Create Presentation
Download Presentation

Download

Download Presentation

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ The ParthusCeva Ult

241 Views
Download Presentation

Download Presentation
## Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ The ParthusCeva Ult

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -

**Project: IEEE P802.15 Working Group for Wireless Personal**Area Networks (WPANs) Submission Title: [The ParthusCeva Ultra Wideband PHY proposal] Date Submitted: [05 May, 2003] Source: [Michael Mc Laughlin, Vincent Ashe] Company [ParthusCeva Inc.] Address [32-34 Harcourt Street, Dublin 2, Ireland.] Voice:[+353-1-402-5809], FAX: [-], E-Mail:[michael.mclaughlin@parthusceva.com] Re: [IEEE P802.15 Alternate PHY Call For Proposals. 17 Jan 2003] Abstract: [Proposal for a 802.15.3a PHY] Purpose: [To allow the Task Group to evaluate the PHY proposed] Notice: This document has been prepared to assist the IEEE P802.15. 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 P802.15. Michael Mc Laughlin, ParthusCeva**The ParthusCeva PHYProposal**Michael Mc Laughlin, ParthusCeva**Overview of Presentation**• Coding • DSSS Coding scheme - biorthogonal coding • Ternary spreading codes • Reed Solomon FEC code • Optionally concatenated with convolutional code • Preamble • Implementation Overview • Performance • Link margin • Test results • Throughput, Multiple piconet performance • Complexity Michael Mc Laughlin, ParthusCeva**Symbol coding**• 64 biorthogonal signals [Proakis1] • 64 signals from 32 orthogonal sequences • Ternary sequences chosen for their auto-correlation properties • Code constructed from binary Golay-Hadamard sequences Michael Mc Laughlin, ParthusCeva**Spreading code comparison**• Length 32 code chosen for aamf and best matching with bit rates. Michael Mc Laughlin, ParthusCeva**Sample rate and pulse repetition frequency**• Signal bandwidth chosen is 3.85GHz to 7.7GHz • Sampling rate chosen is 7.7Ghz • 32 chips per codeword, 6 channel bits / symbol Michael Mc Laughlin, ParthusCeva**FEC Scheme**• Concatenated code for 110 , 220Mbps, 880Mbps • Reed Solomon outer code (235,255) • Convolutional rate 4/6 inner code • Reed Solomon code (43,63) for 490Mbps, 980Mbps Michael Mc Laughlin, ParthusCeva**FEC scheme - inner code**• A 0.667 rate (rate 4/6) convolutional code was chosen for the inner code at 110 and 200 Mbps. [Proakis2] • Very low complexity 16 state code, constraint length 2, Octal generators 27, 75, 72. • Each of 16 states can transition to any other state, outputting 16 of 64 possible codewords. • Provides 3dB of gain over uncoded errors at a cost of 50% higher bit rate Michael Mc Laughlin, ParthusCeva**Preamble Sequence**Michael Mc Laughlin, ParthusCeva**PAC properties**• Because of the perfect autocorrelation property, the channel impulse response can be obtained in the receiver by correlating with the sequence and averaging the results. • Because the sequence consists of mostly 1, -1 with a small number of zeros, correlation can be economically implemented. (a length 553 PAC has 24 0’s) Michael Mc Laughlin, ParthusCeva**Preamble properties**• Very good detect rate and false alarm probability. Pfa and Pmd < 10-4 for CM1 to CM4 test suite at 10 metres. Detected in 2s using matched filter architecture. • Matched filter is equivalent of 553 parallel correlators • Different length sequences means other piconets won’t trigger detection i.e. Pfa still < 10-3 for a different piconets PACn, even at 0.3m separation. • Preamble length varies from ~5s to ~15s depending on the bit rate. Lower bit rates use longer preambles (Longer distances need more training time) Michael Mc Laughlin, ParthusCeva**PHY Header**• The PHY header is sent at an uncoded 45Mbps rate, but with no convolutional coding. It is repeated 3 times. • The PHY header contents are the same as 802.15.3 i.e. Two octets with the Data rate, number of payload bits and scrambler seed. Michael Mc Laughlin, ParthusCeva**Scrambler/Descrambler**• It is proposed that the PHY uses the same scrambler and descrambler as used by IEEE 802.15.3 Michael Mc Laughlin, ParthusCeva**Typical Tx/Rx configuration**Antenna Single Chip Possible Output data at 55 - 960 Mbps Channel Matched filter (Rake Receiver) Fine/ Band Reject Filter Band Pass Filter* A/D 7.7GHz, 1 bit Viterbi Decoder Correlator Bank Switch / Hybrid LNA Descramble 8-240M symbols/sec 256 - 