C07 wireless la-ns

Mobile Communications
Chapter 7: Wireless LANs
 Characteristics  HIPERLAN
 IEEE 802.11  Bluetooth / IEEE 802.15.x
 PHY  IEEE 802.16/.20/.21/.22
 MAC  RFID
 Roaming
 Comparison
 .11a, b, g, h, i …

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/

Mobile Communication Technology according to IEEE

WiFi
Local wireless networks 802.11a 802.11h
WLAN 802.11 802.11i/e/…/w
802.11b 802.11g

ZigBee
802.15.4 802.15.4a/b
Personal wireless nw
WPAN 802.15 802.15.5
802.15.2 802.15.3 802.15.3a/b
802.15.1
Bluetooth
Wireless distribution networks
WMAN 802.16 (Broadband Wireless Access) WiMAX
+ Mobility
802.20 (Mobile Broadband Wireless Access)


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 802.11)
 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


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


Comparison: infrared vs. radio transmission

Infrared Radio
 uses IR diodes, diffuse light,  typically using the license free
multiple reflections (walls, ISM band at 2.4 GHz
furniture etc.) Advantages
Advantages  experience from wireless WAN
 simple, cheap, available in and mobile phones can be used
many mobile devices  coverage of larger areas
 no licenses needed possible (radio can penetrate
 simple shielding possible walls, furniture etc.)
Disadvantages Disadvantages
 interference by sunlight, heat  very limited license free
sources etc. frequency bands
 many things shield or absorb IR  shielding more difficult,

light interference with other electrical
 low bandwidth devices

Example Example
 Many different products
 IrDA (Infrared Data Association)
interface available everywhere


Comparison: infrastructure vs. ad-hoc networks

infrastructure
network
AP: Access Point
AP

AP wired network
AP

ad-hoc network


802.11 - Architecture of an infrastructure network

Station (STA)
802.11 LAN  terminal with access mechanisms
802.x LAN
to the wireless medium and radio
contact to the access point
STA1 Basic Service Set (BSS)
BSS1  group of stations using the same
Access Portal
radio frequency
Point
Access Point
Distribution System  station integrated into the wireless
LAN and the distribution system
Access
ESS Point Portal
 bridge to other (wired) networks
BSS2
Distribution System
 interconnection network to form
one logical network (EES:
Extended Service Set) based
STA2 802.11 LAN STA3 on several BSS


802.11 - Architecture of an ad-hoc network

Direct communication within a limited
802.11 LAN
range
 Station (STA):
terminal with access mechanisms to
the wireless medium
STA1  Independent Basic Service Set
IBSS1 STA3
(IBSS):
group of stations using the same
radio frequency
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 802.3 PHY


802.11 - Layers and functions

MAC PLCP Physical Layer Convergence Protocol
 access mechanisms, fragmentation,  clear channel assessment signal
encryption (carrier sense)
MAC Management PMD Physical Medium Dependent
 synchronization, roaming, MIB,  modulation, coding
power management PHY Management
 channel selection, MIB
Station Management
 coordination of all management
functions

LLC
DLC

MAC MAC Management

PLCP
PHY

PHY Management
PMD
a Mnot a S
i t


802.11 - Physical layer (classical)

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


FHSS PHY packet format

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)
HEC (Header Error Check)
 CRC with x16+x12+x5+1

80 16 12 4 16 variable bits
synchronization SFD PLW PSF HEC payload

PLCP preamble PLCP header


DSSS PHY packet format
Synchronization
 synch., gain setting, energy detection, frequency offset compensation
SFD (Start Frame Delimiter)
 1111001110100000
Signal
 data rate of the payload (0A: 1 Mbit/s DBPSK; 14: 2 Mbit/s DQPSK)
Service Length
 future use, 00: 802.11 compliant  length of the payload
HEC (Header Error Check)
 protection of signal, service and length, x16+x12+x5+1

128 16 8 8 16 16 variable bits
synchronization SFD signal service length HEC payload



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


802.11 - MAC layer II

Priorities
 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
PIFS
SIFS
medium busy contention next frame
t
direct access if
medium is free ≥ DIFS


802.11 - CSMA/CA access method I

contention window
DIFS DIFS (randomized back-off
mechanism)

medium busy next frame

direct access if t
medium is free ≥ DIFS slot time

 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 time of
the station, the back-off timer stops (fairness)


802.11 - competing stations - simple version

DIFS DIFS DIFS DIFS
boe bor boe bor boe busy
station1

boe busy
station2

busy
station3

boe busy boe bor
station4

boe bor boe busy boe bor
station5
t

busy medium not idle (frame, ack etc.) boe elapsed backoff time

packet arrival at MAC bor residual backoff time


802.11 - CSMA/CA access method II

Sending unicast packets
 station has to wait for DIFS before sending data
 receivers acknowledge at once (after waiting for SIFS) if the packet was
received correctly (CRC)
 automatic retransmission of data packets in case of transmission errors

DIFS
data
sender
SIFS
ACK
receiver
DIFS
other data
stations t
waiting time contention


802.11 - DFWMAC

Sending unicast packets
 station can send RTS with reservation parameter after waiting for DIFS
(reservation determines amount of time the data packet needs the medium)
 acknowledgement via CTS after SIFS by receiver (if ready to receive)
 sender can now send data at once, acknowledgement via ACK
 other stations store medium reservations distributed via RTS and CTS

DIFS
RTS data
sender
SIFS SIFS
CTS SIFS ACK
receiver

NAV (RTS) DIFS
other NAV (CTS) data
stations t
defer access contention


Fragmentation

DIFS
RTS frag1 frag2
sender
SIFS SIFS SIFS
CTS SIFS ACK1 SIFS ACK2
receiver

NAV (RTS)
NAV (CTS)
NAV (frag1) DIFS
other NAV (ACK1) data
stations t
contention


DFWMAC-PCF I

t0 t1
SuperFrame

medium busy PIFS SIFS SIFS
D1 D2
point
coordinator SIFS SIFS
U1 U2
wireless
stations
stations‘ NAV
NAV


DFWMAC-PCF II

t2 t3 t4

PIFS SIFS
D3 D4 CFend
point
coordinator SIFS
U4
wireless
stations
stations‘ NAV
NAV contention free period contention t
period


