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

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ TG4g Common Platform Proposal (CPP) Update ] Date Submitted: [ September 2009 ] Source: [ Cristina Seibert ] Company [ SilverSpring Networks] Address [ 555 Broadway Street, Redwood City, CA 94063] Voice [ 650 780-4514 ] E-Mail:[ cseibert@silverspringnet.com ] Re: [ TG4g Proposal ] Abstract: An update to the Common Platform Proposal for TG4g Purpose: Proposal Update 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.

TG4g Common Platform Proposal (CPP) September 2009

Members January 20 Slide 3

Latest Developments • PHY parameter harmonization • Consistent data rates and modulation parameters across bands • Retains support for difficult regulatory domains • Comprehensive validation • Modulation parameters • Coding for header and payload protection • Link margin analysis

Outline • CPP Goals and Highlights • Global Regulatory Landscape • CPP Modulation Parameters • Detailed Technical Proposal • PHY Parameters • FEC • Packet Formatting • Data Rate Management • Precursor System Support • Performance Simulations • Conclusions

Proposal Goals and Highlights

CPP Goals • Strong technical proposal • Elegant and global, common PHY • Accommodate regional spectrum limitations • Substantial flexibility for growth and future needs

CPP Highlights • Generalization of 802.15.4d • Meets regulatory constraints in all applicable frequency bands • Extends performance to SUN requirements • Global application support • Globally common base data rate of 100 kbps • Proven performance • Validated analytically • Real world results • Accommodates bandwidth constrained regions • Scalability for future needs • Optional data rates of 200 kbps and 400 kbps • Sufficient extensibility features provide future-proofing

CPP Framework January 20 • Global regulatory landscape • Globalization of existing 802.15.4 FSK PHY • Modulation parameters • Consistent, simple, flexible, and easily implemented • PHY parameter details • Chosen for optimal SUN performance • PPDU details • Simple, powerful mechanism for extensibility • PHY Mode and Data Rate Management • Conforming to OSI layering principles • Precursor system support • Existing deployments supported with minimal modification Slide 9

Overview of Bands January 20 Band Table 1 Band Table 2 Slide 11

Regional Spectrum Aspects • Japan • 1 MHz in 400-430 band expected to become available • No spread spectrum, no hopping required • Channels can be provisioned for optimal performance • China • 40 MHz in 470-510, 200kHz channel spacing • Optional 400kHz channel for higher data rate (channel bonding) • Configurable boundary for channel hopping • Europe • Some channels require ≤ 100 kHz widths • Portions of band to be used in contiguous 250 kHz width • US • 26 MHz of spectrum available at 902 band • 80+ MHz at 2.4 GHz • Coverage impact due to higher carrier frequencies • Licensed spectrum with high roll-off requirements

US Narrow Band Regulations Part 90: 896-901 MHz Part 24: 901-902 MHz Part 101: 928-960 MHz h=0.5 h=1.0 • A GFSK signal with h=0.5 and BT=0.5 fits the spectral mask

US Narrow Band Regulations 25 kHz Channel 50 kHz Channel h=0.5 h=1 h=0.5 h=1 • A GFSK signal with h=0.5 and BT=0.5 fits the spectral mask

European Band Overview

European Band Overview (Cont) • Out of band emissions of < -36 dBm per 100 kHz from the band edge • h < 0.5 is required to meet requirement with 250 kHz channels • Small guard bands and a larger mod. index can be used in the 863-868 MHz band

Modulation and Channel Parameters Note: BT of 0.5 used with GFSK *baseline rate

Parameters for narrow channels January 20 Note: BT of 0.5 used with GFSK * number of available channels can vary Slide 19

Interoperability • FSK and GFSK are compatible • All geographically localized parameters are consistent and interoperable

Data Rate Options • Data rates selected to meet consensus goals • 100 kbps in all applicable bands globally • Also supports 50 kbps, 200 kbps, 400 kbps • Where regulations limit channel bandwidth, CPP supports low data rates

Network Performance Collision profile is highly dependent upon: number of channels available – collision avoidance data rate – on-air time Number of nodes within interference range Number of channels, and number of visible nodes are dictated by the deployment Performance is optimized by choosing data rate that balances SNR performance and network collisions Network Collision Profile 1.0 100 chan 100kbps 40kbps 0.8 10 chan 0.6 probability of success 100kbps 0.4 0.2 100kbps 40kbps 1 chan 40kbps 0.0 0 100 200 300 400 500 number of nodes January 20 Slide 23

January 20 100kbps across bands in all regions • Collision probability reduced compared to lower data rates in interference limited environment • Link margin more than sufficient in actual deployments • Same applications supported in all bands • Enables seamless inter-band hopping Slide 24

PHY Modulation Options GFSK and FSK have their own strengths GFSK and the choice of BT can help reduce adjacent channel emissions However, it can also increase ISI which results in partial closing of the eye diagram For simple demodulators this results in a degradation of performance compared to FSK BT=0.5 ~ 2dB BT=0.3 can be significantly worse

PHY Modulation Options (Cont’d) BT=0.5 represents a good compromise of spectral control vs. performance MSK increases performance where adjacent channel requirements allow Best to include both as interoperable choices to support all applications

Channel Spacing Options • Supports channel spacing optimized for regional regulatory constraints • Requirements differ: • Channel spacing of 200 kHz • Fits 5 channels in 1 MHz • GFSK achieves -20 dBc adjacent channel attenuation • Channel spacing of 250 kHz • Fits 5 channels in European band - 868 MHz to 869.7 MHz • GFSK achieves -30 dBc adjacent channel attenuation • Channel spacing of 300 kHz • For longer range MSK operation; still permits good adjacent channel attenuation • Suggested in US 902 MHz and 2.4 GHz bands • Leverage band agnostic approach • There are good reasons for each and there is no additional transceiver complexity deriving from multiple channel spacing options

