Wireless Token Ring Protocol: QoS for Real-time Ad-hoc Networks

1. Wireless Token Ring Protocol (WTRP)A Medium Access Control Protocol for QoS Aware Wireless Networks Mustafa Ergen, Duke Lee, Ruchira Datta, Jeff Ko, Roberto Attias, Anuj Puri, Raja Sengupta, Starvros Tripakis, and Pravin Variaya

2. Automated Vehicle Platoon Real-time safety critical control over ad-hoc network Vehicles transmit control data in round robin every 20 ms Wireless Quality of Service

3. Merge Lane • Distributed solution • Need wireless QOS • Admission control

4. Motivations for WTRP • Quality of service (real time applications) • Distributed solution (robust against a single node failure) • Flexible topology (token ring can be created with Pico cells) • Safety critical applications (need fast recovery from failure) • No need for clock synchronization (compared to TDMA) • Partial connectivity (hidden terminal problem)

5. Motivations for WTRP • Quality of service (real time applications) • Distributed solution (robust against a single node failure) • Flexible topology (token ring can be created with Pico cells) • Safety critical applications (need fast recovery from failure) • No need for clock synchronization (compared to TDMA) • Works on partial connectivity (no hidden terminal problem)

6. Motivations for WTRP • Quality of service (real time applications) • Distributed solution (robust against a single node failure) • Flexible topology (token ring can be created with Pico cells) • Safety critical applications (need fast recovery from failure) • No need for clock synchronization (compared to TDMA) • Works on partial connectivity (no hidden terminal problem) centralized (802.11 PCF, Bluetooth) distributed (token ring)

7. Motivations for WTRP • Quality of service (real time applications) • Distributed solution (robust against a single node failure) • Flexible topology (token ring can be created with Pico cells) • Safety critical applications (need fast recovery from failure) • No need for clock synchronization (compared to TDMA) • Works on partial connectivity (no hidden terminal problem) 1 2 3 4 1 TDMA

8. Motivations for WTRP • Quality of service (real time applications) • Distributed solution (robust against a single node failure) • Flexible topology (token ring can be created with Pico cells) • Safety critical applications (need fast recovery from failure) • No need for clock synchronization (compared to TDMA) • Works on partial connectivity (no hidden terminal problem)

9. Additional Challenges From Wireless Medium • Partial connectivity (unable to hear all nodes in a ring) • Support for multiple rings • Self-managed admission control • Frequent packet loss, corruption

10. Solutions: Connectivity Table • Each node builds and updates connectivity table that contains information of all stations in its reception range, and transmission order of the nodes in its ring

11. Solutions: Connectivity Table • Each node builds and updates connectivity table that contains information of all stations in its reception range, and transmission order of the nodes in its ring

12. 1. Retransmit TOKEN 0. Transmit TOKEN 2. SET_PRED A F D E Ring Recovery • B fails or moves out of range. • A tries to transmit to its successor (B) a specified number of tries and determine that communication link to B is bad. C A B

13. Solutions: Unique Ring Address • Each ring has unique ring id based on unique MAC address of one of the stations of the ring.

14. Solutions: Unique Priority of Token • Based on ring address and generation sequence number pair. • Station only accept token that has higher priority than the last token that the station has accepted. ring address generation sequence …

15. Token Recovery (Multiple Tokens Resolution) 1 1 2 2 1 1 6 6

16. Token Recovery (Multiple Tokens Resolution) 2 2 1 2 1 6 6 6

17. Token Recovery (Multiple Tokens Resolution) 2 2 2 6 6 1 6 6

18. Token Recovery (Multiple Tokens Resolution) 6 6 2 6 2 2 6 6 At next step Delete token with generation sequence number 2 since the next node has seen token with generation sequence number 6

19. Token Recovery (Multiple Tokens Resolution) 6 6 6 6 2 6 6

20. Token Recovery (Multiple Tokens Resolution) 6 6 6 6 6 6 6

21. Token Recovery (Multiple Tokens Resolution) 6 6 6 6 6 7 7 Token refreshed by owner

22. Token Recovery (Multiple Tokens Resolution) 6 6 6 6 7 7 7

23. Suppose that the owner of the token has failed Token Recovery (Ring Address Resolution) 6 6 6 6 6 6 7

24. Token Recovery (Ring Address Resolution) 6 6 6 6 8 7 8 This node detects that the owner is down and claims the token

25. Token Recovery (Ring Address Resolution) 6 6 8 8 6 8 7

26. Token Recovery (Ring Address Resolution) 8 8 6 8 6 8 7

27. Register 6 QOS Interface High Priority Applications (6) Low Priority Applications (6,3) Wireless Token Ring Protocol (10)

28. Granted Register 6 QOS Interface High Priority Applications (6) Low Priority Applications (6,3) Wireless Token Ring Protocol (4)

29. Granted Handler Register 3 QOS Interface High Priority Applications (6) Low Priority Applications (6,3) Wireless Token Ring Protocol (4)

30. Granted QOS Interface High Priority Applications (6) Low Priority Applications (6,3) Wireless Token Ring Protocol (1)

