Abstract: A system for detection of voice activity in a communications signal, employing a nonlinear two filter voice detection algorithm, in which one filter has a low time constant (the fast filter) and one filter has a high time constant (the slow filter). The slow filter serves to provide a noise floor estimate for the incoming signal, and the fast filter serves to more closely represent the total energy in the signal. The absolute value of incoming data is presented to both filters, and the difference in filter outputs is integrated over each of a series of successive frames, thereby giving an indication of the energy level above the noise floor in each frame of the incoming signal. Voice activity is detected if the measured energy level for a frame exceeds a specified threshold level. Silence (e.g., leaving only noise) is detected if the measured energy level for each of a specified number of successive frames does not exceed a specified threshold level.

Abstract: A reduced complexity method of ring signal detection, in which a digital signal processor monitors an incoming data stream for zero crossings and employs a limiter-discriminator to differentiate ring frequency signals from line noise. Controlled noise is injected into the incoming data stream in order to prevent false declarations of ring signals in the presence of low frequency natural noise or low amplitude signals. The method conserves valuable processing power and may therefore prove useful in DSP-based telephone devices that must simultaneously perform multiple processing operations such as ring detection and speech processing.

Abstract: The present disclosure includes a discussion of a bit error rate detection method for use in a digital radio communication system. The digital radio communication system contains multiple radios which transmit and receive radio frequency (RF) signals. The RF signals are formatted into multiple frames, each frame has a predetermined number of data bits, a subset of which have known values. A first frame of data is transmitted. The first frame is received and the subset of known data bits are extracted. Each data bit of the received subset of known data bits are compared to the known set of data bits and a counter is incremented in response to each comparison which results in difference between the received bit and the set of known bits. The counter value is used to determine a bit error rate of the received first frame at a predetermined confidence level.

Abstract: The present patent application includes a discussion of a signal compensation apparatus (119). The apparatus is implemented in a digital radiotelephone (101) having diversity receivers (111, 113). The signal compensation apparatus utilizes three control loops and a branch selection switch circuit to substantially diminish the undesired gain and DC offset present in the selected received data signal. Portions of the apparatus are implemented in a digital signal processor (DSP) (249) for rapid adjustment of the control loops when switching to a different receiver branch.