802.11 - Frame format

Types
 control frames, management frames, data frames
Sequence numbers
 important against duplicated frames due to lost ACKs
Addresses
 receiver, transmitter (physical), BSS identifier, sender (logical)
Miscellaneous
 sending time, checksum, frame control, data
bytes 2 2 6 6 6 2 6 0-2312 4
Frame Duration/ Address Address Address Sequence Address
Data CRC
Control ID 1 2 3 Control 4

bits 2 2 4 1 1 1 1 1 1 1 1
Protocol To From More Power More
Type Subtype Retry WEP Order
version DS DS Frag Mgmt Data


MAC address format

scenario to DS from address 1 address 2 address 3 address 4
DS
ad-hoc network 0 0 DA SA BSSID -
infrastructure 0 1 DA BSSID SA -
network, from AP
infrastructure 1 0 BSSID SA DA -
network, to AP
infrastructure 1 1 RA TA DA SA
network, within DS

DS: Distribution System
AP: Access Point
DA: Destination Address
SA: Source Address
BSSID: Basic Service Set Identifier
RA: Receiver Address
TA: Transmitter Address


Special Frames: ACK, RTS, CTS

Acknowledgement
bytes 2 2 6 4
ACK Frame Receiver
Duration CRC
Control Address

Request To Send
bytes 2 2 6 6 4
Frame Receiver Transmitter
RTS Duration CRC
Control Address Address

Clear To Send
bytes 2 2 6 4
Frame Receiver
CTS Duration CRC
Control Address


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


Synchronization using a Beacon (infrastructure)

beacon interval

B B B B
access
point
busy busy busy busy
medium
t
value of the timestamp B beacon frame


Synchronization using a Beacon (ad-hoc)

beacon interval

B1 B1
station1

B2 B2
station2

busy busy busy busy
medium
t
value of the timestamp B beacon frame random delay


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?)


Power saving with wake-up patterns (infrastructure)

TIM interval DTIM interval

D B T T d D B
access
point
busy busy busy busy
medium

p d
station
t
T TIM D DTIM awake

B broadcast/multicast p PS poll d data transmission
to/from the station


Power saving with wake-up patterns (ad-hoc)

ATIM
window beacon interval

B1 A D B1
station1

B2 B2 a d
station2

t
B beacon frame random delay A transmit ATIM D transmit data

awake a acknowledge ATIM d acknowledge data


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


WLAN: IEEE 802.11b

Data rate Connection set-up time
 1, 2, 5.5, 11 Mbit/s, depending on  Connectionless/always on
SNR Quality of Service
 User data rate max. approx. 6  Typ. Best effort, no guarantees
Mbit/s (unless polling is used, limited
support in products)
Transmission range
Manageability
 300m outdoor, 30m indoor  Limited (no automated key
 Max. data rate ~10m indoor
distribution, sym. Encryption)
Frequency Special Advantages/Disadvantages
 Free 2.4 GHz ISM-band  Advantage: many installed systems,
lot of experience, available
Security worldwide, free ISM-band, many
 Limited, WEP insecure, SSID vendors, integrated in laptops,
Availability simple system
 Disadvantage: heavy interference
 Many products, many vendors
on ISM-band, no service
guarantees, slow relative speed
only


IEEE 802.11b – PHY frame formats

Long PLCP PPDU format
synchronization SFD signal service length HEC payload


192 µs at 1 Mbit/s DBPSK 1, 2, 5.5 or 11 Mbit/s

Short PLCP PPDU format (optional)
short synch. SFD signal service length HEC payload

(1 Mbit/s, DBPSK) (2 Mbit/s, DQPSK)

96 µs 2, 5.5 or 11 Mbit/s


Channel selection (non-overlapping)

Europe (ETSI)

channel 1 channel 7 channel 13

2400 2412 2442 2472 2483.5
22 MHz [MHz]
US (FCC)/Canada (IC)

channel 1 channel 6 channel 11

2400 2412 2437 2462 2483.5
22 MHz [MHz]


WLAN: IEEE 802.11a
 6, 9, 12, 18, 24, 36, 48, 54 Mbit/s,  Connectionless/always on
depending on SNR
 User throughput (1500 byte packets): 5.3
Quality of Service
(6), 18 (24), 24 (36), 32 (54)  Typ. best effort, no guarantees (same as
 6, 12, 24 Mbit/s mandatory all 802.11 products)
Transmission range Manageability
 100m outdoor, 10m indoor  Limited (no automated key distribution,
 E.g., 54 Mbit/s up to 5 m, 48 up to 12 m, sym. Encryption)
36 up to 25 m, 24 up to 30m, 18 up to 40
m, 12 up to 60 m Special Advantages/Disadvantages
Frequency  Advantage: fits into 802.x standards, free
 Free 5.15-5.25, 5.25-5.35, 5.725-5.825 ISM-band, available, simple system,
GHz ISM-band uses less crowded 5 GHz band
Security  Disadvantage: stronger shading due to
 Limited, WEP insecure, SSID higher frequency, no QoS
Availability
 Some products, some vendors


IEEE 802.11a – PHY frame format

4 1 12 1 6 16 variable 6 variable bits
rate reserved length parity tail service payload tail pad

PLCP header

PLCP preamble signal data
12 1 variable symbols

6 Mbit/s 6, 9, 12, 18, 24, 36, 48, 54 Mbit/s


Operating channels for 802.11a / US U-NII

36 40 44 48 52 56 60 64 channel

5150 5180 5200 5220 5240 5260 5280 5300 5320 5350 [MHz]
16.6 MHz

center frequency =
5000 + 5*channel number [MHz]
149 153 157 161 channel

5725 5745 5765 5785 5805 5825 [MHz]
16.6 MHz


OFDM in IEEE 802.11a (and HiperLAN2)

OFDM with 52 used subcarriers (64 in total)
 48 data + 4 pilot
 (plus 12 virtual subcarriers)
 312.5 kHz spacing

pilot 312.5 kHz

-26 -21 -7 -1 1 7 21 26 subcarrier
channel center frequency number


WLAN: IEEE 802.11 – future developments (03/2005)

802.11c: Bridge Support
 Definition of MAC procedures to support bridges as extension to 802.1D
802.11d: Regulatory Domain Update
 Support of additional regulations related to channel selection, hopping sequences
802.11e: MAC Enhancements – QoS
 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…
 Additional energy saving mechanisms and more efficient retransmission

802.11f: Inter-Access Point Protocol
 Establish an Inter-Access Point Protocol for data exchange via the distribution
system
 Currently unclear to which extend manufacturers will follow this suggestion

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)


WLAN: IEEE 802.11– future developments (03/2005)
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
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
802.11k: 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 standards
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


WLAN: IEEE 802.11– future developments (03/2005)
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
802.11s: Mesh Networking
 Design of a self-configuring Wireless Distribution System (WDS) based on 802.11
 Support of point-to-point and broadcast communication across several hops
802.11t: Performance evaluation of 802.11 networks
 Standardization of performance measurement schemes
802.11u: Interworking with additional external networks
802.11v: Network management
 Extensions of current management functions, channel measurements
 Definition of a unified interface
802.11w: Securing of network control
 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.

