Wireless/Cellular Technologies

Report
Wireless/Cellular Technologies
Prabhaker Mateti
Mobile Communication Technology
according to IEEE (examples)
WiFi
Personal wireless nw
WPAN 802.15
ZigBee
802.11a
802.11h
802.11b
802.11g
802.15.4
802.15.5, .6 (WBAN)
802.15.4a/b/c/d/e/f/g
802.15.3b/c
802.15.1
802.15.2
802.15.3
Bluetooth
Wireless distribution networks
WMAN 802.16 (Broadband WirelessWiMAX
Access)
CEG436: Mobile Computing (PM)
+ Mobility
[802.20 (Mobile Broadband Wireless Access)]
802.16e (addition to .16 for mobile devices) 2
Mobile Communications
Schiller Chapter 3 : Media Access
• Motivation
• SDMA, FDMA, TDMA
• Aloha, reservation schemes
• Collision avoidance, MACA
• Polling
• CDMA, SAMA
• Comparison
Motivation
• Can we apply media access methods from fixed/wired networks?
• Example CSMA/CD
– Carrier Sense Multiple Access with Collision Detection
– send as soon as the medium is free, listen into the medium if a
collision occurs (legacy method in IEEE 802.3)
• Problems in wireless networks
– signal strength decreases proportional to the square of the distance
– the sender would apply CS and CD, but the collisions happen at the
receiver
– it might be the case that a sender cannot “hear” the collision, i.e., CD
does not work
– furthermore, CS might not work if, e.g., a terminal is “hidden”
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Motivation - hidden and exposed
terminals
• Hidden terminals
–
–
–
–
A sends to B, C cannot receive A
C wants to send to B, C senses a “free” medium (CS fails)
collision at B, A cannot receive the collision (CD fails)
A is “hidden” for C
A
B
C
• Exposed terminals
–
–
–
–
B sends to A, C wants to send to another terminal (not A or B)
C has to wait, CS signals a medium in use
but A is outside the radio range of C, therefore waiting is not necessary
C is “exposed” to B
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Motivation - near and far terminals
• Terminals A and B send, C receives
– signal strength decreases proportional to the square of the distance
– the signal of terminal B therefore drowns out A’s signal
– C cannot receive A
A
B
C
• If C for example was an arbiter for sending rights, terminal B would drown
out terminal A already on the physical layer
• Also severe problem for CDMA-networks - precise power control needed!
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Access methods SDMA/FDMA/TDMA
• SDMA (Space Division Multiple Access)
– segment space into sectors, use directed antennas
– cell structure
• FDMA (Frequency Division Multiple Access)
– assign a certain frequency to a transmission channel between a sender
and a receiver
– permanent (e.g., radio broadcast), slow hopping (e.g., GSM), fast
hopping (FHSS, Frequency Hopping Spread Spectrum)
• TDMA (Time Division Multiple Access)
– assign the fixed sending frequency to a transmission channel between
a sender and a receiver for a certain amount of time
• The multiplexing schemes presented in chapter 2 are now used to
control medium access.
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MACA variant: DFWMAC in IEEE802.11
sender
receiver
idle
idle
packet ready to send; RTS
RxBusy
ACK
time-out 
NAK;
RTS
wait for the
right to send
time-out;
RTS
data;
ACK
CTS; data
wait for
data
wait for ACK
ACK: positive acknowledgement
NAK: negative acknowledgement
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RTS;
CTS
time-out 
data;
NAK
RxBusy: receiver busy
RTS; RxBusy
8
Polling mechanisms
• If one terminal can be heard by all others, this “central” terminal
(a.k.a. base station) can poll all other terminals according to a
certain scheme
– now all schemes known from fixed networks can be used (typical
mainframe - terminal scenario)
• Example: Randomly Addressed Polling
– base station signals readiness to all mobile terminals
– terminals ready to send can now transmit a random number without
collision with the help of CDMA or FDMA (the random number can be
seen as dynamic address)
– the base station now chooses one address for polling from the list of
all random numbers (collision if two terminals choose the same
address)
– the base station acknowledges correct packets and continues polling
the next terminal
– this cycle starts again after polling all terminals of the list
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Access method CDMA
• CDMA (Code Division Multiple Access)
– all terminals send on the same frequency probably at the same time and can
use the whole bandwidth of the transmission channel
– each sender has a unique random number, the sender XORs the signal with
this random number
– the receiver can “tune” into this signal if it knows the pseudo random number,
tuning is done via a correlation function
• Disadvantages:
– higher complexity of a receiver (receiver cannot just listen into the medium
and start receiving if there is a signal)
– all signals should have the same strength at a receiver
• Advantages:
–
–
–
–
all terminals can use the same frequency, no planning needed
huge code space (e.g. 232) compared to frequency space
interferences (e.g. white noise) is not coded
forward error correction and encryption can be easily integrated
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SDMA/TDMA/FDMA/CDMA
Approach
Idea
SDMA
segment space into
cells/sectors
Terminals
only one terminal can
be active in one
cell/one sector
Signal
separation
cell structure, directed
antennas
TDMA
segment sending
time into disjoint
time-slots, demand
driven or fixed
patterns
all terminals are
active for short
periods of time on
the same frequency
synchronization in
the time domain
FDMA
segment the
frequency band into
disjoint sub-bands
CDMA
spread the spectrum
using orthogonal codes
every terminal has its all terminals can be active
own frequency,
at the same place at the
uninterrupted
same moment,
uninterrupted
filtering in the
code plus special
frequency domain
receivers
Advantages very simple, increases established, fully
simple, established,
robust
inflexible, antennas
Disadvantages typically fixed
inflexible,
frequencies are a
scarce resource
flexible, less frequency
planning needed, soft
handover
complex receivers, needs
more complicated power
control for senders
typically combined
with TDMA
(frequency hopping
patterns) and SDMA
(frequency reuse)
still faces some problems,
higher complexity,
lowered expectations; will
be integrated with
TDMA/FDMA
capacity per km²
Comment
only in combination
with TDMA, FDMA or
CDMA useful
digital, flexible
guard space
needed (multipath
propagation),
synchronization
difficult
standard in fixed
networks, together
with FDMA/SDMA
used in many
mobile networks
GSM, DECT, TETRA, UMTS, LTE
Schiller Chapter 4: Wireless
Telecommunication Systems
How does it work?
• How can the system locate a user?
• Why don’t all phones ring at the same time?
• What happens if two users talk
simultaneously?
• Why don’t I get the bill from my neighbor?
• Why can an Australian use her phone in
Berlin?
• Why can’t I simply overhear the neighbor’s
communication?
• How secure is the mobile phone system?
• What are the key components of the mobile phone
network?
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GSM: Overview
• GSM
– Global System for Mobile Communication
• formerly: Groupe Spéciale Mobile (founded 1982)
– Pan-European standard (ETSI, European
Telecommunications Standardization Institute)
• GSM all over the world
– 219 countries in Asia, Africa, Europe, Australia, America
• USA: T-mobile, AT&T, Cinci Bell, …
– > 4.2 billion subscribers in >700 networks
– > 75% of all digital mobile phones
– www.gsmworld.com/newsroom/market-data/index.htm
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Performance characteristics of GSM
• Communication
– mobile, wireless communication; support for voice and data services
• Total mobility
– international access, chip-card enables use of access points of
different providers
• Worldwide connectivity
– one number, the network handles localization
• High capacity
– better frequency efficiency, smaller cells, more customers per cell
• High transmission quality
– high audio quality and reliability for wireless, uninterrupted phone
calls at higher speeds (e.g., from cars, trains)
• Security functions
– access control, authentication via chip-card and PIN
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Disadvantages of GSM
•
•
•
•
no end-to-end encryption of user data
roaming profiles accessible
high complexity of the system
several incompatibilities within the GSM
standards
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GSM: Mobile Services
• Bearer Services
• Telematic Services
• Supplementary Services
bearer services
MS
TE
MT
R, S
GSM-PLMN
Um
transit
network
(PSTN, ISDN)
source/
destination
network
TE
(U, S, R)
tele services
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Bearer Services
• Telecommunication services to transfer data between access points
• Specification of services up to the terminal interface (OSI layers 1-3)
• Different data rates for voice and data (original standard)
– data service (circuit switched)
• synchronous: 2.4, 4.8 or 9.6 kbit/s
• asynchronous: 300 - 1200 bit/s
– data service (packet switched)
• synchronous: 2.4, 4.8 or 9.6 kbit/s
• asynchronous: 300 - 9600 bit/s
• Today: data rates of approx. 50 kbit/s possible
– even more with new modulation
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Telecommunication Services I
• mobile telephony
offering the traditional bandwidth of 3.1 kHz
• Emergency number
common number throughout Europe (112);
mandatory for all service providers; free of
charge; connection with the highest priority
(preemption of other connections possible)
• Multinumbering
several ISDN phone numbers per user possible
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Tele Services II: Non-Voice-Teleservices
• group 3 fax
• voice mailbox (implemented in the fixed network supporting the
mobile terminals)
• electronic mail (MHS, Message Handling System, implemented in
the fixed network)
• ...
• Short Message Service (SMS)
alphanumeric data transmission to/from the mobile terminal (160
characters) using the signaling channel, thus allowing simultaneous
use of basic services and SMS
(almost ignored in the beginning now the most successful add-on!)
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Supplementary services
• Services in addition to the basic services, cannot be offered
stand-alone
• Similar to ISDN services besides lower bandwidth due to
the radio link
• May differ between different service providers, countries
and protocol versions
• Important services
–
–
–
–
–
–
identification: forwarding of caller number
suppression of number forwarding
automatic call-back
conferencing with up to 7 participants
locking of the mobile terminal (incoming or outgoing calls)
...
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Architecture of the GSM system
• GSM is a PLMN (Public Land Mobile Network)
– several providers setup mobile networks following the
GSM standard within each country
– components
•
•
•
•
MS (mobile station)
BS (base station)
MSC (mobile switching center)
LR (location register)
– subsystems
• RSS (radio subsystem): covers all radio aspects
• NSS (network and switching subsystem): call forwarding, handover,
switching
• OSS (operation subsystem): management of the network
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GSM: overview
OMC, EIR,
AUC
HLR
NSS
with OSS
VLR
MSC
GMSC
VLR
fixed network
MSC
BSC
BSC
RSS
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segmentation of the area into cells
• use of several carrier frequencies
• not the same frequency in adjoining cells
• cell sizes vary from some 100 m up to 35 km depending on user density,
geography, transceiver power etc.
