Next Generation Wireless Communication System

All right reserved. Copyright ©2011- Yoshikazu Miyanaga

Next Generation Wireless Communication System

- Cognitive System and High Speed Wireless -

Yoshikazu MiyanagaDistinguished Lecturer, IEEE Circuits and Systems Society

Hokkaido UniversityLaboratory of Information Communication Networks

Graduate School of Information Science and TechnologySapporo 060-0814, Hokkaido Japan


Key Technologies

OFDM (Orthogonal Frequency Division Multiplexing)Wireless LAN

54MBPS (IEEE 802.11a, .11g)300MBPS – 600MBPS (IEEE 802.11n)

Digital TV broadcastingWiMAXNext Generation Mobile Phone

3G LTE (super 3G, - 2010 in JP), 4G ( - 2015 in JP)

MIMO (Multiple Input Multiple Output Communication Channels )Wireless LAN

300MBPS – 600MBPS (IEEE 802.11n)Over 1GBPS (IEEE802.11ac)

Advanced WiMAXNext Generation Mobile Phone

2


Basic OFDM System

Input Data

Output Data

Mapping

S/P

IFFT

channel

Dem

apping

P/S

Delete G

I

S/P

FFT

Equalizer

P/S

D/A

Guard Interval

A/D


Basic OFDM System

Input Data

Output Data

Mapping

S/P

IFFT

channel

Dem

apping

P/S

Delete G

I

S/P

FFT

Equalizer

P/S

D/A

Guard Interval

A/D

Coder:cov, blk

De-Coder:Viterbi,LDPC

512 – 1024 p FFT within several nanosecond

512 – 1024 p FFT within several nanosecond

Low Power Design


MIMO System

Transmitter

Receiver

Mapper

Mapper

IFFT

IFFTTX

Encoder

Encoder

FFT

FFT

MIM

O

Detector

De-Mapper

De-MapperRX

Decoder

Decoder


MIMO Decoding Circuit

The mode when the receiver gets the training symbolsThe estimation of channel and the inverse matrix calculation should be completed.

The mode when the receiver gets data symbolsMIMO decoding should be applied.

from FFT ΒA,

H

(from 1st and 2nd training symbols)

G

1−Η=G

y s

Channel Estimation

Inverse Matrix Memory

MIMO Detector


MIMO Decoding Circuit

from FFT ΒA,

H

(from 1st and 2nd training symbols)

G

1−Η=G

y s

Channel Estimation

Inverse Matrix Memory

MIMO Detector

Matrix Inversionwithin several nanosecond

Low Power Design

High speed & Low power ….


Low Power Consumption Design

Smaller number of GatesSwitching power reductionLeak current reduction

Parallel/Pipelined CalculationLower Clock Rate

Power ControlGated clockDynamic Power Suspension of Module Block

8


and MORE …

Lower Voltage Input SupplySub-threshold designDynamic voltage control

New Algorithm DesignLower calculation costComplete Parallel/Pipelined Processing

New Architecture DesignDynamic Architecture

9


COGNITIVE RADIO SYSTEM FOR THE NEXT GENERATION WIRELESS NETWORK


WHAT IS COGNITIVE RADIO ?!?

In 2000, FCC introduced a “Cognitive Radio System” which used efficiently frequency bands.

In 2005, IEEE 802 Committee introduced an advance system, i.e., a cognitive radio system, in which an occupied frequency band is automatically selected and dynamically changed.


Conventional Radio Mode

All available frequency bands are fixed. Accordingly, the frequency band possibly used for the system has been assigned as a prior information.

ch1 for system A

ch2 for system B

ch3 for system C

Freq.ch1 ch2 ch3

A B C

A

A

B

C

C

time : t1

time : t2

time : t3

time : t4 B

FCC reports over 80% bands are not used at the specific location and time.


Cognitive Radio Mode

ch1 for system A

ch2 for system B

ch3 for system C

Freq.ch1 ch2 ch3

A B C

A

A

B C

C

time : t1

time : t2

time : t3

time : t4 B

C

C

• The system finds out the available bands and then select some of suitable bands dynamically by itself.

System C is a cognitive radio.

System A and B are conventional radio.


Cognitive Radio Mode

• It changes the frequency bandwidths depending on communication environment.

