WIRELESS MESH NETWORKS Ian F. AKYILDIZ* and Xudong WANG** * Georgia Institute of Technology BWN (Broadband Wireless Networking) Lab ** TeraNovi Tachnologies ** TeraNovi Tachnologies

2 1. INTRODUCTION

3 WIRELESS NETWORKS Wireless Networking Multi-hop Infrastructure-less (Ad Hoc) Hybrid Infrastructure-less (MANETs) Single Hop Cellular Networks Wireless Sensor Networks WIRELESS MESH NETWORKS VANETs Infrastructure-based (APs) Bluetooth802.11

4 WMNs consist of two types of nodes: Mesh Routers and Mesh Clients A wireless mesh router contains additional routing functions to support mesh networking Same coverage as a conventional router but with much lower transmission power through multi-hop communication ARCHITECTURE of WMNs

5 Mesh Routers

6 Zigbee Mesh BWN Lab

7 Mesh Routers

8

9 MESH CLIENTS

10 Network Architecture Classification 1. INFRASTRUCTURE MESHING 2. CLIENT MESHING 3. HYBRID MESHING

11 INFRASTRUCTURE MESHING

12 CLIENT MESHING

13 HYBRID MESHING

14 IEEE Based Mesh Network Wired Network G1G1 G2G2 R1R1 R2R2 R3R3 A1A1 A2A2 A3A3 R i Mesh Point (MP) G i Mesh Point Portal (MPP) A i Mesh Access Point (MAP)

15 CHARACTERISTICS (Required) Multi-hop Wireless Network Multi-hop Wireless Network Support for Ad Hoc Networking Support for Ad Hoc Networking Capability of Self-Forming, Self-Healing, and Self- Capability of Self-Forming, Self-Healing, and Self- Organization Organization Compatible and Interoperable with Existing Wireless Compatible and Interoperable with Existing Wireless Networks Networks

16 CHARACTERISTICS (Typical) Multiple radios and multiple channel systems Multiple radios and multiple channel systems Advanced radio techniques: Advanced radio techniques: Directional and smart antennas, MIMO system, Directional and smart antennas, MIMO system, reconfigurable radios, frequency agile/cognitive reconfigurable radios, frequency agile/cognitive radios, software radios radios, software radios Multiple Types of Network Access (WiMAX, WiFis) Multiple Types of Network Access (WiMAX, WiFis)

17 WMNs vs Ad Hoc Networks Dedicated Routing and Configuration: In ad-hoc networks, end-user devices also perform routing and In ad-hoc networks, end-user devices also perform routing and configuration functionalities for all other nodes. configuration functionalities for all other nodes. However, WMNs contain mesh routers for these functionalities. However, WMNs contain mesh routers for these functionalities.  the load on end-user devices is significantly decreased,  the load on end-user devices is significantly decreased,  lower energy consumption and high-end application capabilities  lower energy consumption and high-end application capabilities End-user requirements are limited  decreases the cost of devices in WMNs End-user requirements are limited  decreases the cost of devices in WMNs

18 WMNs vs Ad Hoc Networks Multiple Radios: * Multiple radios perform routing and access functionalities * Example: One radio  routing between mesh routers Another radio  access to the network from end-users  significantly improves the capacity of the network * These functionalities are performed in the same channel in ad-hoc networks  performance affected !

19 WMNs vs Ad Hoc Networks Mobility: (in ad hoc networks) Routing is realized by end-user devices Routing is realized by end-user devices  the network topology and connectivity depend on the movement of users  Additional challenges on * routing protocols * routing protocols * network configuration and * network configuration and * deployment * deployment

20 WMNs vs Ad Hoc Networks Mobility: (in WMNs) Since mesh routers provide the infrastructure, the Since mesh routers provide the infrastructure, the coverage can be engineered easily. coverage can be engineered easily. While providing continuous connectivity throughout the While providing continuous connectivity throughout the network, the mobility of end-users is still supported, network, the mobility of end-users is still supported, without compromising the performance of the network. without compromising the performance of the network.

