A wireless LAN or wireless local area network can be considered a supple system of data communications being implemented to serve as an alternative, or as an extension to, for a “wired’ Local Area Network. Local Area Network or LAN is the relative linking of two computers or more using an OFDM modulation type technology or a spread spectrum that enables the communication between the devices on a limited range of area. This eventually provides the users with such mobility to move from one place to another within the specified range. Utilizing the applications of the RF or radio frequency technology, the wireless LANs are capable of transmitting and receiving data through air, thus lessening the eventual requirements for a physical connection in the form of cables and wires. Therefore, the wireless LAN technology combines user mobility and flexible data and information connectivity (Proxim 1998, p.24).
The technology brought about by the wireless LANs have consequently gained an intense reputation in various forms of vertical markets such as retail, commercial, academe, health-care, warehousing, and manufacturing sectors. These segments of the industrial sector have efficiently gained performance as well as employee productivity on using laptop or notebook computers or hand-held devices to transmit data and information in a real-time basis within a centralized host computer for processing. At present, wireless LAN technology are continuously becoming broadly accepted and recognized as a general-purpose solution in terms of alternatives in connectivity intended for a broad range of personal and especially business customers.
The eventual invention of the wireless LAN began in 1970 when Norman Abramson of the University of Hawaii had developed the first communication computer network using a minimum-cost ham-structured radio termed the ALOHAnet. This computer network, a two-directional system with a star topology, included almost seven computers, which were deployed on four islands. These computers in return will be subjected to communications with a main central computer located on the Oahu Island without utilizing physical connections or telephone lines.
The first experimental procedure using the principles of wireless LAN using a diffused type infrared system was published in the IEEE report in 1979 by U. Bapst and F.R. Gfeller. It was then followed in 1980 by an experimental report using the spread spectrum on a single code for terminal wireless communications by P. Ferrert. And in 1984, a comparative analysis was conducted between the CDMA spread-spectrum and the infrared was presented by Kaveh Pahlavan in the IEEE Computer and Networking Conference and soon was published on the magazine of IEEE Communication Society.
During the early 1980’s several proletarian radio operators (commonly termed packet radio) were able to develop the first group of data modems. The enhancement was the addition of a voice data communication band with a rate-data of below 9,600 bits per second to an active and existing radio structure over a short range. The second group of wireless bound modems was created and developed right after the announcement of the Federal Communications Commission (FCC) on the subsequent experiments using the spread spectrum bands intended for non- commissioned military usage. This second generation of modems produced data rates on the range of hundreds of kilobits per second. Afterwards, the third generation was created with the objective of utilizing compatibility on other existing local area networks in the range of Megabits per second (Hopkins 2007, p. 23).
In 1991, the IEEE conducted the first wireless local area network workshops. This led to the relative conglomeration of the various LAN merchandises on the platform of the IEEE 802.11 standards. The workshop focused on the evaluation of the alternative and available technologies. In 1996, the technology had tremendously matured and various applications were clearly defined and understood. The chip sets necessary for the implementations and specific applications of wireless local area network. Were also determined and proved to be the critical part to achieve fast growth in the market shares. This resulted in the utilization of wireless local area network by the different institutions such as hospitals, academes, offices, and the like, upon which several networking principles were applied (ad-hoc networking, point-to-point local area networking, and nomadic access). Rapid development and progress were achieved by the IEEE 802.11 standards wherein alternatives and variants were eminent (the wireless local area network operability, the SUPERnet, HiperLAN specifications, and the like).
Initially, the hardware of the wireless LAN proved to be expensive and the use of which served only as an alternative to the wired –LAN where it was impossible or difficult to install. The early development of the technology were intended solely on industry-identified needs and solutions, But in the late 1990’s, the early technologies of wireless LAN were replaced eventually by standard technology which were mostly different versions of the original IEEE 802.11 (WiFi TM). Several alternatives include the HiperLAN/2, the 802.11g standard, and the 54 Megabit per second 802.11a (Jackson 2001, p110).
The architecture of the wireless LAN technology has several definitive terms such as the Station, the Basic Service Set, the Extended Service Set, and the Distribution System.
All of the components that literally connect unto the medium of wireless communications within the network are referred to as the station. These stations are equipped with a card known as the WNICs or the wireless network interface card. The stations are also categorized into two categories: the clients and the access points. The clients are the devices capable of conducting wireless communications such as pda’s or personal digital assistance units, laptops, internet-phones, and desktops or workstations with a network interface which is wireless. The access point is normally classified to as routers, and usually consists of a base station that receives and transmits RF (radio frequencies) for wireless-capable clients to communicate from one another.
Basic Service Set
The BSS or the Basic Service Set comprised of all stations that are capable of communicating from one another. The two types of BSS are the infrastructure and the independent: the infrastructure BSS are capable of communicating with the other stations through utilizing the access points even with different basic service set; the independent BSS is considered an ad-hoc network wherein there is no relative access point, thus it can connect to other BSS. An access point is the “physical” address of the network wherein every BSS has an identification address.
Extended Service Set
The Extended Service Set comprised of the set of interconnections of numerous BSS. The access points are eventually connected on a distribution system upon which ESS identification is assigned (usually string of 32 byte character).