• hexagonal shape of cells is idealized (cells overlap, shapes depend on
geography)
• if a mobile user changes cells handover of the connection to the neighbor
cell
possible radio coverage of the cell
cell
idealized shape of the cell
GSM: system architecture
radio
subsystem
MS
network and
switching subsystem
fixed
partner networks
MS
ISDN
PSTN
MSC
Um
BTS
Abis
BSC
EIR
SS7
BTS
VLR
BTS
BTS
BSS
HLR
BSC
A
MSC
IWF
ISDN
PSTN
PSPDN
CSPDN
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Radio subsystem
radio
subsystem
MS
network and switching
subsystem
– MS (Mobile Station)
– BSS (Base Station Subsystem):
consisting of
MS
Um
BTS
Abis
BTS
• Components
BSC
MSC
• BTS (Base Transceiver Station):
sender and receiver
• BSC (Base Station Controller):
controlling several transceivers
• Interfaces
A
BTS
BTS
BSC
MSC
– Um : radio interface
– Abis : standardized, open interface
with
16 kbit/s user channels
– A: standardized, open interface with
64 kbit/s user channels
BSS
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•
Network and switching subsystem
network
subsystem
fixed partner
networks
•Components
ISDN
PSTN
MSC
SS7
EIR
HLR
ISDN
PSTN
PSPDN
CSPDN
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MSC (Mobile Services Switching
Center):
IWF (Interworking Functions)
ISDN (Integrated Services
Digital Network)
PSTN (Public Switched
Telephone Network)
PSPDN (Packet Switched Public
Data Net.)
CSPDN (Circuit Switched Public
Data Net.)
•Databases
VLR
MSC
IWF
•
•
•
•
•
•
• HLR (Home Location Register)
• VLR (Visitor Location Register)
• EIR (Equipment Identity
Register)
27
GSM frequency bands (examples)
Type
Channels
Uplink [MHz]
Downlink
[MHz]
GSM 850
128-251
824-849
869-894
GSM 900
0-124, 9551023
876-915
921-960
890-915
880-915
935-960
925-960
classical
extended
124 channels
+49 channels
GSM 1800
512-885
1710-1785
1805-1880
GSM 1900
512-810
1850-1910
1930-1990
GSM-R
955-1024, 0124
876-915
921-960
876-880
921-925
exclusive
69 channels
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Mobile station
• Terminal for the use of GSM services
• A mobile station (MS) comprises several functional groups
– MT (Mobile Terminal):
• offers common functions used by all services the MS offers
• corresponds to the network termination (NT) of an ISDN access
• end-point of the radio interface (Um)
– TA (Terminal Adapter):
• terminal adaptation, hides radio specific characteristics
– TE (Terminal Equipment):
• peripheral device of the MS, offers services to a user
• does not contain GSM specific functions
– SIM (Subscriber Identity Module):
• personalization of the mobile terminal, stores user parameters
TE
TA
R
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MT
S
Um
29
Network and switching subsystem
• NSS is the main component of the public mobile network
GSM
– switching, mobility management, interconnection to other
networks, system control
• Components
– Mobile Services Switching Center (MSC)
controls all connections via a separated network to/from a
mobile terminal within the domain of the MSC - several BSC can
belong to a MSC
– Databases (important: scalability, high capacity, low delay)
• Home Location Register (HLR)
central master database containing user data, permanent and semipermanent data of all subscribers assigned to the HLR (one provider
can have several HLRs)
• Visitor Location Register (VLR)
local database for a subset of user data, including data about all user
currently in the domain of the VLR
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Mobile Services Switching Center
• The MSC (mobile services switching center) plays a central role in GSM
–
–
–
–
–
switching functions
additional functions for mobility support
management of network resources
interworking functions via Gateway MSC (GMSC)
integration of several databases
• Functions of a MSC
–
–
–
–
–
–
–
specific functions for paging and call forwarding
termination of SS7 (signaling system no. 7)
mobility specific signaling
location registration and forwarding of location information
provision of new services (fax, data calls)
support of short message service (SMS)
generation and forwarding of accounting and billing information
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Operation subsystem
• The OSS (Operation Subsystem) enables centralized
operation, management, and maintenance of all GSM
subsystems
• Components
– Authentication Center (AUC)
• generates user specific authentication parameters on request of a VLR
• authentication parameters used for authentication of mobile
terminals and encryption of user data on the air interface within the
GSM system
– Equipment Identity Register (EIR)
• registers GSM mobile stations and user rights
• stolen or malfunctioning mobile stations can be locked and sometimes
even localized
– Operation and Maintenance Center (OMC)
• different control capabilities for the radio subsystem and the network
subsystem
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GSM - TDMA/FDMA
935-960 MHz
124 channels (200 kHz)
downlink
890-915 MHz
124 channels (200 kHz)
uplink
higher GSM frame structures
time
GSM TDMA frame
1
2
3
4
5
6
7
8
4.615 ms
GSM time-slot (normal burst)
guard
space
tail
3 bits
user data
S Training S
user data
57 bits
1 26 bits 1
57 bits
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guard
tail space
3
546.5 µs
577 µs
33
GSM hierarchy of frames
hyperframe
0
1
2
2045 2046 2047 3 h 28 min 53.76 s
...
superframe
0
1
0
2
1
...
48
...
49
50
24
6.12 s
25
multiframe
0
1
...
0
24
1
2
120 ms
25
...
48
49
50
235.4 ms
frame
0
1
...
6
7
4.615 ms
slot
burst
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577 µs
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GSM protocol layers for signaling
Um
Abis
MS
A
BTS
BSC
MSC
CM
CM
MM
MM
RR
RR’
BTSM
RR’
BTSM
LAPDm
LAPDm
LAPD
LAPD
radio
radio
PCM
PCM
16/64 kbit/s
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BSSAP
BSSAP
SS7
SS7
PCM
PCM
64 kbit/s /
2.048 Mbit/s
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Mobile Terminated Call
1: calling a GSM subscriber
2: forwarding call to GMSC
3: signal call setup to HLR
4, 5: request MSRN from VLR
6: forward responsible
calling
MSC to GMSC
station 1
7: forward call to
current MSC
8, 9: get current status of MS
10, 11: paging of MS
12, 13: MS answers
14, 15: security checks
16, 17: set up connection
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HLR
4
5
3 6
PSTN
2
GMSC
10
7
VLR
8 9
14 15
MSC
10 13
16
10
BSS
BSS
BSS
11
11
11
11 12
17
MS
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Mobile Originated Call
1, 2: connection request
3, 4: security check
5-8: check resources (free
circuit)
9-10: set up call
VLR
3 4
6
PSTN
5
GMSC
7
MSC
8
2 9
MS
1
10
BSS
Mobile Terminated/Originated Call
MS
MTC
BTS
MS
MOC
BTS
paging request
channel request
channel request
immediate assignment
immediate assignment
paging response
service request
authentication request
authentication request
authentication response
authentication response
ciphering command
ciphering command
ciphering complete
ciphering complete
setup
setup
call confirmed
call confirmed
assignment command
assignment command
assignment complete
assignment complete
alerting
alerting
connect
connect
connect acknowledge
connect acknowledge
data/speech exchange
data/speech exchange
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4 types of handover
1
2
3
4
MS
MS
MS
MS
BTS
BTS
BTS
BTS
BSC
BSC
BSC
MSC
MSC
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Handover decision
receive level
BTSold
receive level
BTSold
HO_MARGIN
MS
MS
BTSold
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BTSnew
40
Handover procedure
MS
BTSold
BSCold
measurement
measurement
report
result
MSC
HO decision
HO required
BSCnew
BTSnew
HO request
resource allocation
ch. activation
HO command
HO command
HO command
HO request ack ch. activation ack
HO access
Link establishment
clear command clear command
clear complete
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HO complete
HO complete
clear complete
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DECT
• DECT (Digital European Cordless Telephone) standardized by ETSI (ETS
300.175-x) for cordless telephones
• standard describes air interface between base-station and mobile phone
• DECT has been renamed for international marketing reasons into „Digital
Enhanced Cordless Telecommunication“
• Characteristics
–
–
–
–
frequency: 1880-1990 MHz
channels: 120 full duplex
duplex mechanism: TDD (Time Division Duplex) with 10 ms frame length
multplexing scheme: FDMA with 10 carrier frequencies,
TDMA with 2x 12 slots
– modulation: digital, Gaußian Minimum Shift Key (GMSK)
– power: 10 mW average (max. 250 mW)
– range: approx. 50 m in buildings, 300 m open space
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DECT system architecture reference
model
D4
D3
VDB
D2
PA
PA
PT
FT
local
network
PT
HDB
D1
global
network
FT
local
network
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DECT reference model
C-Plane
U-Plane
network
layer
data link
control
application
processes
management
signaling,
interworking
OSI layer 3
data link
control
OSI layer 2
medium access control
physical layer
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• close to the OSI
reference model
• management
plane over all
layers
• several services in
C(ontrol)- and
U(ser)-plane
OSI layer 1
44
DECT layers I
• Physical layer
– modulation/demodulation
– generation of the physical channel structure with a guaranteed
