Describe how you would set up and maintain a wireless LAN alongside an existing wire-based system in a closely defined organization of your choice
'Describe how you would set up and maintain a wireless LAN alongside an existing wire-based system in a closely defined organization of your choice'
Since the invention of the computer, we have been witnessing major shifts in computing paradigms almost every decade. Today clusters of desktop workstations interconnected through high speed Local Area Networks constitute the core of network computing environments worldwide.
" Technological advances of the 90's are bringing about a major change that has the potential to reshape the existing form of network computing, with the confluence of wireless and VLSI technologies, we are poised for yet another computing revolution. ".
(Jim Grier 'Wireless lans'2001)
Figure (1.0) shows a network plan of Surrey County All Girls School. The school has 2 main teaching buildings, which are separated by a recreation building but interconnected by an Ethernet LAN.
The School Dean has decided the recreation building that has no computing facilities will be converted into a teaching facility but due to the historical nature of the building, cabling the whole building would be difficult. The floors and walls were made of very thick sandstone and historic plaster ceilings could not be easily drilled into. The only feasible solution was a wireless LAN.
Wireless LAN exist in several specifications and standards, the emphasis of this solution is using IEEE 802.11 i.e. using 2.4 Ghz operating frequency and data rates of 1Mbps and 2Mbps.It use's spread spectrum modulation. There are alternatives such as HiperLAN operating in the 5 GHz radio band and data transfer rates up to 24 Mbps. Another popular one is Bluetooth, operating over 2.4 GHz and data rates of 1Mbps.
Wireless LAN's use electromagnetic airwaves (radio in this case) to communicate network information from node to node without relying on a physical (wired) connection. The various manufacturers of wireless LAN's have a range of technologies to choose from. The common ones include narrowband (NB), spread spectrum (SS), frequency hopping spread spectrum (FHSS), direct sequence spread spectrum (DSSS) and infrared technology (IR).
The principal one used in our solution is FHSS. It takes the data signal and modulates it with a narrow band carrier wave that hops from frequency to frequency as a function of time over a band of frequencies. For example, a frequency-hopping radio will hop the carrier frequency over the 2.4 GHz and 2.483 GHz. A hopping code determines the frequencies it will transmit and in which order. To properly receive the signal, the receiver must be set to the same hopping code and "listen" to the incoming signal at the right time at the correct frequency.
The major components of a wireless LAN are a wireless network interface card (NIC) and a wireless local bridge which is often referred to as an access point. The wireless NIC interfaces the appliance with the wireless network, and the access point interfaces the appliance with the wireless network with a wired network. The wireless NIC interface appliances to the wireless network by implementing a carrier sense protocol and modulating the data signal with a spreading sequence.
The end user appliances for this solution are a range of desktop computers, laptop computers and hand held p.c.'s.
(See figure 1.3)
The solution (fig 1.2) shows how the new system will be implemented.
The main features of this wireless solution includes: using the 2.4 GHz frequency band, high performance 1.6 MB/s data rate, transmitting over secure FHSS technology, simple control and configuration of network, being ETSI accredited by Radio Communications Agency and fully IEEE 802.3 compliant and protocol independent. It is fully manageable via SNMP and via special web browser software. It is an ...
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The end user appliances for this solution are a range of desktop computers, laptop computers and hand held p.c.'s.
(See figure 1.3)
The solution (fig 1.2) shows how the new system will be implemented.
The main features of this wireless solution includes: using the 2.4 GHz frequency band, high performance 1.6 MB/s data rate, transmitting over secure FHSS technology, simple control and configuration of network, being ETSI accredited by Radio Communications Agency and fully IEEE 802.3 compliant and protocol independent. It is fully manageable via SNMP and via special web browser software. It is an Ethernet solution that has future options for IEEE 802.11 and IEEE 802.11b (yet to be licensed within UK)It even offers Cable-less mobile users or fixed users within buildings Building-to-building links with zero running costs.
The network operating system software is Window's NT, hosted on a high-end server providing the file, print and application services. The network operating system will be server orientated, that is where the core application software and databases will reside. The appliances will interface via TCP/IP with the application software/database running on the NOS. The wireless network appears to be transparent to application software and operating systems on the network. As a result, applications written for the wired Ethernet will generally run without changes over the wireless network.
In the school wireless LAN configuration, the access points connect to the wired network from the fixed location using standard cabling. It then transmits via an antenna to the antenna in building 2 connected to another access point. The access point receives buffers and transmits data between the wireless LAN and the wired network infrastructure. This single access point can support the users in that room and can function within a range of up to several hundred feet. The access point (or in this case, the antenna attached to the access point) will be mounted anywhere on the floor to provide the desired radio coverage. The end users then access the wireless LAN through wireless-LAN adapters, which are implemented as PC cards in the desktop computers, lap top computers or integrated within hand held p.c.'s.
Due to the large number of relatively large number of access points the school users will be able to move seamlessly (called roaming) on the floor. The access points 'hand' the client from one to another in a way that is invisible to the client (similar to how mobiles phones pass from one cell site to another).Extension points can also be used to further extend coverage however for this solution it was more cost effective to use extra access points.
The solution will be implemented using the Proxim RangeLAN2 product range from: Unwired Solutions.Com (UK Based Company)
Figure 1.4 and fig 1.5 shows the RangeLAN2 Network Card and Adapter, a wireless network card (NIC) is required for each client on the wireless network.
The RangeLAN2 7920 Ethernet Adaptor operates no matter what network operating system or hard platform is used (allowing for future multi-vendor upgrades) The RangeLAN2 7920 Series Ethernet Adapters support wireless connectivity to it. Internal bridging feature in the RangeLAN2 Ethernet Adapters automatically forwards packets as required with no modification to the applications.
