Analysis of radar detection probabilities in time division duplexed systems

Dynamic Frequency Selection (DFS) is the technology chosen by ETSI, FCC, and Industry Canada to provide unlicensed access for broadband radios in licensed bands. It may be viewed as a basic form of cognitive radio, where broadband radios share spectrum with radar users, and is implemented by the basestation or basestation/subscriber combination. This work looks at the likelihood that a radar pulse burst can be detected in a time-division duplexed (TDD) system with radar detection restricted to the basestation. In such a system, a periodic `quiet time' is enforced. Compared to past assumptions on the structure of the radar and radio transmission, namely that both are random, the results shown here suggest that TDD systems will find it difficult or impossible to achieve current FCC and ETSI requirements with certain frame/schedule durations. We present expressions for the number of detected pulses and simulations that demonstrate the trade-offs of varying the uplink/downlink rate and frame/schedule duration.