Broadband wireless access (BWA) allows for the provision of high-speed Internet services without building physical structures consisting of fiber, coax or category 5 twisted pair in residential houses and business premises, relying instead on base transceiver stations (BTS) to transmit the bandwidth. However, at the initial stages, there weren’t any defined standards for building the Systems which resulted in a variety of software and hardware. The acceptance level is therefore low as the prices for these products are often kept high. As such, IEEE standard 802. 16 was developed by The Institute of Electrical and Electronics Engineers Standards Association (IEEE-SA) which sought to make Broadband Wireless access (BWA) more acceptable. The official standard was approved in April 2002 and is now known as ‘Air Interface for Fixed Broadband Wireless Access System’.
It is also known as wireless Metropolitan Area Network (MAN) or wireless Local Loop. (References from Computer Network, Andrew S. Tanenbaum, Person Education, 4 th Edition) IEEE 802. 16 deals with the ‘first-mile / last -mile’ connection in wireless MAN which refers to the topology between customer and central office / head end. It characterises the medium access control (MAC) layer that supports multiple physical layer specifications which customize the bandwidth between 10 and 66 GHz to the frequency band usage. The standard defines per station and per connection as the 2 forms of bandwidth allocation.
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For per station, the bandwidth is released to its users after it amasses all the requests and when it has been allocated the resources. For per connection, the BTS manages each connection directly. IEEE 802. 16 standard specifies a protocol that support low latency applications such as voice and videos and provides broadband connectivity without requiring a direct line of sight between subscriber terminals and the base transceiver station (BTS).
It can support a large number of subscribers from a single BTS, accelerating the introduction of wireless broadband equipment into the marketplace, speeding up last-mile broadband deployment worldwide by enabling service providers to increase system performance and reliability while reducing their equipment costs and investment risks due to mass production of the software / hardware .
The 802. 16 Protocol Stack is different from the Logical Link Control protocols which have been used with other LAN standards. The difference lies in the security sub layer that provides customer separation through encryption mechanisms and encryption key management. The MAC sub layer manages the data transfer mechanism while the service specific convergence sub layers deal with different services such as voice, video, data transfer and basic Internet access that can be provided over 802. 16. As such, the 802.
16 Protocol Stack is different from most other IEEE standards. The physical layer specifies the frequency band, the modulation scheme, error-correction techniques, synchronization between transmitter and receiver, data rate and the time-division multiplexing (TDM) structure. (References from web last accessed on 11 Mar 2004) The 802. 16 a standard specifies three physical layers for services: a single-carrier access method which was retained for special-purpose networks, a 256-carrier orthogonal frequency division multiplexed (OFDM) multi carrier for mainstream applications, and a special ‘OFDMa’s standard with 2, 048 carriers, which can be used for selective multi cast applications and advanced multiplexing options in tiered metro networks. (References from web last accessed on 10 Mar 2004) With the introduction of BWA, networks can be set up within a shorter time by installing base stations to create ‘Hotspots’ for high-capacity wireless access system. It streamlines business processes and increases demand for fast internet connection for data, video and voice services.
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BWA can extend fibre optic networks and provide more capacity than the ‘traditional’ Digital Subscriber Line (DSL) and cable networks. It also eliminates the need to construct and maintain physical subscriber structure, thus making it more popular due to lower overhead and increased mobility. The MAC common part sub layer provides the security for BWA in terms of authentication and registration. It is more secure than Wired Equivalent Privacy (WEP), a security protocol for wireless local area networks (WLANs) which are more vulnerable to tampering as it is used at the two lowest layers of the OSI model – the data link and physical layers. Due to the flaw in WEP, other security practises such as security practices such as password protection, end-to-end encryption and authentication are often used in addition to it.