Conducting A Site Survey Computer Science Essay

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One of the first considerations facing the enterprise wants to deploy a wireless network - including wireless technologies to adopt and when? This article examines the three current standards, 802.11b, 802.11g and 802.11a, with an eye toward the upcoming 802.11n standard, which promises speeds much higher than those currently available. We also expect both wireless LAN (WLAN) architectures - standalone access points and centrally coordinated access points - and discuss implementation considerations that can help you decide which architecture to adopt in your environment.

To help you decide which products based on standards to implement, you'll want to conduct a site survey which identifies the most appropriate technologies and architectures for wireless to your environment. Before going into more technical details, we will examine what is involved in planning and conducting a site survey.

Conducting a site survey

A key factor in determining the success of a deployment of wireless LAN is a site survey. Before you deploy or expand your wireless LAN, you must understand the needs of users in the current environment. By performing a site survey, you can identify the appropriate technologies to apply; obstacles to avoid, eliminate or circumvent; cover models to adopt, and the amount of capacity. Your site survey should produce a design document that describes the network location of each access point's coverage area, and the 802.11 a, b, g or channel selections for the access point. The network design document should also provide a complete bill of materials, indicating the WLAN equipment and supplies, infrastructure equipment and supplies to provide Power over Ethernet (PoE), and switch ports, and will include a description of each component WLAN providers.

When planning and installing a wireless network, be sure to consult a professional wireless communication to ensure that you comply with the applicable safety and operating restrictions in your country or region

User Survey

what do users need? What are their expectations? What applications are they using? What types of traffic (bursts vs. continuous or continuous) and traffic volumes are present? How densely or sparsely situated are the users? To what extent will they be capable of locating access points?

The workspace

Consider the space that the wireless network will serve. How will it be used? What work, rooms and corridors must be supported by the wireless infrastructure? AutoCAD or similar tool creates a diagram of the working environment.

Obstacles to the signal strength

In general, objects absorb or reflect the signal strength and degrade or block the signal. Identify any obstacles or potential problems in the area to be served. For example:

• Walls - especially if the wall is made of heavier construction materials such as concrete. Note also the firewall in the region.

• Ceiling tiles - especially if they are made of materials such as metal.

• Furniture - particularly pieces that are mostly metal.

• The natural elements - such as water, trees and shrubs - not only outside but also in many lobbies, courtyards and other public spaces.

• Coated glass - clear glass is generally not greatly degrade signal strength. But it may do so if it is coated with a metalized film or a wire mesh embedded in it.

Security considerations

The inherently open wireless access - compared to a wired world - creates significant security issues, first and foremost, user authentication and rights enforcement, and encryption of data. Broadcast signals often travel in public spaces that can be accessed by "listening" for people who have not gone through any type of authentication process

validate their presence on the site. The site investigation should identify the security status of all the locations considered for wireless access.

The security solution must control network access in different ways for different types of users who may be in one place. Some users, such as employees, may be entitled to full access and wide. Other users, such as guests or contractors, may be entitled to more limited access. In a more sophisticated solution, an access controller sits between the access point and network, functioning as a gatekeeper or administrator rights to the network edge. With such a device, for example, employees can access corporate resources, and guests can be granted access to the Internet.

The site assessment should note where guests, contractors or other non-employee users can find, so that appropriate security solutions can be created for these areas.

In the selection of network equipment, it is essential to choose access points that offer a full range of security features the industry has proven that integrate easily into any network design. Your network equipment must provide a standards-based authentication and encryption methods satisfactorily security issues such as confidentiality, authentication and access control. For deployments or existing legacy WEP-based WLAN, or new deployments that are struggling to deploy 802.1X end to end and are therefore not suitable for encrypting the link layer based on the 802.11i standard, robust VPN encryption must be used.

For small networks that operate without a centralized server RADIUS for user authentication, some access points offer built-in RADIUS authentication. Your access points should integrate seamlessly with existing authentication systems.

