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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
Radio Networks
Riccardo Cavallari
+39 051 20 93180
Office:
3rd floor, Main Building
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
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Wireless Body Area Networks (WBAN) and
IEEE 802.15.6 Standard
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
Outline 1. Introduction
• Definitions and Application Scenarios
• Standardization
2. Physical (PHY) Layer
3. Medium Access Control (MAC) Layer
• Beacon Mode with beacon periods (superframes)
• Non-Beacon Mode with superframes
• Non-Beacon Mode without superframes
5. Coexistence techniques
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
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Outline 1. Introduction
• Definitions and Application Scenarios
• Standardization
2. Physical (PHY) Layer
3. Medium Access Control (MAC) Layer
• Beacon Mode with beacon periods (superframes)
• Non-Beacon Mode with superframes
• Non-Beacon Mode without superframes
5. Coexistence techniques
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
Wireless Body Area Networks (WBANs)
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WBAN:
• Collection of nodes placed on, or inside,
the human body (but not limited to).
• Nodes have sensing and/or actuating
and communication capabilities.
Applications:
• Medical: monitoring vital parameters,
hearing aids, cardiac implant, etc.
• Sport/Fitness: rehabilitation, motion capture,
monitoring parameters;
• Entertainment: consumer electronics (audio/video streaming,
interactive gaming), personal item tracking.
WiserBAN EU Project: realizes a miniaturized and ultra-low power RF microsystem, for
medical and multimedia applications.
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
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Outline 1. Introduction
• Definitions and Application Scenarios
• Standardization
2. Network Topology
3. Physical (PHY) Layer
4. Medium Access Control (MAC) Layer
• Beacon Mode with beacon periods (superframes)
• Non-Beacon Mode with superframes
• Non-Beacon Mode without superframes
5. Coexistence techniques
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
Standard IEEE 802.15.6 (final release, Feb. 2012)
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• Different applications leads to different technical requirements unique standard
IEEE 802.15 Task Group 6 (November 2007):
• Define the Physical (PHY) and Medium Access Control (MAC) Layers for short range,
low complexity, low cost, ultra-low power and high reliable wireless communication in,
on or around the human body.
High level application requirements
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
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Outline 1. Introduction
• Definitions and Application Scenarios
• Standardization
2. Physical (PHY) Layer
3. Medium Access Control (MAC) Layer
• Beacon Mode with beacon periods (superframes)
• Non-Beacon Mode with superframes
• Non-Beacon Mode without superframes
5. Coexistence techniques
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
Physical (PHY) Layer
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• 3 different PHY
• Modulation @ 2.45GHz
Packet
Component Modulation
Symbol Rate
(ksps)
Spreading
Factor
(S)
Information
Data Rate
(kbps)
PSDU π/2-DBPSK 600 4 121.4
PSDU π/2-DBPSK 600 2 242.9
PSDU π/2-DBPSK 600 1 485.7
PSDU π/4-DQPSK 600 1 971.4
• N° of Channel @ 2.45GHz:
79 Channel of 1MHz Bandwidth
• Min Tx Power:
-10 dBm EIRP
• Receiver Sensitivity @ 2.45GHz:
Frequency Band (MHz)
Information Data Rate
(kbps)
Minimum Sensitivity
(dBm)
2400 – 2483.5
121.4 –92
242.9 –90
485.7 –87
971.4 –83
Narrowband
2483.5 5 50
2360 2400 3100 10600 402 405
420 450
863 870 902 928
958 950
