Download - EEE 464 Wireless Communications Lecture 9
Wireless Data Networks
This lecture discusses wireless LANs, IEEE Wireless PANs (Bluetooth) and Wireless
MANs
Shahzad Malik Lecture 9 3Wireless Communications – Wireless Data
WiFi - IEEE 802.11
Bluetooth - IEEE 802.15
WiMax - IEEE 802.16
Mobile IP
MANETs (Routing)
Integration (Cellular + WLAN)
Organization of LectureOrganization of Lecture
Shahzad Malik Lecture 9 4Wireless Communications – Wireless Data
Wireless LANs: Characteristics
Advantages Flexible deployment; Minimal wiring problems
More robust against disasters
Historic buildings, conferences, …
Disadvantages Low bandwidth compared to wired networks
Need to follow wireless spectrum regulations
Shahzad Malik Lecture 9 5Wireless Communications – Wireless Data
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
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 WiFi, HIPERLAN, Bluetooth
Shahzad Malik Lecture 9 6Wireless Communications – Wireless Data
infrastructure vs. ad-hoc networks
infrastructure network
ad-hoc network
APAP
AP
wired network
AP: Access Point
IEEE 802.11 (WiFi)
Shahzad Malik Lecture 9 8Wireless Communications – Wireless Data
IEEE 802.11 Wireless LAN
802.11/802.11b2.4-5 GHz unlicensed
radio spectrumup to 11 Mbpsdirect sequence
spread spectrum (DSSS) in physical layer
all hosts use same chipping code
widely deployed, using base stations
802.11a 5-6 GHz rangeup to 54 Mbps
802.11g 2.4-5 GHz rangeup to 54 Mbps
All use CSMA/CA for multiple access
All have base-station and ad-hoc network versions
Shahzad Malik Lecture 9 9Wireless Communications – Wireless Data
802.11 - Architecture of an infrastructure network
Station (STA) terminal with access
mechanisms to the wireless medium and radio contact to the access point
Basic Service Set (BSS) group of stations using the
same radio frequencyAccess Point
station integrated into the wireless LAN and the distribution system
Portal bridge to other (wired)
networksDistribution System
interconnection network to form one logical network (EES: Extended Service Set) based on several BSS
Distribution System
Portal
802.x LAN
Access Point
802.11 LAN
BSS2
802.11 LAN
BSS1
Access Point
STA1
STA2 STA3
ESS
Shahzad Malik Lecture 9 10Wireless Communications – Wireless Data
802.11 - Architecture of an ad-hoc network
Direct communication within a limited range
Station (STA):terminal with access mechanisms to the wireless medium
Independent Basic Service Set (IBSS):group of stations using the same radio frequency
802.11 LAN
IBSS2
802.11 LAN
IBSS1
STA1
STA4
STA5
STA2
STA3
Shahzad Malik Lecture 9 11Wireless Communications – Wireless Data
IEEE standard 802.11
mobile terminal
access point
fixedterminal
application
TCP
802.11 PHY
802.11 MAC
IP
802.3 MAC
802.3 PHY
application
TCP
802.3 PHY
802.3 MAC
IP
802.11 MAC
802.11 PHY
LLC
infrastructurenetwork
LLC LLC
Shahzad Malik Lecture 9 12Wireless Communications – Wireless Data
802.11: Channels, association
802.11: 2.4GHz-2.485GHz spectrum divided into 11 channels at
different frequencies
AP admin chooses frequency for AP
interference possible: channel can be same as that
chosen by neighboring AP!
host: must associate with an APscans channels, listening for beacon frames containing
AP’s name (SSID) and MAC address
selects AP to associate with
may perform authentication
will typically run DHCP to get IP address in AP’s subnet
Shahzad Malik Lecture 9 13Wireless Communications – Wireless Data
802.11 - Layers and functions
PLCP Physical Layer Convergence Protocol
clear channel assessment signal (carrier sense)
PMD Physical Medium Dependent
modulation, coding PHY Management
channel selection, MIB Station Management
coordination of all management functions
PMD
PLCP
MAC
LLC
MAC Management
PHY Management
MACaccess mechanisms,
fragmentation, encryption MAC Management
synchronization, roaming, MIB, power management
PH
YD
LC
Sta
tion
Man
agem
ent
Shahzad Malik Lecture 9 14Wireless Communications – Wireless Data
802.11 - Physical layer
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, synchonization
Shahzad Malik Lecture 9 15Wireless Communications – Wireless Data
802.11 - MAC layer
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 DCF CSMA/CA (mandatory)
collision avoidance via randomized „back-off“ mechanism
minimum distance between consecutive packets ACK packet for acknowledgements (not for broadcasts)
DCF w/ RTS/CTS (optional) Distributed Foundation Wireless MAC avoids hidden terminal problem
PCF (optional) access point polls terminals according to a list
Shahzad Malik Lecture 9 16Wireless Communications – Wireless Data
802.11 - MAC layer
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
t
medium busySIFS
PIFS
DIFSDIFS
next framecontention
direct access if medium is free DIFS
Shahzad Malik Lecture 9 17Wireless Communications – Wireless Data
802.11 - CSMA/CA access method
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
t
SIFS
DIFS
data
ACK
waiting time
otherstations
receiver
senderdata
DIFS
contention
Shahzad Malik Lecture 9 18Wireless Communications – Wireless Data
802.11 – RTS/CTSSending 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 ACKother stations store medium reservations distributed via RTS
and CTS
t
SIFS
DIFS
data
ACK
defer access
otherstations
receiver
senderdata
DIFS
contention
RTS
CTSSIFS SIFS
NAV (RTS)NAV (CTS)
Shahzad Malik Lecture 9 19Wireless Communications – Wireless Data
PCF - Point Coordination Function
PIFS
stations‘NAV
wirelessstations
point coordinator
D1
U1
SIFS
NAV
SIFSD2
U2
SIFS
SIFS
SuperFramet0
medium busy
t1
Shahzad Malik Lecture 9 20Wireless Communications – Wireless Data
802.11 - RoamingNo 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 Requeststation sends a request to one or several AP(s)
Reassociation Responsesuccess: AP has answered, station can now participatefailure: continue scanning
AP accepts Reassociation Requestsignal the new station to the distribution systemthe distribution system updates its data base (i.e.,
location information)typically, the distribution system now informs the old
AP so it can release resources
Shahzad Malik Lecture 9 21Wireless Communications – Wireless Data
WLAN: IEEE 802.11bData rate
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 Free 2.4 GHz ISM-band
Security Limited, WEP insecure, SSID
Cost 100€ adapter, 250€ base
station, droppingAvailability
Many products, many vendors
Connection set-up time 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
Shahzad Malik Lecture 9 22Wireless Communications – Wireless Data
WLAN: IEEE 802.11aData rate
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 mandatoryTransmission range
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
Frequency Free 5.15-5.25, 5.25-5.35,
5.725-5.825 GHz ISM-bandSecurity
Limited, WEP insecure, SSIDCost
280€ adapter, 500€ base station
Availability Some products, some vendors
Connection set-up time Connectionless/always on
Quality of Service Typ. best effort, no
guarantees (same as all 802.11 products)
Manageability Limited (no automated key
distribution, sym. Encryption)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
Shahzad Malik Lecture 9 23Wireless Communications – Wireless Data
WLAN: IEEE 802.11 – future developments
802.11e: MAC Enhancements – QoSEnhance the current 802.11 MAC to expand support for
applications with Quality of Service requirements, and in the capabilities and efficiency of the protocol.
