1. WiMAX (IEEE 802.16)
Presented
By:
Muhammad Israr Akbar
INU Peshawar
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2.  Introduction
 Overview of the IEEE 802.16 Standard
 Application
 Physical layer
 MAC Layer
 WIMAX versus Wi-Fi
 Conclusion
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3.  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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4.  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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5.  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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6.  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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7.  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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8.  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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9.  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

11. 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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12. 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]

14. 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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15.  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]

17.  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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18.  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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