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Implementation and Configuration of Wireless Networks (WLAN)
Running head: IMPLEMENTATION AND CONFIGURATION
Implementation and Configuration of
Wireless Local Area Networks Capella University
School of Technology
Abstract This paper examines the framework of WLAN technology, the IEEE 802.11 a – g and briefly discusses IEEE 802.15 technology establish by Bluetooth. Next, the author examines four popular wireless technologies Bluetooth, IrDA, HomeRF or SWAP, and WiFi. Finally, it discusses the implementation and configuration of a wireless local area network (WLAN). Implementation and Configuration of
Wireless Local Area Networks
Introduction The implementation and configuration of a WLAN requires careful planning. Before and installation can go forward, the designer must evaluate the clients business and technical needs. The designer must be able to identify and analyze customer's business problems and design a solution. Other considerations include possible modification of building infrastructure, additional software, and WLAN technology. In view of the fact that this installation and configuration is a hypothetical, examination of WLAN technology supersedes the client’s needs.
According to Cisco Systems, there are over eighteen wireless technologies. The size and cost of the network can range from two or three computer home office implementations for under $200 for home small office system (Truelove, 2002) to Wireless Local Area Networks (WLAN) that sells for $500,000 per data link. Frequencies of the different technologies can travel between a few hundred feet to 25 miles (Cisco System, 2004).
A wireless LAN or WLAN is a wireless local area network that uses radio waves to carry a signal instead of copper or fiber optic cables. A thorough examination of all eighteen technologies would be beyond the scope of this term paper. Rather, this term paper will examine four popular wireless technologies IrDA, HomeRF, Bluetooth, and Wireless Fidelity, better known as Wi-Fi, and how they are utilize LAN technology.
The WLAN technology was standardized the Institute of Electrical and Electronics Engineers (IEEE) in the document IEEE 802.11. The original standards issued in 1999 specified WLAN operation at the 2.4 Giga Hertz in the unlicensed industrial, scientific, and medical (ISM) designated bands (Truelove, 2002).
The 802.11 family of standardization include three separate protocols 802.11a, 802.11b, and 802.11g; and, the other standards in the 802.11 family (c-f, h-j, n) are service enhancement and extensions, or corrections to previous specifications and the 802.15 family of technology standards(Wikipedia, 2004).
IEEE 802.11 Standards
The 802.11 IEEE standard defines three implementation options, Infrared technology (IrDA), Direct Sequence Spread Spectrum (DSSS), and Frequency Hopping Spread Spectrum (FHSS) with a shared data rate of 2 Megabytes per second (Mbps) (Coyle, 2001).
The IEEE 802.11 standard also placed limitations on the both the physical (PHY) and medium access control (MAC) layers of the network. The PHY layer, which actually handles the transmission of data between nodes, can use either direct sequence spread spectrum, frequency hopping spread spectrum, or infrared (IrDA) pulse position modulation (Lough, Blankenship, & Krizman, 2004).
The MAC, a sublayer of the Data Link Layer of the OSI model, is a set of protocols that ensures signals sent from different stations across the same channel don't collide (Webopedia, 2004). The IEEE 802.11 MAC also, specifies the Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol to control the wireless LAN access (Coyle, 2001).
The United States Military developed Spread Spectrum radio techniques during World War II as method to overcome radar jamming on torpedo guidance systems. In summary, the signals in spread spectrum broadcasting, from the signal sender and to the receiver, hopped from frequency to frequency to avoid jamming. The signals of WLAN broadcast, the signals have the same intent as their WWII counterparts. Instead of guidance instruction to ordinance, data for computer consumption is superimposed on an ever-modulating radio carrier wave, to insure radio transmission. Several types of spread spectrum techniques are available. The most prevalent techniques are Direct-sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS)(Truelove, 2002).
In the original IEEE 802.11 documents, Direct-Sequence Spread Spectrum (DSSS) radio techniques spread a signal across broadband radio frequencies simultaneously. Each bit of the transmission is a redundant pattern called a chip. The longer the chip, the more likely the data can be recovered. Longer bits require larger bandwidths. In 1999, DSSS speed was 1 (Mbps).
Frequency-Hopping Spread Spectrum (FHSS) transmits data over a narrowband that cycles through frequencies. The sender and the receiver know the frequency pattern used. The idea is to insure transmission recovery in the event one frequency is block. Top throw put for FHSS is 2 Mbps. The IEEE addendum 80211b specifies the bandwidth at 11 Mbps. The IEEE addendum 802.11a for ISM broadcast at the 5-GHz increased speed to 54 Mbps Mallick, 2003).
