WiMAX Cell Site Design for SCADA Communication

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WiMAX Cell Site Design for SCADA Communication
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Contents

• 1. Introduction to WiMAX
• 2. Fixed WiMAX Network Design Flow Sequence.
• 3. Premise of the Network Design.
• 4. WiMAX Spectrum allocation
• 5 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 Calculation
• 11.Base Station Capacity Calculation
• 12.Frequency Reuse Plan Options

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• Introduction to WiMAX

• 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.

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WiMAX Throughput Calculation

• The net usable throughput of WiMAX system will
  depend on
• 1. 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
  WiMAX
• c) Characteristics of the WiMAX System.
• System Gain Parameters of Tx,Rx, heights of
  Antennas at TX, Rx, Receiver Sensitivity of the
  System
• d) 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

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Fixed -WiMAX Network Design Flow Sequence
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Radio Spectrum for WiMAX profiles
Let 2.4835-2.4995 GHz is allotted Spectrum for
example
Source Fujitsu Whitepaper RF Spectrum
utilization in WiMAX, November 2004
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
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WiMAX Spectrum Band (2483.5 to 2499.5MHz)
16MHz spectrum band
2499.250
2497.500
2495.750
2494.000
2492.250
2490.500
2488.750
2487.000
2485.250
Possible TDD Channels
 F8
 F7
 F6
 F5
 F4
 F3
 F2
F1 1.75MHz
 
 F9
 
 
1.75MHz
F4 3.5MHz
F3 3.5MHz
F2 3.5MHz
F1 3.5MHz
F27MHz
F1 7MHz
 
1.75MHz
Possible FDD Channels
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Comparison of TDD FDD for WiMAX
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Comparison of TDD FDD (Contn..d)
SOURCE http//www.moonblinkwifi.com/fddvstddwima
x.cfm
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Premise of WiMAX Network Design for SCADA
Communication

• 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 ) 2 520
• Data 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
  29,12029,120 Kbps58,240Kbps
• 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)

10 Km
Base Station
RTU
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.
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Choice of OFDM Parameters for Channel Bandwidth
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WiMAX Throughput Calculation for RF Channels

• 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

Table Throughput and Modulation
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Bit rate Modulation
Receiver Sensitivity -102SNR(Rx)10.log(Fs.(Nuse
d/Nfft).(Nsubchannels/16)) Nused 200 Nfft
256 Nsubchannels16
Note Bit rate is in Kbps, Guard Time is 1/32
of Symbol Time, excluding MAC Preamble Overhead.
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(No Transcript)
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Erceg Path Loss Model ( recommended model by IEEE
802.16 BWA Team)
A 20log(4?d0/?) where d0 100mtrs
? (a-b(Hbs) c/(Hbs))
? is path-loss exponent
Type C terrain is considered for Path Loss Model
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For BPSK 1/2, 3.5MHz channel Rx Sensitivity of
-102.692 dBm, 10Km is coverage distance for
99.9 reliability
For QPSK 1/2, 3.5MHz channel Rx Sensitivity of
-99.693 dBm, 8.5Km is coverage distance for
99.9 reliability
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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 reliability
Note The uplink (UL) input power will be lower
but sub-channeling and diversity techniques will
enhance the uplink budget, resulting in a similar
performance.
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Modulation- Bit rate- Distance of Coverage based
on Erceg Path Loss Model
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Modulation- Bit rate- Distance of Coverage in a
WiMAX Cell Site (of 10Km radius and 3.5MHz
channel)
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CPE Bandwidth Requirement Calculation
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Base Station Capacity Calculation( for 10Km
coverage radius and 3.5MHz channel)
So, 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.
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Base Station Traffic Capacity and Coverage
Distance of WiMAX System
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Frequency Reuse Plan options
F3
F1
F1
120
F2
F3
120
F1
F2
F3
120
F2
F1
F2
120
R10 KM
Option1 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
F3
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)
Carrier to Interference Noise Ratio Ref11

(C/I) Uplink (No of sectors)/6 x (D/R)? where ?
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
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Objective 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.
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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 (133)
Existing Oil Field Area 16Sq Km No of RTUs 50
F3
F1
Base Station
Existing Oil Field Area 4 Sq Km No of RTUs 35
R 5Km
1Km
1Km
F2
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Modulation- Bit rate- Distance of Coverage
(Example)
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Base Station Capacity Calculation-Example
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
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Available WiMAX system profiles
Source http//www.wimaxforum.org/regulators/profi
les/certification
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References

• IEEE802.16-2004
• Performance Evaluation of Fixed Wireless
  Broadband system based on IEEE 802.16-Wout
  Joseph member IEEE,Ghent University, Belgium
• WiMAX Forum www.wimaxforum.com
• Lawrence Harte Introduction to 802.16 WiMAX
  Althos Publishing house 2006
• Harry R.Anderson Fixed Broadband Wireless
  System Design John Wiley Sons -2003
• WiMAX Forum White Paper Can WiMAX Address Your
  Applications? By Westech Communications OCT 2005
• SR Telecom - symmetry Product Data Sheets.
• Competitive Potential of WiMAX in Broadband
  Access Market A Techno-Economic Analysis Timo
  Smura , Networking Laboratory, Helsenki
  University of Technology- Finland.
• Channel Modes for Fixed Wireless Applications
  V.Erceg et.al, Project IEEE 802.16 Broadband
  Wireless Working Group dated 2001-07-17.
• Dimensioning Cellular WiMAX Part 1 Single Hop
  Networks Christian Hoyman et al, RWTH Aachen
  University, Denmark.

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Questions ?
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Thank You
K.Raghunath