Typical Wireless 
   Networks
  •Base stations connected to wired backbone
  •Mobile nodes communicate wirelessly to base stations
                                                                  2
   Ad hoc Networks
   •Networks without pre-configured infrastructure
     ◦ require no hubs, access points, base stations
     ◦ are instantly deployable
     ◦ can be wired or wireless
               wired                wireless         multi-hop wireless
   •Initially targeted for military and emergency applications
                                                                         3
   IEEE 802.11 Ad hoc 
   Mode
  •IEEE 802.11 already provides support for ad hoc mode
  •Computers can be connected without an access point
  •Only work with single hop
                                                                  4
    Applications of Ad hoc Networks
                                                                                     cc
                                                                                    hhoo
                                                                                   dd  
                                                                                  aa
        Factory Floor                Disaster recovery            Car-to-car communication
        Automation
                                                                                                  5     5
   Characteristics of Ad hoc Networks
  •Heterogeneity ― sensors, PDAs, laptops
  •Limited resources ― CPU, bandwidth, power
  •Dynamic topology due to mobility and/or failure
    ◦ Mobile Ad hoc Networks (MANETs)
                                            B
                                    C
                          A
                                                                  8