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Project: IEEE P802.15 WG for Wireless Personal Area Networks (WPANs)

Project: IEEE P802.15 WG for Wireless Personal Area Networks (WPANs) Submission Title: [Merged Proposal for FHSS to TG4g ] Date Submitted: [July , 2009 ]

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Project: IEEE P802.15 WG for Wireless Personal Area Networks (WPANs)

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  1. Project: IEEE P802.15 WG for Wireless Personal Area Networks (WPANs) Submission Title: [Merged Proposal for FHSS to TG4g] Date Submitted: [July, 2009] Source: [Bob Mason1, Rodney Hemminger1, John Buffington2, Daniel Popa2, Hartman VanWyk2, Fumihide Kojima3, Hiroshi Harada3, Henk de Ruijter4, Ping Xiong4, Péter Onódy4] Company [1Elster Electricity, 2Itron, 3NICT, 4Silicon Laboratories] Address:[ ] Voice: [ ]E-Mail: [ ]Re: [ Response to CFP issued January 22nd 2009, document 15-09-077-00-004g ]Abstract: [This document describes the Merged Proposal for FHSS to TG4g]Purpose: [ Proposal for consideration of inclusion into 802.15.4 PHY draft amendment ] 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. <Elster>, <Itron>, <NICT>, <Silicon Labs>

  2. Merged Proposal from 8 affiliated companies/organizations Objective of this work is to create a baseline FHSS system based on the best technical solution to meet the SUN requirements and plan for the future, without bias to existing systems. This is a MERGED PROPOSAL from the following authors, representing a combination of equipment suppliers and Silicon vendors. • Elster Electricity [09-302]: Bob Mason, Rodney Hemminger • Itron [09-292]: John Buffington, Daniel Popa, Hartman VanWyk • NICT [09-312]: Fumihide Kojima, Hiroshi Harada • Silicon Laboratories [09-278]: Henk de Ruijter, Ping Xiong, Péter Onódy The FHSS merged proposal is supported by: • Aclara: Kendall Smith, Mark Wilbur • Maxim: Rishi Mohindra • Roberto Aiello • TI: Khanh Tuan Le <Elster>, <Itron>, <NICT>, <Silicon Labs>

  3. Agenda • Requirements • Details about merged proposal • Band plan and channelization • System Parameters • Frame format: preamble, header, PSDU • TX/RX architecture • Performance results • Link budget • System performance in multi-path • Summary and conclusions <Elster>, <Itron>, <NICT>, <Silicon Labs>

  4. Requirements • The network must be comprised of robust, scalable network devices capable of today’s data requirements, but also capable of providing extended data capacity and response times for existing and future data requirements and device types. To meet these criteria, in addition to the items outlined in the PAR, the PHY must support the following: • Data rates to support basic devices (40-50kbps) but also data rates to support data intensive devices and applications (e.g. >300 kbps) • Ubiquitous network support for battery powered (i.e. gas and water) and line powered (i.e. electric) devices. All devices must interoperate. • Minimal infrastructure requirements (in many cases, nothing required except the utility devices) • Support for world-wide operation <Elster>, <Itron>, <NICT>, <Silicon Labs>

  5. Proposal DetailsMore details in 15-09-0491-00-004g <Elster>, <Itron>, <NICT>, <Silicon Labs>

  6. Key Points of Merged Proposal • Frequency Hopping Spread Spectrum • Three data rates* • Operating frequency range • 400MHz (Japan) • 868MHz (Europe) • 902-928MHz (US) • 950MHz (Japan) • 2,400MHz (Worldwide) • Other bands as available (including licensed bands) • 200kHz and 400kHz channels * Data rates and channel width vary slightly in different regions <Elster>, <Itron>, <NICT>, <Silicon Labs>

  7. System parameters * One will be selected, analysis still to be completed <Elster>, <Itron>, <NICT>, <Silicon Labs>

  8. Band plan – Channel Spacing * For systems using only the low data rate, 128 200kHz channels are available. For systems supporting mid and high data rates, all devices use 64 channels with 400 kHz spacing ** Pending regulatory approval <Elster>, <Itron>, <NICT>, <Silicon Labs>

  9. Japan operation:400MHz and 950 MHzDetails in document: 15-09-0478-00-004g <Elster>, <Itron>, <NICT>, <Silicon Labs>

  10. Europe operation <Elster>, <Itron>, <NICT>, <Silicon Labs>

  11. EU 868MHz Band (non-specific SRD) <Elster>, <Itron>, <NICT>, <Silicon Labs>

  12. Modulation parameters • GFSK BT = 0.5 • FHSS: 40kbps, h = 0.75 • AFA: • 100 kbps, h = 0.75 • 200 kbps, h = 0.3 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  13. Channel plan for Channel Hopping in Europe Note: Sub-bands for Alarm are excluded (gray frequencies) <Elster>, <Itron>, <NICT>, <Silicon Labs>

