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802.16e – Mobile WiMAX
Mikko Kivistö - mikko.kivisto(at)tut.fi
Petri Järvelä – petri.jarvela(at)tut.fi

Introduction
802.16e provides enhancements to 802.16-2004 to support
subscriber stations moving at vehicular speeds
standard specifies a system for a combined fixed and mobile
broadband wireless access.

Key advantages of 802.16e
Mobile WiMAX physical layer is based on Scalable
OFDMA technology.
The new technologies employed for Mobile WiMAX result
in lower equipment complexity and simpler mobility
management due to the all-IP core network and provide
Mobile WiMAX systems with many other advantages over
CDMA-based 3G systems

Key advantages of 802.16e
Tolerance to Multipath and Self-Interference
Scalable Channel Bandwidth
Orthogonal Uplink Multiple Access
Support for Spectrally-Efficient TDD
Frequency-Selective Scheduling
Fractional Frequency Reuse
Fine Quality of Service (QoS)
Advanced Antenna Technology

Overview
Certification Process
Frequency Bands
Reference Model

Certification Process
In December, 2005 the IEEE ratified the 802.16e
amendment to the 802.16 standard.
First certification laboratory was established in Cetecom
Labs in Malaga, Spain in the same year
IEEE has moved it´s responsibility of WiMAX
certifications to WiMAX Forum
First commercial availability for 802.16e in 7/2006
More advanced mobile functionality will gradually be
added through support for high-speed handoffs, roaming
and multiple antenna technologies such as MIMO and
beamforming and be available in equipment in the second
half of 2007.

Frequency Bands
IEEE 802.16e-2005 will initially operate in the 2.3 GHz, 2.5
GHz, 3.3 GHz, 3.4-3.8 GHz spectrum bands.
Support for additional bands will be added on the basis of
market demand and new spectrum allocations.
Release-1 of 802.16e profiles will cover 5, 7, 8.75, and 10
MHz channel bandwidths for frequency bands above.

Reference Model
ASN = Access Service Network
CSN = Connctivity Service Network
NSP = Network Service Provider
ASP = Application Service Provider
NAP = Network Access Provider

Physical Layer description
The Mobile WiMAX Air Interface adopts Orthogonal
Frequency Division Multiple Access (OFDMA) for
improved multi-path performance in non-line-of-sight
environments.
Scalable OFDMA (SOFDMA) is introduced in the IEEE
802.16e Amendment to support scalable channel bandwidths
from 1.25 to 20 MHz.
The scalability is supported by adjusting the FFT size while
fixing the sub-carrier frequency spacing at 10.94 kHz.

Physical Layer Description
Since the resource unit sub-carrier bandwidth and symbol
duration is fixed, the impact to higher layers is minimal
when scaling the bandwidth.
802.16e systems offer scalability in both radio access
technology and network architecture, thus providing a great
deal of flexibility in network deployment options and
service offerings.
802.16e supports TDD and Full and Half-Duplex FDD
operation.

Data Rates
High Data Rates: The inclusion of MIMO antenna
techniques along with flexible sub-channelization schemes,
Advanced Coding and Modulation all enable the 802.16e
technology to support
• peak DL data rates up to 63 Mbps per sector and
• peak UL data rates up to 28 Mbps per sector
in a 10 MHz channel.

Other Advanced Features for
802.16e
Adaptive modulation and coding (AMC)
Hybrid Automatic Repeat Request (HARQ)
Fast Channel Feedback (CQICH)

SOFDMA and 802.16e specs.
SOFDMA
Data Rates

Mobility Management
Power management and handoff are two important issues for
mobile applications.
Mobile WiMAX supports Sleep Mode and Idle Mode.
Mobile WiMAX also supports seamless handoff to enable
the Mobile Station (MS) to switch from one base station to
another at vehicular speeds without interrupting the
connection.

