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Write short notes on IEEE 802.16 Standard.
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1. IEEE 802.16 standard is based on broadband services for ‘Metropolitan Area Networks (MAN)’:

i. The IEEE 802.16 Standard provides wireless computer network access and internet access for MAN thus being an alternative to traditional cable, DSL, or TI offerings.

ii. 802.16 provide flexible, cost-effective, standard based means of filling gaps in broadband services not envisioned in a wired world.

iii. The advantages of systems based on 802.16 are multifold: faster provisioning of service, even in areas that are hard for wired infrastructure to reach, lower installation cost; and ability to overcome physical limitations of traditional wired infrastructure.

iv. Thus 802.16 based systems provide affordable last-mile broadband access for millions of subscribers in homes and businesses throughout the world.

2. Road-map of IEEE 802.16 standard

i. 802.16 (2001) was originally designed for10-66 GHZ. It specified ‘medium access control (MAC)’ and ‘physical (PHY)’ layers for air interface for fixed broadband wireless access system with ‘Line of sight (LOS)’ propagation.

ii. 802.16a (January 2003) was an extension of the original version. It covered frequency bands between 2 and 11 GHZ and enabled non line of sight (NLOS) operation.

iii. NLOS operation enabled the mounting of base stations on roofs of homes or buildings rather than towers or mountains. Trees and buildings were no longer an obstacle.

iv. The range of operation was up to 30 miles. The NLOS performance and throughputs are optimal in typical cell radius of 4 to 6 miles.

v. 802.16a introduced three physical layers- OFDM, OFDMA, Single carrier. It also introduced additional MAC functions; mesh topology support.

vi. 802.16a also provided an ideal wireless backhaul technology to connect 802.11 WLAN and commercial 802.11 hotspots with the Internet.

vii. 802.16d (July 2004) combined 802.16 and 802.16a with some modifications to MAC and PHY.

viii. 802.16e (December 2005) was an amendment to 802.16d. It had MAC modifications for limited mobility.

ix. 802.16e uses OFDMA in which carriers are divided among users to form sub channels. The coding and modulation are adapted separately for each sub channel.

x. SOFDMA is an enhancement of OFDMA that scale the number of subcarriers in a channel with possible values of 128, 512, 1024, and 2048.

xi. 802.16e includes power-saving and sleep modes to extend battery life if mobile devices.

xii. 802.16e also supports hard and soft handoff to provide users with seamless connections as they move across coverage areas of adjacent cells.

Fig10. OFDM and OFDMA in IEEE 802.16e

Fig10. OFDM and OFDMA in IEEE 802.16e

3. Features of 802.16 standards

i. The82.16 delivers high throughput at long ranges with a high spectral efficiency. Dynamic adaptive modulation allows base stations to trade off throughput for range.

ii. The 802.16 supports flexible channel bandwidths to accommodate easy cell planning in both licensed and unlicensed spectra worldwide.

iii. The 802.16 includes robust security features and QoS needed to support services that require low latency, such as voice and video.

iv. The 802.16 voice service can either be TDM voice or voice over IP (Vo IP).

v. Privacy and encryption features are also included to support secure transmission and data encryption.

vi. Applications of 802.16 are cellular backhaul, broadband on-demand, residential broadband, and best-connected wireless service.

vii. The worldwide interoperability for micro access inc. (WiMAX) forum, an industry group, focuses on creating advanced technology solution for high speed wide area Internet access and ensures operability among devices based on 802.16 standards from different manufacturers.

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