WIRELESS LAN
Introduction
This paper is about the emerging technology of Wireless LANs that are being used in many businesses today. A historical overview will start the discussion as it moves on to the discussion of its application and technology. Wireless LANs will be defined and describes in details in the following sections.
Historical Overview
They say that back in 1971, at the University of Hawaii, researchers developed ALOHA net, the world’s first ever wireless local area network. The system was a bi-directional star topology that included seven computers. These computers were deployed over four islands. The central computer was deployed at Oahu island without using any phone lines.
Back then, wireless LAN hardware were so expensive. Due to this, WAN was only used as an alternative for cabled LAN. Ultimately, it was used for places that were only difficult or impossible for cabling.
Moreover, according to Wikipedia, “early development included industry-specific solutions and propriety protocols.” But as the end of 1990s neared, these solutions and protocols were replaced by standards, mainly the various versions of IEEE 8012.11 (Wife). There has been an alternative developed like the ATM-like 5 GHz standardized technology, HYPERLINK. But so far, it has not succeeded in the market. Apparently, it never will with the release of the faster 54 Ambit/s 802.111 (5 GHz) and 802.11g (2.4GHz) standards.
As of last year, The Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO) have been in battle with other software and hardware giants for royalties on the patents that are allegedly held by CSIRO regarding these technologies. CSIRO claims to have been the first to develop wireless networking.
Application/Technology
Wireless networks include several technologies, each with its own optimal use. Wireless LAN technology, mainly the 802.11 set of standards, helps create wireless networks similar to organization-wired Ethernet networks.
Wireless LANs also can provide a cost benefit. Installing and configuring wired communications can be costly, especially in those hard-to-reach areas. Ladders, drop ceilings, heavy furniture, kneepads, and a lot of time are often necessary to get all components installed and connected properly. By comparison, wireless LAN installations are a breeze. Plug in the access point, install a wireless network interface card (NIC), and you are all set.
An access point is the device that acts as a gateway for wireless devices (Andres, 2003). Through this gateway, wireless devices access the network, as shown in Figure 1.
Stations – are referred to as all components that can connect into wireless medium in a network. All stations have wireless network interface cards (WINCES). Wireless stations fall into one of two categories: access points and clients.
Clients – can be mobile devices such as personal digital assistants (Pads), laptops, fixed devices such as desktops and workstations, or IP phones. All which are equipped with Winces.
Basic service set – or BSS is a set of all stations who communicate with each other. Two types of BSS are: infrastructure BSS and independent BSS. BSS has an identification called the BID. The BID is the MAC address of the access point in service of BSS.
Extended service set – or LESS is a set of all connected Basses. LESS also has an identification called the SAID. The SAID is a 32-byte (maximum) character string. All access points in an LESS are connected by a distribution system.
Distribution system – as mentioned above, the distribution system connects all access points in an LESS. Usually, a distribution system is a wired LAN but can also be a wireless LAN.
What Is It, Including Technology Overview
A wireless local area network (WAN) is said to be a set of network components. These network components are connected by electromagnetic (radio) waves instead of the more commonly used wires. Weans are used as a substitute for wired computer networks. It adds freedom of movement and flexibility within the workplace. Oftentimes, it is also used in combination with wired computer networks. Clients who use Weans enjoy the easy access on their respective company networks and even the Internet from almost anywhere within and throughout the boardroom, campus or store. They do this without relying on any wired cables and connections available.
There are two modes that the proposed standard 802.11 works on: (1) in the absence of base station and, (2) in the presence of base station. In the first case, computers that communicate with each other through this mode is called ad hoc networking. The latter case on the other hand is called the infrastructure mode. All communication goes through the base station, which is the access point in 802.11 terminologies.
IEEE (working committee) 802.11 indicates set of wireless WAN/LAN standards. Some challenges that they met as they developed these standards were: “dealing with the fact that radio signals have a finite range; building a system with enough bandwidth to be economically feasible; ensuring users privacy and security; finding a suitable frequency band that was available, preferably worldwide; and finally, worrying about human safety.”
