1. March 2016
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Proposal for an adaptive throughput/link-budget mode in the PHY]
Date Submitted: [March 15, 2016]
Source: [Willem Mulder] Company [Dialog Semiconductor]
Address [Het Zuiderkruis 52, 5215MV, Den Bosch, Netherlands]
Voice:[ ], Fax: [ ],
Abstract: [Proposal for an adaptive throughput/link-budget mode in the PHY]
Purpose: [Initiate discussion]
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 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 P
Willem Mulder, Dialog Semiconductor.

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

3. 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

4. 802.15.4 Sensor Network Topology
March 2016
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

5. The 802.15.4 PHY PHY Packet Fields
March 2016
The 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 – ms
12 symbols
0 – 254 symbols
PHY packet duration: max ms
1 symbol = 16us = 0.5 byte (octet)
Willem Mulder, Dialog Semiconductor

6. 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 MAC packet
Data-poll packet
ms (64/63 bytes overhead/payload with DTLS, 35/92 bytes overhead/payload without DTLS)
6LoWPAN enabled Data-transfer packet
Willem Mulder, Dialog Semiconductor

7. 802.15.4 Authentication and Security
March 2016
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

8. Excellent Autocorrelation
March 2016
The 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

9. The 802.15.4 PHY What when we don’t need 127 bytes ?
March 2016
The 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 – ms
12 symbols
0 – 254 symbols
Boundary conditions / Design considerations:
RF compatible (channel BW, chiprate, O-QPSK-sensitivity)
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

10. 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

11. 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 proc gain 5
30.1 dB
21 dB on top of the default proc gain 6
39.1 dB
30 dB on top of the default proc gain
pn-codes shall have a regular/repeating stucture (correlator complexity)
Willem Mulder, Dialog Semiconductor

12. March 2016
The proposal:
To develop an optional adaptive throughput/link-budget allocation mode for the 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