  14. AFA channel plan • Frequency Band: 863-870 MHz • Frequency sub-bands and allowed max output power: • 868.00-868.60 MHz (600 kHz): 25 mW / +14 dBm • 868.70-869.20 MHz (500 kHz): 25 mW / +14 dBm • 869.40-869.65 MHz (250 kHz): 500 mW / +27 dBm • Sub-band channel separation: 250 kHz • Number of channels: 5 • Channel center frequencies: • 868.175 MHz and 868.425 MHz • 868.825 MHz and 869.075 MHz • 869.525 MHz • Enable Adaptive Frequency Agility (AFA) with Listen-Before-Talk (LBT) <Elster>, <Itron>, <NICT>, <Silicon Labs>

  15. FHSS + AFA Hybrid for Europe • FHSS limits the data rate due to: • 100kHz channel limit (ETSI 300 220 V2.2.1) • Overhead associated with FHSS • When higher data rate is desired the MAC can set up a fixed wide band channel controlled under AFA. • For efficient FHSS we propose to skip LBT • LBT time of 5 ~ 10 ms per hop is not needed • Duty cycle restriction of 0.1% applies which seems sufficient for typical transfers. <Elster>, <Itron>, <NICT>, <Silicon Labs>

  16. Physical Layer Prococol Data UnitPHY-PDU (PPDU) <Elster>, <Itron>, <NICT>, <Silicon Labs>

  17. Proposed PPDU Structure • Proposed PPDU has the following fields • SHR composed of a basic SHRand some extensions • PHR: composed of a basic PHR and some extensions • PSDU & CRC • Proposed PPDU has a key feature • provides a flexible structure to support basic and extended modes <July 2009> SHR PHR MAC-PDU (MPDU) CRC Basic SHR SHRExtensions Basic PHR PHR Extensions MAC-PDU (MPDU) CRC Slide 17 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  18. PPDU Structure: Basic SHR and SHR extensions <July 2009> • Preamble • length set by phyNBFHPreambleLength • default phyNBFHPreambleValue)= 0x55 • Start of Frame Delimiter (SFD) • indicate whether there is a data rate change or not • 2 defined values : • 0xAA52 = No data rate change. • 0xAA2D = Data rate change prior to PHR Basic SHR SHR Extensions DRI ESHR Slide 18 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  19. <July 2009> PPDU Structure: Basic PHR & PHR extensions • RFU: • reserved for further use • Antenna Diversity: • An indication of the capabilities of the device. May allow change to preamble length to take advantage of antenna diversity • Enable/Disable DW: • Enable/disable data whitening for PSDU Basic PHR PHR Extensions Extension A Extension B Extension C Slide 19 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  20. <July 2009> Slide 20 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  21. <July 2009> PPDU Structure Reduced PPDU with Basic SHR and PHR • Basic SHR • SFD = 0xAA52 • Basic PHR • EXT =0 & NID = 0 & PSDU FEC = X & PHR FEC = 0 Slide 21 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  22. <July 2009> <July 2009> PPDU Structure PPDU with Basic SHR and full PHR extensions • When multiple optional fields are selected, order is as shown below Slide 22 Slide 22 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  23. Data Rate Changes <Elster>, <Itron>, <NICT>, <Silicon Labs>

