3. Introduction
• Stands for “Worldwide Interoperability for
Microwave Access”.
• Based on IEEE 802.16 standard.
• 802.16 is the IEEE standard for Wireless
Metropolitan Area Network (Wireless MAN).
• Specifies the air interface for fixed, portable, and
mobile broadband wireless access (BWA) systems
supporting multimedia services.
• Aims to provide wireless broadband services with a
target range of up to 31 miles at a transmission rate
exceeding 100 Mbps.
4. Introduction
• 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 where Wi-Fi is to IEEE
802.11
6. Overview Of the IEEE 802.16 Standard
• 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.
• IEEE 802.16 has three major versions:
IEEE 802.16-2001.
IEEE 802.16d-2004(Fixed).
IEEE 802.16e-2005(Mobile).
7. IEEE 802.16-2001
• Addresses fixed line of sight (LOS) connections and
operates in the licensed frequency range between 10
GHz and 66 GHz.
• At these high frequency range (reduced risk of
interference)
• Has a maximum coverage of 5km.
8. IEEE 802.16-2001
• Physical layer
• 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”.
9. IEEE 802.16-2001
• MAC
• Supports both Time Division Duplex (TDD) and
Frequency Division Duplex (FDD).
• It uses a slotted TDMA protocol scheduled by the base
terminal station to allocate capacity to subscribers.
• It also supports different transport technologies such as
IPv4, IPv6, Ethernet, Asynchronous Transfer Mode
(ATM).
• Provides mechanisms for authentication, key-sharing
and encryption.
11. IEEE 802.16d “Fixed”
• 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.
12. IEEE 802.16d “Fixed”
• PHY
• Design for the 2-11 GHz range and is more complex
because of interference.
• Three air interfaces are specified for this range, which are;
I. Wireless MAN-SC uses single carrier modulation .
II. Wireless MAN-OFDM uses a 256-carrier FDM.
Provides multiple access to different stations through
TDMA.
III. Wireless MAN-OFDMA uses a 2,048-carrier OFDM
scheme.
14. IEEE 802.16e “Mobile”
• 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 70Mbps.
• Operates in the frequency range between 2-6 GHz.
15. IEEE 802.16e “Mobile”
• PHY
• The main technologies used for it’s physical layer
are OFDMA and an improved version called
Scalable OFDMA (SOFDMA).
• SOFDMA scales the number of sub-carriers in a
channel with possible values of
128, 512, 1024, and 2,048.
16. IEEE 802.16e “Mobile”
• MAC
• It is connection oriented and supports quality of
service (QoS) for stations through adaptive
allocation of the uplink and downlink traffic.
18. Fixed Vs. Mobile
I. Mobility Management and Hand Offs
• The simplest difference between the fixed and
mobile is the fact that the mobile enables a hand-
off from one base station to another as the
user, in one session, moves from the coverage
zone of one base station to another. This is also
known as “mobility management”.
19. Fixed Vs. Mobile
II. OFDM vs. SOFDMA
• Orthogonal Frequency Division Multiplexing
(OFDM) breaks the wireless carrier into 256
sub-carriers .
• The two greatest advantages are:
(a) it mitigates inter symbol interference
(multipath)
(b) improves propagation of the signal, especially
in non-line of sight (NLOS) coverage zones.
20. Fixed Vs. Mobile
II. OFDM vs. SOFDMA
• OFDMA breaks the carrier into even more sub
carriers (up to 2048 sub carriers).
• The “mobile” WiMAX uses SOFDMA.
• The advantage of this is better propagation and
improved building penetration .
• The use of OFDMA should also enable the use of
smaller, less costly subscriber devices including
PC cards and USB devices.
21. Fixed Vs. Mobile
III. QoS
• 802.16e introduces Extended Real-Time Polling
Service (ERTPS). ERTPS allows the 802.16e
solution to manage traffic rates and transmission
policies as well as improving latency and jitter.
(VoIP) applications.
22. Future Works & Problems
• P802.16m (In progress) :Advanced Air Interface with
data rates of 100 Mbit/s mobile & 1 Gbit/s fixed.
• With “MIMO” (Downlink 128 Mbps/20 Mhz &
Uplink 56 Mbps 20 Mhz) Also known as Mobile
WiMAX Release 2 or
WirelessMAN-
• Problems: Advanced
Wimax Availability Problem (DoS)
Authentication Problem In WiMAX Mainly Security
Problem
(man-in-the-middle attack)
Policies (government), infrastructure(poor) and low income
23. References
• [1]. K. Fazel and S. Kaiser, M. Ergen, “Wikipedia ” ,30.04.2011, URL:
http://en.wikipedia.org/wiki/WiMAX.
• [2]. Sridhar Iyer, “WiMAX: IEEE 802.16 Wireless MANs” , K R School of
Information Technology, URL: http://www.it.iitb.ac.in/~sri.
• [3]. AFTAB AHMAD, “WIRELESS AND MOBILE DATA NETWORKS”, Wiley
& Sons, Inc., 1st Edition, 2005.
• [4]. Aruleba, Olakunle Michael, “WiMAX (IEEE 802.16)”, B.Sc.
Project, University of Windsor, 2007.
• [5]. Frank Ohrtman, “Fixed vs. Mobile WiMAX Mobility Monomania?”
, President, WMX Systems, LLC ,URL:http://www.MindCommerce.com, July
2007.
• [6]. White Paper, “WiMAX: E vs. D The Advantages of 802.16e over
802.16d”, URL: http:www.motorola.com/wi4, Motorola, Inc. 2007.