3800 Mchips/sec Input data at 55- 960 Mbps Band Pass Filter Chip to Pulse Generator Code Generator Band Reject Filter Convolutional encoder Scramble * Can be avoided with good LNA dynamic range Michael Mc Laughlin, ParthusCeva**Filter**Possible RF front end configuration • Total Noise Figure = 6.6dB NF= 0.3dB (input referred) NF= 2.0dB NF= 3.5dB Fine Filter** BP Filter* LNA To Rx NF= 0.8dB Tx/Rx switch / hybrid Band reject Filter ** From Tx ** Depending on Local National or User requirements * Can be avoided with good LNA dynamic range Michael Mc Laughlin, ParthusCeva**Matched Filter configuration**Cn 4 1 Di Cn+N Di-N Cn+1 4 1 Di-1 Di-N-1 Cn+N+1 ….. ….. 4x 4x 4x 4x 4 4 4 4 ….. 4 bit adder 4x 4x + 5 bit adder + ….. ….. Michael Mc Laughlin, ParthusCeva**Matched Filter configuration**• Structure repeated 16 times e.g. a 500 tap filter with 4 bit coefficients would have 500 x 16 x 4 AND gates in first stage • Calculates 16 outputs in parallel, each runs at (480/mps) MHz. • e.g. 120MHz for 220Mbps • Multiplier is 4 AND gates. • First adder stage is 4 OR gates. Very little performance loss. (0dB for CM1-3, 0.23dB for CM4). • Coefficients are pre-processed to remove smallest if two clash. • mps is max pulses/sample. = 1440/(channel bit rate (Mbps)) Michael Mc Laughlin, ParthusCeva**Matched filter**• 560 tap filter takes 135k gates or 0.82 sq mm in 0.13 standard cell CMOS • Worst case power consumption = 120mW ( at 490Mbps ), proportional to data rate. Much lower for CM1 because of fewer taps. • Matched filter re-used for correlation with training sequence during training phase • All simulations were carried out with this filter/correlator structure Michael Mc Laughlin, ParthusCeva**Distance achieved for mean packet error rate of best 90% =**8% Michael Mc Laughlin, ParthusCeva**Distance achieved for at worst packet error rate of best 90%**= 8% Michael Mc Laughlin, ParthusCeva**110 Mbps average PER**Michael Mc Laughlin, ParthusCeva**220 Mbps average PER**Michael Mc Laughlin, ParthusCeva**490 Mbps average PER**Michael Mc Laughlin, ParthusCeva**Multiple Piconet Interferers**• Tests were done according to the Multiple Piconet interference procedure outlined in the latest revision of the selection criteria (03031r11). • The distance to the receiver under test was set at 0.707 of the 90% link success probability distance. • Tests results were obtained for 1,2 and 3 interfering piconets Michael Mc Laughlin, ParthusCeva**Single adjacent piconet**Michael Mc Laughlin, ParthusCeva**Two adjacent piconets**Michael Mc Laughlin, ParthusCeva**Three adjacent piconets**Michael Mc Laughlin, ParthusCeva**Co-channel interference**• Different piconets use exactly the same data mode codes as each other. • Separation is achieved because • a) a different piconet will have a different impulse response and thus will not correlate with the matched filter which has been trained for the piconet of interest. • b) Codes won’t be synchronised • Co-channel data mode interference is exactly the same as adjacent channel interference. • Training to the preamble will be affected more markedly by co-channel interference. Difficult to simulate. Michael Mc Laughlin, ParthusCeva**Co existence**• Out of band signals, e.g. 802.11b, (< 3.1GHz and >10.6GHz) are always filtered out. • Any desired in band energy can be filtered out, with minimal effect on performance because the whole band is used to transfer data. • Only adverse effect is the transmit power reduction (e.g. Dropping 400MHz for 802.11a loses <0.5dB) Michael Mc Laughlin, ParthusCeva**Co-existence with 802.11a**• Filtering out the UNII band spectrum from the transmitter has very little effect on the performance • The receive matched filter will cope with it automatically • Only 1.25dB of power is lost by filtering out the Tx signal from 5GHz to6GHz • This is the equivalent of a 15% loss in distance Michael Mc Laughlin, ParthusCeva**Interference and susceptibility**• As for co existence, out of band signal, e.g. 802.11b, are always filtered out. • Again, any desired in band energy can be filtered out, with minimal effect on performance because the whole band is used to transfer data. • Only adverse effect is the receive power reduction (e.g. Dropping 400MHz for 802.11a loses <0.5dB), its just a part of the channel. Michael Mc Laughlin, ParthusCeva**Narrowband interference**• Immunity to narrowband interference • With