IEEE Wireless Communications • August 2013
64
1536-1284/13/$25.00 © 2013 IEEE
WIRELESS COMMUNICATIONS FOR E-HEALTH APPLICATIONS
INTRODUCTION
With the development of miniaturized, high-
performance, and low-power sensor nodes, and
the recent advances in wireless networking tech-
nologies, communications in or around human
body using wireless body area networks
(WBAN) have become practically feasible.
Healthcare community and engineering industry
have shown increased interests in WBAN, since
this emerging system provides efficiency to e-
Health applications, e.g., remote patient moni-
toring and medical care. The general
architecture of a WBAN-based system is illus-
trated in Fig. 1. WBAN is body-centric and it
comprises two categories of nodes: in-body, on-
body or around-body sensor nodes, and coordi-
nator equipped on human body. These nodes,
covering a short range (usually 2–3 m), usually
form a star-topology network, where the coordi-
nator and sensor nodes exchange data directly
in one-hop communication. Thus different types
of information regarding human body can be
collected and then transmitted to the coordina-
tor for analysis and display. Through wireless
and broadband network, the coordinator can
also forward data to remote servers. Thus body
area information, such as body vital signs,
human motions, and surrounding environment
status, can be collected without interrupting
people’s normal activities.
The most important issue we should consider
in WBAN is energy efficiency since sensor nodes
only have batteries with limited capacity and it is
inconvenient to recharge or replace the batter-
ies, especially for implanted sensors. Besides,
various kinds of sensor nodes, such as blood
pressure, heart rate, electrocardiogram (ECG),
electroencephalogram (EEG), have very differ-
ent demands in terms of data rate and latency.
These demands are usually dynamic and dictated
by the time-varying conditions of human body
and environment. For example, when a car-
diomyopathy patient is doing exercise, time-criti-
cal signals, such as heart rate and ECG, need to
be delivered in a real-time fashion rather than
the usual periodic transmission. Furthermore,
the robustness of WBAN should be guaranteed
against the channel fading in WBAN caused by
energy absorption, body movement, and multi-
path due to surrounding environment [1]. For
example, when one walks and moves his/her
arms or legs between some transmitter and
receiver antenna, transmitted packets may suffer
deep fading and packets loss. In order to combat
the aforementioned adversaries of WBAN, prop-
er channel access and resource allocation mecha-
nism is critically needed to control the
communications and duty cycle of nodes. There-
fore, designing an appropriate medium access
control (MAC) protocol for WBAN becomes
BIN LIU AND ZHISHENG YAN, UNIVERSITY OF SCIENCE AND TECHNOLOGY OF CHINA
CHANG WEN CHEN, THE STATE UNIVERSITY OF NEW YORK AT BUFFALO
ABSTRACT
Wireless Body Area Networks (WBAN) is a
promising low power technology that enables the
communications between body area sensor nodes
and a central coordinator. It targets at many
applications in e-Health services. In WBAN, dif-
ferent data sources generate time-varying traffic.
Large traffic volume may result in intolerant
latency and thus it is extremely important that
the most significant data can always be delivered
in a real-time fashion. Besides, data transmission
may suffer from deep fading and packets loss
due to the dynamic on-body channel induced by
movements and surrounding environment.
Hence, energy-efficient medium access control
(MAC) is crucially needed to allocate transmis-
sion bandwidth and to ensure reliable transmis-
sion considering WBAN contexts, i.e.,
time-varying human and environment conditions.
To improve both efficiency and reliability, we
investigate the challenges in the development of
WBAN MAC design. Furthermore, based on the
traffic nature and channel status, we introduce a
context-aware MAC protocol to meet time-vary-
ing requirements of WBAN. We have demon-
strated that the proposed protocol is able to
reduce latency, energy consumption, and packet
loss rate, as well as to achieve a reasonable
trade-off between efficiency and reliability.
MAC PROTOCOL IN WIRELESS BODY AREA
NETWORKS FOR E-HEALTH:
C
HALLENGES AND A CONTEXT-AWARE DESIGN
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