HBC MICS WMTS
Japan Europe
ISM
North America Australia
New Zeland WorldWide Japan
UWB f [ MHz ] ISM
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
Data rates
PHY
Frequency band
(MHz), center
frequency
(MHz), or
modulation
Data rate 0 (kb/s)
Data rate 1 (kb/s)
Data rate 2 (kb/s)
Data rate 3 (kb/s)
Data rate 4 (kb/s)
Data rate 5 (kb/s)
Data rate 6 (kb/s)
Data rate 7 (kb/s)
Narrow band
(NB)
402 to 405 75.9 151.8 303.6 455.4 Rsvd Rsvd Rsvd Rsvd
420 to 450 75.9 151.8 187.5 Rsvd Rsvd Rsvd Rsvd Rsvd
863 to 870 101.2 202.4 404.8 607.1 Rsvd Rsvd Rsvd Rsvd
902 to 928 101.2 202.4 404.8 607.1 Rsvd Rsvd Rsvd Rsvd
950 to 958 101.2 202.4 404.8 607.1 Rsvd Rsvd Rsvd Rsvd
2360 to 2400 121.4 242.9 485.7 971.4 Rsvd Rsvd Rsvd Rsvd
2400 to 2483.5 121.4 242.9 485.7 971.4 Rsvd Rsvd Rsvd Rsvd
Ultra wideband (UWB)
Non- coherent 394.8 789.7 1579 3159 6318 12 636 Rsvd Rsvd
Differentially
coherent 487 975 1950 3900 7800 15 600 557 1114
FM 202.5 Rsvd Rsvd Rsvd Rsvd Rsvd Rsvd Rsvd
Human body
communica-
tions (HBC)
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164
328
656
1312.5
Rsvd
Rsvd
Rsvd
Rsvd
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
PHY Protocol Data Unit (PPDU)
PLCP Preamble PLCP Header PSDU
HCSBCH
Parity BitsPHY Header
4 bits 12 bits15 bits 7 bytes 2 bytes
MAC
HeaderFCS
MAC Frame Body
Variable Length: 0 – 255 bytes
RATE LENGTHBURST
MODEReserved
3 bits 8 bits1 bit
Reserved
1 bit
SCRAMBLER
SEED
1 bit 1 bit
•Packet detection
•Time synchronization
•Carrier off-set recovery
• It conveys PHY parameters needed at
the Rx to decode the PSDU:
a) Length and Data Rate of MAC
packet
b) Header check sequence
c) BCH encoder to improve header
robustness
• Physical layer Service Data Unit:
contains the MAC frame
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
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Outline 1. Introduction
• Definitions and Application Scenarios
• Standardization
2. Physical (PHY) Layer
3. Medium Access Control (MAC) Layer
• Beacon Mode with beacon periods (superframes)
• Non-Beacon Mode with superframes
• Non-Beacon Mode without superframes
5. Coexistence techniques
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
MAC Access Modes and Phases 1/4
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1. Beacon Mode with superframe: beacons at the beginning of each superframe to
establish a common time base for time referenced allocations;
Random Access Phases
CSMA/CA Access Method : • Backoff counter (BC) in the interval [0-CW],
• BC is decremented by one, for each
successive idle CSMA time slot;
• When BC=0, the node obtains a contended
allocation during which the TX occurs.
Contention between nodes: allocations are non-recurring time intervals valid per instance
of access.
EAP (Exclusive Access Phase): for high priority traffic.
RAP (Random Access Phase): for regular traffic.
Slotted Aloha Access Method: • Contention Probability (CP) properly set;
• z =random in the interval [0-1];
• If z≤CP the node obtains a contended
allocation in the current Aloha slot, during
which the TX occurs .
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
CSMA/CA access illustration
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RAP1
Data
arrives
Tf
Slot = CSMA slot SIFS = pSIFS
F1 = frame transaction initiated by node 1 in a contended allocation (e.g., a data type frame and an I-Ack frame with pSIFS in between)
Tf = time required to complete F1 GTn = nominal guard time
Slo
t
CW = CWmin = 8;
backoff counter is set
to 3 over [1, CW] and
unlocked.
SIF
S
Slo
tS
lot F1
Backoff
counter (= 0)
Contention fails 1st time.
CW is not changed;
backoff counter is reset to
5 over [1, CW] and locked.
CAP
Slo
t
Backoff
counter (= 5)
is unlocked
Slo
tS
lot
No enough time is
left; backoff counter
(= 2) is locked.
Slo
t
Tf Tf
RAP2
Slo
tS
lot F1
Contention fails 2nd
time.
