626 research outputs found
Performance analysis of a fully-connected, full-duplex CDMA ALOHA network with channel sensing and collision detection
In cases where machines having bursty data are equally likely to transmit to one another, code-division multiple-access (CDMA) ALOHA which allows for an individual "virtual channel" for each receiving station may be a better multiple-access protocol than simple ALOHA. With the use of "receiver-based code" multiple-access protocol, it is also possible for a station to listen to the channel of the intended receiver before transmission, and also abort transmission when it detects others transmitting on the same channel. This paper describes a model for a fully-connected, full duplex, and slotted CDMA ALOHA network where channel sensing and collision detection are used. The model is analyzed using a discrete time Markov chain and some numerical results are presented. For a system with a large number of users, where Markov analysis is impractical, equilibrium point analysis is used to predict the stability of the system, and estimate the throughput as well as the delay performance of the system when it is stable. Finally, a comparison is made with a simple channel sense multiple-access with collision detection (CSMA-CD) network, showing that a substantial improvement in the performance is achieved by the proposed network.published_or_final_versio
Wireless Network-Level Partial Relay Cooperation: A Stable Throughput Analysis
In this work, we study the benefit of partial relay cooperation. We consider
a two-node system consisting of one source and one relay node transmitting
information to a common destination. The source and the relay have external
traffic and in addition, the relay is equipped with a flow controller to
regulate the incoming traffic from the source node. The cooperation is
performed at the network level. A collision channel with erasures is
considered. We provide an exact characterization of the stability region of the
system and we also prove that the system with partial cooperation is always
better or at least equal to the system without the flow controller.Comment: Submitted for journal publication. arXiv admin note: text overlap
with arXiv:1502.0113
Relay-assisted Multiple Access with Full-duplex Multi-Packet Reception
The effect of full-duplex cooperative relaying in a random access multiuser
network is investigated here. First, we model the self-interference incurred
due to full-duplex operation, assuming multi-packet reception capabilities for
both the relay and the destination node. Traffic at the source nodes is
considered saturated and the cooperative relay, which does not have packets of
its own, stores a source packet that it receives successfully in its queue when
the transmission to the destination has failed. We obtain analytical
expressions for key performance metrics at the relay, such as arrival and
service rates, stability conditions, and average queue length, as functions of
the transmission probabilities, the self interference coefficient, and the
links' outage probabilities. Furthermore, we study the impact of the relay node
and the self-interference coefficient on the per-user and aggregate throughput,
and the average delay per packet. We show that perfect self-interference
cancelation plays a crucial role when the SINR threshold is small, since it may
result to worse performance in throughput and delay comparing with the
half-duplex case. This is because perfect self-interference cancelation can
cause an unstable queue at the relay under some conditions.Comment: Accepted for publication in the IEEE Transactions on Wireless
Communication
Analysis of Half-Duplex Two-Node Slotted ALOHA Network With Asynchronous Traffic
Despite the long history of research on slotted ALOHA, the exact analysis of
the average delay is still in question as the performance of each node is
coupled with the activity of other nodes. In this paper, we consider a network
comprised of two half-duplex transmitter nodes with asynchronous arrival
traffic that follow the slotted ALOHA protocol. We propose a new queueing
theoretic model based on the state-dependent queues to analyze the network. In
addition, we derive the exact values of delay and stability region for each
node. The numerical results demonstrate the accuracy of our proposed model.Comment: 5 pages, 5 figure
Network-Level Performance Evaluation of a Two-Relay Cooperative Random Access Wireless System
In wireless networks relay nodes can be used to assist the users'
transmissions to reach their destination. Work on relay cooperation, from a
physical layer perspective, has up to now yielded well-known results. This
paper takes a different stance focusing on network-level cooperation. Extending
previous results for a single relay, we investigate here the benefits from the
deployment of a second one. We assume that the two relays do not generate
packets of their own and the system employs random access to the medium; we
further consider slotted time and that the users have saturated queues. We
obtain analytical expressions for the arrival and service rates of the queues
of the two relays and the stability conditions. We investigate a model of the
system, in which the users are divided into clusters, each being served by one
relay, and show its advantages in terms of aggregate and throughput per user.
We quantify the above, analytically for the case of the collision channel and
through simulations for the case of Multi-Packet Reception (MPR), and we
provide insight on when the deployment of a second relay in the system can
yield significant advantages.Comment: Submitted for journal publicatio
A Mobile Satellite Experiment (MSAT-X) network definition
The network architecture development of the Mobile Satellite Experiment (MSAT-X) project for the past few years is described. The results and findings of the network research activities carried out under the MSAT-X project are summarized. A framework is presented upon which the Mobile Satellite Systems (MSSs) operator can design a commercial network. A sample network configuration and its capability are also included under the projected scenario. The Communication Interconnection aspect of the MSAT-X network is discussed. In the MSAT-X network structure two basic protocols are presented: the channel access protocol, and the link connection protocol. The error-control techniques used in the MSAT-X project and the packet structure are also discussed. A description of two testbeds developed for experimentally simulating the channel access protocol and link control protocol, respectively, is presented. A sample network configuration and some future network activities of the MSAT-X project are also presented
Stable Throughput and Delay Analysis of a Random Access Network With Queue-Aware Transmission
In this work we consider a two-user and a three-user slotted ALOHA network
with multi-packet reception (MPR) capabilities. The nodes can adapt their
transmission probabilities and their transmission parameters based on the
status of the other nodes. Each user has external bursty arrivals that are
stored in their infinite capacity queues. For the two- and the three-user cases
we obtain the stability region of the system. For the two-user case we provide
the conditions where the stability region is a convex set. We perform a
detailed mathematical analysis in order to study the queueing delay by
formulating two boundary value problems (a Dirichlet and a Riemann-Hilbert
boundary value problem), the solution of which provides the generating function
of the joint stationary probability distribution of the queue size at user
nodes. Furthermore, for the two-user symmetric case with MPR we obtain a lower
and an upper bound for the average delay without explicitly computing the
generating function for the stationary joint queue length distribution. The
bounds as it is seen in the numerical results appear to be tight. Explicit
expressions for the average delay are obtained for the symmetrical model with
capture effect which is a subclass of MPR models. We also provide the optimal
transmission probability in closed form expression that minimizes the average
delay in the symmetric capture case. Finally, we evaluate numerically the
presented theoretical results.Comment: Submitted for journal publicatio
Secure Communications for the Two-user Broadcast Channel with Random Traffic
In this work, we study the stability region of the two-user broadcast channel
(BC) with bursty data arrivals and security constraints. We consider the
scenario, where one of the receivers has a secrecy constraint and its packets
need to be kept secret from the other receiver. This is achieved by employing
full-duplexing at the receiver with the secrecy constraint, so that it
transmits a jamming signal to impede the reception of the other receiver. In
this context, the stability region of the two-user BC is characterized for the
general decoding case. Then, assuming two different decoding schemes the
respective stability regions are derived. The effect of self-interference due
to the full-duplex operation on the stability region is also investigated. The
stability region of the BC with a secrecy constraint, where the receivers do
not have full duplex capability can be obtained as a special case of the
results derived in this paper. In addition, the paper considers the problem of
maximizing the saturated throughput of the queue, whose packets does not
require to be kept secret under minimum service guarantees for the other queue.
The results provide new insights on the effect of the secrecy constraint on the
stability region of the BC. In particular, it is shown that the stability
region with secrecy constraint is sensitive to the coefficient of
self-interference cancelation under certain cases.Comment: Submitted for journal publicatio
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