260
Within the latter category falls the IoT vision of the IPSO
261
(IP for Smart Objects) Alliance [11], a forum formed in Sep-
262
tember 2008 by 25 founding companies to promote the
263
Internet Protocol as the network technology for connecting
264
Smart Objects around the world. According to the IPSO vi-
265
sion, the IP stack is a light protocol that already connects a
266
huge amount of communicating devices and runs on tiny
267
and battery operated embedded devices. This guarantees
268
that IP has all the qualities to make IoT a reality. By reading
269
IPSO whitepapers, it seems that through a wise IP adapta-
270
tion and by incorporating IEEE 802.15.4 into the IP archi-
271
tecture, in the view of 6LoWPAN [12], the full
272
deployment of the IoT paradigm will be automatically
273
enabled.
274
Internet Ø [13] follows a similar approach of reducing
275
the complexity of the IP stack to achieve a protocol de-
276
signed to route ‘‘IP over anything”. In some forums this is
277
looked at as the wisest way to move from the Internet of
278
Devices to the Internet of Things. According to both the
279
IPSO and Internet Ø approaches, the IoT will be deployed
280
by means of a sort of simplification of the current IP to
281
adapt it to any object and make those objects addressable
282
and reachable from any location.
283
As said before, it is worth noticing that ‘‘Semantic ori-
284
ented” IoT visions are available in the literature [14–17].
285
The idea behind them is that the number of items involved
286
in the Future Internet is destined to become extremely
287
high. Therefore, issues related to how to represent, store,
288
interconnect, search, and organize information generated
289
by the IoT will become very challenging. In this context,
290
semantic technologies could play a key role. In fact, these
291
can exploit appropriate modeling solutions for things
292
description, reasoning over data generated by IoT, seman-
293
tic execution environments and architectures that accom-
294
modate IoT requirements and scalable storing and
295
communication infrastructure [14].
296
A further vision correlated with the IoT is the so called
297
‘‘Web of Things” [18], according to which Web standards
298
are re-used to connect and integrate into the Web every-
299
day-life objects that contain an embedded device or
300
computer.
301
3. Enabling technologies
302
Actualization of the IoT concept into the real world is
303
possible through the integration of several enabling tech-
304
nologies. In this section we discuss the most relevant ones.
305
Note that it is not our purpose to provide a comprehensive
306
survey of each technology. Our major aim is to provide a
307
picture of the role they will likely play in the IoT. Interested
308
readers will find references to technical publications for
309
each specific technology.
310
3.1. Identification, sensing and communication technologies
311
‘‘Anytime, anywhere, anymedia” has been for a long
312
time the vision pushing forward the advances in communi-
313
cation technologies. In this context, wireless technologies
314
have played a key role and today the ratio between radios
315
and humans is nearing the 1 to 1 value [19].
316
However, the reduction in terms of size, weight, energy
317
consumption, and cost of the radio can take us to a new era
318
where the above ratio increases of orders of magnitude.
319
This will allow us to integrate radios in almost all objects
320
and thus, to add the world ‘‘anything” to the above vision,
321
which leads to the IoT concept.
322
In this context, key components of the IoT will be RFID
323
systems [20], which are composed of one or more reader(s)
324
and several RFID tags. Tags are characterized by a unique
325
identifier and are applied to objects (even persons or ani-
326
mals). Readers trigger the tag transmission by generating
327
an appropriate signal, which represents a query for the
328
possible presence of tags in the surrounding area and for
329
the reception of their IDs. Accordingly, RFID systems can
330
be used to monitor objects in real-time, without the need
331
of being in line-of-sight; this allows for mapping the real
332
world into the virtual world. Therefore, they can be used
333
in an incredibly wide range of application scenarios, span-
334
ning from logistics to e-health and security.
335
From a physical point of view a RFID tag is a small
336
microchip
1
attached to an antenna (that is used for both
337
receiving the reader signal and transmitting the tag ID) in
338
a package which usually is similar to an adhesive sticker
339
[21]. Dimensions can be very low: Hitachi has developed a
340
tag with dimensions 0.4 mm 0.4 mm 0.15 mm.
341
Usually, RFID tags are passive, i.e., they do not have on-
342
board power supplies and harvest the energy required for
343
transmitting their ID from the query signal transmitted
344
by a RFID reader in the proximity. In fact, this signal gener-
345
ates a current into the tag antenna by induction and such a
346
current is utilized to supply the microchip which will
347
transmit the tag ID. Usually, the gain (power of the signal
348
received by the reader divided by the power of the signal
349
transmitted by the same reader) characterizing such sys-
350
tems is very low. However, thanks to the highly directive
351
antennas utilized by the readers, tags ID can be correctly
352
received within a radio range that can be as long as a
353
few meters. Transmission may occur in several frequency
354
bands spanning from low frequencies (LF) at 124–
355
135 kHz up to ultra high frequencies (UHF) at 860–
356
960 MHz that have the longest range.
357
Nevertheless, there are also RFID tags getting power
358
supply by batteries. In this case we can distinguish semi-
359
passive from active RFID tags. In semi-passive RFIDs batter-
360
ies power the microchip while receiving the signal from
361
the reader (the radio is powered with the energy harvested
362
by the reader signal). Differently, in active RFIDs the bat-
363
tery powers the transmission of the signal as well. Obvi-
364
ously the radio coverage is the highest for active tags
365
even if this is achieved at the expenses of higher produc-
366
tion costs.
367
Sensor networks will also play a crucial role in the IoT.
368
In fact, they can cooperate with RFID systems to better
369
track the status of things, i.e., their location, temperature,
370
movements, etc. As such, they can augment the awareness
371
of a certain environment and, thus, act as a further bridge
372
between physical and digital world. Usage of sensor net-
1
New RFID tags, named chipless tags, are under study which do not use
microchips so as to decrease production cost [Ted09]
Q2
.
4 L. Atzori et al. / Computer Networks xxx (2010) xxx–xxx
COMPNW 4247 No. of Pages 19, Model 3G
31 May 2010
Please cite this article in press as: L. Atzori et al., The Internet of Things: A survey, Comput. Netw. (2010), doi:10.1016/
j.comnet.2010.05.010