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A Tale of Two Technologies: A Tale of Two Technologies:

Lecture #2

A Tale of Two Technologies: A Tale of Two Technologies: WiMAX vs. LTEWiMAX vs. LTE

Dr. Kun YangUniversity of Essex, UK

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y

17th March 2009 @ NII

Agenda

Wireless LAN (Local Area Networks)Wireless MAN: WiMAXMobile Cellular Systems3GPP LTE (Long Term Evolution)Femto Cell and Mobility

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Q&A

Some slides here pay courtesy to J. He, & D. Hunter.

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IEEE 802 (LAN) vs OSI

IEEE 802 reference model

Lower layers of OSI model

Physical

Media access control (MAC)

Logical link control (LLC)

•IEEE 802 11

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IEEE 802.11•IEEE 802.15•IEEE 802.16•IEEE 802.21

IEEE 802.11 Version Summary

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3

Comparison: infrastructure vs. ad-hoc networks

infrastructurenetwork

ad hoc network

APAP

AP

wired network

AP: Access Point

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ad-hoc network

802.x LAN802.11 LAN

802.11 - Architecture of an infrastructure network

Station (STA)terminal with access mechanisms to the wireless medium and radio contact to the access point

STA1

Distribution System

Portal

AccessPoint

BSS

BSS1

AccessPoint

contact to the access pointBasic Service Set (BSS)

group of stations using the same radio frequency

Access Pointstation integrated into the wireless LAN and the distribution system

Portal

ESS

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802.11 LAN

BSS2 Portalbridge to other (wired) networks

Distribution Systeminterconnection network to form one logical network (EES: Extended Service Set) based on several BSS

STA2 STA3

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802.11 - Architecture of an ad-hoc network

Direct communication within a limited range

802.11 LAN

STA1g

Station (STA):terminal with access mechanisms to the wireless mediumBasic Service Set (BSS):group of stations using the same radio frequency

BSS

BSS1

STA1

STA2

STA3

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802.11 LAN

BSS2

STA4

STA5

ETSI - HIPERLANETSI standard

European standard, cf. GSM, DECT, ...Enhancement of local Networks and interworking with fixed networksintegration of time-sensitive services from the early beginningintegration of time-sensitive services from the early beginning

HIPERLAN familyone standard cannot satisfy all requirements

• range, bandwidth, QoS support• commercial constraints

HIPERLAN 1 standardized since 1996

medium access network layer

higher layers

logical link

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physical layer

channel accesscontrol layer

control layer

physical layer

data link layer

HIPERLAN layers OSI layers

network layer

physical layer

medium accesscontrol layer

gcontrol layer

IEEE 802.x layers

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802.11 - MAC layer I - DFWMACTraffic services

Asynchronous Data Service (mandatory)• exchange of data packets based on “best-effort”

f b d d l i• support of broadcast and multicastTime-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)

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• 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 IIPriorities

defined through different inter frame spaces (IFS)no guaranteed, hard prioritiesSIFS (Sh t I t F S i )SIFS (Short Inter Frame Spacing)

• highest priority, for ACK, CTS, polling responsePIFS (PCF IFS)

• medium priority, for time-bounded service using PCFDIFS (DCF, Distributed Coordination Function IFS)

• lowest priority, for asynchronous data service

DIFSDIFS

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t

medium busy SIFSPIFSDIFSDIFS

next framecontention

direct access if medium is free ≥ DIFS

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DIFSDIFScontention window(randomized back-offmechanism)

802.11 - CSMA/CA access method I

t

medium busy next frame

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

slot timedirect access if medium is free ≥ DIFS

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p ( ) g ( pservice 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

station1

DIFSboe bor

DIFSboe bor

DIFS DIFSboe busy

busy

station2

station3

station4

t ti

boe

boe

busy

bor

boe

boe

busy

busy

boe

boe

bor

bor

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t

boe

station5

packet arrival at MAC

elapsed backoff time

bor residual backoff time

busy medium not idle (frame, ack etc.)

