15-11-0605-00-004k J. Schwoerer (France Telecom) – N. Dejean (Elster)) Slide 1 Project: IEEE...

15-11-0605-00-004k

J. Schwoerer (France Telecom) – N. Dejean (Elster))Slide 1

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: [Elster & France Telecom proposal]Date Submitted: [15 September, 2011]Source: [Jean Schwoerer, Nicolas Dejean] Company [France Telecom R&D, Elster]Address [28 chemin du vieux chênes 38240 FRANCE ]Voice:[+33 4 76 76 44 83], FAX: [+33 4 76 76 44 50], E-Mail:[[email protected]]

Re: [.]

Abstract: [This document give preliminary information on the proposal that we submit]

Purpose: [Description of what the author wants P802.15 to do with the information in the document]

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.

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Slide 2

Orange - France Telecom / ELSTERTechnical Proposal

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Agenda

- LECIM devices needs :- Long range

- Low power

- Proposed network capabilities

- Proposed PHY features- RF characteristic

- FEC and interleaving

- MAC- Coexistence

- Conclusion

Slide 3

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Slide 4

Sub-GHz wireless connectivity platform

Battery powered LECIM devices will provides :– Long range (high link budget) for cost effective network

infrastructure and long operating range

– Ultra-low power management to reach multi-year operation

– Ability to peacefully coexist with other devices

– permanent reachability with human acceptable turn-around time (a few 10’s of sec)

Large scale wireless sensor network needs :• Typical network structure (star and tree) at reasonable cost

• Mesh / relaying for hard to reach endpoints or to recover wireless connectivity after major events

• Efficient power management to save endpoint battery life

• “almost” always on and limited latency for application involving IP or human interaction

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Slide 5


• How to get long range ? there is two way– Go wide band thanks to spread spectrum, and get benefit

from diversity and de-spreading gain

– Go narrow band and take benefit from – Increased sensivity (less noise)

– Limited cost and complexity

– Reduced spectrum use (better coexistence)

In addition, Frequency Hopping and efficient FEC and interleaving can bring diversity and reduce system margin, even for narrow band system

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Slide 6


Ultra-low power design to reach multi-year operation :• The best way to save power : just do nothing !• But we also need to save bidirectionnality and limited latency

• Network synchronization : • Allow endpoint sto sleep as soon as no activity is planned for them

• Minimize unwanted wake up and coordinate RX windows : each endpoint stay reachable in acceptable time (always-on illusion)

• Very short media probing at regular interval• Keep network probing duration as short as possible (direct impact on the duty

cycle!) and as low level as possible : Full wake up occurs only if some activity is detected on the channel

• Probing period can be in the order of one to a few second (low latency)

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Slide 7

Sub-GHz ISM license free bands 915MHz, 868MHz, 316-433MHz• better propagation properties and less interferences than 2.4 Ghz

Simple to implement modulation : GFSK / FSK • Simple and low power : very power efficient implementation are already

available for endpoint• Concentrator can offer more complex receiver (coherent, soft decision..)

Low data rate and narrow bandwidth : 15 Kbps GFSK modulation• 40 KHz bandwidth and 50 kHz channelization• Limited noise bandwidth : - 127 dBm thermal noise• RX sensitivity up to – 115 dBm (endpoint)• Low spectrum occupancy : better coexistence properties

Fundamentals – RF features

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Slide 8

• Intra Frame Frequency Hopping : Provide channel diversity– Frame is sliced into several data blocks – Data block length can be flexible (recommended : 255 symbols)– Hopping occurs between each data block over a N-hopping sequence– Short training symbol at the beginning of each data block– up to 63 channels in EU (863-870 MHz)– x50 channels or less to comply with FCC part.15-247 (915 MHz)

Fundamentals – Reliable Comms

SHR + PHR PSDUFrame

Chan. #1

Chan. #2

Chan. #N

SHR + PHR

PSDU – subpart #2

PSDU – subpart #N

Data block #1 Data block #2 Data block #N

PSDU

PSDU

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Slide 9

• Intra Frame Frequency Hopping : Provide channel diversity– First data block include SHR and PHR.– First data block can have increased duration if needed (preamble

sampling)– R-Sync : 2 bits “00” for carrier re-sync after hopping– Proposed data block length is : 255 symbols ( ~20 ms) + R-Sync– Only complete data block can be send : add padding bit if required– Minimum frame duration : 2 Data blocks