During the standardization process, 802.11 was decided to be made compatible with Ethernet above data link layer. Inherent differences existed eventually which had to be taken care of by the standard.
Foremost, before transmitting, a computer on Ethernet always listens to the ether. This is not possible in case of Weans. Collision may take place as the range of a station may not be able to detect transmission that is taking place between two other stations.
Another problem that were to be solved was the interference resulting in what we call Multipart fading. This was a result of radio signals being received a multiple times because they can be reflected off solid objects.
The last dilemma was is a notebook computer were to be moved away from the base station to another, a way of handing it off must be done.
Eventually, the committee came up with a standard to finally address these concerns. The amendment 802.11i also enhanced the security. Among the most popular of amendments are 802.11a, 802.11b and 802.11g to original standard. Service enhancements and extensions are in other specifications from (c-f, h, j).
Who Does/Might Use It
Basically almost every establishment and organization that is spread over an area uses WAN. WAN however are more for the persons on the go.
Outline of Development/Uptake Challenges
Before we move on, let us discuss the standards that are the basis for communication. In June 1997, the IEEE (Institute of Electrical and Electronics Engineers) finalized IEEE 802.11, the initial standard for wireless LANs. This standard specifies a 2.4GHz operating frequency with data rates of 1Mbps to 2Mbps and the capability to choose between using frequency hopping or using direct sequence, two incompatible forms of spread-spectrum modulation. In late 1999, the IEEE published two supplements to the initial 802.11 standard: 802.11a and 802.11b.
Like the initial standard, 802.11b operates in the 2.4GHz band, but data rates can be as high as 11Mbps, and only direct-sequence modulation is specified. The 802.1 la standard specifies operation in the 5GHz band using orthogonal frequency division multiplexing (FORM) with data rates up to 54Mbps. The advantages of this standard include higher capacity and less radio frequency (R.F) interference than with other types of devices.
802.1 la and 802.11b operate in different frequencies, so they are not interoperable. They can coexist on one network, though, because no signal overlap exists. Some vendors provide a dual-radio system with 802.11a and 802.11b.
The latest wireless standard is 802.11g, and (like 802.1 la) it provides data rates of 54Mbps, but (like 802.11b) it operates in the 2.4GHz range. The 802.11g standard is also backward compatible with 802.11b networks, providing a more cost-effective upgrade and rollout plan for organizations.
To complicate issues, Europe has developed the Hyperlink/2 standard, led by the European Telecommunications Standards Institute (ESTE). Hyperlink/2 and 802.1 la share some similarities: both use FORM technology to achieve their data rates in the 5GHz range, but they are not interoperable.
Anyway, before the discussion goes further, the approval of the initial IEEE 802.11 standard back in 1997 spurred rapid growth in Weans beyond the traditional, low-bandwidth vertical applications and into mission-critical general-office applications. In September 1999, however, 11-Mbps 802.11b standard was approved and the horizontal WAN market achieved some impression of legitimacy, followed by rapid acceleration.
Analysts have long anticipated the fever that surrounded WAN. Yet with the success, according to Mathias (2003), Weans are still not immune to the rip currents that pervade essentially ever high-technology market. He states the following observations:
(a) There is a constant demand in price and performance. (b) There is a need to deal with rapid technological change and continuing 802.11 evolutions. (c) Security. And, (d) there is a requirement to lower operational and other recurring expenses.
It comes as no surprise, then, that wireless-LAN vendors have been sparing little effort in building additional tools and now entirely new architectures to address the above needs. The primary goals today are to improve manageability, security and the costs of both equipment and operations. In short, what we are seeing is the result of a very natural evolutionary process, which is endemic to high technology.
Current Technical/Business Status (where relevant)
Wexler (2006) observed that the subject of 802.11 has ignited controversy during the past year ranging from whether municipalities that deploy mesh networks have an unfair advantage over competing service providers, to whether strangers who piggyback on unsecured home networks are abetting terrorists.
