1,856 research outputs found
Energy Detection of Unknown Signals over Cascaded Fading Channels
Energy detection is a favorable mechanism in several applications relating to
the identification of deterministic unknown signals such as in radar systems
and cognitive radio communications. The present work quantifies the detrimental
effects of cascaded multipath fading on energy detection and investigates the
corresponding performance capability. A novel analytic solution is firstly
derived for a generic integral that involves a product of the Meijer
function, the Marcum function and arbitrary power terms. This solution
is subsequently employed in the derivation of an exact closed-form expression
for the average probability of detection of unknown signals over *Rayleigh
channels. The offered results are also extended to the case of square-law
selection, which is a relatively simple and effective diversity method. It is
shown that the detection performance is considerably degraded by the number of
cascaded channels and that these effects can be effectively mitigated by a
non-substantial increase of diversity branches.Comment: 12 page
Analysis of Multipath Mitigation Techniques with Land Mobile Satellite Channel Model
Multipath is undesirable for Global Navigation Satellite System (GNSS) receivers, since the reception of multipath can create a significant distortion to the shape of the correlation function leading to an error in the receivers’ position estimate. Many multipath mitigation techniques exist in the literature to deal with the multipath propagation problem in the context of GNSS. The multipath studies in the literature are often based on optimistic assumptions, for example, assuming a static two-path channel or a fading channel with a Rayleigh or a Nakagami distribution. But, in reality, there are a lot of channel modeling issues, for example, satellite-to-user geometry, variable number of paths, variable path delays and gains, Non Line-Of-Sight (NLOS) path condition, receiver movements, etc. that are kept out of consideration when analyzing the performance of these techniques. Therefore, this is of utmost importance to analyze the performance of different multipath mitigation techniques in some realistic measurement-based channel models, for example, the Land Multipath is undesirable for Global Navigation Satellite System (GNSS) receivers, since the reception of multipath can create a significant distortion to the shape of the correlation function leading to an error in the receivers’ position estimate. Many multipath mitigation techniques exist in the literature to deal with the multipath propagation problem in the context of GNSS. The multipath studies in the literature are often based on optimistic assumptions, for example, assuming a static two-path channel or a fading channel with a Rayleigh or a Nakagami distribution. But, in reality, there are a lot of channel modeling issues, for example, satellite-to-user geometry, variable number of paths, variable path delays and gains, Non Line-Of-Sight (NLOS) path condition, receiver movements, etc. that are kept out of consideration when analyzing the performance of these techniques. Therefore, this is of utmost importance to analyze the performance of different multipath mitigation techniques in some realistic measurement-based channel models, for example, the Land Mobile Satellite (LMS) channel model [1]-[4], developed at the German Aerospace Center (DLR). The DLR LMS channel model is widely used for simulating the positioning accuracy of mobile satellite navigation receivers in urban outdoor scenarios. The main objective of this paper is to present a comprehensive analysis of some of the most promising techniques with the DLR LMS channel model in varying multipath scenarios. Four multipath mitigation techniques are chosen herein for performance comparison, namely, the narrow Early-Minus-Late (nEML), the High Resolution Correlator, the C/N0-based two stage delay tracking technique, and the Reduced Search Space Maximum Likelihood (RSSML) delay estimator. The first two techniques are the most popular and traditional ones used in nowadays GNSS receivers, whereas the later two techniques are comparatively new and are advanced techniques, recently proposed by the authors. In addition, the implementation of the RSSML is optimized here for a narrow-bandwidth receiver configuration in the sense that it now requires a significantly less number of correlators and memory than its original implementation. The simulation results show that the reduced-complexity RSSML achieves the best multipath mitigation performance in moderate-to-good carrier-to-noise density ratio with the DLR LMS channel model in varying multipath scenarios
An Investigation into the Implementation and Performance of Spectrally Shaped Orthogonal Frequency Division Multiplex
Orthogonal Frequency Division Multiplex (OFDM) is a flexible, robust multi-carrier
modulation scheme. The orthogonal spectral shaping and spacing of OFDM sub-carriers
ensure that their spectra can be over-lapped without leading to undesirable inter-carrier
interference. Conventional OFDM systems have non-band limited Sinc(x) shaped subcarrier
spectra. An alternative form of OFDM, referred to hereafter as Spectrally Shaped
OFDM, employs band limited Nyquist shaped sub-carrier spectra. The research described
in this thesis investigates the strengths and weaknesses of Spectrally Shaped OFDM as a
potential modulation scheme for future mobile radio applications.
From this research a novel Digital Signal Processing architecture for modulating and
demodulating Spectrally Shaped OFDM sub-carriers has been derived which exploits the
combination of a complex Discrete Fourier Transform (DFT) and PolyPhase Network
(PPN) filter. This architecture is shown to significantly reduce the minimum number of
computations required per symbol compared to previous designs.
