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# Wireless LAN Overview: Intel(R) PRO/Wireless 2200BG User's Guide

About Wireless LAN Technology

- Choosing a WLAN
- Configuring a WLAN
- Identifying a WLAN
- Surveying the Site of Your WLAN
- Factors Affecting Range

A wireless network connects computers without using network cables. Computers use radio communications to send data between each other. You can communicate directly with other wireless computers, or connect to an existing network through a wireless access point. When you set up your wireless adapter, you select the operating mode for the kind of wireless network you want. You can use your wireless adapter to connect to other similar wireless devices that comply with the 802.11 standard for wireless networking.

### Choosing a Wireless LAN

Wireless LANs can operate with or without access points, depending on the number of users in the network. Infrastructure mode uses access points to allow wireless computers to send and receive information. Wireless computers transmit to the access point, the access point receives the information and rebroadcasts it to other computers. The access point can also connect to a wired network or to the Internet. Multiple access points can work together to provide coverage over a wide area.

Peer-to-Peer mode, also called Ad Hoc mode, works without access points and allows wireless computers to send information directly to other wireless computers. Ad Hoc Mode is only supported in 802.11b and 802.11g networks. You can use Peer-to-Peer mode to network computers in a home or small office or to set up a temporary wireless network for a meeting.

### Configuring a Wireless LAN

There are three basic components that must be configured for an 802.11 wireless LAN to operate properly:

- Network Name: Each wireless network uses a unique Network Name to identify the network. This name is called the Service Set Identifier (SSID). When you set up your wireless adapter, you specify the SSID. If you want to connect to an existing network, you must use the name for that network. If you are setting up your own network you can make up your own name and use it on each computer. The name can be up to 32 characters long and contain letters and numbers.
- Profiles: When you set up your computer to access a wireless network, the wireless client manager creates a profile for the wireless settings that you specify. If you want to connect to another network, you can scan for existing networks and make a temporary connection, or create a new profile for that network. After you create profiles, your computer will automatically connect when you change locations.
- Security: The 802.11 wireless networks use encryption to help protect your data. Wired equivalent privacy (WEP) uses a 64-bit or 128-bit shared encryption key to scramble data. Before a computer transmits data, it scrambles the data using the secret encryption key. The receiving computer uses this same key to unscramble the data. If you are connecting to an existing network, use the encryption key provided by the administrator of the wireless network. If you are setting up your own network you can make up your own key and use it on each computer.
  - Wi-Fi Protected Access (WPA) is a security enhancement that strongly increases the level of data protection and access control to a WLAN. WPA mode enforces 802.1x authentication and key-exchange to strengthen data encryption. WPA utilizes its Temporal Key Integrity Protocol (TKIP). TKIP provides important data encryption enhancements that include a per-packet key mixing function, a message integrity check (MIC) named "Michael", an extended initialization vector (IV) with sequencing rules, and a also re-keying mechanism. Using these improvement enhancements, TKIP protects against WEP's known weaknesses.
  - Cisco Client Extention (CCX) is a server and client 802.1x authentication via a user-supplied logon password. When a wireless access point communicates with a Cisco LEAP-enabled RADIUS (Cisco Secure Access Control Server (ACS) server), Cisco LEAP provides access control through mutual authentication between client wireless adapters and the wireless network and provides dynamic, individual user encryption keys to help protect the privacy of transmitted data.

### Identifying a Wireless Network

Depending on the size and components of a wireless LAN, there are many ways to identify a wireless LAN:

- The Network Name or Service Set Identifier (SSID): Identifies a wireless network. All wireless devices on the network must use the same SSID.
- Extended Service Set Identifier (ESSID): A special case of SSID used to identify a wireless network that includes access points.
- Independent Basic Service Set Identifier (IBSSID): A special case of SSID used to identify a network of wireless computers configured to communicate directly with one another without using an access point.
- Basic Service Set Identifier (BSSID): A unique identifier for each wireless device. The BSSID is the Ethernet MAC address of the device.
- Broadcast SSID: An access point can respond to computers sending probe packets with the broadcast SSID. If this feature is enabled on the access point, any wireless user can associate with the access point by using a blank (null) SSID.

### Surveying the Site of Your Wireless LAN

Conducting a site survey for your wireless LAN is the most crucial step in the process of setting up a wireless network. It greatly reduces the amount of troubleshooting you will have to do once you have the wireless LAN set up and ready for connection testing. To conduct a site survey, you will need the following tools:

- An access point (or laptop computer) that is set up to be the transmitter. It should be mounted near and at the same height as the designated location of your wireless LAN.
- A laptop that will act as the mobile receiver. It must contain your site survey software.
- An area or building map, which will be used to plot the strength of your signals.

