Abstract: In a rake receiver, a correlation-value calculation section calculates correlation values between spreading codes and reception signals from an input terminal and outputs the calculated correlation values to a delayed-profile creation section and a difference-history creation section. The delayed-profile creation section determines average correlation values and issues the values as a delayed profile to a path selection section. For each reception timing, the difference-history creation section compares the latest correlation value with a previous correlation value held by the difference-history creation section, to determine a difference history, and issues the difference history to the path selection section. The path selection section rearranges the delayed profile in decreasing order of the average correlation values.

Abstract: Two kinds of user-tailored searchers, narrow-search-range searchers (3, 4) and a wide-search-range searcher (5), are set out of a plurality of groups of searchers in compliance with the features of two kinds of multi-paths in mobile communication, and are used, thereby making it possible to search efficiently with high accuracy and on reduced hardware and software scales.

Abstract: Signals sent from a sender by a code division multiple access communication system are input respectively into first to Mth delay units which are disposed parallel to one another. The correlation is examined in each correlator, and the results of a predetermined number of times of correlation are averaged in each averaging section. Based on this, path detection is carried out in each path detector. The results of path detection are input into a correlator control unit which performs control in such a manner that the number of times of averaging in an averaging section is smaller for a higher correlation value.

Abstract: During inter-frequency HO, an HO destination BTS (2) transmits, in gaps in compressed mode, to an MS (3) in the HO destination frequency, data that are identical to data that are transmitted by the HO origin BTS (1) to the MS (3) in the HO origin frequency. In addition, the MS (3) switches frequencies from the HO origin frequency to the HO destination frequency in the gaps in compressed mode, and the MS (3) thus transmits to the BTS (2) data that are identical to data that are transmitted to the BTS (1) in the HO origin frequency.

Abstract: A mobile station (MS), upon completing monitoring of downlink signals, reports both the completion of monitoring and the time of a transmission gap in which the transmission of uplink training signals is to begin to a base station (BST1) using the HHO origin frequency. The mobile station (MS) transmits the uplink training signals by a transmission power that has been designated beforehand, and the base station (BST1) attempts reception of these signals. When the base station (BST1) receives the uplink training signals, it measures and holds the reception timing and reception SIR at that time, calculates the difference between the reception SIR and a predetermined target SIR that is necessary for obtaining adequate reception quality, and reports this difference to the mobile station (MS) by an ACK signal using the HHO origin frequency. The mobile station (MS), upon receiving the ACK signal, changes the frequency to the HHO destination frequency and begins transceiving.

Abstract: An object of the present invention is to provide a rake receiver and a receiving method for efficiently assigning paths to fingers in a CDMA mobile communication system. In the present invention, a correlation-value calculation section 2 calculates correlation values between spreading codes and reception signals input from an input terminal 1, at all timings at which rake reception is possible, and outputs the calculated correlation values to a delayed-profile creation section 3 and a difference-history creation section 6. The delayed-profile creation section 3 determines average correlation values and issues the values as a delayed profile to a path selection section 4.

Abstract: In a spread spectrum receiver, a first despread signal is produced by a despreading circuit corresponding to a first symbol rate. The despreading circuit is responsive to a command signal for subsequently producing a second despread signal corresponding to the second symbol rate. A symbol rate estimation circuit is provided for estimating, from the first despread signal, the transmitted symbol rate of the spread spectrum signal as one of the first and second symbol rates. If the transmitted symbol rate is estimated as the first symbol rate, the despreading circuit continues producing the first despread signal. If the transmitted symbol rate is estimated as the second symbol rate, the estimation circuit supplies the command signal to the despreading circuit to produce the second despread signal. A decoding circuit decodes the first and second despread signals.

Abstract: A reception path search method and a searcher circuit for use in a CDMA reception device in which a delay profile is generated is provided. The delay profile reflects change of the state of a reception path more appropriately. A fading vector which is subjected to a weighted-averaging is calculated from a delay profile of a vector value obtained in every fixed cycle. A phase angle of the fading vector which is subjected to the weighted-averaging is compared with a phase angle of the fading vector which is subjected to the weighted-averaging calculated previously. An absolute value of difference of both phase angles is within a fixed threshold value. On this occasion, an the in-phase-addition of the delay profile of the above vector value continues. The delay profile which is subjected to the in-phase-addition is maintained. While when the absolute value of the angle difference becomes more than the threshold value, the in-phase added delay profile is subjected to a power-addition to generate a delay profile.

