[PPT] - UWB-TSCH : Time and Frequency Division Multiplexing for PowerPoint Presentation

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UWB-TSCH : Time and Frequency Division Multiplexing for Ultra-wideband Communications

Maximilien Charlier

University of Mons, Belgium

June 4, 2019

CORES 2019

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UWB UWB-TSCH Test & Validation Conclusion

Ultra Wideband

Wireless communication technology Pulse radio Frequency band ≥ 500 MHz Very short pulse (<ns) ⇒ Wide frequency band

Figure: Pulse waveform

Source: wlan62d [2] Maximilien Charlier Challenges in Using TSCH with UWB CommunicationsJune 4, 2019 4/26

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UWB UWB-TSCH Test & Validation Conclusion

Ultra Wideband

Low power spectral density

The power is spread over the whole UWB spectrum, therefore, the power density is much lower than narrow band technology.

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UWB UWB-TSCH Test & Validation Conclusion

Medium Access Control

1 Transmit as soon as possible

ALOHA

Low channel occupancy Low power efficiency (overhearing)

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UWB UWB-TSCH Test & Validation Conclusion

Medium Access Control

1 Transmit as soon as possible

ALOHA

Low channel occupancy Low power efficiency (overhearing)

2 Listen before transmit

Carrier-Sense Multiple Access (CSMA)

Reduce collision No Clear Channel Assessment in UWB (PSD too low)

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UWB UWB-TSCH Test & Validation Conclusion

Medium Access Control

1 Transmit as soon as possible

ALOHA

Low channel occupancy Low power efficiency (overhearing)

2 Listen before transmit

Carrier-Sense Multiple Access (CSMA)

Reduce collision No Clear Channel Assessment in UWB (PSD too low)

3 Transmit according a scheduling

Time Division Multiple Access (TDMA)

Channel occupancy improvement Minimization of the power consumption

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UWB UWB-TSCH Test & Validation Conclusion

Medium Access Control

1 Transmit as soon as possible

ALOHA

Low channel occupancy Low power efficiency (overhearing)

2 Listen before transmit

Carrier-Sense Multiple Access (CSMA)

Reduce collision No Clear Channel Assessment in UWB (PSD too low)

3 Transmit according a scheduling

Time Division Multiple Access (TDMA)

Channel occupancy improvement Minimization of the power consumption

Our proposal: ⇒ Increase of channel occupancy by adapting TSCH to UWB.

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UWB UWB-TSCH Test & Validation Conclusion

Time Slotted Channel Hopping

TSCH is a 802.15.4 MAC protocol originally for Narrow Band. Time Domain/TDMA (Time Slotted)

Challenge: new PHY parameters (preamble, bit-rate)

Frequency Domain (Channel Hopping)

Narrow band: improvement of the resilience to interference UWB: maximizing the bandwidth (with concurrent communications) Challenge: concurrent communication, channel agility

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UWB UWB-TSCH Test & Validation Conclusion

TSCH - Time slot

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UWB UWB-TSCH Test & Validation Conclusion

TSCH - Time slot

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UWB UWB-TSCH Test & Validation Conclusion

TSCH - Time slot

Clock drift ⇒ Guard time

RXGuard : clock drift & clock granularity

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UWB UWB-TSCH Test & Validation Conclusion

TSCH - Time slot

Clock drift ⇒ Guard time

RXGuard : clock drift & clock granularity

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UWB UWB-TSCH Test & Validation Conclusion

TSCH - Time slot

Clock drift ⇒ Guard time

RXGuard : clock drift & clock granularity

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UWB UWB-TSCH Test & Validation Conclusion

TSCH - Time slot

Clock drift ⇒ Guard time

RXGuard : clock drift & clock granularity AckGuard : clock granularity

Maximilien Charlier Challenges in Using TSCH with UWB CommunicationsJune 4, 2019 9/26

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UWB UWB-TSCH Test & Validation Conclusion

Scheduling

Transmissions to each neighbour scheduled locally within a slotframe.