Once you have the tools you need, you are ready to survey the inside of the building. Launch the site survey software on the mobile receiver laptop and carry it around in the intended wireless LAN area to test the signal strength. Be sure to also check the signal strength of each intended access point location. If you encounter problems while surveying the site, make sure your transmitter laptop is not located on a wall containing metal, such as an air-conditioning duct, which will interfere with the range of your signal. Simply move the transmitter and test the signal strength again. For users to have seamless coverage when moving from access point to access point, the signal levels at each point must overlap. There is software available that will seamlessly hand off changing signal levels from one access point to another.

Your building's infrastructure can sometimes interfere with the microwave signal, but finding the location and cause of the interference will allow you to figure out the best place to mount your access points for optimal area coverage. Microwave signals travel in all directions, which means there is one access point for a multi-floor building. However, the range is highly dependent on the material used to construct the flooring, especially metal materials. Once your signal strength is strong inside the building, you are ready to check the strength outside the building. To do so, simply carry the mobile receiver laptop as far down the street or around the building as you can go without losing significant signal strength. If possible, you should be aware of the types of networks being used by the companies on the floors above and below you, so that you can work together in harmony. With wireless networks, security is very important and if you communicate with those around you, you are better prepared to select the right channels, as well as the best location for access points.

### Factors Affecting Range

Although access points can transmit signals up to 60 feet away in an area with many walled barriers or as much as 500 feet away in a large open area, the range is affected by the following factors:

- Building materials, such as steel and drywall, can shorten the range of the radio signals.
- Physical layout of the area can interfere with the signals and cause them to be dropped.
- Electronic noise from cell phones, microwave ovens, or other devices on the same frequency can interfere with the transmission of the signals.
- Range is inversely proportional to data rate, so the faster that the signals are sent, the less distance they will travel.

Taking these factors into consideration when you survey the site for your WLAN is key to providing all of your users with undisturbed mobile connectivity. Using multiple access points will, of course, reduce the impact of these factors if your area has dividing walls throughout.

### What is a Site Survey?

A site survey is an in-depth examination and analysis of a proposed wireless LAN site. The purpose of a site survey is to determine the number of access points needed, the types of antennas needed, and the best placement for those access points and antennas. Although the goal of a site survey is simple, the means of arriving at that goal are not. Some of the steps involve taking measurements, but most involve experience, trial and error, and a little guesswork rather than numbers and figures. When to Perform a Site Survey Intel® recommends that you perform a site survey prior to installing a wireless LAN. Site surveys are especially important when:

- You are installing a new site: Evaluate the placement of the access points and antennas throughout the proposed site.
- You are changing an existing site: When modifying or extending an existing network structure, re-evaluate the placement of the access points and antennas. If you need a different level of coverage in some areas, you may need to move, replace, or supplement access points and antennas.
- You are physically changing the site: Remodeling may introduce new sources of interference, such as motors and metal structures within the coverage area of the access point, even if it does not directly effect the sites where the access points are located.

## Elements of an Effective Site Survey

An effective site survey requires four elements. Failure to commit the appropriate time, money, and energy to accomplish a proper site survey in advance may result in greater expenditures of money and time later, when problems arise that require repeated adjustments to the wireless configuration. The three elements of an effective site survey are:

1. Examine the network usage problems solved by the wireless LAN.
   How many clients need a wireless LAN connection? What areas of the site require wireless LAN connectivity? How many hours each day is wireless LAN connectivity required? Which locations are likely to generate the largest amount of data traffic? Where is future network expansion most likely?
2. Study blueprints of the proposed wireless LAN site.
   A site blueprint provides a map of the site as well as the location of objects, such as walls, partitions, and anything else that could affect the performance of a wireless LAN. Examining the site blueprint prior to conducting the physical walk-through helps you identify areas in which wireless equipment is likely to perform well and areas where it is not. Many obstructions are not readily visible and, in some cases, a room originally built for a specific purpose, such as a radiology lab, might have been converted into something completely different, such as a conference room. The blueprint may also show areas proposed for future building expansion. To prepare for the next step of the site survey, mark possible wireless device locations on the blueprint and refer to the marked blueprint during the physical walk-through and inventory.
3. Conduct a physical walk-through and inventory.
   The primary purpose of the physical walk-through is to document any items or materials near a proposed device location that may interfere with reception or transmission and affect network performance. Document stock and inventory levels, current environmental conditions and any materials that may interfere with the wireless LAN.

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