223 research outputs found
Combinatorial Channel Signature Modulation for Wireless ad-hoc Networks
In this paper we introduce a novel modulation and multiplexing method which
facilitates highly efficient and simultaneous communication between multiple
terminals in wireless ad-hoc networks. We term this method Combinatorial
Channel Signature Modulation (CCSM). The CCSM method is particularly efficient
in situations where communicating nodes operate in highly time dispersive
environments. This is all achieved with a minimal MAC layer overhead, since all
users are allowed to transmit and receive at the same time/frequency (full
simultaneous duplex). The CCSM method has its roots in sparse modelling and the
receiver is based on compressive sampling techniques. Towards this end, we
develop a new low complexity algorithm termed Group Subspace Pursuit. Our
analysis suggests that CCSM at least doubles the throughput when compared to
the state-of-the art.Comment: 6 pages, 7 figures, to appear in IEEE International Conference on
Communications ICC 201
The capacity of non-identical adaptive group testing
We consider the group testing problem, in the case where the items are
defective independently but with non-constant probability. We introduce and
analyse an algorithm to solve this problem by grouping items together
appropriately. We give conditions under which the algorithm performs
essentially optimally in the sense of information-theoretic capacity. We use
concentration of measure results to bound the probability that this algorithm
requires many more tests than the expected number. This has applications to the
allocation of spectrum to cognitive radios, in the case where a database gives
prior information that a particular band will be occupied.Comment: To be presented at Allerton 201
Blind Interference Alignment in General Heterogeneous Networks
Heterogeneous networks have a key role in the design of future mobile
communication networks, since the employment of small cells around a macrocell
enhances the network's efficiency and decreases complexity and power demand.
Moreover, research on Blind Interference Alignment (BIA) has shown that optimal
Degrees of Freedom (DoF) can be achieved in certain network architectures, with
no requirement of Channel State Information (CSI) at the transmitters. Our
contribution is a generalised model of BIA in a heterogeneous network with one
macrocell with K users and K femtocells each with one user, by using Kronecker
(Tensor) Product representation. We introduce a solution on how to vary
beamforming vectors under power constraints to maximize the sum rate of the
network and how optimal DoF can be achieved over K+1 time slots.Comment: 5 pages, 7 figures, accepted to IEEE PIMRC'1
Delay-rate tradeoff in ergodic interference alignment
Ergodic interference alignment, as introduced by Nazer et al (NGJV), is a
technique that allows high-rate communication in n-user interference networks
with fast fading. It works by splitting communication across a pair of fading
matrices. However, it comes with the overhead of a long time delay until
matchable matrices occur: the delay is q^n^2 for field size q.
In this paper, we outline two new families of schemes, called JAP and JAP-B,
that reduce the expected delay, sometimes at the cost of a reduction in rate
from the NGJV scheme. In particular, we give examples of good schemes for
networks with few users, and show that in large n-user networks, the delay
scales like q^T, where T is quadratic in n for a constant per-user rate and T
is constant for a constant sum-rate. We also show that half the single-user
rate can be achieved while reducing NGJV's delay from q^n^2 to q^(n-1)(n-2).
This extended version includes complete proofs and more details of good
schemes for small n.Comment: Extended version of a paper presented at the 2012 International
Symposium on Information Theory. 7 pages, 1 figur
Interference Management in Heterogeneous Networks with Blind Transmitters
Future multi-tier communication networks will require enhanced network
capacity and reduced overhead. In the absence of Channel State Information
(CSI) at the transmitters, Blind Interference Alignment (BIA) and Topological
Interference Management (TIM) can achieve optimal Degrees of Freedom (DoF),
minimising network's overhead. In addition, Non-Orthogonal Multiple Access
(NOMA) can increase the sum rate of the network, compared to orthogonal radio
access techniques currently adopted by 4G networks. Our contribution is two
interference management schemes, BIA and a hybrid TIM-NOMA scheme, employed in
heterogeneous networks by applying user-pairing and Kronecker Product
representation. BIA manages inter- and intra-cell interference by antenna
selection and appropriate message scheduling. The hybrid scheme manages
intra-cell interference based on NOMA and inter-cell interference based on TIM.
We show that both schemes achieve at least double the rate of TDMA. The hybrid
scheme always outperforms TDMA and BIA in terms of Degrees of Freedom (DoF).