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802.11 - CSMA/CA access method IISending unicast packets

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

SIFS

DIFS

C

sender data

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t

data

ACK

waiting time

otherstations

receiverDIFS

contention

802.11 - DFWMACSending 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

SIFS

DIFS

ACKreceiver

sender dataRTS

CTSSIFS SIFS

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t

data

defer access

otherstations

DIFS

contention

NAV (RTS)NAV (CTS)

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Fragmentation

DIFSfRTS f

t

SIFS

data

ACK1

otherstations

receiver

sender frag1

DIFS

RTS

CTSSIFS SIFS

NAV (RTS)NAV (CTS)

NAV (frag1)NAV (ACK1)

SIFSACK2

frag2

SIFS

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tcontention

DFWMAC-PCF I

SuperFramet0

di b

t1

PIFS

stations‘NAV

wirelessstations

point coordinator

D1

U1

SIFS

NAV

SIFSD2

U2

SIFS

SIFSmedium busy

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At the beginning of the contention-free period, the AP transmits a beacon frame (not shown above –see later)

This announces the maximum duration of the contention-free periodAll stations use this duration to set their NAVs

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DFWMAC-PCF II

t2 t3 t4

tstations‘NAV

wirelessstations

point coordinator

D3

NAV

PIFSD4

U4

SIFS

SIFSCFend

contentioncontention free period

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period

802.11 - Frame formatTypes

control frames, management frames, data framesSequence numbersq

important against duplicated frames due to lost ACKs Addresses

receiver, transmitter (physical), BSS identifier, sender (logical)Miscellaneous

sending time, checksum, frame control, data2 2 6 6 6 62 40-2312bytes

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FrameControl

DurationID

Address1

Address2

Address3

SequenceControl

Address4 Data CRC

version, type, fragmentation, security, ...

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MAC address format

scenario to DS fromDS

address 1 address 2 address 3 address 4

ad-hoc network 0 0 DA SA BSSID -i f t t 0 1 DA BSSID SAinfrastructurenetwork, from AP

0 1 DA BSSID SA -

infrastructurenetwork, to AP

1 0 BSSID SA DA -

infrastructurenetwork, within DS

1 1 RA TA DA SA

DS: Distribution SystemAP: Access PointDA: Destination Address

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DA: Destination AddressSA: Source AddressBSSID: Basic Service Set IdentifierRA: Receiver AddressTA: Transmitter Address

802.11 - MAC management

Synchronizationtry to find a LAN, try to stay within a LANi timer etc.

Power managementsleep-mode without missing a messageperiodic sleep, frame buffering, traffic measurements

Association/Reassociationintegration into a LAN

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roaming, i.e. change networks by changing access points scanning, i.e. active search for a network

MIB - Management Information Basemanaging, read, write

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A bit info on MANET (Mobile Ad hoc Networks) ….

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MANET IntroductionMobile ad hoc networks (MANETs) are basically peer-to-peermultihop mobile wireless networks that

have neither fixed communication infrastructure nor any base stations (BSs) nor any base stations (BSs).

Control is more complex due to its ad hoc nature and mobility.Unlike the typical Internet, which has dedicated nodes for basic network operations such as authorization, routing, packet forwarding, and network management, all these functions should be performed by all MNs themselves in MANETs.

Efficient routing of packets is a primary MANET challenge. MANETs use multihop rather than single-hop routing to deliver

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M N s use u t op at e t a s g e op out g to de ve packets to their destination.

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RoutingConventional networks typically rely on distance-vector or link-state algorithms, which depend on periodic broadcast advertisements of all routers to keep routing tables up-to-date. I MANET l th l ith hi h In some cases, MANETs also use these algorithms, which ensure that the route to every host is always known. However, this approach presents several problems:

periodically updating the network topology increases bandwidth overhead; repeatedly awakening hosts to receive and send information quickly exhausts batteries; the propagation of routing information which depends on the

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the propagation of routing information, which depends on the number of existing hosts, causes overloading, thereby reducing scalability; redundant routes accumulate needlessly; communication systems often cannot respond to dynamic changes in the network topology quickly enough.

On-demand Routing Algorithms

Rather than relying on periodical broadcasts of available routes, called proactive, a re-active algorithm p gdiscovers routes is needed. Because the route to every mobile node is not known at any given time, these algorithms must build and maintain routes. Two representative MANET re-active algorithms:

DSR: data source routing

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gAODV: ad-hoc distance vector

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Bluetooth

Why Bluetooth1994 – Ericsson study on a wireless technology to link mobile phones and accessoriesphones and accessoriesLets replace all those ugly wires with a short range low data rate wireless system.Basically to standardise wireless keyboards and mice

• And add a few more on the way

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Main references:IEEE Std 802.15.1, “Information Technology — Telecommunications and Information Exchange between Systems — Local and Metropolitan Area Networks — Specific Requirements Part 15.1: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Wireless Personal Area Networks (WPANs),” 2002.

