Introduction to WiFi & WiMAXIntroduction to WiFi & WiMAX11
Deploying Wireless LAN’s Deploying Wireless LAN’s
33 LAN SummaryLAN Summary
Deploying Wireless WAN’sDeploying Wireless WAN’s
LAN SummaryLAN Summary
Evolution of Wireless Standards
• 802.11b• 802.11a• 802.11g• 802.16a
The Wi-Fi Alliance is a nonprofit international association formed in 1999 to certify interoperability of wireless Local Area Network products based on IEEE 802.11 specification. http://www.wi-fi.org
The WiMAX Forum is a non-profit corporation with a goal of promoting deployment of broadband wireless access networks. Our member companies support the industry-wide acceptance of the IEEE 802.16 standard. http://www.wimaxforum.org
What is 802.11b
• 802.11b, or IEEE 802.11b, is a standard that has been developed by the IEEE (Institute of Electrical and Electronic Engineers), http://standards.ieee.org. The IEEE is an international organization that develops standards for hundreds of electronic and electrical technologies. The organization uses a series of numbers, like the Dewey Decimal system in libraries, to differentiate between the various technology families.
• The 802 committee develops standards for local and wide area networks (LANs and WANs). For example, the 802.3 committee develops standards for Ethernet-based wired networks, the 802.16 committee develops standards for wireless wide area networks (WAN), and the 802.11 committee develops standards for wireless local area networks (LAN).
• 802.11 is then further divided: 802.11b, or Wi-Fi, is a standard for wireless LANs operating in the 2.4 GHz spectrum with a bandwidth of 11 Mbps. 802.11a is a different standard for wireless LANs operating in the 5 GHz frequency range with a maximum data rate of 54 Mbps. Another draft standard, 802.11g, is for WLANs operating in the 2.4 GHz frequency but with a maximum data rate of 54 Mbps.
Standards & Throughputs
•802.11b 11Mbps•802.11a 54Mbps•802.11g 54Mbps
Standards – Frequencies - Throughputs
802.11a 4-8 Non-overlapping
Example Non-Overlapping Channels
1 5735 MHz
1A 5745 MHz
2 5755 MHz
2A 5765 MHz
3 5775 MHz
3A 5785 MHz
4 5795 MHz
4A 5805 MHz
5 5815 MHz
1 5735 MHz
1A 5745 MHz
2 5755 MHz
2A 5765 MHz
3 5775 MHz
3A 5785 MHz
4 5795 MHz
4A 5805 MHz
5 5815 MHz
11 5735 MHz5735 MHz
1A1A 5745 MHz5745 MHz
22 5755 MHz5755 MHz
2A2A 5765 MHz5765 MHz
33 5775 MHz5775 MHz
3A3A 5785 MHz5785 MHz
44 5795 MHz5795 MHz
4A4A 5805 MHz5805 MHz
55 5815 MHz5815 MHz
• Nominal 20 MHz Channel Bandwidth• Total of 9 Channels available (4 non-overlapping)
Deploying Wireless LAN’s
1. How many wireless networked computers can use a single access point?
This depends upon the manufacturer. Some hardware access points have a recommended limit of 10, with other more expensive access points supporting up to 100 wireless connections.
2. Can I have more than one access point?
Yes, multiple access points can be connected to a wired LAN, or sometimes even to a second wireless LAN if the access point supports this.
In most cases, separate access points are interconnected via a wired LAN, providing wireless connectivity in specific areas such as offices or classrooms, but connected to a main wired LAN for access to network resources, such as file servers or the Internet.
3. What is the range of a wireless network?
Typical indoor ranges are 150-300 feet, but can be shorter if the building construction interferes with radio transmissions. Outdoor ranges are quoted up to 1000 feet, but again this depends upon the environment.
Deploying Wireless LAN’s4. Can I use a wireless network to interconnect two LANs?
Yes. Wireless networking offers a cost-effective solution to users with difficult physical installations such as campuses, hospitals or businesses with more than one location in immediate proximity but separated by public thoroughfare. This type of installation requires two or more access points. Each access point acts as a bridge or router connecting its own LAN to the wireless connection. The wireless connection allows the two access points to communicate with each other, and therefore interconnect the two LAN's.
5. Can networking software identify a wireless computer in the same way it can identify an Ethernet computer on the network?
Wireless cards look just like Ethernet cards to your network drivers. In fact, wireless networking cards have unique MAC hardware addresses that are formatted like Ethernet hardware addresses allocated from the same standards organization.
Wireless LAN Site SurveysThe traditional method for performing an RF site survey includes a laptop equipped
with an 802.11 PC Card and site survey software supplied at no additional cost from the radio card vendor. The software features vary greatly by vendor, but a common function among them all displays the strength and quality of the signal emanating from the access point. This helps determine effective operating range (i.e., coverage area) between end users and access points.
For example, after "best guessing" the potential position of access points for adequate coverage and overlap, you verify your thoughts by placing an access point at each location, and then walk around with the laptop while monitoring and noting signal levels. The goal is to verify the maximum distances that will maintain adequate signal levels, generally the value that continues to enable operation at the planned data rate (e.g., 11 Mbps). If the predetermined location of an access point doesn't provide the coverage you had in mind, then reposition or include additional access points and repeat the testing.
