Wireless media carry data in the form of electromagnetic signals using radio or microwave frequencies.
Wireless media provides the best mobility options , and the number of wireless-enabled devices continues to increase. As network bandwidth options increase, wireless is quickly gaining in popularity in enterprise networks. Wireless does have some important point to consider before planning:-
- Coverage area: Wireless data communication technologies work well in open environments. However, certain construction materials used in buildings and structures, and the local terrain, will limit the effective coverage.
- Interference: Wireless is at risk to intrusion and can be disrupted by such common devices as household cordless phones, some types of fluorescent lights, microwave ovens, and other wireless communications.
- Security: Wireless communication coverage requires no access to a physical strand of media. thus, devices and users, not authorized for access to the network, can gain access to the transmission. Network security is a main component of wireless network administration.
- Shared medium: WLANs work in half-duplex, which means just one device can send or receive at a time. The wireless medium is shared amongst all wireless users. The more users need to access the WLAN simultaneously, results in less bandwidth for each user.
Types of Wireless Media
The IEEE and telecommunications industry standards for wireless data communications cover both the data link and physical layers. cellular and satellite communications can also provide data network connectivity. But, we are not discussing these wireless technologies here in this chapter. In each of these standards, physical layer specifications are applied to areas that include:
- Transmission Frequency
- Transmission power of transmission
- Data to radio signal encoding
- Signal reception and decoding requirements
- Antenna design and construction
Wi-Fi is a trademark of the Wi-Fi Alliance. Wi-Fi is used with certified products that belong to WLAN devices that are based on the IEEE 802.11 standards. Different standards is following:-
WI-FI standard IEEE 802.11
WLAN technology, commonly referred to as Wi-Fi. WLAN uses a protocol known as Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA). The wireless NIC must first listen before transmitting to determine if the radio channel is clear. If another wireless device is transmitting, then the NIC must wait until the channel is clear. CSMA/CA is will be discussed later.
Bluetooth standard IEEE 802.15
Wireless Personal Area Network (WPAN) standard, commonly known as “Bluetooth”, uses a device pairing process to communicate over distances from 1 to 100 meters.
WI-MAX Standard IEEE 802.16
Usually known as Worldwide Interoperability for Microwave Access (WiMAX), uses a point-to-multipoint topology to provide wireless broadband access.
Wireless LAN (WLAN)
General wireless data implementation wireless LAN requires the following network devices:
- Wireless Access Point (AP): In a wireless local area network (WLAN), an access point (AP) is a station that transmits and receives data. An access point connects users to other users within the network and also can serve as the point of interconnection between the WLAN and a fixed wire network. Each access point can serve multiple users within a defined network area; as people move beyond the range of one access point, they are automatically handed over to the next one. A small WLAN may only require a single access point; the number required increases as a function of the number of network users and the physical size of the network.
- Wireless NIC adapters: Provide wireless communication capability to each network host.
As the technology has developed, a number of WLAN Ethernet-based standards have emerged. Care needs to be taken in purchasing wireless devices to ensure compatibility and interoperability.
The benefits of wireless data communications technologies are clear, particularly the savings on costly premises wiring and the convenience of host mobility