The 802.11 MAC specification for Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol are as follows: In the CSMA/CA protocol, when a node receives a packet to be transmitted, it first listens to ensure no other node is transmitting. If the channel is clear, it then transmits the packet. Otherwise, it chooses a random "back-off number" which determines the amount of time the node waits before it is allowed to transmit its packet. When broadcast channel is clear, the transmitting node counts down its back-off number. (When the channel is busy, it does not decrement its back-off number.) When the back-off counter reaches zero, the node transmits the packet.
A similar collision protocol, Carrier Sense Multiple Access with Collision Detection (CSMA/CD) is used by wired Ethernet. CSMA/CD, However, is not used for radio frequency transmissions. The primary reason being the transmitting node cannot hear other nodes in the system that may be broadcasting, because its own signal drowns out any incoming signals at the node (Lough, Blankenship, & Krizman, 2004).
The IEEE specified two 802.11-based WLAN methods: peer-to-peer (ad hoc) or client/server (infrastructure). Figure 1 illustrates the characteristics of an ad-hoc network that 802.11 specify clients can talk with similar clients in the same general vicinity. There is no network structure nor are there fixed access points. In networks of this type every node is able to communicate with every other node, this setup is good for mobile LANs.
Figure 1 Ad-hoc Network(Bing, 2000)
The infrastructure network, shown in figure 2, illustrates the connection involves a wireless access point that acts as a bridge between the wireless clients and the wired LAN. Two access points are located near each other; require they must communicate on different channels in order to avoid radio interference (Net World Fusion, 2004).
Figure 2 Infrastructure Network (Bing, 2000)
802.15 Standards
The IEEE defines the MAC and PHY specifications for a wireless connectivity of devices that are either fixed or portable with the personal computing space. The specifications also consider the coexisting requirements of the IEEE 802.11 wireless local area networks. The 802.15 specifications are based upon Bluetooth. More specifically this standardization was developed, because of Bluetooth technology for short ranged automatic discovery devices (Mallick, 2003).
Infrared Technologies
Infrared (IrDA) LAN technology uses part of the electromagnetic spectrum just below visible light as a transmission medium. For that reason, IrDA wavelengths possess the same advantages and disadvantages as visible light. Infrared light travels in straight lines; an IrDA receiver not in line of sight of an IrDA transmitter will not hear the signal. IrDA signals cannot turn corners; signals do not bleed into other venues. Neither can they penetrate opaque (paper or cardboard) or physical obstructions. Plain glass, sunlight, and shadows greatly affect IrDA transmission. IrDA technology is more secure than other LAN technologies because of its drawbacks. IrDA technologies for Wireless Local Area Networks employ either directed beam or diffused beam technology (Bing, 2000).
Directed IrDA
In directed beam IrDA LAN, transmitters are aimed at each other to achieve a line of site connectivity. The transmitters utilize a narrow IrDA beam. The majority of directed beam IrDA LANs provide connectivity in Token Ring or Ethernet. Directed beam IrDA technology is applied to laser beam LANs. The data rate for IrDA technology varies from one to 155 Mbps with a maximum range from one to five kilometers.
High performances IrDA LANs are primarily used only to augment wired networks. Directed beam IrDA is not an ideal technology for mobile nodes, because the line-of-sight alignment requirement between the receiver and transmitter (Bing, 2000).
Diffused IrDA
Diffused Beam IrDA LAN systems do not require line-of-sight connectivity. Diffused beam IrDA transceivers flood the room with reflected infrared light. The IrDA signals bounce off the walls, floors, and ceiling to fill the coverage area with infrared energy. A simple description of a typical infrastructure IrDA LAN has the WLAN access points housed in the ceiling and the transceiver (antenna) pointed toward the ceiling. The advantage of this approach is that an access point can communicate to multiple transceivers without degradation of signal. The disadvantages to this method of data transference are reduced speeds. The maximum range for diffused LAN connectivity is 10 to 20 meters. The maximum data rate for a diffuse LAN is four Mbps. It is not a technology for outdoors (Bing, 2000).
Bluetooth
Bluetooth is discussed in this paper because it operates in the 2.4-GHz frequency ranges specified by the IEEE 802.11. Bluetooth operates at a range of 10 meters. It uses the unlicensed 2.4-gigahertz (GHz) spectrum for communications. Its maximum throughput is approximately 720-kilobytes per second (Kbps)
Bluetooth is a wireless technology that takes its name from the Viking warrior Harald Bluetooth known for unifying Denmark and Norway. Like the legendary Bluetooth, Bluetooth technology brings together cell phone, computers, PDAs, printers, and other devices to form a close-distance, wireless network.
