Remote Access and Service Discovery for a Vehicular Public Safety Cognitive Radio
The Virginia Tech Center for Wireless Telecommunications' (CWT) Public Safety Cognitive Radio (PSCR) addresses the radio interoperability issues that plague many of the existing public safety radios — disparate frequency bands, incompatible modulation schemes and lack of active channel detection features. The PSCR allows the operator to scan for active channels, classify the detected channels, connect to any of the recognized waveforms and begin analog audio communication as well as bridge two incompatible waveforms together.
The PSCR, although very useful, unfortunately is not portable enough to be used by public safety officials. The power requirement, processing requirement and equipment is respectively large, hungry and bulky. In this thesis, a possible solution to the portability problem is addressed by installing the PSCR in a public safety vehicle and using a Personal Digital Assistant (PDA) for remote access. The PDA allows the user to remotely scan, classify, talk, and bridge waveforms similar in operation to the PSCR. An ergonomically designed interface masks the channel and modulation selection procedure. This architecture can be extended to offer service to any remotely connected device.
In the second part of this thesis, the concept of remote access is extended to a wide-area wireless public safety network. A public safety network consisting of heterogeneous devices is proposed utilizing a small number of backbone nodes. The major research focus of this section is the algorithm for distributing services across the network. Service discovery is optimized to reduce the overhead of service messages and multiple service distribution techniques are utilized depending on the location of the services. Simulation is performed to evaluate the performance of the service discovery protocol in terms of overhead, dissemination time and scalability. The proposed protocol is determined to be superior to the competition in the overhead and scalability tests.