Using a custom coded computer simulation, the effects of varying the key parameters of
the novel architecture's PolyPhase Filter (PPN) filter an the overall system complexity,
spectral performance and system signal-to-distortion have been extensively studied. From
these studies it is shown that compared to similar conventional OFDM systems, Spectrally
Shaped OFDM systems possess superior out-of-band spectral qualities but significantly
worse Peak-to-Average-Power-Ratio (PAPR) envelope performance. lt is also shown that
the absolute value of the end PPN filter coefficients (dependent on the roll-off factor of the
sub-carrier spectral shaping) dictate the system signal-to-distortion ratio when no time-domain
windowing of the PPN filter coefficients is applied. Finally the effects of a both time
and frequency selective fast fading channels on the modulation scheme's uncoded Bit
Error Rate (BER) versus Signal-to-Noise (SNR) performance are simulated. The results
obtained indicate that Spectrally Shaped OFDM is more robust (lower BER) to
frequency-selective fading than time-selective fading
MIMO channel modelling and simulation for cellular and mobile-to-mobile
Recently, mobile-to-mobile (M2M) communications have received much attention due
to several emerging applications, such as wireless mobile ad hoc networks, relay-based
cellular networks, and dedicated short range communications (DSRC) for intelligent
transportation systems (e.g., IEEE 802.11p standard). Different from conventional
fixed-to-mobile (F2M) cellular systems, in M2M systems both the transmitter (Tx)
and receiver (Rx) are in motion and often equipped with low elevation antennas.
Multiple-input-multiple-output (MIMO) technologies, employing multiple antennas
at both the Tx and Rx, have widely been adopted for the third generation (3G) and
beyond-3G (B3G) F2M cellular systems due to their potential benefits of improving
coverage, link reliability, and overall system capacity. More recently, MIMO has been
receiving more and more attention for M2M systems as well.
Reliable knowledge of the propagation channel obtained from channel measurements
and corresponding channel models serve as the enabling foundation for the design
and analysis of MIMO F2M and M2M systems. Furthermore, the development of
accurate MIMO F2M and M2M channel simulation models plays a major role in the
practical simulation and performance evaluation of these systems. These form the
primary motivation behind our research on MIMO channel modelling and simulation
for F2M cellular and M2M communication systems.
In this thesis, we first propose a new wideband theoretical multiple-ring based MIMO
regular-shaped geometry-based stochastic model (RS-GBSM) for non-isotropic scattering
F2M macro-cell scenarios and then derive a generic space-time-frequency (STF)
correlation function (CF). The proposed theoretical reference wideband model can be
reduced to a narrowband one-ring model, a new closed-form STF CF of which is derived
as well. Narrowband and wideband sum-of-sinusoids (SoS) simulation models
are then developed, demonstrating a good agreement with the corresponding reference
models in terms of correlation functions.
Secondly, based on a well-known narrowband two-ring single-input single-output (SISO)
M2M channel reference model, we propose new deterministic and stochastic SoS simulation
models for non-isotropic scattering environments. The proposed deterministic
simulator is the first SISO M2M deterministic simulator with good performance, while
the proposed stochastic simulator outperforms the existing one in terms of fitting the
desired statistical properties of the corresponding reference model.
Thirdly, a new adaptive narrowband MIMO M2M RS-GBSM is proposed for nonisotropic
scattering environments. To the best of our knowledge, the proposed M2M
model is the first RS-GBSM that has the ability to study the impact of the vehicular
traffic density on channel statistics. From the proposed theoretical reference
model, we comprehensively investigate some important M2M channel statistics including
the STF CF, space-Doppler-frequency power spectral density, envelope level
crossing rate, and average fade duration. A close agreement between some channel
statistics obtained from the proposed reference model and measurement data is
observed, confirming the utility of our model.
Finally, we extend the above narrowband model to a new wideband MIMO M2M RSGBSM
with respect to the frequency-selectivity. The proposed wideband reference
model is validated by observing a good match between some statistical properties of
the theoretical model and available measurement data. From the wideband reference
model, we further design new wideband deterministic and stochastic SoS simulation
models. The proposed wideband simulators can be easily reduced to narrowband
ones. The utilities of the newly derived narrowband and wideband simulation models
are validated by comparing their statistical properties with those of the corresponding
reference models.
The proposed channel reference models and simulators are expected to be useful for
the design, testing, and performance evaluation of future MIMO cellular and M2M
communication systems.Scottish Funding Counci
A novel-iterative simulation method for performance analysis of non-coherent FSK/ASK systems over rice/rayleigh channels using the wolfram language
In this paper, a new approach in solving and analysing the performances of the digital telecommunication non-coherent FSK/ASK system in the presence of noise is derived, by using a computer algebra system. So far, most previous solutions cannot be obtained in closed form, which can be a problem for detailed analysis of complex communication systems. In this case, there is no insight into the influence of certain parameters on the performance of the system. The analysis, modelling and design can be time-consuming. One of the main reasons is that these solutions are obtained by utilising traditional numerical tools in the shape of closed-form expressions. Our results were obtained in closed-form solutions. They are resolved by the introduction of an iteration-based simulation method. The Wolfram language is used for describing applied symbolic tools, and Schematic Solver application package has been used for designing. In a new way, the probability density function and the impact of the newly introduced parameter of iteration are performed when errors are calculated. Analyses of the new method are applied to several scenarios: Without fading, in the presence of Rayleigh fading, Rician fading, and in cases when the signals are correlated and uncorrelated
A Survey of Physical Layer Security Techniques for 5G Wireless Networks and Challenges Ahead
Physical layer security which safeguards data confidentiality based on the
information-theoretic approaches has received significant research interest
recently. The key idea behind physical layer security is to utilize the
intrinsic randomness of the transmission channel to guarantee the security in
physical layer. The evolution towards 5G wireless communications poses new
challenges for physical layer security research. This paper provides a latest
survey of the physical layer security research on various promising 5G
technologies, including physical layer security coding, massive multiple-input
multiple-output, millimeter wave communications, heterogeneous networks,
non-orthogonal multiple access, full duplex technology, etc. Technical
challenges which remain unresolved at the time of writing are summarized and
the future trends of physical layer security in 5G and beyond are discussed.Comment: To appear in IEEE Journal on Selected Areas in Communication
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