A → B 1 2 3 4 5 Channel Offset (Freq. domain) 1 2 3 TimeSlot Number (TSN)

Example of slotframe

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UWB UWB-TSCH Test & Validation Conclusion

Scheduling

Transmissions to each neighbour scheduled locally within a slotframe.

A → B 1 2 3 4 5 Channel Offset (Freq. domain) 1 2 3 4 Absolute Slot Number (ASN) - (Time domain) 1 2 3 TimeSlot Number (TSN)

Example of slotframe

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UWB UWB-TSCH Test & Validation Conclusion

Scheduling

Transmissions to each neighbour scheduled locally within a slotframe.

A → B B → D B → A 1 2 3 4 5 Channel Offset (Freq. domain) 1 2 3 4 Absolute Slot Number (ASN) - (Time domain) 1 2 3 TimeSlot Number (TSN)

Example of slotframe

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UWB UWB-TSCH Test & Validation Conclusion

Scheduling

Transmissions to each neighbour scheduled locally within a slotframe.

A → B B → D B → A D → C A → C 1 2 3 4 5 Channel Offset (Freq. domain) 1 2 3 4 Absolute Slot Number (ASN) - (Time domain) 1 2 3 TimeSlot Number (TSN)

Example of scheduling

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UWB UWB-TSCH Test & Validation Conclusion

Channel Hopping

IEEE 802.15.4 defines 16 channels for the UWB PHY ranging from 249.6 MHz up to 10.16 GHz.

3494 3994 4493 3994 6490 6490 Frequency (MHz) 1 2 3 4 5 7 Channel Index

Subset of the UWB channels defined by IEEE 802.15.4 [3] suported by Decawave transceiver.

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UWB UWB-TSCH Test & Validation Conclusion

Channel Hopping

Channel 2 overlaps with channel 1 and 3.

3245 3494 3744 3744 3994 4243 4243 4493 4742 Frequency (MHz) −10 −18 Power Spectral Density (dBm) Channel 1 Channel 2 Channel 3

Transmit PSD mask of UWB Channel 1-3 [3].

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UWB UWB-TSCH Test & Validation Conclusion

Channel Hopping

3 possible simultaneous communications based on 3 separate channels.

3494 3994 4493 3994 6490 6490 Frequency (MHz) 1 2 3 4 5 7 Channel Index

Subset of the UWB channels defined by IEEE 802.15.4 [3] suported by Decawave transceiver.

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UWB UWB-TSCH Test & Validation Conclusion

Channel Hopping

The Pulse Repetition Frequencies (PRF) parameter allows concurrent communication

n the same physical channel.

Channel 1 Ch.1, PRF 16 MHz Ch.1, PRF 64 MHz

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UWB UWB-TSCH Test & Validation Conclusion

Channel Hopping

6 possibles simultaneous communications based on 3 separate channels and 2 Pulse Repetition Frequencies (PRF).

3494 3994 4493 3994 6490 6490 Frequency (MHz) 1 2 3 4 5 7 Channel Index

Subset of the UWB channels defined by IEEE 802.15.4 [3] suported by Decawave transceiver.

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UWB UWB-TSCH Test & Validation Conclusion

Platform

Operating System

Currently Contiki OS.

Embedded system

Zolertia Firefly 32-bit ARM Cortex-M3 512 KB flash and 32 KB RAM CPU running at 16 MHz

IEEE 802.15.4-UWB transceiver

Decawave DWM1000 module

MCU ↔ transceiver through SPI bus

Figure: Firefly (Left), DWM1000 (Right)

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UWB UWB-TSCH Test & Validation Conclusion

Research questions

Channel Access

What is the impact of overlapping channels (1 ← 2 → 3) on the loss rate? Can we perform concurrent communications on the same physical channel?

Time accuracy

Local: Are time slot events performed accuratly? Global: Is the network correctly synchronized?

What about the Packet Delivery Ratio?

