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WiMAX Cell Site Design for SCADA Communication
WiMAX Cell Site Design for SCADA Communication
Contents1. Introduction to WiMAX2. Fixed WiMAX Network Design Flow Sequence.3. Premise of the Network Design.4. WiMAX Spectrum allocation5 Choice of OFDM parameters 6. TDD/FDD channels. 7. Throughput Calculation for different RF channels.8. Erceg Path Propagation Model 9.Possible coverage area based on propagation
model.10.CPE Capacity Calculation11.Base Station Capacity Calculation12.Frequency Reuse Plan Options
WiMAX (Worldwide Interoperability for Microwave Access) is a standards-based technology enabling the delivery of “last mile” wireless broadband access as an alternative to cable, DSL or T1/E1 service.
WiMAX is expected to provide fixed , nomadic, portable and, eventually, mobile wireless broadband connectivity without the need for direct line-of-sight (LOS) with a base station.
In a typical cell radius deployment of three to ten kilometers, WiMAX Forum Certified™ systems can be expected to deliver capacity of up to 40 Mbps per channel (depending on bandwidth of RF channel), for fixed and portable access applications.
Mobile network deployments are expected to provide up to 15 Mbps of capacity within a typical cell radius deployment of up to three kilometers.
Introduction to WiMAX
WiMAX Throughput CalculationThe net usable throughput of WiMAX system will depend on1. Coverage Calculations:a) On the choice of OFDM parameters Channel Spacing (dependent on spectrum profile). Number of FFT points or sub-carriers inside a channel. Sub-carriers used as pilot channels. Sub-carriers used as guard channels. Symbol duration (including guard period) Modulation & FEC coding rates.b) On Path Propagation Loss Model used Erceg Model for Fixed WiMAX, COST231 for Mobile WiMAXc) Characteristics of the WiMAX System. System Gain Parameters of Tx,Rx, heights of Antennas at TX, Rx, Receiver Sensitivity
of the Systemd) Sectorization & Frequency Re-use No of Sectors in a Cell Site (with 120 ,90 , 60 degrees beam width antennas) No of frequencies that can be used in a cell.e) Geographic Area to be Covered
2. Capacity Calculations No of CPEs used Over Booking Factor Average Traffic Demand
Frequency Band
Path loss Model
System Gain
Link Budget
Calculations
Modulation/Coding
Type
Channel Bandwidt
h
Overbooking Factor
Average Traffic
Demand
Cell/Sector range
Cell/Sector
Capacity
Geographic Area
Size
Network Eqpt
Demand
Eqpt Prices
OPEX CAPEX
Economic Results
No of CPEs
Capacity Demand
Fixed -WiMAX
Network Design Flow Sequence
Radio Spectrum for WiMAX profiles
Source: Fujitsu Whitepaper: RF Spectrum utilization in WiMAX, November 2004
Frequencies available for WiMAX deployment World-wide
Region Licensed Frequency Band
Canada 2.3/2.5 GHz 3.5/5GHz
USA 1.5/2.3 GHz, 2.5/5 GHz
Central & South America 2.5/3.5 GHz, 3.5GHz
Europe 3.5GHz, 5GHz
Middle East & Africa 3.5GHz,5GHz
Russia 2.3/2.5/3.5GHz, 5GHz
India 3.5GHz
Asia Pacific 2.3/3.3/3.5GHz 5GHz
Un Licensed Frequency band: 2.4GHz,5.15GHz & 5.85GHz
Legend:
U-NII: Un-licensed National Information Infrastructure.
WRC: World Radio Conference
ISM: Industrial Scientific & Medical
MMDS: Multi-channel Multi point Distribution Service
WCS: Wireless Communication Service
Let {2.4835-2.4995 GHz} is allotted Spectrum for example
WiMAX Spectrum Band (2483.5 to 2499.5MHz)
Uplink (for1.75MHz) :From-To
2486.625 MHz 2488.375 MHz
Downlink (for 1.75 MHz) From-to
2498.625 MHz 2496.375 MHz
Uplink (for 3.5 MHz) : From -To
2485.750MHz 2489.250 MHz
Downlink (for 3.5 MHz) From-To
2493.750MHz 2497.250MHz
2498.3MHz2499.5MHz
2491.5MHz
2487.5MHz 2495.5MHz16MHz
3.5MHz 3.5MHz
Up Link Down Link
8MHz
F2:7MHzF1: 7MHz
F4: 3.5MHzF3: 3.5MHzF2: 3.5MHzF1 :3.5MHz
F9 F8 F7 F6 F5 F4 F3 F2F1
1.75MHz
2499.250
2497.500
2495.750
2494.000
2492.250
2490.500
2488.750
2487.000
2485.250
16MHz spectrum band
2483.500
250KHz
2499. 500
Possible TDD Channels
Possible FDD Channels
1.75MHz
1.75MHz
Issue Multiplexing Method in Advantage
FDD TDD
Guard Band TDD FDD requires a guard band to separate the DL and UL channels which amount to a substantial loss in spectrum.
