march 21, 2007, presentation to verizon motorola and the stylized m logo are registered in the us...

March 21, 2007, Presentation to Verizon

MOTOROLA and the Stylized M Logo are registered in the US Patent & Trademark Office. All other product or service names are the property of their respective owners. © Motorola, Inc. 2006.

11

Dynamic Range Increase for Working with high PAPR

IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number: IEEE S802.16m-08/159

Date Submitted: 2008-03-10

Source:Zeev Cohen E-mail: [email protected]

Doron Ezri Email: [email protected] Erlihson: Email: [email protected]

Venue:Orlando, US.This presentation follows the TGm call for contributions on Project 802.16m System Description Document (SDD) (802.16m-08/005), specifically, on the issue of Downlink Physical Resource Allocation Unit.

Base Contribution: nonePurpose:

To show that the PAPR problem coupled with OFDMA can be reduced or accommodated by various techniques and to conclude that OFDMA is the preferred transmission technology for 802.16m.

Notice:This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein.

Release:The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that

this contribution may be made public by IEEE 802.16.

Patent Policy:The contributor is familiar with the IEEE-SA Patent Policy and Procedures:

<http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and <http://standards.ieee.org/guides/opman/sect6.html#6.3>.Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and <http://standards.ieee.org/board/pat >.



22

The Problem: Transmitting Signals with High PAPR• To ensure high linearity transmission of signals with high PAPR (Peak

to Average Power Ratio), Power Amplifiers should cope with the problem of transmitting the peaks.

• The way RF Power Amplifiers are designed today is that for a given VCC the maximum RF power that can be transmitted with high linearity is aligned to the signal’s peaks (Dotted Red Line) and the average power that is transmitted is then reduced (backed off) approximately by the signal’s PAPR.

• Working with PA’s in high back-off means that the average power transmitted is much lower than the peak power that the PA can transmit and therefore the PA efficiency is reduced dramatically.



33

System solutions to overcome high PAPR

• Crest Factor Reduction

Pros: Reduces signal’s PAPR by 2-3 dB

Cons: Additional IP/Chip EVM performance degrades Mask performance degrades

• SLM – Selective Mapping

Pros: Reduces signal’s PAPR by 2-3 dB

Cons: System complexity. Side information transmission is required (reduces BW). Overall gain is not clear.



44

Increasing Power Amplifier’s Dynamic Range to overcome high PAPR

vD

iD

VDD

vg

Pin

Pout

Pmax

m=-1/ZL

A

VDD+vE

vE

Pmax,E

2

max

max,

DD

EDDE

V

VV

P

PDynamic Range Increase:



55

Increasing Power Amplifier’s Dynamic Range to overcome high PAPR

By partial envelope tracking we can change the VCC to the PA and raise

It when the signal’s peaks occur (Green line: signal envelope) to enable

them to be transmitted linearly (Blue Line).



66

Dynamic Range Increase: Performance Enhancements

• Output Power Increase:

20*Log (Vmax/Vnom)

• Efficiency Improvement:

Vmax/Vnom

• Same Linearity (EVM, Spectral Mask)



77

Dynamic Range Increase: Performance Results

Most PA’s tested provide more than 3dB Pout enhancement

No Dynamic Range

With Dynamic Range

0.00%

0.50%

1.00%

1.50%

2.00%

2.50%

3.00%

3.50%

4.00%

292827262524232221201918

Pout(dBm)

EVM(%)

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

Eff.(%)

2.3GHZ, EVM_w/XNN @3.4V

2.3GHZ, EVM_no/XNN @3.4V

2.345GHz, EVM_w/XNN @3.4V

2.345GHz,EVM_no/XNN @3.4V

2.39GHz, EVM_w/XNN @3.4V

2.39GHz, EVM_no/XNN @3.4V

2.3GHz Eff_w/XNN[%] @3.4V

2.3GHz, Eff_no/XNN[%] @3.4V

2.345GHz,Eff_w/XNN[%] @3.4V

2.345GHz,Eff_no/XNN[%] @3.4V

2.39GHz, Eff_w/XNN[%] @3.4V

2.39GHz, Eff_no/XNN[%] @3.4V



88

Dynamic Range Increase: Implementation Complexity

• Two Blocks are needed:

Envelope detector HW (sensing the RF) or

SW

Voltage Booster HW by 3 transistors and control

Capacitor of 1uF (for charge boosting)

• Full HW solution implemented in 0.18u cmos process in less than 2[mm^2]



99

• Dynamic Range Increase: Benefits

• Cops with signals with high PAPR

• Increased Linearity

• Higher Efficiency

• Prolong battery life

• Reduce PA current consumption

• Reduce heat dissipation

Better Power Amplifier Utilization!



1010

• Conclusions

• The high PAPR introduced by OFDMA transmission may be reduced or accommodated by various techniques.

• One of the most promising techniques is Dynamic Range Increase, which may be implemented with low complexity at the transmitter.

• This leads to the understanding that OFDMA is the preferred transmission technology for the 802.16m UL, which drawbacks may be mitigated fairly easily.

march 21, 2007, presentation to verizon motorola and the stylized m logo are registered in the us...

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