As we peep in the history of Networking, we will find that in 1971, the researchers at the University of Hawaii developed the world’s first WLAN, or in full form the wireless local area network which was named as ALOHnet. The ALOHnet was supposed to be the bi-directional or two-way directional star topology of the system which included seven computers deployed over four islands to communicate with the central computer on the Oahu Island without using phone lines for connection or Data Transfer.
Genuinely, WLAN or wireless Local Area Network hardware was so expensive for the companies that it was only used as an alternative method to cabled LAN in places where cabling was supposed to be difficult or impossible for data transfer. The Early developments and improvements included the industry-specific solutions and proprietary protocols but at the end of the 1990s, these were replaced by standards, primarily the various versions of IEEE 802.11 (Wi-Fi) protocols.
The alternative ATM-like 5 GHz standardized technology, the HIPERLAN, has so far not succeeded in the market and that’s why had little demand for installation. But with the release of the faster 54 Mbit/s 802.11a (5 GHz) and 802.11g (2.4 GHz) standards, almost very fast and fruitful and authentic means of Wireless technology.
While in November 2006, the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO) won a legal battle in the US federal court of Texas against Buffalo Technology which established the US manufacturer had failed to pay royalties on a US WLAN patent CSIRO had filed in 1996. The CSIRO is currently engaged in the legal cases which are related to computer companies including the IT giants Microsoft, Intel, Dell, Hewlett-Packard and Net gear which argue that the patent is invalid and should negate any royalties being paid to CSIRO for WLAN-based products or applications.
Introduction
The wireless LANs or Wireless Local Area Network utilizes and uses the electromagnetic waves which are spread by spectrum technology and are based on radio waves to transfer information in form of signals between devices in a limited area and the main server.
According to kinds of WLANS they are of two types 1.infrastructure WLANs and two. Independent WLANs.The Infrastructure WLANs are used where the wireless network is linked to a wired network or with the cables, is more commonly used today.
In an infrastructure WLAN, the wireless network is usually connected to a wired network such as Ethernet, via access points, which possesses both Ethernet links and antennas to send and receive signals as well as making them powerful to transmit. These signals span microcells, or circular coverage areas (depending on walls and other physical obstructions) or buildings in the way of access points and transmitter, in which devices can communicate with the access points, and through these, with the wired network.
In a wireless LANs the devices can move within and between coverage areas without experiencing disruption or obstruction in connectivity as long as they stay within range of an access point or extension point which is similar to an access point at all times and occasions.
The wireless Local Area Network or WLAM is a network which is the linking of two or more computers without using wires or cables. WLAN utilizes spread-spectrum technology based on radio waves to enable communication between devices in a limited area, also known as the basic service set. This gives users the mobility to move around within a broad coverage area and still be connected to the network.
As regards the home user, the wireless has become most popular and economical due to ease of installation, and location freedom with the gaining popularity of laptops and PDAs. For the business, public businesses such as coffee shops or malls have begun to offer wireless access to their customers and some are even provided as a free service for the facilitation of local customers.
Large wireless network projects are also being set in many major cities for the increasing population as well as killing the cable Costs due to the huge distance from their server. In this regards, the best online advertising Companies and Search engine Google is providing a free service to Mountain View, California and has entered a bid to do the same for San Francisco also for better facilitation. The New York City has also begun a pilot program to cover all five boroughs of the city with wireless Internet access so that data can be accessed remotely by connecting them through wireless Local Area network.
Table of Contents
The other model which is connected through cables and it can be compared to those of wired LANs where devices connect via cables to hubs, or common wiring points, and from these to a central server. However, in wired networks, each hub has a finite number of jacks, and thus, can only connect a preset number of devices. Wireline networks are also confined by the existence of fixed cables, which limit connection to specified locations.
In a wired LAN, devices are connected to the network via cables. Devices are generally anchored to a set location depending on the placement of the network lines.
While WLANs provide some key
benefits, including security, mobility, and scalability, they are currently
much slower as compared to the wired LANs. For instance, a wired LAN using
10BaseT Ethernet ranges from 10 – 100 Mbps. and Other pros and cons of wireless
LANs (in comparison with wired LANs) are listed in the table below:
Wireless LAN Pros and Cons
Easier to deploy and configure
More secure
Ultimately more cost-effective (scalable)
Facilitates office relocation (network portability)
Easier to maintainMakes available real-time data in a broader range of coverage areas
Slower – Ethernet speeds ranging from 10 Mbps to 100 Mbps; corporate networks require high bandwidths
Signal interference often causes disruptions in connection
Systems from different vendors may not be interoperable
Costly installation
Source: WR Hambrecht + Co
· Access point-it is a device that connects the wireless network to the wired network. As a transceiver, it sports an antenna to send and receive signals from the various devices, providing coverage areas in which devices can roam freely.· Extension point-it is a device that acts as an access point and connects the wireless network. Unlike access points, extension points do not connect the wireless network to the wireline but rather extend coverage areas between and beyond access points.
· Infrastructure network-the more common form of a wireless LAN. Infrastructure networks are comprised of WLANs connected to wired LANs and contain access points to channel network traffic.· Independent network-a peer-to-peer network containing devices (with network adapters) connected, independent of a managing server or other form of administration.
· LAN adapter-generally a PC card in the portable device with an integrated antenna to receive signals from the access point/extension point. Can also be integrated into handhelds.
