IEEE Consumer Electronics Magazine - October 2015 - 58

Table 2. Transport time on air.
scenario

6loWPan 6loWPan 6loBtlE 6loBtlE aIos/
First
later
First
later
BlE

Application

802.15.4

IPSP/BLE

BLE

Total data

107

106

data rate
(Mb/s)

0.25

1.0

Air time
(ms)

3.424

2.368

0.848

0.584

0.168

shorten the IPv6 addresses to 16 bits for source and
address, saving 28 octets (224 bits)
▼ shorten the UDP port numbers to 4 bits, saving 3 octets (24 bits)
▼ omit the UDP checksum, trusting the underlying radio
media access control (MAC) for error detection (2 octets).
So, on the first use, 6LoWPAN or 6LoBTLE adds 2 octets.
On subsequent use, they save 33 octets (264 bits) (Table 1).
▼

6LoWPAN TRANSPoRT
IEEE 802.15.4 has MAC and PHY layers [26]. For this example, the 802.15.4 MAC will include the frame control, the
sequence number, the authentication (device-to-device), and
the frame check sequence and omit the source and destination

Alice has a
secret
message to
send to Bob.

BLUETOOTH LOW ENERGY TRANSPORT
The Bluetooth Low Energy transport for 6LoBTLE includes
the PHY, link layer, and L2CAP, with an extra feature called
"connection-oriented channels" defined in Bluetooth Core
Specification v4.1 [44]. The Bluetooth SIG defined the Internet
Protocol Support Profile (IPSP) [45], described in a previous
article [25]. For device-to-device security, a message authentication will be included, this is 4 octets [46]. The PHY will add
a preamble, a channel access code, and a CRC, for 8 octets.
The total overhead will be 18 octets (144 bits). The Bluetooth
Low-Energy radio has a data rate of 1 Mb/s.
The main performance difference is that the PHY itself is
four times faster for Bluetooth Low Energy. If the other
resources are equal, this will be a four times difference in
power consumption. However, for most sensors, the cost of
wireless transmission is only part of the whole device power.

BLUETOOTH LOW ENERGY APPLICATION
If the sensor or actuator is local to the host device (e.g.,
gateway), a simpler protocol can be used. The Bluetooth
SIG had defined an application (profile) specification that is
similar to IPSO digital and analog IO ports, called the AIOS
[47]. Like ISPO objects, AIOS will have characteristics (like
IPSO resources). The applications message will be a 16-bit
characteristic handle and a 16-bit analog value.
The overhead is much simpler: L2CAP (4 octets), security
(4 octets), and 8 octets at the PHY, for a total of 16 octets
(128 bits). These can be seen in Table 2.
AIOS is much more efficient than 6LoBTLE, because it
omits addressing across the network. This may allow a device
to run on coin cells or scavenged power like a photocell. The
system design suggestion is to terminate IPv6 addressing at a
gateway within a home, allowing very low power end nodes.

SECURITY AND PRIVACY

1) Alice composes
a secret message,
inserts it into a
box, locks it with
her key, and sends
it to Bob.

2) Bob receives the
box. He adds a second
lock using his key,
and sends it back
to Alice.

3) Alice receives
the returned box.
She removes her
first lock with her
key and returns it
to Bob.

4) Bob receives the
box a second time.
He removes the
second lock using
his key and
recovers the secret
message.

FIGURE 3. Alice sends a secret to Bob.
58 IEEE ConsumEr ElECtronICs magazInE

PAN addresses. This will add 13 octets (104 bits). The
802.15.4 must include the preamble, the SFD, and a length, for
six additional octets (48 bits). The common 802.15.4 radio has
a data rate of 250 kb/s.

october 2015

Device and system designers routinely focus first on getting a
system to work and then making it secure. If a device or system works, customers will still be concerned with security
and privacy: Can they trust it? Security and privacy must to
be forethoughts, not bolted on later.
Anyone familiar with current events knows the dangers of
untrustworthy devices and systems.
▼ Our databases can be hacked [48].
▼ Our homes can be hacked [49].
▼ Our cars can be hacked [50].
▼ Our bodies can be hacked [51].
Eugene Kaspersky, CEO of security product firm Kaspersky Lab, characterizes the IoT as the Internet of Threats [52].
We may look back on today as the "good old days," before
hackers invade our lives even more than they already do. There
are actually several aspects to making a system trustworthy.

Table of Contents for the Digital Edition of IEEE Consumer Electronics Magazine - October 2015