310,580 research outputs found
Random Access Transport Capacity
We develop a new metric for quantifying end-to-end throughput in multihop
wireless networks, which we term random access transport capacity, since the
interference model presumes uncoordinated transmissions. The metric quantifies
the average maximum rate of successful end-to-end transmissions, multiplied by
the communication distance, and normalized by the network area. We show that a
simple upper bound on this quantity is computable in closed-form in terms of
key network parameters when the number of retransmissions is not restricted and
the hops are assumed to be equally spaced on a line between the source and
destination. We also derive the optimum number of hops and optimal per hop
success probability and show that our result follows the well-known square root
scaling law while providing exact expressions for the preconstants as well.
Numerical results demonstrate that the upper bound is accurate for the purpose
of determining the optimal hop count and success (or outage) probability.Comment: Submitted to IEEE Trans. on Wireless Communications, Sept. 200
On the Fundamental Limits of Random Non-orthogonal Multiple Access in Cellular Massive IoT
Machine-to-machine (M2M) constitutes the communication paradigm at the basis
of Internet of Things (IoT) vision. M2M solutions allow billions of multi-role
devices to communicate with each other or with the underlying data transport
infrastructure without, or with minimal, human intervention. Current solutions
for wireless transmissions originally designed for human-based applications
thus require a substantial shift to cope with the capacity issues in managing a
huge amount of M2M devices. In this paper, we consider the multiple access
techniques as promising solutions to support a large number of devices in
cellular systems with limited radio resources. We focus on non-orthogonal
multiple access (NOMA) where, with the aim to increase the channel efficiency,
the devices share the same radio resources for their data transmission. This
has been shown to provide optimal throughput from an information theoretic
point of view.We consider a realistic system model and characterise the system
performance in terms of throughput and energy efficiency in a NOMA scenario
with a random packet arrival model, where we also derive the stability
condition for the system to guarantee the performance.Comment: To appear in IEEE JSAC Special Issue on Non-Orthogonal Multiple
Access for 5G System
Towards a Simple Relationship to Estimate the Capacity of Static and Mobile Wireless Networks
Extensive research has been done on studying the capacity of wireless
multi-hop networks. These efforts have led to many sophisticated and customized
analytical studies on the capacity of particular networks. While most of the
analyses are intellectually challenging, they lack universal properties that
can be extended to study the capacity of a different network. In this paper, we
sift through various capacity-impacting parameters and present a simple
relationship that can be used to estimate the capacity of both static and
mobile networks. Specifically, we show that the network capacity is determined
by the average number of simultaneous transmissions, the link capacity and the
average number of transmissions required to deliver a packet to its
destination. Our result is valid for both finite networks and asymptotically
infinite networks. We then use this result to explain and better understand the
insights of some existing results on the capacity of static networks, mobile
networks and hybrid networks and the multicast capacity. The capacity analysis
using the aforementioned relationship often becomes simpler. The relationship
can be used as a powerful tool to estimate the capacity of different networks.
Our work makes important contributions towards developing a generic methodology
for network capacity analysis that is applicable to a variety of different
scenarios.Comment: accepted to appear in IEEE Transactions on Wireless Communication
Physical Channel Access (PCA): Time and Frequency Access Methods Simulation in NS-2
We present an NS-2 module, Physical Channel Access (PCA), to simulate different access methods on a link shared with Multi-Frequency Time Division Multiple Access (MF-TDMA). This technique is widely used in various network technologies, such as satellite communication. In this context, different access methods at the gateway induce different queuing delays and available capacities, which strongly impact transport layer performance. Depending on QoS requirements, design of new congestion and ow control mechanisms and/or access methods requires evaluation through simulations. PCA module emulates the delays that packets will experience using the shared link, based on descriptive parameters of lower layers characteristics. Though PCA has been developed with DVB-RCS2 considerations in mind (for which we present a use case), other MF-TDMA-based applications can easily be simulated by adapting input parameters. Moreover, the presented implementation details highlight the main methods that might need modifications to implement more specific functionality or emulate other similar access methods (e.g., OFDMA)
Physical Channel Access (PCA): Time and Frequency Access Methods Emulation in NS-2
We present an NS-2 module, Physical Channel Access (PCA), to simulate
different access methods on a link shared with Multi-Frequency Time Division
Multiple Access (MF-TDMA). This tech- nique is widely used in various network
technologies, such as satellite communication. In this context, different
access methods at the gateway induce different queuing delays and available
capacities, which strongly impact transport layer performance. Depending on QoS
requirements, design of new congestion and flow control mechanisms and/or
access methods requires evaluation through simulations.
PCA module emulates the delays that packets will experience using the shared
link, based on descriptive parameters of lower layers characteris- tics. Though
PCA has been developed with DVB-RCS2 considerations in mind (for which we
present a use case), other MF-TDMA-based appli- cations can easily be simulated
by adapting input parameters. Moreover, the presented implementation details
highlight the main methods that might need modifications to implement more
specific functionality or emulate other similar access methods (e.g., OFDMA)
Information-theoretic Capacity of Clustered Random Networks
We analyze the capacity scaling laws of clustered ad hoc networks in which
nodes are distributed according to a doubly stochastic shot-noise Cox process.
We identify five different operational regimes, and for each regime we devise a
communication strategy that allows to achieve a throughput to within a
poly-logarithmic factor (in the number of nodes) of the maximum theoretical
capacity.Comment: 6 pages, in Proceedings of ISIT 201
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