a tutorial on multiple access technologies for beyond 3g mobile networks

A Tutorial on A Tutorial on Multiple Access Multiple Access

Technologies for Technologies for Beyond 3G Mobile Beyond 3G Mobile

NetworksNetworks

Speaker: Chen-Nien TsaiSpeaker: Chen-Nien TsaiAuthors: A. Jamalipour Authors: A. Jamalipour et al.et al.IEEE Communications Magazine,IEEE Communications Magazine, February 2005 February 2005

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OutlineOutline

• IntroductionIntroduction

• A Review of Multiple Access A Review of Multiple Access TechnologiesTechnologies

• Key Features of 3G Multiple Access Key Features of 3G Multiple Access TechnologiesTechnologies

• Multiple Access Technologies For Multiple Access Technologies For B3G SystemsB3G Systems

• ConclusionsConclusions

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Introduction (1/3)Introduction (1/3)

• Beyond third-generation (B3G) wireless Beyond third-generation (B3G) wireless cellular systems...cellular systems...– can achieve high-data-rate transmission.can achieve high-data-rate transmission.– are capable of delivering multiple services tare capable of delivering multiple services t

o users.o users.– should provide services comparable to thosshould provide services comparable to thos

e offered by wired networks.e offered by wired networks.– Multimedia, VoIP, network games, etc.Multimedia, VoIP, network games, etc.

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• One of the main issues involved in One of the main issues involved in the development of B3G systems is the development of B3G systems is the choice of the choice of multiple accessmultiple access (MA) (MA) technology.technology.

• The choice of MA technique could The choice of MA technique could significantly enhance or lower the significantly enhance or lower the service quality.service quality.

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• The existing MA techniques used in The existing MA techniques used in 2G/3G systems are basically suitable 2G/3G systems are basically suitable for voice communications but not for for voice communications but not for burst data traffic.burst data traffic.

• Therefore, the need to develop new Therefore, the need to develop new MA techniques for B3G becomes MA techniques for B3G becomes imperative.imperative.

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OutlineOutline






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A Review of Multiple Access A Review of Multiple Access TechnologiesTechnologies• A telecommunications network has finite A telecommunications network has finite

resources (bandwidth).resources (bandwidth).

• More than one user will access such More than one user will access such limited bandwidth.limited bandwidth.

• An MA scheme must to control the share An MA scheme must to control the share of bandwidth among multiple usersof bandwidth among multiple users– Everyone can use services.Everyone can use services.– No single user spends all available No single user spends all available

resources.resources.

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What is Multiple Access? What is Multiple Access?

• The techniques that enable multiple The techniques that enable multiple users to share limited network users to share limited network resources efficiently.resources efficiently.

• Four basic MA schemesFour basic MA schemes– FDMA (Frequency-Division MA)FDMA (Frequency-Division MA)– TDMA (Time-Division MA)TDMA (Time-Division MA)– CDMA (Code-Division MA)CDMA (Code-Division MA)– SDMA (Space-Division MA)SDMA (Space-Division MA)

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A Review of Multiple Access TechnologiesA Review of Multiple Access Technologies

FDMA (1/2)FDMA (1/2)

• Dividing the Dividing the available frequency available frequency spectrumspectrum into some into some frequency frequency channelschannels..

• Each channel occupies a portion of Each channel occupies a portion of total available bandwidth and is given total available bandwidth and is given to a single user.to a single user.

• Multiple users using separate Multiple users using separate frequency channels could access the frequency channels could access the same system.same system.

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FDMA (2/2)FDMA (2/2)

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• Dividing the Dividing the time axistime axis into portions or into portions or time slotstime slots, each assigned to a single , each assigned to a single user to transmit data information.user to transmit data information.

• Frame and multiframe conceptFrame and multiframe concept– A user could send a large data file within A user could send a large data file within

time slots of periodical frames.time slots of periodical frames.– Data from a single user always sits in Data from a single user always sits in

the same time slot position of a frame.the same time slot position of a frame.


TDMA (1/3)TDMA (1/3)

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• TDMA has kept its dominance in wired TDMA has kept its dominance in wired and wireless systems for many years.and wireless systems for many years.– 2G (GSM) and 2.5G (GPRS) adopted 2G (GSM) and 2.5G (GPRS) adopted

TDMA as their MA scheme.TDMA as their MA scheme.

• In a TDMA system, the used system In a TDMA system, the used system bandwidth is usually divided in to bandwidth is usually divided in to smaller frequency channels.smaller frequency channels.– Hybrid FDMA/TDMA systemHybrid FDMA/TDMA system

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Hybrid FDMA/TDMAHybrid FDMA/TDMA

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CDMA (1/3)CDMA (1/3)

• In both FDMA and TDMA techniques In both FDMA and TDMA techniques the number of channels or time slots the number of channels or time slots is fixed.is fixed.– By increasing the number of services By increasing the number of services

from simple voice to more burst data from simple voice to more burst data transmissions, it lack of efficiency in transmissions, it lack of efficiency in utilizing the scarce spectrum.utilizing the scarce spectrum.

