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In this paper an analytical approach is presented to determine the impact of frequency offset, timing jitter and additive white Gaussian noise (AWGN) on the bit error rate (BER) performance of a multi-carrier direct-sequence code division multiple access (MC-DS-CDMA) system over a Rayleigh Fading Channel. The analysis developed the pdf (probability density function) at the receiver considering combined...
Wireless location by spread spectrum communication can be severely corrupted by noise. Narrowband noise is the most effective interference that can make measurement signal undetected. In this paper, an adaptive wavelet filter is presented to suppress single and multiple narrowband interferences with additive white Gaussian noise that interferes with spread spectrum signals. The filter uses combinations...
The effectiveness of different diversity combining techniques in improving the bit error rate (BER) performance of a direct-sequence code-division multiple-access (DS-CDMA) system is presented in this paper. The overall performance of a DS-CDMA system is degraded by multipath fading and additive white Gaussian noise (AWGN). To evaluate the degradation, the expression for the conditional BER, conditioned...
The effects of multipath fading and additive white Gaussian noise (AWGN) on the bit error rate (BER) performance of direct-sequence code-division multiple-access (DS-CDMA) systems is studied in this paper. The expression for the conditional BER, conditioned on a given level of fading is derived and then the unconditional BER is evaluated. The BER performance results of the system are evaluated in...
This paper investigates the invariant detection problem of quadrature phase-shift keying (QPSK) direct sequence spread spectrum (DS-SS) signals in additive white Gaussian noise (AWGN). Using the complex Gaussian mixture signal model and invariance principle, we consider the constant-false-alarm-rate (CFAR) invariant detectors and other sub-optimal invariant tests, including the uniformly-most-powerful-invariant...
This paper focuses on optimal detection of quadrature phase-shift keying (QPSK) and binary phase-shift keying (BPSK) direct sequence spread spectrum (DS-SS) signals in additive white Gaussian noise (AWGN) with unknown spreading sequence and other parameters. Using complex Gaussian mixture signal model and invariance principle, we derive constant-false-alarm-rate (CFAR) invariant detectors such as...
Communication countermeasures technique is an important component of contemporary military wireless communication system. In this paper, an anti-jamming receiver, clipper cascaded product-combining receiver (CCPR) has been presented for the fast frequency-hopped binary frequency-shift-keying (FFH/BFSK) spread-spectrum communications system with two typical hostile jamming and the additive white Gaussian...
In this paper, a novel method combining cooperative spectrum sensing with quantized soft decision combining is introduced. In order to allow cognitive radios and cognitive networks to opportunistically use spectrum, it is a prerequisite that the license owner or primary user of the spectrum will not be harmfully interfered and the spectrum band will be vacated as soon as the primary user starts its...
The fractional Fourier transform (FRFT) is one among the most efficient techniques for digital signal processing of linear frequency modulated (LFM) signal applications. Chirp (or LFM) modulation spread spectrum (CMSS) with FRFT technique is employed for demodulation of the multiple access System. The concept of multiple access is based on the use of multiple chirp signals, with different chirp rate,...
It is known that spread spectrum serves no help against white noise, but little literature gives explicit demonstration on this problem. In this paper, two receiver structures for direct-sequence spread spectrum (DSSS) systems are described, the error probabilities for the two receivers are obtained, and the equivalence of the two receivers is studied. It is shown that a system using spread spectrum...
This paper considers blind chip rate estimation of direct sequence spread spectrum (DS-SS) signals in multirate and multiuser direct-sequence code division multiple accesses (DS-CDMA) in channels having slow flat Rayleigh fading plus additive white Gaussian noise. Channel impulse response is estimated by a subspace method, and then the chip rate of each signal is obtained using number of zero crossing...
System capacity of a spread spectrum multiple access communication system is an important design parameter. Capacity of noncoherent synchronous hybrid direct sequence (DS) frequency hopping (FH) multiple access communication system is examined. System operates through the channel with additive white Gaussian noise (AWGN) and employs differential phase shift keying (DPSK) modulation. Its system capacity...
Synchronization process is essential especially in UWB communication system owes to its extremely short transmitted pulse shape and the ultra dense multi-path interference. Acquisition performance decreased rapidly own to serious inter-symbol interference (ISI) caused by those complex channel with relatively large delay spread. An interference resistant adaptive threshold acquisition algorithm (IR-ATAA)...
In this paper, we present the impact of timing jitter on a direct sequence ultra wideband (DS-UWB) system in additive white Gaussian noise (AWGN) and multipath environment. Rake receiver is used to capture the multipath profile. Investigation is performed in ordinary and optimum Rake, each with all Rake (ARake) and selective Rake (SRake). Additionally, the equal gain combining (EGC) maximal ratio...
System capacity of noncoherent synchronous hybrid direct sequence (DS) slow frequency hopping (SFH) multiple access communication system is examined. System operates through the channel with additive white Gaussian noise (AWGN) and employs differential phase shift keying modulation (DPSK). System capacity is analyzed for random signature sequence and frequency hopping pattern, impact of DS code length,...
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