throughput
– controlling of radio transmission
•
•
•
•
channel assignment on request of the MAC layer
detection of incoming signals
sender/receiver synchronization
collecting status information for the management plane
• MAC layer
– maintaining basic services, activating/deactivating physical channels
– multiplexing of logical channels
• e.g., C: signaling, I: user data, P: paging, Q: broadcast
– segmentation/reassembly
– error control/error correction
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DECT layers II
• Data link control layer
– creation and keeping up reliable connections between the
mobile terminal and basestation
– two DLC protocols for the control plane (C-Plane)
• connectionless broadcast service:
paging functionality
• Lc+LAPC protocol:
in-call signaling (similar to LAPD within ISDN), adapted to the
underlying MAC service
– several services specified for the user plane (U-Plane)
•
•
•
•
null-service: offers unmodified MAC services
frame relay: simple packet transmission
frame switching: time-bounded packet transmission
error correcting transmission: uses FEC, for delay critical, timebounded services
• bandwidth adaptive transmission
• “Escape” service: for further enhancements of the standard
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DECT layers III
• Network layer
– similar to ISDN (Q.931) and GSM (04.08)
– offers services to request, check, reserve, control, and
release resources at the basestation and mobile terminal
– resources
• necessary for a wireless connection
• necessary for the connection of the DECT system to the fixed
network
– main tasks
• call control: setup, release, negotiation, control
• call independent services: call forwarding, accounting, call
redirecting
• mobility management: identity management, authentication,
management of the location register
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Enhancements of the standard
• Several „DECT Application Profiles“ in addition to the DECT specification
– GAP (Generic Access Profile) standardized by ETSI in 1997
• assures interoperability between DECT equipment of different manufacturers
(minimal requirements for voice communication)
• enhanced management capabilities through the fixed network: Cordless Terminal
Mobility (CTM)
DECT
DECT
DECT
basestation
Common
Portable Part
Air Interface
fixed network
GAP
–
–
–
–
DECT/GSM Interworking Profile (GIP): connection to GSM
ISDN Interworking Profiles (IAP, IIP): connection to ISDN
Radio Local Loop Access Profile (RAP): public telephone service
CTM Access Profile (CAP): support for user mobility
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UMTS and IMT-2000
• Proposals for IMT-2000 (International Mobile Telecommunications)
– UWC-136, cdma2000, WP-CDMA
– UMTS (Universal Mobile Telecommunications System) from ETSI
• UMTS
– UTRA (was: UMTS, now: Universal Terrestrial Radio Access)
– enhancements of GSM
• EDGE (Enhanced Data rates for GSM Evolution): GSM up to 384 kbit/s
• CAMEL (Customized Application for Mobile Enhanced Logic)
• VHE (virtual Home Environment)
– fits into GMM (Global Multimedia Mobility) initiative from ETSI
– requirements
• min. 144 kbit/s rural (goal: 384 kbit/s)
• min. 384 kbit/s suburban (goal: 512 kbit/s)
• up to 2 Mbit/s urban
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IMT-2000 family
Interface
for Internetworking
IMT-2000
Core Network
ITU-T
GSM
(MAP)
Initial UMTS
(R99 w/ FDD)
IMT-2000
Radio Access
ITU-R
ANSI-41
(IS-634)
IP-Network
Flexible assignment of
Core Network and Radio Access
IMT-DS
IMT-TC
IMT-MC
IMT-SC
IMT-FT
(Direct Spread)
(Time Code)
(Multi Carrier)
(Single Carrier)
(Freq. Time)
UTRA FDD
(W-CDMA)
3GPP
UTRA TDD
(TD-CDMA);
TD-SCDMA
3GPP
cdma2000
UWC-136
(EDGE)
UWCC/3GPP
DECT
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3GPP2
ETSI
50
UMTS protocol stacks (user plane)
UE
Uu
UTRAN
IuCS 3G
MSC
apps. &
protocols
Circuit RLC
switched MAC
RLC
MAC
AAL2
AAL2
radio
radio
ATM
ATM
UE
Uu
apps. &
protocols
IP, PPP,
…
PDCP
Packet
switched RLC
SAR
UTRAN
IuPS
SAR
3G
SGSN
Gn
IP tunnel
3G
GGSN
IP, PPP,
…
GTP
RLC
GTP
UDP/IP
GTP
UDP/IP UDP/IP
MAC
MAC
AAL5
AAL5
L2
L2
radio
radio
ATM
ATM
L1
L1
CEG436: Mobile Computing (PM)
PDCP
GTP
UDP/IP
51
Support of mobility: macro diversity
• Multicasting of data via
several physical channels
– Enables soft handover
– FDD mode only
UE
Node B
• Uplink
Node B
RNC
CN
– simultaneous reception of
UE data at several Node Bs
– Reconstruction of data at
Node B, SRNC or DRNC
• Downlink
– Simultaneous transmission
of data via different cells
– Different spreading codes in
different cells
CEG436: Mobile Computing (PM)
52
Support of mobility: handover
• From and to other systems (e.g., UMTS to GSM)
– This is a must as UMTS coverage will be poor in the beginning
• RNS controlling the connection is called SRNS (Serving RNS)
• RNS offering additional resources (e.g., for soft handover) is called Drift
RNS (DRNS)
• End-to-end connections between UE and CN only via Iu at the SRNS
– Change of SRNS requires change of Iu
– Initiated by the SRNS
– Controlled by the RNC and CN
Node B
Iub
UE
CN
SRNC
Node B
Iur
Iu
DRNC
Iub
CEG436: Mobile Computing (PM)
53
Example handover types in
UMTS/GSM
UE1
Node B1
UE2
UE3
UE4
RNC1
Iu
Node B2
Iur
Iub
Node B3
RNC2
3G MSC2
BTS
BSC
2G MSC3
Abis
CEG436: Mobile Computing (PM)
3G MSC1
A
54
Breathing Cells
• GSM
– Mobile device gets exclusive signal from the base station
– Number of devices in a cell does not influence cell size
• UMTS
– Cell size is closely correlated to the cell capacity
– Signal-to-nose ratio determines cell capacity
– Noise is generated by interference from
• other cells
• other users of the same cell
– Interference increases noise level
– Devices at the edge of a cell cannot further increase their output power (max.
power limit) and thus drop out of the cell
 no more communication possible
– Limitation of the max. number of users within a cell required
– Cell breathing complicates network planning
CEG436: Mobile Computing (PM)
55
Breathing Cells: Example
CEG436: Mobile Computing (PM)
56
Long Term Evolution (LTE)
• Initiated in 2004 by NTT DoCoMo,
focus on enhancing the Universal
Terrestrial Radio Access (UTRA) and
optimizing 3GPP’s radio access architecture
• Targets: Downlink 100 Mbit/s, uplink 50 Mbit/s, RTT<10ms
• 2007: E UTRA progressed from the feasibility study stage to
the first issue of approved Technical Specifications
• 2008: stable for commercial implementation
• 2009: first public LTE service available (Stockholm and Oslo)
• 2010: LTE starts in Germany
• LTE is not 4G – sometimes called 3.9G
– Does not fulfill all requirements for IMT advanced
CEG436: Mobile Computing (PM)
57
Key LTE features
• Simplified network architecture compared to GSM/UMTS
– Flat IP-based network replacing the GPRS core, optimized for the IPMultimedia Subsystem (IMS), no more circuit switching
• Network should be in parts self-organizing
• Scheme for soft frequency reuse between cells
– Inner part uses all subbands with less power
– Outer part uses pre-served subbands with higher power
•
•
•
•
Much higher data throughput supported by multiple antennas
Much higher flexibility in terms of spectrum, bandwidth, data rates
Much lower RTT – good for interactive traffic and gaming
Smooth transition from W-CDMA/HSPA, TD-SCDMA and cdma2000 1x EVDO – but completely different radio!
• Large step towards 4G – IMT advanced
• See www.3gpp.org for all specs, tables, figures etc.!
CEG436: Mobile Computing (PM)
58
High flexibility
•
E-UTRA
Operating
Band
E-UTRA (Evolved Universal Terrestrial Radio Access)
– Operating bands
700-2700MHz
– Channel bandwidth 1.4,
3, 5, 10, 15, or 20 MHz
– TDD and FDD
•
Modulation
– QPSK, 16QAM, 64QAM
•
Multiple Access
– OFDMA (DL),
SC-FDMA (UL)
•
Peak data rates
– 300 Mbit/s DL
– 75 Mbit/s UL
– Depends on UE
category
•
Uplink (UL) operating band
BS receive
UE transmit
FUL_low – FUL_high
1920 MHz – 1980 MHz
1850 MHz – 1910 MHz
1710 MHz – 1785 MHz
1710 MHz – 1755 MHz
824 MHz – 849 MHz
830 MHz – 840 MHz
2500 MHz – 2570 MHz
880 MHz – 915 MHz
1749.9 MHz – 1784.9 MHz
1710 MHz – 1770 MHz
1427.9 MHz – 1447.9 MHz
699 MHz – 716 MHz
777 MHz – 787 MHz
788 MHz – 798 MHz
Reserved
Reserved
704 MHz – 716 MHz
815 MHz – 830 MHz
830 MHz – 845 MHz
832 MHz – 862 MHz
1447.9 MHz – 1462.9 MHz
Cell radius
– From <1km to 100km
CEG436: Mobile Computing (PM)
1
2
3
4
5
1
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
...
33
1900 MHz –
34
2010 MHz –
35
1850 MHz –
36
1930 MHz –
37
1910 MHz –
38
2570 MHz –
39
1880 MHz –
40
2300 MHz –
Note 1: Band 6 is not applicable
1920 MHz
2025 MHz
1910 MHz
1990 MHz
1930 MHz
2620 MHz
1920 MHz
2400 MHz
Downlink (DL) operating band
BS transmit
UE receive
FDL_low – FDL_high
2110 MHz – 2170 MHz
1930 MHz – 1990 MHz
1805 MHz – 1880 MHz
2110 MHz – 2155 MHz
869 MHz – 894MHz
875 MHz – 885 MHz
2620 MHz – 2690 MHz
925 MHz – 960 MHz
1844.9 MHz – 1879.9 MHz
2110 MHz – 2170 MHz
1475.9 MHz – 1495.9 MHz
729 MHz – 746 MHz
746 MHz – 756 MHz
758 MHz – 768 MHz
Reserved
Reserved
734 MHz – 746 MHz
860 MHz – 875 MHz
875 MHz – 890 MHz
791 MHz – 821 MHz
1495.9 MHz – 1510.9 MHz
1900 MHz
2010 MHz
1850 MHz
1930 MHz
1910 MHz
2570 MHz
1880 MHz
2300 MHz
–
–
–
–
–
–
–
–
Duplex
Mode
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
FDD
1920 MHz
2025 MHz
1910 MHz
1990 MHz
1930 MHz
2620 MHz
1920 MHz
2400 MHz
TDD
TDD
TDD
TDD
TDD
TDD
TDD
TDD
59
LTE frame structure
Radio frame (10 ms)
UL
0
1
2
FDD
...