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/


ETSI – HIPERLAN (historical)

ETSI standard
 European standard, cf. GSM, DECT, ...
 Enhancement of local Networks and interworking with fixed networks
 integration of time-sensitive services from the early beginning

HIPERLAN family
 one standard cannot satisfy all requirements
 range, bandwidth, QoS support
 commercial constraints
 HIPERLAN 1 standardized since 1996 – no products!
higher layers
medium access logical link
network layer
control layer control layer
channel access medium access
data link layer
control layer control layer
physical layer physical layer physical layer

HIPERLAN layers OSI layers IEEE 802.x layers


Overview: original HIPERLAN protocol family

HIPERLAN 1 HIPERLAN 2 HIPERLAN 3 HIPERLAN 4
Application wireless LAN access to ATM wireless local point-to-point
fixed networks loop wireless ATM
connections
Frequency 5.1-5.3GHz 17.2-17.3GHz
Topology decentralized ad- cellular, point-to- point-to-point
hoc/infrastructure centralized multipoint
Antenna omni-directional directional
Range 50 m 50-100 m 5000 m 150 m
QoS statistical ATM traffic classes (VBR, CBR, ABR, UBR)
Mobility <10m/s stationary
Interface conventional LAN ATM networks
Data rate 23.5 Mbit/s >20 Mbit/s 155 Mbit/s
Power yes not necessary
conservation

HIPERLAN 1 never reached product status,
the other standards have been renamed/modfied !


HIPERLAN 1 - Characteristics

Data transmission
 point-to-point, point-to-multipoint, connectionless
 23.5 Mbit/s, 1 W power, 2383 byte max. packet size

Services
 asynchronous and time-bounded services with hierarchical priorities
 compatible with ISO MAC

Topology
 infrastructure or ad-hoc networks
 transmission range can be larger then coverage of a single node
(„forwarding“ integrated in mobile terminals)
Further mechanisms
 power saving, encryption, checksums


HIPERLAN 1 - Physical layer

Scope
 modulation, demodulation, bit and frame synchronization
 forward error correction mechanisms
 measurements of signal strength
 channel sensing

Channels
 3 mandatory and 2 optional channels (with their carrier frequencies)
 mandatory
 channel 0: 5.1764680 GHz
 channel 1: 5.1999974 GHz
 channel 2: 5.2235268 GHz
 optional
 channel 3: 5.2470562 GHz
 channel 4: 5.2705856 GHz


HIPERLAN 1 - Physical layer frames

Maintaining a high data-rate (23.5 Mbit/s) is power consuming -
problematic for mobile terminals
 packet header with low bit-rate comprising receiver information
 only receiver(s) address by a packet continue receiving

Frame structure
 LBR (Low Bit-Rate) header with 1.4 Mbit/s
 450 bit synchronization
 minimum 1, maximum 47 frames with 496 bit each
 for higher velocities of the mobile terminal (> 1.4 m/s) the maximum
number of frames has to be reduced
HBR

LBR synchronization data0 data1 ... datam-1

Modulation
 GMSK for high bit-rate, FSK for LBR header


HIPERLAN 1 - CAC sublayer

Channel Access Control (CAC)
 assure that terminal does not access forbidden channels
 priority scheme, access with EY-NPMA

Priorities
 5 priority levels for QoS support
 QoS is mapped onto a priority level with the help of the packet
lifetime (set by an application)
 if packet lifetime = 0 it makes no sense to forward the packet to the
receiver any longer
 standard start value 500ms, maximum 16000ms
 if a terminal cannot send the packet due to its current priority, waiting
time is permanently subtracted from lifetime
 based on packet lifetime, waiting time in a sender and number of hops to
the receiver, the packet is assigned to one out of five priorities
 the priority of waiting packets, therefore, rises automatically


HIPERLAN 1 - EY-NPMA I

EY-NPMA (Elimination Yield Non-preemptive Priority Multiple Access)
 3 phases: priority resolution, contention resolution, transmission
 finding the highest priority
 every priority corresponds to a time-slot to send in the first phase, the
higher the priority the earlier the time-slot to send
 higher priorities can not be preempted
 if an earlier time-slot for a higher priority remains empty, stations with the
next lower priority might send
 after this first phase the highest current priority has been determined
IPS IPA IES IESV IYS

elimination survival
elimination burst
priority detection

priority assertion

yield listening

user data
verification
not az no hc nys

transmission prioritization contention transmission t
i i r


HIPERLAN 1 - EY-NPMA II

Several terminals can now have the same priority and wish to send
 contention phase
 Elimination Burst: all remaining terminals send a burst to eliminate
contenders (11111010100010011100000110010110, high bit- rate)
 Elimination Survival Verification: contenders now sense the channel, if the
channel is free they can continue, otherwise they have been eliminated
 Yield Listening: contenders again listen in slots with a nonzero probability,
if the terminal senses its slot idle it is free to transmit at the end of the
contention phase
 the important part is now to set the parameters for burst duration and
channel sensing (slot-based, exponentially distributed)
 data transmission
 the winner can now send its data (however, a small chance of collision
remains)
 if the channel was idle for a longer time (min. for a duration of 1700 bit) a
terminal can send at once without using EY-NPMA
 synchronization using the last data transmission


