3,083 research outputs found
Soft-decision Viterbi decoding with diversity combining
Diversity combining methods for convolutional coded and soft-decision Viterbi decoded channels in mobile satellite communications systems are evaluated and it is clarified that the pre-Viterbi-decoding maximal ratio combining shows better performance than other methods in Rician fading channels by computer simulation. A novel practical technique for maximal ratio combining is proposed, in which the coefficients for weighting are derived from soft-decision demodulated signals only. The proposed diversity combining method with soft-decision Viterbi decoding requires simple hardware and shows satisfactory performance with slight degradation of 0.3 dB in Rician fading channels compared with an ideal weighting scheme. Furthermore, this diversity method is applied to trellis coded modulation and significant Pe performance improvement is achieved
Secrecy Outage on Transmit Antenna Selection/Maximal Ratio Combining in MIMO Cognitive Radio Networks
This paper investigates the secrecy outage performance
of transmit antenna selection (TAS)/maximal ratio
combining (MRC) in multiple input multiple output (MIMO)
cognitive radio networks (CRNs) over Rayleigh fading channels.
In the considered system, a secondary user (SU-TX) equipped
with NA (NA 1) antennas uses TAS to transmit confidential
messages to another secondary user (SU-RX), which is equipped
with NB (NB 1) antennas and adopts MRC scheme to
process multiple received signals. Meanwhile, an eavesdropper
equipped with NE (NE 1) antennas also adopts MRC scheme
to overhear the transmitted information between SU-TX and
SU-RX. SU-TX adopts the underlay strategy to guarantee the
quality of service of the primary user without spectrum sensing.
In this paper, we derive the exact and asymptotic closed-form
expressions for the secrecy outage probability. Simulations are
conducted to validate the accuracy of the analysis.ARC Discovery Projects Grant DP150103905
The Effect of Macrodiversity on the Performance of Maximal Ratio Combining in Flat Rayleigh Fading
The performance of maximal ratio combining (MRC) in Rayleigh channels with
co-channel interference (CCI) is well-known for receive arrays which are
co-located. Recent work in network MIMO, edge-excited cells and base station
collaboration is increasing interest in macrodiversity systems. Hence, in this
paper we consider the effect of macrodiversity on MRC performance in Rayleigh
fading channels with CCI. We consider the uncoded symbol error rate (SER) as
our performance measure of interest and investigate how different
macrodiversity power profiles affect SER performance. This is the first
analytical work in this area. We derive approximate and exact symbol error rate
results for M-QAM/BPSK modulations and use the analysis to provide a simple
power metric. Numerical results, verified by simulations, are used in
conjunction with the analysis to gain insight into the effects of the link
powers on performance.Comment: 10 pages, 5 figures; IEEE Transaction of Communication, 2012
Corrected typo
On the Sum of Fisher-Snedecor F Variates and its Application to Maximal-Ratio Combining
Capitalizing on the recently proposed Fisher-Snedecor F composite fading
model, in this letter, we investigate the sum of independent but not
identically distributed (i.n.i.d.) Fisher-Snedecor F variates. First, a novel
closed-form expression is derived for the moment generating function of the
instantaneous signal-to-noise ratio. Based on this, the corresponding
probability density function and cumulative distribution function of the sum of
i.n.i.d. Fisher- Snedecor F variates are derived, which are subsequently
employed in the analysis of multiple branch maximal-ratio combining (MRC).
Specifically, we investigate the impact of multipath and shadowed fading on the
outage probability and outage capacity of MRC based receivers. In addition, we
derive exact closed-form expressions for the average bit error rate of coherent
binary modulation schemes followed by an asymptotic analysis which provides
further insights into the effect of the system parameters on the overall
performance. Importantly, it is shown that the effect of multipath fading on
the system performance is more pronounced than that of shadowing.Comment: 5 pages, 3 figure
On the Effects of Estimation Error and Jitter in Ultra-Wideband Communication
The opening of the 3.6 - 10.1 GHz frequency spectrum below the \u27noise-floor\u27 by the FCC in 2002 has made possible the prospect of reusing this frequency spectrum through ultra-wideband (UWB) communication. In this thesis, we compare the performance of several UWB systems in the presence of estimation error and jitter. We then develop two alternative decision schemes to combat the effect of jitter in the UWB system. Numerical results show that one of the schemes provides significantly better performance in the presence of severe jitter than maximal ratio combining and minimal degradation of performance if jitter is not present. A generalized maximal ratio combining decision scheme to combat the presence of estimation error is also proposed. It is shown that the generalized scheme outperforms traditional maximal ratio combining
Cooperative Relaying in Wireless Networks under Spatially and Temporally Correlated Interference
We analyze the performance of an interference-limited, decode-and-forward,
cooperative relaying system that comprises a source, a destination, and
relays, placed arbitrarily on the plane and suffering from interference by a
set of interferers placed according to a spatial Poisson process. In each
transmission attempt, first the transmitter sends a packet; subsequently, a
single one of the relays that received the packet correctly, if such a relay
exists, retransmits it. We consider both selection combining and maximal ratio
combining at the destination, Rayleigh fading, and interferer mobility.
We derive expressions for the probability that a single transmission attempt
is successful, as well as for the distribution of the transmission attempts
until a packet is transmitted successfully. Results provide design guidelines
applicable to a wide range of systems. Overall, the temporal and spatial
characteristics of the interference play a significant role in shaping the
system performance. Maximal ratio combining is only helpful when relays are
close to the destination; in harsh environments, having many relays is
especially helpful, and relay placement is critical; the performance improves
when interferer mobility increases; and a tradeoff exists between energy
efficiency and throughput
Geometry and Wideband Performance of a Maximal Ratio Combining Beam
This paper discusses the geometrical features and wideband performance of the
beam with maximal ratio combining coefficients for a generic multi-antenna
receiver. In particular, in case the channel is a linear combination of plane
waves, we show that such a beam can be decomposed in a linear combination of
beams pointed in the direction of each plane wave, and we compute how many
directions can be effectively utilized. This highlights that such beam is
better exploiting the spatial diversity provided by the channel, and therefore
it is expected to be more robust to disruptions. Moreover, we compute the
achieved Signal-to-Noise-Ratio for a wideband receiver, showing that it is not
significantly worse than for other methods. Finally, we provide some insights
on the robustness of the method by simulating the impact of the blockage of one
multipath components.Comment: 6 pages, 5 figures. Submitted to IEEE WCNC 202
Maximal Ratio combining In N Dual-hop Nakagami-m faded relay branches
Abstract: In recent years relay based communication has gained attention of researchers and the scientific community. In this paper the source-to-destination statistics of a two hop amplify-forward relay branch, with the channel fading statistics of each hop being Nakagami-m distributed has been evaluated. The expression for the statistics of the signal envelope at the output of a maximal ratio combiner in the destination node of a N-path dual-hop relay braches is derived and compared with the simulation results. The statistics are helpful in evaluating the performance of systems using co-operative dual hop relaying and employing maximal ratio combining at the receiver terminal
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