umts, wlan and new broadband technologies standards...

UMTS, WLAN and new Broadband Technologies

Standards and Technical Basics

Dr. Dietmar DenglerDFKI GmbH, UMTS-Doit

StandardisationITU (International Telecommunication Union) defines concepts forIMT-2000 (International Mobile Telecommunications at 2000 MHz)• Requirements• Combination of proposals of different regional standardazation boards

IMT-2000 is a family of compatible systems (e.g. wrt. roaming)Multimode devices will have access to all systems two groups have been built

Quelle: TKN TU Berlin, Cornelia Kappler Course UMTS Networks

UMTS standardization in 3GPP

• www.3gpp.org• every member company sends delegates to the organization • standardization process:– standard is what all delegates agree about– delegates represent their companies interests• standardization is organized by mailing lists and at least 6 meetings per

year• standardization topics get a defined end point in order to manage the

process • nearly every year a new release of the UMTS standard is published– first UMTS Release is "R99", then Rel4, Rel5,...• all specifications are available to the public (as opposed to GSM)

Standardization in IETF - Internet Engineering TaskForce

• e.g. IP, TCP, etc.• www.ietf.org• informal organisation of “independent” engineers and researchers • every person can participate on the standardization process– influence is based on technical knowledge, reputation, etc.• standardization according to: “We believe in running code and rough consensus”– only the things which are implemented can be standardized• standardization is organized by mailing lists and at least 3 meetings per

year• standardization topics are dependent upon the interests of the persons

involved • for every topic a special working group• all documents are available to the public

3GPP - IETF cooperation

• 3GPP and IETF are based on different principles– 3GPP defines a complete system (-> cathedral)– IETF works on a protocol one by one (-> bazaar)• but since telecommunication and internet interact more and more, theyhave to cooperate– but IETF does not produce standards „on demand“– 3GPP cannot wait on standards until „someone is interested on it and ishappy about a specific solution“• so, the same people are active in both organizations

History of mobile telecommunications

• 1958 A-Net in Germany: analog, connection initialized by mobile station, switched by hand, no handover, 1971: 11.000 User

• 1972 B-Net in Germany : analog, no handover, connection could also be initialized from conventional telephone network if the user location has been known, 13.000 User

• 1982 Start of GSM-Specification• 1986 C-Netz (1G) in Germany: analog cellular, handover, automatic

localization of mobile station• 1992 Start of GSM (2G): D1 and D2, completely digital, Roaming, data

services possible• 1994 E-Net in Germany: E-Plus, Viag Interkom• 1998 specification of GSM-successor: UMTS as a european proposal for

IMT-2000• 2000 GSM extension (2.5G): HSCSD, GPRS• 2002 Start of UMTS (3G) in test areas• 2005 Start of HSDPA (3,5G) in test areas

C-Netz

GSM

� speech1. Generation (analog)

2. Generation (digital)

GSM/GPRS2.5 Generation (packet data)

3. Generation (Multimedia) UMTS

� speech, SMS, Fax� circuit-switched data

transmission 9,6 kbit/s

� speech� Multimedia services� high-speed data 384

kbit/s (2 Mbit/s peakrate)

� new to GSM: packet-switched data transmission up to 80 kbit/s

PDC

PDC/PDC-P

Hicap

J-TACS

NMT

TACS

IS-95 A« CDMA »

IS-95 B

cdma2000

AMPS

D-AMPS« TDMA », IS-136

UWC-136HSEDGE (GPRS)

IMT-2000: System family

GSM:

GSM/GPRS:

UMTS:

The different generations

Quelle: T-Mobile, Bonn

• completely new radio access technology WCDMA (and TD-CDMA)• Core-Network (Vermittlungsnetz) is an evolution of the

GSM/GPRS-Core-Network• UMTS-GSM Interworking: Roaming and Handover/Cell-Reselection

of CS- and PS-services in both directions• higher bitrates:

– up to 384 Kb/s – compared to 9,6 Kb/s in GSM, and ca. 54 Kb/s in GPRS

• new Multimedia- and Multitasking abilities• extended network security• usage of ATM in the Radio Access Network and for the connection

of the RNCs to CN

Essential Features of UMTS (Release 99)

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UMTS

FDD uplink

FDD downlink

FDD uplink

FDD downlink

TDD TDD

12 packets of 2 x 5 MHz FDD, 5 packets of 1 x 5 MHz TDD

UMTS (frequency band)


Architecture of the UMTS-Network

• Air interface between UE (User Equipment) and Node B of a cell• Node B is physical unit for radio transmission/reception� contains signal processing units for channel coding, modulation, etc.

