6,135 research outputs found
Open-Loop Spatial Multiplexing and Diversity Communications in Ad Hoc Networks
This paper investigates the performance of open-loop multi-antenna
point-to-point links in ad hoc networks with slotted ALOHA medium access
control (MAC). We consider spatial multiplexing transmission with linear
maximum ratio combining and zero forcing receivers, as well as orthogonal space
time block coded transmission. New closed-form expressions are derived for the
outage probability, throughput and transmission capacity. Our results
demonstrate that both the best performing scheme and the optimum number of
transmit antennas depend on different network parameters, such as the node
intensity and the signal-to-interference-and-noise ratio operating value. We
then compare the performance to a network consisting of single-antenna devices
and an idealized fully centrally coordinated MAC. These results show that
multi-antenna schemes with a simple decentralized slotted ALOHA MAC can
outperform even idealized single-antenna networks in various practical
scenarios.Comment: 51 pages, 19 figures, submitted to IEEE Transactions on Information
Theor
Spectral Efficiency Scaling Laws in Dense Random Wireless Networks with Multiple Receive Antennas
This paper considers large random wireless networks where
transmit-and-receive node pairs communicate within a certain range while
sharing a common spectrum. By modeling the spatial locations of nodes based on
stochastic geometry, analytical expressions for the ergodic spectral efficiency
of a typical node pair are derived as a function of the channel state
information available at a receiver (CSIR) in terms of relevant system
parameters: the density of communication links, the number of receive antennas,
the path loss exponent, and the operating signal-to-noise ratio. One key
finding is that when the receiver only exploits CSIR for the direct link, the
sum of spectral efficiencies linearly improves as the density increases, when
the number of receive antennas increases as a certain super-linear function of
the density. When each receiver exploits CSIR for a set of dominant interfering
links in addition to the direct link, the sum of spectral efficiencies linearly
increases with both the density and the path loss exponent if the number of
antennas is a linear function of the density. This observation demonstrates
that having CSIR for dominant interfering links provides a multiplicative gain
in the scaling law. It is also shown that this linear scaling holds for direct
CSIR when incorporating the effect of the receive antenna correlation, provided
that the rank of the spatial correlation matrix scales super-linearly with the
density. Simulation results back scaling laws derived from stochastic geometry.Comment: Submitte
On Capacity and Delay of Multi-channel Wireless Networks with Infrastructure Support
In this paper, we propose a novel multi-channel network with infrastructure
support, called an MC-IS network, which has not been studied in the literature.
To the best of our knowledge, we are the first to study such an MC-IS network.
Our proposed MC-IS network has a number of advantages over three existing
conventional networks, namely a single-channel wireless ad hoc network (called
an SC-AH network), a multi-channel wireless ad hoc network (called an MC-AH
network) and a single-channel network with infrastructure support (called an
SC-IS network). In particular, the network capacity of our proposed MC-IS
network is times higher than that of an SC-AH network and an
MC-AH network and the same as that of an SC-IS network, where is the number
of nodes in the network. The average delay of our MC-IS network is times lower than that of an SC-AH network and an MC-AH network, and
times lower than the average delay of an SC-IS network, where
and denote the number of channels dedicated for infrastructure
communications and the number of interfaces mounted at each infrastructure
node, respectively. Our analysis on an MC-IS network equipped with
omni-directional antennas only has been extended to an MC-IS network equipped
with directional antennas only, which are named as an MC-IS-DA network. We show
that an MC-IS-DA network has an even lower delay of compared with an SC-IS network and our
MC-IS network. For example, when and , an
MC-IS-DA network can further reduce the delay by 24 times lower that of an
MC-IS network and reduce the delay by 288 times lower than that of an SC-IS
network.Comment: accepted, IEEE Transactions on Vehicular Technology, 201
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