7
8
9
7
8
9
Subframe (1 ms)
DL
0
1
2
...
Synchronization is part of subframe 0 and 5
0
TDD
1
2
...
7
8
9
...
UL/DL
Downlink Pilot Time Slot
(data plus pilot signal)
Uplink Pilot Time Slot
(random access plus pilot signal)
Guard Period
CEG436: Mobile Computing (PM)
60
LTE architecture
Mobility Management Entity
Serving Gateway
Packet-data network Gateway
Home Subscriber Server
Policy and Charging Rules Function
Uu
UE2
MME
eNode B
eNode B
X2-U/-C
X2-U/-C
UE1
Uu
GPRS
S10
S3
MME
S1-MME
HSS
S6
S1-MME
S11
eNode B
X2-U/-C
S4
PCRF
S1-U
eNode B
X2-U/-C
S1-U
eNode B
E-UTRAN
CEG436: Mobile Computing (PM)
S7
S-GW
S5 S8 (roaming)
P-GW
Rx+
Internet,
Operators…
SGi
EPC (Evolved Packet Core)
61
LTE advanced
• GSM – UMTS - LTE
– LTE advanced as candidate for IMT-advanced
•
•
•
•
Worldwide functionality & roaming
Compatibility of services
Interworking with other radio access systems
Enhanced peak data rates to support advanced services and
applications (100 Mbit/s for high and 1 Gbit/s for low mobility)
• 3GPP will be contributing to the ITU-R towards the development of
IMT-Advanced via its proposal for LTE-Advanced.
• Relay Nodes to increase coverage
• 100 MHz bandwidth (5x LTE with 20 MHz)
CEG436: Mobile Computing (PM)
62
Wireless IEEE 802.11
Schiller Chapter 7: Wireless LANs
Characteristics of wireless LANs
• Advantages
–
–
–
–
very flexible within the reception area
Ad-hoc networks without previous planning possible
(almost) no wiring difficulties (e.g. historic buildings, firewalls)
more robust against disasters like, e.g., earthquakes, fire - or
users pulling a plug...
• Disadvantages
– typically very low bandwidth compared to wired networks
(1-10 Mbit/s) due to shared medium
– many proprietary solutions, especially for higher bit-rates,
standards take their time (e.g. IEEE 802.11n)
– products have to follow many national restrictions if working
wireless, it takes a vary long time to establish global solutions
like, e.g., IMT-2000
CEG436: Mobile Computing (PM)
64
Design goals for wireless LANs
•
•
•
•
•
•
•
•
global, seamless operation
low power for battery use
no special permissions or licenses needed to use the LAN
robust transmission technology
simplified spontaneous cooperation at meetings
easy to use for everyone, simple management
protection of investment in wired networks
security (no one should be able to read my data), privacy (no one
should be able to collect user profiles), safety (low radiation)
• transparency concerning applications and higher layer protocols,
but also location awareness if necessary
• …
CEG436: Mobile Computing (PM)
65
Comparison: infrared vs. radio
transmission
•
Infrared
– uses IR diodes, diffuse light, multiple
reflections (walls, furniture etc.)
•
Advantages
– simple, cheap, available in many
mobile devices
– no licenses needed
– simple shielding possible
•
Disadvantages
– interference by sunlight, heat sources
etc.
– many things shield or absorb IR light
– low bandwidth
•
Example
– IrDA (Infrared Data Association)
interface available everywhere
CEG436: Mobile Computing (PM)
• Radio
– typically using the license free
ISM band at 2.4 GHz
• Advantages
– experience from wireless WAN
and mobile phones can be used
– coverage of larger areas possible
(radio can penetrate walls,
furniture etc.)
• Disadvantages
– very limited license free
frequency bands
– shielding more difficult,
interference with other electrical
devices
• Example
– Many different products
66
Comparison: infrastructure vs. ad-hoc
networks
infrastructure
network
AP
AP
wired network
AP: Access Point
AP
ad-hoc network
CEG436: Mobile Computing (PM)
67
802.11 - Architecture of an
infrastructure network
•
802.11 LAN
STA1
– terminal with access mechanisms to the
wireless medium and radio contact to
the access point
802.x LAN
•
Portal
•
ESS
•
Portal
– bridge to other (wired) networks
•
Distribution System
– interconnection network to form one
logical network (EES: Extended Service
Set) based
on several BSS
BSS2
STA2
Access Point
– station integrated into the wireless LAN
and the distribution system
Distribution System
Access
Point
Basic Service Set (BSS)
– group of stations using the same radio
frequency
BSS1
Access
Point
Station (STA)
802.11 LAN
STA3
802.11 - Architecture of an
ad-hoc network
• Direct communication within a
limited range
802.11 LAN
– Station (STA):
terminal with access mechanisms to
the wireless medium
– Independent Basic Service Set
(IBSS):
group of stations using the same
radio frequency
STA1
STA3
IBSS1
STA2
IBSS2
STA5
STA4
802.11 LAN
IEEE standard 802.11
fixed
terminal
mobile terminal
infrastructure
network
access point
application
application
TCP
TCP
IP
IP
LLC
LLC
LLC
802.11 MAC
802.11 MAC 802.3 MAC
802.3 MAC
802.11 PHY
802.11 PHY
802.3 PHY
CEG436: Mobile Computing (PM)
802.3 PHY
70
•
802.11
Layers
and
functions
• PLCP
MAC
Physical Layer Convergence Protocol
– access mechanisms, fragmentation,
encryption
• MAC Management
– synchronization, roaming, MIB,
power management
– clear channel assessment signal
(carrier sense)
• PMD Physical Medium Dependent
– modulation, coding
• PHY Management
– channel selection, MIB
• Station Management
LLC
MAC
MAC Management
PLCP
PHY Management
PMD
CEG436: Mobile Computing (PM)
Station Management
PHY
DLC
– coordination of all management
functions
71
802.11 - Physical layer (legacy)
•
3 versions: 2 radio (typ. 2.4 GHz), 1 IR
– data rates 1 or 2 Mbit/s
•
FHSS (Frequency Hopping Spread Spectrum)
– spreading, despreading, signal strength, typ. 1 Mbit/s
– min. 2.5 frequency hops/s (USA), two-level GFSK modulation
•
DSSS (Direct Sequence Spread Spectrum)
– DBPSK modulation for 1 Mbit/s (Differential Binary Phase Shift Keying), DQPSK for 2
Mbit/s (Differential Quadrature PSK)
– preamble and header of a frame is always transmitted with 1 Mbit/s, rest of
transmission 1 or 2 Mbit/s
– chipping sequence: +1, -1, +1, +1, -1, +1, +1, +1, -1, -1, -1 (Barker code)
– max. radiated power 1 W (USA), 100 mW (EU), min. 1mW
•
Infrared
– 850-950 nm, diffuse light, typ. 10 m range
– carrier detection, energy detection, synchronization
CEG436: Mobile Computing (PM)
72
FHSS PHY packet format (legacy)
• Synchronization
– synch with 010101... pattern
• SFD (Start Frame Delimiter)
– 0000110010111101 start pattern
• PLW (PLCP_PDU Length Word)
– length of payload incl. 32 bit CRC of payload, PLW < 4096
• PSF (PLCP Signaling Field)
– data of payload (1 or 2 Mbit/s)
80
16
12
• HEC (Header
Error
Check)
synchronization
SFD PLW
16
– CRC with x +x12+x5+1
PLCP preamble
CEG436: Mobile Computing (PM)
4
16
PSF
HEC
variable
bits
payload
PLCP header
73
802.11 - MAC layer I - DFWMAC
• Traffic services
– Asynchronous Data Service (mandatory)
• exchange of data packets based on “best-effort”
• support of broadcast and multicast
– Time-Bounded Service (optional)
• implemented using PCF (Point Coordination Function)
• Access methods
– DFWMAC-DCF CSMA/CA (mandatory)
• collision avoidance via randomized „back-off“ mechanism
• minimum distance between consecutive packets
• ACK packet for acknowledgements (not for broadcasts)
– DFWMAC-DCF w/ RTS/CTS (optional)
• Distributed Foundation Wireless MAC
• avoids hidden terminal problem
– DFWMAC- PCF (optional)
• access point polls terminals according to a list
CEG436: Mobile Computing (PM)
74
• Priorities
802.11 - MAC layer II
– defined through different inter frame spaces
– no guaranteed, hard priorities
– SIFS (Short Inter Frame Spacing)
• highest priority, for ACK, CTS, polling response
– PIFS (PCF IFS)
• medium priority, for time-bounded service using PCF
– DIFS (DCF, Distributed Coordination Function IFS)
• lowest priority, for asynchronous data service
DIFS
DIFS
medium busy
PIFS
SIFS
direct access if
medium is free  DIFS
CEG436: Mobile Computing (PM)
contention
next frame
t
75
802.11 - CSMA/CA access method I
• station ready to send starts sensing the medium (Carrier
Sense based on CCA, Clear Channel Assessment)
• if the medium is free for the duration of an Inter-Frame
Space (IFS), the station can start sending (IFS depends on
service type)
• if the medium is busy, the station has to wait for a free IFS,
then the station must additionally wait a random back-off
time (collision avoidance, multiple of slot-time)
• if another station occupies the medium during the back-off
contention window
timeDIFS
of the station, the back-off
DIFS timer stops (fairness)
(randomized back-off
mechanism)
medium busy
direct access if
medium is free  DIFS
CEG436: Mobile Computing (PM)
next frame
t
slot time (20µs)
76
Special Frames: ACK, RTS, CTS
bytes
ACK
• Acknowledgement
2
Frame
Control
bytes
RTS
• Request To Send
2
Frame
Control
bytes
CTS
2
Frame
Control
2
6
4
Receiver
Duration
CRC
Address
2
6
6
4
Receiver Transmitter
Duration
CRC
Address Address
2
6
4
Receiver
Duration
CRC
Address
• Clear To Send
CEG436: Mobile Computing (PM)
77
802.11 - MAC management
• Synchronization
– try to find a LAN, try to stay within a LAN
– timer etc.