Bluetooth

Bluetooth is a standard for wireless communications. Bluetooth is an infrastructure less short-range wireless

d d l h bl b lsystem intended to replace the cable between electronic user terminals with RF links. The devices can also be used for communications between portable computers, act as bridges between other networks, or serve as nodes of ad hoc networks. This range of applications is known as wireless personal

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area network (WPAN). Bluetooth devices use the 2.4 GHz band, which is unlicensed in most countries.

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Piconet

The Bluetooth topology is a star network where a master node can have up to seven slave nodes wirelessly connected to it to form a piconet. Pi t i th i l t fi ti f Bl t th t kPiconet is the simplest configuration of a Bluetooth network.Each piconet uses a centrally assigned time-division multiple access (TDMA) schedule and frequency hopping pattern. Transmission power is typically around 20 dBm and the transmission range is on the order of tens of meters.

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ScatternetPiconets may be connected together, thus forming a scatternet.A scatternet supports multihop.

i.e., two nodes can communicate with each other even if there is no direct connection between them by using other nodes as relays direct connection between them by using other nodes as relays.

Two piconets can communicate by means of a common node belonging to both of them. A node can be a master in one piconet at most and a slave in several others.

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Bluetooth vs. IEEE 802.11 (1)

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Bluetooth vs. IEEE 802.11 (2)

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Agenda

Wireless LAN (Local Area Networks)Wireless MAN: WiMAX (IEEE 802.16)

WiMAX PHY/MAC/QoS FeaturesComparison with IEEE 802.11

Mobile Cellular Systems

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3GPP LTE (Long Term Evolution)Femto Cell and MobilityQ&A

IEEE 802.16WiMAX is the commercialization of the IEEE 802.16 standard,

Started at the National Institute of Standards and Technologies (NIST) in 1998 and then transferred to the IEEE to form Working Group 802.16.

h k l f h lIn June 2004, the working group won approval for the latest 802.16 standard for fixed wireless access, known as IEEE 802.16-2004. In December 2005, an extension that addresses mobility also won approval as IEEE 802.16e-2005.

Specifies the air interface, including the medium access control layer (MAC) and physical layer (PHY), of fixed point-to-multipoint (PMP) and Mesh broadband wireless access systems providing multiple services

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services. The standard includes a particular physical layer specification broadly applicable to systems operating between 10 and 66 GHz, and below 10GHz.

WiMAX: Worldwide Inter-operability for Microwave Access

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The WiMAX ForumComprises a group of industry leaders (Intel, AT&T, Samsung, Motorola, Cisco, and others), has closely supported and promoted the technology. The group’s workforce is divided along multiple working groups that focus on technical, regulatory, and marketing aspects.Loads of live discussion about technical details of WiMAX and its simulation and implementation.

High Performance Radio Metropolitan Area Network (HiperMAN), the European Telecommunications Standards

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( p ) pInstitute’s MAN standard, share the same physical layer (PHY) and medium access control (MAC) layer specifications.

Standard History

• Original fixed wireless broadband air Interface for 10 – 66 GHz: Line‐of‐sight only, Point‐to‐Multi‐Point applications

• First standard based on proprietary implementations of DOCSIS/HFC       architecture in wireless domain

802.16(Dec 2001)

• Extension for 2‐11 GHz: Targeted for non‐line‐of‐sight, Point‐to‐Multi‐Point applications like “last mile” broadband access

GHz: Line of sight only, Point to Multi Point applications

• 802.16 Amendment WiMAX System Profiles 10 ‐ 66 GHz, line‐of‐sight

(Dec 2001)

802.16c(2002)

802.16a(Jan 2003)

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• Adds WiMAX System Profiles and Errata for 2‐11 GHz

• MAC/PHY Enhancements to support subscribers moving at vehicular speeds

802.16d (802.16-2004)

(Oct 2004)

802.16e(802.16-2005)

(Dec 2005)

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Other versions

802.16f-2005 — Management Information Base (MIB)802.16g-2007 — Management Plane Procedures and Services 802 16k 2007 Bridging of 802 16 (an amendment to 802 1D) 802.16k-2007 — Bridging of 802.16 (an amendment to 802.1D) 802.16h — Improved Coexistence Mechanisms for License-Exempt Operation 802.16i — Mobile Management Information Base 802.16j — Multihop Relay Specification 802.16Rev2 — Consolidate 802.16-2004, 802.16e, 802.16f, 802.16g and possibly 802.16i into a new document.

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802.16m — Advanced Air Interface. Data rates of 100 Mbit/s for mobile applications and 1 Gbit/s for fixed applications.