No guard bands are required.
Guard Time FDD No guard time is required at the end of DL transmission. However, guard time is required at the end of UL transmission because typically the SUs are HFDD units that need to turn around from Tx to Rx to receive the new BSU schedule information for the next downlink.
Guard time is required between Tx and Rx and vice versa. The guard time is equal to a unit’s turn around time plus the round trip delay. A unit’s turn around time is in the order of 50 us. The round trip delay is in the order of 66 us. Thus the round trip delay can absorb the transmitter’s turn around time whenever the direction of traffic switches. The loss in throughput due to guard time for a 5 ms frame is about 2%.
Frequency Plan and Reuse
FDD The adjacent channel interference is much lower than in a TDD scheme.
Frequency planning is required only for one channel. If all TDD-based systems are synchronized to GPS, using the same frame size and DL/UL partitioning can mitigate interference.
Comparison of TDD & FDD for WiMAX
IssueMultiplexing
Method in Advantage
FDD TDD
Hardware Cost
TDD
FDD requires one transmitter and a separate receiver. Further a diplexer and shields are required to isolate the DL and UL.
As the transmitter and receiver use the same filters, mixers etc the cost of a TDD scheme is substantially less than an FDD scheme.
Dynamic Bandwidth Allocation
TDD
Once the channel bandwidth is granted by the regulator the UL/DL allocation cannot be modified. This leads to unused spectrum for asymmetric operations such as Internet traffic.
Where cell interference is not a problem, adaptive UL/DL allocation allows dynamic bandwidth allocation for UL and DL traffic. This is especially important for Internet traffic.
Comparison of TDD & FDD (Contn..d)
SOURCE : http://www.moonblinkwifi.com/fddvstddwimax.cfm
Geographic Area Size: SCADA RTU Well Density : 2000 No Average Density of Wells: 2 No /km2
Topography : Plain Terrain . WiMAX Cell Site Coverage radius (in Km) : 10 (assumed value) Area of Hexagonal Cell site assuming no overlap of coverage: [ ( 3 x sq root(3) /2) x
(10)2 ) ] = 260 Km2 No of RTUs in a Cell site : (260 Km2 )* 2 = 520Data requirement of RTUs: Uplink Committed Information Rate : 56 Kbps (actual required speed is 9600 baud) Downlink Committed Information Rate: 56 Kbps Total_ Up link capacity: 520 x 56 = 29,120 Kbps Total_Down link capacity: 520 x 56 =29,120 Kbps For TDD Duplexing method, Total_Link_Throughput : 29,120+29,120 Kbps=58,240Kbps % of RTUs active & communicating at any instant : 90 % (i.e 468 RTU wells) % of average air time usage by active RTUs := 50% (assumption) % of air time usage by active RTUs := (% of active RTUs) x (%of average air-time usage)
= (90%) x (50%)= 0.45 Over subscription Factor (OSF) : 1/0.45 = 2.222 (i.e for every second 450mSec is used , which means we can replicate the total number of
RTUs by 2.22 x times or it can serve for 2.2 x 520 = 1144 wells)
Due to actual air-time usage and activity, the required throughput utilized is (Total_Link_Throughput)/(Oversubscription Factor) (58,240 Kbps)/ 2.222 = 26,208Kbps or 26.208 Mbps
Premise of WiMAX Network Design for SCADA Communication
Objective : To design the cell site with 10Km coverage radius and be able to exceed the data rate requirement of 26.208Mbps. Then the network is said to be over-subscribed.
