingly, the smaller the Bin is, the more precise coverage may be obtained. However, there is a defect that the speed of calculation becomes slower. To sum up, smaller Bin is helpful of obtaining more precise coverage, but the calculation speed may be :10 slower. The size of Bin is determined by user and then the precision and speed of prediction is also decided.

The calculation of each Bin first establishes Radial 33 over 360" all directions at close angles, passing all Bins and calculates received electric field intensity for all Bins over each Radial. For example, as for the Bin over Radial 5 of Fig. 3, the i received electric field intensity for all Bins over Bin 1 to Bin 35 is calculated. At this point, received electric field intensity for each Bin may be obtained by using GIS data and wireless propagation models provided from system.

20 As such calculations for all radials are repeated, it is possible to obtain all received electric field intensity for all Bins within the calculation radius dx. Each communication system has the minimum required power P, for the successful communicaiton. Comparing such minimum received electric power P, /I 4 i, n: '6Ci i.F

:L

A

4.

A-

with the calculation value of received electric field intensity for each Bin, Bin area having the value more than Pn, forms cell coverage.

Since, in the prior cell coverage estimating method as above, intention to obtain precise cell coverage makes unnecessary calculation of all Bins within the calculation radius, very much processing time is also spent even in case the only rough cell coverage is required. Meanwhile, it is helpful to make the size of Bin bigger for faster execution, but there was a defect worsening the precision of cell coverage. Accordingly, the prior method for estimating cell coverage might not be appropriate to use at the time of the calculation of rough cell coverage.

Fig. 4 is a view of specifically illustrating the prior wireless interpretation method.

As shown in Fig. 4, the prior wireless interpretation method comprises of the steps of: Reading GIS data (DTM, vector) at step 41; calculating the received signal for each Bin within the fixed area as shown in Fig.3 at step 42; and displaying the service area on screen at step 43.

In the case of wireless network planning by use of the prior wireless analysis as above, there were much difficulties in management such as subsequent rearrangement as well as a lot of time is spent on the wireless network planning.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for roughly estimating cell coverage in advance by LOS (Line of Sight) for improving the calculation speed of wireless interpretation function implemented in wireless network planning system.

In addition, further object of this invention is to provide a method for roughly estimating cell coverage in advance by using optional search algorithm, such as bi-section search algorithm, and calculating received signal electric power only for the minimum Bin necessary for the calculation of cell coverage in order to improve the calculation speed of the wireless interpretation function implemented in the wireless network planning system, not by calculating received signal electric power for all Bins corresponding to each Radial.

According to the first aspect of the present invention, this object is accomplished by providing a method for estimating cell coverage applied in a wireless network planning system, the method including the steps of: a) searching LOS (Line Of'Sight) path for a plurality of radials with reference to geographical information; b) connecting all LOS points and finding cell coverage area; and c) displaying the cell coverage.

According to the second aspect of the present invention, this object is accomplished by providing a method for estimating cell converge applied in a wireless network system, the method including the steps of: a) searching cell coverage Bin over a plurality of radials using search algorithm after setting parameters necessary 6

M

for estimation of cell coverage b) connecting all cell coverage Bin and finding cell cover-age areal and c) displaying said cell noverage area.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects anid aspects of the invention will become apparent -from the following description of the embodiments with reference to the accompanying drawings in which.

:Iio Fig. 1 is a vieii of explaining general cell coverage; Fig. 2 is a -view of explaining general wireless networkc *planning; fig. 3 is a view of explaining general wireless analysis and Bin.

M 15 Fig. 4 is a view of specifically illustrating the prior wireless interpretation-method; Fig. 5 is 'a block diagram of a wireless network planning KA system to which an embodiment of the present invention ia applied; Fig. 6 is an~ exemplary diagram illustrating an method for searching LOS for each radial in accordance with the present invention; Fig. 7 is a flow chart illustrating a method for estimating cell coverage in accordance with the present invention; Fig. 8 is a -exexnplary diagram illutrating a method for estimating cell coverage for another embodiment of the present 7 Lj Invent ion; Fia.9 isa flow chart illustrating a method for estimating cell coverage in aczardance with another embodiment of the present invention; and Fig. 10 is a flow chart illustrating a miethod for estinating cell coverage in accordance with still another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EM4BODIME~NTS The embodiments of the present invention will be described *with reference to the accompanying drawings.

Fig. 5 is a block diagram of a wireless network planning system to which an embodiment of the present invention is applied.

The wireless network planning system~ comprises a computer 51, an input device 52 such as a moube, and output devices 53 such as a printer and a plotter. An estimation method in accordance with the present invention is loaded and run on the computer 51, Fig. 6 is an exemplary diagram illustrating an method for searching LOS for each radial in accordance with the present invention.

First, we assume that we want to search LOS for each radial clockwise centering around an base station S. On the same radial, when signals travel from a center of the base station S to outside, the length is referred to a LOS path between the base station S anid 8 a fi Irst building of which height is higher than that Of the base Station S.

I LOS is satisfied, the correspondinlg Bin is recognized as a servir~e area. A~nd then the same operation is performed for the othjer radials Wtaen the search operations for all radialis are cdlapieted, Bins Iwhich satisfies LOS path can be found. At this -time,- a a servi.ce area is an inner area consisting of these Bins.

celFig. 7 is a flow chart illustrating a method for estimating cel overage in accordance with the present invention.