HIPERLAN 1 - DT-HCPDU/AK-HCPDU

0 1 2 3 4 5 6 7 bit
LBR 1 0 1 0 1 0 1 0
0 1 2 3 4 5 6 7 bit 0 1 HI AID
LBR 1 0 1 0 1 0 1 0 AID AIDCS
0 1 HI HDA
HDA HDACS Acknowledgement HCPDU
BLIR = n BL-
HI: HBR-part Indicator
IRCS 1
bit
HDA: Hashed Destination HCSAP Address
0 1 2 3 4 5 6 7 byte HDACS: HDA CheckSum
HBR TI BLI = n 1 BLIR: Block Length Indicator
PLI = m 2 BLIRCS: BLIR CheckSum
HID 3-6 TI: Type Indicator
DA 7 - 12 BLI: Block Length Indicator
SA 13 - 18
HID: HIPERLAN IDentifier
UD 19 - (52n-m-4)
DA: Destination Address
PAD (52n-m-3) - (52n-4)
SA: Source Address
CS (52n-3) - 52n
UD: User Data (1-2422 byte)
PAD: PADding
Data HCPDU CS: CheckSum
AID: Acknowledgement IDentifier
AIDS: AID CheckSum


HIPERLAN 1 - MAC layer

Compatible to ISO MAC
Supports time-bounded services via a priority scheme
Packet forwarding
 support of directed (point-to-point) forwarding and broadcast forwarding (if
no path information is available)
 support of QoS while forwarding

Encryption mechanisms
 mechanisms integrated, but without key management
Power conservation mechanisms
 mobile terminals can agree upon awake patterns (e.g., periodic wake-ups
to receive data)
 additionally, some nodes in the networks must be able to buffer data for
sleeping terminals and to forward them at the right time (so called stores)


HIPERLAN 1 - DT-HMPDU

bit LI: Length Indicator
0 1 2 3 4 5 6 7 byte
LI = n 1-2
TI: Type Indicator
TI = 1 3 RL: Residual Lifetime
RL 4-5
PSN: Sequence Number
PSN 6-7
DA 8 - 13 DA: Destination Address
SA 14 - 19
SA: Source Address
ADA 20 - 25
ASA 26 - 31 ADA: Alias Destination Address
UP ML 32 ASA: Alias Source Address
ML 33
UP: User Priority
KID IV 34
IV 35 - 37 ML: MSDU Lifetime
UD 38 - (n-2)
KID: Key Identifier
SC (n-1) - n
IV: Initialization Vector
n= 40–2422 UD: User Data, 1–2383 byte
Data HMPDU
SC: Sanity Check (for the
unencrypted PDU)


Information bases

Route Information Base (RIB) - how to reach a destination
 [destination, next hop, distance]
Neighbor Information Base (NIB) - status of direct neighbors
 [neighbor, status]
Hello Information Base (HIB) - status of destination (via next hop)
 [destination, status, next hop]
Alias Information Base (AIB) - address of nodes outside the net
 [original MSAP address, alias MSAP address]
Source Multipoint Relay Information Base (SMRIB) - current MP status
 [local multipoint forwarder, multipoint relay set]
Topology Information Base (TIB) - current HIPERLAN topology
 [destination, forwarder, sequence]
Duplicate Detection Information Base (DDIB) - remove duplicates
 [source, sequence]


Ad-hoc networks using HIPERLAN 1
Information Bases (IB):
2 RIB RIB: Route
1 Forwarder NIB NIB: Neighbor
RIB HIB HIB: Hello
NIB AIB AIB: Alias
HIB DDIB SMRIB: Source Multipoint Relay
AIB
TIB: Topology
SMRIB
DDIB: Duplicate Detection
TIB
DDIB
4 Forwarder 3
RIB
5 NIB
RIB HIB
NIB RIB AIB
HIB NIB DDIB
AIB HIB
DDIB AIB RIB
SMRIB NIB 6
TIB HIB
DDIB AIB Forwarder
neighborhood SMRIB
TIB
(i.e., within radio range) DDIB


Some history: Why wireless ATM?

 seamless connection to wired ATM, a integrated services high-
performance network supporting different types a traffic streams
 ATM networks scale well: private and corporate LANs, WAN
 B-ISDN uses ATM as backbone infrastructure and integrates several
different services in one universal system
 mobile phones and mobile communications have an ever increasing
importance in everyday life
 current wireless LANs do not offer adequate support for multimedia
data streams
 merging mobile communication and ATM leads to wireless ATM from a
telecommunication provider point of view
 goal: seamless integration of mobility into B-ISDN

Problem: very high complexity of the system – never reached products


ATM - basic principle

 favored by the telecommunication industry for advanced high-performance
networks, e.g., B-ISDN, as transport mechanism
 statistical (asynchronous, on demand) TDM (ATDM, STDM)
 cell header determines the connection the user data belongs to
 mixing of different cell-rates is possible
 different bit-rates, constant or variable, feasible
 interesting for data sources with varying bit-rate:
 e.g., guaranteed minimum bit-rate
 additionally bursty traffic if allowed by the network

ATM cell:
5 48 [byte]

cell header user data

connection identifier, checksum etc.


Cell-based transmission

 asynchronous, cell-based transmission as basis for ATM
 continuous cell-stream
 additional cells necessary for operation and maintenance of the network
(OAM cells; Operation and Maintenance)
 OAM cells can be inserted after fixed intervals to create a logical frame
structure
 if a station has no data to send it automatically inserts idle cells that can be
discarded at every intermediate system without further notice
 if no synchronous frame is available for the transport of cells (e.g., SDH or
Sonet) cell boundaries have to be detected separately (e.g., via the
checksum in the cell header)


B-ISDN protocol reference model

3 dimensional reference model
 three vertical planes (columns)
 user plane
 control plane
 management plane
 three hierarchical layers management plane
 physical layer

plane management
control user
 ATM layer

layer management
plane plane
 ATM adaptation layer
higher higher
Out-of-Band-Signaling: user data is layers layers
transmitted separately from control
information ATM adaptation layer

ATM layer

physical layer
layers
planes


ATM layers

Physical layer, consisting of two sub-layers
 physical medium dependent sub-layer
 coding
 bit timing
 transmission
 transmission convergence sub-layer
 HEC (Header Error Correction) sequence generation and verification
 transmission frame adaptation, generation, and recovery
 cell delineation, cell rate decoupling