10 Km
Base Station
RTU
Sno
OFDM Parameters ValueChoice
BW=3.5MHzunits
Choice BW=1.75MHz
units
1 Sampling Frequency (Fs)
7/6 (undersampli
ng) or 8/7 (over
sampling) x BW
4 MHz 2 MHz
2 Carriers NFFT 256 256 256
3 Data Carriers (Nused) 192 192 192
4 Useful Time (Tb) NFFT /Fs 64 μsec 128 μsec
5 Subcarrier Spacing (Δs) Fs/NFFT 15.625 KHz 7.8125 KHz
6 Delay Spread (Гrms) 3μsec 3 μsec 3 μsec
7Guard time/ Useful Symbol time ratio (Tg/Tb)
1/32,1/16,1/8,1/4
1/16 1/16
8Cyclic Prefix Time (Tg) (choose Tg> Гrms )
Tb/32 2 μsec 4 μsec
9 Symbol Time (Ts) Tb+ Tg 66 μsec 132 μsec
10 Bandwidth Efficiency[(Fs/
BW)x(Nused+1)/(NFFT)]
86 % 86.16071429 %
11Total Data channel baud rate (for Nused=192 data carriers)in Kbps
(192x (1/Ts) 2909.0909 Kbps 1454.5454 Kbps
Choice of OFDM Parameters for Channel Bandwidth
Single sub-carrier baud rate = 1/(66 μ sec) =15.152 KBaud. Total Data Channel baud rate = 192 * 15.151KBaud = 2.909MBaud As a large portion of PDU (Physical Data Unit) is allocated for Cyclic Redundancy Check (CRC),
Forward Error Correction (FEC), and /or Convolution Coding.
There are two convolution rates per modulation rate yielding 8 different modulation levels as follows:
(1) BPSK ½ (2) BPSK ¾ (3) QPSK ½ (4) QPSK ¾ (5) 16QAM ½ (6) 16QAM ¾ (7) 64QAM 2/3 (8) 64QAM ¾ ½, 2/3 and ¾ refer to the fraction of the PDUs allocated for actual user data; the rest is
management, CRC bits Net usable throughput for 3.5MHz RF channel for various modulation scheme is as follows:
For BPSK ½ : 2.909 Mbps x ½ = 1.45 Mbps For 16QAM ½ : 11.636 X ½ = 5.82 Mbps For QPSK ½ : 5.818 Mbps x ½ = 2.909 Mbps For 16QAM ¾ : 11.636 X ¾ = 8.73 Mbps
In practice, bandwidth tends to be lower by 5% to 7% for a general point-to-point link.
WiMAX Throughput Calculation for RF Channels
Modulation Type Used
Bits /Baud Throughput (Mbps)
BPSK 1 2.909
QPSK 2 5.818
16QAM 4 11.636
64QAM 6 17.454
Table :Throughput and Modulation
Bit rate &Modulation*
Note : * Bit rate is in Kbps, Guard Time is 1/32 of Symbol Time, excluding MAC & Preamble Overhead.
Receiver Sensitivity= -102+SNR(Rx)+10.log(Fs.(Nused/Nfft).(Nsubchannels/16)) ; Nused : 200; Nfft= 256; Nsubchannels:16
Modulation
Bits/baud
Coding rate
Receiver SNR(dB) for BER =10-6
Throughput (for 3.5MHz
Channel) (coding rate x
bits/baud x Total Data
channel baud rate)
Spectral Efficiency (Bits/Hz ] (@3.5MHz
)
Rx Sensitivi
ty in dBm
(For
3.5MHz BW)
Throughput (for
1.75MHz Channel) is (coding
rate x bits/baud x Total Data
channel baud rate)
SPECTRAL
EFFICIENCY
(BITS/Hz ]
(@1.75MHz )
Rx Sensitiv
ity in dBm (For
1.75MHz BW)
BPSK 1 1/2 6.4 1454.5455 0.4156 -102.69
26
727.2727 0.4156 -105.70
3
QPSK 2 1/2 9.4 2909.0909 0.8312 -102.70
29
1454.5455 0.8312 -102.70
3
2 3/4 11.2 4363.6364 1.2468 -97.892
6
2181.8182 1.2468 -100.90
3
16-QAM 4 1/2 16.4 5818.1818 1.6623 -92.692
6
2909.0909 1.6623 -95.703
4 3/4 18.2 8727.2727 2.4935 -90.892
6
4363.6364 2.4935 -93.903
64-QAM 6 2/3 22.7 11636.3636 3.3247 -86.392
6
5818.1818 3.3247 -89.403
6 3/4 24.4 13090.9091 3.7403 -84.692
6
6545.4545 3.7403 -87.703
Characteristics of Proposed WiMAX System
Sno Parameter Value Units
1 Center Frequency of Spectrum (2483.5MHz – 2499.5MHz) 2491.5 MHz