802.11f: Inter-Access Point ProtocolEstablish an Inter-Access Point Protocol for data exchange
via the distribution system.802.11n: Data Rates > 100 Mbit/s, OFDM , MIMO802.11h: Spectrum Managed 802.11a (DCS, TPC)802.11i: Enhanced Security Mechanisms
Enhance the current 802.11 MAC to provide improvements in security.
Study Groups5 GHz (harmonization ETSI/IEEE) Radio Resource MeasurementsHigh Throughput
Shahzad Malik Lecture 9 24Wireless Communications – Wireless Data
ETSI - HIPERLAN 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!
physical layer
channel accesscontrol layer
medium access control layer
physical layer
data link layer
HIPERLAN layers OSI layers
network layer
higher layers
physical layer
medium accesscontrol layer
logical link control layer
IEEE 802.x layers
Bluetooth(IEEE 802.15)
Shahzad Malik Lecture 9 26Wireless Communications – Wireless Data
BluetoothIdea
Universal radio interface for ad-hoc wireless connectivity Interconnecting computer and peripherals, handheld devices,
PDAs, cell phones – replacement of IrDAEmbedded in other devices, goal: 5€/device (2002: 50€/USB
bluetooth)Short range (10 m), low power consumption, license-free 2.45
GHz ISMVoice and data transmission, approx. 1 Mbit/s gross data rate
One of the first modules (Ericsson).
Shahzad Malik Lecture 9 27Wireless Communications – Wireless Data
Bluetooth Characteristics
2.4 GHz ISM band, 79 (23) RF channels, 1 MHz carrier spacingChannel 0: 2402 MHz … channel 78: 2480 MHzG-FSK modulation, 1-100 mW transmit power
FHSS and TDDFrequency hopping with 1600 hops/sHopping sequence in a pseudo random fashion,
determined by a masterTime 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
TopologyOverlapping piconets (stars) forming a scatternet
Shahzad Malik Lecture 9 28Wireless Communications – Wireless Data
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
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)
M=MasterS=Slave
P=ParkedSB=Standby
M
S
P
SB
S
S
P
P
SB
Shahzad Malik Lecture 9 29Wireless Communications – Wireless Data
Forming a piconetAll 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
AddressingActive Member Address (AMA, 3 bit)Parked Member Address (PMA, 8 bit)
SB
SB
SB
SB
SB
SB
SB
SB
SB
M
S
P
SB
S
S
P
P
SB
Shahzad Malik Lecture 9 30Wireless Communications – Wireless Data
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 anotherCommunication between piconets
Devices jumping back and forth between the piconets
M=MasterS=SlaveP=ParkedSB=Standby
M
S
P
SB
S
S
P
P
SB
M
S
S
P
SB
Piconets(each with a capacity of < 1 Mbit/s)
Shahzad Malik Lecture 9 31Wireless Communications – Wireless Data
Bluetooth protocol stack
Radio
Baseband
Link Manager
Control
HostControllerInterface
Logical Link Control and Adaptation Protocol (L2CAP)Audio
TCS BIN SDP
OBEX
vCal/vCard
IP
NW apps.
TCP/UDP
BNEP
RFCOMM (serial line interface)
AT modemcommands
telephony apps.audio apps. mgmnt. apps.
AT: attention sequenceOBEX: object exchangeTCS BIN: telephony control protocol specification – binaryBNEP: Bluetooth network encapsulation protocol
SDP: service discovery protocolRFCOMM: radio frequency comm.