Bands with Narrow Channels • Portions of the European band and some class license bands require narrow channels (tens of kHz to 100 kHz) • Complex regulations in 863-870 MHz spectrum • 863-868 MHz has narrow spacing/BW requiring 802.15.4g support • CPP parameters are optimized to enable regulatory compliance for narrower channels • Lower data rates (e.g. 5,10,20, 40kbps) are supported at no added complexity – no need to exclude narrow channel applications from 802.15.4g

Coding Architecture

Coding Choice • To balance payload and header we use • ½ rate convolutional coding on payload • BCH(48,24) on the header • Convolutional coding on payload • Sensitivity gain • Ability to leverage soft decisions • For header, BCH code is a pragmatic choice because it has several other advantages • Systematic code • Ease of implementation • Byte alignment

LDPC Coding • Also under consideration • LDPC codes can offer considerable coding gain • It can be made flexible in terms of coding rate, block size • However, coding gain needs to be covered by a sufficiently strong synchronization header

PHY Packet Format January 20 Octet Bits • Configurable preamble • Support for variable preamble length and pattern • Optional scrambler seed • Robust data recovery w/o constraints on upper layers • SFD choice signals presence of optional field • Payload control field • Controls effective data rate of the payload • Specifies the length of the payload in bytes • Extension bit for future PHR versions of the standard • Minimal overhead • Optional 802.15.4d packet format • Preamble optimization Slide 33

SFD switching: simple, powerful January 20 • Multiple frame formats accommodated • Mechanism is extensible and general Slide 34

Layering Principles • CPP conforms to existing 802.15.4 layering • CPP PHY layer provides only • A set of symbol rates • FEC on/off • One or two bits per symbol • Other functions appropriately left to the MAC layer • Addressing • CRC • Control functions (e.g., data rate changing)

Selection of Data Rate MAC instructs PHY to set channel mode - modulation type, symbol rate, channel and band to use MAC provides MCS parameters in PD-Data.request to PHY PHY encodes PSDU accordingly and sets PHR Control field Receiver mode set by MAC which uses MCS parameters to decode payload Network configuration (“Station Management”)is not in the scope of PHY amendment January 20 Slide 38

Precursor System Support Deployed devices may not be modifiable CPP proposes simple mechanism to support precursor systems which does not require modification of deployed devices. Proposal is consistent with the scope of the amendment and 802.15.4 CPP incorporates a streamlined yet inclusive set of parameters compatible with various precursor systems January 20 Slide 40

Extensible Features Mechanisms in the CPP allow features to be added to a particular implementation that may be outside the scope of the current standard Unique SFDs to distinguish different packet formats Configurable preamble New bands (band agnostic approach) Consistent with 802.15, mechanisms at the upper layers can be used to take advantage of flexibility in the PHY In addition, vendors of existing deployments have full knowledge of what is deployed and can provision systems accordingly January 20 Slide 41

Link Calculations

Link Margin Calculations • Based on data presented in Channel Characteristics Document #15-09-0279-01-004g collected from actual deployments courtesy Landis & Gyr and Silver Spring Networks • NIST link margin calculator to estimate signal strength at the receiver* • Required Eb/No consistent with Doc #0592-01-004g, and simulations for FS10 • Required Eb/No of ~ 24 dB for Bad Urban scenario, assuming 100 kbps, MSK, PER of 10% at 1000 bit packets • Required Eb/No of ~ 21 dB for FS10, assuming 100 kbps, MSK, PER of 10% at 1000 bit packets * http://www.antd.nist.gov/wctg/manet/req_linkcalc_xls.html

SUN Margin Calculation Setup • Transmit power of 30 dBm • Antenna gain of 5 dBi • Receive noise factor of 3 dB, no interference • Receive antenna height = 2m • Carrier frequency at 915 MHz • Data transmission at 100 kbps, 100 ksps, no coding

Urban Median Distance = 119.4 meters 75% of links are < 176.4 meters 95% of links are < 289.5 meters Max link = ~1000 meters

Suburban Median Distance = 113.4 m 75% of links are < 170.5 m 95% of links are < 280.4 m Max link = 1001.6 m

Rural Median Distance = 289.3 m 75% of links are < 622.2 m 95% of links are < 2926 m Max link = 7735 m

Mixed Deployment Mixed Deployment: use small city model 95% of links are < 182.9 m 98% of links are < 1200 m Max link = 1609.3 m Median Distance = 37.1m 75% of links are < 54.4m

Mixed Deployment Mixed Deployment: use small city model 95% of links are < 259.1 m 98% of links are < 365.76 m Max link =1609.3 m Median Distance = 45.7 m 75% of links are < 72 m

Summary of Performance • Several smart grid deployments have been analyzed in various multipath conditions: • The vast majority of nodes have many neighbors • Neighbors are within close proximity • Neighbors have a distribution of strong signal strengths due to their relative proximity • Results indicate that all links are above the threshold required for communication • Most SUN deployments are interference limited NOT noise limited. This is true globally.

CPP Conclusion January 20 • Globally deployable solution • Built on current standards and proven technology • Flexible to meet regional regulatory differences • Scalability to meet the varying utility needs • PHY parameter set optimized to meet real world needs • Flexible frame format that’s scalable for future needs • Strong coding performance to address fringe cases • Facilitation of data rate management by upper layers • Built in precursor systems supported naturally Slide 51

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