Joint Multi-Channel Link Layer and Multi-Path Routing Design for Wireless Mesh Networks Wai-Hong Tam and Yu-Chee Tseng National Chiao-Tung University, Taiwan Chung-Yuan Christian University, Taiwan INFCOM 2007

Outline Introduction Motivation – Four Scenario Scenario Related Work Proposed Algorithm – Assumption – Joint Multi-Channel and Multi-Path Control (JMM) Protocol Performance Evaluation Conclusion

Introduction The algorithm is working in Wireless Mesh Network (WMN). – In places where wired infrastructure is not available A WMN typically has a two-tier architecture – Mesh router: provide end-user to forward traffic – Gateway: provide Internet access

Introduction Difficulty of collision avoidance: In a multi-hop environment, the common phenomena of hidden and exposed terminals cause collision and unfairness, resulting in the reduction of throughput. In this paper, the author proposed an more cost-effective solution by exploiting multi-channels and multi-path control. The goal is to improve network performance.

Motivation The four type scenario discussion: – Single-Channel, Single-Path – Multi-Channel, Single-Path – Single-Channel, Multi-Path – Multi-Channel, Multi-Path

Motivation Single-Channel, Single-Path – The end-to-end throughput at most 1/3 of the effective MAC data rate.

Motivation Multi-Channel, Single-Path – The end-to-end throughput as high as 1/2 of the effective MAC data rate.

Motivation Single-Channel, Multi-Path – The end-to-end throughput as high as 1/3. A B G CDE F J I H

Motivation Multi-Channel, Multi-Path – The end-to-end throughput is better than 1/2 A B G CDE F J I H

Motivation The multi-channel and multi-path will get the better performance.

Related Work Multi-Channel Routing Protocols – AODV Ad hoc On-Demand Vector routing Receiver-based channel assignment A CH1 B CH2CH3 CH2 Data

Related Work ( con.) Multi channel hidden-terminal problem A B CD RTS CH3 CH2 Data CH2 CTS(2) RTS CTS(2) Datacollision Control Channel

Multi channel hidden-terminal problem

Assumption The paper assume that each existing node has already established two paths to its gateway. The paper assume that all nodes on the dual-path except the source have already determined their superframe patterns.

Proposed Algorithm Part1: Multi-channel link layer – Channel scheduling Schedule which channel the transceiver should stay on – Packet scheduling Schedule when a packet can be sent

Proposed Algorithm Part 2:Multi-Path Routing – Receiving channel scheduling Decide the receiving channel Reduce the channel utilizations – Multi-path route scheduling Find Two disjoint Path Path Selection metric – Packet scheduling A function to the packet scheduling

Selection of Receiving Channel AB C S E F G H Y X recv_ch = 3 recv_ch = 2 recv_ch = 3 recv_ch = 1 recv_ch = 2 recv_ch = ? recv_ch = 2 recv_ch = 3 recv_ch = 1 recv_ch = 2 recv_ch = 3 D recv_ch = 1 Neighbor: A:3, B:1, C:2, D:3, E:2, F:3, G:1, H:2, Channel Usage: ch1:2, ch2:3, ch3:3

Dual-Path Route Discovery GREQ

The Procedure of a non-gateway node

AB C S E F G H Y X D Hop_Count: 2 gwAddr = X TF-TF type recv_ch = 2 Hop_Count: 2 gwAddr = X TF-TF type recv_ch = 3 Hop Count: ∞ unknown RF-RF type recv_ch = 1 Hop_Count: 2 gwAddr = Y TF-TF type recv_ch = 2 Hop_Count: 2 gwAddr = Y TF-TF type recv_ch = 3 GREQ(1, S, unknown, ∞, {S} ) Dual-Path Route Discovery