Abstract: Signals sent from a sender by a code division multiple access communication system are input respectively into first to Mth delay units which are disposed parallel to one another. The correlation is examined in each correlator, and the results of a predetermined number of times of correlation are averaged in each averaging section. Based on this, path detection is carried out in each path detector. The results of path detection are input into a correlator control unit which performs control in such a manner that the number of times of averaging in an averaging section is smaller for a higher correlation value. This is because, even when the number of times of averaging is smaller for higher S/N (signal-to-noise ratio), data reliability can be ensured and, at the same time, quicker processing can be realized. This leads to efficient processing in a finger section.

Abstract: A speech coding apparatus which allows a speech decoding apparatus to output a more familiar background noise. The speech coding apparatus includes a voice presence/absence discrimination section, a coding section, a unique word production section, and a data switching section which selectively outputs one of outputs of the coding section and the unique word production section as an output of the speech coding apparatus in response to a result of discrimination of the voice presence/absence discrimination section. The speech coding apparatus further includes an amplitude level discrimination section, a clip processing section and an input switching section. The input switching section selects, when the input speech signal includes voice, the input speech signal, but when the input speech signal includes no voice and a code for updating background noise is to be produced, the input switching section selects the input speech signal after clip processing.

Abstract: A speech transmission method which is applied to a speech coding and decoding system performing VOX (Voice Operated Transmitter) processing. The method can reduce an unfamiliar feeling of background noise to be outputted on the reception side. The method includes the steps of generating a background noise updating signal when a pause period is detected, and calculating a quantized spectrum, a non-quantized spectrum envelope and a quantized spectrum envelope from an input speech signal in the pause period on the transmission side. When a difference between the non-quantized spectrum envelope and the quantized spectrum envelope is larger than a predetermined threshold value, the quantized spectrum is changed and the background noise updating signal is produced based on the changed quantized spectrum.

Abstract: A voice encoder which pauses outputting codewords in accordance with the absence of voice activity. An input aural signal is divided into frames and inputted to the voice encoder. The voice encoder has a voice activity detection circuit for determining at each frame whether voice activity is absent or present, a voice encoding circuit, a background noise update judging circuit for detecting a change in the characteristics of the input aural signal, and a control circuit. If the absence of voice activity is detected, the control circuit causes the frame at that time to be encoded as a background noise frame, and then pauses the operation of the voice encoding circuit. If the presence of voice activity is detected, the operation of the voice encoding circuit is resumed.

Abstract: In a LPC speech signal decoder, background noise is simulated during periods of silence at the transmitting end based upon a background noise frame containing information about the background noise at the sending end. When the silence persists, the transmitter periodically updates the background noise frame previously send by transmitting an updating background noise frame. When an update background noise frame is received, an interpolation is performed so as to make the simulated background noise sound natural to the listener. The interpolation process includes a step of selecting between interpolation spectrum parameters which are produced by the interpolation process and the updated spectrum parameters which are based solely upon the most recent updated background noise frame.

Abstract: In a speech decoding apparatus, a conversion unit converts a received encoded signal into a parameter in units of frames. A memory repeatedly updates and stores the parameter representing a pause state and output from the conversion unit for the pause interval of the speech signal. A synthesis filter coefficient generation unit generates a synthesis filter coefficient on the basis of the parameter read out from the memory. A smoothed filter coefficient generation unit generates a smoothed filter coefficient on the basis of the synthesis filter coefficient output from the synthesis filter coefficient generation unit. The smoothed filter coefficient generation unit generates the smoothed filter coefficient which is smoothed such that the synthesis filter coefficient changes in accordance with a count value of the frames during the predetermined period. A background noise generation unit generates background noise on the basis of the parameter read out from the memory for the pause interval of the speech signal.

Abstract: The disclosure is to eliminate discomforting background noise regenerated at a receive side (viz., a base station) in a mobile radio communications system wherein discontinuous transmission (DTX) is utilized. When speech pause is detected at the receive side, synthesis filter coefficients are produced using a background noise code which has been transmitted from a mobile unit. Subsequently, a Q value of the synthesis filter is measured using the above-mentioned synthesis filter coefficients. If the Q value is larger than a threshold level, each of the filter coefficients is lowered by a predetermined value. Thus, the regenerated discomforting background noise can effectively be reduced.