doc.: IEEE 802.11-wng/1238r0

Submission

November 2010

Alex Reznik, Tanbir Haque (InterDigital)Slide 1

Digital RF Transceiver To Meet Needs of Emerging Spectrum

Date: 2010-11-09

Name Affiliations Address Phone email Alex Reznik InterDigital 781 Third Ave.,

King of Prussia, PA 19406

(610) 878-5784 Alex.reznik@interdigital.com

Tanbir Haque InterDigital 2 Huntington Quad, 4th floor – south wing Melville, NY 11747

(631) 622-4349 Tanbir.Haque@Interdigital.com

Authors:

doc.: IEEE 802.11-wng/1238r0

Submission Slide 2

Abstract• We outline a design approach for a digital RF

Transceiver

• The design is aimed at addressing many of the problems associated with radio operation in TVWS and other sub-1 GHz frequencies

• We believe these developments to be of interest to 802.11 as it considers potential multichannel operation and new spectra below 1 GHz

November 2010

Alex Reznik, Tanbir Haque (InterDigital)

doc.: IEEE 802.11-wng/1238r0

Submission

Motivation• The expanding scope of 802.11

– New spectrum: sub-1GHz (including TV bands), 60GHz, 3.6 GHz– MAC enhancements: 802.11ac– New regulatory environments (TV bands)

• This brings about new challenges– Can a single chipset address multiple spectra efficiently?– Can a reasonable implementation support operation over non-contiguous bands?

• 802.11 is structured to successfully address many of these challenges– Common MAC supporting multiple PHYs– Closely related PHY definitions– All these enable efficient single chipset implementations of MAC/PHYs over multiple spectra

• However, RF remains a challenge– Multiple analog solutions requires to address multiple bands– Aggregation of discontinuous spectrum remains a major challenge– Operation at low frequencies (TVWS and other sub-1 GHZ) requires truly “wideband” radios

• Digital RF technology can address these challenges– The idea is not new– But it is finally ready for prime-time

November 2010

Alex Reznik, Tanbir Haque (InterDigital)Slide 3

doc.: IEEE 802.11-wng/1238r0

Submission

Digital RF: Motivation and GoalsNovember 2010

Alex Reznik, Tanbir Haque (InterDigital)Slide 4

Evolving & emerging standards are pushing baseband (modem) logic gate count, memory and clock speed requirements ever higher

At the same time, proliferation of multi-band and multi-radio devices require access (often simultaneous) to an ever-growing range of spectrum

To achieve performance (speed) and reduce cost (die size) baseband chip designs will migrate into scaled IC process technologies.

Analog radio designs do not scale easily and have emerged as a major barrier to the evolution of multi-mode devices

Next generation radio architectures will employ digital logic building blocks to implement RF functions

The goal is to develop highly flexible “Digital” transceiver technology suitable for monolithic integration with the modem on scaled CMOS process technologies

0.2

0.3

0.4

0.5

0.6

0.7

0.8

1.5 2 2.5 3 3.5

130nm CMOS

90nm CMOS

65nm CMOS

45nm CMOS

BW improvement relative to 0.18um CMOS process

Volta

ge s

win

g re

duct

ion

rel

ativ

e to

0.

18um

CM

OS

pro

cess

Relative Output Swing

Relative BW

doc.: IEEE 802.11-wng/1238r0

Submission

Why Digital? Technology BenefitsNovember 2010

Alex Reznik, Tanbir Haque (InterDigital)Slide 5

Simplified supply chain Lower complexity device design Shorter time to market Reduced cost & size Non-contiguous BW aggregation Stringent spectral mask requirements

in emerging spectra (e.g. TVWS) Broadband sensing, fast frequency

scanning Variable & narrow duplex spacing

FDD Increased downlink waveform

complexity Increased uplink waveform PAR

Implements RF functions on digital logic blocks monolithic integration with modem possible reduces number of components in UE reference design

RF waveform agnostic transceiver chain single chain supports multiple PHY/spectra

Inductor-less design reduced overall die size/cost Efficient wide band TX/RX chains commercially viable BW

aggregation (contiguous & non-contiguous) Wide band TX/RX chains single free running oscillator

used superior phase noise performance possible Employs digital up/down conversion & channelization

superior EVM performance possible Employs adaptive hardware resource management

algorithms reduces overall power consumption High SNDR TX chain delivers better than -55dBc ACLR Constant envelope transmit signal use of efficient switch-

mode PA possible

Summary of radio technology needs & challenges

DTRX features that address needs

doc.: IEEE 802.11-wng/1238r0

Submission

Digital Transmitter Concept

November 2010

Alex Reznik, Tanbir Haque (InterDigital)Slide 6

• Cartesian digital transmitter converts the multi-bit inputs into a high speed single bit output stream

• The signal is formed in Cartesian format as [i, q,-i,-q] – the RF waveform is recovered by filtering

