Abstract: In this paper, we propose a distance estimation scheme
for radar systems using direct sequence ultra wideband (DS-UWB)
signals. The proposed distance estimation scheme averages out the
noise by accumulating the correlator outputs of the radar, and thus,
helps the radar to employ a short-length DS-UWB signal reducing
the correlation processing time. Numerical results confirm that the
proposed distance estimation scheme provides a better estimation
performance and a reduced correlation processing time compared
with those of the conventional DS-UWB radars.
Abstract: Due to side-peaks of autocorrelation function, the binary offset carrier (BOC) signal acquisition suffers from an ambiguity when one of the side-peaks is acquired. In this paper, we first analyze that the BOC autocorrelation is made up of the sum of subcorrelations, and then, remove the side-peaks causing the ambiguity by recombining the sub-correlations. The proposed scheme is shown to remove the side-peaks completely. From numerical results, it is confirmed that the proposed scheme outperforms the conventional schemes in terms of the receiver operating characteristic and mean acquisition time.
Abstract: Due to its capability to resist jamming signals, chirp
spread spectrum (CSS) technique has attracted much attention in
the area of wireless communications. However, there has been little
rigorous analysis for the performance of the CSS communication
system in jamming environments. In this paper, we present analytic
results on the performance of a CSS system by deriving symbol
error rate (SER) expressions for a CSS M-ary phase shift keying
(MPSK) system in the presence of broadband and tone jamming
signals, respectively. The numerical results show that the empirical
SER closely agrees with the analytic result.
Abstract: In this paper, we propose a side-peak cancellation
scheme for code acquisition of composite binary offset carrier
(CBOC) signals. We first model the family of CBOC signals in a
generic form, and then, propose a side-peak cancellation scheme
by combining correlation functions between the divided sub-carrier
and received signals. From numerical results, it is shown that the
proposed scheme removes the side-peak completely, and moreover,
the resulting correlation function demonstrates the better power ratio
performance than the CBOC autocorrelation.
Abstract: In this paper, we propose a novel frequency offset
estimation scheme for orthogonal frequency division multiplexing
(OFDM) systems. By correlating the OFDM signals within the coherence
phase bandwidth and employing a threshold in the frequency
offset estimation process, the proposed scheme is not only robust to
the timing offset but also has a reduced complexity compared with
that of the conventional scheme. Moreover, a timing offset estimation
scheme is also proposed as the next stage of the proposed frequency
offset estimation. Numerical results show that the proposed scheme
can estimate frequency offset with lower computational complexity
and does not require additional memory while maintaining the same
level of estimation performance.
Abstract: Ren et al. presented an efficient carrier frequency offset
(CFO) estimation method for orthogonal frequency division multiplexing
(OFDM), which has an estimation range as large as the
bandwidth of the OFDM signal and achieves high accuracy without
any constraint on the structure of the training sequence. However,
its detection probability of the integer frequency offset (IFO) rapidly
varies according to the fractional frequency offset (FFO) change. In
this paper, we first analyze the Ren-s method and define two criteria
suitable for detection of IFO. Then, we propose a novel method for
the IFO estimation based on the maximum-likelihood (ML) principle
and the detection criteria defined in this paper. The simulation results
demonstrate that the proposed method outperforms the Ren-s method
in terms of the IFO detection probability irrespective of a value of
the FFO.
Abstract: In cognitive radio (CR) systems, the primary user (PU) signal would randomly depart or arrive during the sensing period of a CR user, which is referred to as the high traffic environment. In this paper, we propose a novel spectrum sensing scheme based
on the cyclostationarity of PU signals in high traffic environments. Specifically, we obtain a test statistic by applying an estimate of spectral autocoherence function of the PU signal to the generalized- likelihood ratio. From numerical results, it is confirmed that the proposed scheme provides a better spectrum sensing performance compared with the conventional spectrum sensing scheme based on the energy of the PU signals in high traffic environments.
Abstract: This paper proposes a fast code acquisition scheme for
optical code division multiple access (O-CDMA) systems. Unlike the
conventional scheme, the proposed scheme employs multiple thresholds
providing a shorter mean acquisition time (MAT) performance.
The simulation results show that the MAT of the proposed scheme
is shorter than that of the conventional scheme.