ATM layer
 cell multiplexing/demultiplexing
 VPI/VCI translation
 cell header generation and verification
 GFC (Generic Flow Control)

ATM adaptation layer (AAL)


ATM adaptation layer (AAL)

Provides different service classes on top of ATM based on:
 bit rate:
 constant bit rate: e.g. traditional telephone line
 variable bit rate: e.g. data communication, compressed video
 time constraints between sender and receiver:
 with time constraints: e.g. real-time applications, interactive voice and video
 without time constraints: e.g. mail, file transfer
 mode of connection:
 connection oriented or connectionless

AAL consists of two sub-layers:
 Convergence Sublayer (CS): service dependent adaptation
 Common Part Convergence Sublayer (CPCS)
 Service Specific Convergence Sublayer (SSCS)
 Segmentation and Reassembly Sublayer (SAR)
 sub-layers can be empty


ATM and AAL connections

end-system A end-system B

service dependent
AAL AAL connections
AAL

service independent
ATM ATM
ATM connections
physical physical
layer layer

 ATM layer: ATM network
 service independent transport of ATM cells application
 multiplex and demultiplex functionality
 AAL layer: support of different services


ATM Forum Wireless ATM Working Group

 ATM Forum founded the Wireless ATM Working Group June 1996
 Task: development of specifications to enable the use of ATM
technology also for wireless networks with a large coverage of
current network scenarios (private and public, local and global)
 compatibility to existing ATM Forum standards important
 it should be possible to easily upgrade existing ATM networks with
mobility functions and radio access
 two sub-groups of work items

Radio Access Layer (RAL) Protocols Mobile ATM Protocol Extensions
 radio access layer  handover signaling
 wireless media access control  location management
 wireless data link control  mobile routing
 radio resource control  traffic and QoS Control
 handover issues  network management


WATM services

Office environment
 multimedia conferencing, online multimedia database access
Universities, schools, training centers
 distance learning, teaching
Industry
 database connection, surveillance, real-time factory management
Hospitals
 reliable, high-bandwidth network, medical images, remote monitoring
Home
 high-bandwidth interconnect of devices (TV, CD, PC, ...)
Networked vehicles
 trucks, aircraft etc. interconnect, platooning, intelligent roads


WATM components

WMT (Wireless Mobile ATM Terminal)
RAS (Radio Access System)
EMAS-E (End-user Mobility-supporting ATM Switch - Edge)
EMAS-N (End-user Mobility-supporting ATM Switch - Network)
M-NNI (Network-to-Network Interface with Mobility support)
LS (Location Server)
AUS (Authentication Server)


Reference model

EMAS-N
WMT
RAS

EMAS-E

M-NNI
WMT RAS
EMAS-N

LS
AUS


User plane protocol layers

radio segment fixed network segment

MATM WATM fixed
EMAS EMAS ATM-
termi- terminal RAS end
-E -N Switch
nal adapter system

user
user process
process

AAL AAL

ATM
ATM ATM ATM ATM ATM
ATM- ATM-
CL CL
RAL RAL PHY PHY PHY PHY PHY PHY PHY PHY


Control plane protocol layers

radio segment fixed network segment

MATM WATM fixed
EMAS EMAS ATM-
termi- terminal RAS end
-E -N Switch
nal adapter system

SIG, SIG,
SIG, SIG, SIG,
M-UNI, PNNI,
M-UNI M-PNNI UNI
M-PNNI UNI
SAAL SAAL SAAL SAAL SAAL

M-ATM
ATM ATM ATM ATM ATM
ATM- ATM-
CL CL
RAL RAL PHY PHY PHY PHY PHY PHY PHY PHY


Reference model with further access scenarios I
1: wireless ad-hoc ATM network
2: wireless mobile ATM terminals
3: mobile ATM terminals
4: mobile ATM switches
5: fixed ATM terminals
6: fixed wireless ATM terminals

WMT: wireless mobile terminal
WT: wireless terminal
MT: mobile terminal
T: terminal
AP: access point
EMAS: end-user mobility supporting ATM switch (-E: edge, -N: network)
NMAS: network mobility supporting ATM switch
MS: mobile ATM switch


Reference model with further access scenarios II

1 WMT

RAS ACT WMT

2 EMAS EMAS
T 5
WMT RAS -E -N

EMAS
-E 6
MT
3 RAS WT

NMAS
MS
RAS
RAS
T
4


BRAN – Broadband Radio Access Networks

Motivation
 deregulation, privatization, new companies, new services
 How to reach the customer?
 alternatives: xDSL, cable, satellite, radio
Radio access
 flexible (supports traffic mix, multiplexing for higher efficiency, can be
asymmetrical)
 quick installation
 economic (incremental growth possible)

Market
 private customers (Internet access, tele-xy...)
 small and medium sized business (Internet, MM conferencing, VPN)

Scope of standardization
 access networks, indoor/campus mobility, 25-155 Mbit/s, 50 m-5 km
 coordination with ATM Forum, IETF, ETSI, IEEE, ....


Broadband network types

Common characteristics
 ATM QoS (CBR, VBR, UBR, ABR)
HIPERLAN/2
 short range (< 200 m), indoor/campus, 25 Mbit/s user data rate
 access to telecommunication systems, multimedia applications, mobility
(<10 m/s)
HIPERACCESS
 wider range (< 5 km), outdoor, 25 Mbit/s user data rate
 fixed radio links to customers (“last mile”), alternative to xDSL or cable
modem, quick installation
 Several (proprietary) products exist with 155 Mbit/s plus QoS

HIPERLINK – currently no activities
 intermediate link, 155 Mbit/s
 connection of HIPERLAN access points or connection between
HIPERACCESS nodes


BRAN and legacy networks

Independence
 BRAN as access network independent from the fixed network
 Interworking of TCP/IP and ATM under study

Layered model
 Network Convergence Sub-layer as superset of all requirements for IP and
ATM

Coordination
core network core network  IETF (TCP/IP)
ATM IP
 ATM forum (ATM)
network convergence sublayer  ETSI (UMTS)
 CEPT, ITU-R, ...
BRAN data link control (radio frequencies)

BRAN PHY-1 BRAN PHY-2 ...