Source: wikipedia

ServicesDeliver both fixed and mobile wireless broadband servicesTwo forms of wireless service:

Desirable Non-line-of-sight (NLOS) service• Small antenna• 2 – 11 GHz• Up to 8 km radius (cell phone zone)

Line-of-sight (LOS)• Fixed antenna; strong and stable connection• 10 – 66 GHz• Up to 50 km radius

ApplicationsB db d d d

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Broadband on-demand• Fast deployment of WLAN hotspots

Residential broadband• Hard competition with DSL, cable and fiber

Cellular BackhaulUnderserved areasEmergency communication systems

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Reference Model

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Protocol Stack

UpperLayers

Service specific convergence sublayer

MAC sublayer common part

Security sublayer

Transmission convergence sublayer

Data LinkLayer

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Physical medium dependent sublayer(QPSK | QAM-16 | QAM-64)

PhysicalLayer

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PHY Considerations

Broadband channelsWide channels (20, 25, or 28 MHz)( )High capacity – Downlink AND Uplink

Multiple accessTDM/TDMAHigh rate burst modems

Adaptive burst profiles on uplink and downlinkDuplex scheme

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Duplex scheme Time-Division Duplex (TDD)Frequency-Division Duplex (FDD) [including Burst FDD]

Support for half-duplex terminals (cheaper)

Adaptive PHY

Channel Width

Symbol Rate (M / )

Bitrate (Mbit/s) Num. of PSs (Phy. slots)QPSK 16- 64-QAM

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(MHz) (Msym/s) (1ms frame)QAM

20 16 32 64 96 4000

25 20 40 80 120 5000

28 22.4 44.8 89.6 134.4 5600

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Adaptive Burst Profiles

Burst profileSet of parameters that describe the uplink or downlink transmission properties associated with an interval usage code transmission properties associated with an interval usage code (IUC)Each profile contains parameters such as modulation type, forward error correction (FEC) type, preamble length, guard time, etc.

Dynamically assigned according to link conditionsBurst by burst, per subscriber stationTrade-off between capacity vs. robustness in real time

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p yBurst profile for downlink broadcast channel is well known

All other burst profiles could be configured “on the fly”

TDD Frame

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Frame duration: 1 ms    Physical Slot (PS) = 4 symbols

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TDD Downlink Subframe

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DIUC: Downlink Interval Usage CodeTTG: Transmit Transition Gap

Burst FDD Frame

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FDD Downlink Subframe

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TDMA portion: transmits data to some half-duplex SSs (the ones scheduled to transmit earlier in the frame than they receive). Need preamble to re-sync (carrier phase)

Typical Uplink Subframe (TDD or FDD)

SSTG : Subscriber Station Transition GapUIUC: Uplink Interval Usage Code

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Air Interfaces Specifications

Designation Applicability MAC DuplexingWirelessMAN-SC 10-66 GHz

LicensedBasic TDD, FDD,

HFDDWirelessMAN-SCa 2-11 GHz

LicensedBasic, (ARQ), (STC), (AAS)

TDD, FDD

WirelessMAN-OFDM

2-11 GHz Licensed

Basic, (ARQ), (STC), (AAS)

TDD, FDD

2-11 GHz License-exempt

Basic, (ARQ), (STC), (DFS), (MSH), (AAS)

TDD

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WirelessMAN-OFDMA

2-11 GHz Licensed

Basic, (ARQ), (STC), (AAS)

TDD, FDD

2-11 GHz License-exempt

Basic, (ARQ), (STC), (DFS), (MSH), (AAS)

TDD

MAC Requirements

Provide Network AccessAddress the Wireless environment

e.g., very efficient use of spectrumBroadband services

Very high bit rates, downlink and uplinkA range of QoS requirementsConvergence layers to ATM, IP, Ethernet, ...

Likelihood of terminal being shared

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Base Station may be heavily loadedSecuritySupport PHY alternatives

Adaptive mod, TDD/FDD; single-carrier, OFDM/OFDMA, etc.

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MAC layer architecture

MAC

IP/Ethernet/VLAN

Packet convergence sub‐layer(classify, connection, QoS, 

ATM

ATM convergence sub‐layer(classify, connection, QoS, 

Layer bandwidth allocation) bandwidth allocation)

Basic connection

(RLC and short, Time‐critical MAC msg)

Primary connection

(authentication,Connection 

setup)

Secondary connection

(DHCP, TFTP, SNMP..)

