Wi-Fi Technology

CURRENT WIRELESS TECHNOLOGY

In the smallest range, we have a Bluetooth [2] example. It is a wireless network technology that has its own development direction other than the 802.11 family. Bluetooth supports a very short range in the region of 10 meters and relatively low bandwidth roughly around 1-3 Mbps. It is designed for low-power network devices like portable or handheld gadgets. Nowadays it is a normal feature for handheld devices which include notebook to have a built-in Bluetooth support.

In the medium range, the popularity of the wireless Fidelity (Wi-Fi) has developed the market for unregulated band or unlicensed client-access radios in a wide variety of applications. This technology is one of the last-mile wireless broadband and narrowband services. However, the current main type of the last-mile deployment is the large-area coverage normally called hot-spots. Wireless last-mile coverage is based on IEEE 802.11 standard [1] which uses the high-gain antennas, while hot spots use the modified version of the IEEE 802.11 apparatus which is called a mesh operation. Wi-Fi resembles the wireless local area network.

In 2005, for a wider range, the Worldwide Interoperability for Microwave Access (WiMAX) certified the IEEE 802.16-2004 standard [3] for fixed-position radios. WiMAX will provide the point-to-multi-point and point-to-point wireless broadband devices in both the regulated and unregulated bands. Then, the IEEE 802.16e standard [4] for portable devices has been approved in 2006, regulating the client radio frequencies in licensed and unlicensed bands. This promising technology will provide service providers an additional layer of services benefits.

WiMAX actually resembles a wireless metropolitan-area network segment which provides broadband wireless connectivity to portable, fixed and roaming users. Its designed target is for long-range networking as opposed to local area wireless networking and the research in this field still continues. It is developed independently from Wi-Fi, providing additional distance up to 50 kilometers with total data rates can be up to 75 Mbps, providing sufficient bandwidth to support hundreds concurrent users using a single radio base station. WiMAX has been said to provide many wireless access advantageous to the remote and isolated area.

WIRELESS DEPLOYMENTS

The current trends show that the price of the wireless gadgets keep decreasing with the every advent of new technologies. The affordability makes wireless as a popular and practical alternative. Wireless deployment can be as simple as connecting two adjacent computers wirelessly. More complicated deployment will have hundreds or thousands of devices with centralized servers and distributed APs. Basically, wireless network can be structured into two different modes, based on the coverage size needed. These two modes are

1. Ad-hoc mode: This mode is a temporary, as is basis type. There is no AP in this mode and the devices are directly sharing their resources when in the range. The shared resources available as long as the devices are running. Bluetooth is one of the examples.

2. Infrastructure: This mode resembles the wired network. In this mode the AP is used for the wireless devices to communicate each other and it is dominant mode that can be found in residential, corporate building, university campus and plants. The wireless devices can keep connecting as long as they are directly connected to and within the wireless network coverage. Wireless security elements could be enforced on all the wireless devices and users such as through policies, authentication, encryption and many more.

Currently the wireless deployment still dominated in the last mile coverage. This is because of the unregulated frequency availability which lowered the cost of deployment and maintenance. Furthermore, the mass introduction of the cheaper consumer wireless devices makes it an attractive offer. Other than providing an alternative mode of communication medium, the main reason of the adoption is based on the mobility nature of the devices. However, in term of deployments, we can categorize them into four main segments of utilization as listed below.

1. The Wireless Personal area networks (WPAN – 802.16).

2. The Wireless Local area networks (WLAN).

3. The Wireless Metropolitan area networks (WMAN).

4. The Wireless Wide area networks (WWAN).

WIRELESS PERSONAL AREA NETWORK

WPAN can cover a range up to 30 feet or around 10m. Although this seems absurdly small, but this range allows wireless devices to be connected wirelessly to other nearby wireless devices [6]. WPAN provides a very short distant and for small group or community that can share resources wirelessly. Bluetooth which based on the IEEE 802.15.1 standard [7] for example, is mostly used for short range computing and communication peripherals, such as a PDA to a computer or a hand phones. It is normal that the new Bluetooth version can provide data rate performance up to 1Mbps. Another example is the ultra-wide band (UWB) which is designed for multimedia services transmission. The related standard for UWB is IEEE 802.15.3 which can support a data rate up to 400Mbps which equivalent to the DVD video quality standard. In this case the WPAN becomes a high-speed personnel area network. Other usage includes the ad-hoc network where a local area network in which computers and network devices are in close proximity to others in similar subnet. These devices are connected temporarily and as is basis. The receiver and transmitter used are built-in type devices.