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UWB UWB-TSCH Test & Validation Conclusion

Channel 2 overlapping

80k simultaneous message transmissions for each of the 28 combinations of channel and PRF (4 physical channels, 2 PRF:

8∗(8−1) 2

= 28) Result: With channel 2 ⇒ 0.06% loss Without channel 2 ⇒ 0.02% loss

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UWB UWB-TSCH Test & Validation Conclusion

Timing accuracy

Setup Birate of 6.8 Mbps (time slot duration of 2.5 ms) 5 nodes in linear topology 1 UDP server and 4 clients Each client sends 1 message every 60 seconds 5 millions of active slots (1 million slots per nodes) over 14 hours

N1 Server N2 Client N3 Client N4 Client N5 Client

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UWB UWB-TSCH Test & Validation Conclusion

Timing accuracy

Setup

Logic analyzer connected to multiple nodes

A B tStart tStart tTX1 tRX1 tTX2 tRX2 tSFD tRX3 tTX3 tRX4 tTX4 tEnd tEnd 500 1000 1500 2000 2500 Time (µs) Rx Tx SHR Tx Data

Event monitored using the logic analyser

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UWB UWB-TSCH Test & Validation Conclusion

Local synchronization

RxOffset RxWait RxWait (false) TxAckDelay RxAckDelay Ack Lag −80 −70 −60 −50 −40 −30 −20 −10 10 20 30 40 50 60 Error (µs) −2 −1 1 2 Error (32 kHz ticks) Internal slot error: always less than 2 clock ticks (2 × 30.4µs)

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UWB UWB-TSCH Test & Validation Conclusion

Network synchronization

Source Clock N1 Server N2 Client N3 Client N4 Client N5 Client −600 −400 −200 200 400 600 Error (µs) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Frequency (%) Guard time N2 N3 N4 N5

Global synchronization error in µs

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UWB UWB-TSCH Test & Validation Conclusion

Packet Delivery Ratio (PDR)

Setup: 6 nodes Linear topology (5 hops) Transport layer: 5 UDP messages per second (per client) Link layer for all clients: total of 75 messages per second 750K UDP messages send to the sink over 8 hours experiment Result: PDR of 99.8732% without retransmition PDR of 99.9997% with up to 8 retransmitions

N1 Server N2 Client N3 Client N4 Client N5 Client N6 Client Maximilien Charlier Challenges in Using TSCH with UWB Communications June 4, 2019 24/26

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UWB UWB-TSCH Test & Validation Conclusion

Conclusion

Achievements TSCH-inspired UWB medium access control Working prototype based on off-the-shelf transceiver Future work Definition of a Two-Way Ranging slot (ongoing) Scheduling of concurrent localization Large scale testbed validation

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UWB UWB-TSCH Test & Validation Conclusion

Thank you for your attention, Any questions?

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UWB UWB-TSCH Test & Validation Conclusion

Bibliography I

[1] “Museum Tour App.” http://museumanywhere.com/museum-tour-app/. [On line; 2019-04-02]. [2] “Ultra wideband (UWB) Radios for Precision Location.” http://www.wlan01.wpi.edu/proceedings/wlan62d.pdf. [On line; 2018-07-06]. [3] “IEEE Standard for Low-Rate Wireless Networks,” IEEE Std 802.15.4-2015 (Revision of IEEE Std 802.15.4-2011), pp. 1–709, April 2016. [4] Federal Communication Commission, “First Report and Order, Revision of part 15 of the commission’s rules regarding ultra-wideband transmission system.” https://docs.fcc.gov/public/attachments/FCC-02-48A1.pdf. FCC 02–48, Apr. 2002, [Online]. [5] UWB Alliance, “UWB Alliance to Lead Industry Growth and Drive Global Standards.” https://uwballiance.org/press-releases/. [2018-12-19].

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UWB UWB-TSCH Test & Validation Conclusion

Ultra Wideband

History

Until early 2000 ⇒ Military usage only Radar & Stealth/undetectable wireless transmission UWB become unlicensed in 2002 [4] Two standardisation processes: High bitrate Low power ⇓ ⇓ IEEE 802.15.3 IEEE 802.15.4 ≥ 2007 2018: UWB Alliance creation ⇒ IEEE 802.15.4z expected for second half of 2019 [5]. ⇒ Technological merge upon by multiple silicon vendors, integration in smartphone.

