3G Systems

3 G SYSTEMS3 G SYSTEMS

3G or IMT-20003G or IMT-2000

• The 3G features:– Provision of multirate services– Packet data– A user-dedicated pilot for a coherent uplink– An additional DL pilot channel for beam forming– Intercarrier handover– Fast power control– Multiuser detection

• IMT-2000 has published a minimum performance requirement of a 3G wireless system, which is for both circuit-switched (CS) and packet-switched (PS) data:– Data rate of 144 kbps in the vehicular environment– Data rate of 384 kbps in the pedestrian

environment– Data rate of 2 Mbps in the fixed indoor and pico cell

environment

3G or IMT-20003G or IMT-2000

Near-far EffectNear-far Effect

• Traditionally single-user receiver is known suffering from the so-called near-far problem, where a near-by or strong signal source may block the signal reception of far-away or weak user(s).

• The near-far is more serious in CDMA-liked wireless multi-user communication systems. And multiuser detection techniques can help the receiver solve this problem

• Multiuser detection is one of the receiver design technology for detecting desired signal(s) from interference and noise.

• Consider a receiver and two transmitters, one close to the receiver, the other far away. If both transmitters transmit simultaneously and at equal powers, then due to the inverse square law the receiver will receive more power from the nearer transmitter

• Since one transmission's signal is the other's noise the signal-to-noise ratio (SNR) for the farther transmitter is much lower

• This makes the farther transmitter more difficult, if not impossible, to understand


• If the nearer transmitter transmits a signal that is orders of magnitude higher than the farther transmitter then the SNR for the farther transmitter may be below detectability and the farther transmitter may just as well not transmit. This effectively jams the communication channel.

• In short, the near-far problem is one of detecting or filtering out a weaker signal amongst stronger signals.


Pilot ChannelPilot Channel

• Pilot Channel/Signal– provides a phase reference for coherent

demodulation, and provides a means for signal strength comparisons between base stations for determining when to hand off.

Why standardization?Why standardization?

• standardization important because interworking is necessary:– Applications across the network– Equipment produced by different companies– Networks of different operators

• hence it is not a good idea for everybody to develop their own protocols / architectures

• Network Experts sit together develop and standardize the technology simultaneously

• What needs to be standardized? the "Essential What":– basic architecture– functionality of essential network elements– protocols and protocol stacks– interfaces– information storage– Everything else related to interworking


• What needs not be standardized?• the "How" and everything not essential:

– internal operation of network elements– intradomain solutions not related to core

functionality– e.g. intra-domain resource management

• Equipment vendors / operators have to come up with own solution for things not standardized


Wide band CDMAWide band CDMA• In the standardization forums, WCDMA technology has

emerged as the most widely adopted third generation air interface

• Its specification has been created in 3GPP (the 3rd Generation Partnership Project), which is the joint standardization project of the standardization bodies from Europe, Japan, Korea, the USA and China

• Within 3GPP, WCDMA is called UTRA (Universal Terrestrial Radio Access) FDD (Frequency Division Duplex) and TDD (Time Division Duplex), the name WCDMA being used to cover both FDD and TDD operation.

W-CDMA Contd…W-CDMA Contd…

• WCDMA is a wideband Direct-Sequence Code Division Multiple Access (DS-CDMA) system, i.e. user information bits are spread over a wide bandwidth by multiplying the user data with quasi-random bits (called chips) derived from CDMA spreading codes.

• In order to support very high bit rates (up to 2 Mbps), the use of a variable spreading factor and multicode connections is supported.

• The chip rate of 3.84 Mcps leads to a carrier bandwidth of approximately 5 MHz.

• DSCDMA systems with a bandwidth of about 1 MHz, such as IS-95, are commonly referred to as narrowband CDMA systems

• The inherently wide carrier bandwidth of WCDMA supports high user data rates and also has certain performance benefits, such as increased multipath diversity


Advantages of using WCDMAAdvantages of using WCDMA

• Multiple access capability. Because all users have different spreading codes, which do not ideally cross-correlate too much, several users can coexist in the same frequency band.

• Protection against multipath interference. Multipath interference is a result of reflections and diffractions in the signal path. The various component signals may be interference to each other. A spread spectrum CDMA signal can resist the multipath interference if the spreading codes used have good autocorrelation properties.

Advantages of using WCDMAAdvantages of using WCDMA• Good jamming resistance. Because the power

spectral density of the signal is so low and resembles background noise, it is difficult to detect and jam on purpose.

• Privacy. An intruder cannot recover the original signal unless he knows the right spreading code and is synchronized to it.

