Showing papers on "Bandwidth expansion published in 2018"

Modified Blind Source Separation for Securing End-to-End Mobile Voice Calls

Abstract: This letter proposes a novel method of a highly secured time domain cryptosystem to provide security for mobile voice calls. Using a modified version of blind source separation (BSS) algorithms, the proposed cryptosystem provides a complete solution for highly secured communications between the two ends of any voice call without the need for modifying the existing mobile network infrastructure. Moreover, this system can be easily connected to any type of mobile equipment. To overcome the bandwidth expansion usually associated with BSS algorithms, the proposed system uses a modified key generation process to limit the bandwidth occupied by the encrypted speech signal. Evaluation of the modified encryption and decryption algorithms proved the validity of these changes for speech signals in terms of signal to noise ratio and residual intelligibility.

A 678- $\mu$ W Frequency-Modulation-Based ADC With 104-dB Dynamic Range in 44-kHz Bandwidth

Abstract: This brief presents a frequency-modulation-based analog-to-digital converter (FM ADC) that takes advantage of the coding gain resulting from bandwidth expansion in the analog domain of FM systems to achieve high dynamic range and incorporates a highly digital demodulation approach for power efficiency. The novel architecture employs a sinusoidal output voltage-controlled oscillator (VCO), a relatively low-resolution successive approximation register ADC to sample signals in the FM domain, and then a digital signal processing FM demodulator to recover high-resolution samples of the VCO’s original analog input. The proposed ADC is implemented in 0.5-mm2 of 65-nm CMOS; it achieves 104-dB DR, 99-dB SNR, and 71-dB SNDR in a 44-kHz bandwidth while dissipating $678 ~{\mu } \text{W}$ of power. The architecture of the FM ADC leverages analog domain processing for system performance and digital domain processing for lower power. This novel approach presents a viable alternative to delta-sigma converters for high dynamic range conversion in advanced process nodes.

Training method of voice bandwidth expansion model and voice bandwidth expansion method

Abstract: The invention discloses a training method of a voice bandwidth expansion model and a voice bandwidth expansion method, wherein the voice bandwidth expansion method comprises the following steps: acquiring to-be-expanded narrowband voice; calculating an amplitude spectrum and a phase spectrum of the to-be-expanded narrowband voice, and extracting auxiliary characteristics of the to-be-expanded narrowband voice ; processing the amplitude spectrum and the auxiliary characteristics of the to-be-expanded narrowband voice by virtue of the voice bandwidth expansion model which is obtained from training, so that the amplitude spectrum of a reconstructed bandwidth voice high-frequency band can be obtained; conducting mirror image reversing on the phase spectrum of the to-be-expanded narrowband voice in a frequency domain, and determining the phase spectrum of the bandwidth voice high-frequency band; and on the basis of the amplitude spectrum and the phase spectrum of the narrowband voice, and in combination with the amplitude spectrum and the phase spectrum of the reconstructed bandwidth voice high-frequency band, determining a bandwidth voice signal. With the application of the voice bandwidth expansion method provided by the invention, an effect of improving the tone quality and naturalness of the narrowband voice can be achieved.

Linearization of Wideband Wi-Fi Power Amplifiers Using RF Analog Memory Predistortion

Abstract: Nonlinearity of wideband power amplifiers with memory effects not only limits the performance of digital predistortion, but also challenges the hardware implementation of the digital-to-analog conversions because of the bandwidth expansion up to 5 times bandwidth of the original baseband signal after the predistortion. For wider bandwidth Wi-Fi applications such as the IEEE 802.11ac with a bandwidth of 40 or 80 MHz, PA memory effects have become more prominent and memoryless predistortion has limited effectiveness in suppressing spectral regrowth. In this paper, we improve the accuracy of a memory polynomial (MP) model for a wideband power amplifier (PA) through measurements on a 20 MHz bandwidth input signal with an interpolation method. With this MP model for the PA, an accurate RF analog MP predistorter (PD) is used to compensate both nonlinear properties and memory effects of the actual PA when the PA runs in a saturated or close to a saturated region for improving energy efficiency. The simulated results show that the performance of the MP predistortion model is robust against nonlinearity and memory effects of the actual wideband PA.