HiperLAN2 (historical)

Official name: BRAN HIPERLAN Type 2
 H/2, HIPERLAN/2 also used
High data rates for users
 More efficient than 802.11a
Connection oriented
QoS support
Dynamic frequency selection
Security support
 Strong encryption/authentication
Mobility support
Network and application independent
 convergence layers for Ethernet, IEEE 1394, ATM, 3G
Power save modes
No products – but several mechanisms have been
Plug and Play Adopted by other standards (e.g. 802.11a)


HiperLAN2 architecture and handover scenarios

AP
MT1
APT APC Core
1 Network
MT2 (Ethernet,
Firewire,
3 AP ATM,
MT3 APT
UMTS)
APC
2
MT4 APT


Centralized vs. direct mode

AP AP/CC

control control
control
data
data
MT1 MT2 MT1 MT2 MT1 MT2 +CC
data control

Centralized Direct


HiperLAN2 protocol stack

Higher layers

DLC control Convergence layer DLC user
SAP SAP

Radio link control sublayer Data link control -
basic data
Radio DLC
resource
Assoc.
conn.
transport function
control Scope of
control control
HiperLAN2
Error
standards
control
Radio link control

Medium access control

Physical layer


Physical layer reference configuration

PDU train from DLC
(PSDU)
scrambling FEC coding interleaving

PHY bursts radio
mapping OFDM
(PPDU) transmitter


Operating channels of HiperLAN2 in Europe

36 40 44 48 52 56 60 64 channel

5150 5180 5200 5220 5240 5260 5280 5300 5320 5350 [MHz]
16.6 MHz

100 104 108 112 116 120 124 128 132 136 140 channel

5470 5500 5520 5540 5560 5580 5600 5620 5640 5660 5680 5700 5725
16.6 MHz [MHz]
center frequency =
5000 + 5*channel number [MHz]


Basic structure of HiperLAN2 MAC frames

2 ms 2 ms 2 ms 2 ms TDD,
MAC frame MAC frame MAC frame MAC frame 500 OFDM
...
symbols
per frame

random
broadcast phase downlink phase uplink phase
access phase
variable variable variable

2 406 24 bit

LCH PDU type payload CRC LCH transfer syntax

2 10 396 24 bit
sequence UDCH transfer syntax
LCH PDU type payload CRC
number (long PDU)

54 byte


Valid configurations of HiperLAN2 MAC frames

2 ms 2 ms 2 ms 2 ms
MAC frame MAC frame MAC frame MAC frame ...
random
broadcast downlink uplink access

BCH FCH ACH DL phase DiL phase UL phase RCHs Valid
combinations
BCH FCH ACH DiL phase UL phase RCHs of MAC frames
for a single
BCH FCH ACH DL phase UL phase RCHs sector AP

BCH FCH ACH UL phase RCHs

BCH FCH ACH DL phase DiL phase RCHs

BCH FCH ACH DiL phase RCHs

BCH FCH ACH DL phase RCHs

BCH FCH ACH RCHs


Mapping of logical and transport channels

BCCH FCCH RFCH LCCH RBCH DCCH UDCH UBCH UMCH

downlink

BCH FCH ACH SCH LCH

UDCH DCCH LCCH ASCH UDCH UBCH UMCH DCCH RBCH LCCH

LCH SCH RCH LCH SCH
uplink direct link


Bluetooth

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 (2005: 40€/USB bluetooth)
 Short range (10 m), low power consumption, license-free 2.45 GHz ISM
 Voice and data transmission, approx. 1 Mbit/s gross data rate

One of the first modules (Ericsson).


Bluetooth

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 (was: )
 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
 > 2500 members
 Common specification and certification of products


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.


…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 This could be the “original” colors
the Danes to Christianity." of the stone.
Inscription:
Btw: Blåtand means “of dark complexion” “auk tani karthi kristna” (and
(not having a blue tooth…) made the Danes Christians)


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


Piconet

Collection of devices connected in an ad hoc
fashion
P
S
One unit acts as master and the others as slaves
for the lifetime of the piconet S
M P

Master determines hopping pattern, slaves have
to synchronize SB S
P SB
Each piconet has a unique hopping pattern

Participation in a piconet = synchronization to
hopping sequence M=Master P=Parked
S=Slave SB=Standby
Each piconet has one master and up to 7
simultaneous slaves (> 200 could be parked)


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)
 Phase in hopping pattern determined by clock

Addressing
 Active Member Address (AMA, 3 bit)
 Parked Member Address (PMA, 8 bit)
P S
 
SB
SB S
SB M P
SB SB
SB S
SB SB P 
SB  SB
SB


Scatternet

Linking of multiple co-located piconets through the sharing of common
master or slave devices
 Devices can be slave in one piconet and master of another
Communication between piconets
 Devices jumping back and forth between the piconets
Piconets
(each with a
capacity of
P
S S 720 kbit/s)

S
P
P
M
M
SB S
M=Master P SB SB
S=Slave
P=Parked S
SB=Standby


Bluetooth protocol stack

audio apps. NW apps. vCal/vCard telephony apps. mgmnt. apps.

TCP/UDP OBEX
AT modem
IP
commands
TCS BIN SDP
BNEP PPP Control

RFCOMM (serial line interface)

Audio Logical Link Control and Adaptation Protocol (L2CAP) Host
Controller
Link Manager Interface

Baseband

Radio

AT: attention sequence SDP: service discovery protocol
OBEX: object exchange RFCOMM: radio frequency comm.
TCS BIN: telephony control protocol specification – binary
BNEP: Bluetooth network encapsulation protocol


Frequency selection during data transmission

625 µs

fk fk+1 fk+2 fk+3 fk+4 fk+5 fk+6

M S M S M S M
t

fk fk+3 fk+4 fk+5 fk+6

M S M S M
t

fk fk+1 fk+6

M S M
t


Baseband

Piconet/channel definition
Low-level packet definition
 Access code
 Channel, device access, e.g., derived from master
 Packet header
 1/3-FEC, active member address (broadcast + 7 slaves), link type, alternating
bit ARQ/SEQ, checksum

68(72) 54 0-2745 bits
access code packet header payload

4 64 (4) 3 4 1 1 1 8 bits
preamble sync. (trailer) AM address type flow ARQN SEQN HEC


SCO payload types

payload (30)