AB C S E F G H Y X D Hop_Count: 2 gwAddr = X TF-TF type recv_ch = 2 Hop_Count: 2 gwAddr = X TF-TF type recv_ch = 3 Hop Count: ∞ unknown RF-RF type recv_ch = 1 Hop_Count: 2 gwAddr = Y TF-TF type recv_ch = 2 Hop_Count: 2 gwAddr = Y TF-TF type recv_ch = 3 GREQ(1, S, unknown, ∞, {S} ) GREQ(1, S, X, 2, {S, D} )GREQ(1, S, X, 2, {S, C} ) GREQ(1, S, Y, 2, {S, E} ) GREQ(1, S, Y, 2, {S, F} )

AB C S E F G H Y X D Hop_Count: gwAddr = X RF-RF type recv_ch = 3 Hop_Count: 2 gwAddr = X TF-TF type recv_ch = 2 Hop_Count: 2 gwAddr = X TF-TF type recv_ch = 3 Hop_Count: 1 gwAddr = Y RF-RF type recv_ch = 1 Hop_Count: 2 gwAddr = Y TF-TF type recv_ch = 2 Hop_Count: 1 gwAddr = Y RF-RF type recv_ch = 2 Hop_Count: 1 gwAddr = X RF-RF type recv_ch = 1 Hop_Count: 2 gwAddr = Y TF-TF type recv_ch = 3 Dual-Path Route Discovery

AB C S E F G H Y X D Hop Count: gwAddr = X RF-RF type recv_ch = 3 Hop Count: 2 gwAddr = X TF-TF type recv_ch = 2 Hop Count: 2 gwAddr = X TF-TF type recv_ch = 3 HopCount: 1 gwAddr = Y RF-RF type recv_ch = 1 Hop Count: 2 gwAddr = Y TF-TF type recv_ch = 2 HopCount: 1 gwAddr = Y TF-TF type recv_ch = 2 Hop_Count: 1 gwAddr = X RF-TF type recv_ch = 1 Hop_Count: 2 gwAddr = Y RF-RF type recv_ch = 3 GREQ(1, S, X, 2, {S, D} ) GREQ(1, S, X, 2, {S, C} ) GREQ(1, S, Y, 2, {S, E} ) GREQ(1, S, Y, 2, {S, F} ) Dual-Path Route Discovery

AB C S E F G H Y X D Hop_Count: gwAddr = X RF-RF type recv_ch = 3 Hop_Count: 1 gwAddr = Y RF-RF type recv_ch = 1 Hop_Count: 1 gwAddr = Y RF-RF type recv_ch = 2 Hop_Count: 1 gwAddr = X RF-RF type recv_ch = 1 GREQ(1, S, X, 1, {S, C, B} )GREQ(1, S, X, 1, {S, C, A} ) GREQ(1, S, Y, 1, {S, E, G} ) Dual-Path Route Discovery GREQ(1, S, Y, 1, {S, E, H} ) GREQ(1, S, Y, 1, {S, F, G} ) GREQ(1, S, X, 2, {S, D} ) GREQ(1, S, X, 2, {S, C} ) GREQ(1, S, Y, 2, {S, E} ) GREQ(1, S, Y, 2, {S, F} ) GREQ(1, S, X, 1, {S, D, A} )GREQ(1, S, X, 1, {S, D, B} ) GREQ(1, S, Y, 1, {S, F, H} )

AB C S E F G H Y X D Hop_Count: gwAddr = X RF-RF type recv_ch = 3 Hop_Count: 1 gwAddr = Y RF-RF type recv_ch = 1 Hop_Count: 1 gwAddr =Y RF-RF type recv_ch = 2 Hop_Count: 1 gwAddr = X RF-RF type recv_ch = 1 GREQ(1, S, X, 1, {S, C, B} )GREQ(1, S, X, 1, {S, C, A} ) GREQ(1, S, Y, 1, {S, E, G} ) GREQ(1, S, Y, 1, {S, F, H} ) Dual-Path Route Discovery GREQ(1, S, Y, 1, {S, E, H} ) GREQ(1, S, Y, 1, {S, F, G} ) GREQ(1, S, X, 2, {S, D} ) GREQ(1, S, X, 2, {S, C} ) GREQ(1, S, Y, 2, {S, E} ) GREQ(1, S, Y, 2, {S, F} ) GREQ(1, S, X, 1, {S, D, A} )GREQ(1, S, X, 1, {S, D, B} )