21 WMNs vs Ad-Hoc Networks Multihop Multihop Nodes are wireless, Nodes are wireless, possibly mobile possibly mobile May rely on infrastructure May rely on infrastructure Most traffic is user  user Most traffic is user  user Ad-Hoc Networks Wireless Mesh Networks Multihop Multihop Nodes are wireless, Nodes are wireless, some mobile, some fixed some mobile, some fixed It relies on infrastructure It relies on infrastructure Most traffic is user  gateway Most traffic is user  gateway

22 WMNs vs WIRELESS SENSOR NETWORKS Bandwidth is limited (tens of kbps) Bandwidth is limited (tens of kbps) In most applications, fixed nodes In most applications, fixed nodes Energy constraints Energy constraints Resource constraints Resource constraints Most traffic is user-to-gateway Most traffic is user-to-gateway Wireless Sensor NetworksWireless Mesh Networks Bandwidth is high (>1Mbps) Bandwidth is high (>1Mbps) Some nodes mobile, some fixed Some nodes mobile, some fixed Not energy limited Not energy limited Resources are not an issue Resources are not an issue Most traffic is user-to-gateway Most traffic is user-to-gateway

23 * Low up-front costs * Easy incremental deployment * Easy maintenance * Provide NLOS coverage * Wireless AP backbone provides connectivity and robustness which is not always achieved with selfish and roaming users in ad-hoc networks * Take load off of end-users * Stationary APs provide consistent coverage ADVANTAGES OF WIRELESS MESH NETWORKS

24 Applications: Broadband Home Networking Current home network realized through IEEE WLANs Current home network realized through IEEE WLANs –Problem  location of the access points –Homes have many dead zones without service coverage –Site surveys are expensive and not practical –Installation of multiple access points is also expensive and not convenient –Communications between nodes under two different access points have to go through the access hub, not an efficient solution

25 Applications: Broadband Home Networking WMN is the SOLUTION!

26 Applications: Community and Neighborhood Networking Community networks based on cable, DSL and last-hop wireless All traffic must flow through Internet  significantly reduces All traffic must flow through Internet  significantly reduces network resource utilization. network resource utilization. Large percentage of areas in between houses is not covered by wireless services Large percentage of areas in between houses is not covered by wireless services Gateways may not be shared and wireless services must be set up individually, network service costs may increase Gateways may not be shared and wireless services must be set up individually, network service costs may increase Each home has single path to access Internet Each home has single path to access Internet

27 Applications: Community and Neighborhood Networking WMNs can mitigate these disadvantages and provide many applications such as distributed file storage, distributed file access, and video streaming.

28 Applications: Enterprise Networking IEEE WLANs IEEE WLANs –Isolated islands, connections among them are achieved through wired Ethernet –Adding more backhaul access modems only increases capacity locally –Does not improve robustness to link failures, network congestion and other problems

29 Applications: Enterprise Networking WMNs Solutions WMNs Solutions –Multiple backhaul access modems can be shared by all nodes in the entire network –Scalable

30 Applications: Metropolitan Area Networks WMNs provide higher transmission rate than cellular networks WMNs provide higher transmission rate than cellular networks Communication between nodes does not rely on a wired backbone Communication between nodes does not rely on a wired backbone An economic alternative to broadband networking An economic alternative to broadband networking Covers larger area than home, enterprise, building, or community networks Covers larger area than home, enterprise, building, or community networks Higher scalability Higher scalability

31 Applications: Metropolitan Area Networks

32 Applications: Transportation Systems WMNs can extend access from stations into WMNs can extend access from stations into buses, ferries, and trains. buses, ferries, and trains. Convenient passenger information services, remote Convenient passenger information services, remote monitoring of in-vehicle security video, and driver communications. monitoring of in-vehicle security video, and driver communications. Two key techniques are needed Two key techniques are needed –High-speed mobile backhaul from a vehicle to the Internet –Mobile mesh networks within the vehicle.

33 Applications: Transportation Systems

34 Applications: Building Automation Various electrical devices need to be controlled and monitored. Various electrical devices need to be controlled and monitored. Standard wired networks is very expensive Standard wired networks is very expensive Wi-Fi networks can reduce the cost of such networks Wi-Fi networks can reduce the cost of such networks However, Wi-Fis are still expensive However, Wi-Fis are still expensive Low deployment cost of BACnet (Building Automation and Control Networks) with WMNs Low deployment cost of BACnet (Building Automation and Control Networks) with WMNs

35 Applications: Building Automation

36 Application: Broadband Internet Access

37 Qualitative Comparisons for Broadband Internet Access Cable DSL WMAN (802.16) Cellular (2.5-3G) WMNs Bandwidth Very Good Very Good LimitedGood Upfront Investments Very High Low Total Investments Very High Moderate Market Coverage Good Modest