SHR + PHR PSDUFrame

Chan. #N PSDU – subpart #NR-Sync

Data block #1 Data block #2 Data block #N

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Slide 10

• 2 FEC for asymmetric protection :

Generic use : Convolutional codes K=7 (171,133) • Already included in 802.15.4 PHY• Endpoint : efficient protection for reasonable complexity (dmin=10)• Gateway : more complex RX implementation allow to increase

performance by 4 dB (hard decision, coherent RX)

Uplink : Endpoint to Gateway -> can use Turbo Code• Simple encoding is done by the endpoint – more complex decoding is

handled by Gateway.• Gateway is able to decode both FEC, whatever endpoint selected• Will provide close to Shannon limit performance.


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Slide 11

Data interleaving + LSFR data scrambling (whitenning)• Spread data and code bit among data blocks• Each blocks carry data bits and uncorrelated code bits


Random Interleaver :• Optimal performance

require 7 data blocks (typical 100 bytes frame)

• But some frame will be shorter.

• Random interleaver would allow Variable size between 2 to 7 Data blocks.

• Uniform distribution.

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Link Budget – 915 MHz

Slide 12

Channel Model Parameters Notes

Frequency (MHz) 915 Valid Range 150-2400 MHz

Collector Antenna Height (m) 30 Valid Range 30-200 m, including terrain.

Endpoint Antenna Height (m) 1 Valid Range 1-10 m

Distance (km) 2 Valid Range 1-20 km

Downlink Path Loss Calculation Notes

Collector Tx Power (dBm) 30 Subject to Tx Power Regulations

Collector Tx Antenna Gain (dBi) 6 Subject to Tx Power Regulations

Hata Path Loss (dB) -128,53Must reference the right path loss from the

next worksheet

Shadowing Margin (dB) -16 To buffer against variable shadowing loss

Penetration Loss (dB) -10 For underground vaults, etc.

Endpoint Rx Antenna Gain (dBi) 2If using same antenna for Tx, must be same

as in Uplink Table

Endpoint Interference (dB) 1 Rise over Thermal Interference

Rx Power at Endpoint (dBm) -115,53 Compare against Rx sensitivity

Uplink Path Loss Calculation Notes

Endpoint Tx Power (dBm) 27Subject to Tx Power Regulations. Can be

different from Collector

Endpoint Tx Antenna Gain (dBi) 2 Subject to Tx Power Regulations

Penetration Loss (dB) -10 For underground vaults, etc.

Hata Path Loss (dB) -128,53 Same as Downlink

Shadowing Margin (dB) -16 Same as Downlink

Collector Rx Antenna Gain (dBi)6 If using same antenna for Tx, must be same

as in Downlink Table

Collector Interference (dB) 10 Rise over Thermal Interference

Rx Power at Collector (dBm) -109,53 Compare against Rx sensitivity

Scenario 1 : 2 km range in a Sub-urban area, between pole and indoor meter

Indoor endpoint

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Link Budget – 868 MHz 25 mW

Slide 13

Help to save endpoint power

Scenario 2 : 1 km range in a Sub-urban area, between pole and typical outdoor gaz meter

Outdoor endpoint

Channel Model Parameters Notes

Frequency (MHz) 868 Valid Range 150-2400 MHz


Endpoint Antenna Height (m) 1 Valid Range 1-10 m

Distance (km) 1 Valid Range 1-20 km

Downlink Path Loss Calculation Notes

Collector Tx Power (dBm) 14 Subject to Tx Power Regulations


Hata Path Loss (dB) -117,47Must reference the right path loss from the next

worksheet

Shadowing Margin (dB) -16 To buffer against variable shadowing loss

Penetration Loss (dB) 0 For underground vaults, etc.

Endpoint Rx Antenna Gain (dBi) 2If using same antenna for Tx, must be same as in

Uplink Table





different from Collector

Endpoint Tx Antenna Gain (dBi) 2 Subject to Tx Power Regulations

Penetration Loss (dB) 0 For underground vaults, etc.

