1,050 research outputs found
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
MIMO Networks: the Effects of Interference
Multiple-input/multiple-output (MIMO) systems promise enormous capacity
increase and are being considered as one of the key technologies for future
wireless networks. However, the decrease in capacity due to the presence of
interferers in MIMO networks is not well understood. In this paper, we develop
an analytical framework to characterize the capacity of MIMO communication
systems in the presence of multiple MIMO co-channel interferers and noise. We
consider the situation in which transmitters have no information about the
channel and all links undergo Rayleigh fading. We first generalize the known
determinant representation of hypergeometric functions with matrix arguments to
the case when the argument matrices have eigenvalues of arbitrary multiplicity.
This enables the derivation of the distribution of the eigenvalues of Gaussian
quadratic forms and Wishart matrices with arbitrary correlation, with
application to both single user and multiuser MIMO systems. In particular, we
derive the ergodic mutual information for MIMO systems in the presence of
multiple MIMO interferers. Our analysis is valid for any number of interferers,
each with arbitrary number of antennas having possibly unequal power levels.
This framework, therefore, accommodates the study of distributed MIMO systems
and accounts for different positions of the MIMO interferers.Comment: Submitted to IEEE Trans. on Info. Theor
Throughput and Delay Scaling in Supportive Two-Tier Networks
Consider a wireless network that has two tiers with different priorities: a
primary tier vs. a secondary tier, which is an emerging network scenario with
the advancement of cognitive radio technologies. The primary tier consists of
randomly distributed legacy nodes of density , which have an absolute
priority to access the spectrum. The secondary tier consists of randomly
distributed cognitive nodes of density with , which
can only access the spectrum opportunistically to limit the interference to the
primary tier. Based on the assumption that the secondary tier is allowed to
route the packets for the primary tier, we investigate the throughput and delay
scaling laws of the two tiers in the following two scenarios: i) the primary
and secondary nodes are all static; ii) the primary nodes are static while the
secondary nodes are mobile. With the proposed protocols for the two tiers, we
show that the primary tier can achieve a per-node throughput scaling of
in the above two scenarios. In the associated
delay analysis for the first scenario, we show that the primary tier can
achieve a delay scaling of
with . In the second scenario, with two mobility
models considered for the secondary nodes: an i.i.d. mobility model and a
random walk model, we show that the primary tier can achieve delay scaling laws
of and , respectively, where is the random walk
step size. The throughput and delay scaling laws for the secondary tier are
also established, which are the same as those for a stand-alone network.Comment: 13 pages, double-column, 6 figures, accepted for publication in JSAC
201
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