Traffic connection

(data)

Other connects(Initial accessBroadcastMulticast)

Grant management subheader Fragmentationsubheader

Packingsubheader

MAC (G i b d idth t) H d (6 b t 48 bit )

Mesh subheaderManagement connections

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MAC (Generic or bandwidth request) Header (6 bytes=48 bits)Transmission Convergence sub‐layer 

PHY 10‐66 GHz PHY 2‐11 GHz

Basic connection: short, time-urgent msgPrimary connection:Long, delay-tolerant msgSecondary connection: Delay-tolerant standard-based msg

QoS Support

QoS support is critical for the support of commercial applications

f l f d hDefines 4+1 class of services, associated with connections – ref. next slideScheduling Services Parameters

Maximum sustained traffic rateMinimum reserved traffic rateMaximum latency

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Tolerated jitterTraffic priorityRequest/transmission policy

Bandwidth request and grant mechanisms

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Classes of Service

Unsolicited Grant Services (UGS)for constant bit-rate (CBR) or CBR-like service flows (SFs), e.g. T1/E1T1/E1

Real-time Polling Services (rtPS)for rt-VBR-like SFs such as MPEG video

Non-real-time Polling Services (nrtPS)for nrt SFs with better than best effort service such as bandwidth-intensive file transfer

B t Eff t (BE)

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Best Effort (BE)for best-effort traffic

Mandatory QoS service flow parameters

Maximum sustained traffic rate (MSTR)Minimum reserved traffic rate (MRTR)Maximum latency (ML)Maximum latency (ML)Tolerated jitter (TJ)Traffic priority (TP)Request/transmission policy (RTP)

Service MSTR MRTR ML TJ TP RTP

UGS Yes Optional Yes Yes No Yes

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rtPS Yes Yes Yes No No Yes

nrtPs Yes Yes No No Yes Yes

BE No No No No Yes Yes

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Bandwidth Request and AllocationSSs make bandwidth requests to the BS in many ways:

Implicit requests (UGS): No actual messages, negotiated at connection setup

BS grants/allocates bandwidth in one of two modes:

pSend a standalone MAC message called ”BW request” in an allready granted slot (allocated via polling service).Use the ”contention request opportunities” interval, e.g., upon being polled by the BS (multicast or broadcast poll).Piggyback a BW request message on a data packet.

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Grant Per Subscriber Station (GPSS)Grant Per Connection (GPC)

Decision based on requested bandwidth and QoS requirements vs the available resources at BS.Grants are realized through the UL-MAP.

Unicast Polling

1. BS allocates space for the SS in BS SSthe uplink subframe (using UL-MAP)

2. SS uses the allocated space to send a bw request.

3. BS allocates the requested space for the SS if available (using UL-

PollRequest

AllocateData

BS SS

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( gMAP

4. SS uses allocated space to send data.scheduling

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Agenda

Wireless LAN (Local Area Networks)Wireless MAN: WiMAX (IEEE 802.16)

WiMAX PHY/MAC FeaturesComparison with IEEE 802.11

Mobile Cellular Systems

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3GPP LTE (Long Term Evolution)Femto cell and MobilityQ&A

UNII

ISM

802.11 vs. 802.16: Spectrum

InternationalLicensed

USLicensed

JapanLicensed

InternationalLicensed ISM

802 16

GHz1 32 4 5

802.11

802.16

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ISM: Industrial, Scientific & Medical Band – Unlicensed bandU-NII: Unlicensed National Information Infrastructure – Unlicensed band,

by FCC, mainly for 802.11a.

802.16a has both licensed and license-exempt options

J. Orr of Proxim

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Channel Performance

ChannelBandwidth

Maximumbps/Hz

MaximumData Rate

802.16a ~5.0 bps/Hz

~2.7 bps/Hz54 Mbps20 MHz

63 Mbps10, 20 MHz;

1.75, 3.5, 7, 14 MHz;3, 6 MHz

802.11a

Scalability: 802 11 MAC d i d t t 10’ f h

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802.16 is designed for metropolitan performance

802.11a MAC designed to support 10’s of users whereas 802.16 to support thousands of users

J. Orr of Proxim

QoSIEEE 802.11 IEEE 802.16a

Contention-based MAC Grant-request MAC

QoS

(CSMA/CA) => poor performance under heavy load.No guaranteed QoSNo differentiated service on a per-user basisTDD only – asymmetric 802 11 Q S i i iti ti

qQoS mechanism is part of the standard

Designed to support Voice and Video

Supports 5 differentiated service levels

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802.11e: QoS is prioritization only

levelsTDD/FDD – asymmetric or symmetric

AMC: Adaptive Modulation and Coding

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802.11 802.16aOptimized for ~100 meters Optimized for up to 50 Km