Adaptive MMSE-SVD to Improve the Tracking Ability Against Fast Fading

Abstract: Multi-User Multiple Input Multiple Output (MU-MIMO) can significantly increase the link capacity without bandwidth expansion. One promising technique is MMSE-SVD, which is a combination of minimum mean square error (MMSE) filter at the base station (BS) side and eigenmode filter generated by singular value decomposition (SVD) at user equipment (UE) side. MMSE-SVD requires BS and UEs to share the MIMO channel state information (CSI) prior to data transmission. This may cause a serious problem in a high mobility environment; the shared MIMO CSI becomes outdated and consequently, the bit-error rate (BER) performance degrades. In this paper, we propose an adaptive MMSE-SVD, which updates the transmit filter using channel prediction and the receive filter using decision-feedback channel estimation. The uncoded BER performance of adaptive MMSE-SVD for orthogonal frequency division multiplexing (OFDM) downlink and single-carrier (SC) uplink is evaluated by computer simulation. Simulation results confirmed that adaptive MMSE-SVD increases the allowable maximum Doppler frequency ( $\boldsymbol{f}_{\mathbf{D}}\boldsymbol{T}$ ) for keeping $\mathbf{BER} by about 4 times for OFDM downlink while by about 1.6 times for SC uplink.

Bandwidth expansion method and system based on self-adaptive bandwidth judgment

Abstract: The invention discloses a bandwidth expansion method based on self-adaptive bandwidth judgment. The method comprises the following steps: (1) according to the set input sampling rate and output sampling rate of a voice signal, carrying out sampling rate conversion on the input voice signal x(n), and outputting a signal y(n), wherein the sampling rate is the output sampling rate; (2) calculating the frame energy value of the signal y(n), sequentially carrying out low-pass, band-pass and high-pass filtering processing on the signal y(n), calculating the ratio of the frame energy value of the treated signal to the signal y(n), comparing the ratio with the corresponding threshold value, thus judging that whether the effective frequency bandwidth of the signal exists or not, further judging that whether the bandwidth expansion needs to be carried out on the signal y(n) nor not according to the judging result, if the bandwidth expansion is needed, moving to the step (3), otherwise, directlyoutputting the input signal y(n); and (3) carrying out bandwidth expansion on the signal y(n), and then carrying out outputting. For the method and a system provided by the invention, the expansion for the voice bandwidth is steadily realized under the condition with variable sampling rate and variable bandwidth.

A Novel Interpolation Method for Polar Signals in Radio Frequency Transmitters

Abstract: This contribution describes an arbitrary sampling rate converter architecture for the generation of the modulation signals in polar radio frequency transmitters. The design utilizes a novel look-up table-based interpolation method, which is adaptively employed when certain signal trajectory conditions apply and which allows to deal with the bandwidth expansion inherent to polar signals. Simulation results are presented, which compare the performance of the described architecture to conventional interpolator designs.

A Wideband Mixed-Signal Predistorter for Small-Cell Base Station Power Amplifiers

Abstract: A novel low-power wideband mixed-signal approach to linearize RF power amplifiers (PAs) is presented. The proposed mixed-signal predistorter (MSPD) is based on FIR memory polynomial (FIR-MP) model, where digital FIR filter improves the memory correction performance without any bandwidth expansion and the MP predistorter in analog baseband provides superior linearization. MSPD avoids 5X bandwidth requirement for the transmitter and the power-hungry RF components when compared to digital predistorters (DPDs) and analog-RF predistorters (ARFPDs), respectively. This makes the MSPD solution a very low-power candidate and especially attractive in the context of small-cell base stations. Extracted PA model of a commercial 1 W GaAs HBT PA is linearized over an 80 MHz signal; results prove that the FIR-MP based MSPD in ideal system-level simulations provides an improvement of 14.3 dB and 13.5 dB, in adjacent and alternate channel leakage ratio, ACLR1 and ACLR2, respectively, in comparison with FIR envelope memory polynomial (FIR-EMP) model, used in ARFPD. The impact of various non-idealities are simulated at electrical-level to derive the requirements for the integrated circuit implementation shows that a resolution of 8 bits for the coefficients and a signal path SNR of 60 dB is required to achieve ACLR1 above 45 dBc, with as little as 9 coefficients in the analog domain.

