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This chapter has five sections that review on the literature of the topic that carried out by the research. Section 2.2 discusses about the type of wireless network which are available nowadays and their standards. Section 2.3 explains the function of the most popular wireless network which is Wireless LANs and some types of wireless LANs. Section 2.4 shows different type of protocol of IEEE 802.11 standards. Section 2.5 discusses about the relationship between WLANs and Wi-Fi.
2.2 Types of Wireless Networks
Although we use the term wireless network loosely, there are in fact five different types of network.
Mobile devices network
Both of them have a part to play in developing wireless solutions in various combinations. Each type of wireless network operates on a specific set of radio frequency.
Wireless Local Area Networks (WLANs)
The network operates by linking two or more computer using radio frequency energy, and providing a connection through an access point at a small area such as home or office. WLAN is carrying out by a set of standards under the title of IEEE 802.11 that define the structure of the relative short-range signals that provide Wireless Fidelity (Wi-Fi) service.
Wireless Personal Area Networks (WPANs)
It is a personal area network that interconnecting devices centered on a workspace which the connection are wireless. It can operate in a very short range. A new standard, IEEE 802.15 was used in WPANs. The most talked about technology is called Bluetooth.
Wireless Metropolitan Area Network (WMANs)
Several Wireless LANs can be connected by this type of wireless network. It operates on IEEE 802.16 standard. World Interoperability for Microwave Access (WiMAX) was introduced by WMANs to distribute broadband wireless data over large area.
Wireless Wide Area Networks (WWANs)
A wide area network is a communications network utilizing devices such as telephone lines, antenna, satellite dishes, and microwaves to span a relatively large geographical area. It usually operates on the 2.4 GHz.
Mobile Devices Networks
Global System for Mobile Communications (GSM) and Personal Communication Service (PCS) are the examples of cellular network to carry data. GSM is the most popular standard using by cell phones.
2.3 Functions and Types of WLANs
WLAN is the most popular among those five types of wireless network. It provides wireless connectivity within a finite coverage area. It can be install or set up easily. Anyone can create their own wireless LAN in their home or office. There are three types of wireless LANs, which is Peer-to-peer (P2P), Bridge and Wireless Distribution System (WDS).
2.3.1 Peer-to-peer (P2P)
More than one computer can connected without going through a separate server computer when using this network. It can be an ad-hoc connection to transfer files. If special protocols and applications establish direct relationships among users over the internet, P2P network can be a network on a much grander scale.
The diagram above shows that how a P2P network operates. Computer can transfer files or communicate with every each computer. A printer connect to one computer can be use by other computers on this network
Local area network (LANs) can connect to other local area network that may use the same or a different protocol by using this function. For example, ten users equipped with network in 802.11 standards may associate with a single access point that connects to an Ethernet network. Diagram below shows how a Bridge network operates.
2.3.3 Wireless Distribution System (WDS)
A distribution system can wired or wireless. In IEEE 802.11, this system allows the interconnection of access points wirelessly. It is possible to expand large wireless networks by linking several wireless access points without need for wired backbone to connect them. All traffic must be uses the same radio channel.WDS can be referred to as repeater mode. The reason is WDS appears to bridge and accept wireless clients at the same time. Diagram below shows a wireless distribution system.
2.4 Protocols of IEEE 802.11 Standards
The institute of Electrical and Electronic Engineers or IEEE is the worldâ€™s largest professional organization. It performs the standards making and maintaining functions. The standard used in wireless LAN is IEEE 802.11. Several specifications can be found in the 802.11 family:
It is an original version of the standard IEEE 802.11. It applies to wireless LANs and provides two net bit rates of 1 or 2 Mbps transmission in 2.4GHz band by using direct sequence spread spectrum (DSSS) or frequency spread spectrum (FHSS).
It is apply to wireless LANs by this extension of 802.11. Maximum net data rate up to 54-Mbps are provided in the 5GHz band. The modulation technique of 802.11a is orthogonal frequency division multiplexing (OFDM). The encoding scheme of OFDM is rather used by it than DSSS or FHSS.
Wireless LANs is applying by this extension of 802.11. 11Mbps transmission is provided in the 2.4GHz band. DSSS is only used by it. If compared to Ethernet, 802.11b allows wireless functionality.
It has a frequency band of 2.4GHz and enables the transmission over short distances at data rate up to 54Mbps. Its modulation technique is OFDM.
The real speed would be 100Mbit/s. It is faster than 802.11g. It required 2.4GHz and 5GHz of frequency bands. It builds upon previous 802.11 standards by adding the multiple-input multiple-output antennas (MIMO). The additional antennas will increase data throughput through spatial multiplexing.
2.5 Relationship between Wireless LANs and Wi-Fi
Wireless Fidelity (Wi-Fi) was introduced by an organization called Wi-Fi Alliance and defines it as any wireless local area network product that based on IEEE 802.11 standards. Originally, 802.11b standard can only be used by Wi-Fi in the frequency band of 2.4GHz. Today, it can apply to any 802.11 standard products. It uses radio technology to do the connection between the sender and receiver without wire and reducing the costs of expansion and network deployment. Wi-Fi has gained acceptance in many places, such as businesses, schools, agencies, and home and so on.