Site Survey Equipment and Utilities - Essay Example

Site Survey Equipment and Utilities Content 1. Introduction 2. Site Survey Tools 3. Equipment required for a site survey Wireless access point Wireless client card Choosing the Right Antenna 1. Omni-directional antennas 2. Magnetic mount dipole antenna 3. Calculating Antenna Site Coverage Site Survey Utility Software 4. Additional Information 5. Advanced tools let you "see" wireless LANs 6. References Introduction Designing and implementing of Wireless LAN, site survey is critical element the main cause or purpose of Site Survey is to determine the number of access points needed to support the users of the wireless LAN, best placement of the access point in the designated location. The first step of deployment of a wireless site survey and most important step to desire for this survey A Radio Frequency (RF) Site Survey, to understand the RF nature ,discover RF coverage area ,checks for RF interference and determines the appropriate placement of Wireless devices a site survey is the step-by-step process which the surveyor studies. Site survey provides a detailed specification addressing coverage, equipment placement, power considerations, and wiring requirements, it also serves as a guide for the network design and for installing and verifying the wireless communication infrastructure. WLANs must provide vast coverage areas, handle extensive traffic, and support a continuously clear, reliable signal in any organization, increasing numbers of companies want their new wireless network to manage converged voice and data communications, or accommodate high data rate transmissions. To needs are met companies should perform a radio frequency (RF) site survey prior to the wireless installation. Site Survey Tools The measurement step of a site survey consists of setting up temporary antennas and access points. The consultant measures every part of the site with a software survey tool –Installed on a handheld computer or laptop, that monitors the signal strength and identifies failure zones. Site survey tools measure performance between access points, identifies sources of interference, helps determine access point placement. Symbol uses a handheld survey system running on a Spectrum24® terminal, and notebook-based tools that run on Windows® 95/98, CE, and NT. For high data rate site surveys, Symbol provides a utility along with its Spectrum24 High Rate Wireless LAN technology. This site survey tool is a 32-bit Windows application that uses both a notebook containing a PC Card and an access point to collect WLAN transmission Statistics in the environment where the network is to be installed. It helps customers to both determine the location and, even more essential for high data rate communications, to calculate the number of access points needed for good coverage and adequate bandwidth. “Many wireless LAN vendors, such as Symbol, offer training for analyzing RF coverage. Symbol’s training also provides students with a copy of the Company’s site survey tool.” Equipment required for a site survey:- Some of the basic equipment and utilities that is required for the completion of a site Surveys include: 1. Wireless access point 2. Wireless client card 3. Laptop or PDAs 4. Variety of antennas (this depends on the requirement of the firm) 5. Site survey utility software Wireless access point A wireless access point (WAP or AP) is a device that connects wireless communication devices together to form a wireless network, in computer networking. The WAP usually connects to a wired network, and can relay data between wireless devices and wired devices in computer networking. Several WAPs can link together to form a larger network that allows "roaming"(In contrast, a network where the client devices manage themselves - without the need for any access points - becomes an ad-hoc network.)Wireless access points have IP. Wireless client card Wireless client adapters are the key to adding mobility and flexibility to an enterprise-increasing productivity by enabling users to have network and Internet access anywhere, within a building without the limitation of wires. The ‘Cisco Aironet’ Client Adapters are a complement to Aironet infrastructure devices, providing an enterprise-ready solution that combines mobility with the performance, security, and manageability that people have come to expect from Cisco. A variety of devices to a wireless network either in ad hoc peer-to-peer mode or in infrastructure mode with APs is connecting by Wireless client adapters. Available in PC Card (PCMCIA) and Peripheral Component Interconnect (PCI) form factors, Cisco Aironet Client Adapters quickly connect desktop and mobile computing devices wirelessly to all network resources. With this product, you can instantly add new employees to the network, support temporary workgroups, or enable Internet access in conference rooms or other meeting spaces. Choosing the Right Antenna To direct radio frequency (RF) power from a radio into the coverage area is the work of a wireless antenna. Different antennas produce different coverage patterns, however, and need to be selected and placed according to site coverage requirements. There are two types of antennas we use: 1. Omni-directional antennas These have a 360° coverage pattern on a horizontal plane. The coverage pattern is torus-shaped (doughnut-shaped), making them ideal for square or fairly square areas. Symbol’s omni-directional Antennas include: Plane antenna Ceiling mount dipole antenna Rubber duck dipole antenna Short rubber duck dipole antenna Spectrum24 Sandra "D" antenna 2. Magnetic mount dipole antenna Directional antennas: - These concentrate the coverage pattern in one direction. This produces an almost conical-shaped coverage pattern, similar to that of a flashlight. The antenna directionality is specified by the angle of the beam width. Typical beam width angles are from 90° (somewhat directional) to as little as 20° (very directional). The directed beam allows for a longer but narrower coverage pattern, which is ideal for elongated areas, corners and outdoor point-to-point applications. Symbol’s