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A relay diversity scheme is proposed to provide diversity gain and better system performance in wireless fading environment. The hybrid relay diversity (HRD) scheme combines the concept of distributed space-time block coding (DSTBC) and relay cyclic delay diversity (RCDD) for OFDM-based relay communication network with more than one relay nodes. The scheme addresses the issue of achieving maximum...
Time-reversed orthogonal frequency division multiplexing (TR-OFDM) has recently received attention as a promising scheme for supporting single-input multiple-output (SIMO) communications over time-dispersive fading channels. In TR-OFDM, the time reversal processing cleverly converts multiple time-dispersive fading channels associated with SIMO-OFDM into a single channel with generally smaller time...
In this paper bit error rate (BER) performances of the built-in MATLAB multipath fading simulator, which recreates a theoretical channel based on user's specified parameters, have been compared to that of a ‘playback’ based channel simulator. The MATLAB fading simulator has been configured with parameters estimated from the same radio channel measurements used by the ‘playback’ based simulator. The...
In recent years, the performance analysis of UWB (Ultra-Wide Band) systems has been an area of considerable interest. To understand the fading in UWB caused by the multipath propagation in complicated environment of underground mines, a precise model of the channel response is expected for designing a UWB system. This paper presents the comparison between the UWB channel proposed by study group IEEE...
TH (Tomlinson-Harashima) precoding is an important nonlinear precoding method. In this paper, the bit error rate (BER) performance for the TH precoding system is investigated over time varying and dispersive Ricean fading channels. Assuming that there exists a certain delay introduced by the feedback channel, we first model the feedback error of channel station information (CSI) due to the feedback...
It has been shown that due to its smaller signal bandwidth (96 KHz), DRM+ signal could suffer from flat fading degradation at low receiver speeds, particularly in urban environments. To alleviate this problem, a simple transmit delay diversity (TDD) has been proposed in the standard. This paper tries to investigate this issue by presenting the performance results of multipath fading characterizations...
In this paper, the performance of adaptive modulation for multiuser amplify-and-forward relay networks over Nakagami-$m$ fading is studied. Specifically, adaptive discrete rate five-mode $M$-ary quadrature amplitude modulation is employed with fixed switching thresholds. In particular, the detrimental effect of feedback delays in multiuser scheduling is quantified. To this end, an upper bound of the...
Orthogonal Frequency Division Multiplexing (OFDM) is a robust multi-carrier modulation technique for high data rata wired/wireless transmission systems due to its good performance in multi-path channels. In this paper, a chaos-evolutionary programming (CEP) hybrid approach is proposed to achieve a minimum degradation of OFDM transmission over multi-path channels, taking into account, the Doppler effect...
Overlap frequency-domain equalization (FDE) requires no cyclic prefix (CP) insertion. In this paper, a new minimum mean square error (MMSE) weight is derived for the overlap FDE. In the previous paper, the MMSE weight for overlap FDE is derived by approximating the IBI as a white Gaussian variable. However, the IBI is an independent colored noise. We derive a new MMSE weight by taking into account...
The impact of outdated channel state information (CSI) on the performance of variable-rate adaptive M-ary quadrature amplitude modulation (M-QAM) in an amplify-and-forward (AF) opportunistic relaying system over Rayleigh fading channels is analyzed. Closed-form expressions are derived for the average spectral efficiency, outage probability and the average bit error rate under outdated CSI. Using numerical...
To fully exploit frequency diversity in cyclic delay diversity orthogonal frequency division multiplexing (CDD-OFDM) system, accurate channel estimation is crucial. Due to the excessive channel delay spread in CDD, traditional in-band pilot assisted channel estimation with limited frequency resolution fails to track the considerable variation in the frequency domain. Alternatively, increasing pilot...
In this paper, we propose to use the Discrete-Time Rake receiver for Cooperative DS-CDMA systems. We compare the Bit Error Rate (BER) performance of the Continuous Time, Discrete Time and Decorrelating Discrete Time Rake receivers (CTR, DTR, DDTR) using Decode and Forward (DF) relaying. The former receiver is the most used and consists in combining the output of correlators locked on the most significant...
This paper presents the performance analysis of a realistic Smart Utility Network (SUN) system with low duty signaling design. The main focus of this paper is to evaluate the performance of the SUN system based on the specifications in an on-going industrial standardization activity, the IEEE 802.15.4g. For this purpose, a theoretical framework is constructed to model the transceiver with low duty...
Recently, a novel single user weighted-transmitted reference (WTR) system has been proposed for high data rate ultra-wideband (UWB) communications. The WTR system not only achieves a superior performance but also supports high data rates and is robust to variations of both weighting coefficient and integration interval. Furthermore, it extremely reduces the sampling rate in comparison to the existing...
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...
In coding theory, concatenated codes form a class of error-correcting codes that are derived by combining an inner code with an outer code. This is a solution to the problem of finding a code that has both exponentially decreasing error probability with increasing block length and polynomial-time decoding complexity. The work presented in this paper, provides link level performance analysis of non-line...
Linear precoding plays an important role in the spatial multiplexing multiple-input multiple-output (MIMO)-orthogonal frequency-division multiplexing (OFDM) systems which are considered one of the primary candidates for the physical-layer techniques in the next-generation wireless communication systems. It requires the channel state information (CSI) at the transmitter to adapt the transmitted signal...
This paper investigates the performance of delay diversity with subcarrier-based signal phase rotation in an OFDM system. Delay diversity achieves transmit diversity with channel coding by intentionally ingenerating paths which have different delays at a transmitter side. However, the correlation between subcarriers is not always low. The proposed scheme which combines the delay diversity and the...
This paper presents a novel technique to save the transmitting power of spread-spectrum communication systems based on the application of delay diversity. The core idea of this delay-diversity system is to delay two spreading sequences that carry the same information of a bit with respect to each other in order to statistically separate the influence of fading on the same bit in time domain. The theoretical...
This paper examines radio wave propagation in underground and subway environments from the perspective of providing digital radio with multimedia and video enhanced services (DAB/DMB) as a continuity of the same services offered above ground. To this end, a preliminary simulation framework of a DAB/DMB transmission system inside a rectangular subway tunnel is proposed. First, the received power and...
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