Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title:[Reliable broadcast scheme for PAC networks] Date Submitted: [March 20th, 2014] Source:[Jeongseok Yu, Woongsoo Na, HyoungchelBae, Taejin Kim, Yunseong Lee, Juho Lee, ZeynepVatandas, Sungrae Cho, and JunbeomHur] Company [Chung-Ang University, Korea] E-Mail:[jsyu@uclab.re.kr, wsna@uclab.re.kr, hcbae@uclab.re.kr, tjkim@uclab.re.kr, yslee@uclab.re.kr, jhlee@uclab.re.kr, zvatandas@uclab.re.kr, srcho@cau.ac.kr, jbhur@cau.ac.kr] Re:[] Abstract:[] Purpose:[To provide materials for discussion in 802.15.8 TG] 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. Jeongseok Yu et al., Chung-Ang University

2. Reliable Broadcast Scheme for PAC networks Jeongseok Yu et al., Chung-Ang University

3. Why do we need reliable broadcast? • Before most of broadcast protocol don’t use ACK frame, because broadcast protocol don’t have to satisfy reliable. • In the PAC however, broadcast is necessary for disseminating data for various reasons, e.g., emergency alarm, etc. • Reliability for broadcast might be guaranteed in some applications (e.g., public emergency, hazard notification). -> Reliable Broadcast. Introduction Jeongseok Yu et al., Chung-Ang University

4. Suppose that every receiver node acknowledges (with ACK or NAK) for broadcast data, e.g., The broadcast node will be overwhelmed by acknowledge messages (a.k.a.) ACK/NAK implosion problem. Motivation (1/2) Jeongseok Yu et al., Chung-Ang University

5. This implosion problem also causes the problems of • Unnecessary Collision • Unnecessary Power Consumption • Solution: limit the number of acknowledgements • How?: • Use timers • Timer-based Reliable Broadcast (TRB) Motivation (2/2) Jeongseok Yu et al., Chung-Ang University

6. Transmitter Behavior (when it has broadcast data): • Upstream: If the data is from its child, it does the following in its appropriate schedule: • It broadcasts the data (piggybacked by ACK/NAK) to its children (not siblings), and sets its timer D. • It unicasts the data to its parent and associated neighbors, and sets its timer D. • Downstream: If the data is from its parent • It broadcasts its data to its children (not siblings) and associated neighbors, and sets its timer D. TRB (1/6) Jeongseok Yu et al., Chung-Ang University

7. Transmitter Behavior (when it has broadcast data) • The other cases: If the transmitter is the originator of the data, it does the following in its appropriate schedule: • It broadcasts the data to its children (not siblings), and sets its timer D. • It unicasts the data to its parent and associated neighbors, and sets its timer D. • In all cases, a node that received a broadcast data from other node does not unicast back to that other node. • If timer D expires before receiving feedback (ACK/NAK), it retransmits the original data as above. TRB (2/6) Jeongseok Yu et al., Chung-Ang University

8. Error NAK timer ACK timer • Receiver Behavior (after receiving broadcast data) • When a node receives a broadcast data, it delays its acknowledgement by a random timer described below: • If the received data is erroneous, the node activates a NAK timer. • If the received data is OK, the node activates an ACK timer. • If its timer expires, the node responds (with unicast) its feedback (NAK or ACK) to its transmitter. TRB (3/6) Jeongseok Yu et al., Chung-Ang University

9. αD (NAK Period) (1-α)D (ACK Period) D Broadcast Data Received • NAK timer is generated at random in range of [0, D] while ACK timer is generated at random in range of [D, D]. • Shorter timer for NAK causes early rebroadcast of the original data to fix errors. • Longer timer for ACK is for the case that all nodes successfully received the data. TRB (4/6) Jeongseok Yu et al., Chung-Ang University

10. Transmitter Behavior (after receiving feedback) • Once the transmitter receives a NAK, it retransmits its data as described in Slide 7 to fix the error, and sets its timer D. • When an ACK received, the transmitter transmits its next broadcast data if it has as described in Slide 7, and sets its timer D. TRB (5/6) Jeongseok Yu et al., Chung-Ang University