• Power management
– sleep-mode without missing a message
– periodic sleep, frame buffering, traffic measurements
• Association/Reassociation
– integration into a LAN
– roaming, i.e. change networks by changing access points
– scanning, i.e. active search for a network
• MIB - Management Information Base
– managing, read, write
CEG436: Mobile Computing (PM)
78
Synchronization using a Beacon
(infrastructure)
beacon interval
(20ms – 1s)
access
point
medium
B
B
busy
busy
B
busy
B
busy
t
value of the timestamp
CEG436: Mobile Computing (PM)
B beacon frame
79
Synchronization using a Beacon (adhoc)
beacon interval
station1
B1
B1
B2
station2
medium
busy
busy
B2
busy
busy
t
value of the timestamp
CEG436: Mobile Computing (PM)
B beacon frame
random delay
80
Power management
•
•
•
Idea: switch the transceiver off if not needed
States of a station: sleep and awake
Timing Synchronization Function (TSF)
– stations wake up at the same time
•
Infrastructure
– Traffic Indication Map (TIM)
• list of unicast receivers transmitted by AP
– Delivery Traffic Indication Map (DTIM)
• list of broadcast/multicast receivers transmitted by AP
•
Ad-hoc
– Ad-hoc Traffic Indication Map (ATIM)
• announcement of receivers by stations buffering frames
• more complicated - no central AP
• collision of ATIMs possible (scalability?)
•
APSD (Automatic Power Save Delivery)
– new method in 802.11e replacing above schemes
CEG436: Mobile Computing (PM)
81
Power saving with wake-up patterns
(infrastructure)
TIM interval
access
point
DTIM interval
D B
T
busy
medium
busy
T
d
D B
busy
busy
p
station
d
t
T TIM
D DTIM
B broadcast/multicast
CEG436: Mobile Computing (PM)
awake
p PS poll
d data transmission
to/from the station
82
Power saving with wake-up patterns
(ad-hoc)
ATIM
window
station1
beacon interval
B1
station2
A
B2
B2
D
a
B1
d
t
B beacon frame
awake
CEG436: Mobile Computing (PM)
random delay
a acknowledge ATIM
A transmit ATIM
D transmit data
d acknowledge data
83
802.11 - Roaming
• No or bad connection? Then perform:
• Scanning
– scan the environment, i.e., listen into the medium for beacon signals or send
probes into the medium and wait for an answer
• Reassociation Request
– station sends a request to one or several AP(s)
• Reassociation Response
– success: AP has answered, station can now participate
– failure: continue scanning
• AP accepts Reassociation Request
– signal the new station to the distribution system
– the distribution system updates its data base (i.e., location information)
– typically, the distribution system now informs the old AP so it can release
resources
• Fast roaming – 802.11r
– e.g. for vehicle-to-roadside networks
CEG436: Mobile Computing (PM)
84
• Data rate
WLAN: IEEE• 802.11b
Connection set-up time
– 1, 2, 5.5, 11 Mbit/s, depending on
SNR
– User data rate max. approx. 6
Mbit/s
• Transmission range
– 300m outdoor, 30m indoor
– Max. data rate ~10m indoor
• Frequency
– DSSS, 2.4 GHz ISM-band
• Security
– Limited, WEP insecure, SSID
• Availability
– Connectionless/always on
•
Quality of Service
– Typ. Best effort, no guarantees (unless
polling is used, limited support in
products)
•
Manageability
– Limited (no automated key distribution,
sym. Encryption)
•
Special Advantages/Disadvantages
– Advantage: many installed systems, lot
of experience, available worldwide, free
ISM-band, many vendors, integrated in
laptops, simple system
– Disadvantage: heavy interference on
ISM-band, no service guarantees, slow
relative speed only
– Many products, many vendors
CEG436: Mobile Computing (PM)
85
IEEE 802.11b – PHY frame formats
Long PLCP PPDU format
128
16
synchronization
SFD
8
8
16
16
signal service length HEC
PLCP preamble
bits
variable
payload
PLCP header
192 µs at 1 Mbit/s DBPSK
1, 2, 5.5 or 11 Mbit/s
Short PLCP PPDU format (optional)
56
short synch.
16
SFD
8
16
16
signal service length HEC
PLCP preamble
(1 Mbit/s, DBPSK)
variable
bits
payload
PLCP header
(2 Mbit/s, DQPSK)
96 µs
CEG436: Mobile Computing (PM)
8
2, 5.5 or 11 Mbit/s
86
Channel selection (non-overlapping)
Europe (ETSI)
channel 1
2400
2412
channel 7
channel 13
2442
2472
22 MHz
2483.5
[MHz]
US (FCC)/Canada (IC)
channel 1
2400
2412
channel 6
channel 11
2437
2462
22 MHz
CEG436: Mobile Computing (PM)
2483.5
[MHz]
87
•
Data rate
WLAN: IEEE• 802.11a
Connection set-up time
– 6, 9, 12, 18, 24, 36, 48, 54 Mbit/s,
depending on SNR
– User throughput (1500 byte packets):
5.3 (6), 18 (24), 24 (36), 32 (54)
– 6, 12, 24 Mbit/s mandatory
•
Transmission range
– Connectionless/always on
•
– Typ. best effort, no guarantees (same as
all 802.11 products)
•
•
Frequency
– Free 5.15-5.25, 5.25-5.35, 5.725-5.825
GHz ISM-band
•
Security
– Limited, WEP insecure, SSID
•
Manageability
– Limited (no automated key distribution,
sym. Encryption)
– 100m outdoor, 10m indoor
• E.g., 54 Mbit/s up to 5 m, 48 up to 12 m,
36 up to 25 m, 24 up to 30m, 18 up to 40
m, 12 up to 60 m
Quality of Service
•
Special Advantages/Disadvantages
– Advantage: fits into 802.x standards, free
ISM-band, available, simple system, uses
less crowded 5 GHz band
– Disadvantage: stronger shading due to
higher frequency, no QoS
Availability
– Some products, some vendors
CEG436: Mobile Computing (PM)
88
IEEE 802.11a – PHY frame format
4
rate
1
12
1
6
reserved length parity tail
16
variable
service payload
6
tail
variable
bits
pad
PLCP header
PLCP preamble
signal
12
data
1
6 Mbit/s
CEG436: Mobile Computing (PM)
variable
symbols
6, 9, 12, 18, 24, 36, 48, 54 Mbit/s
89
Operating channels of 802.11a in
Europe
36
5150
40
44
48
52
56
60
64
channel
5180 5200 5220 5240 5260 5280 5300 5320
5350 [MHz]
16.6 MHz
100
5470
104
140
channel
5500 5520 5540 5560 5580 5600 5620 5640 5660 5680 5700
5725
[MHz]
16.6 MHz
CEG436: Mobile Computing (PM)
108
112
116
120
124
128
132
136
center frequency =
5000 + 5*channel number [MHz]
90
Operating channels for 802.11a / US
U-NII
36
5150
40
44
48
52
56
60
64
5180 5200 5220 5240 5260 5280 5300 5320
channel
5350 [MHz]
16.6 MHz
149
153
157
161
channel
center frequency =
5000 + 5*channel number [MHz]
5725 5745 5765 5785 5805 5825 [MHz]
16.6 MHz
CEG436: Mobile Computing (PM)
91
WLAN: IEEE 802.11 – current
developments (06/2009)
•
•
•
802.11c: Bridge Support
–
802.11d: Regulatory Domain Update
–
•
•
•
Support of additional regulations related to channel selection, hopping sequences
802.11e: MAC Enhancements – QoS
–
–
•
Definition of MAC procedures to support bridges as extension to 802.1D
–
–
Enhance the current 802.11 MAC to expand support for applications with Quality of Service
requirements, and in the capabilities and efficiency of the protocol
Definition of a data flow (“connection”) with parameters like rate, burst, period… supported by HCCA
(HCF (Hybrid Coordinator Function) Controlled Channel Access, optional)
Additional energy saving mechanisms and more efficient retransmission
EDCA (Enhanced Distributed Channel Access): high priority traffic waits less for channel access
802.11F: Inter-Access Point Protocol (withdrawn)
–
Establish an Inter-Access Point Protocol for data exchange via the distribution system
802.11g: Data Rates > 20 Mbit/s at 2.4 GHz; 54 Mbit/s, OFDM
–
Successful successor of 802.11b, performance loss during mixed operation with .11b
802.11h: Spectrum Managed 802.11a
–
Extension for operation of 802.11a in Europe by mechanisms like channel measurement for dynamic
channel selection (DFS, Dynamic Frequency Selection) and power control (TPC, Transmit Power
Control)
802.11i: Enhanced Security Mechanisms
–
–
–
Enhance the current 802.11 MAC to provide improvements in security.