• Narrowband interference resistance. A wideband signal can resist narrowband interference especially well.

WCDMA supports two basic modes of operation:

• Frequency Division Duplex (FDD)• Time Division Duplex (TDD)


Frequency Division Duplex (FDD)• In the FDD mode, separate 5 MHz carrier frequencies

are used for the uplink and downlink respectively• Each carrier is divided into 10-ms radio frames, and

each frame further into 15 time slots• The UTRAN chip rate is 3.84 Mcps meaning every

second, 3.84 million chips are sent over the radio interface

– A chip is a bit in a code word, which is used to modulate the information signal. Since they represent no information by themselves, we call them chips rather than bits

Frequency Division Duplex (FDD)

• The ratio between the chip rate and the data bit rate is called the spreading factor

• In theory we could have a spreading factor of one, that is, no spreading at all. Each chip would be used to transfer one data bit.

• However, this would mean that no other user could utilize this frequency carrier, and moreover we would lose many desirable properties of wideband spreading schemes.

Frequency Division Duplex (FDD)

• In principle, the spreading factor indicates how large a chunk of the common bandwidth resource the user has been allocated

• For example, one carrier could accommodate at most 16 users, each having a channel with a spreading factor of 16.

• The spreading factors used in UTRAN can vary between 4 and 512. A sequence of chips used to modulate the data bits is called the spreading code. Each user is allocated a unique spreading code.

Time Division Duplex (TDD)

• The TDD mode differs from the FDD mode in that both the uplink and the downlink use the same frequency carrier

• The 15 time slots in a radio frame can be dynamically allocated between uplink and downlink directions, thus the channel capacity of these links can be different

• only one 5 MHz is timeshared between the uplink and downlink

Time Division Duplex (TDD)

• The chip rate of the normal TDD mode is also 3.84 Mcps, but there exists also a “narrow band” version of TDD known as TD-SCDMA

• The carrier bandwidth of TD-SCDMA is 1.6 MHz and the chip rate 1.28 Mcps. TD-SCDMA can potentially have a large market share in China

W-CDMAW-CDMA

• WCDMA supports the operation of asynchronous base stations, so that, unlike in the synchronous IS-95 system, there is no need for a global time reference such as a GPS

• Deployment of indoor and micro base stations is easier when no GPS signal needs to be received

• UMTS is the European member of the IMT2000 family of third generation cellular mobile standards.

• The goal of UMTS is to enable networks that offer true global roaming and to support a wide range of voice, data and multimedia services

Universal Mobile Universal Mobile Telecommunication ServicesTelecommunication Services

UMTS Contd..UMTS Contd..

• Data rates offered by UMTS are:– vehicular - 144 Kbps– pedestrian 384 Kbps– in-building Kbps

• Backward compatibility with 2G networks by utilizing GSM/GPRS network infrastructure

FDD Technical summaryFDD Technical summary• Frequency band:1920 MHz -1980 MHz and 2110 MHz - 2170 MHz

(Frequency Division Duplex) UL and DL• Minimum frequency band required: ~ 2x5MHz• Frequency re-use: 1• Carrier Spacing: 4.4MHz - 5.2 MHz• Modulation: QPSK• Pulse shaping: Root raised cosine, roll-off = 0.22• Receiver: Rake• Chip rate: 3.84 Mcps• Channel coding: Convolutional coding, Turbo code for high rate

data

TDD Technical SummaryTDD Technical Summary

• Frequency band:1900 MHz -1920 MHz and 2010 MHz - 2025 MHz (Time Division Duplex) Unpaired, channel spacing is 5 MHz and raster is 200 kHz. Tx and Rx are not separated in frequency, but by guard period.

• Minimum frequency band required: ~ 5MHz, ~ 1.6MHz with 1.28 Mcps

• Frequency re-use: 1• channel coding: Convolutional coding, Turbo code for

high rate data• Chip rate: 3.84 Mcps or 1.28 Mcps

• 1900-1920 and 2010-2025 MHz Time Division Duplex (TDD, TD/CDMA) Unpaired, channel spacing is 5 MHz and raster is 200 kHz. Tx and Rx are not separated in frequency.

• 1980-2010 and 2170-2200 MHz Satellite uplink and downlink.

Technical SpecsTechnical Specs

UMTS Network ArchitectureUMTS Network Architecture

• The interfaces between the UE and the UTRAN (Uu

interface) and between the UTRAN and the CN (Iu) are open multivendor interfaces


A UMTS network consists of three interacting domains:

• User Equipment (UE):The UE is a mobile that communicates with UTRAN via the air-interface

• UMTS Terrestrial Radio Access Network (UTRAN) : UTRAN provides the air interface access method for the UE

• Core Network (CN):provides switching, routing, and transit for user traffic. It also stores databases and provides network management functions.