Signal noise

The noise of wireless phones, wireless headsets and other devices not interfere with a protocol may access point try to send or receive data. The site investigation should identify sources of noise in each signal area of ​​deployment so that the WLAN can avoid at least the existing noise sources.

Signal strength measurement

As part of the study site, make sure you have the proper equipment. This equipment can be relatively simple, including access points, antennas and wireless stations will actually be used in deployment.

Place the access point to places where it is likely to achieve adequate coverage, then measure the result. With the access point in a given location, move the wireless station at different locations and measure the signal strength, noise level, and rates of data produced. Take several measurements at each location to ensure consistent results.

Radiation pattern requirements and special antennas

Identify all buildings of irregular shape, hallways, corridors, and similar limitations that may affect the establishment of access points and antennas. With a selection and placement of antennas, you can extend coverage in desired areas, physical barriers and interference.

For example, if you have a shop with storage bins from floor to ceiling, and you need to allow access wireless network wireless data collection devices such as barcode scanners or other devices handheld wireless interactive, you may need to deploy external directional antennas to focus the wireless coverage between each of these obstacles.

Antennas to ensure more effective coverage in specific areas and can help achieve desired coverage, capacity, and objectives of the bandwidth. A higher gain antenna focuses the energy of the RF in a smaller area to levels higher signal and better signal to noise ratio. This usually gives higher data rates over the area covered by the antenna.

Whether using external antennas and internal antennas for access point, you must consider the physical location of installation. Install access points or antennas so that there are obstacles like some signal as possible and be aware of the fact that the wall or column used for the assembly will have on the radiation pattern.

IEEE standards

IEEE 802.11 - otherwise known as the standard Wi-Fi - is a set of standards for wireless LANs.

The original IEEE 802.11 standard, released in 1997, defines a common access control to the medium (MAC) layer that supports the operation of all wireless LANs based on 802.11 per perform essential functions such as managing communications between radio network cards and access points.

Subsequent amendments to 802.11 define the specificity of physical (PHY) layers, such as 802.11b, 802.11g or 802.11a. The physical layer defines the data transmission for wireless LAN, using different modulation schemes.


Much of the impetus for standardization came from the Wi-Fi Alliance, an organization of technology companies and service dedicated to the adoption of a single universally accepted standard for high-speed wireless local area network thread. In common usage, the term Wi-Fi has come to embrace the standards 802.11b, 802.11g, 802.11a and the physical layer, and products based on these standards.


The IEEE 802.11b is the most popular and widely implemented 802.11 standards family, for reasons including its early availability and price of products supported.

802.11b is a standard that specifies the physical layer operation in the 2.4 GHz industrial, scientific and medical (ISM) unlicensed frequency band, using the spread spectrum direct sequence modulation technique (DSSS).

The number of channels in the 2.4 GHz spectrum offers varies by country according to local regulatory constraints. The FCC defines 11 channels for use in the United States, 13 channels are available for use in most of Europe and 14 are available in Japan. Channels overlap each other, since the centers of adjacent channels are separated by only 5 MHz Consequently, only three channels in the 2.4 GHz band are non-overlapping. Devices that use overlapping channels within range of each other will tend to interfere with one another operation. Interference problems are avoided by the configuration of adjacent access points to operate on non-overlapping channels.

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The limited number of available channels in the 2.4 GHz band imposes a restriction inherent in the capacity of an 802.11b network. (By comparison, 802.11a uses the 5 GHz spectrum, which has up to 19 no overlapping channels in the country according to the rules of regulations governing the use of wireless spectrum.)

Moreover, the manufacturers of other devices can use the 2.4 GHz ISM band without a license, as the wireless device operates within regulatory limits. Interference that may affect the 802.11b devices, including microwave ovens, cordless phones, Bluetooth devices, wireless headsets, garage doors, and other gear - all using the same limited 2.4 GHz.

