On Demand Mode (Peer-to-Peer)

Each mobile device, also known as a mobile client, communicates with the other devices in the network, within a specified transmission range or cell. If a client has to communicate with a device outside the specified cell, a client within that cell must act as a gateway and perform the necessary routing.

Infrastructure Mode (Wireless LAN)

Communications between multiple wireless clients are routed by a central station known as an “access point.” The access point acts as a bridge and forwards all communications to the appropriate client in the network whether wireless or wired. Besides having routing mechanisms, the access point also has as a Dynamic Host Configuration Protocol (DHCP) server and other features that facilitate wireless communications in a small to large business environment. Residential gateways are similar to access points, but do not have advanced management features required for corporate networks or high-traffic environments. A wireless client must first be authenticated, and then associated with an access point before it can perform any communications. Enterprises that have a strong mobile e-commerce strategy must make a selection from the major wireless LAN specifications available in the market today.

802.11b

The 802.11b specification was defined by the Institute of Electrical and Electronics Engineers (IEEE). The 802.11b is used as an extension of Ethernet to wireless communication, and as such is quite flexible about the different kinds of network traffic that passes over it. It is primarily used for Transmission Control Protocol/Internet Protocol (TCP/IP), but also supports AppleTalk and other PC file sharing standards. Disparate systems like PCs and Macs may communicate over 802.11b, using PC or Peripheral Component Interconnect (PCI) cards, and even some of the newer hardware, utilizing Universal Serial Bus (USB) and other forms of 802.11b based wireless network cards. Adapters for PDAs, such as Palm OS and PocketPC based devices are also available.

The 802.11b facilitates the wireless transmission of approximately 11 Mbps (Megabits per second) of raw data at distances ranging from a few feet to several hundred feet over the standard 2.4 GHz (GigaHertz) unlicensed band. The coverage distance depends on line of sight, obstacles, and unforeseen obstacles. Several new protocols based on 802.11b, but not compatible with it, are also being released.

802.11a

Protocol 802.11a transmits 54 Mbps over the 5 GHz band. This is ideal for large data file transfers and bandwidth intensive applications over a limited area. Although performance and throughput are significantly increased, the transmission range is notably reduced.

802.11g

Protocol 802.11g transmits 22 Mbps over 2.4 GHz. This specification is considered to be the next generation wireless network platform for the enterprise, workingt wice as fast as the current 802.11b specification. However, this is still a work in progress.

Bluetooth

This wireless network specification, defined by the Bluetooth Special Interest Group, is ideally suited for Personal Area Networks (PANs) that operate in short ranges and need a robust wireless network that allows transmission of bandwidth intensive information. Bluetooth specifications also promote interdevice communications, so mobile phones can communicate to PDAs, notebook PCs with laptops, and so on. Although it uses the unlicensed 2.4 GHz band for transmission, its transmission is faster than the 802.11b networks in both on demand and infrastructure modes. Bluetooth’s range is, however, much less. Bluetooth technology works well for on demand networks and situations in which device-to-device communication is desired. For example, you can wirelessly connect from your PDA to a printer to print documents, or perhaps synchronize your desktop with your PDA over the air.