I need help for Networking assignment

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Ch4-6.ppt
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Chapter 4-6

Configuring a Point-to-Point Wireless LANs

A Case Study

Introduction

This section presents an example of preparing a proposal for providing a point-to-multipoint wireless network for a company.

The administrators for the company have decided that it would be beneficial to provide a wireless network connection for their employees back to the company’s network (Home network).

Overview

This example problem addresses the following issues:

I. conducting an initial antenna site survey

II. establishing a link from the home network to the distribution point

III. configuring the multipoint distribution

IV. conducting an RF site survey for the establishing a baseline signal level for the remote wireless user

V. configuring the remote user’s installation

I. Antenna Site Survey

The proposed antenna site is on top of a hill approximately 1 km from the home network. A site survey of the proposed antenna site provided the following information.

the site has a tower that can be used to mount the wireless antenna

I. Antenna Site Survey

the site has a small building and available rack space for setting up the wireless networking equipment

there is a clear view of the surrounding area for 6 km in any direction

there is not an available wired network connection back to the home network.

II. Establishing a Point-to-Point Wireless Link to the Home Network

Issue: Cost of the link to the home network

Antenna Selection

Three possible antennas were selected for the wireless

network. These are provided in Table 4-7.

Table 4-7 A sample of 802.11b wireless antennas

Antenna Type Radiation Pattern Range in km Costs

2 Mbps 11 Mbps

A Omni Omnidirectional 7 2 moderate

B Yagi Directional 12 7.5 moderate

C Dish Highly directional 38 18 high

Antenna Selection

Antenna A has an omni-directional radiation pattern. This means that the antenna can receive and transmit signals in a 360o pattern.

Antenna Selection

Antenna B is a Yagi antenna with a directional radiation pattern as shown. The cost of the Yagi antenna is comparable to the omni-directional antenna.

Antenna Selection

Antenna C is a “dish” antenna or parabolic reflector. These antennas provide extremely high directional gain. The cost of the dish antenna can be quite high relative to the cost of the Yagi or omni-directional antenna.

Sector Antenna

Yagi

Omni

Dish

Parabolic

III. Configuring the Antenna Site for Multipoint Distribution

  • At this point, an 11 Mbps wireless data link has been established with the home network. The next task is to configure the antenna site for multipoint distribution.

  • It was previously decided that a 2 Mbps link would be adequate for the remote users. This decision was based on the data rate to be supported for the planned coverage area.

  • The site survey in step I showed that there is a clear view of the surrounding area for 12 km, 6 km is each direction. Antenna A (Table 4-7) provides an omni-directional radiation pattern for 7 km. This satisfies that coverage area and 2 Mbps data rate.

Configuring the Site

  • Antenna A (omni-directional) was mounted on the antenna site tower.

  • An RF site survey of the planned coverage area was next done to verify the signal quality provided by the antenna selected.

  • Measurements were made from multiple locations within the planned coverage area.

IV. Site Survey

IV. Site Survey

V. Configuring the remote installations

  • The antenna for the remote user only needs to be able to see the multi-point distribution antenna site. The requirements for the remote client are as follows:
  • - 2 Mbps data rate connection
  • directional antenna (Yagi)
  • plus mount, lightening arrestor, wireless bridge

Antenna B (Yagi) was selected for the directional antenna. This antenna will provide sufficient RF signal level for the remote user.

Each remote user will need a wireless bridge, and a switch to connect multiple users.

Note: the bridge is set for a 2 Mbps data rate. The set-up for the remote user is shown.

Chapter 4 Summary

  • This chapter has presented an overview of wireless networking. The vendors of wireless networking equipment have made the use of wireless networks very easy to integrate into existing networks.

  • But the reader must understand that the key objective of the network administrator is to provide a fast, reliable, and secure computer network.

  • Carelessly integrating wireless components into the network can easily compromise this objective.

Chapter 4 Summary

The concepts the student should understand from reading this chapter are:

  • The operating characteristics of the 802.11 wireless networks

  • The purpose of access points, wireless LAN adapters, and wireless bridges
  • How to perform a basic site survey on a building

  • How to configure the network for user mobility

  • How to plan a multipoint wireless distribution

Chapter 4 Summary

  • A final note, the new wireless networking technologies have greatly simplified the planning and installation. Anytime you are working with RF (Radio-frequencies) there is a chance of unexpected interference and noise.

  • A well-planned RF installation requires a study of all known and a search for any possible interferences. An RF study will also include signal path studies that enable the user to prepare a well thought-out plan and allow an excellent prediction of received signal level.

  • The bottom-line is to obtain support for conducting an RF study if needed.