The resources of frequency bands are fully and optimally used.

• It has many communication modes.The high throughput is usually kept.

• The complexity of a system becomes high compared to a fixed radio system.

High power-consumption and circuit size become considerably large.


Our cognitive system

Our design of new cognitive system is based on MIMO-OFDM system.

All parts of our system behaves as cognitive systems !!!

15


Cognitive MIMO-OFDM

RF8x4 MIMO

.11a OFDM 2x2 MIMO

450M VHT OFDM

4x4 MIMO

4x2 MIMO300M OFDM

MAC

.11n OFDM

Con Sensor Processor


Cognitive MIMO-OFDM

RF アンテナ8x4 MIMO

.11a OFDM 2x2 MIMO

1.8G New OFDM

4x4 MIMO

4x2 MIMOCognitive OFDM

MAC

.11n OFDM


Intelligent Sensor is designed. A sensor tries to find out the information of current communication environment.

450M New OFDM

The AI controller determines the optimum communication mode with suitable parameters in which lowest BER/PER can be designed. From its decision, a specific mode and a suitable band are selected automatically.


Cognitive MIMO-OFDM

RF

.11a OFDM 2x2 MIMO

450M VHT OFDM

4x4 MIMO

4x2 MIMO300M OFDM

MAC

.11n OFDM


8x4 MIMO


Cognitive MIMO-OFDM

RF

.11a OFDM 2x2 MIMO

450M VHT OFDM

4x4 MIMO

4x2 MIMO300M OFDM

MAC

.11n OFDM


8x4 MIMO

Cognitive MIMO-OFDM is designed. Its features are given as follows

•20～100MHz band is determined dynamically.•Minimum PER can be achieved.•The optimum throughput is selected among 54M～1.8Gbps.


Modes in Cognitive MIMO-OFDM

HU-VHT


Number of Butterfly Blocks

HU-VHT


Required data paths for all FFTs

Array of Butterfly blocks


Evaluation

Hardware description language

Verilog HDL

Logic synthesis Design AnalyzerClock frequency 100MHz

technology 90nmCMOS


Evaluation(consumption power)

75.8HU-VHT 2x2 MIMO

48.0802.11n 2x3 MIMO

802.11n 4x4 MIMO

IEEE802.16eSISO

802.11n SISO

System

24.338.163.440.7

16.1

Conventional（mW）

512128

256512102464

128

FFT length

76.148.5

24.538.263.841.3

16.2

Proposed（mW）

802.11a/n SISO 10.3128 10.4

“Conventional” means each power consumption is given from a corresponding sub-module only. It does not means the power consumption of the total system.


Evaluation(circuit area)

Conventional ProposedNo. of gates

Area 1.79 1.16

51096.5 × 51087.3 ×

Proposed structure can reduce a circuit scale by about 35%.


HIGH SPEED WIRELESS COMMUNICATION

26


Current Trend of MIMO-OFDM SystemsIEEE802.11 Standards

Development by Hokkaido Univ.(Only Baseband)

IEEE802.11a (2002) 54Mbps

IEEE802.11n Draft (2007) 300Mbps

IEEE802.11n Optional (2009) 600Mbps

IEEE802.11ac[2012] 3.0 Gbps Hokkaido Univ.

