675 research outputs found
Simulation Analysis of Medium Access Techniques
This paper presents comparison of Access Techniques used in Medium Access
Control (MAC) protocol for Wireless Body Area Networks (WBANs). Comparison is
performed between Time Division Multiple Access (TDMA), Frequency Division
Multiple Access (FDMA), Carrier Sense Multiple Access with Collision Avoidance
(CSMA/CA), Pure ALOHA and Slotted ALOHA (S-ALOHA). Performance metrics used for
comparison are throughput (T), delay (D) and offered load (G). The main goal
for comparison is to show which technique gives highest Throughput and lowest
Delay with increase in Load. Energy efficiency is major issue in WBAN that is
why there is need to know which technique performs best for energy conservation
and also gives minimum delay.Comment: NGWMN with 7th IEEE International Conference on Broadband and
Wireless Computing, Com- munication and Applications (BWCCA 2012), Victoria,
Canada, 201
A Unifying Framework for Local Throughput in Wireless Networks
With the increased competition for the electromagnetic spectrum, it is
important to characterize the impact of interference in the performance of a
wireless network, which is traditionally measured by its throughput. This paper
presents a unifying framework for characterizing the local throughput in
wireless networks. We first analyze the throughput of a probe link from a
connectivity perspective, in which a packet is successfully received if it does
not collide with other packets from nodes within its reach (called the audible
interferers). We then characterize the throughput from a
signal-to-interference-plus-noise ratio (SINR) perspective, in which a packet
is successfully received if the SINR exceeds some threshold, considering the
interference from all emitting nodes in the network. Our main contribution is
to generalize and unify various results scattered throughout the literature. In
particular, the proposed framework encompasses arbitrary wireless propagation
effects (e.g, Nakagami-m fading, Rician fading, or log-normal shadowing), as
well as arbitrary traffic patterns (e.g., slotted-synchronous,
slotted-asynchronous, or exponential-interarrivals traffic), allowing us to
draw more general conclusions about network performance than previously
available in the literature.Comment: Submitted for journal publicatio
Stochastic Analysis of Non-slotted Aloha in Wireless Ad-Hoc Networks
In this paper we propose two analytically tractable stochastic models of
non-slotted Aloha for Mobile Ad-hoc NETworks (MANETs): one model assumes a
static pattern of nodes while the other assumes that the pattern of nodes
varies over time. Both models feature transmitters randomly located in the
Euclidean plane, according to a Poisson point process with the receivers
randomly located at a fixed distance from the emitters. We concentrate on the
so-called outage scenario, where a successful transmission requires a
Signal-to-Interference-and-Noise Ratio (SINR) larger than a given threshold.
With Rayleigh fading and the SINR averaged over the duration of the packet
transmission, both models lead to closed form expressions for the probability
of successful transmission. We show an excellent matching of these results with
simulations. Using our models we compare the performances of non-slotted Aloha
to previously studied slotted Aloha. We observe that when the path loss is not
very strong both models, when appropriately optimized, exhibit similar
performance. For stronger path loss non-slotted Aloha performs worse than
slotted Aloha, however when the path loss exponent is equal to 4 its density of
successfully received packets is still 75% of that in the slotted scheme. This
is still much more than the 50% predicted by the well-known analysis where
simultaneous transmissions are never successful. Moreover, in any path loss
scenario, both schemes exhibit the same energy efficiency.Comment: accepted for IEEE Infocom 201
ALOHA With Collision Resolution(ALOHA-CR): Theory and Software Defined Radio Implementation
A cross-layer scheme, namely ALOHA With Collision Resolution (ALOHA-CR), is
proposed for high throughput wireless communications in a cellular scenario.
Transmissions occur in a time-slotted ALOHA-type fashion but with an important
difference: simultaneous transmissions of two users can be successful. If more
than two users transmit in the same slot the collision cannot be resolved and
retransmission is required. If only one user transmits, the transmitted packet
is recovered with some probability, depending on the state of the channel. If
two users transmit the collision is resolved and the packets are recovered by
first over-sampling the collision signal and then exploiting independent
information about the two users that is contained in the signal polyphase
components. The ALOHA-CR throughput is derived under the infinite backlog
assumption and also under the assumption of finite backlog. The contention
probability is determined under these two assumptions in order to maximize the
network throughput and maintain stability. Queuing delay analysis for network
users is also conducted. The performance of ALOHA-CR is demonstrated on the
Wireless Open Access Research Platform (WARP) test-bed containing five software
defined radio nodes. Analysis and test-bed results indicate that ALOHA-CR leads
to significant increase in throughput and reduction of service delays
Energy-efficient wireless communication
In this chapter we present an energy-efficient highly adaptive network interface architecture and a novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations in bandwidth scheduling and error control are necessary to achieve energy efficiency and an acceptable quality of service. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters
On multiple access random medium access control
In this paper, we develop a new class of medium access control protocol, which allows each user to transmit at different data rates chosen randomly from an appropriately determined set of rates. By using successive interference cancellation, multiple packets can be received simultaneously. In slotted Aloha type Gaussian networks, we show that the achievable total throughput of the proposed protocol is at least a constant fraction of the mac sum rate when the number of transmission rates at each node is equal to the number of users in the network. We also study the case when only a limited number of transmission rates is available at each node. Extension to rate splitting is discussed. Simulation results show that the proposed protocol can achieve a significant throughput gain over the conventional Aloha
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