Ch. 9 – Applications, Design, and Site Survey Preparation Cisco Fundamentals of Wireless LANs version 1.1 Rick Graziani Cabrillo College

Ch. 9 – Applications, Design, and Site Survey Preparation

Cisco Fundamentals of Wireless LANs version 1.1

Rick Graziani

Cabrillo College

Rick Graziani [email protected] 2

Overview

Site Survey


Site survey

• A good site survey will help determine the following:

– Feasibility of the desired coverage

– Radio frequency interference

– Wired connectivity limitations

• The process of performing a site survey includes the following steps: 1. Gather tools and configuration. 2. Research and investigate industry specific concerns. 3. Gather the recommended equipment list, or site survey kit. 4. Implement the site survey. 5. Document the site survey.


Site survey considerations



Standards and topologies

• Besides the advantages, know the limitations and restrictions of the standards and technologies.


Standards and topologies

• A site survey engineer is responsible for not only finding the best locations for the APs, but also for finding ways to connect the APs to the wired network.

• Therefore, it is crucial that the engineer have an understanding of wired networks.

• This understanding should cover wired LAN topologies, standards, and components.


Safety Considerations

Applications


Choosing the technology based on the application


Applications, Requirements, Infrastructure

WLAN Design


Design Guidelines

• High availability is achieved through system redundancy and proper coverage area design. – System redundancy includes redundant APs on separate

frequencies. – Proper coverage area design includes accounting for roaming,

automatic rate negotiation when signal strength weakens, proper antenna selection, and possibly the use of a repeater to extend coverage to areas where an AP cannot be used.

• Scalability is accomplished by supporting multiple APs per coverage area using multiple frequencies or hop patterns. – APs can also perform load balancing if desired.

• Diagnostic tools represent a large portion of management within WLANs.

• Interoperability is achieved through adherence to standards such as 802.11a, b, and g, participation in interoperability associations such as Wireless Ethernet Compatibility Alliance (WECA), and certification such as FCC certification.


Applications and data collection

• Copper installations can still provide higher data rates, but price is no longer a factor.

• A WLAN can be installed for roughly the same price as a copper-based network, and it provides many benefits over a wired network.

• As prices continue to decrease on wireless products and throughput speeds continue to increase, wireless will continue to increase in popularity.

• This may also be a factor in the design.


Load and coverage

• The load on an access point or the total number of potential clients should be considered in any design.

• One problem with WLANs is that the number of potential clients can be unknown, since the freedom of wireless allows any number of people to converge within an area.


Bandwidth and throughput

• 2 Mbps units transmit at 2 Mbps, which takes five times as long to transmit the same data as an 11 Mbps product would.

• This means the data rate is only 2 Mbps for any given remote, and the total that the 11 Mbps unit “could” see is 2 Mbps.

• You may want to use more APs which are closer together to make higher data rates more available.


Mobile Users

• Data collection users are also highly mobile users. • That is the advantage of the wireless data collection device. • It enables the end user to freely roam throughout the facility and scan

items instead of having to carry the item to a scanner that is attached to a fixed terminal.

• Coverage must not have holes and must have enough overlap between APs to offer truly transparent roaming.


Power consumption

• CAM (Constant Awake Mode) - Default – Power is not an issue– Always on

• PSP (Power Save Mode)– Power is an issue– AP buffers frames– Wakes up periodically to receive frames

• Fast PSP (Fast Power Save Mode)– Switches between CAM and PSP, whether plugged in or not.

See earlier presentation on Power Save Modes.


Interference

• 802.11 WLANs are unlicensed users of the spectrum, which allows customers to manage their own products and implementations.

• As unlicensed users they must accept interference from other unlicensed users and are not allowed to cause interference to licensed users.


Authentication and Encryption

• Be sure your equipment will support the security features you want to implement now and in the near future.– Can they be upgraded with software or firmware?


Fire code and safety issues

• It is important to use local building, fire, and electrical codes when designing WLANS.

• The National Fire Protection Agency (NFPA), develops, publishes, and disseminates codes and standards intended to minimize the possibility and effects of fire and other risks.

Building-to-Building Design


Building to Building Design

• Much of the information in the module is covered in detail in earlier modules.

• Please refer to the online curriculum for this module and previous modules for more information.


