IEEE 802.16e/Mobile WiMAX
Moise Effo
IEEE 802.16 Overview
IEEE 802.16e Protocol Stack
NETWORK ARCHITECTURE
PHYSICAL LAYER DESCRIPTION
 The Mobile Wimax adopts Orthogonal Frequency Division
Multiple Access (OFDMA) for improved multi-path performance in
non-line-of-sight environments by:
Multiplexing operation of data streams from multiple users
Dynamically assign a subset of sub-channels to individual users.
Scalable OFDMA (SOFDMA) is introduced in the IEEE 802.16e
an amendment to support scalable channel bandwidths from 1.25 to
20 MHz.
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.
PHYSICAL LAYER DESCRIPTION
 Adaptive modulation and coding (AMC) is the matching of
the modulation, coding and signal strength and protocol parameters
to the conditions on the radio link.
 Hybrid Automatic Repeat Request (HARQ) is a combination of
high-rate forward error-correcting coding (FEC), and ARQ
(Automatic Repeat-reQuest) error-control for detectable-butuncorrectable errors.
 Fast Channel Feedback (CQICH) is a method of communicating
feedback information between a mobile station and a base station by
determining a need to request bandwidth allocation.
MAC LAYER DESCRIPTION
Quality of service (QoS) is provided via service flows. This is a
unidirectional flow of packets that is provided with a particular set of
QoS parameters
Service
Definition
Typical Applications
QoS Specifications
Unsolicited Grant Service (UGS)
Real-time data streams comprising
fixed-size data packets issued at
periodic intervals.
T1/E1 transport, VoIP without
silence suppression.
-Maximum Sustained Rate
-Maximum Latency
Tolerance
-Jitter Tolerance
Extended Real-time Polling Service
(ErtPS)
Real-time service flows that generate
variable-sized data packets on a
periodic basis.
VoIP with silence suppression.
-Minimum Reserved Rate
-Maximum Sustained Rate
-Maximum Latency
Tolerance
-Jitter Tolerance
-Traffic Priority
Real-time Polling Service (rtPS)
Real-time data streams comprising
variable-sized data packets that are
issued at periodic intervals.
MPEG Video.
-Minimum Reserved Rate
-Maximum Sustained Rate
-Maximum Latency
Tolerance
-Traffic Priority
Non-real-time Polling Service (nrtPS).
Delay-tolerant data streams
comprising variable-sized data
packets for which minimum data rate
is required.
FTP with guaranteed minimum
throughout.
-Minimum Reserved Rate
-Maximum Sustained Rate
-Traffic Priority
Best Effort (BE)
Data streams for which no minimum
service level is required and therefore
may be handled on a space-available
basis.
HTTP.
-Maximum Sustained Rate
-Traffic Priority
MAC LAYER DESCRIPTION
Scheduling service is designed to efficiently deliver broadband data
services including voice, data, and video over time-varying broadband
wireless channel. The MAC scheduling service has the following
properties that enable the broadband data service:
 Fast Data Scheduler
 Scheduling for both DL and UL
 Dynamic Resource Allocation
 QoS Oriented
 Frequency Selective Scheduling
MAC LAYER DESCRIPTION
Mobility management
 Power management Mobile Wimax supports the two modes for
power efficient operation:
- Sleep Mode
- Idle Mode
 Handoff there are handoffs methods supported by the mobile
Wimax:
- Hard Handoff (HHO)
- Fast Base Station Switching (FBSS)
- Macro Diversity Handover (MDHO)
MAC LAYER DESCRIPTION
Security
• Key Management Protocol for Traffic Encryption Control,
Handoff Key Exchange and Multicast/Broadcast security
messages.
• Device/User Authentication by providing support for credential
that are SIM-based.
• Traffic Encryption, a cipher is used for the protection all the
user data over the Mobil Wimax MAC interface. (AES-CCM)
• Control Message Protection using AES Based CMAC.
• Fast Handover Support there is a 3-way Handshake scheme to
optimize the re-authentication mechanisms for fast handovers.
ADVANCED FEATURES OF MOBILE WIMAX
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. Complex equalizers are not
required to compensate for frequency selective fading.
Mobile Wimax supports a full range of smart antenna technologies to
enhance system performance.
Beamforming for a better coverage and capacity of the system and
reduce outage probability.
Space-Time Code(STC) transmit diversity codes are used to provide
spatial diversity and reduce fade margin.
ADVANCED FEATURES OF MOBILE WIMAX
Smart antenna technologies
Spatial Multiplexing(SM) is to take advantage of higher peak rates
and increases throughput.
• multiple streams are transmitted over multiple antennas
• both receiver and transmitter must have multiple antennas to achieve
higher throughput.
The inclusion of MIMO antenna techniques along with flexible subchannelization schemes, Advanced Coding and Modulation all enable
the802.16e technology to support a high data rate:
•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.
ADVANCED FEATURES OF MOBILE WIMAX
 Fractional Frequency reuse
• All cells/sectors operate on the same frequency channel to maximize
spectral efficiency.
• Users operate on sub-channels, 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
ADVANCED FEATURES OF MOBILE WIMAX
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
KEY ADVANTAGES OF MOBILE WIMAX
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
SUMMARIZE
Mobile Wimax can be considered as a real competitor for 3G for example in
IP-traffic(VoIP/ IPTV).
Mobile Wimax supports seamless handoff which provides switching between
base stations in vehicular speeds.
Mobile Wimax uses Scalable OFDMA multiplexing which maximizes the
spectral efficiency.
IEEE 802.16e/Mobile WiMAX
Questions