Fig. 1. Examples of mesh routers based on different embedded systems: (a) PowerPC and (b) Advanced Risc Machines (ARM). Mesh clients also have necessary functions for mesh networking, and thus, can also work as a router. However, gateway or bridge functions do Fig. 2. Examples of mesh clients: (a) Laptop, (b) PDA, (c) Wi- Fi IP Phone and (d) Wi-Fi RFID Reader. Fig. 3. Infrastructure/backbone WMNs. Fig. 4. Client WMNs. meshing, since, 1n Client WMNs, the end-users Fig. 5. Hybrid WMNs. Fig. 6. WMNs for broadband home networking. The access points must be replaced by wireless mesh routers with mesh connectivity established Fig. 8. WMNs for enterprise networking. Fig. 10. WMNs for transportation systems. Fig. 11. WMNs for building automation. Disaster) Networking and P2P Communications. For example, wireless networks for an emergency response team and firefighters do not have in- advance knowledge of where the network should be deployed. By simply placing wireless mesh routers in desired locations, a WMN can be quickly established. For a group of people holding devices with wireless networking capability, e.g., laptops and PDAs, P2P communication anytime anywhere is an efficient solution for information sharing. WMNs are able to meet this demand. These Applications illustrate that WMNSs are a superset of ad hoc networks, and thus can accom- plish all functions provided by ad hoc networking. Fig. 12. Multiple-antenna systems. Fig. 13. BWN-Mesh testbed at Georgia Tech. RF LAN module. It provides a convenient plat- form for development of RF radios from the phys- ical layer up to the application layer. The key benefit of the board is that all aspects of the MAC are coded in C language and, therefore, are altered easily for research in queueing, security, power management, MIMO, cognitive radio, and so forth. It also utilizes basic Symbol Technolo- gies’ Wi-Fi test board as the base for modifying board and re-spinning to incorporate new features. CalRADIO-I is evolving into a CalRADIO-II de- velop platform with basic DSP board and multiple RF front-end modules such as 802.11x, 802.16, cell and general RF. This will eventually allow the capability of publishing standards in software/ firmware and hardware. The Broadband and Wireless Network (BWN) Lab at Georgia Institute of Technology has re- cently built a testbed of WMNs, as shown in Fig. 13. The WMN, called BWN-Mesh, consists of 15 IEEE 802.11b/g based mesh routers, among which several of them are connected to the next genera- tion Internet testbed (also available in the BWN Lab) as backhaul access to the Internet. The test- bed consists of laptops and desktops equipped with IEEE 802.11b and IEEE 802.11g cards lo- cated in various rooms on the floor where the BWN Lab resides. By changing the topology of the network, experiments investigating the effects of inter-router distance, backhaul placement and clustering are performed along with mobility experiments using the lantons in the testbed.
