planning for vowifi
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Planning for VoWiFi. Jai Rawat, AirTight Networks [email protected]. Agenda. Wireless Medium Characteristics RF Basics VoWiFi Deployment Challenges VoWiFi Deployment Best Practices/Solutions Interactive Workshop Take Away Q&A. Wireless Medium Characteristics. - PowerPoint PPT PresentationTRANSCRIPT
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Agenda
• Wireless Medium Characteristics• RF Basics• VoWiFi Deployment Challenges• VoWiFi Deployment Best Practices/Solutions• Interactive Workshop• Take Away• Q&A
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Wireless Medium Characteristics• Access Point (AP) coverage depends on
– Building material– Building layout– AP location– Mount type (ceiling, wall, desktop)– Antenna type and orientation– AP transmit power– Transmit protocol (802.11 a/b/g)
• Coverage is not static/predictable– Fluctuates constantly due to multipath and moving objects– Interference due to neighbor APs or other sources of noise– Packet collisions
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RF Basics
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10-3
101
10-6
Power
10W
Source
1 W
d2d1
1mW (= 0 dBm)
10,000 times
40 dB
RF Basics : What is dB?
1,000 times
30 dB
Path loss from source to d2 = 70dB
(= 40 dBm)
(= -30 dBm)
dB: relative measure of signal strength at log scale
dBm: absolute measure with 1mW power defined as 0 dBm
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Antenna Basics
Isotropic Dipole High gain directional
0 dBi 2.2 dBi 14 dBi
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Sample RF Propagation• Wi-Fi is invisible• RF does not propagate in
circles• Different vendor products
behave differently• Site layout and construction
have a significant impact
Resulting in• Coverage holes• Dead spots
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VoWi-Fi Deployment Challenges
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Voice over Wi-Fi Deployment Challenges
• Planning
• Monitoring
• Security
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VoWiFi Challenges: Planning
What kind of APs and Antennas ?
Where should APs to be placed?
What is an Optimum network design ?
What is my security exposure?
What is the estimated network performance?
Am I getting a minimum connectivity speed everywhere?
Can I quickly run what-if scenarios?
How many Access Points do I need?
What is the optimal AP configuration to minimize interference and maximize coverage?
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VoWiFi Challenges: Planning
1. Capacity Planning
2. AP Placement and Configuration Planning
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Planning: 1. Capacity Planning
• What type of applications will be deployed? Do they require QoS?
– Data, Voice, Video, other services?
• How much network capacity is needed for each of these application types?
– Dedicated capacity for QoS applications
• What is the projected growth for these applications?
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Planning: Example Capacity Planning
• 200 sqft/user• 8 hour work day• 150 Mb of avg data traffic/user over
WLAN• Peak usage is 3x (i.e. need to
assume 450 Mb data traffic/user)• 0.15 ERLANG of voice load• VoIP connection requires 64Kbps in
each direction
Call radius 50 ft
Users 39
Active Phone Lines 12
Concentration X:1 3.25
Bandwidth (Mbps)
Voice Uplink 0.77
Voice Downlink 0.77
Data Downlink 3.25
Data Uplink 1.63
Total Throughput 6.41Assumes 100% wireless
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Planning: 2. AP Placement Planning
• Determine coverage requirements– Are you coverage limited or capacity limited?– What is the required signal strength?
• How can you ensure proper coverage?– How many APs?– Location?
• What is the optimal AP configuration?– Power, channel, antennas etc
• How do you minimize interference?
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Planning: AP Placement
Which signal coverage are you going to assume?