4x4 MIMO-OFDM (2008) 1.5 Gbps

Hokkaido Univ. 2x2 MIMO-OFDM (2006) 600 Mbps

Hokkaido Univ. SISO-OFDM

(2005) 300 Mbps

Hokkaido Univ. 8x8 MIMO-OFDM

(2010) 3.0 Gbps

Tran

smit

Spee

d

Bandwidth20MHz 40MHz 60MHz 80MHz

500Mbps

1Gbps

2Gbps

3Gbps


Xilinx・Gigabit Ethernet MAC・STARC MAC

Altera・STARC PHY

Output

Gigabit Ethernet PHY

FPGA Board for Evaluation


Dynamic Architecture of Low Power

OFDM BBTransmitter

OFDM BBReceiver

OFDM BBTransmitter

OFDM BBReceiver

Sensor SensorMonitering

Realization of High Throughput and Low Power


Block Diagram of 4x4 MIMO-OFDM Circuit

Transmitter

Scrambler Encoder Mapper Pilot Insertion

IFFT Re-order & GI Insertion

Preamble Insertion

Interleave& Puncture

Receiver

Frame & Freq. Synchronization

FFT Re-order & Pilot Remove

MIMO Channel Est. & Decoding

Demapper Viterbi Decoding

De-scramblerDe-interleave & Dummy Data

Insertion


Matrix Operations

Use of 2x2 SubmatricesConjugate Symmetry in Non Diagonal Submatrices

11P

21P12P 13P

22P

33P 34P

43P 44P

14P

24P 23P

31P 32P

42P41PConjugate Symmetry

Hermitian Transpose

IHHP 2kk

Hkk σ+=

⎟⎟⎠

⎞⎜⎜⎝

⎛=⎟⎟

⎠

⎞⎜⎜⎝

⎛=

DBBA

DCBA

H

Complexity ReductionStrassen’s Matrix Multiplication and InversionUse of Conjugate Symmetry Submatrices


Performance Comparison

Reference [2] [3] [4] ProposedMatrix 2 x 2 4 x 4 4 x 4 4 x 4

Detection Algorithm ZF ZF MMSE MMSE

Hardware Configuration

DSPTMS3206713

ASIC 90 nm43 k gates

ASIC 0.25 µm89 k gates

ASIC 90 nm1.86 M gates

Operating Freq. 225 MHz 500 MHz 167 MHz 160 MHz

Latency Time 104 x K (µs) 180 x K (ns) 600 x K (ns) 187.5 (ns)

K: No. of OFDM Subcarriers

[2] V. Jungnickel, A. Forck, T. Haustein, et al., “1 Gbit/s MIMO-OFDM transmission experiments,'' IEEE Vehicular Technology Conference (VTC), 2005.

[3] Johan Eilert, Di Wu, and Dake Liu, “Efficient complex matrix inversion for MIMO software defined radio,” IEEE ISCAS, 2007.

[4] A. Burg, S. Haene, D. Perels, P. Luethi, N. Felber, and W. Fichtner, “Algorithm and VLSI architecture for linear MMSE detection in MIMO-OFDM systems,” IEEE ISCAS, 2006.


Available Data Speed

Necessary ConditionsClock Frequency ≥ Baseband BandwidthProcessing Latency ≤ GI Duration (400 ns)

Bandwidth (MHz)

Max

imum

Tra

nsm

issi

on S

peed

(M

bps)

A 2.6-Gbps MIMO-OFDM receiver is available by the proposed MMSE detector.

5/6 Coding Rate

64-QAM

400-ns GI Duration


4x4 MIMO-OFDM with 512 SUBCARRIERS


Design Challenge of 8x8 MIMO-OFDM

Task group of IEEE802.11ac mentions use of more than four antennas.

The maximum number of spatial streams is eight.

8x8 MIMO-OFDM1.2 Gbps at 40-MHz Channel3.0 Gbps at 80-MHz Channel6.0 Gbps at 160-MHz Channel (Use of two transceivers)

High Speed and Low-Power Architecture for 8x8 MIMO-OFDM


Current Activities in Our Project

Total design of 8x8 MIMO-OFDM transceiverIntegrated design for multiple data streamsReal-time processing for MIMO detectionLow power design by intelligent power control

Prototype fabrication of wireless systemIntegration of baseband, RF, antenna units


Block Diagram

Scrambler Encoder Interleave & Puncture

Pilot Insertion

IFFT Re-order & GI Insertion

Preamble Insertion

Mapper

Viterbi Decoding

Frame & Freq .Synchronization

FFT

Re-order & Pilot Remove

MIMO Channel Est. &Decoding

Demapper

De-interleave & Dummy Data Insertion

De-Scrambler

Transmitter

Receiver

Blocks in FFT/IFFT, Viterbi decoding, MIMO decoding are dominant in circuit scale.


Integrated DesignDuplicate design

Deploy identical circuit blocks for the number of spatial data streamsIncrease power and area in proportion to spatial data streams

Integrated designA circuit block supports multiple-input and multiple-output data paths.Reduce power and area by resource sharing

FFT

FFT

FFT

FFT

FFT

FFT

MIMO FFT

SISO FFT processorsMIMO FFT processor


Multi-Path Delay FFT ProcessorR8MDC (Radix-8 multiple path delay communicator)

Based on 8-input and 8-output butterfly unitsReduction of multipliers by FFT radix-8 algorithm

A 8x8 MIMO FFT processor only needs 1/3 circuit area compared with eight SISO FFT processors.


