1. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
10 March, 2009
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Preliminary IMEC Proposal]
Date Submitted: [10 March, 2009]
Source: [Guido Dolmans, Li Huang, Yan Zhang] Company [Holst Centre / IMEC-NL]
Address [High Tech Campus 31, Eindhoven, the Netherlands]
Voice:[ ], FAX: [ ],
Abstract: [This presentation puts forward a preliminary proposal for IEEE PHY and partly MAC.]
Purpose: [For discussion by the group in order to provide applications scenarios, develop channel models and discuss radio architectures for IEEE P ]
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(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 P
Guido Dolmans, IMEC-NL
<author>, <company>

2. Outline WBAN PHY proposal Conclusions
10 March, 2009
Outline
WBAN PHY proposal
Dual-radio (ISM Band Main Radio and ISM Band Wake-up) WBAN Overview
ISM band Transceiver
Wake-up Receiver
Conclusions
Guido Dolmans, IMEC-NL

3. 802.15.6 Technical Requirements
10 March, 2009
Technical Requirements
Miniaturized sensor nodes – small form factor
Limited range (3 meters, extendable to 5 meters)
Significant path loss
Energy scavenging / battery-less operation
Scalable data rate: 10 kbps - 10 Mbps
Extremely low consumption power (0.1 to 1 mW)
Different classes of QoS for high reliability, low latency, asymmetric traffic
Energy efficient, low complexity MAC and upper layers
High security/privacy required for certain applications
Guido Dolmans, IMEC-NL

4. 10 March, 2009
Dual-Radio System
MAIN WBAN TRX RADIO
enable
Wake-up radio
Requirements of hardware event-driven triggered wake-up:
A node should wake up almost instantly when it receives a wake-up packet (low latency QoS)  Wake-up radio not duty cycled
Energy consumption used for channel monitoring with dedicated wakeup receiver should be less than that with cycled main radio.
Performance: Node should not wake up when the event of interest does not happen (‘false alarms’)
Performance: Node should not miss wake-up calls (‘miss detection’)
Guido Dolmans, IMEC-NL

5. PHY 2.4 GHz ISM band with wake-up radios
<month year>
doc.: IEEE <doc#>
10 March, 2009
PHY 2.4 GHz ISM band with wake-up radios
Proposal: ISM band 2.4 – GHz with possible 2.36 – 2.4GHz MBAN extension. Wake-up control channel in the extended part  less false alarms in a clean band. Hardware of two radios can be shared.
Proposal PHY operation: duty-cycled main radio with reliable wake-up scheme for achieving key requirements of IEEE WBAN
Single-radio MAC architecture: a single radio receiver is used for both data communication and traffic monitoring. The corresponding wake-up scheme could be synchronous (e.g. beacon-enable ) or asynchronous (e.g. non beaconed ).
Dual-radio wakeup architecture: adding a ULP wake-up receiver (WuRx) in addition to the main radio so that the main radio could stay in sleep mode if no data communication occurs.
Wakeup overrules MAC in case of strict latency requirements. When buffers are full, enable wake-up, otherwise follow scheduled MAC.
Wakeup overrules MAC in case of high energy efficiency requirements.
Guido Dolmans, IMEC-NL
<author>, <company>

6. Dual Radio: WuRx Enabled WBAN Communication (1)
10 March, 2009
Dual Radio: WuRx Enabled WBAN Communication (1)
Ultra-low power wake-up receivers (WuRx):
A bit-rate scalable (10 kbps – 1 Mbps) OOK wake-up receiver is used to monitor the channel and to identify the wake-up calls.
Fits with asymmetric links  strong wake-up trigger signals  low cost and low power wakeup receiver for body area network nodes.
Always on and power up the main (data) radio when needed, aiming at two QoS requirements: low access latency and low energy consumption.
Guido Dolmans, IMEC-NL

7. Dual Radio: WuRx Enabled WBAN Communication (2)
10 March, 2009
Dual Radio: WuRx Enabled WBAN Communication (2)
Dual-radio (high performance main radio TRX + ULP WuRx) architecture fits perfectly with event-driven applications:
Minimize access latency;
Simplify protocol design;
Improve energy efficiency;
Guido Dolmans, IMEC-NL

8. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
10 March, 2009
Dual Radio: WuRx Enabled WBAN Communication (3)
Dual-radio architecture is superior in that:
Power consumption of data communication scales with network traffic;
Relaxed requirements for synchronization ;
Low access latency;
Relaxed power budget for main radio;
But :
Trade-offs between ULP and performance – could be solved by proper Tx/Rx link-budget;
WuRx sets a lower-bound of power consumption in idle state – could be mitigated by applying duty-cyling to the WuRx;
Co-optimization of MAC/PHY layer is critical in fully exploiting the flexibility offered by dual-radio architecture
Dual-radio architecture makes ease of asynchronous wake-up scheme, thus it fits better to WBAN applications due to the event-driven nature of WBAN;
By careful assignment of link budget the poor sensitivity of the WuRx could be justified by overall power consumption, while proper MAC protocol can enable duty-cycled operation of the WuRx to lower the idle power consumption;
Co-optimization of MAC/PHY layer is critical in fully exploiting the flexibility offered by dual-radio architecture; 8
Guido Dolmans, IMEC-NL 8
<author>, <company>

9. Outline WBAN proposal Conclusions
10 March, 2009
Outline
WBAN proposal
Dual-radio (ISM Main and ISM Wake-up) WBAN Overview
ISM band Transceiver
Wake-up Receiver
Conclusions
Guido Dolmans, IMEC-NL

10. WBAN Transceiver band overview
10 March, 2009
WBAN Transceiver band overview
Proposal: WBAN average radio energy consumption limited to 1 nJ/bit. For 200 kbps, this is equivalent to 200 µW.
This can be achieved (easily) with simple radio structures, e.g. a super-regenerative radio.
OOK transmitter, e.g. 5 MHz channels.
Proposal to use world-wide available ISM band 2.4 – GHz with MBAN extension (2.36 – 2.4 GHz).
Architecture of a super-regenerative receiver
Guido Dolmans, IMEC-NL

11. WBAN Receiver Baseband
<month year>
doc.: IEEE <doc#>
10 March, 2009
WBAN Receiver Baseband
For noncoherent detection:
BER = 10-3  SNR = 11dB
BER = 10-6  SNR = 14dB
Guido Dolmans, IMEC-NL
<author>, <company>

12. Digital Baseband: Matched Filter (1)
<month year>
doc.: IEEE <doc#>
10 March, 2009
Digital Baseband: Matched Filter (1)
It is well-know that the optimum receiver for an AWGN channel is the matched filter receiver.
Square root raised cosine (RRC) filter is used as the matched filter (in pair with the pulse shaping filter at the transmitter).
Digital RRC filter design:
Oversampling rate
Filter order
Roll-off factor
Resolution of filter coefficient
Guido Dolmans, IMEC-NL
<author>, <company>

13. Digital Baseband: Matched Filter (2)
<month year>
doc.: IEEE <doc#>
10 March, 2009
Digital Baseband: Matched Filter (2)
2.5 dB gain is achieved with the matched filter in case of AWGN channel.
2.5 dB
Guido Dolmans, IMEC-NL
<author>, <company>

14. SNR and Receiver Sensitivity (1)
10 March, 2009
SNR and Receiver Sensitivity (1)
For BER=10-3, incoherent OOK modulation, Eb/No= 11 dB magnitude
R/B : ½ for typical modulations. 1 for DSSS
SNR= 8db+ 2db (additional losses)=10 db
Data rate
Noise floor
10 MHz
dBm
10KHz
dBm =
= system BW, twice the data rate for typical modulation schemes
Guido Dolmans, IMEC-NL

15. SNR and Receiver Sensitivity (2)
10 March, 2009
SNR and Receiver Sensitivity (2)
Receiver sensitivity without the addition of Noise Figure (NF):
10 Mbps
10 Kbps
The minimum detectable signal:
MDS= Noisefloor +SNR +NF
+Fade Margin+ L
Transmit power, PT: -10 dBm, 0 dBm, 10 dBm.
GTX and GRX are the transmit and receiver antenna gain: 0-3 dBI
Fade margin 15 dB
Propagation loss, Lfs
Additional Losses-matched filter loss, board/digital losses: L=7 dB
Distance
Lfs
1 m
40 dB
5 m
54 dB
Guido Dolmans, IMEC-NL

16. SNR and Receiver Sensitivity (3)
10 March, 2009
SNR and Receiver Sensitivity (3)
Datarate
Distance Pt NF
Pin
10 MHz 1m
-10dbm
18.9
-72
10dbm
38.9
-52 5m
4.9
-86
24.9
-66
10 KHz
48.9
68.9
34.9
54.9
For 10 MHz data rate
For 1m distance:
For -10dbm transmit power:
MDS= PT -Fade Margin - LFS+ GTX + GRX -L= =-72 dB.
NF target =MDS-Noisefloor –SNR=
= = 18.9 dB
Sensitivity target = -86 dBm
Guido Dolmans, IMEC-NL

17. Outline WBAN proposal Conclusions
10 March, 2009
Outline
WBAN proposal
Dual-radio (ISM Main and ISM Wake-up) WBAN Overview
ISM band Transceiver
Wake-up Receiver
Conclusions
Guido Dolmans, IMEC-NL

