WiMAX (IEEE 802.16)

Presented By:

Muhammad Israr AkbarINU Peshawar

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Introduction Overview of the IEEE 802.16 Standard Application Physical layer MAC Layer WIMAX versus Wi-Fi Conclusion

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The acronym WiMAX stands for “Worldwide Interoperability for Microwave Access”. It is based on IEEE 802.16 standard.

IEEE 802.16 is the IEEE standard for Wireless Metropolitan Area Network (Wireless MAN).

It specifies the air interface for fixed, portable, and mobile broadband wireless access (BWA) systems supporting multimedia services.

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WiMAX aims to provide wireless broadband services with a target range of up to 31 miles at a transmission rate exceeding 100 Mbps.

It is also to provide a wireless alternative to cable, DSL and T1/E1 for last mile access.

The term IEEE 802.16 and WIMAX are used interchangeably.

WiMAX is to IEEE 802.16 what Wi-Fi is to IEEE 802.11

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Designed for point-to-point (PTP) and point-to-multipoint (PTM) topologies but mainly deployed for point to multipoint topologies. It also support mesh topologies.

In PTM a base station (BS) services many subscriber stations (SS) which are mounted outdoors.

IEEE 802.16 has three major versions; 802.16-2001, 802.16-2004 and IEEE 802.16-2005.

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Addresses fixed line of sight connections and operates in the licensed frequency range between 10 GHz and 66 GHz.

At these high frequency range there are more available bandwidth and reduced risk of interference.

Has a maximum coverage of 5km.

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Designed to operate in lower frequency range; 2-11 GHz.

Support Non-line of sight (NLOS) operation.

Operates in both licensed (3.5 GHz) and unlicensed (5.8 GHz).

Operates with a range of up to 50km and data rates of up to 75Mbps.

It is the most supported version of the standard by vendors.

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Support mobility and will standardize networking between fixed base stations and mobile devices.

Would enable high-speed signal handoffs necessary for communications with users moving at vehicular speeds which is below 100km/h.

It will provide a symmetric (up and down) bit rates of 70Mbps.

operate in the frequency range between 2-6 GHz.

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To provide a wireless alternative to cable, DSL and T1/E1 for last mile access especially in areas where wire broadband access are absent.

Serves as E1/T1 replacements for small and medium size businesses.

Provide residential ‘wireless DSL’ for broadband Internet at home.

It can be used as wireless backhaul for Wi-Fi hotspot and cellular companies.

Operators/carriers can use it as a backup backbone.

It can be used in disaster recovery scenes where the wired networks have broken down.

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Figure 1: WiMAX Applications

IEEE 802.16-2001 Designed for line-of-sight propagation because

the frequency range is between 10-66 GHz. single-carrier modulation is used and the air

interface is called “WirelessMAN-SC”. In PTM architecture, the BS transmits a TDM

signal, with individual subscriber stations allocated time slots serially. While access in the uplink direction is by Time-division Multiple Access (TDMA).

uses both time division duplexing (TDD) and frequency-division duplexing (FDD).

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IEEE 802.16-2004 (802.16d) Design for the 2-11 GHz range and is more

complex because of interference. Three air interfaces are specified for this

range, which are; ◦ Wireless MAN-SC uses single carrier modulation ◦ Wireless MAN-OFDM(Orthogonal frequency-division multiplexing (OFDM )

uses a 256-carrier FDM. Provides multiple access to different stations through TDMA. (Most adopted by vendors)

◦ Wireless MAN-OFDMA uses a 2,048-carrier OFDM scheme. Provides multiple access by assigning a subset of the carriers to an individual receiver

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Table 1: Physical Layer Features [5]

IEEE 802.16-2005 (802.16e) The main technologies used for it’s physical layer

are OFDMA and an improved version called Scalable OFDMA (SOFDMA).

OFDMA is required in the implementation of 802.16e and also for the certification of 802.16e devices.

SOFDMA scales the number of sub-carriers in a channel with possible values of 128, 512, 1024, and 2,048.

OFDMA and SOFDMA also benefit fixed broadband service because carriers can allocate spectrum more efficiently and reduce interference.

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It is connection oriented and supports quality of service.

It uses a slotted TDMA protocol scheduled by the base terminal station to allocate capacity to subscribers.

Supports both Time Division Duplex (TDD) and Frequency Division Duplex (FDD) and, also Half Duplex-FDD.

supports quality of service (QoS) for stations through adaptive allocation of the uplink and downlink traffic.

It also supports different transport technologies such as IPv4, IPv6, Ethernet, Asynchronous Transfer Mode (ATM) and any future protocol not yet developed.

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Table 2: MAC Layer Features [5]

WiMAX was designed to replace the last-mile wired-broadband access networks while Wi-Fi was created for providing services into LAN networks.

At the PHY layer, WiMAX channel sizes ranges from 1.75 MHz to 20 MHz while Wi-Fi based products require at least 20 MHz for each channel.

Wi-Fi uses the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) which is not an efficient protocol. The MAC layer in WiMAX has been designed to scale from one to up 100s users within one RF channel.

In WiMAX, the base station assigns a QoS class to each connection. In 802.11, QoS was not considered in the early stage of its implementation.

WiMAX supports many transport technologies, such as ATM, IPv4, and IPv6 which are not supported by Wi-Fi.

WiMAX has the ability to support longer range transmission from 2 to 40 kilometers. While 802.11 was designed for low power consumption which limit the coverage to hundreds of meters.

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WiMAX will no doubt be a viable alternative to DSL and cable connections.

It has changed the scene of wireless broadband by standardizing an industry which provides proprietary solutions.

There have been more than 150 commercial trials and WiMAX network deployments that have taken place worldwide.

In January 2006, Samsung revealed its WiMAX enabled M8000 handset, which connects directly to WiMAX base stations through 802.16e. [2]

Most of the frequency range where WiMAX can operate is really congested and most have been allocated to carriers and other users.

WiMAX mobile version, may face serious competition from IEEE 802.20 mobile broadband technology and 3G cellular systems.

It will have stiff competition with already establish broadband access technology such as DSL and cable modem.

The Mobile version (802.16e) is not compatible with the fixed version (802.16d) which has slow down the release of WiMAX equipment into the market by vendors.

WiMAX is the future of wireless broadband access technology.

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