doc.: ieee 802.15-08-0024-01-004e submission 11 january, 2008 k. pister and c. kang, dust...

11 January, 2008

K. Pister and C. Kang, Dust NetworksSlide 1

doc.: IEEE 802.15-08-0024-01-004e

Submission

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: [Enhancement to IEEE 802.15.4-2006 for Industrial Markets]Date Submitted: [11 January, 2008]Source: [K. Pister and C. Kang] Company [Dust Networks]Address [30695 Huntwood Avenue, Hayward, CA 94544, USA]Voice:[+1 510 400 2900], FAX: [+1 510 489 3799], E-Mail:[[email protected] and [email protected]]

Re: [n/a]

Abstract: [This document proposes an enhancement to IEEE 802.15.4-2006 MAC Layer for Industrial Markets]

Purpose: [This document is a response to Item a) better support the industrial markets in IEEE P802.15.SG4e Call for Application on 14 November, 2007]

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.

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Time Synchronized Channel Hopping

K. PisterC. Kang

Dust Networks

11 January, 2008

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

GOALS• Increase reliability and robustness required for

Industrial Markets• Multi-channel hopping• Provide efficient multi-channel hopping and enable

longer operational life for battery powered devices– Time Synchronized Time Division Multiplexing

• Simple to co-exist with current 802.15.4 MAC devices• Simultaneous operation in 802.15.4-2006 and Time

Synchronized Channel Hopping modes.• Flexible and scale-able

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

802.15.4 Slot and Superframe timing• Slot length

– When SO = 0 60 symbols 0.96ms• Active superframe duration

– 16 slots 15.36ms when SO=0• Superframe duration

– 15.36ms * 2BO ; BO = 0..14– Up to 4 minutes (> 250,000 msec)

Semi-active

Channel-hopping

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Timeslots and Superframes• Each mote-to-mote

communication happens within a scheduled timeslot

• All timeslots are contained within a superframe

• Superframes repeat in time• Multiple superframes can operate

simultaneously within a networkSuperframe

Unallocated Slot Allocated Slot

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Time Synchronization

Timing – perfect synchronization

A

B RX startup

Transmit Packet: Preamble, SS, Headers, Payload, CRC

RX packet Verify CRC

Calculate ACK CRC

TransmitACK

RX startup or TX->RX

RX ACK

RX/TX turnaround

CCA: RX startup, listen, RX->TX

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Time Synchronization (Cont’d)TgTg


TACKTC

CA

TcrcEarly

Late

PerfectTransmit Packet: Preamble, SS,

Headers, Payload, CRCTACKTC

CA

Tcrc


TACKTC

CA

Tcrc


TC

CA


TC

CA


TC

CA

TgTg

Tslot = 2Tg+Tcomm+TCCA

Tcomm = Tpacket+Tcrc+TACK

Tcrc includes TgACK and all CRC and radio turnaround times. It’s the time from the last bit of the packet to the first bit of the preamble of the ACK.

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Time Synchronization

• Acknowledgement-based Synchronization1. Transmitter node sends a packet, timing at the

start symbol.

2. Receiver timestamps the actual timing of the reception of start symbol

3. Receiver calculates TimeAdj = Expected Timing – Actual measured Timing

4. Receiver informs the sender TimeAdj

5. Transmitter adjusts its clock by TimeAdj

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Time Synchronization (Cont’d)

• Received Packet-based Synchronization1. Receiver timestamps the actual timing of the

reception of start symbol

2. Receiver calculates TimeAdj = TimeExpected (expected arrival time) – Actual timing

3. Receiver adjusts its own clock by TimeAdj

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

CA

DA

B

C

Link = (Time Slot , Channel Offset)

A

Time

Chan.offset

BA

BA

One SlotD

• The two links from B to A are dedicated• D and C share a link for transmitting to A• The shared link does not collide with the dedicated links

BC

FE BE

BF

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Timeslot and Channel Mapping

CA

DA

B

C

A

Slot links for devices

Time

Chan.2.405 GHz

2.470 GHz

…

2.480 GHz

BA

BA

One Slot

2.445 GHz

2.425 GHz

2.475 GHz

2.440 GHz

D

• The two links from B to A are dedicated• D and C share a link for transmitting to A• The shared link does not collide with the dedicated links

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Frequency Hopping

CA

DA

CA

DA

• Each link rotates through k available channels over k cycles.

• Blacklisting can be defined globally and locally.

BA

CA

DA

BA

Time

Ch

ann

el

BA

BA

BA

BA

Cycle N Cycle N+1 Cycle N+2

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Channel Hopping• Need to map (slot, offset) into an 802.15.4

channel– For blacklisting, assume

• Num_channels• LookUp() defines pseudo-random hop

sequence over num_channels• ASN = absolute slot number• Chan = (ASN + offset) % num_channels• 15.4Channel = LookUp(Chan)

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Non-conflicting Timeslot assignment• Devices can be given one or more offsets.OR

• Devices can be given one or more slots in a particular superframe.OR

• Devices can be given a block of (slot,offset)s

Chan.offset

slot

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Non-conflicting timeslot assignment• Devices can be given one or more offsets.

OR• Devices can be given one or more slots in a particular superframe.

OR• Devices can be given a block of (slot,offset)s

0 1 9876542 3 1011 1312 1514

GTS GTS

CAP CFP

Beacon

0 1 9876542 3 1011 1312 1514

GTS GTS

CAP CFP

Beacon

SD=aBaseSuperframeDuration*2SOsymbols

BI=aBaseSuperframeDuration*2BOsymbols

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Non-conflicting timeslot assignment• Multiple superframes with different lengths can operate without conflict

as well.• 4 cycles of the 250ms superframe are shown, along with a 1s

superframe• There are never collisions if the 1 second frame uses only the empty

slots

250ms

1,000ms

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Example of HART Capability

• Data collection– 100 pkt/s per access point channel– 16*100 pkt/s with no spatial reuse of frequency– 105 MPDU bytes per packet assuming 22 bytes of MAC

header, MIC, CRC• Throughput

– 84kbps MPDU bits per second per access point– 15 * 84k = 1.26Mbps combined payload throughput w/ no

spatial reuse of frequency• Latency

– 10ms / PDR (Packet Delivery Rate) per hop– Statistical, but well modeled

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Built-In Flexibility

• Trade performance and power– Sample & reporting rate– Latency– High bandwidth connections

• Tradeoffs can vary with– Time– Location– Events

• Use power intelligently if you’ve got it– Highest performance with powered infrastructure

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Added MAC PAN Service PrimitivesPrimitive Description Re-

questCon-firm

Res-ponse

Indica-tion

SET-SUPERFRAME Add, delete, or modify a superframe X X

ADD-LINK Add a new link X X

DELETE-LINK Delete a new link X X

TDMA-MODE Operate in TDMA mode using superframes and links

X X

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Added MAC MIBAttribute Type Description

SuperframeTableSize Integer Number of entries in the Superframe Table

LInkTableSize Integer Number of entries in the Link Table

RxStartOfPacketTstamp Timestamp Timestamp of receiving the first bit of the packet’s SFD on the PHY

RxEndOfPacketTstamp Timestamp Timestamp of receiving the last bit of the packet from the PHY

AbsoluteSlotNumber long Integer Absolute slot number of current superframe

11 January, 2008


doc.: IEEE 802.15-08-0024-01-004e

Submission

Added SMIB (Structured MIB)

• Link Table: contains all links configured on the device.

• Superframe Table: contains all superframes configured on the device.

doc.: ieee 802.15-08-0024-01-004e submission 11 january, 2008 k. pister and c. kang, dust...

Documents