18. Dual Radio: benefits for low latencies and high energy efficiency
10 March, 2009
Dual Radio: benefits for low latencies and high energy efficiency
Energy efficiency maximization w.r.t. to the latency requirements for different network settings (Pmiss=Pfalse=0.1)
If the requirements of false alarm and miss detection become stricter curves will become flatter  the scheme with separate wake-up receiver is applicable to more scenarios.
Guido Dolmans, IMEC-NL

19. Wake-Up Transceiver Duty-Cycled Wake-Up
10 March, 2009
Wake-Up Transceiver
Duty-Cycled Wake-Up
(based on IEEE frame structure)
BAN Node (BN)
BAN Network Coordinator (BNC)
Listening
On / at every SFB
On / at every CAP
Sending
On / at CAP when needed
On / at SFB when needed
Full Wake-Up
Listening
Always listen until a wake up signal is received.
Then, perform synchronization at the main radio.
Then, the superframe starts.
Sending
At CAP when SFB is sensed,
Or wait until the SFB is not sensed over the maximum superframe duration.
Only at SFB.
Guido Dolmans, IMEC-NL

20. Data Transfer Model: From BNC to BN
10 March, 2009
Data Transfer Model: From BNC to BN
BNC BN
Initialized by BNC
BNC is on or self triggered to the main radio mode
BN is in the wake up or the main radio mode
First, BNC sends Request-To-Send (RTS) or wake up signal to BN through the Beacon
Second, BN sends ACK
Third, BNC sends data to BN
Fourth, BN sends ACK back if applicable
Beacon
ACK
Data
ACK if applicable
Guido Dolmans, IMEC-NL

21. Data Transfer Model: From BN to BNC
10 March, 2009
Data Transfer Model: From BN to BNC
BNC BN
Initialized by BN
BN is on or self triggered to the main radio mode
BNC is in the wake up or the main radio mode
First, BN senses SFB over the maximum superframe duration. If SFB is not sensed, a wake up signal from BN is sent.
Second, after SFB is sensed, BN sends RTS.
Third, BNC sends ACK.
Fourth, BNC sends data to BN
Fifth, BN sends ACK back if applicable
Wake Up Signal if applicable
Beacon
Data Send Request
ACK
Data
ACK if applicable
Guido Dolmans, IMEC-NL

22. Digital Wakeup Receiver Baseband
<month year>
doc.: IEEE <doc#>
10 March, 2009
Digital Wakeup Receiver Baseband
Matched filter is used to improve the BER performance in case of OOK modulation and AWGN channel (see previous slides).
Manchester code is a line code with self-synchronization performance.
Correlator is used to measure the likelihood between the received address code and the local address code.
Power consumption estimate of the digital wakeup baseband is 6 µW. Analog RF and baseband estimate is 50 µW.
Guido Dolmans, IMEC-NL
<author>, <company>

23. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
10 March, 2009
Wakeup Packet
The wakeup packet consists of a preamble part and an address code part. After specifying the main radio design, another part used for channel configuration can be added at the end of the packet.
The first part of the preamble is used to implement amplitude estimation and timing synchronization.
The second part of the preamble is used to do packet synchronization.
Address code is Manchester encoded to improve robustness.
Guido Dolmans, IMEC-NL
<author>, <company>

24. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
10 March, 2009
Simulation Results
Different address codes are used in the simulation for comparison.
Case 1: PN code is used as address code
Case 2: Walsh-Hadamard sequence is used as address code
Walsh-Hadamard sequence is featured by good cross-correlation performance.
Guido Dolmans, IMEC-NL
<author>, <company>

25. More options than wake-up receivers
10 March, 2009
More options than wake-up receivers
Motivation
Sensor node: extremely tight power budget
Master device: slightly more relaxed power budget
Shifting as much complexity as possible to the master device
Possible Solutions
Temporal Diversity
(oversampling)
Spatial Diversity
(multiple antennas)
Networking Diversity
(multiple routes)
Guido Dolmans, IMEC-NL

26. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
10 March, 2009
Conclusions
Asymmetric link budget: use wake-up radios and receive diversity
2.4 – GHz ISM band with MBAN extension from 2.36 GHz – 2.4 GHz
Cycled main radio: 5 MHz channels, superregenerative architecture TRX
for 1 nJ/bit (200 µW for 200 kbps), NF = 20 dB, Sensitivity = -85 dBm.
Always-on wakeup radio: Low latency and low energy QoS. Power
consumption below 60 µW. Sensitivity = -75 dBm (strong beacons) or
-85 dBm (weak beacons).
Guido Dolmans, IMEC-NL
<author>, <company>