PPP
Shahzad Malik Lecture 9 32Wireless Communications – Wireless Data
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
f6f0
f1 f7
f12
f13 f19
f18
SCO SCO SCO SCOACL
f5 f21
f4 f20
ACLACLf8
f9
f17
f14
ACL
Shahzad Malik Lecture 9 33Wireless Communications – Wireless Data
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
Shahzad Malik Lecture 9 34Wireless Communications – Wireless Data
Additional protocols
Service Discovery Protocol (SDP)
Inquiry/response protocol for discovering services
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
Shahzad Malik Lecture 9 35Wireless Communications – Wireless Data
Profiles
Represent default solutions for a certain usage model Vertical slice through the protocol stack Basis for interoperability
Generic Access ProfileService Discovery Application ProfileCordless Telephony Profile Intercom ProfileSerial Port ProfileHeadset ProfileDial-up Networking ProfileFax ProfileLAN Access ProfileGeneric Object Exchange ProfileObject Push ProfileFile Transfer ProfileSynchronization Profile
Additional ProfilesAdvanced Audio DistributionPANAudio Video Remote ControlBasic PrintingBasic ImagingExtended Service DiscoveryGeneric Audio Video DistributionHands FreeHardcopy Cable Replacement
Profiles
Pro
toco
ls
Applications
Shahzad Malik Lecture 9 36Wireless Communications – Wireless Data
WPAN: IEEE 802.15-1Data rate
Synchronous, connection-oriented: 64 kbit/s
Asynchronous, connectionless
433.9 kbit/s symmetric 723.2 / 57.6 kbit/s
asymmetricTransmission 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 sequenceCost
50€ adapter, drop to 5€ if integrated
Availability Integrated into some
products, several vendors
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 ad-hoc networking, peer to peer, scatternets
Disadvantage: interference on ISM-band, limited range, max. 8 devices/network&master, high set-up latency
Shahzad Malik Lecture 9 37Wireless Communications – Wireless Data
WPAN: IEEE 802.15 – future developments
802.15-2: CoexistanceCoexistence of Wireless Personal Area Networks
(802.15) and Wireless Local Area Networks (802.11), quantify the mutual interference
802.15-3: High-RateStandard 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
Shahzad Malik Lecture 9 38Wireless Communications – Wireless Data
WPAN: IEEE 802.15 – future developments
802.15-4: Low-Rate, Very Low-PowerLow data rate solution with multi-month to multi-year
battery life and very low complexityPotential 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 operationSupport for critical latency devices, such as joysticks CSMA/CA channel access (data centric), slotted (beacon) or
unslottedAutomatic network establishment by the PAN coordinator Dynamic device addressing, flexible addressing formatFully 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
IEEE 802.16 (WiMax)
Fixed Broadband Wireless Access StandardFixed Broadband Wireless Access Standard
Shahzad Malik Lecture 9 40Wireless Communications – Wireless Data
IEEE 802.16
The standard IEEE 802.16 defines the air interface,
including the MAC layer and multiple PHY layer options,
for fixed Broadband Wireless Access (BWA) systems to
be used in a Wireless Metropolitan Area Network
(WMAN) for residential and enterprise use. IEEE 802.16
is also often referred to as WiMax. The WiMax Forum
strives to ensure interoperability between different
802.16 implementations - a difficult task due to the
large number of options in the standard.
IEEE 802.16 cannot be used in a mobile environment.
For this purpose, IEEE 802.16e has been developed.
Shahzad Malik Lecture 9 41Wireless Communications – Wireless Data
What is 802.16
Commonly referred to as WiMAX or less commonly as WirelessMAN™ or the Air Interface Standard, IEEE 802.16 is a specification for fixed broadband wireless metropolitan access networks (MANs) just like wireless local loop (WLL) that use a point-to-multipoint architecture.
Published on April 8, 2002, the standard defines the use of bandwidth between the licensed 10GHz and 66GHz and between the 2GHZ and 11GHz (licensed and unlicensed) frequency ranges and defines a MAC layer that supports multiple physical layer specifications customized for the frequency band of use and their associated regulations.
802.16 supports very high bit rates in both uploading to and downloading from a base station up to a distance of 30 miles to handle such services as VoIP, IP connectivity and TDM voice and data.
Shahzad Malik Lecture 9 42Wireless Communications – Wireless Data
Properties of IEEE Standard 802.16
Broad bandwidth Up to 134 Mbit/s in 28 MHz channel (in 10-66 GHz air interface) Supports multiple services simultaneously with full QoS Efficiently transport IPv4, IPv6, ATM, Ethernet, etc. Bandwidth on demand (frame by frame) MAC designed for efficient used of spectrum Comprehensive, modern, and extensible security Supports multiple frequency allocations from 2-66 GHz ODFM and OFDMA for non-line-of-sight applications TDD and FDD Link adaptation: Adaptive modulation and coding Subscriber by subscriber, burst by burst, uplink and downlink Point-to-multipoint topology, with mesh extensions Support for adaptive antennas and space-time coding Extensions to mobility are coming next.
Shahzad Malik Lecture 9 43Wireless Communications – Wireless Data
Different versions of 802.16
802.16a 802.16a, approved in January 2003, specified non-line-of-sight
extensions in the 2-11 GHz spectrum, delivering up to 70 Mbps at distances up to 31 miles.
802.16 Revd Consolidates revisions of 802.16a and 802.16c into a single
standard that will replace 802.16a as the base standard. 802.16-2004
The IEEE 802.16-2004 standard subsequently revised and replaced the IEEE 802.16a and 802.16REVd versions. This is designed for fixed-access usage models. This standard may be referred to as "fixed wireless" because it uses a mounted antenna at the subscriber's site. The antenna is mounted to a roof or mast, similar to a satellite television dish.
802.16e 802.16e will add mobility in the 2 to 6 GHz licensed bands,
while 802.20 aims for operation in licensed bands below 3.5GHz.
Shahzad Malik Lecture 9 44Wireless Communications – Wireless Data
Comparisons of Different Versions of 802.16
Shahzad Malik Lecture 9 45Wireless Communications – Wireless Data
Working of 802.16
• Wireless broadband access is set up like cellular systems, using base stations that service a radius of several miles/kilometers.
• A customer premise unit, similar to a satellite TV setup, is all it takes to connect the base station to a customer.
• The signal is then routed via standard Ethernet cable either directly to a single computer, or to an 802.11 hot spot or a wired Ethernet LAN.
Shahzad Malik Lecture 9 46Wireless Communications – Wireless Data
IEEE 802.16 basic architecture
BS SS
SS
SS
Point-to-multipoint transmission
AP
AP
802.11 WLANBS = Base Station
SS = Subscriber Station
Fixed network
Subscriber line replacement
Shahzad Malik Lecture 9 47Wireless Communications – Wireless Data
Uplink / downlink separation
IEEE 802.16 offers both TDD (Time Division Duplexing) and FDD (Frequency Division
Duplexing) alternatives.