• Node B´s are connected to RNC (Radio network Controller): management unit for a set of cells, handover control, ciphering, etc.; connects to CN

• CN (Core Network) divided in circuit switched and packet switched domains• connection to external networks• mobility management by VLR (Visitor Location Register) and HLR (Home Location Register)

• packet oriented data (PS-Packet Switched) are processed by SGSN (ServingGPRS Support Node) and GGSN (Gateway GPRS Support Node)

Architecture of the UMTS-Network

UTRAN - UMTS Terrestrial Radio Access Network

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Quelle: UMTSlink.at

Advantages of Softhandover

• less sensitivity against shadowing effects, e.g. by buildings

• less sensitivity against multipath effects, e.g. fading (destructive overlap of waves)

• less frequent service loss on cell change as opposed to hard handover (GSM)

• less signal to noise ratio: usage of different radio paths decreases the probability of interferences of the same kind

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Multiple Access Mode


Frequency Division Multiple Access Time Division Multiple Access

Code Division Multiple Access

• Two modes: FDD (Frequency Division Duplex) and TDD (Time DivisionDuplex)– FDD uses different frequencies in the “paired spectrum” for Uplink

and Downlink– TDD uses same frequency in “unpaired spectrum” for Uplink and

Downlink• FDD-Mode

– Frequency band: Uplink 1920-1980 MHz, Downlink 2110-2170 MHz– Multiple access mode: WCDMA (Wideband Code Division Multiple

Access)– Bandwidth of a channel: ca. 5 MHz

• TDD-Mode– Frequency band: 1900-1920 MHz and 2010-2025 MHz– Multiple access mode: TD-CDMA (Time Division - Code Division

Multiple Access)• UMTS started with FDD. TDD maybe later.

UMTS Air Interface

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CDMA-Principle (UMTS W-CDMA FDD)

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Distinction UMTS FDD vs. TDD

Quelle: Vorl.Mobile CommunicationsII, LMU München, A. Küpper

Realization of CDMA process by Direct Sequence CDMA-Technique

• Multiplication of data stream (Bits) with a user-specific two-valued code sequence (Chips)

• every Bit is therefore mapped on a specific number of chips: Bit stream -> Chip stream

• sending the signals with a high bandwidth compared to the initial datarate

• impressing of a „fingerprint“ -> Spreading code• Spreading factor = broadening factor of the spectrum = number of chips per bit

• transmission of all user signals using the same carrier frequency

Internal change of bit patterns into NRZ-Signals (No Return to Zero)• Bit 1 -> Symbol -1 • Bit 0 -> Symbol +1

coded datarate of 3,84Mchip/s

(-1) * (+1) = "-1"

Sample Coding

Quelle: UMTSlink.at

Spreading processSpreading code ~ „channelisation code“

Signal Spreader

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Bin BS

Rin: Bit Rate des Input-Signals

Beispiel: Rchip= 3,84 Mcps, Rin= 30 kbps, SF=128

Spreading Factor (SF) = Bs/Bin= Rchip/Rin

Rchip: Chip Rate

Transmission Principle of CDMA


Orthogonal variable spreading factor (OVSF) code

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– W-CDMA uses OVSF-codes forspreading

– every code on a branch of the code tree is orthogonal to every code on another branch

– codes on the same branch arenot orthogonal

– W-CDMA uses SF 4 to 512 forDL, and 4 to 256 for UL

– datarate per user can be quickly adapted -> new code with other SF

– UMTS FDD: adaptation possible every 10ms

Process Gain

• Code length responsible for process gain• decoding is always done over the complete chip length • scalar product during decoding provides the „amplified“ values +/-SF• SF corresponds with process gain• „the longer the code the bigger the band spreading and the process gain“

• that means for a CDMA-system:• the transmission of signals with higher SF and therefore lowerdatarate needs less power on the antenna as signals with high datarate

• if the radio reception on the UE is bad and the transmitter power can no more be increased then the reduction of the datarate by a higherSF provides an amplification of the signal, i.e. the failure ratio decreases

• a dynamic process providing more fail-safe communication

Disadvantage of orthogonal Channelization codes

Sample assumption for uplink:signal delay at Node B = 1 Chip

Fatal:initially orthogonal codes are recognized asidentical codes

Downlink problem:if all cells are using the same codetree then failures arise at theborders of the cells

Scrambling codes provide a solution

• Scrambling codes are only used for an orthogonal coding of thecells in DL and of the Ues in UL instead of a usage as a means of spreading

• the length is fixed at 38400 chips, exactly the length of a signal time frame (10ms)

• every time frame is coded by multiplication with the scrambling code

• scrambling codes persist their orthogonality also in theasynchronous case

• cell network planning distributes the codes to the Node Bs• RNC sends info to UE to enable it to generate an uplink-scrambling code

• Basic idea: dynamic optimization of the relationship of

• speech coding to

• channel coding (protection against failures)• the transcoders are a set of speech codecs at their disposal

(AMR 4,75kb/s to AMR 12,2kb/s)• adaptation of the codec to the current interference situation

