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FOR PUBLIC
In the name of Knowledge Outsourcing
“ LET EVERY ONE GROW ”
Publisher : DINENDRAN S
Email@ [email protected] Copywrite@ dinendran.wordpress.com
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GSM Planning & Engineering.
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GSM Reference Model
A
MSMS BTS BSC
Um Abis
MSC HLR
EIR
VLR
AuC
VLROMC
MSC PSTN ISDN
E
FC
B D
G
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General Planning ProcessMobility and traffic models
for the considered areaEquipment quantity
(BTS, BSC, MSC, links, ...)
Sites positioning
(radio planning)BTS layout andcharacteristics
Frequency plan
Frequency
allocation
Dimensioning
(Erlang, QoS)
BSS design(site positions and
interconnection network)
NSS, IN, WAP design (equipment positions and interconnection network)
Global network design
interconnection
BSCs and MSCsBTSs and BSCs
interconnection
Interconnection with
other networks
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Planning Process• Business Plan• No. of Subscribers• Traffic per subscribers• Subs distribution• GOS• Spectrum availability• Frequency Reuse• Types of coverage• RF parameters• Field strength studies• Available sites• Site survey
• Business Plan• No. of Subscribers• Traffic per subscribers• Subs distribution• GOS• Spectrum availability• Frequency Reuse• Types of coverage• RF parameters• Field strength studies• Available sites• Site survey
CapacityStudies
CapacityStudies
Coverage &C/I study;Search Areas
Coverage &C/I study;Search Areas
• Plan Verification• Quality Check• Update documentation
• Plan Verification• Quality Check• Update documentation
Initial DesignPlan
ImplementationPlan
ImplementationMonitorNetworkMonitorNetwork
Network OptimisationNetwork
Optimisation
• Capacity Studies• Coverage Plan and Coverage Studies• Frequency plans and Interference Studies• Antenna Systems& Orientation Studies• BSS parameter planning• Database and documentation of approved sites• Expansion plans
• Capacity Studies• Coverage Plan and Coverage Studies• Frequency plans and Interference Studies• Antenna Systems& Orientation Studies• BSS parameter planning• Database and documentation of approved sites• Expansion plans
****
****
Acquisition of Sites
Acquisition of Sites
and re-design
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GSM PLANNING: THE BASIC PROCESS
1. CAPACITY PLANNING
2. COVERAGE PLANNING
4. EQUIPMENT PLANNING
3. PARAMETER PLANNING
5. OPTIMIZATION.
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CELLULAR MOBILE RADIO SYSTEM DESIGN
• Concept of frequency reuse channels• Co-channel interference reduction factor• Desired carrier to interference ratio• Hand off mechanism• Cell splittingNote:Limitation in the system is the frequency
resource
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CELLULAR MOBILE RADIO SYSTEM DESIGN
Challenge is to serve the greatest number of customers
1.How many customers can we serve in a busy hour ?
2.How many customers can we take into our system?
3.How many frequency channels do we need?
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GSM NETWORK PLANNING PROCESS - I
• Service Area• Estimation of traffic demand• Available frequency resources.• Evolving an optimum coverage scheme
of placing the cells over the entire service area so as to provide complete mobility to the subscribers.
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GSM NETWORK PLANNING PROCESS- II
• Traffic demand estimation-Population distribution-Car usage distribution-Income level distribution-Land usage distribution-Telephone usage distribution.
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GSM NETWORK PLANNING PROCESS-III
• Estimation of Cell Radius– Service Area
• Terrain conditions• Density of foilage • Man made structures
– Signal level at an unit distance from base station
– Signal strength decay per decade of distance.
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GSM NETWORK PLANNING PROCESS-IV
• MOBILE RADIO NETWORK PLANNING SOFTWARE TOOLS– Propagation Predictions based upon various
propagation models e.g OKUMARA- HATA, WALFISCH-IKEGAMI or special external models written by the users
– Interference analysis – Automatic frequency planning – Coverage analysis by contour plots– Comparison with actual radio field measurements– Efficient tool to load,analyze and display system
performance evaluation
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Traffic ModelCall Mix for other services• FAX/DATA subscribers - 5% in 40mE cities
and 2% in other cities.• IN subscribers - 70% of total subs
– Prepaid subscribers - 80% of IN subs– Freephone (FPH) - 5% – MVPN - 5%– Premium Rate (PRM) - 5%– Universal Access No. - 5%
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Traffic Model
• Voice Mail - 100% of subscribers.• SMSC should be dimensioned for 50% of the
total subscribers with:– 2 messages per subscriber per day– Max. length of SMS message 160 chars.
