Forums

PAPR vs Input Back-off in LTE

Started by nbtech 4 weeks ago2 replieslatest reply 3 weeks ago73 views

Hello -

OFDM based LTE signals show a very high PAPR of around 12dB. This would require an IBO (input back off) for the High Power Amplifier (HPA) of atleast 12dB to operate in linear region. But the efficiency of HPA would be significantly reduced. 

Can anybody provide some info/guidance/links what are the typical IBO values in LTE for multicarrier transmissions like OFDM? How much PAPR reduction can be achieved?

Thank you



[ - ]
Reply by fharrisJuly 14, 2021

There are many ways to reduce PAPR in OFDM... SC-OFDM, which makes the cell links asymmetrical was invented to obtain reduced PAPR at the mobile.

The reserve bin option by cioffei was added to 802.11 to obtain reduced PAPR


the Magic Wand papers by richard van nee did an amazing job reducing PAPR using complementary Code Keying

see two attached papers 

sdr_2004_paper_2.pdf

SDR-04.ppt


fred h

[ - ]
Reply by kazJuly 15, 2021

For Downlink we used to do an inhouse fancy method of peak reduction and achieved PAR of 7.xx dB on lte having PAR of 12 dB or so (FPGA platform). Followed by Digital PreDistortion(DPD).

The method was about measuring peaks over a time window and then reducing all signal values proportional to amplitude using a filter approach on the stream of peaks. This was done in three iterations while keeping an eye on spectrum shoulders due to nonlinear distortion and phase discontinuity caused by this reduction. In terms of resource it was the most expensive and slowest part of design. It was designed as preprocessor for DPD algorithm.