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Although the use of CMA filters to equalize multipath channels for FSK signals is well understood, empirical tests have suggested that in some environments an LMS filter positioned after the demodulator could provide similar performance improvement with lower computational cost. Theoretical analysis of this nonlinear configuration has been hindered by the complex interaction of the system and signal...
Traditional OFDM based transmission system uses Cyclic Prefix (CP) in an OFDM symbol in order to maintain orthogonality of transmission. Present days' Ultra-Wideband (UWB) systems use Multi-Band OFDM (MB-OFDM) techniques for transmission in application like Wireless Personal Area Network (WPAN). UWB based systems are power limited by the regulation of FCC. CP introduces correlation in the transmitted...
OFDM can use frequency band efficiently and has strong characteristic for fading channel. But orthogonality collapse when carrier frequency offset and sample timing offset occur. Sample timing offset is represented as phase rotation and ISI. And Carrier frequency offset is represented as phase rotation and ICI. To compensate those effects, many studies were processed based on frequency domain. In...
LTE (Long Term Evolution) supports QoS (Quality of Service) with several service classes. For each class of traffic, a big difference exists on BER (Bit Error Rate) requirement. This leads to a considerable difference in transmission power for various classes of traffic. In this paper, a novel scheduler is designed and proposed for LTE which supports CoS (Class of Service) with the consideration of...
The focus of this paper is the extension of maximum asymptotic efficiency (MAE) equalization for application to time-varying communication channels. While the asymptotically optimal MAE equalizer is very attractive in its low runtime complexity, it suffers from high (exponential in channel and equalizer length) design complexity. Frequent redesign renders the effective operational complexity of the...
Recently Intra Vehicle Communication received great interest from the automotive industry and Ultra Wideband (UWB) technology considered as one of the potential candidate for this system. Goal of this paper is to compare UWB pulse modulation schemes like time hopping pulse position modulation (TH-PPM), direct sequence pulse amplitude modulation (DS-PAM) and multi-band orthogonal frequency division...
We propose a modified two-stage feedforward carrier recovery algorithm for M-QAM formats that achieves a 3× reduction in computation complexity compared to a single-stage algorithm. When combining with a feedback loop, 5.3-10× computation complexity reduction can be achieved.
In multicarrier systems, cyclic prefix (CP) is introduced between two symbols to mitigate inter block interference (IBI). The CP length should be equal or more than channel impulse response (CIR) to ensure IBI free system. However, in the interest of spectral efficiency, if the CP is chosen to be less than the (worst case) CIR length, then a time domain channel shortening prefilter (CSP) can be used...
Underwater acoustic (UWA) channels pose a significant challenge to multicarrier communication systems. Doppler effects necessitate short block lengths, so that the channel can be approximated as time-invariant, while large delay spreads require long guard intervals to prevent inter-symbol interference. Channel shortening can be used to alleviate this double bind by compressing the received channel...
This paper proposes a cross-layer design (CLD) framework called channel-aware buffer unit multiple access (C-BUMA) for improving wireless local area network (WLAN) performance. In the framework, the radio propagation (i.e. PHY layer) is combined with the medium access control (MAC) protocol for packet transmissions. By sharing channel information with the MAC protocol, the approach reduced unnecessary...
We use simulations to investigate the influence of the value of the differential delay of the Mach-Zehnder interferometer (MZI) demodulator in differential phase-shift-keyed (DPSK) systems when the system is limited by the combined effect of chromatic dispersion and in-band crosstalk. It is found that the dispersion and filtering tolerance improvement which is realized when the delay is less than...
In distributed antenna networks, the received signal from different transmitters can be asynchronous due to the processing or propagation delays. This destroys the space time code properties designed initially for synchronous case. We introduce, in this paper, a new design method to construct optimal-rate delay-tolerant codes from existing synchronous codes for a certain number of delay profiles that...
This article analyzes a comparison of a generic digital communication and a Time Reversal communication systems. The principles and properties of Time Reversal are presented for non-impulsive waveforms. The metrics used to characterize time focusing and the measures used for the simulations are outlined. These measures are used to illustrate how the proposed metrics vary as a function of the bandwidth...
In this paper, we investigate the use of a channel shortening filter (CSF) for multiband orthogonal frequency division multiplexing ultra wideband (MB-OFDM UWB) communication systems. Indoor wideband channels are known as rich scattering environments resulting in potentially large delay spread. When the delay spread exceeds the guard interval length, intersymbol interference (ISI) and intercarrier...
Recent advances in high-speed wireless LANs with physical layer (PHY) rates reaching 600Mbps make them ideal for multimedia applications. It has been shown that efficiency at medium access control (MAC) layer decreases with increasing the PHY rate. To achieve high efficiency, few researches have tried to use aggregation in which few packets are concatenated into a larger frame. The resultant frame...
This paper proposes QARWA (Quality of Transmission Aware Routing and Wavelength Assignment) algorithm to handle dynamic lightpath provisioning in wavelength routed transparent optical networks. Specifically, the QARWA algorithm considers both bit-error rate (BER) and setup delay constraints. In this article, we present and evaluate an enhanced wavelength-assignment solution in the QARWA to handle...
Noncoherent receivers are the practical solutions for impulse radio (IR) ultra-wideband (UWB) systems due to their low-complexity and low-cost implementation. However, this simplicity is achieved at the expense of some performance degradation. In this paper, we propose the utilization of time reversal (TR) technique to improve the performance of a recently presented noncoherent detection scheme, called...
In this paper, a random on-off accumulative transmission (R-OOAT) scheme is proposed to achieve collision-tolerant (CT) media access control (MAC) for asynchronous wireless sensor networks. Unlike conventional MAC schemes that discard packages with collisions at receivers, the CT-MAC extracts the salient information from the colliding signals by using the R-OOAT scheme in the physical layer. Nodes...
The aviation community is currently working on the standardization of data communication systems for the future air traffic management. In this context, the ICAO and EUROCONTROL are working on the standardization of IP-based aeronautical telecommunications network and future radio access technologies, respectively. With this work, for the first time, we integrate L-DACS 1, which is one candidate for...
This paper is aimed to evaluate the effect of feedback delay on the performance of closed loop power control in CDMA System. Even though power control can mitigate the problem fluctuation due to fading, however due to the feedback delay, that advantage is invisible if this parameter is not decreased. Feedback delay is the total time that is taken by the power control from the mobile transmit signal...
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