O Firsitj the process reads GIS data at step 71 an~d determines whether LOS path searches for all radials are completed at step 73 after searching LOS path for the first radial at step 72. If the C. searches are omipleted, the process connects all LOS points at step 76 and finds and displays a desired cell coverage area at step 77.

Or, the other hands, if not, the process stores the searched

LOS

paths at step 74 and sets a next radial and continues to the step 72 which searches LOS path for the next radial.

rig. 8 is a exemplary diagram illustrating a method for estimating cell coverage for another embodiment'of the present inventionl.

As illutrateO- in Fig. 8, the power of the received signal 4 decreases as waves travels far. Even thouigh the selecting point may be different according *to searching algorithm, first, a point is selected between the base station and a maximal calculation distance in this enibodirnenti the bi-secti~fl searching algorithm is used as a searching algorithm- Using the bi-sectiofl searching alcgorithm, a middle point i5 selected. The received power of the Bin correspondOinlg to the middle point 81 is computed.

if the received power Pai is much higher than the minimum power PWA which is minimum power necessary for communication, another point 82 is selected between the point 81 and the maximal ca.lculatio distance d1~ Using the bi-section searching method, the point is a middle point between the two points 81 and The :'IO received power Pu, of the Bin correspondingq to the middle point 82 is computed.

if the received power Paj, is lower than the minimum power p,, wihich is minlimum~ power necessary for communicatiOn, another point 83 is selected between the two P~oints 81 and 62. The received power is of the B~in corresponding to the middle point 83 is computed.

After repeat of operations as described above, a point 85 of

I

4Wwhich power is similar to the minimum power P.L. At this timt, distance between the base station S and the point 85 is cell coverage.

20 -Using the method for estimating cell coverage as described above, since the calculation of received power for all Bins between the base station and the maximal calculation distance d, is not necessary, a calca.lation' time is considerably saved. Also, a much more accurate estimation value can be obtained within a certain calculation time in comparipaon with a co .5entioflal estimation Z7 AR4 Fig 9 is a flow chart illustrating a methdfo tiltfg inventil oetmtr of celoverager suhawh aia aclto the nuet frai at Step 91. Then the pro~Scness seorhe atep Terces dthe Bin. wnether selechtidnsiffthinselertiol fi-rt radial to the last radial are com~pleted, the process connctsthe selected Bins at step 96 and display cell coverage aeatstep 97.

1is a flow chart iilustratin4 a method for estimating el cverage in accordance with still another emubodiment of the 20 reetinvention. Fig. 10 is a flow chart illustrating the detail proessof the step 92.

First, a point is aeiected between the base station S and the Mr maximal calculation distance using the search method at step 101. The proCes aluae te received Power Pji of the corr -espondilg Bin of the selected point and dif ference valUe 11 between the received power Pu, and the minimum received Power Pmin at steps 102 and 103.

Then the process determines whether the difference value is smaller than a threshold value at step 104. If not, a point between points previously selected using the search method at step 105. Tile process continues to the step 102 which calculates the received power of the Bin corresponding to the selected point. On the other hand, if so, the process set the distance between the base station and the corresponding point as a cell coverage at step 106.

O Although the praierred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are-possible, without departing from the soope and spirit of the invention as disclosed in the accompanying claims.

12

Claims (7)

1. A method for estimating cell coverage applied in a wireless network planning system, the method including the steps of: a) searching LOS (Line Of Sight) path for a plurality of radials with reference to geographical information; b) connecting all LOS points and finding cell coverage area; and c) displaying the cell coverage.

2. A method as claimed in claim 1, wherein said step a) includes the steps of: d) searching LOS path for the first radial; e) determining whether search of LOS paths for all of said plurality of radials are completed; and f) storing the searched LOS path, setting a next radial and S restarting said step d) if the LOS search are not completed.

3 A method for estimating cell converge applied in a wireless network planning system, the method including the steps of: a) searching cell coverage Bin over a plurality of radials using search algorithm after setting parameters necessary for j estimation of cell coverage; Sb) connecting all cell coverage Bin and finding cell coverage area; and 113 *i 'f^ i iI 10 c) displaying said cell coverage area.

4. A method as claimed in claim 3, wher~ein the 'step a) includes the steps of: d) setting paramneters necessary for estimation of cell coverage using the search algorithm; e) searching cell coverage Bin over the first radial; f) determining whether selection of cell coverage Bins over all of said plurality of radials are completed; and g) storing the c~rresponding cell coverale Bin, setting a next radial and proceeding said step if the LOS search are not completed.

A method as claimed in claim 4, wherein the step a) includes the steps of; h) selectinlg a point between a base station and a maximal calculation distance u~sing the search algoritbm; i) calculating a received power of a Bin corresponding to the selected point; j) determining whether difference value between a calculated received power and a minimnum received power necessary for communication is lower than a threshold value; k) proceeding to the step i) after selecting another point betweerL points previously selected, if the difference value is not lower than the threshold value; and 14 k 1) setting distance between the base station and the corresponding point as a cell coverage, if so.

6. A method a5 claimed i~n claim 4, wherein the search algorithm ia bi-section algorithm.

7. A method as claimed in claim 4, wherein the par'ameters includes a maximal calculation distance a minimum received power Pmin, a size of a Bin and the num~ber of radials. DATED this 14th day of October 1998 KOREA TELECOM By their Patent Attorneys CULLEN CO. AA