However there is no independent pre-existing network for WPAN. All the devices in WPAN communicate based on the ad-hoc network, can be connected when within the range and disconnected when out of range. Better built-in devices can be designed in the future to provide non ad-hoc network. Other similar scenario can be found when using the Infrared (IR) to exchange data between laptops. The nature of wireless devices discovering each other and in many situation it is automatic, is a very big issue in wireless security field.

2.2.2 WIRELESS LOCAL AREA NETWORK

Similar to its counterpart, LAN in fixed line, WLANs can provide coverage larger than WPAN but still limited. Typical coverage areas can be found in a campus, a corporate building, a hospital, or a manufacturing plant [8]. Take note that, the traditional wired LAN can be expanded using wireless through the wireless Access Points (APs) for example, creating a heterogeneous network. The standards-based WLAN typically serve more users and applications compared to WPAN and can serve a distance up to 10 meters or more although this depend on the physical environment such as walls and frequency reflectors. The legacy and new wireless standards that have been released associated with WLAN are included the following three major revisions.

1. 802.11n - bandwidth speeds up to 600 Mbps (2009).

2. 802.11g - bandwidth speeds up to 54 Mbps.

3. 802.11b - bandwidth speeds up to 11 Mbps.

4. 802.11a - bandwidth speeds up to 54 Mbps.

On the service provider part which normally called Wireless Internet Service Providers (WISPs) usually use the existing Wi-Fi mesh topologies or the directional antennas for better signal and larger coverage. For example those deployments can increase the performance beyond the 54Mbps with 10 kilometers in range while still obeying the 802.11 standard. The increased range creates the WLAN and WMAN segments as shown in Figure 1. However there are many more variables such as the APs to user’s distance, the number of users and topologies which actually define the WLAN and WWAN.

Figure 1: Wireless technologies target segments

METROPOLITAN AREA NETWORK AND WIRELESS WIDE AREA NETWORK

The WMAN is the third usage segment shown in Figure 2. The WLANs collection makes the WMAN and the range can be up to 50 km. The implementation examples in this segment include the WiMAX, DSL/ADSL and DOCSIS legacy coppered wired technologies.

Figure 2: Wireless networks categories

The fourth usage segment shown in Figure 2 is the WWAN. WWAN aggregates WMANs and the range can cover the area up to 50 km. Compared to the previous wireless technology, this is a large area coverage which makes the backhaul or core network possible. In order to cater for the big amount of traffic, WWAN still utilizes various type of existing technology such as fiber optic links and terrestrial microwaves as a complement which normally acts as the backhaul for inter-WWAN connections. Depending on the type of traffic (data, voice or video), the performance can goes up to 10Gbps.

There must be very compelling reasons for deploying wireless communication in all the segment usage because the traditional wired communication already existed long time ago. In the WPAN and WLAN, the main reason of deployment is the mobility while in the WMAN and WWAN it is more on the cost per user, for example, deployment in remote area with less user population. In this case there should be no landline and Radio Base Station (RBS). However the real requirements for each segment are based on a variety of variables as listed below:

1. The distance and power of the signal.

2. The topology including the user location.

3. The bandwidth needs.

4. The services offered.

5. The security features.

Figure 1 also shows the wireless standards, standards bodies and their features such as distance and bandwidth which mapped to the four usage segments previously explained. Regarding the standard, there are three main bodies involved in wireless technology as listed below:

1. European Telecommunications Standards Institute (ETSI) [9]

2. Institute of Electrical and Electronics Engineers (IEEE) [10]

3. Third-Generation Partnership Project (3GPP) [11]

The IEEE and ETSI standards are interoperable and concentrate mainly on wireless packet-based networking. However, ESTI is concentrated more on the technology and standard for the European countries. The 3GPP standard focuses on cellular and third-generation mobile systems and very apparent in the mobile sectors.