Comparing the two proposed schemes, BIA achieves more DoF than TDMA under
certain restrictions, and provides better Bit-Error-Rate (BER) and sum rate
performance to macrocell users, whereas the hybrid scheme improves the
performance of femtocell users.Comment: 30 pages, 18 figure
On Intercept Probability Minimization under Sparse Random Linear Network Coding
This paper considers a network where a node wishes to transmit a source
message to a legitimate receiver in the presence of an eavesdropper. The
transmitter secures its transmissions employing a sparse implementation of
Random Linear Network Coding (RLNC). A tight approximation to the probability
of the eavesdropper recovering the source message is provided. The proposed
approximation applies to both the cases where transmissions occur without
feedback or where the reliability of the feedback channel is impaired by an
eavesdropper jamming the feedback channel. An optimization framework for
minimizing the intercept probability by optimizing the sparsity of the RLNC is
also presented. Results validate the proposed approximation and quantify the
gain provided by our optimization over solutions where non-sparse RLNC is used.Comment: To appear on IEEE Transactions on Vehicular Technolog
Approximate Message Passing under Finite Alphabet Constraints
In this paper we consider Basis Pursuit De-Noising (BPDN) problems in which
the sparse original signal is drawn from a finite alphabet. To solve this
problem we propose an iterative message passing algorithm, which capitalises
not only on the sparsity but by means of a prior distribution also on the
discrete nature of the original signal. In our numerical experiments we test
this algorithm in combination with a Rademacher measurement matrix and a
measurement matrix derived from the random demodulator, which enables
compressive sampling of analogue signals. Our results show in both cases
significant performance gains over a linear programming based approach to the
considered BPDN problem. We also compare the proposed algorithm to a similar
message passing based algorithm without prior knowledge and observe an even
larger performance improvement.Comment: 4 pages, 2 figures, to appear in IEEE International Conference on
Acoustics, Speech, and Signal Processing ICASSP 201
Asymptotic Sum-Capacity of Random Gaussian Interference Networks Using Interference Alignment
We consider a dense n-user Gaussian interference network formed by paired
transmitters and receivers placed independently at random in Euclidean space.
Under natural conditions on the node position distributions and signal
attenuation, we prove convergence in probability of the average per-user
capacity C_Sigma/n to 1/2 E log(1 + 2SNR).
The achievability result follows directly from results based on an
interference alignment scheme presented in recent work of Nazer et al. Our main
contribution comes through the converse result, motivated by ideas of
`bottleneck links' developed in recent work of Jafar. An information theoretic
argument gives a capacity bound on such bottleneck links, and probabilistic
counting arguments show there are sufficiently many such links to tightly bound
the sum-capacity of the whole network.Comment: 5 pages; to appear at ISIT 201
Operating ITS-G5 DSRC over Unlicensed Bands: A City-Scale Performance Evaluation
Future Connected and Autonomous Vehicles (CAVs) will be equipped with a large
set of sensors. The large amount of generated sensor data is expected to be
exchanged with other CAVs and the road-side infrastructure. Both in Europe and
the US, Dedicated Short Range Communications (DSRC) systems, based on the IEEE
802.11p Physical Layer, are key enabler for the communication among vehicles.
Given the expected market penetration of connected vehicles, the licensed band
of 75 MHz, dedicated to DSRC communications, is expected to become increasingly
congested. In this paper, we investigate the performance of a vehicular
communication system, operated over the unlicensed bands 2.4 GHz - 2.5 GHz and
5.725 GHz - 5.875 GHz. Our experimental evaluation was carried out in a testing
track in the centre of Bristol, UK and our system is a full-stack ETSI ITS-G5
implementation. Our performance investigation compares key communication
metrics (e.g., packet delivery rate, received signal strength indicator)
measured by operating our system over the licensed DSRC and the considered
unlicensed bands. In particular, when operated over the 2.4 GHz - 2.5 GHz band,
our system achieves comparable performance to the case when the DSRC band is
used. On the other hand, as soon as the system, is operated over the 5.725 GHz
- 5.875 GHz band, the packet delivery rate is 30% smaller compared to the case
when the DSRC band is employed. These findings prove that operating our system
over unlicensed ISM bands is a viable option. During our experimental
evaluation, we recorded all the generated network interactions and the complete
data set has been publicly available.Comment: IEEE PIMRC 2019, to appea
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