2 Duplexing TDD
3 Multiple Access TDMA
4 Modulation adaptive BPSK,QPSK,QPSK,16-QAM,64-QAM
5 Channel Bandwidth 3.5 / 1.75 MHz
6 Input power to BST (Pi) 39 dBm
7 Hbs (Height of Base Station antenna) 30 meters
8 Hrx (Height of Subscriber Station antenna) 6 meters
9 BS antenna gain Gi 17 dBi
10 BS feeder loss 0.5 dB
11 Input power to CPE 23 dBm
12 receiver antenna gain( Gr) 18 dBi
13RX sensivityfor QAM64 3/4 & 3.5MHz channel and 1.75MHz channel
-84.692, -87.702 dBm
14 Receiver feeder loss 0 dB
15 Other connector losses 4 dB
16 CPE Outdoor
17 Coverage requirement 100 %
18Fade Margin for 99.9% reliability ( as per ITU-R P.530 Recommendation)
10 dB
19 Distance (d) Max 10 Km
20 EIRP =Tx power +GTx-miscellaneous losses at TX 51.5 dBm
21 Total Gain: EIRP+GRx-Rxfeeder loss 69.5 dB
Erceg Path Loss Model ( recommended model by IEEE 802.16 BWA Team)Path Loss (PL)= A + 10ξlog(d/d0)+ΔLf+ΔLh+S for d>d0 (d0 =100mtr)
Terrain A [Hilly areas with
moderate -to-Heavy
tree density]
Terrain B [Intermediate Terrain
with moderate
tree density]
Terrain C [Flat terrain with light tree
density]
a 4.6 4 3.6
b 0.0075 0.0065 0.005
c 12.6 17.1 20
A= 20log(4Πd0/λ) where d0 = 100mtrs
ξ= (a-b*(Hbs)+ c/(Hbs))ξ is path-loss exponent
a,b,c are constants representing certain terrain type.
d is the distance between Base Station (BS) and Receive antenna (Rx) in meters.Δ Lf = frequency correction term : =
6*log(f/2000); f is frequency in MHz
Δ Lh= receive antenna height correction term: = -10.8log(Hss/2) for Terrain A,B; -20log(Hss/2) for Terrain C.
S is shadow fading component. (8.2-10.6dB depending on the terrain and tree density type). 10.6dB for Terrain C
Type C terrain is considered for Path Loss Model
Link Budget (Down Link) with Erceg Model for Type C Terrain
Distance
(inKm)
A= 20log(4Π
do/λ)
ξ (Path-loss Component
)= (a-b.Hbs+c/H
bs);
10ξ Log(d/d
0)
ΔLf = frequenc
y correction term(6
log (f/2000) f:inMHz
ΔLh= receive antenna height
correction term (-
20log(Hss/2) for
Terrain C.)
S is shadow fading
component.
(8.2 for Type C terrain).
Total Path Loss
P rx= Ptx+Gtx+
Grx-connector loss-Path
loss
Calculated Fade Margin
(for 3.5MHz,
QPSK-3/4 Modulatio
n, Rx sensitivity
:-97.892 dBm)
Calculated Fade Margin (for 3.5MHz, QPSK-1/2 Modulation,
Rx sensitivity :-99.693 dBm)
Calculated Fade Margin (for
3.5MHz, BPSK-1/2 Modulation, Rx sensitivity
:-102.692 dBm)
180.37448
5384.1166666
6741.166
670.57258
54
-9.5424250
94 8.2120.7713123
-51.271312
3346.62068
767 48.42168767 51.42068767
580.37448
5384.1166666
6769.940
930.57258
54
-9.5424250
94 8.2149.5455775
-80.045577
517.84642
25 19.6474225 22.6464225
680.37448
5384.1166666
6773.200
560.57258
54
-9.5424250
94 8.2152.8052055
-83.305205
4714.58679
453 16.38779453 19.38679453
780.37448
5384.1166666
6775.956
540.57258
54
-9.5424250
94 8.2155.5611816
-86.061181
6411.83081
836 13.63181836 16.63081836
7.580.37448
5384.1166666
6777.190
020.57258
54
-9.5424250
94 8.2156.7946677
-87.294667
6710.59733
233 12.39833233 15.39733233
7.680.37448
5384.1166666
6777.426
830.57258
54
-9.5424250
94 8.2157.0314719
-87.531471
8710.36052
813 12.16152813 15.16052813
7.780.37448
5384.1166666
6777.660