HV1 audio (10) FEC (20)

HV2 audio (20) FEC (10)

HV3 audio (30)

DV audio (10) header (1) payload (0-9) 2/3 FEC CRC (2)

(bytes)


ACL Payload types

payload (0-343)

header (1/2) payload (0-339) CRC (2)

DM1 header (1) payload (0-17) 2/3 FEC CRC (2)

DH1 header (1) payload (0-27) CRC (2) (bytes)


DH3 header (2) payload (0-183) CRC (2)


DH5 header (2) payload (0-339) CRC (2)

AUX1 header (1) payload (0-29)


Baseband data rates
Payload User Symmetric Asymmetric
Header Payload max. Rate max. Rate [kbit/s]
ACL Type [byte] [byte] FEC CRC [kbit/s] Forward Reverse
DM1 1 0-17 2/3 yes 108.8 108.8 108.8
1 slot
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
3 slot
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
5 slot
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
SCO
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


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
SCO ACL SCO ACL SCO ACL SCO ACL
MASTER f0 f4 f6 f8 f12 f14 f18 f20

SLAVE 1
f1 f7 f9 f13 f19

SLAVE 2
f5 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 NAK ACK

MASTER A C C F H

SLAVE 1 B D E

SLAVE 2 G G


Baseband states of a Bluetooth device

standby unconnected

detach inquiry page connecting

transmit connected active
AMA AMA

park hold sniff low power
PMA AMA AMA

Standby: do nothing Park: release AMA, get PMA
Inquire: search for other devices Sniff: listen periodically, not each slot
Page: connect to a specific device Hold: stop ACL, SCO still possible, possibly
Connected: participate in a piconet participate in another piconet


Example: Power consumption/CSR BlueCore2
Typical Average Current Consumption (1)
VDD=1.8V Temperature = 20°C
Mode
SCO connection HV3 (1s interval Sniff Mode) (Slave) 26.0 mA
SCO connection HV3 (1s interval Sniff Mode) (Master) 26.0 mA
SCO connection HV1 (Slave) 53.0 mA
SCO connection HV1 (Master) 53.0 mA
ACL data transfer 115.2kbps UART (Master) 15.5 mA
ACL data transfer 720kbps USB (Slave) 53.0 mA
ACL data transfer 720kbps USB (Master) 53.0 mA
ACL connection, Sniff Mode 40ms interval, 38.4kbps UART 4.0 mA
ACL connection, Sniff Mode 1.28s interval, 38.4kbps UART 0.5 mA
Parked Slave, 1.28s beacon interval, 38.4kbps UART 0.6 mA
Standby Mode (Connected to host, no RF activity) 47.0 µA
Deep Sleep Mode(2) 20.0 µA
Notes:
(1) Current consumption is the sum of both BC212015A and the flash.
(2) Current consumption is for the BC212015A device only.
(More: www.csr.com )


Example: Bluetooth/USB adapter (2002: 50€)


L2CAP - Logical Link Control and Adaptation Protocol

Simple data link protocol on top of baseband

Connection oriented, connectionless, and signalling 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


L2CAP logical channels

Slave Master Slave

L2CAP L2CAP L2CAP
2 d 1 1 d d d d 1 1 d d 2
baseband baseband baseband

signalling ACL connectionless connection-oriented


L2CAP packet formats

Connectionless PDU
2 2 ≥2 0-65533 bytes
length CID=2 PSM payload

Connection-oriented PDU
2 2 0-65535 bytes
length CID payload

Signalling command PDU
2 2 bytes
length CID=1 One or more commands

1 1 2 ≥0
code ID length data


Security
User input (initialization)
PIN (1-16 byte) Pairing PIN (1-16 byte)

Authentication key generation
E2 E2
(possibly permanent storage)

link key (128 bit) Authentication link key (128 bit)

Encryption key generation
E3 E3
(temporary storage)

encryption key (128 bit) Encryption encryption key (128 bit)

Keystream generator Keystream generator

payload key Ciphering payload key
Cipher data
Data Data


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)


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


Profiles

Represent default solutions for a certain usage model Applications
 Vertical slice through the protocol stack
 Basis for interoperability

Generic Access Profile
Service Discovery Application Profile

s oc o o P
Cordless Telephony Profile

t r
Intercom Profile

l
Serial Port Profile Profiles
Headset Profile Additional Profiles
Dial-up Networking Profile Advanced Audio Distribution
Fax Profile PAN
Audio Video Remote Control
LAN Access Profile
Basic Printing
Generic Object Exchange Profile
Basic Imaging
Object Push Profile Extended Service Discovery
File Transfer Profile Generic Audio Video Distribution
Synchronization Profile Hands Free
Hardcopy Cable Replacement


WPAN: IEEE 802.15-1 – Bluetooth

 Synchronous, connection-oriented:  Depends on power-mode
64 kbit/s  Max. 2.56s, avg. 0.64s
 Asynchronous, connectionless Quality of Service
 433.9 kbit/s symmetric  Guarantees, ARQ/FEC
 723.2 / 57.6 kbit/s asymmetric
Manageability
Transmission range  Public/private keys needed, key
 POS (Personal Operating Space) management not specified, simple
up to 10 m system integration
 with special transceivers up to 100 Special Advantages/Disadvantages
m  Advantage: already integrated into
Frequency several products, available worldwide,
 Free 2.4 GHz ISM-band free ISM-band, several vendors, simple
system, simple ad-hoc networking, peer
Security to peer, scatternets
 Challenge/response (SAFER+),  Disadvantage: interference on ISM-band,
hopping sequence limited range, max. 8
Availability devices/network&master, high set-up
latency
 Integrated into many products,
several vendors


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 low-
power/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



Several working groups extend the 802.15.3 standard

802.15.3a:
 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 …



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


ZigBee

Relation to 802.15.4 similar to Bluetooth / 802.15.1

Pushed by Chipcon, ember, freescale (Motorola), Honeywell, Mitsubishi,
Motorola, Philips, Samsung

More than 150 members
 Promoter (40000$/Jahr), Participant (9500$/Jahr), Adopter (3500$/Jahr)

No free access to the specifications (only promoters and participants)

ZigBee platforms comprise
 IEEE 802.15.4 for layers 1 and 2
 ZigBee protocol stack up to the applications


