nesc language introduction. nesC is an extension to C [2] designed to embody the structuring concepts and execution model of
TinyOS [1]. TinyOS is an event-driven operating system designed for sensor network nodes that
have very limited resources (e.g., 8K bytes of program memory, 512 bytes of RAM). TinyOS has
been reimplemented in nesC. This manual describes v1.1 of nesC, changes from v1.0 are summarised
in Section 3.
The SP2526A device is a dual +3.0V to +5.5V USB Supervisory Power Control Switch ideal
for self-powered and bus-powered Universal Serial Bus (USB) applications. Each switch has
low on-resistance (110mΩ typical) and can supply 500mA minimum. The fault currents are
limited to 1.0A typical and the flag output pin for each switch is available to indicate fault
conditions to the USB controller. The thermal shutdown feature will prevent damage to the
device when subjected to excessive current loads. The undervoltage lockout feature will
ensure that the device will remain off unless there is a valid input voltage present.
According to the statistics of the Federal Communications Commission
(FCC), temporal and geographical variations in the utilization of the as-
signed spectrum range from 15% to 85%. The limited available radio spec-
trum and the inefficiency in spectrum usage necessitate a new commu-
nication paradigm to exploit the existing spectrum dynamically.
Cognitive radio has emerged as a promising technology for maximizing the utiliza-
tion of the limited radio bandwidth while accommodating the increasing amount of
services and applications in wireless networks. A cognitive radio (CR) transceiver
is able to adapt to the dynamic radio environment and the network parameters to
maximize the utilization of the limited radio resources while providing flexibility in
wireless access. The key features of a CR transceiver are awareness of the radio envi-
ronment (in terms of spectrum usage, power spectral density of transmitted/received
signals, wireless protocol signaling) and intelligence.
Providing QoS while optimizing the LTE network in a cost efficient manner is
very challenging. Thus, radio scheduling is one of the most important functions
in mobile broadband networks. The design of a mobile network radio scheduler
holds several objectives that need to be satisfied, for example: the scheduler needs
to maximize the radio performance by efficiently distributing the limited radio re-
sources, since the operator’s revenue depends on it.
At the macroscopic level of system layout, the most important issue is path loss. In the
older mobile radio systems that are limited by receiver noise, path loss determines SNR and
the maximum coverage area. In cellular systems, where the limiting factor is cochannel
interference, path loss determines the degree to which transmitters in different cells interfere
with each other, and therefore the minimum separation before channels can be reused.
Smartphones have become a key element in providing greater user access to the
mobile Internet. Many complex applications which used to be limited to PCs, have
been developed and operated on smartphones. These applications extend the
functionalities of smartphones, making them more convenient for users to be
connected. However, they also greatly increase the power consumption of
smartphones, making users frustrated with long delays in Web browsing.
Advances in communication and networking technologies are rapidly making ubiq-
uitous network connectivity a reality. Wireless networks are indispensable for
supporting such access anywhere and at any time. Among various types of wire-
less networks, multihop wireless networks (MWNs) have been attracting increasing
attention for decades due to its broad civilian and military applications. Basically,
a MWN is a network of nodes connected by wireless communication links. Due
to the limited transmission range of the radio, many pairs of nodes in MWNs may
not be able to communicate directly, hence they need other intermediate nodes to
forward packets for them. Routing in such networks is an important issue and it
poses great challenges.
This book is about multipoint cooperative communication, a key technology to
overcome the long-standing problem of limited transmission rate caused by inter-
point interference. However, the multipoint cooperative communication is not an
isolated technology. Instead, it covers a vast range of research areas such as the
multiple-input multiple-outputsystem, the relay network, channel state information
issues, inter-point radio resource management operations, coordinated or joint
transmissions, etc. We suppose that any attempt trying to thoroughly analyze the
multipoint cooperative communication technology might end up working on a
cyclopedia for modern communication systems and easily get lost in discussing all
kinds of cooperative communication schemes as well as the associated models and
their variations.
This book is a result of the recent rapid advances in two related technologies: com-
munications and computers. Over the past few decades, communication systems
have increased in complexity to the point where system design and performance
analysis can no longer be conducted without a significant level of computer sup-
port. Many of the communication systems of fifty years ago were either power or
noise limited. A significant degrading effect in many of these systems was thermal
noise, which was modeled using the additive Gaussian noise channel.