11. Broadcast Rebroadcast • Receiver Behavior (after receiving rebroadcast data) • The receiver node cancels its timer (NAK or ACK). • This will reduce unnecessary feedbacks to the transmitter. • Based on the result of error detection/correction, the receiver uses NAK/ACK timer. • This series of procedure will continue up to predefined number of times. • Overall behavior will look like as the following for and example: TRB (6/6) Tx ACK NAKs NAK Rx’s Many of receivers will suppress their timer Jeongseok Yu et al., Chung-Ang University

12. @T=, parent(node A) broadcasts. Dotted lines:association relations Downstream Example (1/7) Level N-1 A OK B OK C D Level N OK Level N+1 E F G H I J K L Level N+2 Jeongseok Yu et al., Chung-Ang University

13. @T=+0.75D, nodeB replies with ACK. Downstream Example (2/7) Level N-1 A ACK B C D Level N Level N+1 E F G H I J K L Level N+2 Jeongseok Yu et al., Chung-Ang University

14. Before of afterT=+0.75D, node Cmay forward it to its children. Downstream Example (3/7) Level N-1 A B C D Level N OK Error Level N+1 E F G H I J K L Level N+2 Jeongseok Yu et al., Chung-Ang University

15. @T=+0.8D,node F replies with NAK. About the sametime, node Eforwards the datato its chlidren. Downstream Example (4/7) Level N-1 A B C D Level N NAK Level N+1 E F OK OK OK G H I J K L Level N+2 Jeongseok Yu et al., Chung-Ang University

16. @T=+0.9D,node C rebroadcaststo its children. Node E suppressesits ACK for theprevious broadcastdata, and also ignoresilently therebroadcast data. Downstream Example (5/7) Level N-1 A B C D Level N OK Level N+1 E F ACK G H I J K L Level N+2 Jeongseok Yu et al., Chung-Ang University

17. After T=+0.9D,node F forwardsthe data to its children. Downstream Example (6/7) Level N-1 A B C D Level N Level N+1 E F OK OK OK G H I J K L Level N+2 Jeongseok Yu et al., Chung-Ang University

18. @T=+0.9D,node F replieswith ACK. Downstream Example (7/7) Level N-1 A B C D Level N Level N+1 E F ACK G H I J K L Level N+2 Jeongseok Yu et al., Chung-Ang University

19. @T=, child(node E) of node Cbroadcasts to itschildren. Dotted lines:association relations. Upstream Example (1/4) Level N-1 A B C D Level N Level N+1 E F Broadcast Originator OK OK OK G H I J K L Level N+2 Jeongseok Yu et al., Chung-Ang University

20. @T=, child(node E)unicasts to node C. Upstream Example (2/4) Level N-1 A B OK C D Level N Level N+1 E F ACK G H I J K L Level N+2 Jeongseok Yu et al., Chung-Ang University

21. After T=, node Cbroadcasts datapiggybacked withACK which is ignoredby node F in thisexample. Also, node C unicastsdata to its parent inits appropriateschedule. Upstream Example (3/4) Level N-1 A OK B C D Level N Data/ACK Data/ACK OK Level N+1 E F G H I J K L Level N+2 Jeongseok Yu et al., Chung-Ang University

22. After receivingC’s unicast data,nodes A broadcaststhe data piggybackedwith ACK. Upstream Example (4/4) Level N-1 A Data/ACK Data/ACK Data/ACK B C D Level N Level N+1 E F G H I J K L Level N+2 Jeongseok Yu et al., Chung-Ang University

23. ACK/NAK in reliable broadcast in PAC may cause problems of • Feedback implosion, • Unnecessary collisions, and • Unnecessary power consumption, • Due to unnecessary feedback messages • Timer-based Reliable Broadcast (TRB) algorithm effectively solves the above mentioned problems. Summary Jeongseok Yu et al., Chung-Ang University