User Equipment (UE)User Equipment (UE)

• A UE consists of two parts:– The Mobile Equipment (ME) is a radio terminal

used for communicating over the Uu interface (air-interface).

– The UMTS Subscriber Identity Module (USIM) is a smartcard that stores subscribers’ identity and encryption keys, performs authentication algorithms, and supports subscription information for the ME

UMTS Terrestrial RadioAccess Network (UTRAN)

• A UTRAN consists of two distinct elements: Node B and Radio Network Controller (RNC)

• The main functions of the UTRAN architecture are to:– Support soft handoff and W-CDMA specific radio resource

management– Share and reuse of voice and packet data interfaces (ie. Iu-

CS and Iu-PS)

– Share and reuse of GSM infrastructure– Use ATM as the main transport mechanism within UTRAN

UTRAN Architecture

Radio Network Sub-Systems (RNS)Radio Network Sub-Systems (RNS)

• A UTRAN may consist of one or more Radio Network Sub-Systems (RNS).

• An RNS is a sub-network within UTRAN that consists of one RNC and one or more Node B

• RNCs which belongs to different RNS can be connected to each other via the Iur interface

Node BNode B

• A Node B (logically corresponds to the GSM Base Station) converts data flow between the Iub and Uu interfaces

• Its main duty is to perform the physical layer processing, e.g. modulation, coding, interleaving, rate adaptation, spreading, etc.

Radio Network Controller (RNC)

• An RNC (logically corresponds to the GSM Base Station Controller) controls the radio resources in its domain

• RNC is the service access point for all services UTRAN providing to the Core Network

• It also terminates the Radio Resource Control Protocol (RRC) that defines the messages and procedures between UE and UTRAN.

• The logical function of an RNC is further divided into controlling, serving, and drift

• The controlling RNC administers the Node B for load and congestion control. It also executes admission control and channel code allocation for new radio links to be established by the Node B.

• Mobility management functions such as power control, handoff decision, etc are also handled by the serving RNC. Note that one UE connected to the UTRAN has one and only one SRNC.

• The drift RNC compliments the serving RNC by providing diversity when the UE is in the state of inter-RNC soft handoff (which requires two RNCs).

Radio Network Controller (RNC)

Core Network (CN)Core Network (CN)

• UMTS CN is divided into circuit switched and packet switched domains.

• ATM is the transport mechanism to be used in the UMTS core

• The core network consists of the following elements inherited from the incumbent GSM network:– HLR,MSC/VLR,GMSC, SGSN,GGSN

Home Location RegisterHome Location Register(HLR)(HLR)

• An HLR is a database located in the user’s home system that stores the user’s service profile.

• A service profile is created when a new user subscribes to the system, and remained as long as the subscription is active.

• It consists of information such as user service type and roaming permission etc.

(MSC/VLR)(MSC/VLR)• The co-located MSC/VLR serves as both the

switch and database for the circuit switch service.

• The MSC is used to switch the circuit switch data while the VLR function temporarily hold copies of the visiting users’ service profile.

Gateway MSC (GMSC)Gateway MSC (GMSC)

• It is the gateway that connects the UMTS PLMN with the external circuit switch networks.

• All incoming and outgoing circuit switch connections go through the GMSC

SGSN and GGSNSGSN and GGSN

• SGSN has the similar functionality as MSC/VLR except it handles packet switch connections

• GGSN has the same functionality as that of GMSC except it handles the packet switch connection.

GSM Radio Access Network

UMTS EvolutionUMTS Evolution• Layer 2 between RNC and GGSN not

necessarily ATM based• Flexible RANs

– May attach GSM RAN and GERAN to PS domain GERAN = GSM EDGE Radio Access Network

• Iu Flex– Breaking hierarchical mapping of RNCs to SGSNs

(MSCs)

• HSDPA (High Speed Downlink Packet Access)– Can accommodate peek-rates up to 16 Mb/s– Sustained rates of 1 – 5 Mb/s (depending on cell

size)– 16QAM modulation used in addition to QPSK– Turbo Codes

− Powerful error correcting / encoding scheme suited for low signal-noise ratios

UMTS EvolutionUMTS Evolution

CDMA 2000CDMA 2000

• CDMA2000 is another wireless standard designed to support 3G services as defined by the ITU and its IMT-2000 vision.

• It is evolved from the North American IS-95 CDMA standard.

