Scalable ofdma3 802.16e

802.16e – Mobile WiMAX

Mikko Kivistö - mikko.kivisto(at)tut.fiPetri Järvelä – petri.jarvela(at)tut.fi

Introduction

802.16e provides enhancements to 802.16-2004 to support subscriber stations moving at vehicular speedsstandard 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-InterferenceScalable Channel BandwidthOrthogonal Uplink Multiple AccessSupport for Spectrally-Efficient TDDFrequency-Selective SchedulingFractional Frequency ReuseFine Quality of Service (QoS)Advanced Antenna Technology

Overview

Certification ProcessFrequency BandsReference Model

Certification Process

In December, 2005 the IEEE ratified the 802.16e amendment to the 802.16 standard.First certification laboratory was established in CetecomLabs in Malaga, Spain in the same yearIEEE has moved it´s responsibility of WiMAXcertifications to WiMAX ForumFirst commercial availability for 802.16e in 7/2006More advanced mobile functionality will gradually beadded through support for high-speed handoffs, roamingand multiple antenna technologies such as MIMO and beamforming and be available in equipment in the secondhalf 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 NetworkCSN = Connctivity Service NetworkNSP = Network Service ProviderASP = Application Service ProviderNAP = 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 andservice 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 802.16etechnology 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 enablethe 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 operationSleep ModeIdle Mode

Idle Modeprovides a mechanism for the MS to become periodically availableremove the requirement for handoff and other normal operationseliminate 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 methodsHard Handoff , HHO (mandatory)Fast Base Station Switching , FBSS (optional)Macro Diversity Handover , MDHO (optional)

When FBSS is supportedMS and BS keep up a list of BSs that are involved in FBSS with the MS → Active setMS defines an Anchor BS and communicates only withit.

When FBSS is supportedtransition between Anchor BSs is carried out without anyHO signallingbegins 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 supportedMS and BS maintain an active set of BSs that are involvedin MDHO with the MS.An Anchor BS is definedMS communicates with all BSs in the active set of uplinkand downlink unicast messages and trafficbegins when a MS decides to transmit or receive unicastmessages and trafficfrom multiple BSs in the same time interval

Smart antenna technologies typically involve complexvector or matrix operations on signals due to multipleantennas. OFDMA allows smart antenna operations to be performed on vector-flat sub-carriers.

Mobile WiMAX supports a full range of smartantenna technologies to enhance system performance.

Advanced Features of MobileWiMAX

Advanced Features of MobileWiMAX

Beamforming→ better coverage and capacity

and→ reduce outage probability

Space-Time Code (STC)transmit diversity codes are used to provide spatialdiversity→ reduce fade margin

Spatial Multiplexing (SM)

→ advantage of higher peak rates

→ increases throughputmultiple streams are transmitted over multiple antennasboth receiver and transmitter must have multiple antennas to achieve higher throughput

Advanced Features of MobileWiMAX

Advanced Features of MobileWiMAX

Fractional Frequency Reuseall cells/sectors operate on the same frequency channel to maximize spectral efficiency.users operate on subchannels, which only occupy a smallfraction of the whole channel bandwidththe flexible sub-channel reuse is facilitated by sub-channelsegmentation and permutation zone

Multicast and Broadcast Service (MBS)combines the best features of DVB-H, MediaFLO and 3GPPE-UTRA and satisfies the following requirements:

High data rate and coverage using a Single Frequency Network (SFN)Flexible allocation of radio resourcesLow MS power consumptionSupport of data-casting in addition to audio and video streamsLow channel switching time

Advanced Features of MobileWiMAX

802.16e System Parameters

Comparing Mobile WiMAX to 1xEVDO and HSPA

Summary

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

References

Mobile WiMAX – Part I: A Technical Overview and PerformanceEvaluation, Aug. 2006, Copyright 2006 WiMAX ForumMobile WiMAX – Part II: A Comparative Analysis, May 2006, Copyright 2006 WiMAX Forum802.16e-2005 Standard, LAN/MAN Standards Committee of IEEE Computer SocietyFixed, nomadic, portable and mobile applications for 802.16-2004 and 802.16e WiMAX networks, Nov. 2005, Prepared by Senza FiliConsulting on behalf of the WIMAX ForumMobile WiMAX Performance and Comparative Summary, Sep2006, Copyright 2006 WiMAX Forum