  24. Data Rate Changes • When SFD indicates a data rate change, Data Rate Indicator field (DRI) is present. • DRI field parameters: • New Data Rate: Specifies new data rate as one of:Mid data rate = 0, High data rate = 1 • Settling Delay: Allows for transmitter and receiver settling prior to transmission of remainder of frame • Preamble2Len: Controls length of secondary synchronization preamble (0-7 octets) • SFD2 Present: Indicates whether a second SFD2 field is used for re-synchronization prior to the PHY Header <July 2009> Slide 24 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  25. Data Rate Changes DEFAULT DATA RATE NEW DATA RATE DRI field is the last field transmitted at the default data rate prior to the switch to the new data rate. Settling delay time (optional) is number of octets (0-3) at the default data rate <July 2009> <July 2009> Slide 25 Slide 25 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  26. Data Rate Changes • DRI field provides flexibility for: • Fast re-synchronization (no secondary re-synchronization fields) • Minimal re-synchronization (only SFD2 field) • Multiple options for full re-synchronization with settling delay and/or secondary preamble <July 2009> Slide 26 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  27. Data Rate Change Examples DEFAULT DATA RATE DEFAULT DATA RATE NEW DATA RATE NEW DATA RATE Fast re-synchronization <July 2009> <July 2009> • Minimal re-synchronization (SFD2 field present) Slide 27 Slide 27 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  28. Data Rate Change Examples DEFAULT DATA RATE NEW DATA RATE Re-synchronization with secondary preamble and secondary SFD <July 2009> <July 2009> Slide 28 Slide 28 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  29. Data Rate Change Examples Re-synchronization with settling delay, secondary preamble and secondary SFD <July 2009> <July 2009> DEFAULT DATA RATE NEW DATA RATE Slide 29 Slide 29 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  30. 32-bit CRC • CRC-32K (Koopman) • Polynomial x32+x30+x29+x28+x26+x20+x19+x17+x16+x15+x11+x10+x7+x6+x4+x2+x+1 (0xBA0DC66B) • Advantages • Hamming distance >= 6 up to 16Kbit message length • Traditional CRC-32 only offers HD >=6 up to 268 bits, HD = 5 up to 2974 bits and HD = 4 up to 91607 bits. • CRC-32K yields two additional bits of error detection for 1500 octet message lengths [1] • CRC-32K advantage in the 269-16360 bit (34 to 2045 octet) length range aligns with PAR requirement for minimum 1500 octet payloads [1] Koopman, P. "32-Bit Cyclic Redundancy Codes for Internet Applications," Int'l Conf. on Dependable Systems and Networks, 2002. <July 2009> Slide 30 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  31. Optional FEC Algorithm • Reed Solomon (RS) coding for PSDU: • Proposed coding is a RS(38,28) code. It is a shortened version of a RS(255,245) code with symbols in Galois Field - GF(256). This code has a Hamming distance of 11 and allows the correction of multiple erroneous bytes per block. • Reed Solomon (RS) coding for PHR: • Proposed coding is a RS(xx,yy) code. Coding scheme TBD based on final PHR definition • Aligns with present sensor network research: • BCH codes outperform energy efficiency of best convolutional codes by 15%. [1] • SEC/DED (single error correction, double error detection) BCH yields significant improvement in packet drop rate (outdoor: 0.22% to near 0; indoor: 2.32% to 1.19%). [2] • Significant benefits in multi-hop mesh networks. [3] [1] Sankarasubramaniam, Y. et al. "Energy efficiency based packet size optimization in wireless sensor networks," Proc. IEEE Int'l Workshop on Sensor Network Protocols and Applications, pp. 1-8, 2003. [2] Jeong, J. and Ee, C. "Forward Error Correction in Sensor Networks," Int'l Workshop on Wireless Sensor Networks, June 2007. [3] Vuran, M. and Akyildiz, I. "Cross-Layer Analysis of Error Control in Wireless Sensor Networks," 3rd IEEE Communications Society Conf. on Sensor, Mesh and Ad Hoc Communications and Networks, September 2006. <July 2009> Slide 31 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  32. Optional Data Whitening • Enabled by default; can be disabled with extended PHY header • Seed value based on channel number – no PHR overhead required • 8-bit additive scrambler, using LFSR with feedback polynomial x8 + x6 + x5 + x4 + 1 • Yields maximum length sequence (28 - 1) <July 2009> Slide 32 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  33. “PHY header processing” Data whitening/ scrambling (optional) PSDU FEC (optional) Generate PHR Preamble insertion Compute CRC-32 FEC for PHY header (optional) RF MOD MAC-PDU FEC (optional) De-scrambling (optional) Data Detection Synch FEC for PHY header (optional) Compute CRC-32 RFDMOD TX/ RX architecture “PHY header processing” <Elster>, <Itron>, <NICT>, <Silicon Labs>

  34. System performance <Elster>, <Itron>, <NICT>, <Silicon Labs>

  35. Link budget <Elster>, <Itron>, <NICT>, <Silicon Labs>

  36. Practical considerations • Low data rate presents advantages in real implementations • Receiver bandwidth is often considered as the main parameter to improve receiver sensitivity • Other factors are also important when analyzing PHY performance • ISI is a function of symbol rate • Frequency error tolerance (see backup slides) • Immunity to narrowband interference (see backup slides) • Synthesizer phase noise (see backup slides) • Dispersive fading (see backup slides) <Elster>, <Itron>, <NICT>, <Silicon Labs>

