1. November 2008
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [ Shared Group Timeslots ]
Date Submitted: [ 10 November, 2008 ]
Source: [ Michael Bahr, Norbert Vicari, Ludwig Winkel ] Company [ Siemens AG ]
Address [ Otto-Hahn-Ring 6, München, Germany ]
Voice:[ ], FAX: [ ], [ bahr at siemens. com ]
Re: [response to Call for Proposals doc 15-08/0373r1]
Abstract: [ Further specification of Shared Group Timeslots from Proposal to IEEE e for wireless sensor/actuator networks applicable for factory automation.]
Purpose: [amending for matching the requirements for factory automation]
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
M. Bahr, N. Vicari, L. Winkel, Siemens AG

2. Shared Group Timeslots
November 2008
Shared Group Timeslots
Michael Bahr (Siemens AG)
Norbert Vicari (Siemens AG)
Ludwig Winkel (Siemens AG)
M. Bahr, N. Vicari, L. Winkel, Siemens AG

3. General Concept IEEE 802.15.4 PHY frames Time Division Multiple Access
November 2008
General Concept
IEEE PHY frames
Time Division Multiple Access
superframe with timeslots of fixed length
shared group timeslots with CSMA
addressing based on timeslot location or short address (1 octet)
modified MAC frame
Roaming capability
M. Bahr, N. Vicari, L. Winkel, Siemens AG

4. Shared Group Timeslots
November 2008
Shared Group Timeslots
one or more continuous timeslots concatenated to a shared group timeslot
more than one device per timeslot
carrier sense multiple access within shared group timeslot
all timeslots in single shared group timeslot  network with carrier sense multiple access
mixture between fixed, deterministic timeslots and shared group timeslots possible
M. Bahr, N. Vicari, L. Winkel, Siemens AG

5. General Structure of Shared Group Timeslot
November 2008
General Structure of Shared Group Timeslot
tSlotStart – tSlotTxOwner: sensor node that owns the slot has exclusive access
tSlotTxOwner – tSlotTxGW: if slot is unused, all sensor nodes can use this slot with modified CSMA/CA access (e.g. retransmissions, management devices)
tSlotTxGW – tSlotEnd: if slot is still unused, gateway can use this slot for announcing the network
M. Bahr, N. Vicari, L. Winkel, Siemens AG

6. November 2008
Usage by Slot Owner
only slot owner (exactly 1 sensor/actuator) allowed to send before tSlotTxOwner
contention free access
acknowledgement via:
group acknowledgement
acknowledged mode (not shown on this slide)
unacknowledged mode
M. Bahr, N. Vicari, L. Winkel, Siemens AG

7. November 2008
Usage by Any Sensor
any sensor/actuator can use the slot if not used by slot owner
contention-based access (modified CSMA/CA)
data frame has to fit into shared group timeslot
acknowledgement via:
acknowledged mode
unacknowledge mode (not shown)
M. Bahr, N. Vicari, L. Winkel, Siemens AG

8. November 2008
Usage by Gateway
if slot is still unused after tSlotTxGW, gateway can send network announcement
used for detection of network activity by new sensors
contention free access
usage of this mechanism is optional
M. Bahr, N. Vicari, L. Winkel, Siemens AG

9. Acknowledgement of Transmission
November 2008
Acknowledgement of Transmission
Group Acknowledgement
only possible for dedicated usage by slot owner
Acknowledged Mode
gateway (actuator) sends acknowledgement frame right after successfully received data frame from sensor/actuator (gateway)
necessary for contention-based transmissions
requires explicit addresses  1 byte addresses are sufficient for 250 sensors
requires 2 additional Rx/Tx-switches
Unacknowledged Mode
always possible
M. Bahr, N. Vicari, L. Winkel, Siemens AG

10. Summary further specification of shared group timeslots
November 2008
Summary
further specification of shared group timeslots
3 specific usage opportunities
dedicated access by slot owner before tSlotTxOwner
contention-based access by all sensors after tSlotTxOwner if slot available (modified CSMA/CA)
network announcement by gateway after tSlotTxGW if slot is still available
different acknowledgment schemes
group acknowledgement for dedicated access by slot owner
acknowledged mode for contention-based access by any sensor
unacknowledged mode
short addresses for acknowledged mode with length of 1 (one) octet
M. Bahr, N. Vicari, L. Winkel, Siemens AG

11. References 15-08/0503r0 Preliminary Proposal for Factory Automation
November 2008
References
15-08/0503r0 Preliminary Proposal for Factory Automation
presentation of preliminary proposal for factory automation at July 08 IEEE e meeting
15-08/0571r1 Proposal for Factory Automation
presentation of proposal for factory automation at September 08 IEEE e meeting
15-08/0572r0 Proposal for Factory Automation
text of proposal for factory automation
M. Bahr, N. Vicari, L. Winkel, Siemens AG