Several working groups extend the 802.15.4 standard

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:
 Extensions, corrections, and clarifications regarding 802.15.4
 Usage of new bands, more flexible security mechanisms

802.15.5: Mesh Networking
 Partial meshes, full meshes
 Range extension, more robustness, longer battery live

Not all these working groups really create a standard, not all standards will be
found in products later …


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
 Unclear relation to 802.20, 802.16 started as fixed system…
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

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


WLAN: Home RF – yet another standard, no success

 0.8, 1.6, 5, 10 Mbit/s  10 ms bounded latency
Transmission range Quality of Service
 300m outdoor, 30m indoor  Up to 8 streams A/V, up to 8 voice
Frequency streams, priorities, best-effort
 2.4 GHz ISM Manageability
Security
 Like DECT & 802-LANs
 Strong encryption, no open access Special Advantages/Disadvantages
Cost  Advantage: extended QoS support,
host/client and peer/peer, power
 Adapter 130€, base station 230€
saving, security
Availability  Disadvantage: future uncertain due
 Several products from different to DECT-only devices plus
vendors, no more support 802.11a/b for data


RF Controllers – ISM bands

 Typ. up to 115 kbit/s (serial  N/A
interface)
Quality of Service
Transmission range
 none
 5-100 m, depending on power (typ.
10-500 mW) Manageability
Frequency  Very simple, same as serial
 Typ. 27 (EU, US), 315 (US), 418 interface
(EU), 426 (Japan), 433 (EU), 868 Special Advantages/Disadvantages
(EU), 915 (US) MHz (depending on
regulations)  Advantage: very low cost, large
experience, high volume available
Security
 Disadvantage: no QoS, crowded
 Some products with added
processors ISM bands (particularly 27 and 433
MHz), typ. no Medium Access
Cost Control, 418 MHz experiences
 Cheap: 10€-50€ interference with TETRA
Availability


RFID – Radio Frequency Identification (1)
 Transmission of ID only (e.g., 48 bit,  Depends on product/medium access
64kbit, 1 Mbit) scheme (typ. 2 ms per device)
 9.6 – 115 kbit/s
Quality of Service
Transmission range  none
 Passive: up to 3 m
 Active: up to 30-100 m Manageability
 Simultaneous detection of up to, e.g.,  Very simple, same as serial interface
256 tags, scanning of, e.g., 40 tags/s Special Advantages/Disadvantages
Frequency  Advantage: extremely low cost, large
 125 kHz, 13.56 MHz, 433 MHz, 2.4 GHz, experience, high volume available, no
5.8 GHz and many others power for passive RFIDs needed, large
Security variety of products, relative speeds up to
 Application dependent, typ. no crypt. on 300 km/h, broad temp. range
RFID device  Disadvantage: no QoS, simple denial of
Cost service, crowded ISM bands, typ. one-
 Very cheap tags, down to 1€ (passive) way (activation/ transmission of ID)
Availability



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



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



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



Devices and Companies
 AXCESS Inc., www.axcessinc.com
 Checkpoint Systems Group, www.checkpointsystems.com
 GEMPLUS, www.gemplus.com/app/smart_tracking
 Intermec/Intellitag, www.intermec.com
 I-Ray Technologies, www.i-ray.com
 RF Code, www.rfcode.com
 Texas Instruments, www.ti-rfid.com/id
 WhereNet, www.wherenet.com
 Wireless Mountain, www.wirelessmountain.com
 XCI, www.xci-inc.com

Only a very small selection…



Example Product: Intermec RFID UHF OEM Reader
 Read range up to 7m
 Anticollision algorithm allows for scanning of 40 tags per second regardless
of the number of tags within the reading zone
 US: unlicensed 915 MHz, Frequency Hopping
 Read: 8 byte < 32 ms
 Write: 1 byte < 100ms

Example Product: Wireless Mountain Spider
 Proprietary sparse code anti-collision algorithm
 Detection range 15 m indoor, 100 m line-of-sight
 > 1 billion distinct codes
 Read rate > 75 tags/s
 Operates at 308 MHz



Relevant Standards
 American National Standards Institute
 ANSI, www.ansi.org, www.aimglobal.org/standards/rfidstds/ANSIT6.html
 Automatic Identification and Data Capture Techniques
 JTC 1/SC 31, www.uc-council.com/sc31/home.htm,
www.aimglobal.org/standards/rfidstds/sc31.htm
 European Radiocommunications Office
 ERO, www.ero.dk, www.aimglobal.org/standards/rfidstds/ERO.htm
 European Telecommunications Standards Institute
 ETSI, www.etsi.org, www.aimglobal.org/standards/rfidstds/ETSI.htm
 Identification Cards and related devices
 JTC 1/SC 17, www.sc17.com, www.aimglobal.org/standards/rfidstds/sc17.htm,
 Identification and communication
 ISO TC 104 / SC 4, www.autoid.org/tc104_sc4_wg2.htm,
www.aimglobal.org/standards/rfidstds/TC104.htm
 Road Transport and Traffic Telematics
 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



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


ISM band interference

Many sources of interference OLD
 Microwave ovens, microwave lightning
 802.11, 802.11b, 802.11g, 802.15, Home RF
 Even analog TV transmission, surveillance
NEW
 Unlicensed metropolitan area networks
 …

Levels of interference
 Physical layer: interference acts like noise
 Spread spectrum tries to minimize this
 FEC/interleaving tries to correct
 MAC layer: algorithms not harmonized © Fusion Lighting, Inc.
 E.g., Bluetooth might confuse 802.11


802.11 vs.(?) 802.15/Bluetooth

Bluetooth may act like a rogue member of the 802.11 network
f [MHz]
 Does not know anything about gaps, inter frame spacing etc.
2480 802.11b
3 channels

SIFS
DIFS

DIFS
1000 byte
(separated by

DIFSK CA
installation)
DIFS

SIFS

DIFS

SIFS
500 byte 500 byte 500 byte
DIFSK CA 802.15.1

DIFSK CA
79 channels
DIFS

SIFS

SIFS

DIFS

SIFS

SIFS

DIFS

SIFS
100 100 100 100 100
byte byte byte byte byte (separated by
K CA
K CA

K CA

K CA

K CA
2402 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)


C07 wireless la-ns

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