March 2016 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Proposal for an adaptive throughput/link-budget mode in the 802.15.4 PHY] Date Submitted: [March 15, 2016] Source: [Willem Mulder] Company [Dialog Semiconductor] Address [Het Zuiderkruis 52, 5215MV, Den Bosch, Netherlands] Voice:[+31 6 45232890], Fax: [+31 736408823], E-Mail:[willem.mulder@diasemi.com] Abstract: [Proposal for an adaptive throughput/link-budget mode in the 802.15.4 PHY] Purpose: [Initiate discussion] 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 or organization. The material in this document is subject to change in form and content after further study. The contributor reserves 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. Willem Mulder, Dialog Semiconductor.

an adaptive throughput/link-budget mode in the 802.15.4 PHY March 2016 Proposal for an adaptive throughput/link-budget mode in the 802.15.4 PHY Willem Mulder, Dialog Semiconductor

IoT in the Smart Home Smart Home connectivity in the ISM band. March 2016 IoT in the Smart Home Smart Home connectivity in the ISM band. “Best Effort” connectivity. Proven technology, it works great. For some use cases, “Best Effort” is not enough Safety sensors (Fire/CarbonMonoxide) => single bit messages, extreme reliability requirements Security sensors Door-locks Can we ignore these use cases ? We think not.. Why don’t we use adaptive throughput/link-budget allocation like WiFi ,UMTS, LTE ? Willem Mulder, Dialog Semiconductor

802.15.4 Sensor Network Topology March 2016 802.15.4 Sensor Network Topology A global IPv6-enabled mesh network example Shannon: Fixed 250 kbps throughput, fixed link-budget What holds us from trading throughput for link-budget ? Network Device (Sleepy End Device) FFD Coordinator (Border Router) FFD Coordinator (Router) Network Device (Powered End Device) FFD PAN Coordinator (Leader) Router–Router link SED link Wifi link Willem Mulder, Dialog Semiconductor

The 802.15.4 PHY PHY Packet Fields March 2016 The 802.15.4 PHY PHY Packet Fields Preamble (32 bits) – synchronization Start of Packet Delimiter (8 bits) PHY Header (8 bits) – PSDU length PSDU (0 to 1016 bits) – Data field PHY Payload: max 127 bytes 32 bits 8 bits 8 bits 0 – 1016 bits (127 bytes) Preamble SPD PHDR PSDU 128 us 32 us 32 us 0 – 4.064 ms 12 symbols 0 – 254 symbols PHY packet duration: max 4.256 ms 1 symbol = 16us = 0.5 byte (octet) Willem Mulder, Dialog Semiconductor

How do we use the payload ? March 2016 How do we use the payload ? What holds us from scaling down the throughput ? Authentication Security Routing Medium Access 768 us (24 bytes), native 802.15.4 MAC packet 802.15.4 Data-poll packet 1 .. 4 ms (64/63 bytes overhead/payload with DTLS, 35/92 bytes overhead/payload without DTLS) 6LoWPAN enabled Data-transfer packet Willem Mulder, Dialog Semiconductor

802.15.4 Authentication and Security March 2016 802.15.4 Authentication and Security Receive Side Step 1: Message Authentication Message Integrity Hash AES-CCM32 Step 2: Encryption Encrypt Decrypt AES-CCM32 AES-CCM32 Transmit Side 16 Message Integrity Hash Compare AES-CCM32 16 MAC Security Key MAC Security Key Willem Mulder, Dialog Semiconductor

Excellent Autocorrelation March 2016 The 802.15.4 PHY Trading throughput for link-budget: we already do it Each new symbol is created by a 4-chip right-shift (first 8 symbols), or by taking the complex conjugate (last 8 symbols), reducing correlator complexity (cost) … Excellent Autocorrelation Good Hamming Distance mean = 17 min = 12 max = 21 I Tchip = 0.5 us, 32 chips/symbol Tsymbol = 16 us, 4 bits/symbol Q => 2.5 dB coding gain => 9 dB processing gain => 250 kbps throughput Willem Mulder, Dialog Semiconductor

The 802.15.4 PHY What when we don’t need 127 bytes ? March 2016 The 802.15.4 PHY What when we don’t need 127 bytes ? How scalable are we ? 256 chips 32 chips 32 chips 0 – 8128 chips Preamble SPD PHDR PSDU 128 us 32 us 32 us 0 – 4.064 ms 12 symbols 0 – 254 symbols Boundary conditions / Design considerations: 802.15.4 RF compatible (channel BW, chiprate, O-QPSK-sensitivity) 802.15.4 Receiver-conditioning compatible (Preamble, AGC, ..) Flexible packet size/pn-code-length, max pn-code-length is 8128 chips Processing gain upper bound: 39.1 dB for a 1-bit message Coding gain: dependent on the chosen pn-code-bundle (Hamming distance) Security/Authentication: use pn-code-selection and pn-code-rotation Processing gain: energy-per-bit to energy-per-chip ratio in zero-mean AWGN channels Coding gain / Hamming distance: how many chips can go wrong before our detector chooses the wrong code Willem Mulder, Dialog Semiconductor

Corner Case: 1-bit Extreme Reliability March 2016 Corner Case: 1-bit Extreme Reliability Robustness: Mesh Diversity: Multiple ER receivers (Routers) Extended link budget (Processing Gain) Multiple IPv6 routes - to any IPv6 destination on Earth Extreme Reliability Node 1 ER-Node commissioning using the regular protocol 2 ER-Node subscribes at multiple ER-capable Routers 3 ER-Node receives the security parameters 4 ER-Node sends the alert-action table to the Router 5 pn-code-bundle and pn-code-rotation agreed (security/authentication by code-selection) 6 ER-node switches to ER-mode-operation: send regular heartbeat-messages send alert-messages when needed Sleepy End Device Border Router Router Powered End Device Leader role Router–Router link SED link Wifi link Willem Mulder, Dialog Semiconductor

Trading throughput for Link Budget March 2016 Trading throughput for Link Budget Some reference numbers scenario pn seq length databits proc gain note 1 1.0 8128.0 0.0 dB no DSSS 2 8.0 1016.0 9.0 dB todays symbol detector (32 chips per 4 data bits) 3 320.0 25.4 25.1 dB todays preamble detector (320 chips per bit) 4 508.0 16.0 27.1 dB 18 dB on top of the default 802.15 proc gain 5 30.1 dB 21 dB on top of the default 802.15 proc gain 6 39.1 dB 30 dB on top of the default 802.15 proc gain pn-codes shall have a regular/repeating stucture (correlator complexity) Willem Mulder, Dialog Semiconductor

March 2016 The proposal: To develop an optional adaptive throughput/link-budget allocation mode for the 802.15.4 PHY The 5 IEEE 802 LMSC PAR review criteria : Broad Market Potential Broad sets of applicability. Multiple vendors and numerous users. Compatibility Compliance with IEEE Std 802 Compliance with IEEE Std 802.1D Compliance with IEEE Std 802.1Q Distinct Identity Substantially different from other IEEE 802 standards. One unique solution per problem (not two solutions to a problem) Technical Feasibility Demonstrated system feasibility Proven technology, reasonable testing Confidence in reliability Economic Feasibility Known cost factors, reliable data Reasonable cost for performance Consideration of installation costs Willem Mulder, Dialog Semiconductor