77 research outputs found
Large-System Analysis of Correlated MIMO Multiple Access Channels with Arbitrary Signaling in the Presence of Interference
Presence of multiple antennas on both sides of
a communication channel promises significant improvements in
system throughput and power efficiency. In effect, a new clas
s
of large multiple-input multiple-output (MIMO) communication
systems has recently emerged and attracted both scientific and
industrial attention. To analyze these systems in realistic scenarios,
one has to include such aspects as co-channel interference,
multiple access and spatial correlation. In this paper, we study
the properties of correlated MIMO multiple-access channels in
the presence of external interference. Using the replica method
from statistical physics, we derive the ergodic sum-rate of the
communication for arbitrary signal constellations when the numbers
of antennas at both ends of the channel grow large. Based
on these asymptotic expressions, we also address the problem of
sum-rate maximization using statistical channel information and
linear precoding. The numerical results demonstrate that when
the interfering terminals use discrete constellations, the resulting
interference becomes easier to handle compared to Gaussian
signals. Thus, it may be possible to accommodate more interfering
transmitter-receiver pairs within the same area as compare
d
to the case of Gaussian signals. In addition, we demonstrate
numerically for the Gaussian and QPSK signaling schemes that it
is possible to design precoder matrices that significantly improve
the achievable rates at low-to-mid range of signal-to-noise ratios
when compared to isotropic precoding
Asymptotic Performance Analysis of a K-Hop Amplify-and-Forward Relay MIMO Channel
The present paper studies the asymptotic performance of multi-hop amplify-and-forward relay multiple-antenna communication channels. Each multi-antenna terminal in the network amplifies the received signal, sent by a source, and retransmits it upstream towards a destination. Achievable ergodic rates under both jointly optimal detection and decoding and practical separate decoding schemes for arbitrary signaling schemes, along with the average bit error rate for various receiver structures are derived in the regime where the number of antennas at each terminal grows large without a bound. To overcome the difficulty of averaging over channel realizations we apply large-system analysis based on the replica method from statistical physics. The validity of the large-system analysis is further verified through Monte Carlo simulations of realistic finite-sized systems
On the Asymptotic Sum Rate of Downlink Cellular Systems With Random User Locations.
We consider a downlink cellular communication system with a multi-antenna base station (BS). A regularized zero forcing precoder is employed at the BS to manage the inter-user interference within the cell. Using methods from random matrix theory, we derive a deterministic approximation for the achievable ergodic sum rate, taking into account the randomness from both fading and random user locations. The obtained approximation describes well the behavior of finite-sized systems and enables efficient optimization of the precoder matrix
A century of trends in adult human height
Being taller is associated with enhanced longevity, and higher education and earnings. We reanalysed 1472 population-based studies, with measurement of height on more than 18.6 million participants to estimate mean height for people born between 1896 and 1996 in 200 countries. The largest gain in adult height over the past century has occurred in South Korean women and Iranian men, who became 20.2 cm (95% credible interval 17.5-22.7) and 16.5 cm (13.3-19.7) taller, respectively. In contrast, there was little change in adult height in some sub-Saharan African countries and in South Asia over the century of analysis. The tallest people over these 100 years are men born in the Netherlands in the last quarter of 20th century, whose average heights surpassed 182.5 cm, and the shortest were women born in Guatemala in 1896 (140.3 cm; 135.8-144.8). The height differential between the tallest and shortest populations was 19-20 cm a century ago, and has remained the same for women and increased for men a century later despite substantial changes in the ranking of countries
A near ideal noise whitening filter for an asynchronous time-varying CDMA system
IEEE Transactions on Communications4491355-1361IECM
Adaptive symbol and parameter estimation in asynchronous multiuser CDMA detectors
10.1109/26.554369IEEE Transactions on Communications452213-220IECM
Breadth-first maximum likelihood detection in multiuser CDMA
10.1109/26.634679IEEE Transactions on Communications45101176-1178IECM
A linear receiver for coded multiuser CDMA
10.1109/26.592562IEEE Transactions on Communications455605-610IECM
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