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Building Material Matters
Material type Attenuation in 2.4Ghz band
6” Brick wall 4.4 dB
Concrete slab 10 dB
Dry walls 4 dB
Cubicle [Wood/Sheetrock]
2 dB
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Building Material Matters
Concrete construction
Dry wall Construction
(better coveragewith fewer
APs)
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APs placed inside
wiring closet[ Incomplete coverage ]
Better Coverage
with 4APs
AP Placement Matters
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AP TX power mattersAP TX power # AP required (for
similar coverage)100 mW 3
50 mW 5
30 mW 7
20 mW 8
5 mW 9
1 mW 10
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Coverage target matters
Coverage target[TX Power 100mW]
Number of AP required
-70 mW 7
-75 mW 5
-80 mW 4
-85 mW 3
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Protocol Matters
• 802.11b– 11, 5.5, 2, or 1 Mbps
• 802.11g, 802.11a– 54, 48, 36, 24, 18, 12, 9, 6
Mbps• 802.11 b/g have a greater
range than 802.11a but only have 3 non-overlapping channels
• Observed throughput is 50% or lower than the link speed
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AP Placement Planning Methods
• Ad hoc deployment
• Best Practices
• Site Surveys
• Predictive Planning
• Predictive Planning with site calibration
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Ad hoc deployment
• Unplanned growth - deploy as you need additional coverage or capacity
• Was good 5 yrs ago
• Works for 1-2 AP ‘Home’ networks
Negatives
Not scalable
Bad Performance
Interference
Less Reliability
Suboptimal AP utilizationLow (No) Manageability
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Best Practices
• Rule-of-thumb planning
• Better than no planning (ad-hoc)
• Good for Small deployments 4-5 AP network
Negatives
Site characteristics are not modeled
Low reliability
Underperforming networkSuboptimal AP Utilization
Can be very misleading
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Site Surveys
• On-site visit to take measurements
• Can take site characteristics into account
• Good for medium to large scale business
Negatives
Cost
Repetitive and Time ConsumingMay not be scalableDoesn’t provide a complete picture
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Predictive Planning• Use of software modeling tools
to predict coverage
• Accurate Results
• Ability to play with ‘What If’ scenarios
• Scalable
• Good for all size deployments
Negatives
Accuracy is only as good as the site model createdMay not be possible to model certain environments
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Predictive Planning with Site Calibration
• Predictive planning combined with a sample on-site measurement
• Good accuracy
• Accounts for modeling and other human errors
• ‘What If’ scenarios
• Scalable
Negatives
Cost – requires site visit
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Increase in Network Performance
Reduction inPlanning Cost
Reduction in Planning Time
Reduction in Equipment Cost
0%
20%
40%
60%
80%
100%
120%
100%
0%
20%
60%
80%
120%
40%
RF Predict Ad-hoc Deployment Best Practices Site Surveys
35%
50%60%
95%
10%
100%
10%3%
100%
10%5%
1%
54%
69% 71%
100%
Predictive Planning vs. Alternative Methods
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Voice over Wi-Fi Deployment Challenges
• Planning
• Monitoring
• Security
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VoWiFi Challenges: Monitoring
• Link capacity fluctuates over time
• Link quality is not guaranteed
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Signal Strength
-90
-80
-70
-60
-50
-40
-30
-20
-10
01 61 121 181 241 301 361 421
Time
RSS
IChannel 3 Channel 4 Channel 5 Channel 10
Signal fluctuates because of multipath fading and people movement.Provision enough link margin ( ~ 10dB) for reliable coverage
Coverage Fluctuates
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Link Capacity Fluctuation
1. Channel is shared & all active devices have equal access to the medium
2. Data/Voice is carried on the same channel and data applications tend to hog all available capacity
• Issue 1 & 2 being addressed by 802.11e
3. Interference from neighbor APs can reduce channel capacity (SIR should be well above 15 dB)
4. Noise from other EM sources can also reduce channel capacity. (SNR ratio should be well above 15 dB)
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Link Quality is not Guaranteed• Packet loss rate is higher due to
• Interference from co-channel and adjacent channel WLAN devices
• Noise from other sources (Microwaves, bluetooth etc)
• Collisions in the medium• Frequent
connection/reconnection due to• Hand-offs• Quality of signal – client may
start scanning for better connection
• Dead spots
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Solution: Live Monitoring
Sample Live Monitoring Charts
Required to ensure on-going optimal network performance
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Voice over Wi-Fi Deployment Challenges
• Planning
• Monitoring
• Security
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VoWiFi Challenges: Security
• Wi-Fi is inherently insecure– Signal bleeds through walls and windows– No central point of control
• Easy to break in if proper security standards are not used– Legacy VoWiFi devices don’t support latest security
standards
• Wi-Fi networks can be easily disrupted– DoS attacks are easy to launch– Usual security precautions don’t work against DoS
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Solution: Live Security
Wireless Intrusion Prevention System (WIPS)
• Provides 24 x 7 security coverage
• Three key functions:– Detects and automatically
classifies wireless events & devices – to determine which are threats are which are not
– Robustly prevents (multiple) wireless threats
– Accurately locates wireless threats
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Deployment Best Practice
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Deployment Best Practice• Plan
• Anticipate performance needs of VoIP application in advance. Deploy/configure WiFi infrastructure to obtain the best possible performance
• Monitor• Monitor for changes that cannot be
anticipated at the planning stage. Adjust network configuration to respond to environment changes
• Secure• Protect against malicious threats that
can disrupt VoIP application• Protect VoWiFi infrastucture
vulnerabilities that can easily be exploited to breach corporate network security
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Deployment Best PracticeFactors affecting WiFi performance
Pre-deployment Planning
Live Monitoring Detect & Prevent Threats
Site layout, construction material
Co-channel interference from deployed AP
Co-channel interference from neighbor APs and clients
Can only be estimated when the network is in operation
Usage, Contention, Traffic
Dynamic and can only be measured when the network is operational
Noise Noise level can change over time
Security (e.g. DoS attacks)
Need to detect & respond in real-time
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Take Away
• Analyze current and future requirements• Use a planning tool to help meet the
requirements• Perform on-site measurements if necessary• Invest in a live monitoring and security system
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Questions?
Plan
Monito
rSecure
VoWiFi