Wireless LAN Technologies

Wireless Communication is an application of science and technology that has come to be vital for modern existence. From the early radio and telephone to current devices such as mobile phones and laptops, accessing the global network has become the most essential and indispensable part of our lifestyle. Wireless communication is an ever-developing field, and the future holds many possibilities in this area. One expectation for the future in this field is that, the devices can be developed to support communication with higher data rates and more security. Research in this area suggests that a dominant means of supporting such communication capabilities will be through the use of Wireless LANs. As the deployment of Wireless LAN increases well around the globe, it is increasingly important for us to understand different technologies and select the most appropriate one. This paper provides a detailed study of the available wireless LAN technologies and the concerned issues. This is followed by a discussion evaluating and suggesting a feasible
standard for future.

1 Introduction: The increased demands for mobility and flexibility in our daily life are demands that lead the development from wired LANs to wireless LANs (WLANs). Today a wired LAN can offer users high bit rates to meet the requirements of bandwidth consuming services like video conferences, streaming video etc. With this in mind a user
of a WLAN will have high demands on the system and will not accept too much degradation in performance to achieve mobility and flexibility. This will in turn put high demands on the design of WLANs of the future. In this paper, we first discuss the various Wireless LAN standards available for deployment. Secondly, a study on the challenging factors of these with a little overview on security issues in wireless LAN is discussed. Finally, an analysis of the available Wireless LAN standards and a feasible solution for future deployment is discussed.

A wireless LAN is based on a cellular architecture where the system is subdivided into cells, where each cell (called Base Service Set or BSS*) is controlled by a Base station (called Access point or AP). Wireless LAN standards that are currently being explored in the field of communications technology are:
1. IEEE 802.11.
a. 802.11a
b. 802.11b
c. 802.11g
2. HiperLAN/2.
3. Bluetooth.
4. HomeRF.
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*BSS – Base Service Set; an access point is connected to a wired network and a set of wireless stations.

1.1 Wireless LAN Standards: There are several wireless LAN solutions available today, with varying levels of standardization and interoperability. Two solutions that currently lead the industry are, HomeRF and Wi-Fi* (IEEE** 802.11b). Of these two, 802.11 technologies enjoy wider industry support and are targeted to solve Enterprise, Home
and even public “hot spot” wireless LAN needs. a. IEEE 802.11: The IEEE finalized the initial standard for wireless LANs, IEEE 802.11 [1] in June 1997. This initial standard specifies a 2.4 GHz operating frequency with data rates of 1 and 2 Mbps. With this standard, one could choose to use either frequencyhopping or direct sequence (two non compatible forms of spread spectrum modulation). Because of relatively low data rates (as compared to Ethernet), products based on the
initial standard did not flourish as many had hoped. In late 1999, the IEEE published two supplements to the initial 802.11 standard: 802.11a and 802.11b (Wi-Fi*). The 802.11a [3] standard (High Speed Physical Layer in the 5 GHz Band) specifies operation in the 5 GHz band with data rates up to 54 Mb/s. The advantages of this standard (compared to 802.11b—Higher Speed Physical Layer Extension in the 2.4 GHz Band) include having much higher capacity and less RF (radio frequency) interference with other types of devices (e.g., Bluetooth), and products are just now becoming available throughout 2002. However, 802.11a isn’t compatible with 802.11b and 802.11g products. As with the initial standard, 802.11b operates in the 2.4 GHz band, but it includes 5.5 and 11 Mb/s in addition to the initial 1 and 2 Mb/s. The
802.11b standard only specifies direct sequence modulation, but it is backward compatible with the initial direct sequence wireless LANs. The IEEE 802.11b standard is what most companies choose today for deploying wireless LANs. The 802.11 working group is currently working to extend the data rates in the 2.4 GHz band to 54 Mb/s using OFDM (orthogonal frequency division multiplexing), which is the 802.11g [7] standard. This standard will hopefully be ratified by the end of 2002. Companies should be able to easily scale their existing 802.11b products to become
802.11g-compliant through firmware upgrades. This enables companies having existing 802.11b infrastructures to scale up their network via relatively simple cost-effective changes.
b. HiperLAN 1/2: European Telecommunications Standards Institute, ETSI, ratified in 1996 with High Performance Radio LAN (HiperLAN 1) [4] standard to provide highspeed communications (20Mbps) between portable devices in the 5GHz range. Similarly to IEEE802.11, HiperLAN/1 adopts carrier sense multiple access protocol to connect end
user devices together. On top of that, HiperLAN/1 supports isochronous traffic for different type of data such as video, voice, text, etc. Later, ETSI, rolled out in June 2000, a flexible Radio LAN standard called HiperLAN 2, designed to provide high speed access (up to 54 Mbps at PHY layer) to a variety of networks including 3G mobile core networks, ATM networks and IP based networks, and also for private use as a wireless LAN system. Basic applications include data, voice and video, with specific QoS***
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* Wi-Fi: Wireless Fidelity; a term usually referred to 802.11b
** IEEE – Institute of Electrical and Electronic Engineers; best known for developing standards for the computer and
electronic industry. ; ***QoS – Quality o f Service.parameters taken into account. HIPERLAN/2 [5] has a very high transmission rate up to 54 Mbps. This is achieved by making use of a modularization method called Orthogonal Frequency Digital Multiplexing (OFDM). OFDM is particularly efficient in time-dispersive environments, i.e. where the radio signals are reflected from many points, e.g. in offices.

Bluetooth: Bluetooth is an industry specification for short-range RF-based connectivity for portable personal devices with its functional specification released out in 1999 by Bluetooth Special Interest Group [6]. Bluetooth communicates on a frequency of 2.45 gigahertz, which has been set aside by international agreement for the use of industrial, scientific and medical devices (ISM). One of the ways Bluetooth devices avoid interfering with other systems is by sending out very weak signals of 1 milliwatt. The low power limits the range of a Bluetooth device to about 10 meters, cutting the chances
of interference between a computer system and a portable telephone or television. Bluetooth makes use of a technique called spread-spectrum frequency hopping. In this technique, a device will use 79 individual, randomly chosen frequencies within a designated range, changing from one to another on a regular basis. Bluetooth devices essentially come in two classes, both using point-to-point communication to speak. Class 3 devices operate at 0 dBm range and are capable of transmitting 30 feet, through walls or other objects and the other class is termed as class 1 products. These devices operate at 20 dBm, which allows for the signal to travel about 300 feet through walls or other solid objects. Both Bluetooth classes are rated at traveling at about 1 Mbps, with next generation products allowing anywhere from 2 to 12 Mbps, to be determined at a later date