| UWB Interference |
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Since the FCC permitted low power UWB emissions between 3.1 and 10.6 GHz in February 2003, a number of companies have developed ultrawideband (UWB) technologies for application in wireless personal area networking (WPAN) to achieve high data rates at short distances (less than 10 meters). This program investigates the interference potential of various UWB waveforms. It is a cooperative research effort with the Freescale subsidiary of Motorola Inc and is a logical extension to previous UWB interference research performed at ITS. In this study, we hypothesize that UWB interference potential can be quantified in terms of UWB signal characteristics. To test this hypothesis, a test system was designed and built to inject UWB signals with known characteristics into a C-band satellite digital television (DTV) receiver and quantitatively measure interference susceptibility via signal quality metrics (e.g., segment error rate, pre-Viterbi bit error rate, and modulation error ratio) taken from various points in the receiver signal processing chain. All interference signals were simulated in software and generated with the vector signal generator. An informal preliminary report was made available in June 2004 to demonstrate our approach to signal generation. Part 1 of the three-part NTIA Report Series entitled "Interference Potential of Ultrawideband Signals" was released in February 2005; it describes the test setup and procedures in detail. Part 2, released in August 2005, provides test results for gated-noise interference to DTV receivers. The specific gating parameters of the interfering signals considered in this report include on-times of 0.01, 0.10, 1.00, and 10.00 µs and fractional on-times of 1.00, 0.50, 0.25, 0.125, and 0.0625. This report demonstrates that DTV susceptibility to gated-noise interference cannot be predicted by interference power characteristics alone. It was found that DTV susceptibility is also dependent on temporal characteristics of the interfering signal and the bandwidth of the DTV receiver. Moreover, high correlation was observed between susceptibility and forward error correction performance of the receiver. Part 3, to be released by the end of 2005, will provide results from tests that measured DTV susceptibility to interference from actual UWB signals. In this experiment, a DTV victim receiver was exposed to Direct Sequence UWB (DS-UWB), dither-pulse UWB (DP-UWB), and Multi-Band OFDM UWB (MB-OFDM) interference. Specific signals considered in this report include DS-UWB with {1320, 440, 220, 110}-MHz pulse repetition frequency (PRF) and 0.58-ns pulse width, DP-UWB with {100, 10, 1, 0.1}-MHz PRF, 0.09-ns pulse width, and 50% dither, and MB-OFDM with combinations of (number of bands (b), number of dwells (d)) that include {(1, 1), (3, 1), (3, 2), (7, 1), (7, 2), (7, 6), (13, 1), (13, 2), (13, 12)}. Results agreed with previous test results for gated-noise interference in that measured DTV susceptibility to UWB interference was dependent on temporal characteristics of the interfering signal and the bandwidth of the DTV receiver. |