Wireless devices should avoid transmitting and receiving at the same time, since duplex filters
increase the cost:
TDD: this problem is automatically avoided
FDD: IEEE 802.16 offers semi-duplex operation as an option in Subscriber Stations.
Shahzad Malik Lecture 9 48Wireless Communications – Wireless Data
Uplink / downlink separation
TDDTDD
FDDFDD
Semi-duplex
FDD
Semi-duplex
FDD
DownlinkDownlink
UplinkUplink
… …
Adaptive
Frequency 1
Frequency 2
…
…
…
…
…
…
…
…
Frame n-1 Frame n Frame n+1
Shahzad Malik Lecture 9 49Wireless Communications – Wireless Data
WiMAX
The WiMax (Worldwide Interoperability for Microwave Access)
certification program of the WiMax Forum addresses
compatibility of IEEE 802.16 equipment
=>
WiMax ensures interoperability of
equipment from different vendors.
ATMtransport
ATMtransport
IPtransport
IPtransport
Service Specific ConvergenceSublayer (CS)
Service Specific ConvergenceSublayer (CS)
MAC Common Part Sublayer(MAC CPS)
MAC Common Part Sublayer(MAC CPS)
Privacy sublayerPrivacy sublayer
Physical Layer (PHY)Physical Layer (PHY)
WiMax
Shahzad Malik Lecture 9 50Wireless Communications – Wireless Data
IEEE 802.16 PHY
IEEE 802.16-2004 specifies three PHY options for the 2-11 GHz band, all supporting both TDD and FDD:
WirelessMAN-SCa (single carrier option), intended for a line-of-sight (LOS) radio environment where multipath
propagation is not a problem
WirelessMAN-OFDM with 256 subcarriers (mandatory for license-exempt bands) will be the most popular option
in the near future
WirelessMAN-OFDMA with 2048 subcarriers separates users in the uplink in frequency domain (complex
technology).
Shahzad Malik Lecture 9 51Wireless Communications – Wireless Data
WirelessMAN-OFDM PHY
WirelessMAN-OFDM is based on 256 subcarriers, of which 200 subcarriers are used: 192 data subcarriers + 8 pilot subcarriers. There are 56 ”nulls” (center carrier,
28 lower frequency and 27 higher frequency guard carriers).
Shahzad Malik Lecture 9 52Wireless Communications – Wireless Data
Modulation and coding affect user data rate
The 192 data subcarriers carry 192 data symbols in parallel (= transmitted at the same time). Each symbol carries 1 bit (BPSK), 2 bits (QPSK), 4 bits (16-QAM), or 6 bits (64-QAM) of channel information (corresponding to
the channel bit rate after channel coding, not to be confused with the user bit rate before channel coding).
The inner convolutional coding reduces the usable number of bits to 1/2, 2/3, or 3/4 of the channel
information.
The outer Reed-Solomon block coding furthermore reduces the usable number of bits about 10 %.
Shahzad Malik Lecture 9 53Wireless Communications – Wireless Data
Subcarrier signal in time domain (1)
Time
Guard time for preventing intersymbol interference
In the receiver, FFT is calculated only during this time
Next symbol
TbTg
IEEE 802.16 offers four values for G = Tg/Tb: G = 1/4, 1/8, 1/16 or 1/32. (802.11a/g offers only one value: G = 1/4)
Ts
Shahzad Malik Lecture 9 54Wireless Communications – Wireless Data
Subcarrier signal in time domain (2)
IEEE 802.16 offers various bandwidth choices. The bandwidth is typically an integer multiple of 1.25, 1.5 or
1.75 MHz. (802.11a/g offers only a fixed channel bandwidth: 16.25 MHz)
Since the number of subcarriers is fixed, a certain bandwidth is translated into a certain subcarrier spacing
f = 1/Tb.
Time
Next symbol
TbTg
Shahzad Malik Lecture 9 55Wireless Communications – Wireless Data
Four primitive parameters
WirelessMAN-OFDM defines four "primitive parameters" that characterize the OFDM symbol:
The nominal channel bandwidth BW
The number of used subcarriers Nused = 200
The sampling factor n. This parameter depends on the bandwidth. For instance, when the bandwith is a
multiple of 1.25, 1.5 or 1.75 MHz, n = 144/125, 86/75 or 8/7, respectively.
The guard time to useful symbol time ratio G.
Shahzad Malik Lecture 9 56Wireless Communications – Wireless Data
Derived parameters
Using the four primitive parameters shown on the previous slide, the following additional parameters can
be derived:
NFFT (the smallest power of two greater than Nused) = 256
Sampling frequency fs = floor(n.BW/8000)x8000
Subcarrier spacing f = fs/NFFT
Useful symbol time Tb = 1/f
Guard time Tg = G.Tb
OFDM symbol time Ts = Tg + Tb.
Shahzad Malik Lecture 9 57Wireless Communications – Wireless Data
Example
For BW = 5 MHz, BPSK, G = 1/32, calculate peak bit rate:
fs = floor(144/125 x 5 MHz / 8000) x 8000 = 5.76 MHz
f = fs/NFFT = 5.76 MHz / 256 = 22.5 kHz
Tb = 1/f = 44.44 s
Tg = G.Tb = 1.39 s
Ts = Tg + Tb = 45.83 s
Peak bit rate = (192 bits x 0.5 x 0.9) / 45.83 s = 1.89 Mb/s
86.4 info bits / OFDM symbol
Shahzad Malik Lecture 9 58Wireless Communications – Wireless Data
Modulation
BPSKQPSKQPSK
16-QAM16-QAM64-QAM64-QAM
Info bits / subcarrier
0.51
1.5234
4.5
Info bits /symbol
88184280376568760856
Peak data rate (Mbit/s)
1.893.956.008.0612.1816.3018.36
Coding rate
1/21/23/41/23/42/33/4
Depends on chosen bandwidth (here 5 MHz is assumed)
Modulation and coding combinations
Shahzad Malik Lecture 9 59Wireless Communications – Wireless Data
Example (cont.)
