doc.: ieee 802.11-wng/1238r0 submission november 2010 alex reznik, tanbir haque (interdigital)slide...
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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 [email protected]
Tanbir Haque InterDigital 2 Huntington Quad, 4th floor – south wing Melville, NY 11747
(631) 622-4349 [email protected]
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