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UWB UWB-TSCH Test & Validation Conclusion

Channel Offset

UWB-TSCH channels: ch = HS [(ASN + channelOffset) mod |HS|] Example of Hopping Sequence: HS = {2, 1, 3, 5, 0, 4}, |HS| = 6

Proposed UWB-TSCH channels.

Channels PRF UWB-TSCH UWB (MHz) 1 15.6 1 3 15.6 2 5 15.6 3 1 62.4 4 3 62.4 5 5 62.4

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UWB UWB-TSCH Test & Validation Conclusion

UWB Data Slot

Example at 6.8 Mbps Slot duration : 2.5 ms Wakeup duration : 2.5 ms

A B Jitter Wake up Pin Deepsleep To Init Init To IDLE IDLE Restoration Start Channel Hopping get payload prepare() ready read() create prepare() ready read() parse sync sync to buffer End Enter in Deepsleep Scheduling

2500
2000
1500
1000
500

500 1000 1500 2000 2500 3000 Time (µs) Rx Tx SHR Tx Data

Figure: Data slot, A send to B

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UWB UWB-TSCH Test & Validation Conclusion

IoT network stack

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UWB UWB-TSCH Test & Validation Conclusion

IEEE 802.15.4 UWB

IEEE 802.15.4 Low Power Standardization

Transmission time: 3 parts at different symbols rates.

1 Synchronization header (SHR) 2 Physical Header (PHR) 3 Data part (PSDU)

UWB frame format

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UWB UWB-TSCH Test & Validation Conclusion

Two Way Ranging technique

Based on the propagation time Distance = Tprop ∗ c with c = 299 792 458 m/s 1 meter traveled in 3.3 ns Tprop = RX − TX − TreplyA 2

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UWB UWB-TSCH Test & Validation Conclusion

Double Sided Two Way Ranging

Compute the propagation time on each side and use the mean ⇒ Cancel the clock drift error

Figure: DS-TWR

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UWB UWB-TSCH Test & Validation Conclusion

Application to large scale scenario

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UWB UWB-TSCH Test & Validation Conclusion

Application to large scale scenario

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UWB UWB-TSCH Test & Validation Conclusion

Testbed

Composition : 27 fixed nodes 13 mobiles nodes USB architecture

Centralized Raspberry Pi

Experimentation : Localization Concurrent localization Scheduling Synchronization

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UWB UWB-TSCH Test & Validation Conclusion

Testbed

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UWB UWB-TSCH Test & Validation Conclusion

Channel 2 overlapping

Channel 2 has a higher loss rate

1 - 16 2 - 16 3 - 16 5 - 16 1 - 64 2 - 64 3 - 64 5 - 64 [UWB PHY Channel] - [PRF (MHz)] 0.0 0.1 0.2 0.3 0.4 Loss (%) Maximum loss With all channels Without channel 2

Mean (bars) and max (dots) channel loss per channel/PRF combination based on 2 millions of simultaneous transmissions.

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UWB-TSCH : Time and Frequency Division Multiplexing for Ultra-wideband Communications

Table of contents

Table of contents

Ultra Wideband

Ultra Wideband

Medium Access Control

Medium Access Control

Medium Access Control

Medium Access Control

Table of contents

Time Slotted Channel Hopping

TSCH - Time slot

TSCH - Time slot

TSCH - Time slot

TSCH - Time slot

TSCH - Time slot

TSCH - Time slot

Scheduling

Scheduling

Scheduling

Scheduling

Channel Hopping

Channel Hopping

Channel Hopping

Channel Hopping

Channel Hopping

Table of contents

Platform

Research questions

Channel 2 overlapping

Timing accuracy

Timing accuracy

Local synchronization

Network synchronization

Packet Delivery Ratio (PDR)

Table of contents

Conclusion

Thank you for your attention, Any questions?

Bibliography I

Ultra Wideband

Channel Offset

UWB Data Slot

IoT network stack

IEEE 802.15.4 UWB

Two Way Ranging technique

Double Sided Two Way Ranging

Application to large scale scenario

Application to large scale scenario

Testbed

Testbed

Channel 2 overlapping