26 research outputs found
Erasure Insertion in RS-Coded SFH MFSK Subjected to Tone Jamming and Rayleigh Fading
The achievable performance of Reed Solomon (RS) coded slow frequency hopping (SFH) assisted M-ary frequency shift keying (MFSK) using various erasure insertion (EI) schemes is investigated, when communicating over uncorrelated Rayleigh fading channels in the presence of multitone jamming. Three different EI schemes are considered, which are based on the output threshold test (OTT), on the ratio threshold test (RTT) and on the joint maximum output-ratio threshold test (MORTT). The relevant statistics of these EI schemes are investigated mathematically and based on these statistics, their performance is evaluated in the context of error-and-erasure RS decoding. It is demonstrated that the system performance can be significantly improved by using error-and-erasure decoding invoking the EI schemes considered. Index TermsâTone jamming, OTT, RTT, MO-RTT, SFH, error-and-erasure decoding (EED)
Theoretical contributions for generalized scenarios of wireless channels
Orientador: Michel Daoud YacoubTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de ComputaçãoResumo: Recentemente, trĂȘs novos modelos probabilĂsticos de canal, modelos a-u, ?-u e ?-u, foram propostos com o intuito de prover uma anĂĄlise mais realĂstica do sinal propagante. Por apresentarem um grau de liberdade a mais que os demais jĂĄ existentes na literatura, um melhor ajuste a medidas de campo verificou-se com a utilização dos mesmos. Esta tese provĂȘ uma caracterização estatĂstica para estes modelos de desvanecimento generalizados. Tal caracterização engloba tanto estatĂsticas de primeira como de segunda ordem. AproximaçÔes simples e precisas para a soma de variĂĄveis e processos aleatĂłrios sĂŁo propostas. InĂșmeras mĂ©tricas de desempenho em ambientes com e sem diversidade na recepção sĂŁo investigadas de forma exata e aproximada. Dentre estas, podemos citar: probabilidade de outage, taxa de erro de bit, capacidade de canal, taxa de cruzamento de nĂvel, duração mĂ©dia de desvanecimento, dentre outras. AlĂ©m disso, mostra-se tambĂ©m qual das distribuiçÔes generalizadas melhor aproxima a soma de variĂĄveis e processos Nakagami-m, uma vez que todas incluem Nakagami-m como caso especial. Finalmente, expressĂ”es exatas e aproximadas para a taxa de cruzamento de nĂvel de canaisWeibull correlacionados e nĂŁo idĂȘnticos em receptores multirramos sĂŁo apresentadasAbstract: Recently, three new channel models, a-u, ?-u and ?-u, were proposed with the aim to provide a more realistic analysis of the propagate signal. Due to they have one degree of freedom more than those already existing in the literature, a better adjust to field measurement data was attested with their use. This thesis deals with the statistical characterization of these generalized fading models. Such a characterization includes both first and second order statistics. Simple and precise approximations to the sum of random variables and processes are proposed. Several performance metrics in scenarios with and without diversity are investigated in an exact and approximate manner. Among them, we may cite: outage probability, bit error probability, channel capacity, level crossing rate, average fade duration, such others. Furthermore, it is shown what is the generalized distribution that better approximate the sum of Nakagami-m variates and processes, once that all of them include Nakagami-m as special case. Finally, exact and approximate expressions for the crossing rates of non-identical correlated Weibull channels in multibranch receivers are presented.DoutoradoTelecomunicaçÔes e TelemĂĄticaDoutor em Engenharia ElĂ©tric
Level Crossing Rates of Interference in Cognitive Radio Networks
The future deployment of cognitive radios is critically dependent on the fact
that the incumbent primary user system must remain as oblivious as possible to
their presence. This in turn heavily relies on the fluctuations of the
interfering cognitive radio signals. In this letter we compute the level
crossing rates of the cumulative interference created by the cognitive radios.
We derive analytical formulae for the level crossing rates in Rayleigh and
Rician fast fading conditions. We approximate Rayleigh and Rician level
crossing rates using fluctuation rates of gamma and scaled noncentral
processes respectively. The analytical results and the approximations used in
their derivations are verified by Monte Carlo simulations and the analysis is
applied to a particular CR allocation strategy.Comment: submitted to the IEEE Transactions on Wireless Communication
Statistical analysis of the capacity of mobile radio channels
Doktorgradsavhandling i informasjons- og kommunikasjonsteknologi, Universitetet i Agder, Grimstad, 201
Extreme Level Crossing Rate: A New Performance Indicator for URLLC Systems
Level crossing rate (LCR) is a well-known statistical tool that is related to
the duration of a random stationary fading process \emph{on average}. In doing
so, LCR cannot capture the behavior of \emph{extremely rare} random events.
Nonetheless, the latter events play a key role in the performance of
ultra-reliable and low-latency communication systems rather than their average
(expectation) counterparts. In this paper, for the first time, we extend the
notion of LCR to address this issue and sufficiently characterize the
statistical behavior of extreme maxima or minima. This new indicator, entitled
as extreme LCR (ELCR), is analytically introduced and evaluated by resorting to
the extreme value theory and risk assessment. Capitalizing on ELCR, some key
performance metrics emerge, i.e., the maximum outage duration, minimum
effective duration, maximum packet error rate, and maximum transmission delay.
They are all derived in simple closed-form expressions. The theoretical results
are cross-compared and verified via extensive simulations whereas some useful
engineering insights are manifested.Comment: Accepted for publication in IEEE TV
Performance Analysis of M-Ary PSK Modulation Schemes over Multiple Double Rayleigh Fading Channels with EGC in Cooperative Networks
paper presented at the 2010 IEEE International Conference on Communications Workshops, Cape Town.(c) 2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. Paper also available from the publisher: http://dx.doi.org/10.1109/ICCW.2010.5503940This article studies the performance of M-ary phase shift keying (PSK) modulation schemes over mobile-to-mobile (M2M) fading channels with equal gain combining (EGC) in cooperative networks. The frequency-nonselective M2M fading channels are modeled assuming non-line-of-sight (NLOS) propagation conditions. Furthermore, a dual-hop amplify-and-forward relay type cooperative network is taken into consideration here. It is assumed that K diversity branches are present between the source mobile station and the destination mobile station via K mobile relays. The performance of M-ary PSK modulation schemes is analyzed by evaluating the average bit error probability (BEP). We have derived a simple analytical approximation for the average BEP of M-ary PSK modulation schemes over relay-based M2M fading channels with EGC. The validity and accuracy of the analytical approximation is confirmed by simulations. The presented results show that in a dual-hop relay system with EGC, there is a remarkable improvement in the diversity gain as the number of diversity branches K increases
Multi-carrier CDMA using convolutional coding and interference cancellation
SIGLEAvailable from British Library Document Supply Centre-DSC:DXN016251 / BLDSC - British Library Document Supply CentreGBUnited Kingdo