Selection of Receiving Channel

Path Selection AB C S E F G H Y X D GREQ(1, S, X, 1, {S, C, B} ) GREQ(1, S, Y, 1, {S, E, G} ) GREQ(1, S, Y, 1, {S, F, H} ) GREQ(1, S, Y, 1, {S, E, H} ) GREQ(1, S, Y, 1, {S, F, G} ) GREQ(1, S, X, 1, {S, D, B} ) GREQ(1, S, X, 1, {S, C, A} ) GREQ(1, S, X, 1, {S, D, A} )

Path Selection AB C S E F G H Y X D

Path Selection Metric W_node+W_chl+W_qlty = 1.

Path Selection With Metric AB C S E F G H Y X D ( Wnode = 0.5 Wchl = 0.4 Wqlty = 0.1 ) Vnode =node(P1)+ node(P2)  Vchl = CN(P1)+CN(P2)+δ(P1,P2)  Vqlty = ETX(P1) + ETX(P2) Path 1 Path 2 recv_ch = 3 recv_ch = 2 recv_ch = 3 recv_ch = 1 recv_ch = 2 recv_ch = 3 recv_ch = 1 recv_ch = 2 recv_ch = 3 recv_ch = 1

Path Selection With Metric AB C S E F G H Y X D GREP GREP-AC

Determining Superframe Patterns AB C S E F G H Y X D

Superframe Structure

Determining Superframe Patterns AB C S X D B TF B B RF B TF B RF B TF B ?? Master Path P1 Slave Path P2

Determining Superframe Patterns case1 AB C S X D B TF B B RF B TF B RF B TF B RF B

Determining Superframe Patterns case1 AB C S X D B TF B B RF B TF B RF B TF B RF B

Determining Superframe Patterns case2 A B C S X B TF B B RF B TF B RF B B TF

Determining Superframe Patterns case2 A B C S X B TF B B RF B TF B RF B B TF Contended Link

Vchl = CN(P1)+CN(P2)+δ(P1,P2) δ(P1,P2) = 1 Contended Link

Determining Superframe Patterns Rule AB C S X D |P1| − |P2| is even: If |P1| is odd If |P1| is even The pattern of S’s first part should match on P1. The pattern of S’s second part should match on P2. The pattern of S’s first part should match on P2. The pattern of S’s second part should match on P1.

Determining Superframe Patterns Rule A B C S X |P1| − |P2| is odd: If |P| is odd If |P| is even The pattern of S’s first part should match on P1. The pattern of S’s second part should match on P2. The pattern of S’s first part should match on P2. The pattern of S’s second part should match on P1. Let P be the longer path.

Determining Superframe Patterns AB C S X D B TF B B RF B TF B RF B TF B RF Master Path P1 Slave Path P2 B RF

Pack Scheduling Packet Queue – When packets arrive, we need to allocate them to transmitting slots for transmission.

Pack Scheduling Pack Forwarding Rule – When a source node or a gateway generates a sequence of packets, the node will alternately mark them as to be sent along the master path or along the slave path. – If P = 0, the packet will be forwarded to the first part unicast queues; otherwise, the packet will be sent to the second part unicast queues

Pack Forwarding Rule (C.5) Pack Forwarding Rule

Determining Superframe Patterns AB C S X D B TF B B RF B TF B RF B TF B RF B Packet 1 M = 0 E = 0 D = 0 C = 0 1 M = 1 E = 0 D = 0 C = 0 0 Packet 2 M = 0 E = 1 D = 0 C = 0 0

B. Multi-channel link layer part Example

Route Maintenance Route Maintenance : – When a node discovers a faulty link, it will propagate a Gateway ERR or (GERR) message to all its successors which use this link. Each successor will initiate a new gateway discovery procedure to find a new dual-path. – JMM is also quite resilient to failure Before new paths are found, the other (non-broken) paths can still be used for communication.

Performance Evaluation

Conclusions We first point out that multi-path routing has to be used in concert with multi-channel design to improve end-to-end throughput.

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