(for each UE individually) • if the datarate decreases then the process gain increases and

also the coverage of the UE increases (transmitting power decreases which leads to a reduction of interference)

AMR (adaptive multirate) speech transmission

• Maintaining the security concepts of GSM – usage of SIM-Card– authentification of SIM against the net– encryption of the data on the air interface

• Enhanced security of UMTS– mutual authentification of USIM (Universal Subscriber Identity Module)

and net– livetime of temporary keys limited– increasing key length from 64 bit to 128 bit– ciphering on the air interface and between Node B and RNC

• Compatibility of 3G/2G security features: – usuage of USIM for GSM access

Node B

USIM

RNC MSC / SGSN

HLR

Ciphering / Integrity Check

USIM AuthenticationNetwork Authentication

Security in the UMTS network


Mobile and wireless services – Always Best Connected

widearea networks

metropolitan networks

campus networks

buildings

VerticalHandover

HorizontalHandover

Integration of heterogenous fixed and wirelessnetworks with highly different characteristics

Quelle: Vorl. Mobilkommunikation, J. Schiller, FU Berlin

Mobility with WLAN & UMTS

• UMTS provides cost-efficient broadband wide area access• UMTS supports international roaming• UMTS provides integrated accounting• UMTS provides secure network access• WLAN provides wireless high-speed access to existing networks with limited mobility in the area of hot spots

WLAN and UMTS complement each other and will coexist!

Quelle: Farpoint Group

Wireless Evolution

IEEE 802.11 Standards and working groups


Comparison of infrastructure and ad hoc networks


802.11 - Architecture – Infrastructure network

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802.11 - Architecture – Ad hoc network

direct way of communication withrestricted coverage• Station (STA):device with access to the wirelessmedium• Basic Service Set (BSS):group of stations using the same frequency channel

different BSSs can be built byspace multiplexing or by usingdifferent carrier frequencies


WLAN usage in the 2,4GHz band

• no license required for this band, everyone can use it• no regulation of the frequencies• public service -> no protection against tapping• Internationally regulated!

• no manipulation on the transmitter• only „licensed“ antenna

• other usage of the band• micro wave, bluetooth, radar, motion sensors, wireless headphones, etc.

• responsibility: RegTP, ETSI (Europe), ITU (international)

WLAN – coverage 802.11b

Quelle: F. Jondral, Uni Karlsruhe, Inst. Für Nachrichtentechnik

WLAN - Physical Layer DSSS

DSSS (Direct Sequence Spread Spectrum) process• the standard for 802.11b WaveLan• 1, 2, 5.5 and 11 MBit• new devices backwards compatible • bad radio reception involves switching to lower bitrate• 13 channels (Europe). USA: 11 channels• Raster 5 MHz• DSSS Signal is spreaded by Chipping Codes to 22 MHz• max. 3 non-overlapping channels

WLAN - Control Layer• application of specific collision avoidance algorithms• AP has control on access to the transmitting medium

WLAN – channel allocation 802.11b


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HSDPA (Highspeed downlink packet access)

• enhancements to the WCDMA-based UMTS-technology• WCDMA-Networks are using e.g. Fast-Power-Control in order to

guarantee quality of service of a connection • HSDPA uses the realtime adaptation of modulations (QPSK, 16QAM)

and codings dependent upon „Channel Quality Indicator“ data of the UE

• new transport channel type supports up to 15 multicodes per channel: exclusively to one user or shared between at most 4 users

• length of transmission window reduced to 2ms • packet delivery planning is done by NodeB instead of RNC• Downlink up to 2-3Mbit/s (theoretically 10-14 Mbit/s), Uplink 128Kbit/s• low investment (mostly software) provides high capacity

improvement• HSDPA backwards compatible to WCDMA-UMTS

• WiMAX Forum 2003 established by10 companies, today mor than 150 members

• Intel drives the development(WiMAX air interface will be integrated into next Centrinotechnology)

• Marketing, certification, development of system profiles forIEEE 802.16, currently IEEE 802.16-2004 (once 802.16d)

• 802.16e for mobile access

• Adaptive modulation and coding

• Adaptation of the coding to the signal to noise ratio

Worldwide Interoperability for Microwave Access (WiMAX)

Quelle: Intel

OFDMA (Orthogonal Frequency Division Multiple Access)

• segmentation of a fast bit stream into several slow bit streams which will be transmitted over different frequencies simultaneously

• ‘Long’ symbol duration is more robust against multipath reception• minus on bandwidth is compensated by overlapping of the frequency

bands, i.e. parallel transmission• broad channel segmented into narrow subcarrier• Symbols on the subcarriers are orthogonal to each other• single subcarriers can be assigned to different users and are not fixed

in the spectrum (frequency hopping)

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Abkürzungen II

umts, wlan and new broadband technologies standards...

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