  37. Multipath Fading and Data Rate • Fixed (non-time variant) fading characterized by mean delay spread (average value of the delayed signal components) • Mean delay spread will vary based on environment, typical values are as follows: Source: Lee, William C.Y., “Mobile Communications Design Fundamentals”, John Wiley & Sons, Inc, 1993 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  38. Multipath Fading and Data Rate • For minimal ISI, the symbol rate (Rb) should be less than 10% of the mean delay spread. In other words: Rb < 0.1 * Δ 1 • Using the above rule, and the mean delay spreads for various environments, the recommended baud rates for each environment can be calculated: <July 2009> 1Source: Lee, William C.Y., “Mobile Communications Design Fundamentals”, John Wiley & Sons, Inc, 1993, p38-41. Slide 38 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  39. Multipath Fading and Data Rate • The variability in mean delay spreads based on environment presents a strong argument for: • 3 data rates to minimize multipath fading effects • 4 level modulation to achieve higher data rates without reducing system throughput and reliability <July 2009> Slide 39 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  40. Conclusions Merged proposal • Low data rate* mandatory: 40-50kbps • Medium/ high data rates* optional: 160/320kbps • GFSK • 400kHz channel spacing * Data rates vary slightly in different regions Other proposals • 100kbps • FSK • 250kHz channel • 300kHz channel spacing • Advantages of merged proposal • Lower adjacent channel emission for local regulations • Worldwide operation • Proven technology for meter reading and FHSS systems • Higher data rates for data intensive devices and applications • Low and high data rate devices interoperable <Elster>, <Itron>, <NICT>, <Silicon Labs>

  41. Backup <Elster>, <Itron>, <NICT>, <Silicon Labs>

  42. Japan band: 400MHz • Japan allocation for the 15.4g on 400MHz: • About 1MHz-system-bandwidth out of 400.0MHz~430.0MHz band is under consideration that accommodates 4~5 of 200kHz spacing carriers • Japan allocation for the conventional specified low power radio: • 426.0250 and 426.1375 MHz, 1mW (0dBm) • 429.1750 and 429.7375 MHz, 10mW (+10dBm) • 429.8125 and 429.9250 MHz, 10mW (+10dBm) • 449.7125 and 449.8875 MHz, 10mW (+10dBm) • 469.4375 and 469.4875 MHz, 10mW (+10dBm) <July 2009> 42 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  43. Japan band: 950MHz • Japan allocation • 950.9-955.7MHz <July 2009> 43 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  44. Constrains FHSS in “g” Band • Sub-bands for alarms are excluded: • Max channel spacing = 100kHz • Minimum number of channels = 47 • Maximum emission at sub-band edges is -36dBm in 100kHz • Max duty cycle = 0.1% (maybe higher when LBT is used) • NOTE: The duty cycle applies to the entire transmission (not at each hopping channel). • Max dwell time per channel = 400 ms • The maximum return time to a hopping channel shall be equal or less than the product of 4 x dwell and the number of hopping channels and must not exceed 20 s. • Each channel of the hopping sequence shall be occupied at least once during a period not exceeding the product of 4 x dwell time and the number of hopping channels. • In case of LBT being used for FHSS, this function shall be used at each hop channel. Slide 44 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  45. Power Spectral Density2-GFSK, BT = 0.5, 160 kbps <July 2009> • Trace 4 (Green) • Mod Index = 0.75 • 20 dB BW = 192 kHz 192 kHz Slide 45 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  46. Spectral Density4-GFSK, BT = 0.5, 320 kbps <July 2009> • Freq Separation = 80 kHz (-120,-80,+80,+120) • 20 dB BW = 373 kHz Slide 46 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  47. Comparison of Modulation Index Numbers for FSK • Wider signal bandwidth used by higher modulation index offers the following advantages where sufficient channel bandwidth is available : • Greater frequency error tolerance • Greater immunity to narrowband interferers • Improved performance in presence of synthesizer phase noise • Potentially better performance under dispersive (frequency dependent) fading conditions <July 2009> Slide 47 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  48. Comparison of Modulation Index Numbers for FSK • Greater Frequency Error Tolerance • To guarantee capture under sensitivity threshold conditions, the RX IF bandwidth must be as wide as the TX signal bandwidth plus the relative frequency error between the transmitter and receiver. • For narrowband FSK, the frequency error may be a significant percentage of the total RX IF bandwidth, resulting in a S/N penalty given by: S/N Penalty (dB) = 10*LOG10(TX BW/RX IF BW) = 10*LOG10[TX BW/(TX BW + Ferror)] where Ferror = relative frequency error between the transmitter and receiver <July 2009> Slide 48 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  49. Greater Frequency Tolerance • Calculated S/N penalties for various modulation index numbers with following assumptions: • Baud rate (Rb) = 40 ksps • Relative frequency error between Tx and Rx = 50 ppm (25 ppm each device) • Nominal center Frequency = 915 MHz • GFSK TX BW ~= 2*dev + 0.68*Rb <July 2009> Slide 49 <Elster>, <Itron>, <NICT>, <Silicon Labs>

  50. Comparison of Modulation Index Numbers for FSK • Greater immunity to narrowband interferers • For narrowband interference in the RX IF BW, a wider FSK BW offers better immunity as the interfering signal affects a smaller percentage of the desired signal bandwidth • Relative immunity for FSK signals as a function of BW can be approximated by: Relative Immunity (dB) = 10*LOG10(TX BW1/TX BW2) <July 2009> Slide 50 <Elster>, <Itron>, <NICT>, <Silicon Labs>

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