The peak bit rate does not take into account the MAC layer overhead (MAC PDU header and trailer) and PHY layer overhead (contention slots and burst preamble in
UL, DL PHY PDU preamble and header in DL).
Consequently, the user data rate is substantially smaller (even if the SS is the only user of the WMAN).
Shahzad Malik Lecture 9 60Wireless Communications – Wireless Data
ATMtransport
ATMtransport
IPtransport
IPtransport
Service Specific ConvergenceSublayer (CS)
Service Specific ConvergenceSublayer (CS)
IEEE 802.16 protocol layering
MAC Common Part Sublayer(MAC CPS)
MAC Common Part Sublayer(MAC CPS)
Privacy sublayerPrivacy sublayer
Physical Layer (PHY)Physical Layer (PHY)
MA
C
Like IEEE 802.11, IEEE 802.16 specifies the
Medium Access Control (MAC) and PHY layers of the wireless transmission system.
The IEEE 802.16 MAC layer consists of three
sublayers.
Shahzad Malik Lecture 9 61Wireless Communications – Wireless Data
ATMtransport
ATMtransport
IPtransport
IPtransport
Service Specific ConvergenceSublayer (CS)
Service Specific ConvergenceSublayer (CS)
IEEE 802.16 protocol layering
MAC Common Part Sublayer(MAC CPS)
MAC Common Part Sublayer(MAC CPS)
Privacy sublayerPrivacy sublayer
Physical Layer (PHY)Physical Layer (PHY)
MA
C
CS maps data (ATM cells or IP packets) to
a certain unidirectional
connection identified by the Connection Identifier (CID) and associated with a
certain QoS.
CS adapts higher layer protocols to MAC CPS.
May also offer payload header suppression.
Shahzad Malik Lecture 9 62Wireless Communications – Wireless Data
ATMtransport
ATMtransport
IPtransport
IPtransport
Service Specific ConvergenceSublayer (CS)
Service Specific ConvergenceSublayer (CS)
IEEE 802.16 protocol layering
MAC Common Part Sublayer(MAC CPS)
MAC Common Part Sublayer(MAC CPS)
Privacy sublayerPrivacy sublayer
Physical Layer (PHY)Physical Layer (PHY)
MA
C
MAC CPS provides the core MAC
functionality:
• System access
• Bandwidth allocation
• Connection controlNote: QoS control is applied dynamically to every connection
individually.
Shahzad Malik Lecture 9 63Wireless Communications – Wireless Data
ATMtransport
ATMtransport
IPtransport
IPtransport
Service Specific ConvergenceSublayer (CS)
Service Specific ConvergenceSublayer (CS)
IEEE 802.16 protocol layering
MAC Common Part Sublayer(MAC CPS)
MAC Common Part Sublayer(MAC CPS)
Privacy sublayerPrivacy sublayer
Physical Layer (PHY)Physical Layer (PHY)
MA
C
The privacy sublayer provides
authentication, key management and
encryption.
Shahzad Malik Lecture 9 64Wireless Communications – Wireless Data
ATMtransport
ATMtransport
IPtransport
IPtransport
Service Specific ConvergenceSublayer (CS)
Service Specific ConvergenceSublayer (CS)
IEEE 802.16 protocol layering
MAC Common Part Sublayer(MAC CPS)
MAC Common Part Sublayer(MAC CPS)
Privacy sublayerPrivacy sublayer
Physical Layer (PHY)Physical Layer (PHY)
MA
C IEEE 802.16 offers three PHY options for the 2-11 GHz band:
• WirelessMAN-SCa
• WirelessMAN-OFDM
• WirelessMAN-OFDMA
Shahzad Malik Lecture 9 65Wireless Communications – Wireless Data
Overall TDD frame structure (1)
Frame n-1Frame n-1 Frame nFrame n Frame n+1Frame n+1 Frame n+2Frame n+2
Frame length 0.5, 1 or 2 ms
The following slides present the overall IEEE 802.16 frame structure for TDD.
It is assumed that the PHY option is WirelessMAN-OFDM, since this presumably will be the most popular PHY
option (in the near future). The general frame structure is applicable also to other PHY options, but the details
may be different.
Shahzad Malik Lecture 9 66Wireless Communications – Wireless Data
Overall TDD frame structure (2)
Frame n-1Frame n-1 Frame nFrame n Frame n+1Frame n+1 Frame n+2Frame n+2
DL PHYPDU
DL PHYPDU
Contentionslot A
Contentionslot A
Contentionslot B
Contentionslot B
UL PHYburst 1UL PHYburst 1
UL PHYburst kUL PHYburst k
…
DL subframe UL subframe
TDMA bursts from different subscriber stations (each with its own preamble)
TDM signal in downlink
For initial ranging
For BW requests
Adaptive
Shahzad Malik Lecture 9 67Wireless Communications – Wireless Data
Modulation and coding combinations
Modulation
BPSKQPSKQPSK
16-QAM16-QAM64-QAM64-QAM
Info bits / subcarrier
0.51
1.5234
4.5
Info bits /symbol
88184280376568760856
Peak data rate (Mbit/s)
1.893.956.008.0612.1816.3018.36
Coding rate
1/21/23/41/23/42/33/4
Depends on chosen bandwidth (here 5 MHz is assumed)
Shahzad Malik Lecture 9 68Wireless Communications – Wireless Data
Example: Efficiency vs. Robustness Trade-off
Large distance => high attenuation => low bit rate
BS64 QAM
16 QAM
QPSK
SS
SS
SS
Shahzad Malik Lecture 9 69Wireless Communications – Wireless Data
Four service classes The IEEE 802.16 MAC layer defines four service
classes:
• Unsolicited Grant Service (UGS)• Real-time Polling Service (rtPS)
• Non-real-time Polling Service (nrtPS)• Best Effort (BE) service
The scheduling algorithms needed for implementing the three first types of services are implemented in
the BS (while allocating uplink bandwidth to each SS) and are not defined in the 802.16 standard. Each SS
negotiates its service policies with the BS at the connection setup time.