CW = 16 (doubled);
backoff counter is reset
to 8 over [1,CW] and
locked
Backoff
counter (= 2)
is unlocked.
Slo
tS
lot
Backoff
counter (= 8)
is unlocked
Backoff
counter (= 0)
Slo
tS
lot
Slo
tS
lot
Slo
t F1
Backoff
counter (= 0)
Slo
t
Contention succeeds.
CW is reset to CWmin;
backoff counter is reset to 2
over [1, CW] and locked
Backoff counter decrements
Tf
SIF
S
SIF
S
SIF
S
Priority User Priority Traffic designation CWmin CWmax
Lowest
Highest
0 Background (BK) 16 64
1 Best effort (BE) 16 32
2 Excellent effort (EE) 8 32
3 Controlled load (CL) 8 16
4 Video (VI) 4 16
5 Voice (VO) 4 8
6 Medical data or network
control
2 8
7 Emergency or medical event
report
1 4
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
Slotted Aloha access illustration
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RAP1
F1 = frame transaction initiated by node 1 in a contended allocation (e.g., a management type frame and an I-Ack frame with pSIFS in between)
CAP RAP2
Aloha
slot
Aloha
slot
Aloha
slot
Aloha
slot
Aloha
slot
Aloha
slot
Aloha
slot
Aloha
slot
CP = CPmax = 1/2.
Node 1 does not
obtain a
contended
allocation.
CP =1/2.
Node 1 obtains a
contended allocation
and sends a frame
which then fails.
F1
CP = 1/2 (unchanged).
Node 1 obtains a
contended allocation
and sends a frame
which then fails again.
F1
CP = 1/4 (halved).
Node 1 does not
obtain a
contended
allocation.
CP = 1/4.
Node 1 does
not obtain a
contended
allocation.
CP = 1/4.
Node 1 does
not obtain a
contended
allocation.
CP = 1/4.
Node 1 obtains a
contended allocation
and sends a frame
which then succeeds.
F1
CP is reset to CPmax.
Node 1 does not
obtain a
contended
allocation.
Priority User Priority Traffic designation CPmax CPmin
Lowest
Highest
0 Background (BK) 1/8 1/16
1 Best effort (BE) 1/8 3/32
2 Excellent effort (EE) 1/4 3/32
3 Controlled load (CL) 1/4 1/8
4 Video (VI) 3/8 1/8
5 Voice (VO) 3/8 3/16
6 Medical data or network
control
1/2 3/16
7 Emergency or medical event
report
1 1/4
z = rand[0,1]
z ≤ CP to transmit
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
MAC Access Modes and Phases 2/4
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Managed Access Phase
Beacon period (superframe) n Beacon period (superframe) n+1
Allocation
interval
Allocation
interval
Allocation
interval
...
Beacon period (superframe) …
7 8 9 7 8 9 7 8 9
Beacon period (superframe) n Beacon period (superframe) n+1
...
Beacon period (superframe) n+m
1 2Allocation
interval
1 2Allocation
interval
Access to the channel is managed by the hub
• Scheduled Access Method:
1-periodic scheduled allocation: one or
more allocation intervals, of the same
temporal length, are granted to the
node in every superframe. Suitable for
high duty cycle periodic or quasi-
periodic traffic. (e.g., streaming)
m-periodic scheduled allocation: one or
more allocation intervals, of the same
temporal length, are granted to the
node every m>1 superframe. Suitable
for low duty cycle periodic or quasi-
periodic traffic. (e.g., status signals)
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
MAC Access Modes and Phases 3/4
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• Improvised Access Methods:
for on-demand contention-free frame exchange outside scheduled allocations
Hub
transmits
Node 1
transmits
Data(B-
Ack)
B-A
ck+
Po
ll
Data(I-Ack)
Po
ll
Data(L-
Ack)
Data(B-
Ack)
B-A
ck+
Po
ll
Scheduled uplink
allocation interval
Data(I-Ack)
I-Ack
Data(I-Ack)
I-Ack
I-A
ck+
Po
ll
Data(I-Ack)
I-Ack P
oll
Data(I-Ack)
I-Ack
Scheduled downlink
allocation interval
Post
Data(L-
Ack)
Po
ll
Immediate Future Immediate Future
Polled
allocation
interval
Polled
Allocation interval
Polled
Allocation
interval
ImmediateImmediate Immediatea) Polling Access: the hub grants to
the node one or more non-
reoccuring time intervals for
initiating one or more frame
transactions by the node
uplink! Suitable for “ordinary”,
“unexpected” or “extra” traffic.