38 Mobile Internet Access Direct competition with 3G cellular systems Direct competition with 3G cellular systems

39 Qualitative Comparisons for Mobile Internet Access Cellular 3G WMNs Upfront Investments LowHigh Geo-locationLimitedGood BandwidthGoodLimited Upgrade Cost LowHigh

40 Applications: Health and Medical Systems Monitoring and diagnosis data need to be processed and transmitted across rooms for various purposes Monitoring and diagnosis data need to be processed and transmitted across rooms for various purposes Large data volume by high resolution medical images, various periodical monitoring information Large data volume by high resolution medical images, various periodical monitoring information Wi-Fi based networks must rely on the existence of Ethernet connections, cause high system cost, complexity and dead spots Wi-Fi based networks must rely on the existence of Ethernet connections, cause high system cost, complexity and dead spots However, these issues do not exist in WMNs However, these issues do not exist in WMNs

41 Applications: Security and Surveillance Systems Security surveillance systems are necessary for enterprise buildings, shopping malls, grocery stores, etc. Security surveillance systems are necessary for enterprise buildings, shopping malls, grocery stores, etc. Still images and videos are the major traffic flowing in the network Still images and videos are the major traffic flowing in the network They demand much higher network capacity than other applications They demand much higher network capacity than other applications WMNs are a good solution for these applications WMNs are a good solution for these applications

42 More Applications Disaster Relief and Emergency Networks P2P Networking

43 Project No : Communications Infrastructure for Electric System Automation ANOTHER APPLICATION: Hybrid Network Architecture for Electrical System Automation –Wireless Automatic Meter Reading (WAMR): Energy consumption statistics Effective billing management Remote activation and deactivation of the customer services

44 Project No : Communications Infrastructure for Electric System Automation ANOTHER APPLICATION: Hybrid Network Architecture for Electrical System Automation –Electric System Monitoring: Equipment (e.g., distribution transformer, feeder, recloser/sectionalizer, capacitor, etc.) monitoring Fast identification of service interruptions and incipient faults Timely restoration of the electric utility services

45 Project No : Communications Infrastructure for Electric System Automation ANOTHER APPLICATION: Hybrid Network Architecture for Electrical System Automation

46 Applications: Layer 2 Connectivity The entire wireless mesh cloud becomes one (giant) Ethernet switch The entire wireless mesh cloud becomes one (giant) Ethernet switch Simple, fast installation Simple, fast installation –Short-term events (e.g., conferences, conventions, shows) –Where wires are not desired (e.g., hotels, airports) –Where wires are impossible (e.g., historic buildings) Internet

47 Qualitative Comparisons Layer 2 Connectivity EthernetWMN Total CostModerateLow-Moderate Mobile Users neededsupport BandwidthGood Very Good Speed/Ease of Deployment Fast/EasySlow/Difficult

48 Critical Factors influencing Network Performance 1. Advanced Radio Techniques Typical Examples: Typical Examples: * Directional and smart antennas * Directional and smart antennas * MIMO systems  (Key Technology for IEEE n) * MIMO systems  (Key Technology for IEEE n) * Multi-radio/multi-channel systems * Multi-radio/multi-channel systems * Reconfigurable radios * Reconfigurable radios More Advanced Technologies (not mature yet for commercialization): * Frequency agile/cognitive radios and * Frequency agile/cognitive radios and * Software radios * Software radios These advanced radio technologies require revolutionary design in These advanced radio technologies require revolutionary design in higher layer protocols, in particular, MAC and routing. higher layer protocols, in particular, MAC and routing.

49 2. Scalability (NW performance degrades with increasing NW size) e.g., throughput degrades with the number of hops. Max. available bandwidth degrades at the rate of 1/2,1/4,1/8 depending on the number of hops; 4 hops away from the sender the max BW becomes 1/16 of the total available BW. Critical Factors Influencing Network Performance

50 3. Mesh Connectivity (for protocol design) 4. Broadband and QoS (end-to-end delay, fairness, delay, jitter, aggregate and per-node throughput, packet loss ratios) 5. Compatibility and Inter-Operability (for mesh and conventional clients; mesh routers must be capable for inter-operation) Critical Factors Influencing Network Performance

51 6. Security (new encryption algorithms, key distribution, secure MAC and routing protocols, intrusion detection, monitoring) 7. Ease of Use (autonomic network, automatic power management, self organization, dynamic topology control, robust to link failures, fast network subscription/user authentication procedure) Critical Factors Influencing Network Performance