12 research outputs found
Multi-user Communication in Difficult Interference
The co-channel interference (CCI) is one of the major impairments in wireless
communication. CCI typically reduces the reliability of wireless communication
links, but the difficult CCI which is no more or less strong to the desired
signals destroys wireless links despite having myriad of CCI mitigation
methods. It is shown in this paper that M-QAM (Quadrature Amplitude Modulation)
or similar modulation schemes which modulate information both in in-phase and
quadrature-phase are particularly vulnerable to difficult CCI. Despite
well-known shortcomings, it is shown in this paper that M-PAM or similar
schemes that use a single dimension for modulation provides an important mean
for difficult CCI mitigation.Comment: 4 pages, 2 figs and accepted in IEEE ICASSP 2019, Brighton, U
Mediumband Wireless Communication
The fundamental phenomenon widely known as multipath is unavoidable in
wireless communication, and affects almost every element of modern wireless
communication systems. The impact of multipath on the received signal depends
on whether the delay spread (i.e., spread of time delays associated with
different multipath components) is large or small relative to the signalling
period of the wireless communication system. In narrowband systems, the delay
spread is about one tenth (or less) of the signalling period. The delay spread
and the signalling period of broadband systems are in the same order of
magnitude. In between these two extremes, there appears to exist an important,
yet overlooked, class of systems whose delay spread is neither small nor large
enough for them to fall into these two basic classes. In this paper, the effect
of multipath on this class of systems denoted henceforth as mediumband is
studied, and its channel is characterized in compact form in order to enable
future research into this class of wireless communication systems.Comment: 5 pages, 3 figures, Proceedings of IEEE Vehicular Technology
conference (VTC-Fall) 2022, London-Beijin
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
Performance Analysis of Dual-User Macrodiversity MIMO Systems with Linear Receivers in Flat Rayleigh Fading
The performance of linear receivers in the presence of co-channel
interference in Rayleigh channels is a fundamental problem in wireless
communications. Performance evaluation for these systems is well-known for
receive arrays where the antennas are close enough to experience equal average
SNRs from a source. In contrast, almost no analytical results are available for
macrodiversity systems where both the sources and receive antennas are widely
separated. Here, receive antennas experience unequal average SNRs from a source
and a single receive antenna receives a different average SNR from each source.
Although this is an extremely difficult problem, progress is possible for the
two-user scenario. In this paper, we derive closed form results for the
probability density function (pdf) and cumulative distribution function (cdf)
of the output signal to interference plus noise ratio (SINR) and signal to
noise ratio (SNR) of minimum mean squared error (MMSE) and zero forcing (ZF)
receivers in independent Rayleigh channels with arbitrary numbers of receive
antennas. The results are verified by Monte Carlo simulations and high SNR
approximations are also derived. The results enable further system analysis
such as the evaluation of outage probability, bit error rate (BER) and
capacity.Comment: 24 pages, 7 figures; IEEE Transaction of Wireless Communication 2012
Corrected typo
Bit Error Rate Performance and Diversity Analysis for Mediumband Wireless Communication
Mediumband wireless communication refers to wireless communication through a
class of channels known as mediumband that exists on the TmTs-plane. This
paper, through statistical analysis and computer simulations, studies the
performance limits of this class of channels in terms of uncoded bit error rate
(BER) and diversity order. We show that, owing mainly to the effect of the deep
fading avoidance, which is unique to the channels in the mediumband region,
mediumband wireless systems, if designed judiciously, have the potential to
achieve significantly superior error rate and higher order diversity even in
non-line-of-sight (NLoS) propagation environments where the achievable
diversity order is otherwise low.Comment: 6 pages, 5 figures, Accepted for Publication in the Proceedings of
IEEE VCC 2023, 28-30 Nov. 202
Wireless infrared-based LiFi uplink transmission with link blockage and random device orientation
Light-fidelity (LiFi) is recognised as a promising technology for next generation wireless access networks. However, limited research efforts have been spent on the uplink (UL) transmission system in LiFi networks. In this article, a wireless infrared (IR)-based LiFi UL system is investigated. In particular, we focus on the performance of a single static user under the influence of random device orientation and link blockage. Simulations and mathematical analysis have been used to evaluate the UL system performance. The analytical expressions for the UL optical wireless channel and signal-to-noise ratio (SNR) statistics under the effects of random device orientation and link blockage are derived. The results show that the effects of random orientation and link blockage may lead to a decrease in coverage probability by 10% - 40% with various SNR thresholds
Massive But Few Active MIMO
International audienceIn this paper, an emerging wireless communication concept, which is termed as spatial modulation (SM) for large-scale multiple-input-multiple-output (MIMO), is considered. The results show that from the information-theoretic perspective, SM achieves capacity comparable to the open-loop MIMO capacity, although a subset of transmit antennas is activated in every channel use because both the channel coefficients and the input symbols carry information in SM. As a result, SM compensates the loss of information capacity due to a subset of antennas being activated by modulating information in the antenna index; therefore, the total information rate remains high. In particular, an upper bound for the capacity of SM is derived in closed form, and it is shown analytically that this upper bound is almost certainly achievable in the massive MIMO regime. Moreover, it is shown that the upper bound is achievable with no channel state information at the transmitter (CSIT) but with channel distribution information (CDI) at the transmitter (CDIT). The optimum transmission strategy should adapt the channel input distribution to fading using CDI such as the K factor in Rician fading or the shape parameter m in Nakagami-m fading