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Continuous time delta-sigma (CTΔΣ) analog-to-digital converters (ADCs) are capable of sampling at much higher rates than discrete time ΔΣ converters. This makes heterojunction bipolar transistor (HBT) technologies excellent candidates for the implementation of fast CTΔΣ ADCs. Due to linearity considerations, all HBT-based ΔΣ ADCs known to us incorporated a single-bit digital-to-analog converter (DAC)...
This paper addresses the medium access control (MAC) and physical (PHY) cross-layer design of a time-division multiple access protocol (TDMA) where users with good channels are allowed to relay the packets of other users with less favorable conditions. All signals are combined at the central node using signal processing tools in order to achieve diversity. The work is focused on an asymmetrical scenario...
In recent years, Path Computation Element (PCE) architecture has been standardized as a suitable solution for path computation in multi-domain network scenarios. The Traffic Engineering Database (TED) of the PCE is updated with the information of the control plane. However, there is a delay from the PCE replies to a request, until the TED is updated with the network status information. This delay...
This article investigates the efficacy of a joint-design of adaptive modulation and coding (AMC) at the physical (PHY) layer with an adaptive Rmax-truncated selective-repeat automatic repeat request (ARQ) protocol at the medium access control (MAC) layer to maximize the throughput of cooperative amplify-and-forward (CAF) relay networks under prescribed delay and/or error performance constraints. Specifically,...
OFDM signal classification has become an important requirement in many cognitive radios and military systems. Implementing such a requirement under Frequency Selective Rayleigh fading is a challenging task. In this paper, we explore different blind OFDM parameter and channel estimation techniques based on Maximum Likelihood techniques and higher order signal processing to ascertain the reception of...
RAKE receiver is a digital receiver that takes advantage of temporal diversity of a multipath channel in order to increase the average received signal to noise ratio (SNR). In this paper we will analyze the performances of RAKE receiver for ultra wideband system with pulse amplitude modulation and time hopping spreading technique. These ultra wideband (UWB) systems have low duty-cycle and they are...
In this paper, we present an enhanced collision arbitration protocol that operates over multiple antennas in RFID systems. An RFID system consists of a reader and tags, and all tags have to be quickly recognized by a reader. Due to a contention based tag transmission, collision arbitration is a very important issue in tag identification. However, collision always happens in the existing single antenna...
In this paper, We applied CCI canceller to remove multiple access interference in co-channel environment and improved performance of Impulse Radio UWB system. Also, we have evaluated the performance of UWB system with Truncated Type-II Hybrid ARQ scheme for achieving high quality data transmission.
In any two elements of a sensor array with omni-directional receiving elements, the effect of a narrow-band (NB) signal incident on the elements is the same for both of them, except for a phase lag or lead between them. In this paper a numerical algorithm for estimating the delay between the time series acquired by these two spatially separated elements is presented. The method makes use of a first-order...
The Direct Sequence Spread Spectral (DSSS) communication system has been widely used in military and civilian fields because of its high processing gain, strong ant-jamming and anti-probed capacity, and low intercepted probability. In this paper, an efficient blind parameter estimating and detecting algorithm is proposed, which takes advantage of the autocorrelation property of pseudo random code...
New results on the achievable trade-off between the per-node throughput T(n) and the average delay D(n) in a static wireless network of n nodes are presented for physical link models. For links modeled by channels with additive white Gaussian noise with power-law attenuation, a trade-off of only D(n) = ⊖ (n (log n) T(n)) is guaranteed for T(n) = ⊖(n−½). This follows from showing that there is significant...
The paper presents a network simulator specifically designed for the analysis of real-time wireless networks in an industrial control context, and for time-space localization applications. Critical issues associated to physical components are accounted for, together with the performance of the communication channel in an interfering environment. A comparison toward already available simulation schemes...
Inspired by the idea of cross-layer analysis and Network Calculus theory, an analytical model for wireless network, which combines the essential knowledge of both, is proposed in this paper by mapping the characteristic of network layer, link layer and physical layer into concatenation of a sequence of Network Calculus components. In addition, the effect of terminal mobility has been considered in...
In this paper, a cognitive system for link adaptation of Wi-Max physical layer is presented. The proposed cognitive system makes the Wi-Max physical layer adaptive to the wireless channel. It monitors the wireless channel as well as the system performance and then by choosing optimal transmission parameters adapts the physical layer thus maximizing the latter. The cognitive system is based on Support...
Performance of a 60 GHz RoF system employing Single-Carrier signal modulation was evaluated in a typical laboratory environment to understand the impact of channel characteristics. Broadband channel characteristics were measured using a channel sounding technique, and the resulting impact of the characteristics on the performance of the multi-Gb/s RoF system was assessed experimentally. Varying performance...
Recently, several papers have been concentrating on reducing the decoding complexity of high-rate space-time codes. While the research has led to some impressive reductions in decoding complexity, the geometric methods so far used appear to have faced some fundamental limits. In this paper, we study what happens if we let go of the assumption of full diversity and study the possibility of reducing...
There have recently been serious social issues involved in multimedia signal processing such as digital rights management, secure authentication, malicious attacks, and tampering with digital audio/speech signals. Reversible watermarking is a technique that enables these signals to be authenticated and then restored to their original signals by removing watermarks from them. We previously proposed...
In this work, the distributed power allocation problem in universal mobile telecommunication systems (UMTS) is studied under feedback signal-to-noise ratio (SNR) constraints. The sources of uncertainty are assumed to come from the quantization process and measurement noise in the closed-loop system. The power allocation problem is formulated as a reference tracking problem of a pre-defined signal...
Binaural hearing aids use a wireless link to exchange the signals received at each side, allowing the implementation of sophisticated noise-reduction strategies. Although different noise-reduction strategies have been reported for binaural hearing aids, those based on Multichannel Wiener filter (MWF) have been identified to provide the best SNR improvement and output sound quality. The real-time implementation...
Threshold effects in the estimation of parameters of non-linearly modulated, continuous-time, wide-band waveforms, are examined from a statistical physics perspective. These threshold effects are shown to be analogous to phase transitions of certain disordered physical systems. Our main message is in demonstrating that this physical point of view is insightful for understanding the interactions between...
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