Range

No “near-far” compensation

Designed to handle indoor multi-path (delay spread of 0.8μ seconds), optimized for indoor

Designed to handle many users spread out over kilometers

Designed to tolerate greater multi-path delay spread up to 10.0μ seconds, optimized for outdoor NLOS performance

PHY d MAC d i d ith lti il

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Optimization centers around PHY and MAC layer for 100m range

Range can be extended by increasing trans. Power - may be non-standard

PHY and MAC designed with multi-mile range in mind

Standard MAC

802.16a is designed for distance

802.11 and 802.16 both gain broader industry acceptance through conformance and

IEEE 802.11 vs 802.16: Summary

• 802.11 is mainly optimized for license-exempt LAN operation802 16 i i l ti i d f li d MAN

acceptance through conformance and interoperability by multiple vendors

802.16 complements 802.11 by creating a complete MAN-LAN solution

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• 802.16 is mainly optimized for licensed MAN operation.

J. Orr of Proxim

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Agenda

Wireless LAN (Local Area Networks)Wireless MAN: WiMAX (IEEE 802.16)Mobile Cellular Systems3GPP LTE (Long Term Evolution)Femto cell and Mobility

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Q&A

Motivation

Radio spectrum is very limited, we have only 10-25MHz dedicated to wireless communication. h b d d h ll h l fSuch narrow bandwidth allows 100-400 channels of

reasonable quality, which is not rational and commercially not profitable to develop network for such small number of mobile subscribers.

Then the cellular idea: division of the whole geographical area to relatively small cells, and each cell ma reuse the same frequencies b reducing power of

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may reuse the same frequencies by reducing power of transmission. Each cell has its own antenna (base station), and all base stations are interconnected using microwave or cable communication.

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A bit of historyOnce upon a time there was analog cellular communication

didn’t support encryption, compression, and ISDN pp yp pcompatibility; in addition each country (company) developed its own system, which was incompatible with everyone else’s in equipment and operation.

So, in early 80s Europeans realized that pan-European public mobile system should be developed. The new system had to meet certain criteria:

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system had to meet certain criteria: Good subjective speech quality Low terminal and service cost International roaming ISDN compatibility Digital

Cellular Network Organization

Areas divided into cellsEach cell served by its own base station consisting ofbase station consisting of transmitter, receiver, and control unit,Cells set up such that antennas of all neighbors are equidistant (hexagonal pattern)

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Frequency Reuse

Adjacent cells are assigned different frequencies to avoid interference or crosstalk

b f b llObjective is to reuse frequency in nearby cells10 to 50 frequencies assigned to each cellTransmission power controlled to limit power at that frequency escaping to adjacent cells.The issue is to determine how many cells must intervene between two cells using the same frequency.

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Examples

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N=4 N=7

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Frequency reuse

Reuse Distance (D): minimum distance between centres of cells that use the same band of frequencies (co-channels)

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Increasing Capacity

Adding new channelsFrequency borrowing – frequencies are taken from d ll b d lladjacent cells by congested cells

Cell splitting – cells in areas of high usage can be split into smaller cellsCell sectoring – cells are divided into a number of wedge-shaped sectors, each with their own set of channels. Directional Antennas must be used in this case.

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Microcells – a decrease in cell size results in a reduction of the radiated power levels.

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Example: Microcells

Area: 213 km2 , Bandwidth: 336 channels per cluster, cells per cluster: N=7

Number of channels per cell is 336/7=48If cell radius R=1.6 km, then 32 total cells,

Total channel capacity is 48 x 32 = 1536If cell radius R=0.6 km, then 128 cells

Total channel capacity is 48 x128 =6144 channels

69Total cells: 32 Total cells: 128

Architecture of the GSM system

GSM is a PLMN (Public Land Mobile Network)several providers setup mobile networks following the GSM standard within each countrystandard within each countrycomponents

• MS (mobile station)• BS (base station)• MSC (mobile switching center)• LR (location register)

subsystems• RSS (radio subsystem): covers all radio aspects

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• NSS (network and switching subsystem): call forwarding, handover, switching

