© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-1 © 2002, Cisco Systems, Inc. All rights reserved.

2 Wireless Bridges 4-2

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-3 Objectives Upon completion of this module, you will be able to perform the following tasks: Determine the feasibility of installing a wireless bridge link. Explain why a wireless bridge may be a better solution than other alternatives. Determine the maximum distance that can be achieved using wireless bridges with given antennas and extension cables. Identify steps necessary to protect a wireless bridge installation against a lightning strike.

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-4 Bridging Defined

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-5 Wireless Bridge Alternatives Medium Drawbacks Phone lines Recurring costs Installation costs Cable/DSL Physical barriers may preclude High cost Microwave Licensing required Fiber Installation costs 56K, E1, T1 Reliability, Speed, Recurring Cost Installation costs Recurring Cost

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-6 Emerging Markets Bridging Wireless building-to-building bridges Connect separate LANs at high speed No tariff, no recurring fee E1, T1 alternative High-speed internet access (ISP) Educational campuses International markets Developing countries Alternative to wired data infrastructure Rapid deployment with lower cost

Role in Radio Network © 2002, Cisco Systems, Inc. All rights reserved. 7

AWLF 3.0Module 4-8 Role in Radio Network Determines functionality within WLAN Determines which type of clients will be supported File Server Bridge Access Point PC Card PCI Card Workgroup Bridge Bridge

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-9 Parent – Child Relationship (Root Bridge vs. Non-Root Bridge) Root Bridge (Parent): Accepts associations and communicates with Non-Root Bridge (Child) devices Will not communicate with other Root Bridge devices Communicates with multiple Non-Root bridges Root Bridge Non-Root Bridges

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-10 Parent – Child Relationship (Root vs. Non-Root) Non-Root (Child): Can associate and communicate with Root devices or Clients Will not communicate with other Non-Root devices –Unless other Non-Root device is communicating with a parent Root Bridge Non-Root Bridges

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-11 Root Mode: Access Point vs. Bridge Access Point in Non-Root mode Management traffic ONLY via Ethernet Bridge set to Root or Non-Root Able to send traffic via Ethernet or Radio Access Point in Non-Root mode Bridge in Root mode Bridge in Non-Root mode

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-12 Root Bridge Communicates with: Non-Root Bridge Workgroup Bridge Repeater Access Points Wireless Clients Non-Root Bridge Repeater Access Point PC Card Wireless Clients Workgroup Bridge Root Bridge PCI Card

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-13 Non-Root Bridge with Clients Communicates with: Root Bridge Non-Root Repeater Bridges WGB Repeater Access Points Wireless Clients Non-Root Repeater Bridge Access Point as Repeater PC Card Workgroup Bridge Non-Root Bridge PCI Card Root Bridge

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-14 Non-Root Bridge without Clients Communicates with: Root Bridge ONLY Root Bridge Non-Root Bridge

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-15 Bridge Configured as a Root Access Point Same functionality as Cisco Aironet Access Point Supports all wireless clients

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-16 Bridge Configured as a Repeater Access Point Connects to Root bridges Non-Root bridges Root access points Other repeater access points Repeaters are not covered by standards

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-17 Bridge Configured as a Site Survey Client Used to survey access point configured as repeater Will not accept associations from Wireless Clients Repeater Access Point Site Survey Client

Installation Considerations © 2002, Cisco Systems, Inc. All rights reserved. 18

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-19 What Makes Ciscos Bridges Best? Flexibility: point-to-point and multipoint Inline power Management capabilities Radio RX sensitivity SNMP, telnet, FTP, HTML 802.1d spanning tree Breadth of product line 1, 2, 5.5, and 11 Mbps Antenna/range options Price/performance

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-20 PCI Card Access Point to ANY Client - Maximum Distance Bridge to ANY Client - Maximum Distance 1 any data rate 1.6 any data rate 25 2 Mbps 40 2 Mbps Mbps Mbps 25 2 Mbps 40 2 Mbps Mbps Mbps Distances Limited by Specification

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-21 Products: Wireless Bridges Bridge Model 350 Note: Distances over 25 miles or 40 Km are very hard to align and install! Data Rate 11 Mbps dBi Dish Mbps 5.5 Mbps Max. Distance Miles Km Max. Distance Miles Km Optional Antenna Standard Cable (6.7 dB/100 ft. loss) (6.7 dB/30.5 m) Standard Cable (6.7 dB/100 ft. loss) (6.7 dB/30.5 m) 1 Mbps 21 dBi Dish 50 ft (15.2m)/side 20 ft (6.1m)/side 50 ft (15.2m)/side

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-22 Common Questions Cisco Aironet Bridge How Fast? Max data rate 20.5 Miles 33 Km 11 Mbps 5.5 Mbps 3.6 Miles 5.8 Km How Far? Typical throughput Yagi antenna 2 Mbps 1.4 Mbps 7.3 miles 11.7 Km 25+ miles 40+ Km Dish antenna Note: All distances may be limited by governing bodies and standards.