Implementation of 8x8 MIMO-OFDMCircuit performance (100MHz clock, w/o MIMO decoding)

Transmitter

Receiver

No. of logic gates Power Dissipation (mW)

IFFT 573,400 91.2

Interleave* 104,000 15.0

Pilot assignment* 219,000 32.2

Others* 348,500 47.3

Total 1,244,900 185.7

No. of logic gates Power Dissipation (mW)

FFT 573,700 117.0

Synchronization 24,900 2.8

Channel Estimation 19,600 1.7

Viterbi decoding 2,724,300 251.6

Deinterleave* 677,200 73.4

Others* 219,500 33.4

Total 4,239,200 479.9

* memory buffer included


MIMO Detection

Strassen’s algorithmSystematic matrix operation based on 2x2 matricesExtension of square matrix operations

8x8 matrix inversion

8

8


4x4 matrix multiplication


2x2 matrix multiplication

Division of submatrices in matrix inversion


Timing ChartReceived signals in frequency domain after FFT

Preprocessing (matrix inversion)

)()()( ttt kkkk nsHy +=

Hkkk

Hkk HIHHG 12 )( −+= σ

MIMO decoding)()(ˆ tt kkk yGs =

k: OFDM subcarrier index

t: OFDM symbol index


Implementation of MIMO Detector8x8 MIMO detection can complete within guard interval (800 ns) duration.

Complete real-time processing in MIMO detection, which is tolerant of time varying fading.

8x8 FullPipeline

4x4 Full Pipeline*

Wordlength (bits) 26 20

Operating Frequency 80MHz 160MHz

Total cell area (μm2) 61,570,100 8,813,200

Number of logic gates 15,392,500 2,203,300

Processing Latency 780 ns 190 ns

Power Consumption 1.42 W 701.2mW

*Shingo Yoshizawa, Yasushi Yamauchi, Yoshikazu Miyanaga, ``VLSI Implementation of a Complete Pipeline MMSE Detector for a 4x4 MIMO-OFDM Receiver,'' IEICE Transactions on Fundamentals, Vol.E91-A, No.7, pp.1757-1762, July 2008.


Prototype FabricationWireless transceiver

2x2 MIMO-OFDM transmitter and receiverFPGA baseband unitsRF transceiver (5150 - 5250 MHz frequency band)*

*Shingo Yoshizawa, Shinya Odagiri, Yasuhiro Asai, Takashi Gunji, Takashi Saito, Yoshikazu Miyanaga,``Development and Outdoor Evaluation of an Experimental Platform in an 80-MHz Bandwidth 2x2 MIMO-OFDM System at 5.2-GHz Band,''IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), Sep. 2010.


FPGA Board2x2 MIMO-OFDM Transceiver

400 M samples/s by 4x over samplingMMSE and MLD algorithms in MIMO detection


Summary

New Trend of Wireless CommunicationsMIMO-OFDM

802.16 WiMAX3G LTE (super 3G, - 2010 in JP), 4G (- 2015 in JP)

LTE : Long Term Evolution

802.11ac ( over 1GBPS wireless LAN)

Cognitive Wireless SystemUltra High Speed Wireless System

4x4 MIMO-OFDM8x8 MIMO-OFDM

46


Who ?

47

Yoshikazu MiyanagaHe is a professor in Graduate School of Information Science and Technology, Hokkaido University. He is an associate editor of Journal of Signal Processing, RISP Japan (2005-present). He was a chair of Technical Group on Smart Info-Media System, IEICE(IEICE TG-SIS) (2004-2006) and now a member of the advisorycommittee, IEICE TG-SIS (2006-present). He is also vice-President,IEICE Engineering Science (ES) Society. He is a fellow member ofIEICE. He is also vice-President, Asia-Pacific Signal and Information Processing Association (APSIPA). He is a distinguished lecture (DL) of IEEE CAS Society (2010-2011) and now a Board of Governor (BoG) of IEEE CAS Society (2011-present).

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Next Generation Wireless Communication System