• WAP subscribers - 10% for high traffic cities and 5% for others with:– 50% on Circuit Switched Data (CSD)– 50% on SMS
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Design Parameters
• Grade of Service– MSC-MSC/PSTN - 1%– MSC-BSS - 0.5%– Um interface - 2%– BSC-BTS - 0%
• Handover– Total HO - 50%– Inter MSC - 5%– Inter BSC - 10%– Intra BSC - 85%
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Design Parameters
• Location Update– Normal
• Intra MSC (New LAI) - 0.3 nr/sub• Intra MSC (new registration) - 0.18 nr/sub
– Periodic - 0.5 nr/sub– Attach
• Subscribers registered earlier - 0.25 nr/sub• New registration - 0.1 nr/sub
– Detach
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GSM Cell Planning Requirement
• Provision of required Capacity
• Optimum use of the available frequency spectrum
• Minimum number of cell sites
• Provision of easy and smooth expansion of the network in future
• Provision of adequate Coverage of the given area, for a minimum specified level of interference
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Example : Basic Planning (1/3)• Say the service provider wants to launch his network
with 20 sites or for 10,000 subscribers in a city• The following assumptions are made in the planning process :• 25 mE average traffic per subscriber• Grade of Service 2%
• Mobile to Mobile traffic 10%
• Mobile to PSTN traffic 70%
• Land to Mobile traffic 20%
• Average call duration 90 seconds
Contd..
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Example : Basic Planning (1/3) contd….
Traffic capacity of 1 carrier with 7 TCHs = 2.94E(approximately 120 subscribers ); a 1/1/1 site will have capacity of approximately 350 subscribers.
Traffic capacity of 2 carrier with 15 TCHs = 8.2E (approximetly 330 subscribers). A 2/2/2 site will have a capacity of about 990 subscribers.
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Example - Basic Planning (2/3)Case 1: For specified number of sites (20)
• 1/1/1 sites (350 subs per site) … 7000 subscribers.
• 2/2/2 sites (990 subs per site) … 19800 subscribers.
Case 2: For specified capacity requirement (10000)
• 1/1/1 sites….10000/350 …. 30 sites.
• 2/2/2 sites….10000/990 …. 11sites.
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For 10000 capacity, at 25mE traffic, the total traffic is 250E. We assume a hypothetical distribution of traffic as shown below:
• We may choose 2/2/2 sites for first 3area types and 1/1/1 sites for the rest.
• This makes a total of 18 sites. After customer’s approval,site selection is done.
Example - Basic Planning (3/3)
Area Type % tfc tfc 1/1/1 2/2/2Urban high density 20 50E 6 2
Urban 30 75E 10 3
Industrial 15 37.5E 5 2
Suburban 25 62.5E 7 3
Highways 5 12.5E 2 1Quasi open 5 12.5E 2 1Total 100 250E 32 12
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Cell Planning (1/2)• What is the area to be covered ?• How many sites are required for this area ?
(cell radius of 1km means an approximate coverage area of 3 Sq.kms).
• Do we need so many sites? Can some sites be bigger?
• Decide number of sites based on capacity and coverage requirements.
• Divide city into clutter types such as: > Urban> Suburban> Quasi Open> Water.
• Identify “search areas” covering all clutter types.• Customer selects a few sample sites.
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Cell Planning (2/2)• Survey sites with reference to
> Clutter heights> Vegetation levels> Obstructions> Sector orientation> Building strength and other Civil requirements
• Prepare Power budgets• Conduct Propagation tests• Calculate coverage probabilities• Verify against predictions and modify planning tool
parameters
• Prepare final coverage map
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Cell Planning and C/I issuesAssume all cell are of the same sizeAll cells transmit the same power.
The path loss is not free space and is governed by the attenuation constant .
The reuse distance D and cell radius R are related to the C/I as given below:
(D/R) = 6 (C/I)
The C/I is in absolute value.