TKIP enhances the insecure WEP, but remains compatible to older WEP systems
AES provides a secure encryption method and is based on new hardware
CEG436: Mobile Computing (PM)
92
WLAN: IEEE 802.11– current
developments (06/2009)
•
•
•
•
•
•
•
802.11j: Extensions for operations in Japan
–
Changes of 802.11a for operation at 5GHz in Japan using only half the channel width at larger range
802.11-2007: Current “complete” standard
–
Comprises amendments a, b, d, e, g, h, i, j
802.11k: Methods for channel measurements
–
Devices and access points should be able to estimate channel quality in order to be able to choose a
better access point of channel
802.11m: Updates of the 802.11-2007 standard
802.11n: Higher data rates above 100Mbit/s
–
–
–
Changes of PHY and MAC with the goal of 100Mbit/s at MAC SAP
MIMO antennas (Multiple Input Multiple Output), up to 600Mbit/s are currently feasible
However, still a large overhead due to protocol headers and inefficient mechanisms
802.11p: Inter car communications
–
–
–
Communication between cars/road side and cars/cars
Planned for relative speeds of min. 200km/h and ranges over 1000m
Usage of 5.850-5.925GHz band in North America
802.11r: Faster Handover between BSS
–
–
–
Secure, fast handover of a station from one AP to another within an ESS
Current mechanisms (even newer standards like 802.11i) plus incompatible devices from different
vendors are massive problems for the use of, e.g., VoIP in WLANs
Handover should be feasible within 50ms in order to support multimedia applications efficiently
CEG436: Mobile Computing (PM)
93
WLAN: IEEE 802.11– current
developments (06/2009)
•
802.11s: Mesh Networking
•
802.11T: Performance evaluation of 802.11 networks
•
•
802.11u: Interworking with additional external networks
802.11v: Network management
•
802.11w: Securing of network control
•
•
•
•
•
802.11y: Extensions for the 3650-3700 MHz band in the USA
802.11z: Extension to direct link setup
802.11aa: Robust audio/video stream transport
802.11ac: Very High Throughput <6Ghz
802.11ad: Very High Throughput in 60 GHz
•
Note: Not all “standards” will end in products, many ideas get stuck at working group
level
Info: www.ieee802.org/11/, 802wirelessworld.com, standards.ieee.org/getieee802/
•
– Design of a self-configuring Wireless Distribution System (WDS) based on 802.11
– Support of point-to-point and broadcast communication across several hops
– Standardization of performance measurement schemes
– Extensions of current management functions, channel measurements
– Definition of a unified interface
– Classical standards like 802.11, but also 802.11i protect only data frames, not the control
frames. Thus, this standard should extend 802.11i in a way that, e.g., no control frames can be
forged.
CEG436: Mobile Computing (PM)
94
Bluetooth
• Basic idea
– Universal radio interface for ad-hoc wireless
connectivity
– Interconnecting computer and peripherals, handheld
devices, PDAs, cell phones – replacement of IrDA
– Embedded in other devices, goal: 5€/device (already <
1€)
– Short range (10 m), low power consumption, licensefree 2.45 GHz ISM
– Voice and data transmission, approx. 1 Mbit/s gross
data rate
One of the first modules (Ericsson).
CEG436: Mobile Computing (PM)
95
Bluetooth
(was:
)
• History
– 1994: Ericsson (Mattison/Haartsen), “MC-link” project
– Renaming of the project: Bluetooth according to Harald “Blåtand” Gormsen
[son of Gorm], King of Denmark in the 10th century
– 1998: foundation of Bluetooth SIG, www.bluetooth.org
– 1999: erection of a rune stone at Ercisson/Lund ;-)
– 2001: first consumer products for mass market, spec. version 1.1 released
– 2005: 5 million chips/week
• Special Interest Group
–
–
–
–
Original founding members: Ericsson, Intel, IBM, Nokia, Toshiba
Added promoters: 3Com, Agere (was: Lucent), Microsoft, Motorola
> 10000 members
Common specification and certification of products
CEG436: Mobile Computing (PM)
96
History and hi-tech…
1999:
Ericsson mobile
communications AB
reste denna sten till
minne av Harald
Blåtand, som fick ge
sitt namn åt en ny
teknologi för trådlös,
mobil kommunikation.
CEG436: Mobile Computing (PM)
97
…and the real rune stone
Located in Jelling, Denmark,
erected by King Harald “Blåtand”
in memory of his parents.
The stone has three sides – one side
showing a picture of Christ.
Inscription:
"Harald king executes these sepulchral
monuments after Gorm, his father and
Thyra, his mother. The Harald who won the
whole of Denmark and Norway and turned
the Danes to Christianity."
Btw: Blåtand means “of dark complexion”
(not having a blue tooth…)
CEG436: Mobile Computing (PM)
This could be the “original” colors
of the stone.
Inscription:
“auk tani karthi kristna” (and
made the Danes Christians)
98
Characteristics
•
2.4 GHz ISM band, 79 (23) RF channels, 1 MHz carrier spacing
– Channel 0: 2402 MHz … channel 78: 2480 MHz
– G-FSK modulation, 1-100 mW transmit power
•
FHSS and TDD
– Frequency hopping with 1600 hops/s
– Hopping sequence in a pseudo random fashion, determined by a master
– Time division duplex for send/receive separation
•
Voice link – SCO (Synchronous Connection Oriented)
– FEC (forward error correction), no retransmission, 64 kbit/s duplex, point-to-point,
circuit switched
•
Data link – ACL (Asynchronous ConnectionLess)
– Asynchronous, fast acknowledge, point-to-multipoint, up to 433.9 kbit/s symmetric
or 723.2/57.6 kbit/s asymmetric, packet switched
•
Topology
– Overlapping piconets (stars) forming a scatternet
CEG436: Mobile Computing (PM)
99
•
•
Piconet
Collection of devices connected in an ad hoc
fashion
One unit acts as master and the others as slaves for
the lifetime of the piconet
P
S
S
M
•
Master determines hopping pattern, slaves have to
synchronize
•
Each piconet has a unique hopping pattern
•
Participation in a piconet = synchronization to
hopping sequence
•
Each piconet has one master and up to 7
simultaneous slaves (> 200 could be parked)
CEG436: Mobile Computing (PM)
P
SB
S
P
M=Master
S=Slave
SB
P=Parked
SB=Standby
100
Forming a piconet
• All devices in a piconet hop together
– Master gives slaves its clock and device ID
• Hopping pattern: determined by device ID (48 bit,
unique worldwide)
P 
• Phase in hopping pattern determined by clock
S
 SB 
SB
• Addressing
S
M
P
 SB
– ActiveMember
Address (AMA, 3 bit)

SB
SB
 SB
S
– Parked Member Address (PMA, 8 bit) 

 SB
SB
P  SB
 SB
SB
CEG436: Mobile Computing (PM)
101
Scatternet
• Linking of multiple co-located piconets
through the sharing of common master or
slave devices
Piconets
(each with a
P slave in one piconet and master
– Devices can be
of
S
capacity of
S
720 kbit/s)
another
S
P
• Communication
M between piconets
P
M
SB jumping back
– Devices
S and forth between the
M=Masterpiconets
P
SB
SB
S=Slave
P=Parked
SB=Standby
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S
102
Bluetooth protocol stack
audio apps. NW apps.
TCP/UDP
vCal/vCard
telephony apps.
OBEX
AT modem
commands
IP
mgmnt. apps.
TCS BIN SDP
BNEP PPP
Control
RFCOMM (serial line interface)
Audio
Logical Link Control and Adaptation Protocol (L2CAP)
Link Manager
Host
Controller
Interface
Baseband
Radio
AT: attention sequence
OBEX: object exchange
TCS BIN: telephony control protocol specification – binary
BNEP: Bluetooth network encapsulation protocol
CEG436: Mobile Computing (PM)
SDP: service discovery protocol
RFCOMM: radio frequency comm.
103
625 µs
Frequency selection during data
transmission
fk
M
fk+1
S
fk+2
M
fk+3
S
fk+4
M
fk+5
S
fk+6
M
t
fk
M
fk+3
S
fk+4
M
fk+5
S
fk+6
M
t
fk
M
fk+1
S
fk+6
M
t
CEG436: Mobile Computing (PM)
104
Baseband
• Piconet/channel definition
• Low-level packet definition
– Access code
• Channel, device access, e.g., derived from master
68(72)
– Packet header
54
0-2745
bits
access code packet header payload
• 1/3-FEC, active member address (broadcast + 7 slaves),
link type, alternating bit ARQ/SEQ, checksum
4
64
preamble sync.
(4)
3
(trailer) AM address
CEG436: Mobile Computing (PM)
4
1
type
flow
1
ARQN
1
SEQN
8
bits
HEC
105
SCO payload types
payload (30)
HV1
audio (10)
HV2
audio (20)
HV3
audio (30)
DV
audio (10)
FEC (20)
FEC (10)
header (1) payload (0-9)
2/3 FEC
CRC (2)
(bytes)
CEG436: Mobile Computing (PM)
106
ACL Payload types
payload (0-343)
header (1/2)
payload (0-339)
DM1 header (1) payload (0-17)
DH1
header (1) payload (0-27)
DM3 header (2)
payload (0-121)
DH3
header (2)
payload (0-183)
DM5 header (2)
payload (0-224)
DH5
payload (0-339)
header (2)
CRC (2)
2/3 FEC CRC (2)
(bytes)
CRC (2)
2/3 FEC
CRC (2)
CRC (2)
2/3 FEC
CRC (2)
CRC (2)
AUX1 header (1) payload (0-29)
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107
Baseband data rates
ACL
1 slot
3 slot
5 slot
SCO
Type
Payload User
Header Payload
[byte]
[byte]
FEC
CRC
Symmetric Asymmetric
max. Rate max. Rate [kbit/s]
[kbit/s]
Forward
Reverse
DM1
1
0-17
2/3
yes
108.8
108.8
108.8
DH1
1
0-27
no
yes
172.8
172.8
172.8
DM3
2
0-121
2/3
yes
258.1
387.2
54.4
DH3
2
0-183
no
yes
390.4
585.6
86.4
DM5
2
0-224
2/3
yes
286.7
477.8
36.3
DH5
2
0-339
no
yes
433.9
723.2
57.6
AUX1
1
0-29
no
no
185.6
185.6
185.6
HV1
na
10
1/3
no
64.0
HV2
na
20
2/3
no
64.0
HV3
na
30
no
no
64.0
DV
1D
10+(0-9) D 2/3 D yes D
64.0+57.6 D
Data Medium/High rate, High-quality Voice, Data and Voice
CEG436: Mobile Computing (PM)
108
Baseband link types
• Polling-based TDD packet transmission
– 625µs slots, master polls slaves
• SCO (Synchronous Connection Oriented) – Voice
– Periodic single slot packet assignment, 64 kbit/s full-duplex, point-to-point
• ACL (Asynchronous ConnectionLess) – Data
– Variable packet size (1, 3, 5 slots), asymmetric bandwidth, point-to-multipoint
MASTER
SLAVE 1
SLAVE 2
SCO
f0
ACL
f4
SCO
f6
f1
ACL
f8
f7
f5
SCO
f12
f9
ACL
f14
SCO
f18
f13
ACL
f20
f19
f17
f21
Robustness
• Slow frequency hopping with hopping patterns determined by a master
– Protection from interference on certain frequencies
– Separation from other piconets (FH-CDMA)
• Retransmission
– ACL only, very fast
Error in payload
(not header!)