no filtering • Processing a gain of e.g. ~24dBs at 110Mbps. Any interfering tone is reduced by this amount. • With digital notch filter • Tones can be detected at the A/D output. • A simple notch filter either at the input or output of the matched filter can then remove this completely with no loss in performance (if notch is narrow enough) Michael Mc Laughlin, ParthusCeva**PHY-SAP Data Throughput**• At higher bit rates, a 1024 byte frame is very short. • The channel will be stationery for more than one frame so it is possible to send multiple frames for each preamble. • T_MIFS=1μs, T_SIFS=5μs, T_PHYHDR=1.1μs,T_HCS=0.29μs, T_MACHDR=1.45μs Michael Mc Laughlin, ParthusCeva**Scalable solution**• 55 - 980 Mbps. Gate count depends on maximum bit rate and power consumption of baseband PHY is proportional to bit rate. • 880Mbps has 90% link success on CM1-CM3 at over 3.4m, 2.8m and 2.6m with exactly same RF and sample rate as the other rates • Receiver here uses 3.85 - 7.7GHz. • 2.5dB extra performance gain if full band used. • 1.0dB lower performance if 3.2-4.8 GHz band used with ~50% power reduction Michael Mc Laughlin, ParthusCeva**Complexity - Area/Gate count, Power consumption**• These figure are for a standard cell library implementation in 0.13µm CMOS Michael Mc Laughlin, ParthusCeva**How can it be so good?**• Where does this large Performance/Cost/Power advantage come from • Compare with two proposals other proposals - TFI OFDM and Multiband • These two were chosen because of their prominence and fairly comprehensive results available Michael Mc Laughlin, ParthusCeva**Performance- How much better?**• All similar under AWGN, i.e. 20 odd metres at 110Mbps. • 200/220/240 Mbps • ~50% farther than either TFI-OFDM or Multiband over CM1 • 92% farther than TI-OFDM and 230% farther than Multiband over CM4 • 110/120 Mbps • 22/25% farther over CM1 • 22% farther than TFI-OFDM and 75% farther than Multiband over CM4 • 480 Mbps -86% fartherthan TFI-OFDM over CM1, no CM4 or Multiband figures available. • NB: The distances quoted for TFI-OFDM and Multiband do not take into account the 4.7dB loss required for FCC compliance i.e. a further 1.72 gain factor. Michael Mc Laughlin, ParthusCeva**Performance - Why is it better?**• Gap is small with no multipath at low rates, larger as the multipath increases and speed increases. • Multiband approach only gathers a small amount of multipath energy. 16ns at 120Mbps and 8ns at 240Mbps. CM4 channels have significant energy spread over 100ns • ParthusCeva PHY - has equivalent of a 230 finger rake. • Ternary codes were chosen for their multipath immunity Michael Mc Laughlin, ParthusCeva**Power**• 110/120Mbps Rx @ 0.13 • This approach up to 145mW • Multiband approach 170-200mW • TFI - OFDM 205mW • Why so good? • Simple analog Rx section • Single bit ADC • No AGC • No mixer • No FFT in the receiver. Matched filter with 1 bit inputs. Low complexity decoders Michael Mc Laughlin, ParthusCeva**Cost**• Comparison at 0.13µ • This approach 4.25mm2 • Multiband approach 7.3mm2 • TFI - OFDM approach 6.9mm2 • Why the difference ? • Same reasons as power, low complexity digital and analog requirements Michael Mc Laughlin, ParthusCeva**Summary of advantages**• Ternary spreading codes • Better auto-correlation properties • Perfect PAC training sequence • Simple RF section • 1 bit A/D converter • No AGC required • No Rx mixers required • Long rake possible - near multipath immunity • 4 bit coefficients • 1 bit data • no multipliers • Cost and Power very similar to Bluetooth } Low cost Low power consumption Low Noise figure Michael Mc Laughlin, ParthusCeva**The ParthusCeva PHY**Faster Michael Mc Laughlin, ParthusCeva**The ParthusCeva PHY**Faster Smaller Michael Mc Laughlin, ParthusCeva**The ParthusCeva PHY**Faster Smaller Cooler Michael Mc Laughlin, ParthusCeva**Backup Slides**Michael Mc Laughlin, ParthusCeva**Self evaluation : General Criteria**Michael Mc Laughlin, ParthusCeva**Self evaluation : PHY protocol**Michael Mc Laughlin, ParthusCeva**Self evaluation : MAC enhancements**Michael Mc Laughlin, ParthusCeva**Ternary orthogonal sequences**• From any base set of 32 orthogonal binary signals, can generate 32C16 sets of 32 orthogonal ternary sequences. • Generate by adding and subtracting any 16 pairs. • Generally, if the base set has good correlation properties, so will a generated set. Michael Mc Laughlin, ParthusCeva