• OSS (operation subsystem): management of the network

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GSM: overview

fixed networkGMSCHLRNSS

OMC, EIR, AUC

BSC

BSC

MSC MSCVLR

with OSS

VLR

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RSS

radiosubsystem

MS MS

network and switching subsystem

fixedpartner networks

GSM: system architecture

Um

AbisBTSBSC

BTS

MSC

SS

7

EIR

HLR

ISDNPSTN

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ABSS

BTSBSC

BTS MSCIWF

ISDNPSTN

PSPDNCSPDN

VLR

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Agenda

Wireless LAN (Local Area Networks)Wireless MAN: WiMAX (IEEE 802.16)Mobile Cellular Systems3GPP LTE (Long Term Evolution)Comparison and Mobility

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Q&A

Cellular Networks: GenerationsOnce upon a time there was analog cellular communication – 1st G2nd Generation (2G): digital, early 80s, GSM2.5G or GPRS: 140.8 kb/s in theory, 56 kb/s in practice2.75G or E-GPRS or EDGE (Enhanced Data Rates for GSM Evolution): 180 kbps effective3G:

UMTS using WCDMA supports 14Mbps in theory. 384 kbps, or 3.6 Mbps for HSDPA handsets;

• O2, 3, Orange, AT&T, HK, Taiwan, etc.• Different countries use diff. frequencies, thus diff. handsets

CDMA-2000: (2.5G+3G), e.g., China Unicom

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TD-SCDMA at China; to avoid patent fees3.5G: UMTS is being upgraded to High Speed Downlink Packet Access (HSDPA): up to 7.2 Mb/s. 3.99G/4G: the 3GPP Long Term Evolution (LTE) project plans to move UMTS to 4G: 100 Mb/s downlink and 50 Mb/s uplink, using OFDM.

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3GPP: 3rd Generation Partnership Project

Established in Dec. 1998, 3GPP is a collaboration between groups of telco associations from across the g pworld, such as ETSI (Europe), ARIB/TTC (Japan), China, North America, South Korea, etc. Its aim it to make a globally applicable 3G mobile phone system specification within the scope of the ITU’s International Mobile Telecommunications (IMT)-2000 project.

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It evolves current GSM systems. Note: different from 3GPP2, which is another 3G technology based on IS-95 (CDMA), commonly known as CDMA2000.

Standard ReleasesVersion Released

atDescription

Release 98 1998 This and earlier releases specify pre-3G GSM networksp y p

Release 99 2000 Q1 Specified the first UMTS 3G networks, incorporating a CDMA air interface

Release 4 2001 Q2 Added features including an all-IP Core Network

Release 5 2002 Q1 Introduced IMS and HSDPA

Release 6 2004 Q4 Integrated operation with Wireless LAN networks

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Release 7 2007 Q4 Performance improvement

Release 8Release 9

Mar. 2009Dec. 2009

LTE, All-IP Network (SAE). SAES Enhancements, Wimax and LTE/UMTS Interoperability

Release 10 In progress

LTE Advanced

From wikipedia

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LTE-advanced Proposals

Various concepts for Relay Nodes UE Dual TX antenna solutions for SU-MIMO and diversity MIMO Scalable system bandwidth exceeding 20 MHz Potentially up to Scalable system bandwidth exceeding 20 MHz, Potentially up to 100MHzLocal area optimization of air interface Nomadic / Local Area network and mobility solutions Flexible Spectrum Usage Cognitive Radio Automatic and autonomous network configuration and operation

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g pEnhanced precoding and forward error correction Interference management and suppression Asymmetric bandwidth assignment for FDD Hybrid OFDMA and SC-FDMA in uplink UL/DL inter eNB coordinated MIMO

From wikipedia

LTE vs WiMAX: Air interface

LTE WiMAX

Duplexing methodFDD and TDD b FDD f

TDD primary profile but FDD ifi d

Duplexing methodbut FDD focus FDD specified too

MIMO mode Diversity/SM/CSM Diversity/SM/CSM

System Bandwidth Scalable: 1.25 ~ 20 MHz Scalable: 3.5 ~ 10 (20) MHz

Modulation 64QAM/16QAM/QPSK 64QAM/16QAM/QPSK

FFT 128 ~ 2048 points 128 ~ 1024 (2048) points

Downlink Access OFDMA OFDMA

Uplink Access SC-FDMA OFDMA

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Uplink Access SC-FDMA OFDMA

Frame Length 0.5ms 5 ms

Source: D. Pulley of Picochip

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Less obvious at first glance

Mobile WiMAX 20MHz is coming!LTE has two TDD modes with different frame structures:

pressure is on to reduce on a single one “TDSCDMA successor mode”pressure is on to reduce on a single one TDSCDMA successor modethis may pre-empt natural selection and resultant could go head to head with WiMAX TDD profile