Hata Path Loss (dB) -117,47 Same as Downlink


Collector Rx Antenna Gain (dBi) 6If using same antenna for Tx, must be same as in

Downlink Table



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Link Budget – 868 MHz 25 mW

Slide 14

Scenario 3 : 100m range in a Sub-urban area, between a rooftop device and underground water meter (typical relaying scenarios)

Underground endpoint

Channel Model Parameters NotesFrequency (MHz) 868 Valid Range 150-2400 MHz


Endpoint Antenna Height (m) 1 Valid Range 1-10 mDistance (km) 0,1 Valid Range 1-20 km

Downlink Path Loss Calculation NotesCollector Tx Power (dBm) 12 Subject to Tx Power Regulations


Wallfish Ikegami Path Loss (dB) -99,57Must reference the right path loss from the next

worksheet

Shadowing Margin (dB) -10 To buffer against variable shadowing lossPenetration Loss (dB) -20 For underground vaults, etc.

Endpoint Rx Antenna Gain (dBi) 2If using same antenna for Tx, must be same as in

Uplink Table





different from CollectorEndpoint Tx Antenna Gain (dBi) 2 Subject to Tx Power Regulations

Penetration Loss (dB) -20 For underground vaults, etc.Hata Path Loss (dB) -99,57 Same as Downlink


Collector Rx Antenna Gain (dBi) 2If using same antenna for Tx, must be same as in

Downlink Table



Wallfish Ikegami model as valid range down to 20m.

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Frame Fragmentation

Transmitting long frame at a low date rate can be problematic :• Channel coherence time is estimated to 20 ms (300bits@15kbit/S)

• Frame error rate increased when frame length increase

But Fast FH provide a «de-facto» PHY fragmentation :• A frame is sliced in several “data blocks” (min 2 / max 128)

• Data block duration is shorter than channel coherence time

• Frame length and data block size give the number of data block

• Each data block is identified by his position in the hopping sequence

• Only ACK need to be modified to allows signaling of damaged data block

Slide 15

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Slide 16

15.4e TSCH resources management• Time Slot Channel Hopping defines the automatic

repetition of a slotframe based on a shared notion of time• TSCH Allows the devices hopping over the entire channel

space in a slotted way thus minimizing the negative effects of multipath fading and interference while avoiding collisions

• Slotframe is configurable through the definition of the channels used, the number of slots and the duration of the slots

• TSCH parameters will define data block duration

MAC Layer compatibility

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Slide 17

Packet fragmentation in a slotframe• Fast FH provide a PHY level fragmentation• The adaptation layer between PHY and MAC uses the channel

management scheme of 15.4e TSCH mode for hopping on PHY data blocks

• The first data block carries the PHR, including frame length and thus the total number of data blocks.

• The following data blocks are sent on the different channels.• After the last data block, a group ACK is sent in the other direction, each bit

of this group representing the correct reception of the corresponding data block.

• Only the data blocks which have not been correctly received are retransmitted

.

MAC Layer compatibility

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Slide 18

As an example, with a 15kbps data rate and ½ FEC, 16 data bytes can be transmitted in a ~20ms slot

Data block duration is shortest than channel coherence time

128 slots are required for transmitting 2047 bytes (longuest possible frame)

Average 100 bytes frames will requires 7 data blocks

Example

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Slide 19

Several mean to help coexistence

- Narrow channel (50 kHz) : limited spectrum usage

- Frequency hopping :- Adequate sequences management mitigate

interference between independent networks- Short data block minimize interference on a

single channel as individual channel occupancy time remain low

Coexistence

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Conclusions- FSK/GFSK are proven solutions :

- To address very low power wireless devices

- To allow flexible implementations

- Narrow band, FH, efficient FEC and interleaving allow supporting path loss larger than 140 dB.- Frequency Hopping bring channel diversity and frame

fragmentation “built-in” : improved robustness

- Relaying allows yet improved network coverage and network resilience against major channel changes

- but handling yet higher path loss requires other technology

- Limited latency and always-on behaviour can be provided at an acceptable cost

Will be happy to discuss exchange with everybody interestedSlide 20

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Slide 21

Thank You

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FSK Receiver implementation

Slide 22

Comparison between :- Low cost non coherent FSK receiver using hard decision and viterbi decoder- Coherent FSK receiver using soft decision and viterbi decoder

- Performance increase by 4 dB at BER = 1.10e-3

15-11-0605-00-004k J. Schwoerer (France Telecom) – N. Dejean (Elster)) Slide 1 Project: IEEE...

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