• Forward Error Correction
– SCO and ACL
MASTER
SLAVE 1
SLAVE 2
NAK
A
C
B
C
D
F
ACK
H
E
G
G
Baseband states of a Bluetooth device
unconnected
standby
detach
inquiry
transmit
AMA
park
PMA
hold
AMA
Standby: do nothing
Inquire: search for other devices
Page: connect to a specific device
Connected: participate in a piconet
CEG436: Mobile Computing (PM)
page
connecting
connected
AMA
active
sniff
AMA
low power
Park: release AMA, get PMA
Sniff: listen periodically, not each slot
Hold: stop ACL, SCO still possible, possibly
participate in another piconet
111
Example: Power consumption/CSR
BlueCore2
• Typical Average Current Consumption1
– VDD=1.8V Temperature = 20°C
– Mode
•
•
•
•
•
•
•
•
•
•
•
•
SCO connection HV3 (1s interval Sniff Mode) (Slave)
SCO connection HV3 (1s interval Sniff Mode) (Master)
SCO connection HV1 (Slave)
SCO connection HV1 (Master)
ACL data transfer 115.2kbps UART (Master)
ACL data transfer 720kbps USB (Slave)
ACL data transfer 720kbps USB (Master)
ACL connection, Sniff Mode 40ms interval, 38.4kbps UART
ACL connection, Sniff Mode 1.28s interval, 38.4kbps UART
Parked Slave, 1.28s beacon interval, 38.4kbps UART
Standby Mode (Connected to host, no RF activity)
Deep Sleep Mode2
• Notes:
–
–
1
2
26.0 mA
26.0 mA
53.0 mA
53.0 mA
15.5 mA
53.0 mA
53.0 mA
4.0 mA
0.5 mA
0.6 mA
47.0 µA
20.0 µA
Current consumption is the sum of both BC212015A and the flash.
Current consumption is for the BC212015A device only.
CEG436: Mobile Computing (PM)
112
Example: Bluetooth/USB adapter (2002: 50€, today: some cents if integrated)
CEG436: Mobile Computing (PM)
113
L2CAP - Logical Link Control and
Adaptation Protocol
•
Simple data link protocol on top of baseband
•
Connection oriented, connectionless, and signaling channels
•
Protocol multiplexing
– RFCOMM, SDP, telephony control
•
Segmentation & reassembly
– Up to 64kbyte user data, 16 bit CRC used from baseband
•
QoS flow specification per channel
– Follows RFC 1363, specifies delay, jitter, bursts, bandwidth
•
Group abstraction
– Create/close group, add/remove member
CEG436: Mobile Computing (PM)
114
L2CAP logical channels
Master
Slave
L2CAP
L2CAP
2
d
L2CAP
1
1 d d d d 1
baseband
signalling
CEG436: Mobile Computing (PM)
Slave
baseband
ACL
connectionless
1
d
d
2
baseband
connection-oriented
115
L2CAP packet formats
Connectionless PDU
2
length
2
2
CID=2
0-65533
PSM
bytes
payload
Connection-oriented PDU
2
length
2
CID
0-65535
bytes
payload
Signalling command PDU
2
length
2
CID=1
bytes
One or more commands
1
code
CEG436: Mobile Computing (PM)
1
ID
2
length
0
data
116
Security
User input (initialization)
PIN (1-16 byte)
E2
link key (128 bit)
E3
encryption key (128 bit)
Pairing
Authentication key generation
(possibly permanent storage)
Authentication
Encryption key generation
(temporary storage)
Encryption
E2
link key (128 bit)
E3
encryption key (128 bit)
Keystream generator
Keystream generator
payload key
PIN (1-16 byte)
Ciphering
payload key
Cipher data
Data
CEG436: Mobile Computing (PM)
Data
117
SDP – Service Discovery Protocol
• Inquiry/response protocol for discovering services
–
–
–
–
–
–
Searching for and browsing services in radio proximity
Adapted to the highly dynamic environment
Can be complemented by others like SLP, Jini, Salutation, …
Defines discovery only, not the usage of services
Caching of discovered services
Gradual discovery
• Service record format
– Information about services provided by attributes
– Attributes are composed of an 16 bit ID (name) and a value
– values may be derived from 128 bit Universally Unique
Identifiers (UUID)
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118
Additional protocols to support legacy
protocols/apps.
• RFCOMM
– Emulation of a serial port (supports a large base of legacy applications)
– Allows multiple ports over a single physical channel
• Telephony Control Protocol Specification (TCS)
– Call control (setup, release)
– Group management
• OBEX
– Exchange of objects, IrDA replacement
• WAP
– Interacting with applications on cellular phones
CEG436: Mobile Computing (PM)
119
Profiles
Represent default solutions for a certain usage model
•
•
•
•
•
•
•
•
•
•
•
•
•
Generic Access Profile
Service Discovery Application Profile
Cordless Telephony Profile
Intercom Profile
Serial Port Profile
Headset Profile
Dial-up Networking Profile
Fax Profile
LAN Access Profile
Generic Object Exchange Profile
Object Push Profile
File Transfer Profile
Synchronization Profile
– Vertical slice through the protocol stack
– Basis for interoperability
CEG436: Mobile Computing (PM)
Protocols
•
Applications
Profiles
Additional Profiles
Advanced Audio Distribution
PAN
Audio Video Remote Control
Basic Printing
Basic Imaging
Extended Service Discovery
Generic Audio Video Distributio
120
Hands Free
Bluetooth versions
• Bluetooth 1.1
– also IEEE Standard 802.15.1-2002
– initial stable commercial standard
• Bluetooth 1.2
– also IEEE Standard 802.15.1-2005
– eSCO (extended SCO): higher, variable bitrates, retransmission for SCO
– AFH (adaptive frequency hopping) to avoid interference
• Bluetooth 2.0 + EDR (2004, no more IEEE)
– EDR (enhanced date rate) of 3.0 Mbit/s for ACL and eSCO
– lower power consumption due to shorter duty cycle
• Bluetooth 2.1 + EDR (2007)
– better pairing support, e.g. using NFC
– improved security
• Bluetooth 3.0 + HS (2009)
– Bluetooth 2.1 + EDR + IEEE 802.11a/g = 54 Mbit/s
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121
WPAN: IEEE 802.15.1 – Bluetooth
•
Data rate
– Synchronous, connection-oriented:
64 kbit/s
– Asynchronous, connectionless
• 433.9 kbit/s symmetric
• 723.2 / 57.6 kbit/s asymmetric
•
Transmission range
– POS (Personal Operating Space) up to
10 m
– with special transceivers up to 100 m
•
Frequency
– Free 2.4 GHz ISM-band
•
Security
– Challenge/response (SAFER+),
hopping sequence
•
Availability
– Integrated into many products,
several vendors
CEG436: Mobile Computing (PM)
•
Connection set-up time
– Depends on power-mode
– Max. 2.56s, avg. 0.64s
•
Quality of Service
– Guarantees, ARQ/FEC
•
Manageability
– Public/private keys needed, key
management not specified, simple
system integration
•
Special Advantages/Disadvantages
– Advantage: already integrated into
several products, available
worldwide, free ISM-band, several
vendors, simple system, simple adhoc networking, peer to peer,
scatternets
– Disadvantage: interference on ISMband, limited range, max. 8 active
devices/network, high set-up latency
122
WPAN: IEEE 802.15 – future
developments 1
• 802.15.2: Coexistance
– Coexistence of Wireless Personal Area Networks (802.15) and Wireless
Local Area Networks (802.11), quantify the mutual interference
• 802.15.3: High-Rate
– Standard for high-rate (20Mbit/s or greater) WPANs, while still lowpower/low-cost
– Data Rates: 11, 22, 33, 44, 55 Mbit/s
– Quality of Service isochronous protocol
– Ad hoc peer-to-peer networking
– Security
– Low power consumption
– Low cost
– Designed to meet the demanding requirements of portable consumer
imaging and multimedia applications
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123
WPAN: IEEE 802.15 – future
developments 2
•
Several working groups extend the 802.15.3 standard
•
802.15.3a: - withdrawn – Alternative PHY with higher data rate as extension to 802.15.3
– Applications: multimedia, picture transmission
•
802.15.3b:
– Enhanced interoperability of MAC
– Correction of errors and ambiguities in the standard
•
802.15.3c:
– Alternative PHY at 57-64 GHz
– Goal: data rates above 2 Gbit/s
•
Not all these working groups really create a standard, not all standards will be
found in products later …
CEG436: Mobile Computing (PM)
124
WPAN: IEEE 802.15 – future
developments 3
•
802.15.4: Low-Rate, Very Low-Power
– Low data rate solution with multi-month to multi-year battery life and very low
complexity
– Potential applications are sensors, interactive toys, smart badges, remote controls,
and home automation
– Data rates of 20-250 kbit/s, latency down to 15 ms
– Master-Slave or Peer-to-Peer operation
– Up to 254 devices or 64516 simpler nodes
– Support for critical latency devices, such as joysticks
– CSMA/CA channel access (data centric), slotted (beacon) or unslotted
– Automatic network establishment by the PAN coordinator
– Dynamic device addressing, flexible addressing format
– Fully handshaked protocol for transfer reliability
– Power management to ensure low power consumption
– 16 channels in the 2.4 GHz ISM band, 10 channels in the 915 MHz US ISM band and
one channel in the European 868 MHz band
•
Basis of the ZigBee technology – www.zigbee.org
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125
ZigBee
• Relation to 802.15.4 similar to Bluetooth / 802.15.1
• Pushed by Chipcon (now TI), ember, freescale (Motorola),
Honeywell, Mitsubishi, Motorola, Philips, Samsung…
• More than 260 members
– about 15 promoters, 133 participants, 111 adopters
– must be member to commercially use ZigBee spec
• ZigBee platforms comprise
– IEEE 802.15.4 for layers 1 and 2
– ZigBee protocol stack up to the applications
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126
WPAN: IEEE 802.15 – future
developments 4
•
•
•
•
802.15.4a:
–
–
–
Alternative PHY with lower data rate as extension to 802.15.4
Properties: precise localization (< 1m precision), extremely low power consumption, longer range
Two PHY alternatives
•
•
UWB (Ultra Wideband): ultra short pulses, communication and localization
CSS (Chirp Spread Spectrum): communication only
802.15.4b, c, d, e, f, g:
–
–
–
Extensions, corrections, and clarifications regarding 802.15.4
Usage of new bands, more flexible security mechanisms
RFID, smart utility neighborhood (high scalability)
802.15.5: Mesh Networking
–
–
Partial meshes, full meshes
Range extension, more robustness, longer battery live
802.15.6: Body Area Networks
–
Low power networks e.g. for medical or entertainment use
•
802.15.7: Visible Light Communication
•
Not all these working groups really create a standard, not all standards will be found in products
later …
CEG436: Mobile Computing (PM)
127
Some more IEEE standards for mobile
communications
• IEEE 802.16: Broadband Wireless Access / WirelessMAN / WiMax
–
–
–
–
Wireless distribution system, e.g., for the last mile, alternative to DSL
75 Mbit/s up to 50 km LOS, up to 10 km NLOS; 2-66 GHz band
Initial standards without roaming or mobility support
802.16e adds mobility support, allows for roaming at 150 km/h
• IEEE 802.20: Mobile Broadband Wireless Access (MBWA)
–
–
–
–
Licensed bands < 3.5 GHz, optimized for IP traffic
Peak rate > 1 Mbit/s per user
Different mobility classes up to 250 km/h and ranges up to 15 km
Relation to 802.16e unclear
• IEEE 802.21: Media Independent Handover Interoperability
– Standardize handover between different 802.x and/or non 802 networks
• IEEE 802.22: Wireless Regional Area Networks (WRAN)
– Radio-based PHY/MAC for use by license-exempt devices on a non-interfering
basis in spectrum that is allocated to the TV Broadcast Service
CEG436: Mobile Computing (PM)
128
RF Controllers – ISM bands
•
Data rate
•
– Typ. up to 115 kbit/s (serial interface)
•
Transmission range
– 5-100 m, depending on power (typ.