directional Antennas include: Yagi antenna (30° beam) Patch antenna (70° beam) Panel antenna (22° beam) Calculating Antenna Site Coverage An increase in coverage within the beam width is called "antenna gain" and is measured in decibels (dB). Gain improves the range of the signal for better communication, each 1dB increase in antenna gain results in a range increase of approximately 2.5%. For an unobstructed outdoor site, each 1dB increase in gain results in a range increase of approximately 5%. Actual results vary depending on the amount and type of obstructions at the site. Site Survey Utility Software Aironet Site Survey Utility 1.3.01 is designed for use by people responsible for conducting a site survey with the CB21AG client adapter. It is useful in determining the best placement of infrastructure devices within a wireless network. The utility is a stand-alone application that runs from an executable file. The utility may function with the Cisco 350 Aironet Client Utility (ACU) Version, however, it has not been tested for such use. Do not call the Technical Assistance Center (TAC) for assistance with this tool when using it with a 350 adapter. Note also that operation with a 350 adapter may be different than with a CB21AG adapter. The table below identifies known differences in functionality. 350 Aironet Client Utility (ACU) Version Description 6.5 and later No apparent differences. 6.4 to 6.0 Signal Quality is always shown as "Beacons Received." 6.3 to 6.0 The Display in percent check box is grayed out. Also, Signal Quality and Overall Link Quality do not appear on the Associated AP Status window. 6.0 RSSI values are shown as positive numbers. To work around this issue, mentally negate the numbers. Also, information element (IE)-based information is not available. Note- Cisco does not support the use of the site survey utility with 350 series client adapters Additional Information a site survey, also consider the following operating and environmental conditions when performing: •Data rates—Sensitivity and range are inversely proportional to data bit rates. Therefore, the maximum radio range is achieved at the lowest workable data rate, and a decrease in receiver threshold sensitivity occurs as the radio data increases. •Antenna type and placement—Proper antenna configuration is a critical factor in maximizing radio range. As a general rule, range increases in proportion to antenna height. •Physical environment—Clear or open areas provide better radio range than closed or filled areas. Also, the less cluttered the work environment, the greater the range. •Obstructions—A physical obstruction such as metal shelving or a steel pillar can hinder the performance of wireless devices. Avoid placing these devices in a location where a metal barrier is between the sending and receiving antennas. •Building materials—Radio penetration is greatly influenced by the building material used in construction. For example, drywall construction allows greater range than concrete blocks, and metal or steel construction is a barrier to radio signals. Advanced tools let you "see" wireless LANs 1 Advanced 802.11 site survey tools include spectrum analysis. Providing the "eyes" and "ears" that let you understand the affects of the environment on the transmission of 802.11 signals. For example, an 802.11b spectrum analyzer graphically illustrates the amplitude of all signals falling within a chosen 22 MHz channel. This enables you to distinguish 802.11 signals from other RF sources that may cause interference and making it possible to locate and eliminate the source of interference or use additional access points to resolve the problem. Another key spectrum analysis feature is the monitoring of channel usage and overlap. 802.11b limits up to three access points to operate in the same general area without interference and corresponding performance impacts. Causing difficulties when planning the location and assignment of channels in large networks. Spectrum analysis displays these channels, enabling you to make better decisions on locating and assigning channels to access points. A handful of test equipment companies are currently developing advanced site survey tools - Berkeley Varitronics Systems (Metuchen, New Jersey) and Softbit (Oulu, Finland) now have products on the market. Softbit's TriCycle. is software that installs on a ‘laptop’ equipped with a radio card and provides a very useful display of nearby access points, association status, signal levels, and has the ability to display coverage areas, this product doesn't get you away from lugging a laptop around, but it certainly has features that decrease the time and increase the accuracy of performing site surveys. Berkeley Varitronics Systems' Grasshopper. has fewer graphical features, but it is a small handheld device weighing only 3 lbs. Because of the higher cost (up to several thousand dollars) of advanced tools, you should only consider them if installing multiple wireless LANs or the wireless LAN environment is complex. Warehouses with lots of high metal racks and manufacturing plants full of machinery will wreak havoc on radio waves. In these cases, you'll find it easy to warrant the additional costs of using advanced tools 1 Jim Geier, November 12, 2001, Tools Simplify 802.11 Deployments http://www.wi-fiplanet.com/columns/article.php/922181 References 1. Wireless Site Survey, FAQ. Document ID: 68666 2. Symbol technologies. RF Site Survey and Antenna Selection for Optimum Wireless LAN Performance. JAN 2000 3. Cisco Wireless IP Phone 7920 Deployment Recommendations 4. http://www.cisco.com/en/US/products/hw/phones/ps379/products_white_paper0900aecd800f6d97.shtml 5. Solution Reference Network Designs: Best Practices for Building a Cisco AVVID Network Infrastructure 6. http://www.cisco.com/warp/public/779/largeent/it/ese/srnd.html 7. Cisco Systems. Site Survey Guide for Deploying Cisco 7920 IP Phones. April 2005. 8. Jim Geier, November 12, 2001, Tools Simplify 802.11 Deployments http://www.wi-fiplanet.com/columns/article.php/922181 9. RF/ Wireless basics, JAN 2006, http://www.lxe.com/pdf/wp_RFBasics2006.pdf Read More