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SELECTING A PROPER CELLSITE
When a cell site is selected• Determine whether an UHF TV station is
nearby and whether any new ongoing construction would affect the coverage
• Check the local noise level and no spurious signals fall in the freq.band
• Existing multi-antenna tower can be used with proper earthing and shielding
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RF LINK DESIGN
Radio link design is one of the most important problem for design engineers
Fundamental parameters:1.Transmitted power2.Co-channel reuse design
In order to provide quality transmission ie.a specified bit error rate (BER) and allowable outage is decided.(outage is defined as the fraction of the service area over which the required transmission quality cannot be maintained within the service area)
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CELLULAR CONCEPTS-ESSENTIAL FEATURES
• Frequency reuse-refers to the use of radio channels on the same carrier frequency to cover different areas,which are physically separated from each other sufficiently to ensure that co-channel interference is not objectionable.
• Cell splitting-when the demand for service exceeds the number of channels allocated to a particular cell, cell splitting is used to handle the additional growth in traffic in within the particularcell.Cell splitting involves a revision of cell boundaries, so that the local area formerly regarded as a single cell can now contain a number of smaller cells.These cells are called micro cells.The transmitted power and antenna height of these base stations are correspondingly reduced and the same set of frequencies are reused.
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Freq Reuse & C/I Requirement
N D/R= 3N C/I= 10log(1/6(D/R)3.5
3 3.00 8.917 dB
4 3.46 13.29 dB
7 4.58 21.80 dB
9 5.19 25.62 dB
12 6.00 29.99 dB9
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CO-CHL INTERFERENCE
DR
A Multi Cell Environment
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Frequency Planning AspectsA1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3
1 2 3 4 5 6 7 8 9 10 11 1213 14 15 16 17 18 19 20 21 22 23 2425 26 27 28 29 30 31 32 33 34 35 36
A1A2
A3 B1B2
B3
D1D2
D3 C1C2
C3
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Traffic Capacity of Cells
Control CCHNo. of TRX No. of TCH
11 7
22 14
23 22
25mE SUBS SUPPORTED
TFC CAP IN ERLANG*
40mE SUBS SUPPORTED
1182.94 74
3288.20 205
59614.9 373
34 29
35 37
36 45
84021 525
113228.3 708
142435.6 890
* GOS AT 2%
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Traffic Capacity of BTS
* GOS AT 2%
No. of TRXBTS CONFGN
No. of CELLS
31-1-1 3
41-1-2 3
51-2-2 3
25mE SUBS SUPPORTED
No. of A-bisTS reqd.
40mE SUBS SUPPORTED
3549 221
56411 353
77413 484
62-2-2 3
72-2-3 3
82-3-3 3
98415 615
125217 783
152019 950
93-3-3 3
103-3-4 3
178821 1118
203223 1270
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Traffic Capacity of BTS ..contd..
* GOS AT 2%
No. of TRXBTS CONFGN
No. of CELLS
113-4-4 3
124-4-4 3
134-4-5 3
25mE SUBS SUPPORTED
No. of A-bisTS reqd.
40mE SUBS SUPPORTED
227625 1423
252027 1575
281230 1758
144-5-5 3
155-5-5 3
165-5-6 3
310433 1940
339636 2123
368838 2305
175-6-6 3
186-6-6 3
398040 2488
427242 2670
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Traffic Capacity of BTS ..contd..
* GOS AT 2%
No. of TRXBTS CONFGN
No. of CELLS
1Omni 1 1
2Omni 2 1
3Omni 3 1
25mE SUBS SUPPORTED
No. of A-bisTS reqd.
40mE SUBS SUPPORTED
1183 74
3285 205
5967 373
4Omni 4 1
5Omni 5 1
6Omni 6 1
8409 525
113211 708
142413 890
22000/2C 1
2HW 1-1 2
3285 205
2356 147
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A-bis Connectivity Types
Multi-drop configurationBSCMSC
Star configuration
BSCMSC
BSC
MSC
Ring configuration
BSC
MSCUrban star configuration
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Basic Planning• For 30000 lines @40mE traffic, the total traffic would be 1200E.
Assuming the IMPCS specification for traffic distribution:
TYPE OF AREA % OF TFC
URBAN INDOOR 40%
URBAN INCAR 40%
URBAN OUTDOOR 20%
1/1/1TFC IN ERLANG* 2/2/2
54480 E 20
54480 E 20
27240 E 10
TOTAL 100% 1271200 E 50
6/6/65/5/5
57
57
33
1317
• Decision on choice of BTS type and TRX configuration is very crucial to provide the specified capacity and coverage
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Coverage Model
• Indoor Coverage: – Commercial areas, airports, etc
• In-car coverage– Residential areas, industrial areas, roads, all
national/state highways, by-passes and important rail routes, etc.