Bluetooth developed by Ericsson in 1994 as a mean of using a cellular telephone headset without wire. In 1998, Ericsson formed a partnership with Nokia, IBM, Intel, and Toshiba to form the Bluetooth special interest group (SIG) (Coyle, 2001).
Unlike IrDA, Bluetooth does not require a line of sight connectivity to be effective. It utilizes a technology known as auto-discovery (Mallick, 2003). Briefly, in auto-discovery, Bluetooth automatically discover other Bluetooth devices. Bluetooth specifications define three modes of auto-discovery: General discoverable mode, Limited discoverable mode, and Non-discoverable mode.
The General discoverable mode allows a Bluetooth device to be discovered by any other Bluetooth device. In The Limited discoverable mode, Bluetooth allows only well defined devices to be able to detect a device. In The Non-discoverable mode, Bluetooth makes a device invisible to other devices so it cannot be detected (Mallick, 2003).
Bluetooth technology creates ad-hoc networks called piconets. Piconets have a size limit of eight devices. Figure 3 illustrates a Bluetooth piconet. A piconet is formed when at least two devices, such as a portable PC and a cellular phone, connect. A piconet can support up to eight devices. When a piconet is formed, one device acts as the master while the others act as slaves for the duration of the piconet connection. Another name for Piconet is Personal Area Network (PAN)(Webopedia, 2004).
If more than 8 participants want to take part in a Bluetooth session, several Piconets have to be connected. This kind of network is called scatternet
Figure 3 Piconet (Fujitsu Computer Siemens, 2002)
In a scatternet configuration, not all devices are visible to one another. Only devices with the individual piconets can communicate. In figure 4 there is one scatternet consisting of five piconets. The hands-free mobile telephone is a member of three different piconets and is able to communicate with the headset, the Bluetooth pen, and the access point, but not with the laptop, printer, or facsimile machine.
Figure 4 Scatternet (Mallick, 2003)
Bluetooth Technology is not a competitor in the market place for wired LAN replacement. Instead, because of its low speeds and limited range, experts consider Bluetooth a complimentary technology that replaces close range cable technology. Furthermore, results of Bluetooth testing with IEEE 802.11b standards indicate degradation of services unless Bluetooth transceivers are within 3 meters of each other (Coyle, 2001).
SWAP: The HomeRF Standard
SWAP, Shared Wireless Access Protocol, is a wireless LAN protocol for the home office or small office. The HomeRF Working Group (HRFWG) is a consortium of over 90 companies conforming to the IEEE 802.11 standards for home and small office wireless computing (Coyle, 2001).
SWAP can operate at 10 Mbps on the 2.4-GHz frequency band. The range of a SWAP network is about 50 meters. It incorporates Digital Enhanced Cordless Telephony (DECT) that permits use of a cordless phone (Mallick, 2003). SWAP uses the CSMA/CA and Time Division Multiple Access, which guarantee bandwidth and latency. These are important criteria for real-time voice streaming and media streaming (Coyle, 2001). The major advantage of SWAP over WLAN is price. SWAP access points, routers, and switches are much less expensive than comparable WLAN equipment.
Wi-Fi
Wireless Fidelity, Wi-Fi, is the final wireless technology discussed in this term paper. The term Wi-Fi translates to mean wireless fidelity. It compliments the IEEE 802.11x, where x is a, b, or g standards for wireless computing. The Wireless Ethernet Compatibility Alliance (WECA) certifies Wi-Fi industrial standards (WiFi Consulting, 2004).
Typically, when you sit down at a workstation, the computer is wired to a network via a hub, router, or switch. The mobility of the worker in a wired network is limited the workstation cubicle or desktop. The WiFi definition simply put means replacing the wires with a low powered two-way radio (Ohrtman & Roeder, 2003).
The most popular Wi-Fi implementation is based upon DSSS radio technology. Wi-Fi is also available in the IEEE 802.11a at 5-GHz with Orthogonal Frequency Division Multiplexing (OFDM) implementation (Mallick, 2003). The IEEE 802.11b specification allows for the wireless transmission of approximately 11 Mbps of raw data at distances from several dozen to several hundred feet over the 2.4-GHz unlicensed band. The distance depends on impediments, equipment, and line of sight (WiFi Consulting, 2004).
