Project: IEEE P Study Group for Wireless Personal Area Networks (WPANs(

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1 Project: IEEE P Study Group for Wireless Personal Area Networks (WPANs( WPANs) Title: Alternatives for Lower Frequency Band Extension Date Submitted: July 12, 2004 Source: Andreas Wolf, Dr. Wolf & Associates (DWA) and Hans van Leeuwen, STS-wireless Dr. Wolf & Associates GmbH Tel.: +49 (0) STS BV, The Netherlands Tel: , cell Re: Proposal and Discussion of equal higher data rates for PHY for 900/868 and 2400MHz bands Abstract: This document provides a discussion of alternatives for the extension of 2.4 GHz derivative modulation yielding higher data rates for the lower frequency band. Purpose: Increased data rate to reduce total system power and reduce marketing difference with 900/868/2400 Notice: This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P Slide 1

2 Alternatives for Lower Frequency Band Extension Andreas Wolf Dr. Wolf & Associates GmbH Hans van Leeuwen STS Slide 2

3 Presentation Contents Challenges for Low Band Alternatives PSSS Overview PSSS Linearity Requirements MP Fading and White Noise Coverage in Indoor Environments Summary Slide 3

4 TG4b Challenges Provide higher data rate in sub-1-ghz bands Minimum of 200 kbit/s Reduce power consumption Enable sufficient number of transactions/hr. in Europe Receiver sensitivity similar Extend practically achieved indoor range and coverage Increasing multipath fading robustness is required Derivative of 2.4 GHz modulation required Allow operation in US, EU and other regulatory regimes Provide backward compatibility to IEEE (868/915 MHz) Avoid additional hardware to achieve compatibility to maintain low complexity and implementation cost Required due to Revision PAR of IEEE TG4b 1: Canada, Russia, Korea Slide 4

5 New Specifications for the Low Bands We can expect new frequency bands specifications for the low ISM bands (868, 915 MHz) in Europe and Asia with increasing bandwidth in the future However, it will take years until the changed SRD band specifications form CEPT are adopted by all countries Therefore 3 modes of derivative modulations yielding higher data rates 1 are desirable: Higher rate in existing sub-ghz bands Ready for new, upcoming European MHz band Higher rate in 915 MHz band 1: Scope as defined in PAR Slide 5

6 Alternatives of Lower Band Extension Half Rate proposal PSSS I/Q PSSS BPSK/DSB Bitrate 125 kbit/s 250 kbit/s 500 kbit/s 225 kbit/s 450 kbit/s Bandwidth 2 Mhz at 915 Mhz 500 khz at 868 Mhz 1 Mhz at 900 Mhz 500 khz at 868 Mhz 1 Mhz at 915 Mhz Marketability US + few countries; Others only with regulatory change US, Europe, Asia (some) and US today US, Europe, Asia (some) and US today Coding backward compatibility Identical to existing 2.4GHz Derivative built of blocks that are similar to 2.4 Ghz Derivative 1 built of blocks that are similar to 2.4 Ghz Synchronization Clock recovery Required for BPSK and O-QPSK Required for BPSK and QAM Same as BPSK RF backward compatibility Other modulation, thus 2nd Tx+Rx core, sync, etc. Other modulation, thus 2nd Tx+Rx core, sync, etc. Same Rx and Tx; proposed solution is full derivative 1 1: Derivative of IEEE ; PSSS characteristics have been reviewed against PAR by TG4b, see also Anaheim minutes Slide 6

7 Link Budget Differences BPSK Low Band PSSS BPSK/DSB Band Data Rate Sensitivity Difference Data Rate Sensitivity Difference 868 Mhz 20 kbit/s 0 db 225 kbit/s -3 db 915 Mhz 40 kbit/s -3 db 450 kbit/s -6 db For a practical receiver the sensitivity will be better then -92 dbm Slide 7

8 PSSS 15 Codes 31 chip Code Words PSSS BPSK/ASK Tx Architecture Code Code 1 1 Code Code 2 2 Code Code 3 3 Code Code 4 4 Code Code 5 5 Code Code 6 6 Code Code 7 7 Code Code 8 8 Code Code 9 9 Code Code Code Code Code Code Code Code Code Code Code Code Low band 15 bit code Cyclic Extension Data Word Interoperable d 1 d 2 d 3 d 4 d 5 d 6 d 7 d 8 d 9 d 10 d 11 d 12 d 13 d 14 d 15 + Precoding 1 less then 300 gates 3 DAC 3 bit 1 Msamples/s 1 No additional gates on Rx side required Slide 8 Modulator PA C Class PA Design >10% non linearity acceptable ~ f 0 =868/915 MHz 3 bit resolution of PSSS symbol approx. 6 amplitude levels) 0.45 bit/s/hz [=15 codes/(31+2) symbol length], each second code and 2 chip cyclic extension] 1 Mchip/s (1MHz Bandwidth) for 900 MHz, 450 kbit/s data rate Backward compatible and interoperable to existing 15.4 low band phy Precoding Digital Analog

9 PSSS Receiver Architechture Pre-Select Filter LNA + LPF ADC Decoder FIR Filter 31 taps ection Carrier Synch (BPSK) ~ f 0 =868/915 MHz Chip Synch Threshold Det Digital Analog Slide 9

10 Simulation Model for Non Linearity 900/868 MHz PSSS Tx Non Linear Rx Correlator 1 Correlated Signal 1 Tx Signal Note: 1: 2 correlators and 2 correlated signals for Half Rate due to 2 different base codes used Slide 10