• Outdoor coverage– Remaining areas of the coverage area.
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Coverage Model
HIGH TRAFFIC CITIESCOVERAGE OTHER CITIES
40%INDOOR 25%
40%INCAR 40%
20%OUTDOOR 35%
TRAFFIC DENSITY
SIGNAL LEVEL MEASURED AT STREETCOVERAGE
SHOULD BE BETTER THAN -75 dBmINDOOR
SHOULD BE BETTER THAN -85 dBmINCAR
SHOULD BE BETTER THAN -95 dBm IN 90% OF TOTAL COVERAGE AREAOUTDOOR
SIGNAL LEVEL FOR 95% OF THE TIME FOR THE COVERAGE
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Coverage Planning
• Involves designing two aspects of Radio:– Link Budget– Power Balance
• LINK BUDGET brings out whether the uplink or the downlink is the limiting factor for coverage.
• POWER BALANCE ensures that the coverage of DL is equal to that of UL
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RADIO LINK ANALYSIS
• ‘Link budget’ or ‘link power budget’ is the totalling of all the gains and losses incurred in operating a communication link.It provides a detailed accounting of three broadly defined items:
1.Apportionment of the resources available to the transmitter and the receiver
2.Sources responsible for the loss of signal power3.Sources of noise
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RF LINK BUDGET UL DLTRANSMITTING END MS BTS
Tx RF Output 33 dBm 43 dBmBody Loss -2.0dB 0dBCombiner Loss 0dB 0dBFeeder Loss (@2dB/100m) 0dB 1.5dBConnector Losses 0dB 2dBTx Antenna Gain 0dB 17.5dBEIRP 31dBm (A) 57dBm ( C)
RECEIVING END BTS MS
Rx sensitivity -107 dBm -102 dBm
Rx. Antenna gain 17.5dB 0dBDiversity Gain 3dB 0dBConnector Loss 2dB 0dBFeeder Loss 1.5dB 0dBInterference Degradation Margin 3dB 3dBBody Loss 0dB 3dBDuplexer Loss 0dB 0dBRx Power -121dBm -96dBmFade Margin 4dB 4dBRequired Isotropic Rx .Power -117dBm (B) -92dBm ( D)
Maximum Permissible Path 148dB 149dB
RF LINK BUDGET
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Propagation Loss• LFS = 10 log ( 4 d / )2
• LFS = 32.44 +20 log (f )+ 20 log (d)Where f = frequency in MHz
d = distance in Kms
• LFS = Lo + 10 log ( d)
Where is the SLOPE of the attenuation characteristic
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BTS
Multipath Environment
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Classical Propagation Models
• Basically curve fitting exercises• Okumara• Basically curve fitting exercisesCosat 231 - Hata
(similar to Hata:for 1500-2000Mhz)• Walfisch - Ikegami Cost 231• Walfisch - Xia JTC• XLOS
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Okumara ModelThe Okumara tests are valid for :• 150-2000 Mhz• 1-100 Kms• BTS heights of 30 -100 meters• MS antenna height , typically 1.5 m (1-10m)• The results of Okumara tests were graphically represented
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PROPAGATION MODELS
• Hata Model • The basic equation for the 150-1000 MHz band is given by• Lp=69.55+ 26.16 log(f) -13.82 log (hbts)-a (hm)
+ {44.9- 6.55log(hbts)} log(d)
Where f=frequency in MHzHbts =BTS antenna height in meters (30-100m)d=distance in Kms (1 to 20 Kms)hm=mobile antenna height in meters (1-10m)a(hm)=correction for mobile height if hm is >1.5 meters
=3.2 [log(11.75hm)-4.97 for Dense urban and ={1.1 log(f)-0.7} hm-{1.56 log (f)-0.8} for Urban areas
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Okumara-Hata ModelThe path loss equation can be rewritten as :
•Lp=Lo + {44.9-6.55 log (hbts)} log(d)
• Where Lo=[69.55+26.16 log(f)-13.82 log (hbts)-a(hm)].OR more conveniently
•Lp=Lo +10 log (d) is the SLOPE and is ={44.9-6.55log (hbts)} /10
typically varies from 3.5 to 4 for urban environments.
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Calculate the path loss in a BTS site in an Urban environment, given the following parameters
• Frequency : 900 MHz
• Cell radius : 5Kms
• BTS antenna height 30 m• Mobile antenna height 3m.