The 802.11b standard defines a maximum data throughput of 11 Mbps, which provides a realistic maximum throughput of about 4-6 Mbps usable under normal conditions. (Remember that the data rate is not the same speed; access points must manage the protocol overhead, as well as senior management and control should be forwarded to the lowest supported data load

The lower data rates use less complex methods for encoding data. Therefore, they are less likely to be corrupted by interference or signal attenuation.


The IEEE 802.11g is a direct extension of 802.11b that extends the maximum data rate (speed of light) to 54 Mbit / s, which can serve up to five times more users.

The higher speed of signalling is made possible by using a more efficient means of transmission called multiplexing orthogonal frequency division (OFDM). OFDM divides a wide-frequency channel into several sub channels and transmits data in parallel. 802.11g offers a realistic maximum throughput of about 20 Mbps in normal conditions. 802.11g can scale to support data rates of 48, 36, 24, 18, 12 and 9 Mbps.

Because 802.11g uses the same frequency - 2.4 GHz - the 802.11b devices are subject to the same limitations: only three non-overlapping channels and interference from unlicensed, non-hardware protocol. On the positive side, using the same frequency of 2.4 GHz means that 802.11g devices are backwards compatible with 802.11b access points and other devices that companies may already have. However, different modulation techniques to prevent 802.11b and 802.11g coordination between them to avoid collisions by using the same shared frequency. Thus, the presence of a station within range of 802.11b access point forces 802.11g access point to invoke an RTS / CTS (Request to Send / Clear to Send) and CTS protection mechanism to itself. This protected mode prevents simultaneous transmission by devices using the 802.11g and 802.11b (which would result in collisions and retransmissions), but it greatly reduces the overall wireless network. In protected mode, the access point goes down to 802.11b speeds to alert the station 802.11b 802.11g transmission takes control of the media. To serve the station 802.11b access point should use the DSSS (rather than OFDM) and is therefore limited to data rates lower. Execution in protected mode is required by standards 802.11b whenever a station is present.


The IEEE 802.11a offers the same maximum 54 Mbps data rate than 802.11g. But unlike 802.11b and 802.11g, 802.11a operates in the 5 GHz ISM band. This means that 802.11a devices are not subject to interference affecting 802.11g and 802.11b devices, but they are still subject to interference from other products designed to use the 5 GHz ISM band.

The 5 GHz band allocates up to 19 no overlapping channels according to local regulations. The higher data rates, coupled with more non-overlapping channels, allows for higher density deployments (access points in a given area) to accommodate more users and provide greater capacity.

With its high throughput and low end, 802.11a is ideally suited for providing connectivity to densely populated user environments such as computer labs, classrooms, conference rooms, airports or convention centers.

However, 802.11a is subjected to a basic rule of physics: the higher the radio frequency, the greater the range. Because 802.11a operates in the 5 GHz band, the range of the signal is somewhat more limited than that of 802.11b / g, which operates at 2.4 GHz. Radio signals have shorter wavelengths more difficulty penetrating walls and other obstacles. Therefore, access points are usually needed to cover a given area.

Without backward compatibility for the installed base of 2.4 GHz based mainly on wireless clients, 802.11a, by itself, has never gained mass adoption in enterprises or wireless home networks . With the rapid growth of the global wireless industry and technological advances that followed, most of today's mobile devices such as notebooks support both 802.11b / g and 802.11a. To follow suit, most 802.11b access points also simultaneous / g and 802.11a support.


The draft 802.11n standard defines a new physical layer to increase the throughput of wireless LANs. The Working Group N 802.11 (TGN), chartered by the IEEE in January 2004, spent more than two years drafting a new amendment to the 802.11 standard to address the need for higher throughput. The working group was submitted competing proposals by two major industry groups: the WWiSE (World-Wide Spectrum Efficiency) Alliance backed by companies including Broadcom, and TGn Sync, which was supported by Intel and Philips. In 2005, WWiSE and TGn Sync, a third group called MITMOT, merged their respective proposals in a common project.