• CDMA2000 system uses 2.1GHz band and it maintains backward compatibility by allowing current frequency bands of 800, 1800 and 1900 MHz to operate seamlessly.

Cdma2000 Technical summary

• Frequency band: Any existing band• Minimum frequency band required: 1x: 2x1.25MHz,

3x: 3x1.25=3.75• Chip rate: 1x: 1.2288, 3x: 3.6864 Mcps• Maximum user data rate: 1x: 144 kbps now, 307

kbps in the future 1xEV-DO: max 384 kbps - 2.4 Mbps, 1xEV-DV: 4.8 Mbps.

• Modulation: QPSK (downlink) BPSK(uplink)

CDMA Network ArchitectureCDMA Network Architecture

• Besides MS and BTS, the first six elements are the same as in cdmaOne for circuit switched voice and data service; BSC, MSC, HLR, VLR, AC, and IWF.

• The IWF enables circuit-switched data service, and BSC carries out the mobility management.

• The additional two elements are for the purpose of providing packet-switched data service.


• In cdma2000 architecture, mobile station (MS) gain access to a service provider network via the air interface to the Radio Network (RN)

• Access mobility management is achieved using existing air interface procedures that include interactions with Visited Location Registers (VLR) and Home Location Registers (HLR)


Mobile Station (MS)

• The main function of the MS is to establish, maintain, and terminate voice and data connections through the PDSN

• The MS establishes a connection by requesting the appropriate radio resources from the RN. Once the connection is established, the mobile station is responsible for maintaining knowledge of radio resources, buffering packets from the mobile applications when radio resources are not in place or are insufficient to support the flow to the network.

Radio Network (RN)

• The Radio Network consists of two logical components:

• Packet Control Function (PCF) • Radio Resources Control (RRC).

Packet Control Function (PCF)Packet Control Function (PCF)

• The primary function of the PCF is to establish, maintain, and terminate L2 connection to the PDSN. It also communicates with the RRC to request and manage radio resources in order to relay packets to and from the mobile station

• During hard handoff to another RRC, the serving PCF forwards its information to the target PCF to re-establish packet data session to the PDSN

• Finally PCF is responsible for collecting accounting information and forward them to the PDSN

Radio Resources Control (RRC)Radio Resources Control (RRC)

• RRC supports authentication and authorization of the mobile station for radio access.

• It also supports air interface encryption to the mobile station.

Packet Data Serving Node(PDSN)

• Key functionalities of PDSN are:– Routing packets to the IP networks or directly to

the HA is the major effort of PDSN– It assigns dynamic IP addresses and maintains PPP

sessions to the mobile stations– Similar in function to the GGSN (GPRS Gateway

Support Node) that is found in GSM and UMTS networks.

Home Agent (HA)

• The HA is a router that resides on that MS’ home IP network.

• Home Agent (HA) plays a major role in implementing the Mobile IP protocol by redirecting packets to the Foreign Agent (FA), and receive and route reverse tunneled packets from the FA

• HA provides security by authenticating mobile station through Mobile IP registration.

• HA also maintains direct connection with AAA in order to receive provisioning information for subscribers

• This is another router residing in another PDSN.

• When an MS visits a foreign IP network, the FA on the foreign network receives packets forwarded from the HA and delivers them to the MS.

Foreign Agent (FA)

Authentication, Authorization, and Accounting (AAA)• pass authentication requests from the PDSN to the

home IP network, and authorize responses from the home IP network to the PDSN

• Stores accounting information for the MS and provides user profiles and QOS information to the PDSN.

• An AAA server connected to a home IP network authenticates and authorizes the mobile station based on requests from the local AAA.

3G Evolution of CDMA2000 3G Evolution of CDMA2000

• The 3G Evolution of CDMA2000 means the evolution of CDMA 1X to CDMA 1xEV-DO and CDMA2000 1xEV-DV– CDMA2000 1x EV-DO (DO= Data Only) – CDMA2000 1xEV-DV(DV=Data and Voice)

• CDMA2000 1X can double the voice capacity of CdmaOne networks and delivers peak packet data speeds of 307 kbps in mobile environments

Voice Data up to 14.4 Kbps

Voice data up to 115 Kbps

2x increases in voice capacityUp to 307 Kbps packet data on single carrier in downlinkFirst 3G system for any technology worldwide.

Optimized for very high data speed (phase 1).

Up to 2.4Mbps packet data on single carrierIntegrated voice and data (phase 2)Up to 3.08 Mbps.

Thank You!Thank You!

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3G Systems

Technology

Transcript of 3G Systems