SC-FDMA in the Uplink?WiMAX OFDMA has a peak-mean ratio of approx 10dBLTE SC-FDMA has lower peak-mean ratio: approx 5dB

∴ LTE terminal battery life should be betterHigh speed packet data rate claims:

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High speed packet data rate claims:regardless of air interface, divide the theory or marketing by 3 for deployable peak base station throughputs for wide area coverage

Source: D. Pulley of Picochip

Over the next 5 yearsHSPA builds on existing 2G/3G deployments, licenses and roaming, and will account for majority of mobile wireless networksMobile WiMAX can capture niche market dependent on Mobile WiMAX can capture niche market dependent on spectrum availability, proof of performance (Sprint-Nextel)Initial coverage limited deployments give HSPA advantage in CAPEX and OPEX and therefore capital required for launch and NPVLower cost of equipment will not be significant factorImportant to consider other areas such as mobility, latency, services to be offered revenue streams and overall “eco

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services to be offered, revenue streams, and overall eco-system”

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Longer Term Perspective

Improvements in technology performance and resulting link budget (e.g. 802.16m) can give advantage to WiMAX particularly for Greenfield operators – but LTE will have advantage of 3GPP h iheritageLater capacity limited scenarios are more favourable to mobile WiMAX and LTE – mainly in urban areas – but greater competition from e.g. WiFi hotspots3GPP and 3GPP2 networks migrate towards OFDMA technology (e.g. LTE, CDMA Rev. C)This may lead to further market consolidation, depending on

d f LTE/R C d f bil WiMAX

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speed of LTE/Rev. C and success of current mobile WiMAX deployments

Who will eventually win? Who knows!

Comparison

WiMAX

Net o k

WiFi

LargeCoverage

NetworkSimplicity

BroadBand

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3G /HSDPA

QoSFull Mobility Security

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Wireless Technology Positioning

Mobility / Range

GSMGPRS

EDGEWalk

Vehicle

Pedestrian

High Speed

VehicularRural

VehicularUrban

Nomadic

WiMAX with limited mobility

Flash‐OFDM 

UMTS

HSDPAIEEE

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Data rates

10

Mbps

0.1

IEEE802.16d

1 100

WLAN(IEEE 802.11x)

DECT

Bluetooth

EDGE

Fixed

W

IndoorPersonal Area

Fixed urban

Nomadic IEEE802.16e

Capacity

Agenda

Wireless LAN (Local Area Networks)Wireless MAN: WiMAX (IEEE 802.16)Mobile Cellular Systems3GPP LTE (Long Term Evolution)Femto cell and Mobility

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Q&A

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Smartphones

Windows Mobile Based: 12% of the market, supports UMTS, WiFi.Symbian Based: 65% of the market, Nokia, Sony Ericsson, support 3G.RIM OS Based: 11% of the market, Blackberry (not currently 3G capable to save battery, with the small exception)Mac OS-like iPhone-OS Based: 7% of the market

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Mac OS like iPhone OS Based: 7% of the market. Apple's iPhone (using EDGE)

Femto CellAlso called Access Point Base StationNo dual-mode handset needed, existing handset is fine.A femto cell is a small cellular base station, typically for indoors, especially where access would otherwise be limited or unavailable. The femtocell incorporates the functionality of a typical base station but extends it to allow a simpler, self contained deploymentAlthough much attention is focussed on UMTS, the concept is applicable to other network technologies, such as GSM, CDMA2000, TD-SCDMA, WiMAX. Attractions to mobile operators: to improve both coverage and

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p p gcapacity, especially indoors.

There may also be opportunity for new services and reduced cost.

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Femto Cell Network Arch.

Femto Cell BS

Internet

Macro Cell BS

Macro NetworkBroadband Router

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Mobile OperatorCore Network

Internet

Tunnel 

Example Scenario

Nation WideNation WideNetworkNetwork(Cellular)(Cellular)

Home Home NetworkNetwork(WiFi)(WiFi)

Office NetworkOffice Network(Multiple (Multiple WiFisWiFis))

City WideCity WideNetworkNetwork(WiMAX)(WiMAX)

88Switch Switch automaticallyautomatically and and seamlesslyseamlesslyfrom one network to anotherfrom one network to another

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Contact, Q&A

Dr Kun YangSchool of Comp. Science & Electronic Engineering (CSEE),University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK

Email: kunyang@essex.ac.ukhttp://privatewww.essex.ac.uk/~kunyang/

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