The IEEE 802.11a implementation has two distinct advantages over 11b. First, it increases the bandwidth from 11 Mbps to 54 Mbps. Second the bandwidth to available at 5-GHz range is larger decreases more simultaneous users with transmission conflicts. The downsides of the 5-GHz frequencies equate to shore ranges and increased cost. To maintain quality of service more access points must be maintained, the higher the frequency the shorter the range of the access points. A Second disadvantage of OFDM is its higher operating frequency, higher operating frequencies require greater power consumption; increased power equates to shorter battery life for mobile computers (Mallick, 2003).
Each radio in a Wi-Fi implementation may act, depending on software, as a hub for computer-to-computer communication, as in an ad-hoc network. However, a more likely scenario for a Wi-Fi enabled workstation is in conjunction access points to connect with a wired network, infrastructure network, to access data. The access point often includes routing, DHCP server, NAT, and other features necessary for small to large business operation (WiFi Consulting, 2004).
Implementation and Configuration
When deploying a WLAN, pay close attention to the equipments ability to grow and be updated. Avoid schemes that exceed the IEEE standards for the chosen technology be it 802.11a, b, a & g, or g. Avoid proprietary schemes that appear to be innovative but really put a lid on the scalability of the equipment and the network.
Another important point to remember Choose the latest technology, that has redundancy, scalability and interoperability (Broadcom, 2004).
Of the four networks discussed in the previous sections, only Wi-Fi has had commercial success. The most prevalent implementation of Wi-Fi is as an adjunct to a wired backbone in 802.11b. A second standard 802.11g is gaining popularity and is slightly more expensive than 802.11b. IEEE 802.11g operates at 5-GHz and has speed of 54 Mbps and a range of 150 feet indoors (Wi-Fi Standards, 2004).
The 802.11g standard encodes its data in the same manner as 802.11a with OFDM. 802.11g is fully compatible with 802.11b. The major stumbling block to commercial success is the IEEE’s final ratification. A second obstacle to widespread acceptance of 802.11g is the failure of WECA to certify the protocol.
The biggest advantage 802.11g has over 802.11b is the way the receivers handle signal reflection. Like the 802.11a receivers, 802.11g receivers adjust to signal reflection in a way that enables receivers to handle these reflections in a simpler but more effective way than 802.11b (Engst & Fleishman, 2003).
Beyond the selection of the 802.11 protocols the WLAN operates, WLAN implementation requires three components an access points, network interface card (NIC) with low powered radio, a hub or a switch that will allow communication with other members of the LAN and a switch or a router that will connect with the wired network or the Internet (Truelove, 2002).
Cisco has several models of Access points, for this paper, the Cisco Aironet 1100 series is the model for discussion. The access point uses a small low powered radio certified for 802.11b that can easily be upgraded to 802.11g.
The access point serves as a connection point between wireless and wired LAN or as a stand-alone wireless network. Aironet can be configured using the standard Cisco IOS command-line interface (CLI) or with Simple Network management Protocol (SNMP). Figure 5 and accompanying chart, on page 17, illustrates the interfaces of the Aironet 1100.
The Aironet 1100 can be configured in three modes that as a root unit, a repeater, or as a stand-alone all wireless network. For this term paper purposes Configuration as a root unit will be explored.
To install the Aironet 1100 for the first time, please take the following steps: First make sure the computer is connected to the wired LAN as the AP. Then obtain from the network administrator the device’s service set identifier for the LAN. Next be sure the device is connect to the DHCP server, and has a unique IP address for the access point. Finally get from the network administrator the SNMP community name.
Figure 5 Access point layout and Connectors (Cisco Systems, 2002)
Or you can use the IP Setup Utility (IPSU) on the device to find the IP address and find the MAC address from the label on the bottom of the access point box. Also, the IP address can be configured using the Telnet feature or through a Web browser.
After the access point’s IP address is assigned, browse the Express setup page and perform initial configuration. Follow the seven steps described in the configuration manual. From there, configure the VLAN, WEP, radio setting, QoS, and SNMP (Cisco Systems, 2002).
The third component of a WLAN is the router or switch that allows the clients on the network to communicate with each other. Once again, Cisco provides the equipment for this discussion. Instead of a router, seamlessly tie the network in with the wired components. Allow the wired system the responsibility for security, user-password authentication, VLANs, routing and switching. In June of 2003, Cisco unveiled a WLAN strategy called Structured Wireless-Aware Network (SWAN). The ideal behind SWAN is to distribute WLAN functions to various devices in the net. Cisco engineers say some functions are best done on access points, and the adaptation of IOS for these devices makes them easily programmable, and visible to Cisco network resources, such as network management and network security products (Cox, 2003).