Micro cell-a coverage area in which devices can roam freely with a wireless connection. Microcells are generally circular (depending on the existence of interfering objects such as walls) and overlap to enable seamless connection as a user wanders through the wireless network. Spread spectrum-a radio frequency technology most commonly used in WLANs. Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS) are two examples of the spread-spectrum technique. Transceiver-a device, such as a LAN adapter, used to receive signals sent by the transmitter. the transmitter-a device that sends signals to the transceiver (typically an access point or an extension point in WLANs.
In recent years the popularity of wireless LANs is a testament primarily to their convenience, cost efficiency, and ease of integration with other networks and network components for the better facilitation of Clients or customers. Today, the majority of computers sold to consumers today come pre-equipped with all necessary wireless LAN technology for the safe facilitation and hassle-free uninterrupted Internet service.
Convenience: The wireless nature of such networks allows users to access network resources from nearly any convenient location within their primary networking environment (home or office). With the increasing saturation of laptop-style computers, this is particularly relevant.
With the emergence of public wireless networks, users can access the internet even outside their normal work environment. Most chain coffee shops, for example, offer their customers a wireless connection to the internet at little or no cost.
Users connected to a wireless network can maintain a nearly constant affiliation with their desired network as they move from place to place. For a business, this implies that an employee can potentially be more productive as his or her work can be accomplished.
Initial setup of an infrastructure-based wireless network requires little more than a single access point. Wired networks, on the other hand, have the additional cost and complexity of actual physical cables being run to numerous locations (which can even be impossible for hard-to-reach locations within a building).
Wireless networks can serve a suddenly-increased number of clients with the existing equipment. In a wired network, additional clients would require additional wiring.Cost: Wireless networking hardware is at worst a modest increase from wired counterparts. This potentially increased cost is almost always more than outweighed by the savings in cost and labour associated with running physical cables.
The Wireless LAN technology, while filled with the conveniences and advantages which are described above. It has its share of downfalls or demerits also. I think of nay networking solution, the wireless LANs may not be desirable for several reasons. As most of these have to do with the inherent limitations of the technology because they are sometimes dependent devices.
The Wireless LAN transceivers are designed to serve computers throughout a structure with uninterrupted service using radio frequencies. Due to this space and cost, the antennas typically present on wireless networking cards in the end computers are generally relatively poor.
To receive signals properly using such limited antennas or devices throughout even a modest area, the wireless LAN transceiver utilizes a fairly considerable amount of power. It means that not only can the wireless packets be intercepted by a nearby adversary’s poorly-equipped computer, but more importantly, a user willing to spend a small amount of money on a good quality antenna can pick up packets at a remarkable distance as the case may be.
Perhaps, the people in hundreds of times the radius as the typical user so they are also vulnerable as they are not secure data transmitters. There are even computer users dedicated to locating and sometimes even hacking into a wireless network known as war drivers which hampers all transmission.
whereas On a wired network, an adversary would first have to overcome the physical limitation of tapping into the actual wires, but this is not an issue with wireless packets. To tackle this problem, wireless networks users usually choose to utilize various encryption technologies available such as Wi-Fi_Protected_Access which is a useful tool for security purposes. Some of the older encryption methods, such as WEP are known to have weaknesses that a dedicated adversary can compromise.
As regards the typical range of a common 802.11g network with standard equipment is on the order of tens of meters. While sufficient for a typical home, it will be insufficient in a larger structure. To obtain additional range, repeaters or additional access points will have to be purchased. Costs for these items can add up quickly. Other technologies are in the development phase, however, which feature increased range, hoping to render this disadvantage irrelevant.
Like any radio frequency transmission, wireless networking signals are subject to a wide variety of interference, as well as complex propagation effects (such as multipath or especially in this case Rician fading) that are beyond the control of the network administrator. In the case of typical networks, modulation is achieved by complicated forms of phase-shift keying (PSK) or quadrature amplitude modulation (QAM), making interference and propagation effects all the more disturbing. As a result, important network resources such as servers are rarely connected wirelessly.
The speed on most wireless networks (typically 1-54 Mbps) is far slower than even the slowest common wired networks (100Mbps up to several Gbps). There are also performance issues caused by TCP and its built-in congestion avoidance. For most users, however, this observation is irrelevant since the speed bottleneck is not in the wireless routing but rather in the outside network connectivity itself.
For example, the maximum ADSL throughput (usually 8Mbps or less) offered by telecommunications companies to general-purpose customers is already far slower than the slowest wireless network to which it is typically connected. That is to say, in most environments, a wireless network running at its slowest speed is still faster than the internet connection serving it in the first place.
However, in specialized environments, the throughput of a wired network might be necessary. Newer standards such as 802.11n are addressing this limitation and will support peak throughputs in the range of 100-200 Mbps.
WLAN can be connected through a cell phone card via GSM network, satellite hardware from your satellite company, or the most common an 802.11 router and either a network card for PCI/PCI Express slot on a desktop or PCMCIA card for a laptop. Some laptops already come prepared with built-in wireless.
All components that can connect into a wireless medium in a network are referred to as stations. All stations are equipped with wireless network interface cards (NICs). Wireless stations fall into one of two categories: access points and clients.
If the functions of Wireless Local Area Network are analyzed and compared with cabled Local Area network, it will be clear that WLAN has many features and has spared the cost of wireless and other disconnection which is usually found in cabled Wireless Area Network.
But besides its numerous facilities, it has some disadvantages which need to be rectified for improving the wireless Local Area Network. Firstly the WLAN should have proper security while the transmitter and receiver receive and send their data.
Secondly, The Speed and the data sent from the main server should be strong so that it may not get slow as the distance go increasing. Thirdly the wireless data can easily be caught by the Users who use strong antennas while the remote users just have to carry on low signals and low speed. As the low signal has a low speed.
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