Transcript March 2016 - IEEE Mentor

March 2016
doc.: IEEE 802.15-16-0238-00
EC Monday Meeting Report
March 14, 2016
Venetian Macau Hotel and Casino
Macau, China
Submission
Slide 1
Willem Mulder, Dialog Semiconductor
March 2016
doc.: IEEE 802.15-16-0238-00
Proposal for
an adaptive throughput/linkbudget mode in the 802.15.4 PHY
Submission
2
Willem Mulder, Dialog Semiconductor
March 2016
doc.: IEEE 802.15-16-0238-00
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
=> single bit messages, extreme reliability requirements
Door-locks
=> single bit messages, extreme reliability requirements
Can we ignore these use cases ? We think not..
Why don’t we use adaptive throughput/link-budget allocation like WiFi,UMTS,LTE ?
Submission
3
Willem Mulder, Dialog Semiconductor
March 2016
doc.: IEEE 802.15-16-0238-00
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 ?
FFD Coordinator (Router)
FFD Coordinator (Border Router)
FFD PAN Coordinator (Leader)
Network Device (Sleepy End Device)
Network Device (Powered End Device)
Submission
Router–Router link
SED link
Wifi link
4
Willem Mulder, Dialog Semiconductor
March 2016
doc.: IEEE 802.15-16-0238-00
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
32 bits
Preamble
128 us
PHY Payload: max 127 bytes
0 – 1016 bits (127 bytes)
8 bits
8 bits
SPD
PHD
R
PSDU
32 us
32 us
0 – 4.064 ms
0 – 254 symbols
12 symbols
PHY packet duration: max 4.256 ms
1 symbol = 16us = 0.5 byte (octet)
Submission
5
Willem Mulder, Dialog Semiconductor
March 2016
doc.: IEEE 802.15-16-0238-00
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
Submission
6
Willem Mulder, Dialog Semiconductor
March 2016
doc.: IEEE 802.15-16-0238-00
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
Message Integrity
Hash
16
MAC Security Key
Submission
MAC Security Key
16
Compar
e
AES-CCM32
Willem Mulder, Dialog Semiconductor7
March 2016
doc.: IEEE 802.15-16-0238-00
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
I
Good Hamming Distance
• mean = 17
• min = 12
• max = 21
Tchip = 0.5 us, 32 chips/symbol
Q
Submission
Tsymbol = 16 us, 4 bits/symbol
=> 2.5 dB coding gain
=> 9 dB processing gain
=> 250 kbps throughput
Willem Mulder, Dialog Semiconductor
8
March 2016
doc.: IEEE 802.15-16-0238-00
The 802.15.4 PHY
What when we don’t need 127 bytes ?
How scalable are we ?
256 chips
Preamble
128 us
0 – 8128 chips
32 chips 32 chips
SPD
PHD
R
PSDU
32 us
32 us
0 – 4.064 ms
0 – 254 symbols
12 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
Submission
9
Willem Mulder, Dialog Semiconductor
March 2016
doc.: IEEE 802.15-16-0238-00
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
Router
Border Router
Leader role
Sleepy End Device
Powered End Device
Submission
Router–Router link
SED link
Wifi link
10
Willem Mulder, Dialog Semiconductor
March 2016
doc.: IEEE 802.15-16-0238-00
Trading throughput for Link Budget
Some reference numbers
scenario
pn seq length
databits
1
1.0
8128.0
2
3
4
5
6
8.0
320.0
508.0
1016.0
8128.0
1016.0
25.4
16.0
8.0
1.0
proc gain note
0.0 dB no DSSS
todays symbol detector (32 chips per 4 data
9.0 dB bits)
25.1 dB todays preamble detector (320 chips per bit)
27.1 dB 18 dB on top of the default 802.15 proc gain
30.1 dB 21 dB on top of the default 802.15 proc gain
39.1 dB 30 dB on top of the default 802.15 proc gain
pn-codes shall have a regular/repeating stucture (correlator complexity)
Submission
11
Willem Mulder, Dialog Semiconductor
March 2016
doc.: IEEE 802.15-16-0238-00
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 :
1.
2.
3.
4.
5.
Submission
Broad Market Potential
a) Broad sets of applicability.
b) Multiple vendors and numerous users.
Compatibility
a) Compliance with IEEE Std 802
b) Compliance with IEEE Std 802.1D
c) Compliance with IEEE Std 802.1Q
Distinct Identity
a) Substantially different from other IEEE 802 standards.
b) One unique solution per problem (not two solutions to a problem)
Technical Feasibility
a) Demonstrated system feasibility
b) Proven technology, reasonable testing
c) Confidence in reliability
Economic Feasibility
a) Known cost factors, reliable data
b) Reasonable cost for performance
c) Consideration of installation costs
12
Willem Mulder, Dialog Semiconductor