QoS increasesQoS increases
Dynamic QoS management
Shahzad Malik Lecture 9 70Wireless Communications – Wireless Data
Unsolicited grant service (UGS)
UGS offers fixed size grants on a real-time periodic basis, which eliminates the overhead and latency of SS requests and assures that
grants are available to meet the flow’s real-time needs. The BS provides fixed size bursts in the uplink at periodic intervals for the service flow.
The burst size and other parameters are negotiated at connection setup.
Typical UGS applications: E1/T1 links (containing e.g. delay-sensitive speech signals), VoIP
(without silence suppression).
UGSUGS
rtPSrtPS
nrtPSnrtPS
BEBE
Shahzad Malik Lecture 9 71Wireless Communications – Wireless Data
Real-time Polling Service (rtPS)
The Real-time Polling Service (rtPS) is designed to support real-time service flows that generate variable size data packets on a periodic basis,
such as VoIP (with silence suppression) or streaming video.
This service offers real-time, periodic, unicast request opportunities, which meet the flow’s real-time needs and allow the SS to specify the size of
the desired uplink transmission burst. This service requires more request overhead than
UGS, but supports variable grant sizes for optimum data transport efficiency.
UGSUGS
rtPSrtPS
nrtPSnrtPS
BEBE
Shahzad Malik Lecture 9 72Wireless Communications – Wireless Data
Non-real-time Polling Service (nrtPS)
The Non-real-time Polling Service (nrtPS) is designed to support non-real-time service flows that require variable size bursts in the uplink on
a regular (but not strictly periodic) basis.
Subscriber stations contend for bandwidth (for uplink transmission) during contention request
opportunities. The availability of such opportunities is guaranteed at regular intervals (on the order of one second or less) irrespective
of network load.
UGSUGS
rtPSrtPS
nrtPSnrtPS
BEBE
Shahzad Malik Lecture 9 73Wireless Communications – Wireless Data
Best Effort (BE) service
The Best Effort service is intended to be used for best effort traffic where no throughput or delay
guarantees are provided.
Subscriber stations contend for bandwidth (for uplink transmission) during contention request
opportunities. The availability of such opportunities depends on network load and is
not guaranteed (in contrast to nrtPS).
UGSUGS
rtPSrtPS
nrtPSnrtPS
BEBE
Shahzad Malik Lecture 9 74Wireless Communications – Wireless Data
Dynamic QoS management in practice
The request-response mechanism described on the previous slides is designed to be scalable, efficient, and
self-correcting.
While extensive bandwidth allocation and QoS mechanisms are specified in the IEEE 802.16 standard, the
details of scheduling and reservation management have not been standardized and thus provide an important
mechanism for vendors to differentiate their equipment.
(There is a similar situation regarding standardization of a transmission system in general: the transmitted signal is standardized in detail, whereas receivers can process the
received signal as they like, using innovative technology.)
Shahzad Malik Lecture 9 75Wireless Communications – Wireless Data
Three types of management connections
When a subscriber station accesses the network, three types of management connections are established
between the SS and the BS (before transport connections can be established):
Basic management connection for exchange of short, delay-critical MAC management messages
Primary management connection for exchange of longer, more delay tolerant MAC management
messages
Secondary management connection for exchange of delay tolerant IP-based messages, such as used
during DHCP transactions.
Shahzad Malik Lecture 9 76Wireless Communications – Wireless Data
Summary: Dynamic QoS management
In summary, IEEE 802.16 offers the following mechanisms for dynamically managing QoS and
bandwidth:
In the PHY layer by adjusting the DL and UL burst profiles (modulation and coding combination) on a per-frame
basis.
In the MAC layer through fragmentation and packing (both can be done at the same time).
At higher protocol layers by using scheduling algorithms in the base station. These algorithms are not specified in
the IEEE 802.16 standard.
Mobile IP
Shahzad Malik Lecture 9 78Wireless Communications – Wireless Data
Motivation for Mobile IP
Routing based on IP destination address, network prefix (e.g.
129.13.42) determines physical subnet change of physical subnet implies change of IP address to
have a topological correct address (standard IP) or needs special entries in the routing tables
Specific routes to end-systems? change of all routing table entries to forward packets to the
right destination does not scale with the number of mobile hosts and
frequent changes in the location, security problems Changing the IP-address?
adjust the host IP address depending on the current location almost impossible to find a mobile system, DNS updates
take to long time TCP connections break, security problems
Shahzad Malik Lecture 9 79Wireless Communications – Wireless Data
Mobile IP - Terminology
Mobile Node (MN) system (node) that can change the point of connection
to the network without changing its IP address Home Agent (HA)
system in the home network of the MN, typically a router registers the location of the MN, tunnels IP datagrams to the COA
Foreign Agent (FA) system in the current foreign network of the MN, typically a
router forwards the tunneled datagrams to the MN, typically also the
default router for the MN Care-of Address (COA)
address of the current tunnel end-point for the MN (at FA or MN) actual location of the MN from an IP point of view can be chosen, e.g., via DHCP
Correspondent Node (CN) communication partner
Shahzad Malik Lecture 9 80Wireless Communications – Wireless Data
Example network
mobile end-system
Internet
router
router
router
end-system
FA
HA
MN
home network
foreign network
(physical home networkfor the MN)
(current physical network for the MN)
CN
Shahzad Malik Lecture 9 81Wireless Communications – Wireless Data
Data transfer to the mobile system
Internet
sender
FA
HA
MN
home network
foreignnetwork
receiver
1
2
3
1. Sender sends to the IP address of MN,HA intercepts packet (proxy ARP)2. HA tunnels packet to COA, here FA, by encapsulation3. FA forwards the packet to the MN
CN
Shahzad Malik Lecture 9 82Wireless Communications – Wireless Data
Data transfer from the mobile system
Internet
receiver
FA
HA
MN
home network
foreignnetwork
sender
1
1. Sender sends to the IP address of the receiver as usual, FA works as default router
CN
Shahzad Malik Lecture 9 83Wireless Communications – Wireless Data
Overview
CN
routerHA
routerFA
Internet
router
1.