Multi-bit

Multi-bit

Adaptive HW Resource Management Algorithms

t

I

Q

Gain control &

C

hannelization Logic

Lowpass Sigma-Delta Modulator

Lowpass Sigma-Delta Modulator

On-chip C

MO

S switch m

ode low

power PA

1-bit Digital IQ

Modulator

65nm CMOS 2.61x2.64mm^2 65nm CMOS

2.28x2.28mm^2TX BB ASIC TX RFIC

doc.: IEEE 802.11-wng/1238r0

Submission

Going Digital in the TX: Sigma Delta Modulation

November 2010

Alex Reznik, Tanbir Haque (InterDigital)Slide 7

4th order, 1.5-bit sigma-delta modulator for TVWS low band

Programmable all-digital sigma-delta modulator technology– Response is programmed by writing appropriate coefficients stored in memory– Power optimized design supplies improved coding efficiency for better overall TX efficiency– Noise optimized design supplies better noise free bandwidth to relax bandpass filter requirements

4th order, 1.5-bit sigma-delta modulator for TVWS high band

Better than 65dB SNR available to support -55dBc ACLR required for TVWS operation

doc.: IEEE 802.11-wng/1238r0

Submission

Aggregating Multiple Bands for TX

• Digital design approach leads to simple “aggregation” of spectra

• Simultaneous transmission over multiple non-adjacent channels is possible while preserving efficiency & spectrum mask performance

• Example: TV Band Tx Channel Capabilities of Existing prototype– Waveform may be 5, 10, 15 or 20 MHz OFDM

– 4x6 MHz channels: – Contiguous or non-contiguous

– 2x12 MHz channels:– Contiguous or non-contiguous

– 1x24 MHz channel:

– Time alignment between channels < 1uSec

– Better than -55dBc ACLR performance supports TVWS spectral mask requirements

– 50% < sigma-delta coding efficiency < 75%

November 2010

Alex Reznik, Tanbir Haque (InterDigital)Slide 8

doc.: IEEE 802.11-wng/1238r0

Submission

Going Digital in the RX: Banked ADCsNovember 2010

Alex Reznik, Tanbir Haque (InterDigital)Slide 9

ADC

LNA

ADCADC

ADCADC

ADCADC

ADC

InputD

igital Signal

Processing Unit

Clock and power management unit

Modem

t Multiple ADC’s sample the input signal on different phases of the clock

High-rate sampling (115 Msps per ADC, 1840 Msps aggregate) for direct-to-digital conversion

Signal processing unit assembles the input signal and sends it to modem Enables use of power-efficient small non-instrumentation grade ADCs

Clock and power management helps to reduce the overall power consumption

doc.: IEEE 802.11-wng/1238r0

Submission

Aggregating Multiple Bands for RX• As with digital TX, simultaneous reception of multiple bands

is possible for continuous of discontinuous spectra– Commercially viable BW aggregation

• Example: Existing prototype supports simultaneous reception of OFDM waveform with BW of 5, 10 or 20 MHz in TV Spectrum– 4x6 MHz channels & 2x12 MHz channels

• Contiguous or non-contiguous

– 1x24 MHz channel

– EVM < 2%

– Maximum power difference between Rx channels: 40 dB

– Time alignment between Rx channels < 1 uSec

– 5 db Noise Figure with LNA

November 2010

Alex Reznik, Tanbir Haque (InterDigital)Slide 10

doc.: IEEE 802.11-wng/1238r0

Submission

Near Term Design TargetsNovember 2010

Alex Reznik, Tanbir Haque (InterDigital)Slide 11

Single chip transceiver solution 40nm CMOS process Programmable solution supports

LTE bands 1, 3, 4, 6, 7, 9, 10, 11, 17 WCDMA bands I, II, III, IV, V, VI, VIII, IX, X, XI TVWS bands 512MHz ~ 698MHz

Chip (die) size < 10mm^2 ADC Performance Numbers

12 HW bits (9 ENOB) Max single rate = 200 Msps Max agg.rate (x16) = 3200 Msps

RX EVM < 2% RX SNDR > 50dB RX noise figure < 6dB 80mW* < RX power < 180mW*

*determined by operating conditions

Key Features RX Performance Targets

TX EVM < 2% TX ACLR better than -55dBc Peak output power ~ +17dBm Transmitter power consumption < 150mW SD modulator coding efficiency > 50% Switch mode PA peak efficiency > 50%

TX Performance Targets

doc.: IEEE 802.11-wng/1238r0

Submission

Digital Radio SummaryNovember 2010

Alex Reznik, Tanbir Haque (InterDigital)Slide 12

Overcomes the limitations suffered by analog solutions Delivers higher bandwidth in a commercially viable manner Delivers better performance (EVM, SNR) Suitable for and leverages the benefits of smaller CMOS process nodes

Lower cost (size and power) radio solution possible Monolithic integration of modem and digital radio is possible – this reduces the

overall size and cost Scalable transceiver design and adaptive power management algorithms reduce

overall power consumption

Enables broadening of possibilities for 802.11 Wide band digital radio makes BW aggregation commercially viable Waveform agnostic, re-configurable digital radio eases the incorporation of new

bands and standards Superior TX spectral mask performance suitable for TVWS operation