Flat Bandwidth Expansion for Spin-Valve GMR Magnetic Field Sensors

Abstract: The solid-state magnetic field sensors developed in recent years are transducers that convert magnetic fields under test into digital or analog voltage outputs. [1] The system consists of the front-end sensing element and the rear-end signal processing unit. The key performances of magnetic field sensor are demonstrated by its sensitivity, noise, linear range, and frequency bandwidth. The ultimate frequency response and noise behavior of the sensing system are determined by the driving method for the front-end sensing element. For quasi-static geomagnetic applications, flipping or modulation techniques is used to minimized the hysteresis for high accuracy measurement of DC field [2], but the available flat bandwidth is limited to less than one tenth of modulation frequency [3]. In contrast, a flat bandwidth over 30 kHz is observed for the DC-field-biased GMR sensor with a magnetic field feedback [4], which is ideal for high frequency applications, e.g. eddy-current sensing. However, the output under a DC-biased field is hysteretic and hence it is not suitable for DC measurement. For industry and high-end consumer applications, a magnetometer with a large bandwidth is necessary for mixed AC and DC measurement. A straight forward implementation of high bandwidth DC/AC magnetometer is to combine the DC sensor with and an AC induction coil [5], [6]. However, the hybrid magnetometer of this kind has a feature size much larger than the solid-state sensor in it. In addition, the output levels for the two element sensors could be very different, inducing more complexity in signal processing. In this work, we explore the flat bandwidth expansion technique using two spinvalve GMR magnetic field sensors driven by different schemes, i.e. field modulation and DC-field-bias. Fig.1 shows the block diagram for the analog signal processing of the system. The low-frequency GMR sensor (LF sensor) is driven by AC magnetic modulation field to achieve high linearity and low hysteresis. A low-pass filter is used to extract the DC output induced by the nonlinear voltage-field relation of spin valve. In this way, the complexity of driving circuit with the inclusion of synchronous detection is avoided. The high-frequency GMR sensor (HF sensor) driven by a DC magnetic field bias has higher hysteresis in the low frequency range, but it exhibits high sensitivity and good linearity for high frequency field measurement. The LF sensor is suitable for detection of DC and low frequency magnetic field, while the HF sensor is capable of AC measurement at higher frequencies. The combined sensor output of the system has a wide bandwidth and is suitable for both DC and AC measurement. To combine the output of the two sensors, the output of HF sensor is high-pass (6 dB/oct) filtered at 100 Hz, and the output of LF sensor is low-pass (6 dB/oct) filtered at 100 Hz. The amplifier gains of the two outputs are fine tuned to achieve a uniform sensitivity, and the two outputs are combined with a summing amplifier. The observed outputs of LF and HF sensors as well as the combined signals are shown in Fig. 2. It was found that the front-end sensitivities are 9.8 V/T for LF sensor and 251 V/T for HF sensor. The total sensitivity of the combined GMR sensing system is 2312 V/T with the total amplifier gains of 500 for the LF sensor and 20 for the HF sensor, supply voltage is 0.69 V for LF sensor and 2.61 V for HF sensor. The linearity error of the combined output signal is 2.2% within the ± 4μT range. The field noise spectral density is 65 nT$/ \surd $ Hz at 1 Hz. The output of summing amplifier is well consistent with theoretical values predicted by numeral calculations from the circuit model. The flat bandwidth of the combined output is expanded to the range from DC to above 10 kHz. The maximum deviation of normalized sensitivity is 1.7% at 100 Hz and the 3-dB flat bandwidth is 40 kHz. The phase lag of the combined output changes slowly to from 0° to - 15° with an increasing frequency from 1 Hz to 1 kHz. The phase lag increases to -130° at 10 kHz and becomes random at frequencies above 100 kHz. Further improvement in the uniformity of frequency response is possible by optimizing the circuit parameters of low-pass and high-pass filters to fine tune their characteristic frequencies and gains. The observed frequency response of our system surpasses the existing GMR sensing systems reported by Tyler et al. [7], for which the 5% flat bandwidth is 530 Hz, and 10% flat bandwidth is 1.515 kHz. Our system exhibited a 5% flat bandwidth of 1.7 kHz and a 10% flat bandwidth of 8.3 kHz, while the response to quasi-static sweeping field at frequencies below 0.1 Hz shows negligible hysteresis. The broad bandwidth of our system makes it suitable for detecting the DC and AC magnetic fields in nondestructive evaluation [4]. It is also suitable for monitoring the environmental field in transient motion tracking with the software gyroscope [8] consisting of magnetic sensor and accelerometer. This work is supported by the Ministry of Science and Technology of Taiwan under Grant No. MOST MOST 105-2221-E-151-038.Fig. 1.Schematics of the signal processing unitFig. 2.Normalized sensitivity of LF sensor, HF sensor, and combined output of two sensors. Brown: LF sensor, Purple: HF sensor, Blue: Output of summing amplifier.