31. API Front End IP UDP CORE SIMULATOR CORE KERNEL CORE WTRP Software Core WTRP Software Core WTRP Software Core IP Channel Model Driver UDP Implementation SIMULATOR Implementation LINUX KERNEL Implementation http://wow.eecs.berkeley.edu WTRP Deliverables (2001)

32. UDP: Video Streaming

33. Simulation Front End

34. Token Rotation Time Vs. Rotation A 3 A 1 A 2 C B C B C B

35. Fairness

36. Throughput Comparison With 802.11 DCF

37. Conclusions • The wireless token ring protocol (WTRP) is a medium access control protocol for wireless networks in mission critical systems. • It supports quality of service in terms of bounded latency and reserved bandwidth. • WTRP is efficient in the sense that it reduces the number of retransmissions due to collisions. • It is fair in the sense that each station takes a turn to transmit and is forced to give up the right to transmit after transmitting for a specified amount of time. • It is a distributed protocol that supports many topologies since not all stations need to be connected to each other or to a central station. • It can be used with an admission control agent for bandwidth or latency reservations. • WTRP is robust against single node failure. WTRP is designed to recover gracefully from multiple simultaneous faults.

38. Conclusions • The wireless token ring protocol (WTRP) is a medium access control protocol for wireless networks in mission critical systems. • It supports quality of service in terms of bounded latency and reserved bandwidth. • WTRP is efficient in the sense that it reduces the number of retransmissions due to collisions. • It is fair in the sense that each station takes a turn to transmit and is forced to give up the right to transmit after transmitting for a specified amount of time. • It is a distributed protocol that supports many topologies since not all stations need to be connected to each other or to a central station. • It can be used with an admission control agent for bandwidth or latency reservations. • WTRP is robust against single node failure. WTRP is designed to recover gracefully from multiple simultaneous faults.

39. Conclusions • The wireless token ring protocol (WTRP) is a medium access control protocol for wireless networks in mission critical systems. • It supports quality of service in terms of bounded latency and reserved bandwidth. • WTRP is efficient in the sense that it reduces the number of retransmissions due to collisions. • It is fair in the sense that each station takes a turn to transmit and is forced to give up the right to transmit after transmitting for a specified amount of time. • It is a distributed protocol that supports many topologies since not all stations need to be connected to each other or to a central station. • It can be used with an admission control agent for bandwidth or latency reservations. • WTRP is robust against single node failure. WTRP is designed to recover gracefully from multiple simultaneous faults.

40. Conclusions • The wireless token ring protocol (WTRP) is a medium access control protocol for wireless networks in mission critical systems. • It supports quality of service in terms of bounded latency and reserved bandwidth. • WTRP is efficient in the sense that it reduces the number of retransmissions due to collisions. • It is fair in the sense that each station takes a turn to transmit and is forced to give up the right to transmit after transmitting for a specified amount of time. • It is a distributed protocol that supports many topologies since not all stations need to be connected to each other or to a central station. • It can be used with an admission control agent for bandwidth or latency reservations. • WTRP is robust against single node failure. WTRP is designed to recover gracefully from multiple simultaneous faults.

41. Conclusions • The wireless token ring protocol (WTRP) is a medium access control protocol for wireless networks in mission critical systems. • It supports quality of service in terms of bounded latency and reserved bandwidth. • WTRP is efficient in the sense that it reduces the number of retransmissions due to collisions. • It is fair in the sense that each station takes a turn to transmit and is forced to give up the right to transmit after transmitting for a specified amount of time. • It is a distributed protocol that supports many topologies since not all stations need to be connected to each other or to a central station. • It can be used with an admission control agent for bandwidth or latency reservations. • WTRP is robust against single node failure. WTRP is designed to recover gracefully from multiple simultaneous faults.

42. Conclusions • The wireless token ring protocol (WTRP) is a medium access control protocol for wireless networks in mission critical systems. • It supports quality of service in terms of bounded latency and reserved bandwidth. • WTRP is efficient in the sense that it reduces the number of retransmissions due to collisions. • It is fair in the sense that each station takes a turn to transmit and is forced to give up the right to transmit after transmitting for a specified amount of time. • It is a distributed protocol that supports many topologies since not all stations need to be connected to each other or to a central station. • It can be used with an admission control agent for bandwidth or latency reservations. • WTRP is robust against single node failure. WTRP is designed to recover gracefully from multiple simultaneous faults.

43. Conclusions • The wireless token ring protocol (WTRP) is a medium access control protocol for wireless networks in mission critical systems. • It supports quality of service in terms of bounded latency and reserved bandwidth. • WTRP is efficient in the sense that it reduces the number of retransmissions due to collisions. • It is fair in the sense that each station takes a turn to transmit and is forced to give up the right to transmit after transmitting for a specified amount of time. • It is a distributed protocol that supports many topologies since not all stations need to be connected to each other or to a central station. • It can be used with an admission control agent for bandwidth or latency reservations. • WTRP is robust against single node failure. WTRP is designed to recover gracefully from multiple simultaneous faults.