Behind Mobile WiMAX

Chenxi Zhu, Ph.D.

Fujitsu Labs of AmericaCollege Park, MD

Email: czhu@ieee.org

What is mobile WiMAX?

Mobile broadband wireless accessDefined by IEEE and WiMAX Forum.

IEEE 802.16e_2005: wireless MAN-OFDMAPHY and MAC layer.

WiMAX Forum: System profiles, testing, networking protocols, applications, certification, etc.Marketing and promotion.

Mobile WiMAX network

TDD or FDD spectrum 802.16e air interface:

• OFDMA-based PHY,• QoS-oriented MAC

Mobile IP-basedNetworking layer

Cellulardeployment

Core Network

Radio Access Network

OFDMA PHY layerQoS oriented MAC layerMobile IP-based networking layerFuture of WiMAX

OFDM PHY layer

Frequency domain signaling.ICI-free: orthogonal between subcarriers.ISI-free: guard interval between symbols.Robust against multiple paths.

No equalization required at receiver.

Time domain Frequency domain

OFDMA: OFDM for multiple access

User 1

User 2

User 3

User 4

Base station assigns the subcarriers to users in DL and UL.Radio resources (subcarriers, transmission powers) are allocated based on user channel quality and BW requirement (QoS).

Scalable PHY layer TDD or FDD, variable frame length (2—20 ms). Different FFT sizes (128, 512, 1024, 2048) for variable BW (1.25MHz--20MHz).Variable CP length (1/32,1/16,1/8,1/4) for different cell size.Same inter-subcarrier spacing (97.2KHz).Multi-modes supported with a single SoC.Adaptive modulation and coding.

QPSK, 16QAM, 64QAM.CC, CTC, BTC, LDPC (1/2, 2/3, ¾, 5/6).

Beamforming and MIMO.Common or dedicated pilots.HARQ (Chase, IR).

Different subchannelization for different mobility.

Diversity permutation(PUSC, FUSC)

Contiguous permutation(AMC)

TDD Frame structure

Preamble: power boosted for BS identification and synchronization.Control channel (FCH, DL-MAP, UL-MAP): assign

subchannels to users, power level, modulation/coding.DL/UL Burst: data packets BS MS.

Multiple antennas (MIMO)

Close loop transmitter beamforming.Space time code (Alamouti scheme).Spatial multiplexing.Up link: virtual MIMO.

IFFT

IFFT

IFFT

IFFT

FFT

FFT

FFT

FFT

MIM

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MIM

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MIM

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MIM

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-map

ping

OFDMA PHY layerQoS oriented MAC layerMobile IP-based networking layerFuture of WiMAX

QoS support by connection-oriented scheduled MAC

ServiceFlow overQoSconnection

WiMAX QoS classes

Maximum Rate, Traffic PriorityData Transfer, Web browsing

BE(Best Effort Service)

Minimum Rate, Maximum Rate, Traffic Priority

FTPNRT-VR(Non-Real-Time Variable Rate)

Minimum Rate, Maximum Rate, Maximum Delay, Jitter Tolerance, Traffic Priority

VoIP with Activity Detection

ERT-VR(Extended Real-Time Variable Rate service)

Minimum Rate, Maximum Rate, Maximum Delay, Traffic Priority

Streaming Audio or Video

RT-VR(Real-Time Variable Rate service)

Maximum Rate, Maximum DelayJitter Tolerance

VoIPUGS (CBR)(Unsolicited Grant Service)

QoS SpecificationsApplicationsQoS Category

OFDMA PHY layerQoS oriented MAC layerMIP-based networking layer

defined by WiMAX Forum NWG

Future of WiMAX

Mobile IP-based network architecture

MIP FA

OFDMA PHY layerQoS oriented MAC layerMobile IP-based networking layerFuture of WiMAX

Current development of 802.16

802.16j: multi-hop relayEnhance coverage and capacity of 802.16e with relay stations.

802.16m: targeting IMT-AdvancedSupport BW ≥ 20MHz. Backward compactable with 802.16e. 100 Mbps at high mobility.1 Gbps for fixed user.

Industry synergySystem vendors

Samsung, Motorola, Alcatel-Lucent, Nortel,Nokia-Siemens, Huawei, ZTE, …

Chip manufacturesIntel, Fujitsu, Runcom, Beecem, …

Device manufacturesNokia, Samsung, Motorola, Sony-Ericsson,…

Service providersSprint, AT&T, Nextwave, SK-Telecom, KDDI, French-telecom, Telecom-Italia, DirectTV, ….

Content providerDisney

Roadmap to market

Who may deploy WiMAX?Fixed point-to-point (LOS): 802.16d-OFDM

Wireless backhaulFixed point-to-multipoint (NLOS): 802.16d/e-OFDM/OFDMA

DSL/cable replacementCCTV

Nomadic data application (Laptop, Handhold): OFDM/OFDMABetter coverage than WiFi Hotspot

Mobile data, data/voice (OFDMA)4G?

Intelligent transportation system (OFDMA)Transportation infrastructureVehicle to curb

World wide WiMAX trials

Further information

www.wimaxforum.orgwww.wimaxtrends.comGoogle!

Backup slides

Scalable OFDMA PHY layer

4 FFT sizes (128, 512, 1024, 2048) for variableBandwidth.

AdaptiveModulationand codingfor differentchannel quality

802.16e Subcarrier allocation

Pilot sub-carrier for channel estimation.Data sub-carrier for data transmission.No transmission in Null sub-carriers (DC, guard-band).

Air Interface Protocol Stack