802.11n is based on MIMO (multiple input / multiple output) OFDM technology, which enables transmission of up to 100 Mbps over a much wider range than earlier versions. MIMO technology uses multiple transmitters and receivers to allow increased flow through full range of spatial multiplexing and increased.

In January 2006, TGn voted unanimously to confirm the selection of a joint proposal for WLAN broadband. The 802.11n standard specifies methods modified to increase the signalling speed wireless local area networks up to 600 Mbps - more than 40 times faster than 802.11b and nearly 10 times faster than 802.11a or 802.11g . It is expected that 802.11n will also offer a better operating distance than current networks.

At its March 2006 meeting, the group sent the TGn draft 802.11n for the comprehensive review of over 500 technical experts from tech companies, academic institutions and government agencies. The IEEE 802.11n standard development project expected to complete its work in developing the project in late 2006, with ratification and final publication of the formal amendment 802.11n in the course of 2007.

As wireless technologies continue to mature and others, it is clearer than ever that the standards of well-trained are the smartest way to ensure that future products meet market needs. The Wi-Fi Alliance and other industry groups have argued strongly against the introduction of "pre-N", saying that there is no way to guarantee these products will be compatible input beginning with the future standard. The Gartner Group has urged companies to "intent to remain with the Wi-Fi products certified" (that is, 802.11a, b, g) and avoid adopting "premature" products based on a specification which is still in flux and likely to undergo changes before its final report ratification.

Autonomous and coordinated centrally wireless networks

In planning your wireless network, you will need to determine which WLAN architectures to adopt in your environment. The two architectures - standalone access points and coordinated at central level - have advantages that are well adapted to different environments.

A wireless network based on autonomous access points, based on the integrated functionality of each access point to allow wireless services, authentication and security. As shown in Figure 2, this network can be characterized as follows:

• All access points into the network to operate independently of each other.

• Encryption and decryption is done at the access point.

• Each access point has its own configuration file.

• The major networks usually rely on a management application such as ProCurve Manager or Airwave Management Platform.

• The network configuration is static and unresponsive to changing network conditions such as interference rogue access points or failure of a neighbouring AP.

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In a coordinated network wireless "thin" access points, or ports radio, have responsibilities much simpler, most heavy loads is performed by a centralized controller that manages functions such as roaming , authentication, encryption / decryption, load balancing, RF monitoring, performance monitoring and location services. Because the configuration is done once, at the controller, adding extra radios to cover areas new office is as simple as connecting them as shown in Figure 3, this type of network can be characterized as follows:

• The activity of AP is coordinated by a centralized wireless controller. Encryption / decryption and authentication are performed at the controller instead of individual access points.

• To maintain the health of the network, the controller can reconfigure the access point settings, if necessary, provide a wireless network self-healing.

• The wireless LAN controller performs tasks such as configuration control, fault tolerance and network expansion.

• Redundancy can be provided by redundant controllers in separate locations that can take control in case of failure of the switch or controller.

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Implementation Considerations

What type of wireless network: centrally coordinated or autonomous AP?

The two architectures autonomously and coordinated centrally have advantages and disadvantages, depending on the age of the wired infrastructure, deployment area, building architecture, and types of applications you want to support. Whichever approach you choose, it is essential that your architecture provide a way to manage your network effectively.

A WLAN access point self is particularly well suited in environments where:

• There is a small isolated area of ​​wireless coverage that requires only one or a few access points.

• It is necessary to bridge wirelessly from a main building site at a branch or a building remote mobile or temporary, like a portable classroom.

However, an operational overhead to manage and maintain a wireless local area network increases with the size of the deployment of wireless LAN. management tools such as wireless LAN Manager and ProCurve Airwave Management Platform to help simplify the configuration and monitoring the local network, but the inherent "independence" of these access points is a challenge in security, configuration control, predictable bandwidth and reliability that users and applications become dependent on a wireless LAN connection always available and reliable.