Analysis on Multiple Access Capability of Hybrid Spread Spectrum System with Optimal Sequences - A Review of Performance Parameters Trade-off

Abstract: The performance analysis of hybrid direct- sequence/frequency-hopped spread spectrum multiple-access communication system over additive white Gaussian noise chan- nels in asynchronous environment is reviewed. Binary phase shift keying is considered as base modulation for data signals. Random binary signature sequences as spreading codes and hopping patterns are employed. Several numerical results and graphs help in determining the optimal tradeoff between various performance parameters of the hybrid spread spectrum multiple access (HSSMA) system. Multiple access capability of the system is examined with respect to transmission of maximum simultaneous signals and corresponding error probability. It is devised that under the identical bandwidth expansion and same modulation scheme along with random signature sequences and hoping pattern, the multiple access capability of hybrid spread- spectrum system is considerably better than frequency-hopped spread spectrum (FHSS) system. But under same conditions, directsequence spread spectrum (DSSS) system performance is superior to H-SSMA system. Generation and performance analysis of different types and lengths of pseudo-random binary sequences are discussed in necessary detail, for use in spread spectrum multiple access scenario. Impact of code length, number of available hopping frequencies with respect to total number of users, signal to noise ratio at the particular receiver, variation in hopping speed with respect to data rate and tolerable error probability for the total number of possible simultaneous trans- missions is determined, to achieve optimum performance of the H-SSMA system.

Bandwidth expansion filter and design method thereof

Abstract: The invention provides a bandwidth expansion filter and a design method thereof. The design method of the bandwidth expansion filter comprises the following steps: defining the system loss function ofthe bandwidth expansion filter as the weighted sum of the pass band loss function and the stop band loss function; calculating the pass band loss function and the stop band loss function that minimized the system loss function based on the least square criterion; calculating the order and the weight value required by the bandwidth expansion filter based on the pass band loss function, the stop band loss function and the bandwidth expansion ratio; and confirming the impulse response function of the bandwidth expansion filter based on the calculated order and weight value. The bandwidth expansion filter and the design method thereof provided by the invention can effectively expand the bandwidth of the TI-ADCs system, and can enhance the pass band response performance and suppress the stop band noise.

Optimised periodic precoder-based blind channel estimation for MIMO-OFDM systems

Abstract: In modern wireless communication systems, multiple antennas at transmitter and receiver are employed along with orthogonal frequency-division multiplexing to achieve very high data rate with significant system reliability. To further enhance system performance, blind channel estimation techniques are employed whenever data symbols are transmitted in blocks. These estimation techniques are computationally expensive at almost all signal-to-noise ratio values. In this paper, periodic precoder-based blind channel estimation is used to tackle problems like complexity, channel order overestimation and bandwidth expansion. The system reliability can be improved, if precoder coefficients are chosen in such a way that they have no dependency or minimum correlation with noise coefficients. The overall bit error rate (BER) is derived and simulated with dependency on periodic sequence and channel estimation error. The simulation results shows that the presented precoding scheme performs better in terms of BER...

