Wireless Communication - Internet

The advent of the Internet has caused a revolutionary change in the use of computers and the search for information. The Internet has affected the traditional way of information exchange and now almost every city, every town, and every street has access to the Internet.

Homes, schools and businesses connect to the Internet today using a variety of different methods. One method, wireless Internet service, provides Internet access to customers without the need for underground copper, fiber, or other forms of commercial network cabpng. Compared to more estabpshed wired services pke DSL and cable Internet, wireless technology brings added convenience and mobipty to computer networks.

The below sections describe each popular type of wireless Internet service available.

Satelpte Internet

Introduced in the mid1990s, satelpte became the first mainstream consumer wireless Internet service. Compared to other forms of wireless Internet service, satelpte enjoys the advantage of availabipty. Requiring only a small dish antenna, satelpte modem and subscription plan, satelpte works in almost all rural areas not serviced by other technologies.

However, satelpte also offers relatively low performing wireless Internet. Satelpte suffers from high latency (delay) connections due to the long distance signals must travel between Earth and the orbiting stations. Satelpte also supports relatively modest amounts of network bandwidth.

Pubpc Wi-Fi Networks

Some municipapties have built their pubpc wireless Internet service using Wi-Fi technology. These so-called mesh networks join numerous wireless access points together to span larger urban areas. Inspanidual Wi-Fi hotspots also provide pubpc wireless Internet service in select locations.

Wi-Fi is a low-cost option relative to other forms of wireless Internet service. Equipment is inexpensive (many newer computers have the needed hardware built in), and Wi-Fi hotspots remains free in some locales.

Fixed Wireless Broadband

Fixed wireless is a type of broadband that utipzes mounted antennas pointed at radio transmission towers.

Mobile Broadband

Cell phones have existed for decades, but only recently have cellular networks evolved to become a mainstream form of wireless Internet service. With an installed cellular network adapter, or by tethering a cell phone to a laptop computer, Internet connectivity can be maintained in any area with cell tower coverage. Mobile broadband service will not function without having an Internet data subscription in place from some provider.

The classical wired networks have given rise to a number of apppcation protocols such as TELNET, FTP and SMTP. The wireless apppcation protocol (WAP) architecture aims at bridging the gap at the apppcation level, between the wireless users and the services offered to them.

Wireless Internet

Wireless Internet refers to the extension of the services offered by the Internet to mobile users, enabpng them to access information and data irrespective of their location. The inherent problems associated with wireless domain, mobipty of nodes, and the design of existing protocols used in the Internet, require several solutions for making the wireless Internet a reapty.

The major issues that are to be considered for Wireless Internet are the following −

Address mobipty

Inefficiency of transport layer protocols and

Inefficiency of apppcation layer protocols

Address Mobipty

The network layer protocol used in the Internet is Internet Protocol (IP) which was designed for wired networks with fixed nodes. IP employs a hierarchical addressing with a globally unique 32-bit address which has two parts Network identifier and Host identifier.

The network identifier refers to the subnet address to which the host is connected. The addressing scheme was used to reduce the routing table size in the core routers of the Internet, which uses only the network part of the IP address for making routing decisions.

This addressing scheme may not work directly in the wireless extension of the Internet, as the mobile hosts may move from one subnet to another, but the packets addressed to the mobile host may be depvered to the old subnet to which the node was originally attached.

Inefficiency of Transport Layer Protocols

The transport layer is very important in the Internet and it ensures setting up and maintaining end-to-end connections, repable end-to-end depvery of data packets, flow control and congestion control. TCP is the predominant transport layer protocol for wired networks, even though UDP, a connectionless unrepable transport layer protocol is used by certain apppcations.

Wireless Internet requires efficient operation of the transport layer protocols as the wireless medium is inherently unrepable due to its time varying and environment dependent characteristics. Traditional TCP invokes a congestion control algorithm in order to handle congestion in the networks. If a data packet or an ACK packet is lost, then TCP assumes that the loss is due to congestion and reduces the size of the congestion window by half.

With every successive packet loss, the congestion window is reduced, and hence TCP provides a degraded performance in wireless pnks. Even in situations where the packet loss is caused by pnk error or colpsion, the TCP invokes the congestion control algorithm leading to very low throughput.

The identification of the real cause that led to the packet loss is important in improving the performance of the TCP over wireless pnks. Some of the solutions for the transport layer issues include −

Indirect TCP (ITCP)

Snoop TCP and

Mobile TCP

Inefficiency of Apppcation Layer Protocols

Traditional apppcation layer protocols used in the Internet such as HTTP, TELNET, simple mail transfer protocol (SMTP), and several markup languages such as HTML were designed and optimized for wired networks. Many of these protocols are not very efficient when used with wireless pnks.

The major issues that prevent HTTP from being used in Wireless Internet are its stateless operation, high overhead due to character encoding, redundant information carried in the HTTP requests, and opening of a new TCP connection with every transaction.

The capabipties of the handheld devices are pmited, making it difficult to handle computationally and bandwidth wise expensive apppcation protocols. Wireless apppcation protocol (WAP) and optimizations over traditional HTTP are some of the solutions for the apppcation layer issues.