دانلود مقاله Datalink Streaming in Wireless Sensor Networks

اختصاصی از اس فایل دانلود مقاله Datalink Streaming in Wireless Sensor Networks دانلود با لینک مستقیم و پر سرعت .

Raghu K. Ganti, Praveen Jayachandran ∗,
Haiyun Luo, and Tarek F. Abdelzaher

Abstract
Datalink layer framing in wireless sensor networks usually
faces a trade-off between large frame sizes for high
channel bandwidth utilization and small frame sizes for effective
error recovery. Given the high error rates of intermote
communications, TinyOS opts in favor of small frame
sizes at the cost of extremely low channel bandwidth utilization.
In this paper, we describe Seda: a streaming datalink
layer that resolves the above dilemma by decoupling framing
from error recovery. Seda treats the packets from the upper
layer as a continuous stream of bytes. It breaks the data
stream into blocks, and retransmits erroneous blocks only
(as opposed to the entire erroneous frame). Consequently,
the frame-error-rate (FER), the main factor that bounds the
frame size in the current design, becomes irrelevant to error
recovery. A frame can therefore be sufficiently large in
great favor of high utilization of the wireless channel bandwidth,
without compromising the effectiveness of error recovery.
Meanwhile, the size of each block is configured according
to the error characteristics of the wireless channel to
optimize the performance of error recovery. Seda has been
implemented as a new datalink layer in the TinyOS, and evaluated
through both simulations and experiments in a testbed
of 48 MicaZ motes. Our results show that, by increasing the
TinyOS frame size from the default 29 bytes to 100 bytes
(limited by the buffer space at MicaZ firmware), Seda improves
the throughput around 25% under typical wireless
channel conditions. Seda also reduces the retransmission
traffic volume by more than 50%, compared to a frame-based
retransmission scheme. Our analysis also exposes that future
sensor motes should be equipped with radios with more
packet buffer space on the radio firmware to achieve optimal
utilization of the channel capacity.
∗First two authors equally contributed to this work

Keywords
Throughput optimization, datalink layer, reliable communication,
sensor networks, wireless networks

دانلود مقاله OPERA: An Optimal Progressive Error Recovery Algorithm for Wireless Sensor Networks

اختصاصی از اس فایل دانلود مقاله OPERA: An Optimal Progressive Error Recovery Algorithm for Wireless Sensor Networks دانلود با لینک مستقیم و پر سرعت .

OPERA: An Optimal Progressive Error Recovery Algorithm for Wireless Sensor Networks
Saad Bin Qaisar and Hayder Radha
Department of Electrical and Computer Engineering
Michigan State University
East Lansing, MI-48824, United States

Abstract—Wireless Sensor Networks (WSNs) require
robustness against channel induced errors while retransmission
based schemes prove too costly for energy constrained
sensor nodes. Channel coding with low rates can
ensure increased reliability, and it can eliminate the need
for costly retransmissions. However, low channel coding
rates on an end-to-end basis (between a source sensor
and a destination base-station) requires a large number
of transmissions of redundant data. In this paper, we
propose an Optimal Progressive Error Recovery Algorithm
(OPERA) over WSNs. Under OPERA, individual
intermediate sensors, which are relaying data toward the
base station, partially and optimally channel-decode the
incoming packets while employing a progressive decrease
in parity bits as data reaches the final destination. OPERA
requires significantly lesser processing than would be
required for complete decoding or full decoding/encoding
at the sensor nodes; and OPERA significantly reduces the
total number of transmissions when compared to optimal
end-to-end channel coding schemes. We use iteratively
decodeable LDPC codes for this purpose. OPERA not
only provides a partial processing framework, but also
an algorithm to optimally map the decoding iterations
over the multi hop network. We provide a comparison
between our iteration assignment scheme and random
iteration assignment, and show that our scheme performs
considerably better. Finally, while being naturally motivated
by the sensor reachback problem, we further develop
a fairness-based OPERA scheme for the allocation of
channel-decoding LDPC iterations to sensor nodes taking
into consideration the life-expectancy of each sensor.

کاربرد تکنولوژی های Wireless در انتقال دیتا ، انواع و تفاوتهای آن

اختصاصی از اس فایل کاربرد تکنولوژی های Wireless در انتقال دیتا ، انواع و تفاوتهای آن دانلود با لینک مستقیم و پر سرعت .

مقاله با عنوان کاربرد تکنولوژی های Wireless در انتقال دیتا ، انواع و تفاوتهای آن در فرمت پی دی اف  در 14 صفحه و شامل مطالب زیر می باشد:

مقدمه
انواع فناوری Wireless
UWB
Wi-Fi
WiMax
3G