530.57258
54
-9.5424250
94 8.2157.2651805
-87.765180
5110.12681
949 11.92781949 14.92681949
8.580.37448
5384.1166666
6779.427
750.57258
54
-9.5424250
94 8.2159.0323914
-89.532391
438.359608
566 10.16060857 13.15960857
980.37448
5384.1166666
6780.449
650.57258
54
-9.5424250
94 8.2160.0542956
-90.554295
637.337704
369 9.138704369 12.13770437
9.580.37448
5384.1166666
6781.416
290.57258
54
-9.5424250
94 8.2161.0209341
-91.520934
086.371065
923 8.172065923 11.17106592
1080.37448
5384.1166666
6782.333
330.57258
54
-9.5424250
94 8.2161.937979
-92.437978
995.454021
008 7.255021008 10.25402101
For BPSK 1/2, 3.5MHz channel& Rx Sensitivity of -102.692 dBm, 10Km is coverage distance for 99.9% reliabilityFor QPSK 1/2, 3.5MHz channel& Rx Sensitivity of -99.693 dBm, 8.5Km is coverage distance for 99.9% reliability
Distance (in Km)
A= 20log(4Πdo/λ)
ξ= (a-b. Hbs +c/ Hbs)
log(d/d0)
10ξlog(d/d0)
ΔLf = 6*log(f/2000)
ΔLh=-20log(Hss/2) for Terrain C
s: shadowing Component (Type C terrain)
Path Loss(PL)= A + 10ξlog(d/d0)+ΔLf+ΔLh+S for d>d0
P rx= Ptx+Gtx+Grx-connector loss-Path loss(PL)
Fade Margin
(in dB)
(for 3/4)
0.180.37448538
4.116666667 0 0
0.572585375
-9.5424310.6 82.00465
-12.50465
72.18735
0.280.37448538
4.116666667 0.30103
12.3924015
0.572585375
-9.5424310.6 94.39705
-24.89705
59.79495
0.380.37448538
4.116666667
0.47712125
19.6414917
0.572585375
-9.5424310.6 101.64614
-32.14614
52.54586
0.480.37448538
4.116666667
0.60205999
24.784803
0.572585375
-9.5424310.6 106.78945
-37.28945
47.40255
0.580.37448538
4.116666667 0.69897
28.7742652
0.572585375
-9.5424310.6 110.77891
-41.27891
43.41309
180.37448538
4.116666667 1
41.1666667
0.572585375
-9.5424310.6 123.17131
-53.67131
31.02069
280.37448538
4.116666667 1.30103
53.5590682
0.572585375
-9.5424310.6 135.56371
-66.06371
18.62829
380.37448
5384.116666
6671.47712
12560.8081
583
0.572585375
-9.54243
10.6 142.81280
-73.3128
011.379
20
480.37448538
4.116666667
1.60205999
65.9514696
0.572585375
-9.5424310.6 147.95612
-78.45612
6.23588
580.37448538
4.116666667 1.69897
69.9409318
0.572585375
-9.5424310.6 151.94558
-82.44558
2.24642
680.37448538
4.116666667
1.77815125
73.2005598
0.572585375
-9.5424310.6 155.20521
-85.70521
-1.01321
780.37448538
4.116666667
1.84509804
75.956536
0.572585375
-9.5424310.6 157.96118
-88.46118
-3.76918
880.37448538
4.116666667
1.90308999
78.3438711
0.572585375
-9.5424310.6 160.34852
-90.84852
-6.15652
980.37448538
4.116666667
1.95424251 80.44965
0.572585375
-9.5424310.6 162.45430
-92.95430
-8.26230
1080.37448538
4.116666667 2
82.3333333
0.572585375
-9.5424310.6 164.33798
-94.83798
-10.14598
1580.37448538
4.116666667
2.17609126
89.5824235
0.572585375
-9.5424310.6 171.58707
-102.08707
-17.39507
2080.37448538
4.116666667 2.30103
94.7257348
0.572585375
-9.5424310.6 176.73038
-107.23038
-22.53838
Link Budget Calculation (Down Link) for ¾ QAM-64 with Erceg Path Loss Model
For 64QAM-3/4, 3.5MHz channel& Rx Sensitivity of -84.692 dBm, 3Km approx is coverage distance for 99.9% reliabilityNote: The uplink (UL) input power will be lower but sub-channeling and diversity techniques will enhance the uplink budget, resulting in a similar performance.