A centrally coordinated WLAN is well suited for deployments where:

• There are one or several large wireless coverage areas that require multiple radio ports possibly accompanied by several small isolated areas of coverage.

• RF network self-healing is required.

• A stateful failover-redundant solution is required.

In a recent analysis of the market, IDC believes that "dependent" access points - where the network management and other functions are dependent on a centralized controller such as the ProCurve 5300xl Wireless Edge Services Module - "will develop to represent 74% of all business access point shipments in 2009. "2 Moreover, the wireless LAN deployments continue to grow, accommodating a growing number of users, there will be an increasing demand to manage a wide range of security, performance and configuration attributes as one system.

A centrally coordinated network offers many benefits including:

• Reduced operational costs. Centralized management helps ease of deployment and ongoing management.

• Increased availability. In this architecture, it is easier to respond in real time to changes in network performance and peak user demand.

• Better return on investment. Roaming Client and rapid improvements in quality of service enable applications sensitive traffic such as voice over wireless LAN.

AP coordinated deployments are most appropriate for large organizations with an overlay wireless throughout the hotel, across the campus. This type of deployment provides a facility to meet the operational concerns, simplify network management and ensures the availability and resilience - with more users, it is essential to minimize desk calls and trouble tickets.

There are many ways to configure your wireless network. Of course, you will need a certain density of access points to ensure adequate coverage and network capacity. Although many aspects of wireless LAN is similar to a wired LAN and should be managed consistently, some aspects of wireless services are unique. Wireless radio is a shared medium and, as such, requires careful planning use patterns and dynamic changes in capacitance.

Dual-band radios and two radio access points

802.11a/b/g access points with two dual-band radios can simultaneously support both 2.4 GHz (802.11b / g) and 5 GHz (802.11a) radio frequency bands. They are backwards compatible (to preserve existing investments) with a larger number of channels and increased flow accordingly. A radio station with a wireless dual-band typically looks first for an 802.11a access point. If it cannot find one, it searches for an 802.11g, and finally for 802.11b.

APs Dual-band are well adapted to a wide range of network topologies. In addition to the benefits of increased bandwidth, it is quite common to find deployments that use access points to separate dual-band data types on different RF bands. The 802.11a radio access point can traffic services wireless data customers (such as books), while the 802.11b / g radio supports voice traffic to time-sensitive from VoWLAN handsets, reducing data and voice traffic from VoWLAN handsets, reducing the data and voice traffic assertion by creating two networks RF.

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Furthermore, consider an application in which a dual-radio access point is deployed in a temporary building or laptop - for example, in the middle of a quad student, where there is no Ethernet connection. A radio (and the associated antenna) is used for the connecting link to communicate with an access point corresponding to the main campus, and the second radio (and the associated antenna) is used to provide connectivity to users in the coverage area of ​​local wireless.

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For networks where support for 802.11a is not a requirement, you can configure the access points more capable, as the ProCurve Access Point 530, to provide data of high-capacity data and voice. By putting the two radios 802.11g mode, a dual 2.4 GHz access point radio can provide twice the capacity of the network. This approach is particularly well suited when you need to deal with coverage areas with a large number of wireless users, such as adjacent rooms and large lecture halls.

The ProCurve solution

By participating actively and extensively in the standards organizations, ProCurve has demonstrated leadership in developing industry standards, spearheaded most of the work that goes into their training and adoption.

According to IDC, "a strong interoperability, vendor-neutral defence organization and technology ... continue to provide a consistent user experience between products from multiple vendors. "3 Because ProCurve solutions are standards-based, they are interoperable with numerous authentication systems customers, and switches. Companies may take advantage of existing site infrastructure investments without sacrificing security or functionality. The ability to reap the benefits of a secure WLAN infrastructure without retooling the entire network can provide huge savings.

