61 research outputs found
MAC Centered Cooperation - Synergistic Design of Network Coding, Multi-Packet Reception, and Improved Fairness to Increase Network Throughput
We design a cross-layer approach to aid in develop- ing a cooperative
solution using multi-packet reception (MPR), network coding (NC), and medium
access (MAC). We construct a model for the behavior of the IEEE 802.11 MAC
protocol and apply it to key small canonical topology components and their
larger counterparts. The results obtained from this model match the available
experimental results with fidelity. Using this model, we show that fairness
allocation by the IEEE 802.11 MAC can significantly impede performance; hence,
we devise a new MAC that not only substantially improves throughput, but
provides fairness to flows of information rather than to nodes. We show that
cooperation between NC, MPR, and our new MAC achieves super-additive gains of
up to 6.3 times that of routing with the standard IEEE 802.11 MAC. Furthermore,
we extend the model to analyze our MAC's asymptotic and throughput behaviors as
the number of nodes increases or the MPR capability is limited to only a single
node. Finally, we show that although network performance is reduced under
substantial asymmetry or limited implementation of MPR to a central node, there
are some important practical cases, even under these conditions, where MPR, NC,
and their combination provide significant gains
Random Access Game in Fading Channels with Capture: Equilibria and Braess-like Paradoxes
The Nash equilibrium point of the transmission probabilities in a slotted
ALOHA system with selfish nodes is analyzed. The system consists of a finite
number of heterogeneous nodes, each trying to minimize its average transmission
probability (or power investment) selfishly while meeting its average
throughput demand over the shared wireless channel to a common base station
(BS). We use a game-theoretic approach to analyze the network under two
reception models: one is called power capture, the other is called signal to
interference plus noise ratio (SINR) capture. It is shown that, in some
situations, Braess-like paradoxes may occur. That is, the performance of the
system may become worse instead of better when channel state information (CSI)
is available at the selfish nodes. In particular, for homogeneous nodes, we
analytically present that Braess-like paradoxes occur in the power capture
model, and in the SINR capture model with the capture ratio larger than one and
the noise to signal ratio sufficiently small.Comment: 30 pages, 5 figure
Effects of MAC Approaches on Non-Monotonic Saturation with COPE - A Simple Case Study
We construct a simple network model to provide insight into network design strategies. We show that the model can be used to address various approaches to network coding, MAC, and multi-packet reception so that their effects on network throughput can be evaluated. We consider several topology components which exhibit the same non-monotonic saturation behavior found within the Katti et. al. COPE experiments. We further show that fairness allocation by the MAC can seriously impact performance and cause this non-monotonic saturation. Using our model, we develop a MAC that provides monotonic saturation, higher saturation throughput gains and fairness among flows rather than nodes. The proposed model provides an estimate of the achievable gains for the cross-layer design of network coding, multi-packet reception, and MAC showing that super-additive throughput gains on the order of six times that of routing are possible.United States. Dept. of Defense (Air Force Contract FA8721-05-C-0002)Irwin Mark Jacobs and Joan Klein Jacobs Presidential FellowshipInformation Systems of ASD(R&E
QoS in LEO satellite networks with multipacket reception
Dissertação apresentada para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores, pela Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaLow Earth Orbit (LEO) satellite networks can improve terrestrial wireless networks to
allow global broadband services for Mobile Terminals (MT), regardless of the users' location.
In this context, hybrid telecommunication systems combining satellites with Long
Term Evolution (LTE) networks, like the LightSquared technology, are intended to provide
ubiquitous high-speed services.
This dissertation analyses the performance of a random access protocol that uses Hybrid
Network-assisted Diversity Multiple Access (H-NDMA), for a LEO satellite system
network, named by Satellite Random NDMA (SR-NDMA). The protocol also considers
a Single Carrier-Frequency Domain Equalization (SC-FDE) scheme for the uplink transmission
and a Multipacket Reception (MPR) receiver. In this scenario, the transmission
of data packets between MTs and the Base Station (BS) is made through random access
and schedule access slots, organized into super-frames with the duration of a Round Trip
Time (RTT).