Advanced tools let you "see" wireless LANsAdvanced 802.11 site survey tools include spectrum analyzers, like the Air Magnet, 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, making it possible to locate and eliminate the source of interference or use additional access points to resolve the problem.
Wireless LAN Security1. What about security?
Wireless communications obviously provide potential security issues, as an intruder does not need physical access to the traditional wired network in order to gain access to data communications. To protect against any potential security issues, 802.11 wireless communications have a function called WEP (Wired Equivalent Privacy), a form of encryption which provides privacy comparable to that of a traditional wired network. If the wireless network has information that should be secure then WEP should be used, ensuring the data is protected at traditional wired network levels.
2. Aren’t there Problems with WEP
On 802.11 networks, you can enable WEP, which encrypts the body of each frame. This is supposed to keep hackers from viewing sensitive e-mails, user names and passwords, proprietary documents, etc. Hackers can fairly easily decode WEP-encrypted information after monitoring an active network for less than one day.
Consequently, don't depend on WEP for protecting sensitive information. The use of WEP in most cases, nevertheless, is better than no encryption at all, especially if you deploy a mechanism to change the WEP key often. Recent improvements from manufacturers have begun to include AES and 3DES encryption within the radios.
Also it should be noted that traditional Virtual Private Networking (VPN) techniques will work over wireless networks in the same way as traditional
Wireless LAN Summary
Wireless LAN installation is tricky. Unlike wired networks, you can't visualize the wireless medium. The construction of a facility and silent sources of RF interference impact the propagation of radio waves, often in odd ways. This hinders your ability to plan the location of access points. How do you avoid these drawbacks? Perform an RF site survey using appropriate site survey tools that help you plan access point locations for adequate coverage and resiliency to potential RF interference.
There are many wireless LAN security issues that require attention. If and how you handle these problems depends greatly on your security requirements. In some cases, you might want to keep the network as open as possible and only protect files on user PCs. Most other scenarios, however, will likely need much more. It's possible to make wireless LANs very secure with the proper planning and management.
Deploying Wireless WAN’s
Technological improvements in the broadband wireless arena have been rapid and significant in recent years, offering greater performance and flexibility in deployments while reducing investment risks and ongoing operating expenses.
Line-of-SightThe Line of Sight Concept
An optical line of sight exists if an imaginary straight line can be drawn connecting the antennas on either side of the link.
Clear Line of Sight
A clear line of sight exists when no physical objects obstruct viewing one antenna from the location of the other antenna.
A radio wave clear line of sight exists if a defined area around the optical line of sight (Fresnel Zone) is clear of obstacles.
The Fresnel zone is the area of a circle around the line of sight.
The Fresnel Zone is defined as follows:
When at least 80% of the first Fresnel Zone is clear of obstacles, propagation loss is equivalent to that of free space.
Studies & DesignTopology Studies
Topo Studies are a requirement for any outdoor deployment to ensure a proper design for LOS (Line of Sight) or NLOS (Near Line of Sight) Connections.
Link Budget Calculations
Once you determine the distance and topology of your link you must run Link Budgets for each link to ensure proper connection, throughput, and link reliability.
Prior to deployment a site survey including a complete spectrum analysis will help to identify any potential interfering systems and channel space that is best suited for the individual sites.
What is WiMAX or 802.16a?The 802.16/HiperMAN for 2-11 GHz is a wireless metropolitan area network (MAN) technology that provides broadband wireless connectivity to Fixed, Portable and Nomadic users. This powerful OFDM and NLOS technology can be used to backhaul LANs to the Internet, provide inter-campus connectivity, and enable a wireless alternative to cable, DSL, T1’s or even fiber or DS3’s.
It provides up to 50-kilometers of service area range, allows users to get broadband connectivity without needing direct line of sight with the base station, and provides total data rates of hundreds of Mbps per base station - a sufficient amount of bandwidth to simultaneously support hundreds of businesses with T1/E1-type connectivity and thousands of homes with DSL-type connectivity with a single base station.
802.16/HiperMAN Technology Specs
Based on IEEE 802.16 and ETSI HiperMAN - WiMAX selected the common mode of operation of these two standards - 256FFT OFDM.
Concentrated in 2-11GHz Wireless MAN (Metropolitan Access Networks), with the following set of features:
Service area range 50km
Non Line of Sight
QoS designed in for voice/video, differentiated services
Very high spectrum utilization: 3.8 bit/Hz
Up to 280Mbps per base station
True broadband for portable users - based on IEEE 802.16e enables the creation of a ‘CPE-less’ broadband market, providing broadband connectivity for laptops and PDAs with integrated WiMAX technology
Sectorial Cell ArchitectureThe Line of Sight Concept
The growing demand for broadband services on a global scale is clear and uncontestable Businesses, public institutions and private users regard it as an enabling technology and it has become a given requirement for delivering communications services in the Information Age. In last mile markets where traditional cable or copper infrastructures are either saturated, outdated or simply out of reach, Broadband Wireless Access (BWA) technology fills the void admirably, providing highly efficient and cost effective access services for millions
of subscribers who would otherwise be left out of the loop.
The introduction of the Wireless MAN standards (802.16 and HiperMAN) and the guidelines set forth by the WiMAX Forum to ensure its success, will do much to encourage the growth of broadband wireless markets everywhere, benefiting everyone…