IEEE Solid-State Circuits Magazine - Fall 2017 - 38

Things [14]. While not yet able to
reach the very low peak power con-
sumption (<10 mA) and extended
range (>10 m) of a custom protocol,
wearable wireless patient monitoring
patches based on BTLE have started
to become commercially available,
e.g., [15] and [16]. Moreover, recent
publications have demonstrated
BTLE transceivers operating at a
lower than 10 mA peak current, and
while not yet commercially avail-
able, such products can be expected
to appear on the market in the near
future [17]-[19].

Wireless Communication
for Intensive Care Monitoring
Replacing wired cables in the ICU with
wireless communication presents a
significant challenge at low power
consumption, which, in this applica-
tion, is also highly desirable to mini-
mize size and maximize battery life.
For ICU monitoring, the required
data rate is dominated by the need
to stream multiple leads ECG, which
for a 15-lead ECG requires around
120 kb/s. Adding more capability
to support the monitoring of other
vital signs, including respirator y

250
200
150
1 Packet/Event
2 Packet/Event
3 Packet/Event
4 Packet/Event
5 Packet/Event

100
50
0

6 Packet/Event
7 Packet/Event
8 Packet/Event
9 Packet/Event
10 Packet/Event

16
24
32
40
48
56
64
72
80
88
96
104
112
120
128
136
144
152
160
168
176
184
192
200
208
216
224
232
240
248
256

Effective Througput (kb/s)

300

Packet Size (bytes)
FIGURE 2: Effective data throughput versus packet size for BTLE 4.2.

700
Target Application Throughput (kb/s)
600
500

606

Effective Application Throughput (kb/s)
498

498

498

498

498

590
498

528

498

450

400
300

248

200

FIGURE 3: The relative effective throughput of different wireless technologies.

38

FA L L 2 0 17

IEEE SOLID-STATE CIRCUITS MAGAZINE

BT-EDR
(3 Mb/s)

BT-EDR
(2 Mb/s)

802.15.6
RATE4

802.15.6
RATE3

BT4.2
(BER=1E-4)

44
BT4.0
(BER = 1E-4)

0

BT4.0
(BER = 1E-3)

100

148

waveform and rate and photo ple -
thysmography waveform for blood
oxygen saturation, gave an appli-
cation data rate requirement of
166 kb/s.
Equally important for ICU stream-
ing are the wireless QoS parameters
that need to be achieved. In addition
to the data throughput of 166 kb/s,
the application requires a latency of
<250 ms with a reliability of <25 ms
data drop out in any 10-min period
(i.e., data loss lower than 50 parts
per million). Such a high reliability
is usually achieved using strong for-
ward error correction combined with
message acknowledgment and retry.
But in our application, this would
lead to an unacceptable latency from
patient measurement to display.
Therefore, we chose to implement
redundancy through frequency di-
versity; with a data throughput of
166 kb/s per frequency channel
and three time the frequency diver-
sity, we require an application data
throughput of 498 kb/s.
To select an appropriate wire-
less technology for this monitor-
ing application, simulations were
performed using models of many
different wireless protocols with the
potential to operate in the dedicated
MBANS frequency bands at ~2.4 GHz.
The protocols selected were BTLE
(1 Mb/s raw data rate), Bluetooth-
extended data rate (EDR) [differen-
tial quadrature phase-shift keying
(DQPSK) and 8PSK modes giving 2
and 3 Mb/s data rates, respectively],
and IEEE 802.15.6.
The IEEE 802.15.6 protocol was
developed specifically for the imple-
mentation of wireless body area
networks, including medical device
applications, and thus has many
security and reliability features built
in while still supporting low-power
implementation [20]. The 802.15.6
protocol was simulated for RATE3 and
RATE4 modes giving raw data rates of
600 kb/s and 1.2 Mb/s, respectively.
Simulations were carried out for each
protocol, varying the packet size from
the minimum to maximum allowed
and adjusting the number of packets
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