356 research outputs found
Stability Analysis of Frame Slotted Aloha Protocol
Frame Slotted Aloha (FSA) protocol has been widely applied in Radio Frequency
Identification (RFID) systems as the de facto standard in tag identification.
However, very limited work has been done on the stability of FSA despite its
fundamental importance both on the theoretical characterisation of FSA
performance and its effective operation in practical systems. In order to
bridge this gap, we devote this paper to investigating the stability properties
of FSA by focusing on two physical layer models of practical importance, the
models with single packet reception and multipacket reception capabilities.
Technically, we model the FSA system backlog as a Markov chain with its states
being backlog size at the beginning of each frame. The objective is to analyze
the ergodicity of the Markov chain and demonstrate its properties in different
regions, particularly the instability region. By employing drift analysis, we
obtain the closed-form conditions for the stability of FSA and show that the
stability region is maximised when the frame length equals the backlog size in
the single packet reception model and when the ratio of the backlog size to
frame length equals in order of magnitude the maximum multipacket reception
capacity in the multipacket reception model. Furthermore, to characterise
system behavior in the instability region, we mathematically demonstrate the
existence of transience of the backlog Markov chain.Comment: 14 pages, submitted to IEEE Transaction on Information Theor
On the Stability of Random Multiple Access with Stochastic Energy Harvesting
In this paper, we consider the random access of nodes having energy
harvesting capability and a battery to store the harvested energy. Each node
attempts to transmit the head-of-line packet in the queue if its battery is
nonempty. The packet and energy arrivals into the queue and the battery are all
modeled as a discrete-time stochastic process. The main contribution of this
paper is the exact characterization of the stability region of the packet
queues given the energy harvesting rates when a pair of nodes are randomly
accessing a common channel having multipacket reception (MPR) capability. The
channel with MPR capability is a generalized form of the wireless channel
modeling which allows probabilistic receptions of the simultaneously
transmitted packets. The results obtained in this paper are fairly general as
the cases with unlimited energy for transmissions both with the collision
channel and the channel with MPR capability can be derived from ours as special
cases. Furthermore, we study the impact of the finiteness of the batteries on
the achievable stability region.Comment: The material in this paper was presented in part at the IEEE
International Symposium on Information Theory, Saint Petersburg, Russia, Aug.
201
On the Stability of Contention Resolution Diversity Slotted ALOHA
In this paper a Time Division Multiple Access (TDMA) based Random Access (RA)
channel with Successive Interference Cancellation (SIC) is considered for a
finite user population and reliable retransmission mechanism on the basis of
Contention Resolution Diversity Slotted ALOHA (CRDSA). A general mathematical
model based on Markov Chains is derived which makes it possible to predict the
stability regions of SIC-RA channels, the expected delays in equilibrium and
the selection of parameters for a stable channel configuration. Furthermore the
model enables the estimation of the average time before reaching instability.
The presented model is verified against simulations and numerical results are
provided for comparison of the stability of CRDSA versus the stability of
traditional Slotted ALOHA (SA). The presented results show that CRDSA has not
only a high gain over SA in terms of throughput but also in its stability.Comment: 10 pages, 12 figures This paper is submitted to the IEEE Transactions
on Communications for possible publication. The IEEE copyright notice applie
Communication Patterns in Mean Field Models for Wireless Sensor Networks
Wireless sensor networks are usually composed of a large number of nodes, and
with the increasing processing power and power consumption efficiency they are
expected to run more complex protocols in the future. These pose problems in
the field of verification and performance evaluation of wireless networks. In
this paper, we tailor the mean-field theory as a modeling technique to analyze
their behavior. We apply this method to the slotted ALOHA protocol, and
establish results on the long term trends of the protocol within a very large
network, specially regarding the stability of ALOHA-type protocols.Comment: 22 pages, in LNCS format, Submitted to QEST'1
Channel-Aware Random Access in the Presence of Channel Estimation Errors
In this work, we consider the random access of nodes adapting their
transmission probability based on the local channel state information (CSI) in
a decentralized manner, which is called CARA. The CSI is not directly available
to each node but estimated with some errors in our scenario. Thus, the impact
of imperfect CSI on the performance of CARA is our main concern. Specifically,
an exact stability analysis is carried out when a pair of bursty sources are
competing for a common receiver and, thereby, have interdependent services. The
analysis also takes into account the compound effects of the multipacket
reception (MPR) capability at the receiver. The contributions in this paper are
twofold: first, we obtain the exact stability region of CARA in the presence of
channel estimation errors; such an assessment is necessary as the errors in
channel estimation are inevitable in the practical situation. Secondly, we
compare the performance of CARA to that achieved by the class of stationary
scheduling policies that make decisions in a centralized manner based on the
CSI feedback. It is shown that the stability region of CARA is not necessarily
a subset of that of centralized schedulers as the MPR capability improves.Comment: The material in this paper was presented in part at the IEEE
International Symposium on Information Theory, Cambridge, MA, USA, July 201
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