Based on the ProCurve Networking Adaptive EDGE Architecture â„¢, ProCurve networking solutions not only include hardware and software, but also services, support and tools necessary to enable a successful deployment of WLAN infrastructure independently profitable existing. With a lifetime warranty and software updates free, ProCurve Networking products provide investment protection for customers.

The ProCurve Networking Adaptive EDGE Architecture provides unified security and management capabilities for all unified wired and wireless infrastructure, enabling network administrators to easily deploy and centrally manage a secure, yet flexible, multi-service.

Products and complementary technologies

ProCurve understands the importance of centralized management of network and provides a comprehensive set of management tools to support network architectures centralized and autonomous AP network.

For distributed sites, such as remote offices or branches, ProCurve offers access 530, Pointe-à-secure, highly intelligent dual-radio standalone access point that provides a full range of security features proven by the industry that integrate easily into any network design. In addition to supporting dual radio (802.11b / g 802.11a +) customer service operation Dual Band Wireless Access Point 530 can be configured as a dual 2.4 GHz (802.11b / g + 802.11 b / g) access point to provide high capacity data and voice coverage in networks where support for 802.11a is not a requirement.

To accommodate a wide range of traditional deployments, the access point includes both 2.4 GHz and 5 GHz integrated diversity unidirectional antennas for easy deployment as well as external antenna connectors compatible with the ProCurve range of external antennas to extend wireless coverage or wireless connection to remote access points. ProCurve offers a variety of antennas that customers can choose to answer the needs that were identified during the site survey.

The ProCurve Access Point 530 offers a built-in RADIUS authentication server that enables enterprise wireless security 802.11i. This provides enhanced security (such as encryption keys and dynamic periodic rotation of the key) for deployments that can use a remote RADIUS server.

ProCurve 5300xl Switch series offers intelligent edge access control Identity Driven to network resources via wired network connections. Now with the addition of Module ProCurve Wireless Edge Services xl, these same access policies based on roles, dynamically generated by ProCurve Identity Driven Manager, are now being applied across the board wireless. This unified approach to policy management and wireless edge provides security and imposed network access control on each network connection, regardless if a user connects to the network via wireless or via a wired port. The Wireless Edge Services Module provides centralized configuration and RF control over a group of radio ports 210/220/230 and their coverage area corresponding wireless (s).

In conjunction with ProCurve radio ports, the Wireless Edge Services Module provides advanced services such as RF network self-healing, fast roaming and QoS priority to ensure that the WLAN is flexible and reliable. As wireless networking grows, it is easy to increase port capacity radio by purchasing additional software licenses.

Estimating coverage needs and equipment

The following tables can be used prior to the survey results wirelessly to estimate the number of access points, ProCurve radio ports or you might need to cover a given area. The tables show the typical distances that you might find in a typical office environment cell using internal antennas for the ProCurve Access Point 530 and ProCurve Radio Port 230. Many factors determine effective range, including transmitter power and Rx sensitivity of wireless stations that will use the access point, the obstacles to the RF signal, the location of the radio port assembly, etc. However, the figures below should give a reasonable estimate of how many access points budget are required. To identify the exact location of the access point with respect to wireless stations you would need to conduct a site survey as discussed above. Of course, in addition to RF performance, your choice of the location of the access point mounting is likely to be influenced by factors such as aesthetics, physical security and other factors. ProCurve Networking Access Points are fireproof and aesthetic for the office facility.

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Both the ProCurve Access Point 530and the ProCurve Wireless Edge Services XL Module include built-in support for ProCurve Manager Plus (PCM +), including ProCurve Mobility Manager and ProCurve Identity Driven Manager (IDM). Network administrators can easily manage the entire unified network, including wired and wireless devices, and administering security policies and user-based roles that are applied without regard to how and where the user connects to the network.

By providing centralized control of wired and wireless security policies, and centralized management of the wired infrastructure and wireless PCM + also reduces operating costs and increases productivity of information technology ( TI).With simplified management capabilities of the system, PCM + provides centralized visibility, configuration and modification of a generalized WLAN deployment.