Modulation- Bit rate- Distance of Coverage based on Erceg Path Loss Model
3.5MHz channel 1.75MHz channel
Modulation Rx Sensiti
vity (3.5MH
z)
Max Bit rate
obtainable (Mbps)
Max distance
of coverage
in Km) with
99.9% reliability*
Modulation
covered area (in sq km) in a cell
of coverage radius
of 10Km
coverage % in a cell of
coverage radius of
10Km
Rx Sensitivit
y (1.75MH
z)
Max Bit
rate obtainable (Mbps
)
Max distance
of coverage (in Km)
with 99.9%
reliability*
Modulation
covered area (in sq
km) in a cell
of covera
ge radius
of 12Km
coverage % in a cell of
coverage radius
of 12 Km
BPSK -1/2 -102.69
2
1.454 10.00 72.15 27.75 -105.703 0.727 12.00 109.17 29.16
QPSK-1/2 -99.693
2.909 8.50 33.70 12.96 -102.703 1.454 10.10 49.92 13.33
QPSK-3/4 -97.892
4.363 7.70 52.04 20.02 -100.903 2.181 9.10 69.98 18.69
16-QAM-1/2
-92.692
5.818 5.70 31.81 12.23 -95.703 2.909 6.80 45.38 12.12
16-QAM-3/4
-90.892
8.727 5.20 28.70 11.04 -93.903 4.363 6.20 40.04 10.69
64-QAM-2/3
-86.392
11.636 4.00 6.01 2.31 -89.403 5.818 4.80 11.83 3.16
64-QAM-3/4
-84.692
13.09 3.70 35.59 13.69 -87.703 6.545 4.30 48.07 12.84
* ITU-R P.530 recommendation for reliability is considered: 10dB of Fade Margin corresponds to 99.9% reliability
260.00 100.00374.4
0 100.00
Distance (Km)
3.70 4.0
5.2
5.7
7.7
8.8
10.0
26.8%
12.96%
27.75%
5.45%
11.04%
2.31 %
13.69%
QPSK 1/2
BPSK 1/2
QPSK 3/4
16QAM-1/2
16QAM-3/4
64QAM-2/3
64QAM-3/4
1.454Mbps
2.909Mbps
4.363Mbps
5.818Mbps
8.727Mbps
11.63Mbps
13.09Mbps
Modulation- Bit rate- Distance of Coverage in a WiMAX Cell Site (of 10Km radius and 3.5MHz channel)
RTU Capacity Calculation:
Parameter Units Value
Total Coverage area /cell Km2 260
No of RTUs/SqKm Ea 2
Total No of RTUs in the coverage area Ea 520
Downlink Committed Information Rate (CIR) Kbps 56
Uplink Committed Information Rate (CIR) Kbps 56
Total Uplink Capacity Mbps 29.120
Total Downlink Capacity Mbps 29.120
Total Link Throughput (UL+DL Capacity) Mbps 58.240
Base Station (BS) Percentage Utilization Calculation:
% of active RTUs at an instant (assumption) % 90
% of average air time usage by active RTUs ( assumption) % 50
% of usage of Total Bandwidth of BS % 0.45
Over Subscription Factor for all RTUs (OSF or replication ratio) =(1/(%of usage) ratio 2.222222222
BST Capacity (in Mbps) required by active RTUs on average [ Total Throughput required]/[OSF] Mbps 26.208
CPE Bandwidth Requirement Calculation
Modulation & Coding Scheme
% Coverage [From
Modulation-Bit rate-Distance
Coverage Chart]
Data rate, in Mbps for(3.5MHz channel)
%Capacity = (% Coverage x data rate )
BPSK -1/2 27.75 1.454 0.8758896
QPSK-1/2 12.96 2.909 0.3770064
QPSK-3/4 26.80 4.363 1.169284
16-QAM-1/2 5.45 5.818 0.317081
16-QAM-3/4 11.04 8.727 0.9634608
64-QAM-2/3 2.31 11.636 0.2687916
64-QAM-3/4 13.69 13.09 1.792021
[Capacity in a Sector (Mbps)] 5.7635344
[Base Station Capacity with 3 sectors (3 x sector capacity) in Mbps] 17.289
Required Bandwidth ( in Mbps) including Oversubscription [from CPE bandwidth requirement table]
26.208
No of Base Stations required (approx) = (CPE Data Capacity requirement) /(Base Station Capacity)
1.511So, 2 Base Stations (1 Capacity BST) is required to cover 260 Sq Km of area (with 99.9% reliability) to serve 520 CPEs with Committed Information Rate of 56Kbps on each Uplink and Downlink TDD channel.
