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In many DSP applications (image and voice processing, baseband symbol decoding in high quality communication channels) several dBs of SNR loss can be tolerated without noticeable impact on system level performance. For power optimization in such applications, voltage overscaling can be used to operate the arithmetic circuitry slower than the critical circuit path delay while incurring tolerable SNR...
Class D amplifiers are becoming the most feasible solution for embedded audio application. However, distortions due to the non-linear nature of switching stage are the main drawback for this amplifier topology. This paper discusses the design and implementation of high fidelity audio class D using sliding mode control scheme. This design method proves to be a cost effective solution for industrial...
This paper presents an evaluation of a subband beamforming scheme for speech enhancement and acoustic echo suppression applications, such as hands-free telephony, internet telephony and video conferencing. The aim of the paper is to study the impact of the different types of subband filter banks on the speech enhancement performance. Results show that the octave band filter banks provide an effective...
Orthogonal frequency division multiplexing (OFDM) is the modulation scheme of choice for digital video broadcasting-handheld (DVB-H), which is required to operate under high mobility conditions resulting in significant Inter-carrier Interference (ICI). To mitigate ICI, several cancellation schemes have been proposed but they require reliable channel information at the receiver which is quite challenging...
Orthogonal frequency division multiplexing (OFDM) is the modulation scheme of choice for digital video broadcasting-handheld (DVB-H) which is required to operate under high mobility conditions resulting in significant Inter-Carrier Interference (ICI). Under these conditions, the conventional one-tap per subcarrier channel estimation and equalization is suboptimal since it does not account for ICI...
In this paper we discuss performance results of a novel real-time closed-loop power amplifier (PA) linearization technique that has originally been proposed by Ahmed and Li. The novel approach performs on-the-fly prediction and measurement of the PA AM/AM and AM/PM non-linearity, stores such non-linear characteristics and calculates their inverse functions in order to pre-distort the base-band amplitude...
This paper addresses adaptive channel estimation for time-varying mobile wireless channels with nonstationary statistics. We presents a reduced complexity adaptive channel estimator based on a set membership filtering approach known as the Optimal Bounding Ellipsoid (OBE) algorithm. To exploit time and frequency domain correlation properties of the channel in an efficient low-complexity way, we allow...
This paper explores the attributes, layering models and objective functions in cross layer designs for mobile ad hoc wireless networks by taking all the statistical characteristics and constraints from the physical (PHY) layer, media access control (MAC) layer and network (NET) layer into consideration. This paper reviews the entire network optimization across all the PHY/MAC/NET layers. At the PHY...
While two-dimensional (2-D) orthogonal variable spreading factor (OVSF) codes were proposed for multicarrier direct-sequence code-division multiple-access (MC/DS-CDMA) systems in order to eliminate multiple-access interference, the number of orthogonal sequences (or code cardinality) was restricted by the number of carrier frequencies. Non-orthogonal 2-D frequency-time-spreading (FTS) codes were then...
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