Path Considerations

• Radio line of sight

• Earth bulge

• Fresnel zone

• Antenna and cabling

• Data rate


Line of Sight

• The following obstructions might obscure a visual link:– Topographic features, such as mountains– Curvature of the Earth– Buildings and other man-made objects – Trees

Line of sight!

Rick Graziani [email protected]

Longer Distances

• Line of Sight disappears at 6 miles (9.7 Km) due to the earth curve


Fresnel Zone

Fresnel Zone


Improving Fresnel Effect

Raise the antenna

New structure

Existing structure

Different mounting point

Remove trees


Total Distance

Fresnel @ 60% (Value “F”)

Earth Curvature (Value “C”)

Antenna Height (Value “H”)

Site to Site Fresnel Zone

• Antenna Height– Fresnel zone consideration– Line-of-Sight over 25 miles (40 Km) hard to

implement


Antenna Alignment

Line of Sight


Antenna Issues

•No Downtilt

•One-way communications

High gain omni-directional

Directional antenna


Antenna Issues (cont.)

8 Miles/13 Km

700 ft./213 m

8.50 downtilt

14.50

200

ft.

/61

m

Site Survey Equipment


Site Survey Equipment

• Much of the information in the module is covered in detail in earlier modules.

• Please refer to the online curriculum for this module and previous modules for more information.


Access Points

•802.11b– With RP-TNC

• Reverse Polarity Threaded Naval Connector (RP-TNC)

• 1200 Series Access Point (2.4 GHz)Without RP-TNC• 1100 Series Access Point

•802.11a– 1200 Series with 5 GHz Module

•Survey with correct access point– Customer purchases an 1200 Series

Access Point - survey with a 1200 Series Access Point


Client Cards

• Client Cards• PC Cards• LM Cards

• MMCX Cable Connectors

http://www.rfconnector.com/cbls.JPG


Antennas

•Two of every antenna you may have to use

•Diversity

•Availability of antennas


Battery Pack and Cables

• Battery Pack

• Charger

• Cables– Serial or RJ-45 to DB-

9 roll-over cable– RP-TNC Assembly


Mounting Brackets

•Mounting bracket•Mounting solutions

– Bright color tape– Velcro– Beam clamps– Zip ties

•Secure the access point!


Access Point Markers

•Mark access point and antenna locations

•Bright colors

•Durable but easily removed


Antenna Attenuator

• Difficult to carry one cable of each length

• Splitters, cables, and lightning arrestors add loss

• Duplicate the loss with a single device

http://www.terra-wave.com/Detail.bok/d18e4014e5e3404713?&category=Attenuators&start=1&total=1&no=22


Measuring Devices

• Measuring wheel (horizontal distances)

• Height measurement

• Rope marked in 10’ or 3 meters increments (vertical distances)


Digital Camera

• Easiest way to document unusual situations

• Need to photograph antenna mounting locations & methods


Travel Case

• Portable travel case– Sufficiently padded– Checkable as luggage

• Quick deployment

http://www.terra-wave.com/Detail.bok/d18e4014e5e3425801?&category=Site+Survey+Tools&start=1&total=7&no=3

http://www.pelican.com/product/cases/1650case.htm


Cisco Aironet Site Survey Kit

•Cisco Aironet In-Building Site Survey Kit– Airline approved travel

case– Custom cut foam inserts

•Inventory includes:– Access point with 2 RP-

TNC connectors • 2.4 GHz• 5 GHz Radio module

(optional)


Cisco Aironet Site Survey Kit

•PC Card Adapter with Integrated Antenna– 802.11b – 11 Mbps (2.4

GHz)– Optional 802.11a – 54

Mbps (5 GHz) •2.2 dBi Dipole Antenna•2 dBi Diversity Omni-directional Ceiling Mount Antenna •6.5 dBi Diversity Patch Wall Mount Antenna

Site Survey Documentation and Utilities


Pre-site Survey Form

• Assists you in assessing– Type of survey needed– How long it will take– Equipment needed– Introduction to the

customer’s facility• General fact gathering form


Aironet Client Utility: Site Survey


Link Status Meter

Ch. 9 – Applications, Design, and Site Survey Preparation

Cisco Fundamentals of Wireless LANs version 1.1

Rick Graziani

Cabrillo College

Documents

Ch. 9 – Applications, Design, and Site Survey Preparation Cisco Fundamentals of Wireless LANs version 1.1 Rick Graziani Cabrillo College