E.g., error signaling.
Hub
transmits
Node 1
transmits
Data(L-
Ack)
Data(B-
Ack)
B-A
ck
Scheduled uplink
allocation interval
Post
Data(I-Ack)
I-Ack
Data(I-Ack)
Post
I-Ack
Scheduled downlink
allocation interval
Post
Data(I-Ack)
Data(I-Ack)
Data(L-Ack)
Data(B-
Ack)
B-A
ck
Post
Data(L-Ack)
Data(B-
Ack)
B-A
ck
Post Post
Posted
allocation interval
Posted
allocation interval
Immediate ImmediateFuture Immediate Immediate Immediate
I-Ack
Data(I-Ack)
I-Ack
I-Ack
a) Posting Access: the hub grants to
itself one or more non-reoccuring
time intervals for initiating one or
more frame transactions
downlink! Suitable for
“unexpected” or “extra” traffic. E.g.,
BAN management information.
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
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Outline
1. Introduction
• Definitions and Application Scenarios
• Standardization
2. Physical (PHY) Layer
3. Medium Access Control (MAC) Layer
• Beacon Mode with beacon periods (superframes)
• Non-Beacon Mode with superframes
• Non-Beacon Mode without superframes
5. Coexistence techniques
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
MAC Access Modes and Phases 4/4
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2. Non-Beacon Mode with superframes:
no beacons but superframe and
allocation slots are established
because the channel access involves
time referencing. Only MAP.
3. Non-Beacon Mode without superframes:
no beacons; superframe and allocation
slots are not established because the
allocation involves no time referencing.
• Unscheduled Access Method:
A hub may provide unscheduled reoccuring polled or posted allocations, nodes
may use CSMA/CA to obtain a contended allocation.
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
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Outline
1. Introduction
• Definitions and Application Scenarios
• Standardization
2. Physical (PHY) Layer
3. Medium Access Control (MAC) Layer
• Beacon Mode with beacon periods (superframes)
• Non-Beacon Mode with superframes
• Non-Beacon Mode without superframes
5. Coexistence techniques
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
Coexistence with other BANs
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• Coexistence Techniques:
a) Beacon Shifting: in order to mitigate potential beacon collisions and
schedule allocation conflicts the hub transmits its beacons at different time
offset, according to a particular beacon shifting sequence, not being used
by other neighbor hubs.
b) Channel Hopping: the hub changes its operating channel periodically
according to a particular channel hopping sequence, not being used by
other neighbor hubs. The node shall hop to the same channel to remain
connected with its hub.
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
References
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1. 15-08-0644-09-0006-tg6-technical-requirements-document, November 2008.
2. Kwak K.S, Ameen M.A, Kwak D, Lee C, Lee H; “A Study on proposed IEEE
802.15 WBAN MAC protocols”, ISCIT December 2009.
3. Massè F, Penders J; “Quality-of-Service in BAN: PER reduction and its trade-offs”;
International conference on BSN July 2010.
4. 15-08-0780-11-0006-tg6-channel-model, September 2010.
5. 15-08-0034-15-0006-ieee-802-15-6-regulation-subcommittee-report, May 2010.
6. IEEE Standard for Local and metropolitan area networks - Part 15.6: Wireless
Body Area Networks," IEEE Std 802.15.6-2012 , vol., no., pp.1,271, Feb. 29 2012.
7. Reichmann A; “Standardization of Body Area Networks”; COMCAS January 2010.
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Riccardo Cavallari DEI, Università di Bologna
Radio Networks
Radio Networks
Riccardo Cavallari
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