According to Cisco, regular VPN will fail in a hierarchical network. The prime reason, remember the client moving from office to office, floor to floor, or even building to building. If users are moving across subnets, you have new challenges to consider. Some operating systems (such as Windows XP and Windows 2000) support automatic Dynamic Host Control Protocol (DHCP) release/renew to obtain the IP address for the new subnet. To resolve the problem Cisco Recommends putting remote users on flat networks where all the access points on the same segment (Alexander & Snow, 2002).
Conclusion
In conclusion, the best WLANs employ technology that is suits the company’s business and technical needs. The equipment employed is robust, state-of-the-art and upgradeable. Remember the 802.11b, ratified in 1999, offered 11 Mbps. Five years, later, 802.11g is about to replace 802.11b with faster speeds, backwards compatibility, and more flexibility for the standard business consumer. Who knows what will be the standards for WLANs of 2010? References Alexander, B., & Snow, S. (2002). Preparing for Wireless LANs: Secrets to Successful Wireless Deployment. Retrieved March 18, 2004, from Cisco Systems Inc. Web Site: http://www.cisco.com/warp/public/784/packet/apr02/p36-cover.html#title
Bing, B. (2000). High-Speed Wireless ATM and LANs. Boston: Artech.
Broadcom. (2004). Practical Strategies for Deploying Wi-Fi Clients. Retrieved February 17, 2004, from Broadcom Web Site: http://www.gobroadcom.com/wireless/?atlasnumber=ATL_66
Cisco Systems. (2002, October). Cisco Systems Aironet 1100 Series Installation and Configuration Guide. Retrieved February 15, 2004, from Cisco Systems Inc. Web Site: http://www.cisco.com/en/US/products/hw/wireless/ps4570/products_installation_and_config...
Cisco Systems. (n.d.). The Cisco Internetworking Handbook: Wireless Technologies. Retrieved January 26, 2004, from Cisco Systems Web Site: http://www.cisco.com/univercd/cc/td/doc/cisintwk/into_doc/wireless.htm#xtocid1
Cox, J. (2003, November 12). Cisco broadens WLAN offerings. Retrieved March 18, 2004, from NetworkWorldFusion Web Site: http://www.nwfusion.com/news/2003/1112ciswlan.html
Coyle, F. P. (2001). Wireless Web: A Manager's Guide. Boston: Addison-Wesley.
Engst, A., & Fleishman, G. (2003, January 23). 802.11g's "Extreme" Emergence. Retrieved March 1, 2004, from O'Reilly Wireless DevCenter Web Site: http://www.oreillynet.com/pub/a/wireless/2003/01/23/80211g.html
Fujitsu Computer Siemens. (2002). Bluetooth. Retrieved February 29, 2004, from Fujitsu Computer Siemens Web Site: http://www.fsc-pc.de/KnowHow/Start_GB_Notebook.htm?uri=/KnowHow/GB/Grundlagen/Funknetz/...
Lough, D. L., Blankenship, T. K., & Krizman, K. J. (n.d.). A Short Tutorial on Wireless LANs and IEEE 802.11. Retrieved January 26, 2004, from http://www.computer.org/students/looking/summer97/ieee802.htm
Lough, D. L., Blankenship, T. K., & Krizman, K. J. (n.d.). A Short Tutorial on Wireless LANs an IEEE 802.11. Retrieved January 26, 2004, from http://
Mallick, M. (2003). Mobile and Wireless Design Essentials. Indianapolis, Indiana: Wiley Publishing Inc.
Net World Fusion. (n.d.). Script: Wireless LAN Audio Primer. Retrieved February 17, 2004, from http://www.nwfusion.com/primers/wlan/wlanscript.html
Ohrtman, F., & Roeder, K. (2003). Wi-Fi Handbook. New York: McGraw-Hill.
Truelove, J. (2002). Build Your Own Wireless LAN. New York: McGraw-Hill.
Webopedia. (n.d.). The MAC Layer. Retrieved March 14, 2004, from http://www.webopedia.com/TERM/M/MAC_Layer.html
WiFi Consulting. (n.d.). WiFi 101: Ok, what is WiFi? Retrieved March 8, 2004, from http://www.wificonsulting.com/WiFi101/wifi101.htm
Wi-Fi Standards. (2004, February 16). Rocky Mountain News, p. B-1.
Wikipedia. (n.d.). IEEE 802.11. Retrieved February 17, 2004, from http://en.wikipedia.org/wiki/IEEE_802.11 sponsored by www.hodari.cashinginonauctions.com and http://www.e-pixelads.biz |
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