The distribution system interconnects the access points in the ESS. The principle of the distribution system is to augment the network exposure through the use of roaming capabilities among the cells.
Wireless LAN Technology
Different manufacturers of wireless local area networks offer a wide variety of technologies to opt from when developing and designing wireless solutions on a specific application. Limitations, advantages, and disadvantages are eminent and unique for every set of wireless technology designs. These technologies involved narrowband, spread spectrum, Frequency-Hopping Spread Spectrum, Direct Sequence Spread Spectrum, and Infrared Technology.
The narrowband radio classification receives and transmits user data and information on a specified RF or radio frequency. The system keeps the apparent radio frequency or signal as slender as possible in order to surpass the data or information. Crosstalk between two channels of communications can be avoided by allotting different and specific frequencies; this also served in preserving level of confidentiality or privacy over the communication channel. Technically, this can be achieved as the radio receiver eventually filters out all of the radio signals with the exception on the designated or allocated frequency. Eventually, a narrowband type of communication requires an FCC license obtained by the end-user on the pre-determined area.
Most of the wireless local area network -systems utilizes the technology of spread-spectrum, in which it consists of a broadband radio frequency method being developed by the armed forces (military) to have secure, reliable, and critical-mission system of communications. This technology is intended to trade off efficiency of the bandwidth in terms of reliability, efficiency, security, and integrity. Therefore, much bandwidth is being consumed as compared to the transmission using narrowband technology. But the effect of utilizing such broadband provides a louder signal that can easily be detected by the receiver. Consequently, if a receiver has not been oriented unto the correct frequency, a spread-spectrum will manifest a signal on the background and could be identified as a noise. The two types of spread spectrum are the following:
Frequency-Hopping Spread Spectrum
Frequency-hopping spread-spectrum or the FHSS utilizes a carrier, which is narrowband that eventually alternates or changes the frequency in a form of a definite pattern known to both receiver and transmitter. When correctly synchronized, the resulting effect is a logical single channel, otherwise will appear like an impulse noise having short durations.
Direct-Sequence Spread Spectrum
The Direct-sequence spread-spectrum or DSSS is capable of generating a superfluous pattern for each transmitted bit. This pattern of bit is called the chipping code or the chip. The longer is the chip, the superior will the possibility that the original information or data can be recovered. This is in turn directly proportional to the required bandwidth. Furthermore, the statistical method or technique entrenched on the radio frequency can be manipulated to regain the original data or information without resending. The signal appeared as noise for an unintended receiver and is usually being ignored or rejected of most narrowband receivers (Kopytoff 2005, p. A-1).
The infrared or the IR technology is the third manifestation of wireless LAN aside from the narrowband and spread-spectrum technology. It is considered seldom used in the commercial aspect of wireless local area network businesses. The infrared utilizes a very high frequency, which is relatively below the electromagnetic spectrum of visible light, to transmit data.
Just like a light, the Infrared is not capable of passing trough objects that are opaque; either diffuse or a line-of-sight (directed) technology; have a minimal cost for a system that provides a range of around 3 ft.; specifically applied on personal remote networks but seldom employed on specific wireless local area network solutions.
Wireless LAN Configuration
How Wireless LAN Works
Wireless Local Area Network uses the electromagnetic signal or airwaves (infrared or radio) to be able to transfer data or information (communicate) from one area to another without the existence of a physical connection, such a wires or cables. A transmitter superimposes the data on a carrier wave, in this case the radio waves served as the carrier waves. The process of superimposing the data unto the carrier waves is called modulation. The radio waves, therefore occupies more than one frequency since the bit rate of the modulated information combines with the carrier. Usually, several carrier waves can exist at the same time
and on the on area or space without the consequent of interference since the radio waves can be allocated with different frequencies. To be able to extract the information or data, a receiver on the other end is used and set to the pre-determined frequency, rejecting all other frequencies present (Ingersoll 2005, p.11).
A transceiver (transmitter-receiver) system is used in a typical wireless local area network setting. This transceiver is categorized as the access point and it connects to all other network from a fixed spot implementing standard cabling structures. On a minimum standpoint, an access point eventually receives, then buffers, and finally transmits the information or data obtained between the wired and the wireless network.
A solitary access point can have considerable support on a minimal group of end- users and can relatively function within the specified range of slightly several hundred feet. The antenna, which is being attached unto the access point, is mounted relatively high to avoid the blockade of the line-of-sight; but nonetheless can be mounted at any height as long as the required radio frequency coverage is attained. The end-users utilizes the wireless LAN through a network adapter card that served as the hardware interface between the computer’s (laptop, desktop, notebook, personal data assistant devices, etc.) operating system and the radio frequency through an antenna attached or imbedded on the adapter card.
Configurations on the wireless local area network can be very simple to a more complex arrangement. Typical network configurations depend on the subsequent applications and can be categorized as such of the following:
Wireless Peer-to-Peer Network
This configuration can be considered the simplest wherein two computers with a wireless adapter card can set-up their own independent network provided it is within the specified range.