Base Station Capacity Calculation( for 10Km coverage radius and 3.5MHz channel)
0
2
46
8
10
1214
16
18
2022
24
26
2830
32
34
3638
40
42
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Distance from Base Station ( in Km )
Bas
e Sta
tion
Tra
ffic
Cap
acity
( in
Mbps) BST Max capacity (in Mbps) with 3 sectors For 3.5MHz
BST Max capacity (in Mbps) with 3 sectors For 1.75Mhz
Base Station Traffic Capacity and Coverage Distance of WiMAX System
Option 2: Frequency Reuse (C,S,N)
C: no of BST s / cluster : 01
S: no of sectors / BST site : 03
N: no of unique RF Channels needed for reuse : 03
Frequency Reuse Pattern: (1,3,3)
Option:1 : Frequency Reuse (C,S,N) with Cluster order 3 & Cell radius of 10Km
C: no of BST s / cluster : 01
S: no of sectors / BST site : 03
N: no of unique RF Channels needed for reuse: 01
Frequency Reuse Pattern: (1,3,1); K: Cluster Order :03
Frequency Reuse Plan options
Carrier –to –Interference Noise Ratio Ref[11] (C/I) Uplink: (No of sectors)/6 x (D/R)ξ
where ξ is path loss component value 4.11 for C type Terrain as per Erceg Path Loss Model
(3/6)x (30/10)4.116 = 46 =16.62 dB
Co-channel distance ( D ) =R x √ (3x K) = 10x√3*3 = 30Km
F2
F2
F2
F1
F1
F1
F3
F3
F3
R=10 KM
D
120˚
120˚
120˚
F2
F3
F1
F1
F2
F3
F1
F2
F3
R=10 KM
120˚
120˚
120˚
F2
120˚
F1
F3
CPE Bandwidth Calculation -Example
Geographic Area Size:
No of RTUs in the Oil Field : 85 ; Total area of coverage : 65 Sq Km; Density of RTUs : 1.307 per Sq Km
RTU Capacity Calculation:
Parameter Units Value
Downlink Committed Information Rate (CIR) Kbps 56
Uplink Committed Information Rate (CIR) Kbps 56
Total Uplink Capacity (No of RTUs x CIR) Mbps 4.760
Total Downlink Capacity (No of RTUs x CIR) Mbps 4.760
Total Link Throughput (UL+DL Capacity) Mbps 9.520
Base Station (BS) Percentage Utilization Calculation:
% of active RTUs at an instant (assumption) % 90
% of average air time usage by active RTUs ( assumption) % 50
% of usage of Total Bandwidth of BS % 0.45
Over Subscription Factor for all RTUs (OSF or replication ratio) =(1/(%of usage) ratio 2.222222222
BST Capacity (in Mbps) required by active RTUs on average [ Total Throughput required]/[OSF] Mbps 4.288Objective : To design the cell site with 5Km coverage radius and
be able to exceed the data rate requirement of 4.288 Mbps. Then the network is said to be over-subscribed.
Base Station
Existing Oil Field Area : 16Sq Km
No of RTUs: 50
Existing Oil Field Area :4 Sq Km
No of RTUs: 351Km
1Km
Proposed WiMAX cell site
(Example) : Base Station:
No of RTUs : 85
Area of Cell site: 65 SqKM
No of Channels /cell :03
Frequency Reuse Pattern: (1:3:3)
R =5Km
F1
F2
F3
Modulation- Bit rate- Distance of Coverage (Example)
Modulation
Coding Rx Sensiti
vity (3.5MHz)
Max Bit rate
obtainable
(Mbps)
Spectral Efficiency (bits/sec/
Hz)
Max distance of coverage in
Km) with 99.9%
reliability*
Modulation covered
area (in sq km) in a
cell of coverage
radius of 5 Km
coverage % in a cell
of coverage
radius of 5 Km
BPSK -1/2 1/2 -102.69
2
1.454 0.415428571
10.00 0 0
QPSK-1/2 1/2 -99.693 2.909 0.831142857
8.50 0 0
QPSK-3/4 3/4 -97.892 4.363 1.246571429
7.70 0 0
16-QAM-1/2
1/2 -92.692 5.818 1.662285714
5.70 0 0
16-QAM-3/4
3/4 -90.892 8.727 2.493428571
5.20 23.40 36
64-QAM-2/3
2/3 -86.392 11.636 3.324571429
4.00 6.01 9.24
64-QAM-3/4
3/4 -84.692 13.09 3.74 3.70 35.59 54..76
* ITU-R P.530 recommendation for reliability is considered: 10dB of Fade Margin corresponds to 99.9% reliability
65 100.00
Modulation & Coding Scheme
% Coverage [From
Modulation-Bit rate-Distance
Coverage Chart]
Data rate, in Mbps %Capacity = (% Coverage x data rate )
BPSK -1/2 0 1.454 0
QPSK-1/2 0 2.909 0
QPSK-3/4 0 4.363 0
16-QAM-1/2 0 5.818 0
16-QAM-3/4 36 8.727 3.1417
64-QAM-2/3 9.24 11.636 1.0751
64-QAM-3/4 54.76 13.09 7.1680
[ Base Station Capacity (per sector)] 11.3849
[Base Station Capacity with 3 sectors (3 x Sector Capacity) in Mbps] 34.15491 *
Required Bandwidth ( in Mbps) including Oversubscription [from CPE bandwidth requirement table]
4.288
No of Base Stations required (approx) = (CPE Data Capacity requirement) /(Base Station Capacity)
0.248
So, 1 Base Station is sufficient to cover 65 Sq Km of area (with 99.9% reliability) to serve 85 CPEs with Committed Information Rate of 56Kbps on each Uplink and Downlink TDD channel.
