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1.
Learning
objectives:
a)
Understand the motivation of link estimation protocols and the time
varying nature of a wireless channel;
b)
Understand the metric of ETX;
c)
Understand the four-bit link estimation;
d)
Understand the impact of link estimation on representative TinyOS network
protocols.
2.
Prerequisites:
Module 2, plus a). Basic
concepts of wireless communications; b). Basic concepts of computer networks.
3.
Module
description:
WSNs demonstrate unique radio communication
patterns, including radio irregularity, anisotropic signal strength, and
anisotropic packet loss ratio. All these factors have dramatic impact on
higher layer protocols like MAC and their design and implementation. In our
course modules, we use detailed experimental data to illustrate the relevant
concepts.
We start with the introduction to some basic concepts about wireless
communications, including signal, dB, dBm, Received Signal Strength Indicator
(RSSI), Link Quality Indicator (LQI), and noise floor. These concepts are
frequently used in many WSN papers. We then introduce MAC protocols which
coordinate nodes to access shared wireless channels. The essential
requirements of MAC protocols are energy efficiency, effective collision
avoidance, efficient channel utilization, and scalability. We present a classification
of MAC protocols in order for students to have a high-level conception. We
focus on the introduction of Time Division Multiple Access (TDMA) and Carrier
Sense Multiple Access (CSMA) protocols. Finally we introduce the details of
B-MAC, which is a core module implemented in TinyOS. We focus on important
concepts including Clear Channel Access (CCA) and Sleep/Wake scheduling using
Low Power Listening (LPL), which are unique to WSN design. We also introduce
other important MAC protocols including S-MAC and X-MAC.
4. Tools utilized:
MicaZ motes and TelosB motes are used as the
example hardware platforms to illustrate important concepts in this module.
5. Requirements:
Students are required to read related papers and
understand presented ideas. After these steps, students are then encouraged to
go through TinyOS CVS tree to have a deeper understanding of presented
protocols.
6. Assignments and Hands-on projects:
Students are required to add Low Power Listening
(LPL) feature to the Ping-Pong application. To do this, students need to
invoke relevant LPL interfaces provided by TinyOS. Detailed
Lab description
+ Assignment
7.
Level of
difficulty: This module is
classified as a module of intermediate difficulty.
8.
Grading/evaluation
criteria: Graders
need to see a demo of the Ping-Pong application and that of the multi-hop data collection tree protocol submitted by students.
9.
PowerPoint
slides: radio_MAC.ppt
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