However, although Wife has been phenomenal, market analysts sense a proverbial lull before the storm. Wexler states the following reasons:
(a) The lion’s share of the current installed Wife base comprises Cisco Systems’ older AirNet equipment. This gear consists of individually managed, intelligent access points (Apes) that are also called “thick” or “traditional” Apes. Many of the customers operating these systems are just beginning to learn about the newer, centrally managed (“thin” or “dependent”) Apes, and the accompanying switched Wife architecture. (b) Many mainstream enterprises are waiting for dual-mode handsets that support both Wife and cellular voice calls before they make commitments to deploying voice over IP (VOID) over Wife networks. And, (c) Established enterprise WAN deployments are still catching up to Wife technology advances, particularly in the area of security.
Wexler explains that despite the continuous progress with standards development and product features, particularly in the area of intrusion detection and prevention, that the Wife industry makes, enterprises can only move so fast. She says that the verticals in which wireless and mobility have always been a must are keeping up with trends like voice over Wife, yet they struggle with the latest iterations of security, which are most difficult to deploy on small handheld clients, because 802.11i supplicants simply aren’t available for them yet.
She explains further that the direction of Wife provisioning, administration and R.F management is toward centralization, but it will take awhile until the masses that now use Cisco traditional distributed Apes move onto the bandwagon. And until converged devices supporting both Wife and cellular voice capabilities are widely available, mainstream enterprises seem to be postponing large commitments to voice over Wife.
Furthermore, the enterprise WAN, in general, is in a bit of a holding pattern until full 802.11e QUEST-enabled implementations are Wi-Fi-certified and available, dual-mode phones hit the market, interoperability and deployment issues associated with 802.11i security components get cleared up, and it becomes apparent whether 802.11a is ever going to be a real network player, or will be leapfrogged by 802.11n.
Technical Details In Depth Explaining Total Value Chain
Benefits of wireless LANs include:
Convenience
The wireless nature of such networks allows users to access network resources from nearly any convenient location within their primary networking environment (a home or office). With the increasing saturation of laptop-style computers, this is particularly relevant.
Mobility
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.
Productivity
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 from any convenient location.
Deployment
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).
Expandability
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 labor associated to running physical cables.
Source: http://en.wikipedia.org/wiki/Wireless LAN#Historie
Disadvantages on the other hand include:
Security
Wireless LAN transceivers are designed to serve computers throughout a structure with uninterrupted service using radio frequencies. Furthermore, because of space and cost, the “antennas” typically present on wireless networking cards in the end computers are generally nothing more than the most naive of reception devices. In order to properly receive signals using such limited antennas throughout even a modest area, the wireless LAN transceiver utilizes a fairly considerable amount of power. What this means is 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; perhaps hundreds of times the radius as the typical user. There are even computer users dedicated to locating and sometimes even hacking into wireless networks, known as war drivers. On a wired network, any 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 combat this consideration, wireless networks may choose to utilize some of the various encryption technologies available. Some of the more commonly utilized encryption methods, however, are known to have weaknesses that a dedicated adversary can compromise.
Range
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.
Reliability
Like any radio frequency transmission, wireless networking signals are subject to a wide variety of interference, as well as complex propagation effects (such as multipart, or especially in this case Rican 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 (PS) or quadrate amplitude modulation (AM), making interference and propagation effects all the more disturbing. As a result, important network resources such as servers are rarely connected wirelessly.
Speed
The speed on most wireless networks (typically 1-54 Mbps) is far slower than even the slowest common wired networks (100Mbps up to several Gaps). 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.
Source: http://en.wikipedia.org/wiki/Wireless LAN#Historie
Any Other Relevant Topics
Morozoff (2004) seems to agree that Weans still needs improvement. She states that:
“WLAN adopters are clearly committed to the technology, as evidenced by their plans to deploy to more end users and to add functionality. But what about the suppliers? Will the areas that need improvement be addressed?
There is plenty of reason to conclude that the answer is yes. Products from wireless specialist companies like Reef edge and Trapeze Networks are aimed at helping enterprises design and manage increasingly complex WAN deployments, while industry leaders like Cisco and 3Com continue to introduce enhancements to their products. Since so many industry players see wireless as one of the few shining spots in the industry, you can be certain that R & D investments will continue.”
Credit:ivythesis.typepad.com
0 comments:
Post a Comment