* Base Station Capacity is abundant than the required CPE capacity
Base Station Capacity Calculation-Example
Available WiMAX system profiles WiMAX System profiles: Fixed, Mobile & Evolutionary WiMAX
Fixed WiMAX Mobile WiMAX Evolutionary WiMAX
Standard IEEE 802.16-2004 IEEE 802.16e-2005 IEEE 802.16e-2005
Multiplexing OFDM OFDMA OFDM
FFT Size 256 512,1024 256
Duplexing Mode TDD,FDD,HFDD TDD,FDD,HFDD TDD,FDD,HFDD
Modulation BPSK,QPSK,16-QAM,64-QAM QPSK,16-QAM,64-QAM(uplink)
BPSK,QPSK,16-QAM,64-QAM(optional)
Channel Bandwidths 3.5,7,10MHz 5,7,8.75,10MHz 3.5,7MHz
Frequency Bands 3.4-3.6 GHz, 5.7-5.8 GHz 2.3-2.4GHz,2.305-2.320 GHz,2.345-2.360GHz,3.3-3.4GHz,3.4-3.8GHz
2.305-2.302 GHz,2.345-2.360 GHz,3.4-3.6 GHz, 4.9-5.0 GHz
Source: http://www.wimaxforum.org/regulators/profiles/#certification
Currently Approved Certification profiles
System profiles Spectrum Duplexing Channel Bandwidth
Fixed WiMAX (IEEE 802.16-2004,OFDM)
3.4-3.6 GHz TDD 3.5 & 7 MHz
3.4-3.6 GHz FDD 3.5 & 7 MHz
5.725-5.850 GHz TDD 10 MHz
Evolutionary WiMAX (IEEE 802.16e-2005,OFDM)
4.935-4.990 GHz TDD 5 MHz
Mobile WiMAX (IEEE 802.16e-2005, OFDMA)
2.3-2.4 GHz TDD 5,10 MHz (dual), 8.75MHz
2.496-2.690 GHz TDD 5, 10MHz(dual)
3.4-3.6 GHz TDD 5,7 MHz
References1. IEEE802.16-20042. “Performance Evaluation of Fixed –Wireless Broadband
system based on IEEE 802.16”-Wout Joseph member IEEE,Ghent University, Belgium
3. WiMAX Forum: www.wimaxforum.com4. Lawrence Harte: Introduction to 802.16 WiMAX –Althos Publishing
house 20065. Harry R.Anderson “ Fixed Broadband Wireless System Design” –John
Wiley & Sons -20036. WiMAX Forum White Paper: Can WiMAX Address Your
Applications? By Westech Communications OCT 20057. SR Telecom - symmetry™ Product Data Sheets.8. ‘Competitive Potential of WiMAX in Broadband Access
Market: A Techno-Economic Analysis: Timo Smura , Networking Laboratory, Helsenki University of Technology- Finland.
9. ‘Channel Modes for Fixed Wireless Applications’ V.Erceg et.al, Project: IEEE 802.16 Broadband Wireless Working Group :dated 2001-07-17.
10. ‘Dimensioning Cellular WiMAX Part 1: Single Hop Networks’ –Christian Hoyman et al, RWTH Aachen University, Denmark.
Questions ?
Thank YouK.Raghuna
th
