摘要:
A device for providing conferencing communications. The device comprises: a summing circuit for forming a signal sum equal to a sum of signals received from at least three information signal sources along with an echo compensation signal, the signal received from each information source including echoes and the signal sum including an aggregation of such echoes; an adaptive filter having an input and an output, the input being solely responsive to the signal sum and the output being only coupled to the summing circuit, the filter forming the echo compensation signal which is an estimate of the aggregation of echoes; and a low level training sequence generator having an amplitude less than a predetermined level. The adaptive filter has coefficients whose respective values are varied in response to a training sequence comprising a plurality of a priori known values supplied by the low level training sequence generator and the predetermined level is below that of the signal received from the each information source.
摘要:
Briefly, in accordance with one embodiment of the invention, an adaptive equalizer comprises: a digital filter including filter tap coefficients; a slicer; and a filter tap coefficient update block. The filter, slicer and coefficient update block are configured so as to perform at least one burst update of the filter tap coefficients. In accordance with another embodiment of the invention, a method of updating the filter tap coefficients of an adaptive equalizer comprises the step of: performing at least one burst update of the filter tap coefficients.
摘要:
To reduce near-end crosstalk (NEXT) in systems possessing excess bandwidth, a signal is transmitted from a first to a second location. At the second location, the received signal is examined and a characteristic of this signal is determined while the delay provided in the transmit signal path at this location is varied. Based on this examination, a particular amount of delay is introduced into the transmit signal path which reduces NEXT. This process is repeated for each direction of transmission. In the disclosed embodiment, the characteristic of the received signal which is determined is the mean square error and the amount of delay selected is that corresponding to the minimum mean square error.
摘要:
Distortion and instability due to echoes in conference communications is reduced through the use of an echo estimating filter disposed in a conference bridging circuit. This circuit includes a signal combiner which receives information signals from each of the parties in the conference communications and provides an output signal which is a combination of the received information signals and an echo compensation signal. The echo estimating filter provides this echo compensation signal in response to the combiner output signal. Advantageously, the echo estimating filter can be fixed or adaptive. In the latter case, the adaptation can be in response to the received information signals or to training sequences.
摘要:
Provided are an apparatus for reducing clipping noise in a broadband wireless communication system in which a clipping method is used and a method thereof. The method includes, when clipped signals are received, decoding and equalizing the received signals to determine transmitted symbols, comparing the magnitudes of the amplitudes of the determined transmitted symbols with a predetermined reference value, and reconstructing signals using the amplitudes of the transmitted symbols and the phases of the received signals when it is determined that the magnitudes of the amplitudes of the transmitted symbols are greater than the reference value.
摘要:
A new diversity scheme for orthogonal frequency division multiplexing/multi-input multi-output (OFDM/MIMO) systems. The new diversity scheme, i.e., turbo layered space-frequency coded OFDM (TLSFC-OFDM), uses the turbo principle with space hopping (SH). The TLSFC-OFDM system uses a successive interference cancellation (SIC) algorithm to reduce the number of iterations. As a result, this scheme reduces computational complexity. Simulation results show that the SIC-based TLSFC-OFDM system outperforms a conventional OFDM/Horizontal Bell Labs Layered Space-Time (H-BLAST) system using a horizontal coding scheme.
摘要:
Disclosed is a transceiving apparatus and method in which a space frequency block coding (SFBC) technique is applied to the SC-FDE technique. The transceiving method encodes an input signal into frequency-domain blocks so as to output at least two signal blocks in parallel to each other, inserts a cyclic prefix (CP) into the output signal blocks, and outputs the signal blocks through the same sub-channel by means of corresponding antenna.
摘要:
Disclosed is a multicarrier-based wireless communication system including a base station for providing a multiple access service to terminals which filter multitone transmitting signals through filters and transmit the filtered signals. A transmitter of the respective terminals includes a multiplexer for multiplexing an input signal and outputting the signal as a plurality of transmitting signals, at least one filter bank for filtering the plurality of transmitting signals, an inverse fast Fourier transformer for executing inverse fast Fourier transform of the filtered transmitting signals output from the filter bank, and a filter information generator for providing filter information to the filter bank. Since the transmitter of the present invention distinguishes users from each other by a filter and thus no synchronization is required between users, which causes a problem in an uplink of the multicarrier-based wireless communication system, system performance can be expected to be improved.
摘要:
A preprocessing apparatus and method for a transmitter and a receiver to prevent system performance degradation caused by Inter-Channel Interference (ICI) or inter-symbol interference (ISI) in an OFDM system. In the OFDM system using N carriers having different frequency bands and K carriers of the N carriers designated as redundant carriers, the transmitter renders ICI-causing parts to be zeroes in a data frame, when a cyclic prefix is not longer than a channel impulse response. Therefore, the ICI is prevented. The receiver eliminates the ISI involved in a current frame using an interference estimated from a previous data frame. Therefore, noise spread caused by the use of redundant carriers is prevented and system complexity is remarkably reduced.
摘要:
A method and apparatus for transmitting and receiving data by performing an iterative multi-user detection is provided. The apparatus includes: a receives a transmission signal and generates a received signal, the transmission signal being generated by modulating a single carrier signal via a modulation process, specialized for each user, in a wireless communication system; an interference canceled signal generator which generates an interference canceled signal by canceling a signal interference using a demodulated signal with respect to the received signal, the signal interference being caused by an other user; and a demodulated signal generator which generates the demodulated signal by demodulating the received signal via a demodulation process using the interference canceled signal, the demodulation process being specialized for each user, wherein the demodulated signal, which is generated by performing the generating of the interference canceled signal and the generating of the demodulated signal at least once, is adopted as a final demodulated signal.