2.
3.
homenetwork
MN
foreignnetwork
4.
CN
routerHA
routerFA
Internet
router
homenetwork
MN
foreignnetwork
COA
Shahzad Malik Lecture 9 84Wireless Communications – Wireless Data
Network integration
Agent AdvertisementHA and FA periodically send advertisement messages into
their physical subnetsMN listens to these messages and detects, if it is in the
home or a foreign network (standard case for home network)
MN reads a COA from the FA advertisement messages Registration (always limited lifetime!)
MN signals COA to the HA via the FA, HA acknowledges via FA to MN
these actions have to be secured by authentication Advertisement
HA advertises the IP address of the MN (as for fixed systems), i.e. standard routing information
routers adjust their entries, these are stable for a longer time (HA responsible for a MN over a longer period of time)
packets to the MN are sent to the HA, independent of changes in COA/FA
Shahzad Malik Lecture 9 85Wireless Communications – Wireless Data
Encapsulation
original IP header original data
new datanew IP header
outer header inner header original data
Shahzad Malik Lecture 9 86Wireless Communications – Wireless Data
Encapsulation I
Encapsulation of one packet into another as payloade.g. IPv6 in IPv4 (6Bone), Multicast in Unicast (Mbone)here: e.g. IP-in-IP-encapsulation, minimal encapsulation or
GRE (Generic Record Encapsulation) IP-in-IP-encapsulation (mandatory, RFC 2003)
tunnel between HA and COA
Care-of address COAIP address of HA
TTLIP identification
IP-in-IP IP checksumflags fragment offset
lengthDS (TOS)ver. IHL
IP address of MNIP address of CN
TTLIP identification
lay. 4 prot. IP checksumflags fragment offset
lengthDS (TOS)ver. IHL
TCP/UDP/ ... payload
Shahzad Malik Lecture 9 87Wireless Communications – Wireless Data
Optimization of packet forwarding
Triangular Routingsender sends all packets via HA to MNhigher latency and network load
“Solutions”sender learns the current location of MNdirect tunneling to this locationHA informs a sender about the location of MNbig security problems!
Change of FApackets on-the-fly during the change can be lostnew FA informs old FA to avoid packet loss, old FA now
forwards remaining packets to new FA this information also enables the old FA to release
resources for the MN
Mobile Ad-hoc Networks (MANETs)
Shahzad Malik Lecture 9 89Wireless Communications – Wireless Data
Multi-Hop wireless networks
May need to traverse multiple links to reach destination
Mobility causes route changes
Shahzad Malik Lecture 9 90Wireless Communications – Wireless Data
Mobile Ad Hoc Networks (MANET)
Host movement frequent Topology change frequent
No cellular infrastructure. Multi-hop wireless links. Data must be routed via intermediate nodes.
A B AB
Source: Vaidya
Shahzad Malik Lecture 9 91Wireless Communications – Wireless Data
MANETs
Do not need backbone infrastructure support Are easy to deploy Useful when infrastructure is absent, destroyed or
impractical Infrastructure may not be present in a disaster area or war
zone Applications
Military environments soldiers, tanks, planes
Emergency operations search-and-rescue policing and fire fighting
Civilian environments taxi cab network meeting rooms sports stadiums
Shahzad Malik Lecture 9 92Wireless Communications – Wireless Data
MAC in MANET
IEEE 802.11 DCF is most popular Easy availability Uses RTS-CTS to avoid hidden terminal problem Uses ACK to achieve reliability
802.11 was designed for single-hop wireless Does not do well for multi-hop ad hoc scenarios Reduced throughput Exposed terminal problem
Shahzad Malik Lecture 9 93Wireless Communications – Wireless Data
Routing in MANET
Mobile IP needs infrastructure Home Agent/Foreign Agent in the fixed network DNS, routing etc. are not designed for mobility
MANET no default router available “every” node also needs to be a router
Shahzad Malik Lecture 9 94Wireless Communications – Wireless Data
MANET routing protocols
Reactive protocols Determine route if and when needed Example: DSR (dynamic source routing)
Proactive protocols Traditional distributed shortest-path protocols Example: DSDV (destination sequenced distance
vector) Hybrid protocols
Adaptive; Combination of proactive and reactive Example : ZRP (zone routing protocol)
Shahzad Malik Lecture 9 95Wireless Communications – Wireless Data
MANET variations
Fully symmetric environment all nodes have identical capabilities and responsibilities
Asymmetric Capabilities transmission ranges, battery life, processing capacity may
differ at different nodes Asymmetric Responsibilities
only some nodes may route packets Mobility patterns may differ from one scenario to another Mobility characteristics (speed, predictability) may be
different for different applications Traffic characteristics may differ
timeliness constraints reliability requirements
Shahzad Malik Lecture 9 96Wireless Communications – Wireless Data
MANET summary
Routing is the most studied problem
Interplay of layers is being researched
Large number of simulation based expts
Small number of field trials
Very few reported deployments
Fertile area for imaginative applications
Integration of Cellular Networks and WLANs
Shahzad Malik Lecture 9 98Wireless Communications – Wireless Data
Why Cellular + WLAN?