10-500 mW)
•
Frequency
– Typ. 27 (EU, US), 315 (US), 418 (EU),
426 (Japan), 433 (EU), 868 (EU), 915
(US) MHz (depending on regulations)
•
Security
– Some products with added
processors
•
Cost
– Cheap: 10€-50€
•
Availability
Connection set-up time
– N/A
•
Quality of Service
– none
•
Manageability
– Very simple, same as serial interface
•
Special Advantages/Disadvantages
– Advantage: very low cost, large
experience, high volume available
– Disadvantage: no QoS, crowded ISM
bands (particularly 27 and 433 MHz),
typ. no Medium Access Control, 418
MHz experiences interference with
TETRA
– Many products, many vendors
CEG436: Mobile Computing (PM)
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RFID – Radio Frequency Identification
(1)
•
•
Data rate
– Transmission of ID only (e.g., 48 bit,
64kbit, 1 Mbit)
– 9.6 – 115 kbit/s
Transmission range
– Passive: up to 3 m
– Active: up to 30-100 m
– Simultaneous detection of up to, e.g.,
256 tags, scanning of, e.g., 40 tags/s
•
Frequency
•
Security
•
Cost
•
Availability
– 125 kHz, 13.56 MHz, 433 MHz, 2.4
GHz, 5.8 GHz and many others
– Application dependent, typ. no crypt.
on RFID device
– Very cheap tags, down to 1€ (passive)
– Many products, many vendors
CEG436: Mobile Computing (PM)
•
Connection set-up time
– Depends on product/medium access
scheme (typ. 2 ms per device)
•
Quality of Service
– none
•
Manageability
– Very simple, same as serial interface
•
Special Advantages/Disadvantages
– Advantage: extremely low cost, large
experience, high volume available, no
power for passive RFIDs needed,
large variety of products, relative
speeds up to 300 km/h, broad temp.
range
– Disadvantage: no QoS, simple denial
of service, crowded ISM bands, typ.
one-way (activation/ transmission of
ID)
130
RFID – Radio Frequency Identification
(2)
• Function
– Standard: In response to a radio interrogation signal from a
reader (base station) the RFID tags transmit their ID
– Enhanced: additionally data can be sent to the tags, different
media access schemes (collision avoidance)
• Features
– No line-of sight required (compared to, e.g., laser scanners)
– RFID tags withstand difficult environmental conditions (sunlight,
cold, frost, dirt etc.)
– Products available with read/write memory, smart-card
capabilities
• Categories
– Passive RFID: operating power comes from the reader over the
air which is feasible up to distances of 3 m, low price (1€)
– Active RFID: battery powered, distances up to 100 m
CEG436: Mobile Computing (PM)
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RFID – Radio Frequency Identification
(3)
• Applications
– Total asset visibility: tracking of goods during manufacturing,
localization of pallets, goods etc.
– Loyalty cards: customers use RFID tags for payment at, e.g., gas
stations, collection of buying patterns
– Automated toll collection: RFIDs mounted in windshields allow
commuters to drive through toll plazas without stopping
– Others: access control, animal identification, tracking of
hazardous material, inventory control, warehouse management,
...
• Local Positioning Systems
– GPS useless indoors or underground, problematic in cities with
high buildings
– RFID tags transmit signals, receivers estimate the tag location by
measuring the signal‘s time of flight
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RFID – Radio Frequency Identification
(4)
• Security
– Denial-of-Service attacks are always possible
• Interference of the wireless transmission, shielding of transceivers
– IDs via manufacturing or one time programming
– Key exchange via, e.g., RSA possible, encryption via, e.g., AES
• Future Trends
– RTLS: Real-Time Locating System – big efforts to make total
asset visibility come true
– Integration of RFID technology into the manufacturing,
distribution and logistics chain
– Creation of „electronic manifests“ at item or package level
(embedded inexpensive passive RFID tags)
– 3D tracking of children, patients
CEG436: Mobile Computing (PM)
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RFID – Radio Frequency Identification
(5)
•
Relevant Standards
–
American National Standards Institute
•
–
Automatic Identification and Data Capture Techniques
•
–
ISO TC 104 / SC 4, www.autoid.org/tc104_sc4_wg2.htm,
www.aimglobal.org/standards/rfidstds/TC104.htm
Road Transport and Traffic Telematics
•
–
JTC 1/SC 17, www.sc17.com, www.aimglobal.org/standards/rfidstds/sc17.htm,
Identification and communication
•
–
ETSI, www.etsi.org, www.aimglobal.org/standards/rfidstds/ETSI.htm
Identification Cards and related devices
•
–
ERO, www.ero.dk, www.aimglobal.org/standards/rfidstds/ERO.htm
European Telecommunications Standards Institute
•
–
JTC 1/SC 31, www.uc-council.com/sc31/home.htm,
www.aimglobal.org/standards/rfidstds/sc31.htm
European Radiocommunications Office
•
–
ANSI, www.ansi.org, www.aimglobal.org/standards/rfidstds/ANSIT6.html
CEN TC 278, www.nni.nl, www.aimglobal.org/standards/rfidstds/CENTC278.htm
Transport Information and Control Systems
•
ISO/TC204, www.sae.org/technicalcommittees/gits.htm,
www.aimglobal.org/standards/rfidstds/ISOTC204.htm
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RFID – Radio Frequency Identification
(6)
• ISO Standards
– ISO 15418
• MH10.8.2 Data Identifiers
• EAN.UCC Application Identifiers
– ISO 15434 - Syntax for High Capacity ADC Media
– ISO 15962 - Transfer Syntax
– ISO 18000
•
•
•
•
•
Part 2, 125-135 kHz
Part 3, 13.56 MHz
Part 4, 2.45 GHz
Part 5, 5.8 GHz
Part 6, UHF (860-930 MHz, 433 MHz)
– ISO 18047 - RFID Device Conformance Test Methods
– ISO 18046 - RF Tag and Interrogator Performance Test Methods
CEG436: Mobile Computing (PM)
135
ISM band interference
OLD
• Many sources of interference
–
–
–
–
–
Microwave ovens, microwave lighting
802.11, 802.11b, 802.11g, 802.15, …
Even analog TV transmission, surveillance
Unlicensed metropolitan area networks
…
NEW
• Levels of interference
– Physical layer: interference acts like noise
• Spread spectrum tries to minimize this
• FEC/interleaving tries to correct
© Fusion Lighting, Inc.,
now used by LG as
Plasma Lighting System
– MAC layer: algorithms not harmonized
• E.g., Bluetooth might confuse 802.11
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802.11 vs.(?) 802.15/Bluetooth
DIFS
802.15.1
79 channels
SIFS
ACK
SIFS
DIFS ACK
100
byte
DIFS
100
byte
(separated by
installation)
500 byte
SIFS
ACK
SIFS
ACK
DIFS
100
byte
SIFS
DIFS ACK
DIFS
SIFS
DIFS ACK
100
byte
500 byte
SIFS
ACK
2402
SIFS
ACK
500 byte
DIFS
DIFS
DIFS
f [MHz]
• Bluetooth may act like a rogue member of the 802.11 network
802.11b
2480 – Does not know anything about gaps, inter frame spacing etc.
3 channels
1000 byte
100
byte
(separated by
hopping pattern)
t
• IEEE 802.15-2 discusses these problems
– Proposal: Adaptive Frequency Hopping
• a non-collaborative Coexistence Mechanism
• Real effects? Many different opinions, publications, tests, formulae, …
– Results from complete breakdown to almost no effect
– Bluetooth (FHSS) seems more robust than 802.11b (DSSS)
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Wireless IEEE 802.11
• Traditional
• Bluetooth
• Infrared
CEG436: Mobile Computing (PM)
138
The WiMAX Possibility
• Wireless & Mobile Broadband at 10-30 miles range
CEG436: Mobile Computing (PM)
139

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