Clients and Access Points
This network configuration refers to the interconnection of several clients to an access point connected to a wired network. Creating an access point usually extends the range of transmission wherein the devices can consequently communicate. Therefore, each client would eventually have access to all other server networks depending on the specified capacity of the access point (maximum required volume of data, range of transmission, etc.).
Multiple Access Points and Roaming
An access point has a range of around 500 ft. (indoor) and almost 1000ft (outdoor). If the application is on a larger scale, for instance a university or a manufacturing site, the solution can be obtained by installing several or multiple access points within the wide area. The location of such access points will depend on the topographical and structural conditions of the area. The idea is to have multiple overlapping access points so that the end-user may move from area to another without loosing connections. This concept of blanketing a wide area so that the end-user may move freely among the group of overlapping access points is called roaming (Pommer 2008, p.236).
Sometimes, the topology of an area affects the establishment of access points. Therefore an extension point is installed to extend the range of the signal so that it could reach an access point. An extension point works and looks like an access point but they are not attached to the wired network. The extension point only served as a “bridge” to other access point or extension points.
The Directional Antenna
Directly antenna configuration can be described as having two antennas, relatively communicating from each other on one point to another on a considerable distance. One antenna
is hooked up to the wired network though an access point wherein the data or information is transmitted to the other antenna. The other antenna then served as the access point on a wireless local area network within that vicinity.
Advantages, Disadvantages and Applications
Advantages of the wireless local area network can be made on the basis of a relative comparison against the wired network. The advantages of such over the latter are the following:
Mobility provides the end-user a real time access of data or information from anywhere within the specified range, thus improving productivity and performance. This mobility cannot be obtained through wired network.
The installation is fast, flexible, and simple as compared with that of the installation requirements of a wired network.
The relative costs are low with respect to the life-cycle cost, installation expenses, and maintenance, though the initial cost of the hardware maybe higher as compared to the wired network (Steven 2008, p. 12).
The scalability is more eminent compared to wired network since the wireless LAN can be configured in several variations of topologies to meet the required solutions.
Network configurations can easily be adjusted and change.
The disadvantages of the wireless LAN over the wired network should also be considered. The following are:
· The security of eventually intercepting the signal transmitted in a wireless environment is evident since the data only travels through the carrier radio waves, once intercepted by a powerful receiver can be fatal. Though there has been several security measures such as the WiFiTM Protected Access or the WPA, wireless network cracking can always be performed without the knowledge of the end-user. The hacked network is susceptible on data access even on remote pc or laptops. As compared with the wire-network, the hacker should pass the limitation of a physical connection as compared to the wireless LAN (Mitchell 2006, p.10).
· The range is also of great concerns since if the solution requires a wide area, the utilization of the wireless technology will be costly since extension points and access points devices should be purchase to increase the range.
· Reliability is also of great concern in a wireless LAN set-up since there is a possibility of several interferences and composite propagations that may affect the strength of the signal.
· The speed of the wireless LAN is usually from 1 up to 108 Mega Bit per second is relatively slower compared to the slowest possible speed of a wired-network (100 Mega Bit up to several Giga Bits).
The applications of wireless local area network communications usually augment that of the wired network rather than replace. The flexibility and the communication power of wireless LAN can be seen on these various manifestations such as the following: Students can have easy access on on-line libraries and references through wireless LANs on their laptops and handheld devices; nurses and doctors can easily give patient information through wireless connectivity; a fast network set-up can help employees access their files and relative data, transfer information, communicate real-time improving work performance, and efficiency; field managers can reduce the cost of transportation or gasoline expenses through mobile and wireless teleconferencing, and electronic mails; exhibits and trade shows can minimize the cost of setting up if a wireless LAN is available within the vicinity; warehouse workers can easily check the inventory and other related logistics concerns also in a real-time and flexible manner; managers can have the flexibility on conducting long distance meetings, and consultations through the use of the wireless local area network.
Customer Considerations and Summary
While the technology of wireless LAN provide much of the desired power, flexibility, and economics, several key factors should be given attention when considering a wireless network configuration. These are the coverage and range that has a certain limitations considering the wireless local area networks (blockades and topologies); the relative throughput in which the factors to be considered are the propagation, the number of users, types of wireless LAN structure, bottlenecks and latency; reliability and integrity, compatibility in terms of the existing network, the operational capabilities of the wireless devices being used, coexistence and its relative interference, licensing, and ease of usage, and simplicity. It is therefore imperative that these factors should be given the outmost concerns when planning to set-up or established a wireless local area network.
The wireless LAN offers a wide variety of opportunities and practical applications for the end-users. The use of radio frequency technology and infrared indeed provided the way for a wireless connectivity. The advantages of wireless LAN over a wired-network are eminent: flexibility, mobility, low maintenance cost, fast and flexible installation and the network configurations can be adjusted quickly. The disadvantages are also significant. Therefore it is imperative that the pros should be weighed against the cons in terms of the efficient solutions to the customer’s or to the end-user’s needs. One should not compromise the other and all of which will depend on the proper design of a wireless local area network on a specified needs and applications. Furthermore, the reliability, security, speed, connectivity, and simplicity should not be compromised with flexibility, availability, and costs; and vice versa.