The Specifications includes the supporting of 15 independent channels and a range of 150 metres in doors. It communicates with wired Ethernet via RangeLAN2 (as in this case) or any other open air certified access points (OPAC) or extension points (EP's)There is full support for RangeLAN2 roaming for seamless roaming, has the capacity for up to 16 domains for simultaneous independent networks (only 3 will be used though) and operates using encrypted ID. It uses the FHSS radio type technology and the Ethernet port, use's standard 10 Base-T (RJ-45 connector) conforming to standard hub conventions.
Fig 1.6,1.7 show's the RangeLAN2 Access Points that will be used to connect the wireless clients to the existing Ethernet network. RangeLAN2 7520 Access Points are full Featured Ethernet Access Points. ( includes 7015 Dipole Antenna). These will be providing Mobile Connectivity to the Ethernet. It provides standards-based connectivity from the wired Ethernet network to the wireless RangeLAN2.
The RangeLAN2 Access Points will be managed using the wired network interface. The web browser, or the SNMP interfaces which will allow the IS team to remotely monitor traffic, set configuration parameters, upgrade software. Advanced diagnostics will help isolate possible problems. SNMP traps provide notifications for fault conditions or security violations.
Figure 1.7 shows the RangeLAN2 Antenna outdoor antenna but due to the close proximity of the locations the solution will require just the indoor one. Figure 1.8 show's the LAN2 7742 Antenna Snap-on 0 dBi Stub (for indoor use in building with NIC's).However if in the future the LAN was required to be extended to other locations the external antenna could be used.
There are various advantages gained from using a wireless solution in this environment compared to more traditional media. Such as cost, if a hard-wired LAN had been introduced to the school it would have cost a lot more. The reduced cost of ownership, while the initial investment can be higher overall installation expenses and life cycle cost's can be significantly lower. Long term cost benefits are greatest in such dynamic environments requiring frequent changes especially in this school environment, where the needs of users constantly change.
The wireless network can be installed a lot faster especially in difficult to wire areas i.e. better installation speed and simplicity e.g. no need to pull cable through walls, obove floors.
Mobility is a key one, the school pupils, can access real time information anywhere in the building. This mobility supports productivity and service opportunities not possible with wired networks. Also with the inherent installation flexibility, wireless technology allows teachers and pupils to be more productive because hand held or notebook computers with wireless LAN capability deliver educational information instantly. Senior governors can make decisions more quickly because they have the information at their fingertips.
The scalability of wireless LANs is also advantageous as they can be configured in a variety of topologies to meet the needs of the school pupils and teachers. The configurations can be rapidly changed from peer to peer to large scale, full infrastructure environments. Wireless networks can benefit from increased reliability as there hard-wired counterparts inherently have more system downtime due to cable faults (cables get cut, accidental breaking of networks, corrosion due to moisture i.e. less 'wear and tear' components). This is advantageous as less cable is used, therefore reducing the downtime of the networks and the costs associated with replacing cables.
There also can be disadvantages of using wireless LAN technology such as security although the there are provisions in the IEEE 802.11 standards, encryption comes at an increased cost and decreased performance which could slow the school network should there be confidential data which needs to be protected i.e. higher level of security. Also the radio signals maybe 'eavesdropped' upon by parties not entitled to pick up signals (in this solution there will be security safeguards with encryption levels being adjusted to degree of sensitivity).
System interoperability is also an issue with wireless LAN's. Vendor-specific enhancements to 802.11-compliant products can make interoperability questionable (multivendor wireless LAN's work but features are reduced to the lowest common denominator).Although in this solution we maintain uniforminity via the RangeLan2 product range.
Other considerations include unwanted interference. Interference maybe caused by simultaneous transmissions, multi path fading or other external sources e.g. military base communications. Another limitation could be path loss between transmitters and receivers, however within this indoor solution we can expect path loss to increase 20db every hundred feet (but the planned network can easily manage applications due to the large number of access points). Another challenge could be power consumption; wireless devices are typically powered battery powered so there are inherent limitations to the usage.
Other service limitations could include problems with the TCP/IP over the wireless LAN. Issues that may affect performance such as difficulty in dealing with mobile node address's (problems occur with roaming IP address's but can be solved using Middleware although at further expense).The high overhead cause problems, TCP connection orientated protocols consume large amount of bandwidth therefore deteriorates the LAN performance. One other major issue could be the incapability to adjust under marginal conditions i.e. TCP is fairly rigid when affected by changes in wireless coverage causing the protocol to terminate the connection, thus requiring re-establishment of the connection.
So in conclusion, although flexibility and mobility make wireless LAN's both effective extensions and attractive alternative's to wired LANs the implementation of a wireless LAN is much more involved than wired networks such as Ethernet. Wireless LAN's require a more in-depth understanding of requirements, such as range and potential interference, and additional thought on the number and placement of access points.
Word Count: 1649
** All images bar figures 1.0 and 1.2 are courtesy of Wired Solutions (Web site address below)
http://www.un-wired.co.uk/acatalog/index_products_and_services.html Dates used: 02/12/01
http://www.xilinx.com/esp/home_networking/pdf_files/wireless_lans/wlan-complete.pdf : 25/11/01
www.vlana.com : 29/11/01
References
Peterson, Larry L. and Davie, Bruce S: - 'Computer networks' (2000).
Collin, Simon: -The essential LAN source book (1995).
Miller, Mark A., :-Internetworking: a guide to network communications: LAN to LAN; (1955)
Santamaría, A and Hernández, F. J.López: - Wireless LAN systems (1994).
Grier, Jim; - 'Wireless Lans' (2001)