Power Management
Two modes to manage efficient power operation
Sleep Mode
Idle Mode
Idle Mode
provides a mechanism for the MS to become periodically
available
remove the requirement for handoff and other normal
operations
eliminate air interface and network handoff traffic from
essentially inactive MSs

Power Management
Sleep Mode
MS conducts pre-negotiated periods of absence from the
Serving Base Station (SBS) air interface. These periods are
interpreted as unavailability of the MS to SBS concerning
DL or UL traffic.
Sleep Mode minimize MS power usage and the usage of
SBS’s air interface resources
Handoffs between Base Stations are available during Sleep
Mode

Handoff
Mobile WiMAX supports three handoff methods
Hard Handoff , HHO (mandatory)
Fast Base Station Switching , FBSS (optional)
Macro Diversity Handover , MDHO (optional)
When FBSS is supported
MS and BS keep up a list of BSs that are involved in
FBSS with the MS → Active set
MS defines an Anchor BS and communicates only with
it.

When FBSS is supported
transition between Anchor BSs is carried out without any
HO signalling
begins with a decision by an MS to receive or transmit data
from the Anchor BS that may change within the active set.
important requirement of FBSS is that the data is
simultaneously transmitted to all members of an active set of
BSs that are able to serve the MS.
Handoff

Handoff
When MDHO is supported
MS and BS maintain an active set of BSs that are involved
in MDHO with the MS.
An Anchor BS is defined
MS communicates with all BSs in the active set of uplink
and downlink unicast messages and traffic
begins when a MS decides to transmit or receive unicast
messages and traffic
from multiple BSs in the same time interval

Smart antenna technologies typically involve complex
vector or matrix operations on signals due to multiple
antennas. OFDMA allows smart antenna operations to
be performed on vector-flat sub-carriers.
Mobile WiMAX supports a full range of smart
antenna technologies to enhance system performance.
Advanced Features of Mobile
WiMAX

WiMAX
Beamforming
→ better coverage and capacity
and
→ reduce outage probability
Space-Time Code (STC)
transmit diversity codes are used to provide spatial
diversity
→ reduce fade margin

Spatial Multiplexing (SM)
→ advantage of higher peak rates
→ increases throughput
multiple streams are transmitted over multiple antennas
both receiver and transmitter must have multiple antennas to
achieve higher throughput
WiMAX

WiMAX
Fractional Frequency Reuse
all cells/sectors operate on the same frequency channel to
maximize spectral efficiency.
users operate on subchannels, which only occupy a small
fraction of the whole channel bandwidth
the flexible sub-channel reuse is facilitated by sub-channel
segmentation and permutation zone

Multicast and Broadcast Service (MBS)
combines the best features of DVB-H, MediaFLO and 3GPP
E-UTRA and satisfies the following requirements:
High data rate and coverage using a Single Frequency
Network (SFN)
Flexible allocation of radio resources
Low MS power consumption
Support of data-casting in addition to audio and video
streams
Low channel switching time
WiMAX

Comparing Mobile WiMAX to
1xEVDO and HSPA

Summary
802.16e can offer full-mobility for WiMAX and thus it can
be considered as a real competitor for 3G for example in IP-
traffic (VoIP / IPTV).
802.16e supports seamless handoff which provides
switching between base stations in vehicular speeds.
Mobile WiMAX uses Scalable OFDMA multiplexing which
maximizes the spectral efficiency.

References
Mobile WiMAX – Part I: A Technical Overview and Performance
Evaluation, Aug. 2006, Copyright 2006 WiMAX Forum
Mobile WiMAX – Part II: A Comparative Analysis, May 2006,
Copyright 2006 WiMAX Forum
802.16e-2005 Standard, LAN/MAN Standards Committee of IEEE
Computer Society
Fixed, nomadic, portable and mobile applications for 802.16-2004
and 802.16e WiMAX networks, Nov. 2005, Prepared by Senza Fili
Consulting on behalf of the WIMAX Forum
Mobile WiMAX Performance and Comparative Summary, Sep
2006, Copyright 2006 WiMAX Forum

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