Design of the equaliser with lower-order Chebyshev polynomial for bandwidth expansion of transmission channel of logging cable

Abstract: This paper introduces the logging cable equaliser. In logging engineering, the seven-core cable has been widely used as transmission medium, which has a narrower effective bandwidth. In order to improve the data transfer rate, it is necessary to expand the effective bandwidth. We have proposed a design method of equaliser based on Chebyshev polynomial in this paper. This scheme could compensate the high-order channel attenuation and expand the effective width with lower-order Chebyshev polynomials. The equaliser could also compensate the phase shift of the transfer data which is caused by the non-linear characteristic of logging cable. We have also simulated the scheme with Matlab and produced the circuit board to demonstrate the practical application effect. It is proved that for the non-linear logging transmission channel, the proposed scheme has a good effect on the expansion of the effective bandwidth. It could provide enough bandwidth to enhance the data transmission rate.

Method and device for adjusting bandwidth on demand

Abstract: The invention discloses a method and a device for adjusting bandwidth on demand The method comprises the following steps: binding different generalized label switched paths (LSPs) between user network interface client (UNI-C) equipment to the same VTE (Virtual TE) link between the UNI-C equipment; and when a generalized LSP in the VTE link has an extra demand on bandwidth, performing bandwidth expansion on the generalized LSP or adding a new generalized LSP meeting the bandwidth demand under the VTE link When an extra bandwidth service needs to be provided by a service layer in a multilayernetwork, the network topology of a client layer can keep constant, and the bandwidth can be adjusted into various granularities according to user demands without being limited to the bandwidth of a single physical link between a UNI-C and a UNI-N (User Network Interface Network)

Method and apparatus for adjusting bandwidth according to requirements, and computer storage medium

Abstract: Disclosed are a method and apparatus for adjusting bandwidth according to requirements, and a computer storage medium The method comprises: binding different universal label switching paths (LSPs) between user network interface-client side (UNI-C) devices to a same VTE link between the UNI-C devices; and when there are additional bandwidth requirements for a universal label switching path in the VTE link, performing bandwidth expansion on the universal label switching path, or adding a universal label switching path meeting the bandwidth requirements under the VTE link

Audio decoder having bandwidth expansion module with energy regulation module

Abstract: FIELD: physics.SUBSTANCE: audio decoder comprises a baseband decoding module, a bandwidth expansion module, and a means for combining a baseband audio signal and a bandwidth expansion audio signal. The bandwidth expansion module comprises an energy regulation module configured in such a way that in the current audio frame, in which the audio frame loss occurs, the adjusted signal energy for the current audio frame for at least one frequency band is set based on the current gain for the current audio frame. The current gain is calculated based on the gain from the previous audio frame or from the bitstream, and based on the estimated signal energy. The estimated signal energy is calculated from the spectrum of the current audio frame of the baseband audio signal. The bandwidth expansion module comprises a gain setting module. The frequency expansion module comprises a noise generator and a signal synthesis module.EFFECT: compensation of decoding errors.15 cl, 5 dwg

A Modified Superimposed Training Scheme for Individual Channel Estimation for Amplify-and-Forward Relay Network

Abstract: In this letter, we deal with the problem of individual channel estimation in amplify-and-forward (AF) relaying systems. A novel superimposed training (ST) scheme is proposed where the relay superimposes its own training sequence directly on top of the received data signal without bandwidth expansion. As a result, the training sequences from the source and relay nodes are independent of each other and can be viewed as a time-multiplexed (TM) mode in the proposed scheme, thus making it more flexible and robust in relay-training design. To remove the data-induced interference and relaying-propagated noise during channel estimation, a modified ST scheme is designed by discarding some relaying data to accommodate the relay-training sequence. Simulation results are presented to assess the performances of the proposed scheme and to obtain the optimal power allocation.