• Also calculate the Attenuation slope for this site. • Lp =[69.55+26.16 log(f)- 13.82 log (hBTS) -a (hm)]+ [44.9 -6.55 log (hBTS)] log(d).• a(hm) = { 1.1 log (f) -0.7 } hm -{1.56 log (f) -0.8}
26.16 log (f) = 77.28 dB13.82 log (hBTS) = 20.41dB
[44.9-6.55log (hBTS)]log (d) = 24.62 dBa(hm) = 3.81 dB
Path Loss Lp =69.55+77.28 -20.41 +24.62 -3.81 = 147.23dB.Attenuation Slope = [44.9-6.55 log (hBTS )]/10 =35.225/10 =3.5225.
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Propagation…Okumara-Hata ModelThe receive signal strength RSS is given by :
RSS = ERP- {Lo +10 log(d)}.
The distance d can be calculated from :
d= 10 [ERP -Lo-RSS]/10
Or, from the equation for RSS,
Log (d) =[ERP-RSS-Lo]/10
ie.., d=antilog [ERP-RSS-Lo)/10 ]
Lo=69.55+26.16 log (f)-13.82 log(hbts)-a(hm).
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Example- To Calculate cell radius (d)Calculate the cell radius for a site that has:Frequency : 900 MHz BTS height: 30meters
Mobile height: 3 meters BTS ERP: 55dBm
Expected RSS at the cell boundary (d=R) = -75dBm.
Lo= 122.61 dB; = 3.5 (calculated in the previous example).
122.61 -75+35 log (d) =55 dBm.
log (d) = 7.39/35 =0.2111
Therefore d= antilog (0.2111) =1.62 Kms.
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Calculating the Signal Strength• After the terrain has been acquired in the database for the entire
site signal strength calculations can be made on the individual stations
• The propagation model calculates the path loss using the following components.
– Basic Path Loss - Okumura’s Model– Diffraction Effects - Picquenard’s Multiple Knife Edge Diffraction
model – Water Enhancement– Antenna Patterns, Tilt amount, Tilt type– Curvature of the Earth– Morphology
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Morphological CategoriesWaterBushesWet Farm landDense Residential AreaHeavy Urban TreesDry Farm LandLight Residential AreaLight UrbanHeavy Urban
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Location Area PlanningHLR
MSC/VLR
MSC/VLR
1 location area = several cells
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Drive Test Analysis
• Drive test gathers accurate propagation data for candidate site for evaluation and approval.– Uses both Omni-directional and sector antenna.– Radiation center and ERP modeling.– Measurement integration performed to improve modeling
efficiency.
• Based on drive data and prediction, the optimum antenna radiation center, ERP and sector orientation determined.
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BSS Parameters setting
• GSM base station parameters setting achieves the following functions
• MS measurement of serving and neighbouring stations• Call set up - Call Processing, Paging, System Access, & Short Message
Service.• Radio functions: DTX, DRX, Frequency Hopping• BTS Radio Resource Management• Mobiles’ uplink Power Control• Timing Advance• Handover - Based on PWRBGT (Power budget), RXLEV, RXQUAL,
distance and intra-cell
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Signal Variations
Fast Fading
Slow Fades
Long term average
Distance
RSS
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Standard Deviation
Example
The RSS values obtained from a drive test in a BTS area in a city
- 80 dBm , - 79 dBm , - 77 dBm , -82.5 dBm , - 84.35 dB - 78.65 dBm
• Mean RSS “M” = -79.97 dBm
• Standard deviation = 6.068
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Confidence Interval
M- 3 M- 2 M- M M+ M+2 M+3
99.72 %
95.44 %
68 %
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Probability
• Probability (P) that a random sample of RSS will have a value of - 92dBm or better (ASSUME M=-79 & = 8)
• Compute z =( x-M)/ = -92 -( - 79 )/8 = - 1.625• Refer the standard table for normal distribution curve
we get P=94.74%
• Probability that RSS value would be better than -92 dBm isP (RSS -92 dBm ) = 94.74%
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Typical values for building penetration loss
• If the minimum RF signal strength for 90 % coverage on the street is ,say - 92 dBm , then for 75 % in building coverage in a central business area ,we should have a signal level of - 72 dBm on the road;
This shall provide - 92 dBm inside the building.
Area 75% Coverage
50 % Coverage
Central Business area 20 dB 15 dBResidential area 15 dB 12 dBIndustrial area 12 dB 10 dBIn Car 6 to 8 dB