Cellular
Outdoor
Wide area mobility
Moderate to high
mobility
Moderate bandwidth
High cost
Good for everywhere
except hotspots
WLAN
Indoor
Small area mobility
Low mobility
High bandwidth
Low cost
Good for hotspots of
high-bandwidth activity
Shahzad Malik Lecture 9 99Wireless Communications – Wireless Data
3G UMTS Architecture
MSC
VLR
PSTN
BS
BS
BS
RNC
RNC
BS
GGSN InternetSGSN
• GGSN• connected to the Internet• IP address assignment• session management
• SGSN• manage mobility context• interact with RNC to perform RAB setup• perform inter-RNC handover
GnIu
Iu
Gi
Gs
Shahzad Malik Lecture 9 100Wireless Communications – Wireless Data
802.11 WLAN Infrastructure Mode
Association Point (AP) Base station
Basic Service Set Cell 100-300 meters
Every MN is associated to at most one AP
MACDistributed Coordinated
Function (DCF) CSMA/CA
Point Coordinated Function (PCF)
Polling IAPP for Roaming
BSS1
MN1
AP1
BSS2
MN2
AP2
Distribution System
Shahzad Malik Lecture 9 101Wireless Communications – Wireless Data
Integration ScenariosScenario 1:
Common Billing and Customer Care No real inter-working
Scenario 2: 3GPP System-based Access Control and Charging Common AAA service – Reusing GPRS AAA
Scenario 3: Access to 3GPP GPRS-based Services E.g. WAP, Location-base service etc
Scenario 4: Service Continuity No stringent requirement on handover
Scenario 5: Seamless Services Service continuity without any noticeable difference
Scenario 6: 3GPP Circuit Switched Services E.g. Voice service should be available in WLAN network
Shahzad Malik Lecture 9 102Wireless Communications – Wireless Data
Integration – At GGSN
SGSN GGSN
Internet
BS
BS
RNC
WLAN Network
AR1 AR2Macro Cell (UMTS)
Micro Cell (802.11)
AAA
Shahzad Malik Lecture 9 103Wireless Communications – Wireless Data
Integration – At SGSN
SGSN GGSN
Internet
BS
BS
RNC
WLAN Network
AR1 AR2Macro Cell (UMTS)
Micro Cell (802.11)
Shahzad Malik Lecture 9 104Wireless Communications – Wireless Data
Integration – At RNC
SGSN GGSN
Internet
BS
BS
RNC
WLAN Network
AR1 AR2Macro Cell (UMTS)
Micro Cell (802.11)
Shahzad Malik Lecture 9 105Wireless Communications – Wireless Data
Integration
Shahzad Malik Lecture 9 106Wireless Communications – Wireless Data
IA: FeaturesWLAN is an IP network
All IETF standard protocols IP Local Mobility Management
(LMM) IP level integrationSGSN is the integration point
SGSN maintains mobility context that can be modified to include MN’s mobility state in WLAN
No need to update HLR/VLR when MN is in WLAN
MN in a BSS with multiple interfaces can access:
Packet switched services through WLAN
Circuit switched services through UMTS
WLAN IP Network
AR AR
BR BR
SRNS SGSN
Packet Data Signallling
Packet Data Bearer Voice (CS)
GGSN
Internet
Shahzad Malik Lecture 9 107Wireless Communications – Wireless Data
IA: ChallengesSynchronization between SGSN
and WLAN For mobility management For session management
GPRS is connection oriented, whereas WLAN network is connection-less
GPRS is a single-hop IP network and WLAN is a multi-hop IP network
Mobility management in WLAN network is qualitatively different
GPRS is essentially tunneled-based
WLAN could be tunnel-based or routing-based
Terminal Model How to maintain connection
between MN and SGSN through WLAN?
WLAN IP Network
AR AR
BR BR
SRNS SGSN
Packet Data Signallling
Packet Data Bearer Voice (CS)
GGSN
Internet
Shahzad Malik Lecture 9 108Wireless Communications – Wireless Data
Terminal ArchitectureMobile Node is equipped with
two interfaces UMTS-GPRS interface 802.11 WLAN interface
GPRS specific protocols are implemented at the device driver level
Applications GPRS applications can
access GPRS-aware services through GPRS service layer
IP applications use IP protocols through IP stack
Mobility Management and QoS signaling protocols
LMM and RSVP
ICMPIGMP
Internet Protocol (IP)
TCPUDP
LMM RSVP
GMMSM
RRC PDCP
RLC
MAC
L1 802.11 PHY
802.11 MAC
802.2 LLC
UMTS Device Driver
GPRS Service Layer
802.11 Device Driver
Application Layer
Shahzad Malik Lecture 9 109Wireless Communications – Wireless Data
Mobility Management
LMM state machine is
augmented with two new states
WLAN-attached stated: a
transition point from GPRS to
WLAN network
GPRS-attached state:
representing the MN is
disassociated from WLAN
GPRS state machine is
augmented with one new state
WMM-connected state: MN is
receiving PS service from
WLAN, hence no RAB is set
up for PDP contexts in UTRAN
PMM-IDLE
PMM-DETACHED
PMM-CONNECTED
WMM-CONNECTED
GPRS MM Context
Handover Points
GPRS -ATTACHED
WLAN-ATTACHED
LMM States
WLAN LMM Context
Handover Points
Shahzad Malik Lecture 9 110Wireless Communications – Wireless Data
UMTS-WLAN Handover Handover signalling through WLAN
Avoid keeping separate signalling connection through UTRAN
Support abrupt disconnection SGSN can implement modified
mobility agent functionality to allow Mobile IP signalling between AR and SGSN
W_Route Area Update may not be a new signalling protocol, it may be BU with some extensions
It is shown differently here to show explicit transaction between WLAN and UMTS
Resource Reservation following HO may be required to adjust QoS parameters and acquire resources in WLAN network including 802.11 radio resources when it offers QoS
UMTS – WLAN Handover
MN AR SGSN SRNC
Beacon Association Request
Router Advertisement
Binding Update
[W_Route Area Update] RAB
Release
RAB Release Complete
[W_Route Area Update Accept]
Binding Update Ack
[W_Route Area Update Complete]
RSVP Path
RSVP Resv
Association Response
Authentication & COA Assignment
RSVP Path RSVP Path
RSVP Resv RSVP Resv
Shahzad Malik Lecture 9 111Wireless Communications – Wireless Data
Concluding RemarksAn Integration Architecture is discussed:
UMTS macro cells overlaid on 802.11 micro cells Access services through the networks that optimize their
delivery Seamless handover between two networks SGSN as integration point
Modifications only in SGSN inside the network No gateway functionality in WLAN network
• Incurs no additional cost to WLAN network deployment IP level inter-system handover
No GPRS specific layer-2 level inter-working function in WLAN network
Transparency to IP applications IETF standardized protocols in WLAN networks
Reuse UMTS AAA infrastructure