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-23 Front Cover LEDs

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-24 Optional Antennas for Long Range 13.5 dBi Yagi Distances over Mbps Mbps Mbps Mbps 21 dBi Solid Dish For distances up to Mbps Mbps Mbps Mbps Note: Distances include 50 feet of low loss cable and 10 dB fade margin

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-25 Bridge Application: School District Lincoln Elementary Yagi Bode Elementary Yagi Richardson Elementary Yagi Price Elementary Yagi Dewitt Elementary Yagi Bolich Middle School Yagi Roberts Middle School Dish Weaver- Special Education Dish High School 2 Bridges One 12 dBi omni One Dish Administration 2 Bridges One 12 dBi omni One Yagi Channel #11 Channel #6 Channel #1

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-26 Lightning Ethernet Bridge Static Electricity Wind Nearby Strikes

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-27 Lightning Arrestor Designed to protect LAN devices from static electricity and lightning surges that travel on coax transmission lines RP-TNC connectors used on all Cisco Antennas To Antenna Ground Wire From RF Device Lug Lockwasher Nut

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-28 Direct Strike Protection Bridge To Network Copper – Fiber transceivers 1 meter fiber optic cable Protection from a direct strike 1 meter fiber optic cabling Electricity will not travel over fiber Transceivers require power Hub

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-29 Coax Connection Sealing Number one problems with bridges - water in the connectors Proper sealing is important Coax Seal is one product that is inexpensive and works great

Path Loss Considerations © 2002, Cisco Systems, Inc. All rights reserved. 30

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-31 Path Loss Considerations How far will it go? 22 miles/34.5 Km?

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-32 Calculations of Coverage Performance Coax Length 150 ft (45.7)? Coax Length 100 ft (30.5 m)? Wants 11 Mbps data rate Distance = 13 miles (20.9 Km) Towers needed to clear trees and other buildings

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-33 Calculations of Coverage Performance (cont.)

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-34 Bridge Distance Calculations

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-35 Bridge Distance Calculations (cont.)

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-36 Bridge Distance Calculations (cont.)

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-37 Path Considerations Radio line of sight Earth bulge Fresnel zone Antenna and cabling Data rate

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-38 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

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-39 Longer Distances Line of Sight disappears at 6 miles (9.7 Km) due to the earth curve

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-40 Fresnel Zone

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-41 Improving Fresnel Effect Raise the antenna New structure Existing structure Different mounting point Remove trees

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-42 Total Distance 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

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-43 Antenna Alignment Line of Sight

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-44 Antenna Issues No Downtilt One-way communications High gain omni-directional Directional antenna

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-45 Antenna Issues (cont.) 8 Miles/13 Km 700 ft./213 m downtilt ft./61 m

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-46 Antenna Issues (cont.) Antennas have gain in particular directions Direction other than the main intended radiation pattern, are typically related to the main lobe gain

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-47 Antenna Issues (cont.) Omni-directional antennas provide coverage Also accepts interference from all directions

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-48 Interference Carrier Detect Test (Spectrum Analyzer) Built into Bridge Run from Console Menu

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-49 Antenna Installation Towers and antennas may require permits and must meet local regulations

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-50 Antenna Installation (cont.) Antenna Alignment Tool Id Name Address Signal Strength Signal Quality 18 Cisco Bridge # fd35 100% -10 dBm 100% 17 Cisco Bridge # fd35 100% -10 dBm 100% 16 Cisco Bridge # fd35 45% -73 dBm 100% 15 Cisco Bridge # fd35 38% -77 dBm 100% 14 Cisco Bridge # fd35 100% -10 dBm 100% 13 Cisco Bridge # fd35 58% -67 dBm 100% 12 Cisco Bridge # fd35 38% -77 dBm 88% 11 Cisco Bridge # fd35 63% -64 dBm 100% 10 Cisco Bridge # fd35 100% -10 dBm 96% 9 Cisco Bridge # fd35 45% -73 dBm 91%

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-51 Antenna Installation (cont.) Aironet Client Utility Site Survey Utility for antenna alignment

Common Questions and Misconceptions © 2002, Cisco Systems, Inc. All rights reserved. 52

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-53 Common Questions Can I use a bigger antenna with more gain? Can I use an amplifier? Can I have 5 sites at 2 Mbps to a single 11 Mbps center site for better throughput? Can I use a splitter and two antennas? Can I double my distance with a repeater?

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-54 Bigger Antennas If 13.5 dBi is good and….. 21 dBi is better... Is 50 dBi even better??

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-55 Amplifiers? 50 dBm (100 Watts) Cisco Aironet Access Point 20 dBm (100 mW) If this = 25 miles (40 Km)……… WorldLink Amplifier then this MUST = 250 miles (402 Km)!

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-56 Amplifiers and the FCC

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-57 Can I have 5 sites at 2 Mbps to a single 11 Mbps center site for better throughput? Will this give me 10+ Mbps to the center site and 2 Mbps to each remote site? NO - It will only provide 2 Mbps TOTAL or 400 Kbps worst case to each remote. 11 Mbps Bridge 2 Mbps Bridge

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-58 Throughput Questions If data rate is 11 Mbps, why do I only see 5.5 Mbps of data? Throughput = data + overhead 10 Mbps Ethernet has approx. 6 or 7 Mbps throughput Dedicated PipeShared pipe 2 Mbps 11 Mbps

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-59 Two Directional Antennas and Splitters? If I can go 25 miles (40 Km) like this... Then I should be able to go 50 miles (80 Km) here!

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-60 Add a Repeater to Double the Distance? If I can go 25 miles (40 Km) like this... Then I should be able to go 50 miles (80 Km) here!

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-61 Channel 1 Channel 11 Alternative Method of Increasing Distance

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-62 Summary Upon completion of this module, you will be able to perform the following tasks: Determine the feasibility of installing a wireless bridge link. Explain why a wireless bridge may be a better solution than other alternatives. Determine the maximum distance that can be achieved using wireless bridges with given antennas and extension cables. Identify steps necessary to protect a wireless bridge installation against a lightning strike.

© 2002, Cisco Systems, Inc. All rights reserved. AWLF 3.0Module 4-63 Review Questions What are two key differences between bridges and access points? How does the standard effect wireless bridging? What is the maximum EIRP allowed for your country?