5/12/2005doc.: IEEE /0334 Submission Ripple: A Distributed Medium Access Protocol for Wireless Mesh Network Presented at the IEEE802.11, , , , , & Interim Meeting, May 2004 by Ray-Guang Cheng Cun-Yi Wang Jen-Shun Yang

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 2 Outline Motivation Lessons Learned from the Nature Our Solution Algorithm of Ripple Protocol An Example Appendix

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 3 Motivation: Collision due to Hidden Node Multi-hop Forwarding

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 4 Motivation: Optimal forwarding Spatial Reuse Distance Source: IEEE P TGs 11-04/0709r2 n n+1 n+2 n+3 n+4 Multi-hop Forwarding

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 5 O bservations Existing MAC mechanisms Random access mechanism Performance degradation caused by Hidden/exposed nodes exponential backoff Performance is severely degraded when the network is heavy loaded Could we have better solutions? Prerequisites Distributed protocol

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 6 Lessons Learned from the Nature Optimum duration Spatial reuse distance Ripple Effect

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 7 Our Solution: Ripple Protocol Approaches Adopts controlled access mechanism To prevent from unintentional frame collisions To eliminate exponential backoff Uses RTS/CTS to prevent from hidden node problem Utilizes spatial reuse to improve utilization

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 8 Our Solution: Ripple Protocol (cont.) Q: What is the optimum network utilization if spatial reuse is utilized? A: TX RX TX RX … Spatial reuse distance 1313

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 9 System Model Targeted Application Environment Wireless backbone (backhaul) system high data rate is provided by mesh links Basic assumption Tree Topology Non-mobile Mesh Points and Mesh AP routing path has been determined One-hop radio coverage Separate channels are assigned for downlink and uplink paths Unidirectional data-frame delivery

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 10 Network Topology ： Tree

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 11 Frame Formats DATA frame: DATA frame carries user information. The time required to transmit the DATA frame is a constant. NULL frame: NULL frame is a DATA frame but carries no information. RTS frame: a node, which has the right to send a DATA frame, will send an RTS frame. CTS frame: the target node that receives an RTS frame will responses a CTS frame. Ready-to-send (RTR) frame: a node, which has the right to receive a DATA frame, will send an RTR frame to the sender if the expected RTS frame is not received. ACK frame: a node receives a DATA frame correctly will response an ACK frame.

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 12 Operational States Transmit (TX) state: a node which is ready to send a DATA frame will enter this state. Receive (RX) state: a node which is ready to receive a DATA frame will enter this state. Listen state: a node which is a hidden node (i.e., CTS frame is overheard) or an exposed node (i.e., RTS frame is overheard) or both will enter this state. Idle state: a node which has interrupted by unexpected conditions during TX, RX, and Listen states will return to this state. The idle state is also the initial state for all nodes.

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 13 Algorithm of Ripple Protocol Basic concept: Sender: send RTS Receiver: send RTR if RTS is not received Child nodes of a cross node are forbidden to send RTS or RTR Downlink: State transition: RX mode  TX mode  Listen mode  RX mode … Current state  next frame behavior RX mode  send RTS Listen mode  send RTR if RTS is not received Child nodes of a cross node cannot send RTR Uplink: State transition: TX mode  RX mode  Listen mode  TX mode … Current state  next frame behavior TX mode  send RTR if RTS is not received Listen mode  send RTS Child nodes of a cross node cannot send RTS

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 14 Topology of an Example Internet … A1A1 A2A2 AiAi … … C1C1 B1B1 B2B2 BjBj D1D1 D2D2 DkDk E1E1 E2E2 EmEm … C 1 : could be a super node Root Node Chain Mode Cross Mode

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 15 Downlink transmission- Chain Mode TX RX TX RX … Spatial reuse distance

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 16 Thank you for you attention!

5/12/2005doc.: IEEE /0334 Submission Appendix

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 18 TX RX Listen Idle Receive DATA Receive RTR or CTS, and wait for SIFS Overhear RTS, CTS, RTR Overhear CTS or RTR Timeout CTS or RTR Timeout Receive RTR or CTS, and wait for SIFS DATA Timeout Overhear RTS, CTS, RTR Receive DATA State Transition Diagram: Downlink

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 19 RX TX Listen Idle Receive DATA Receive RTR or CTS, and wait for SIFS Overhear RTS, CTS, RTR Overhear CTS or RTR Timeout CTS or RTR Timeout Receive RTR or CTS, and wait for SIFS DATA Timeout Overhear RTS, CTS, RTR Receive DATA State Transition Diagram: Uplink

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 20 DATA RTS DATA TX Listen DATA A9A9 A 10 A7A7 A8A8 A5A5 A6A6 A3A3 A4A4 A1A1 A2A2 A 12 A 13 A 11 A 14 RTRACKRTSCTSACKRTSACKRTSRTRCTSACKRTSRTRCTSACKRTSCTSACKRTSCTSACKRTSCTSACKRTSACKRTSCTSACKRTSCTSRTRACKRTSCTSACKRTSCTSACKRTSCTSACKRTSCTSACKRTSCTSACKRTSCTSACKRTSCTSACKRTSCTSACKRTSCTSACKRTSCTSRTRACK CTSACKRTSCTSACKRTSACKRTS Listen RX TX RX TX RX TX RX TXRX TX RX TXRX Listen TX ListenTX RX Listen TXRX TX Listen TXRX TX Listen RX TX Listen RX Listen TX RX TX RX Listen TX RX TXRX Listen TX RX Listen RX TX RX TX Idle time Node “ripple effect” CTS Idle Listen

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 21 Timing Diagram of an Example: Uplink

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 22 Achievements of Ripple Protocol Mitigate performance degradation caused by hidden and/or exposed nodes Flow Control over Multi-hop paths to avoid performance degradation and/or meet QoS goals Coordinating channel access across multiple nodes to avoid performance degradation and/or meet QoS goals in the multi-hop network Traffic prioritization within a WLAN Mesh Mesh link communication coordination Support for admission control Support for multiple classes of traffic Improving Spatial Reuse in a mesh network

5/12/2005 Submission Ray-Guang Cheng, Cun-Yi Wang, and Jen-Shun Yang doc.: IEEE /0334 Slide 23 Ripples Conflict in Cross Node Solution Apply Scheduling Algorithm in cross node to determine the precedence of the cross paths. To root gateway