A SR-NDMA simulator is implemented to measure the system performance in matters
of throughput, energy consumption, system delay and also the protocol capacity to
meet Quality of Service (QoS) requirements. A set of simulations tests were made with a
random Poisson process tra c generation to validate the analytical model. The capacity
to ful l the QoS requirements of a real-time tra c class was also tested.FCT/MEC: MPSat - PTDC/EEA-TEL/099074/2008,
OPPORTUNISTIC CR - PTDC/EEA-TEL/115981/2009, Femtocells - PTDC/EEA-TEL/120666/2010
e ADIN - PTDC/EEI-TEL/2990/201
Lightly synchronized Multipacket Reception in Machine-Type Communications Networks
Machine Type Communication (MTC) applications were designed to monitor and control
elements of our surroundings and environment. MTC applications have a different
set of requirements compared to the traditional communication devices, with Machine to
Machine (M2M) data being mostly short, asynchronous, bursty and sometimes requiring end-to-end delays below 1ms. With the growth of MTC, the new generation of mobile communications has to be able to present different types of services with very different requirements, i.e. the same network has to be capable of "supplying" connection to the user that just wants to download a video or use social media, allowing at the same time MTC that has completely different requirements, without deteriorating both experiences.
The challenges associated to the implementation of MTC require disruptive changes at
the Physical (PHY) and Medium Access Control (MAC) layers, that lead to a better use of the spectrum available. The orthogonality and synchronization requirements of the PHY layer of current Long Term Evolution Advanced (LTE-A) radio access network (based on glsofdm and Single Carrier Frequency Domain Equalization (SC-FDE)) are obstacles for this new 5th Generation (5G) architecture. Generalized Frequency Division Multiplexing (GFDM) and other modulation techniques were proposed as candidates for the 5G PHY layer, however they also suffer from visible degradation when the transmitter and receiver are not synchronized, leading to a poor performance when collisions occur in an asynchronous MAC layer. This dissertation addresses the requirements of M2M traffic at the MAC layer applying multipacket reception (MPR) techniques to handle the bursty nature of the traffic and synchronization tones and optimized back-off approaches to reduce the delay. It proposes a new MAC protocol and analyses its performance analytically considering an SC-FDE modulation. The models are validated using a system level cross-layer simulator developed in MATLAB, which implements the MAC protocol and applies PHY layer performance models. The results show that the MAC’s latency depends mainly on the number of users and the load of each user, and can be controlled using these two parameters
On Coding for Reliable Communication over Packet Networks
We present a capacity-achieving coding scheme for unicast or multicast over
lossy packet networks. In the scheme, intermediate nodes perform additional
coding yet do not decode nor even wait for a block of packets before sending
out coded packets. Rather, whenever they have a transmission opportunity, they
send out coded packets formed from random linear combinations of previously
received packets. All coding and decoding operations have polynomial
complexity.
We show that the scheme is capacity-achieving as long as packets received on
a link arrive according to a process that has an average rate. Thus, packet
losses on a link may exhibit correlation in time or with losses on other links.
In the special case of Poisson traffic with i.i.d. losses, we give error
exponents that quantify the rate of decay of the probability of error with
coding delay. Our analysis of the scheme shows that it is not only
capacity-achieving, but that the propagation of packets carrying "innovative"
information follows the propagation of jobs through a queueing network, and
therefore fluid flow models yield good approximations. We consider networks
with both lossy point-to-point and broadcast links, allowing us to model both
wireline and wireless packet networks.Comment: 33 pages, 6 figures; revised appendi
Networked Control Systems: The Communication Basics and Control Methodologies
As an emerging research field, networked control systems have shown the increasing importance and attracted more and more attention in the recent years. The integration of control and communication in networked control systems has made the design and analysis of such systems a great theoretical challenge for conventional control theory. Such an integration also makes the implementation of networked control systems a necessary intermediate step towards the final convergence of control, communication, and computation. We here introduce the basics of networked control systems and then describe the state-of-the-art research in this field. We hope such a brief tutorial can be useful to inspire further development of networked control systems in both theory and potential applications
- …