11 Transfer Function for Non Linear System 1,5 1 Saturation 0,5 0-1,0-0,8-0,6-0,4-0,2 0,0 0,2 0,4 0,6 0,8 1,0-0,5 f(x) f(x)+20% f(x)-20% f(x) Dead Zone f(x) Saturation -1 Dead Zone -1,5 Slide 11

12 PSSS Non Linearity 2% - Tx Signal Tx 2% Non Linearity Tx 0% Non Linearity Slide 12

13 PSSS Non Linearity 2% - Correlated Signal Correlated Signal 2% Non Linearity Detection Threshold Correlated Signal 0% Non Linearity Slide 13

14 Non Linearity 5% - Tx Signal Tx 5% Non Linearity Tx 0% Non Linearity Slide 14

15 Non Linearity 5% - Correlated Signal Correlated Signal 5% Non Linearity Detection Threshold (for 0 or 1 data bits) Correlated Signal 0% Non Linearity Slide 15

16 Non Linearity 10% - Tx Signal Tx 10% Non Linearity Tx 0% Non Linearity Slide 16

17 Non Linearity 10% - Correlated Signal Correlated Signal 10% Non Linearity Detection Threshold Correlated Signal 0% Non Linearity Slide 17

18 Non Linearity 20% - Tx Signal Tx 20% Non Linearity Tx 0% Non Linearity Slide 18

19 Non Linearity 20% - Correlated Signal Correlated Signal 20% Non Linearity Detection Threshold Correlated Signal 0% Non Linearity Note: PSSS in the configuration shown would tolerate for example up to 21 one-value chip errors per symbol without loss of data Slide 19

20 PSSS Conclusion on Linearity PSSS works even with 20% non linear PA PA and LNA designs are available off-the-shelf with No increase in chip cost even for linearity of 2% No additional power consumption compared to C class PA used in IEEE today No implementation risk due linearity required for PSSS! Slide 20

21 Simulation Model for MP Fading and Noise Tx Channel Rx Correlator 1 Correlated Signal 1 Tx Signal White Noise Note: 1: 2 correlators and 2 correlated signals for Half Rate due to 2 different base codes used Slide 21

22 PSSS at 1 Mchip/s with Multipath Fading Delay Spread 40ns and White Noise Correlated Signal Noise and Multipath Fading Detection Threshold Correlated Signal No noise Slide 22

23 Half Rate at 1 Mchip/s with Multipath Fading Delay Spread 400ns and White Noise Correlated Signal Noise and Multipath Fading Detection Threshold Correlated Signal No noise Slide 23

24 PSSS Conclusion on Multipath Fading and White Noise PSSS Strong robustness of PSSS against MP and noise Even for higher delay spreads 400ns and more Limit of 1µs for the selected coding Slide 24

25 Coverage Coverage is a good indicator for the range in 3D environments. Slide 25

26 PSSS Coverage Office 900 MHz Tx Limited due to Delay Spread 1µs for PSSS Tx No coverage limit due to multipath fading for PSSS because maximal delay spread is smaller then toleration limit of 1µs Slide 26

27 Summary The proposed parallel reuse of the 2.4 GHz modulation technology in PSSS offers highly attractive performance improvement increasing market opportunities Higher date rate and multiple channels possible in both current and upcoming European band (and certainly also in 915 MHz band) 15x higher spectral efficiency through PSSS compared to the current PHY for 868/915 MHz (8x higher over Half Rate proposal for new European band) Data rate or number of channels could be increased More efficient use of spectrum and resulting better coexistence Significantly stronger multipath fading robustness in PSSS Visibly higher range in many attractive, high volume target areas Very easy backward compatibility to the 2.4 GHz PHY, interoperable to existing Low Band PHY, also easy adaptation to current 868/915 MHz designs PSSS is derivative superset of current 2,4 GHz PHY technology Scalable data rate and automatic fallback to current standard possible Slide 27

28 Back Up Slides Transfer simulations are made with Simulink from Matlab Coverage Simulation are made with InSite Wireless form Remcom Influence of Noise and MP to Half Rate Transmission Coverage for Half Rate Slide 28

29 Half Rate at 1 Mchip/s with Multipath Fading Delay Spread 40ns and White Noise Correlated Signal Noise and Multipath Fading Detection Threshold Correlated Signal No noise Even this simple simulation is already clearly showing to reason for the known deficiencies in coverage and range under indoor MP fading conditions with IEEE (2.4 GHz) Slide 29

30 Half Rate Coverage Office 900 MHz, Delay Spread 40 ns Tx Coverage limit for Half Rate due to multi path fading 40 ns Slide 30

31 PSSS Coverage Office 900 MHz Limitation due Received Signal Strength Tx Coverage limit due to power Assumptions: 0 dbm Tx power -90 dbm Rx sensitivity (SNR 0 db) Slide 31

32 PSSS Conclusion on Multipath Fading and White Noise Half Rate High sensitive to 40 ns delay spread plus noise - Reducing visibly effective indoor range - Causing significant holes in coverage even in the reduced range PSSS Strong robustness of PSSS against MP and noise 1 Even for higher delay spreads 400ns and more Limit of 1µs for the selected coding Notes: 1 The same channels have been used in simulations of MP fading and noise for Half Rate and PSSS Slide 32