– Hence, CDMA schemes started to come Hence, CDMA schemes started to come into commercial systems.into commercial systems.

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• In a CDMA system…In a CDMA system…– Each user is assigned a Each user is assigned a spreading codespreading code..– User’s information is spread into a much User’s information is spread into a much

wider spectrum using a high clock (wider spectrum using a high clock (chipchip) rate.) rate.– It is possible to send multiple users’ It is possible to send multiple users’

information on the same frequency spectrum.information on the same frequency spectrum.

• CDMA is an MA scheme that has no fixed CDMA is an MA scheme that has no fixed maximum number of users. (in theory)maximum number of users. (in theory)

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SDMA (1/2)SDMA (1/2)

• In SDMA, users are separated in a In SDMA, users are separated in a spatial way.spatial way.

• Generally an adaptive array antenna Generally an adaptive array antenna technique is adopted.technique is adopted.

• One disadvantage is the difficulty of One disadvantage is the difficulty of separating two users who are placed separating two users who are placed near the base station. near the base station.

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SDMA (2/2)SDMA (2/2)

Time

Frequency

Space

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OutlineOutline






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Key Features of 3G Multiple Key Features of 3G Multiple Access Technologies (1/3)Access Technologies (1/3)• International Mobile TelecommunicatioInternational Mobile Telecommunicatio

ns-2000 (ns-2000 (IMT-2000IMT-2000) is the “) is the “umbrella speumbrella specificationcification” of all 3G systems.” of all 3G systems.– IMT Direct SpreadIMT Direct Spread (DS- (DS-CDMACDMA, aka UTRA-FD, aka UTRA-FD

D)D)– IMT Time CodeIMT Time Code (TD- (TD-CDMACDMA, aka UTRA-TDD), aka UTRA-TDD)– IMT MulticarrierIMT Multicarrier (MC- (MC-CDMACDMA, aka CDMA 2000), aka CDMA 2000)– IMT Single Carrier (SC-IMT Single Carrier (SC-CDMACDMA, aka UWC-136), aka UWC-136)– IMT Frequency Time (IMT-FT, aka DECT)IMT Frequency Time (IMT-FT, aka DECT)

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Key Features of 3G Multiple Access TechnologiesKey Features of 3G Multiple Access Technologies

IMT-2000 FamilyIMT-2000 Family

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Key Features of 3G Multiple Key Features of 3G Multiple Access Technologies (2/3)Access Technologies (2/3)• IMT-2000 has five standard, four of IMT-2000 has five standard, four of

which are based on CDMA.which are based on CDMA.– CDMA is a promising access technology for CDMA is a promising access technology for

high-data-rate wireless communications.high-data-rate wireless communications.

• The advantages of CDMAThe advantages of CDMA– Tolerance to the effects of channel fading.Tolerance to the effects of channel fading.– Efficient frequency reuse.Efficient frequency reuse.– Soft handover among cells is achievable.Soft handover among cells is achievable.

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Key Features of 3G Multiple Key Features of 3G Multiple Access Technologies (3/3)Access Technologies (3/3)• Near-far problemNear-far problem

– A signal transmitted by a user who is far A signal transmitted by a user who is far from the base station can easily be from the base station can easily be blocked by a signal from a nearby user.blocked by a signal from a nearby user.

– Calls for a power control technique.Calls for a power control technique.

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UMTSUMTS

• Stands for Stands for Universal Mobile Universal Mobile Telecommunication SystemTelecommunication System..

• It’s the most important one of the 3G It’s the most important one of the 3G telecommunications systemstelecommunications systems

• Two modes of operation in the Two modes of operation in the UMTS UMTS terrestrial radio accessterrestrial radio access (UTRA) (UTRA)– Time-division duplex (UTRA-TDD)Time-division duplex (UTRA-TDD)– Frequency-division duplex (UTRA-FDD)Frequency-division duplex (UTRA-FDD)

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IMT Direct SpreadIMT Direct Spread

• The most important IMT-2000 system.The most important IMT-2000 system.

• It’s being developed by 3GPP It’s being developed by 3GPP consortiumconsortium– UTRA-FDDUTRA-FDD

• UTRA-FDD is purely a CDMA-base UTRA-FDD is purely a CDMA-base system, but can be considered a system, but can be considered a combination of CDMA with FDMA.combination of CDMA with FDMA.

• UTRA-FDD separating frequency UTRA-FDD separating frequency spectrum for downlink and uplink.spectrum for downlink and uplink.

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IMT Time Code (1/4)IMT Time Code (1/4)

• It’s also being developed by 3GPP It’s also being developed by 3GPP consortiumconsortium– UTRA-TDDUTRA-TDD

• Can be considered a combination of Can be considered a combination of CDMA with TDMA.CDMA with TDMA.

• UTRA-TDD using the same spectrum UTRA-TDD using the same spectrum for both uplink and downlink for both uplink and downlink channels.channels.

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• For both UTRA-TDD and UTRA-FDDFor both UTRA-TDD and UTRA-FDD– Each carrier has a bandwidth of 5MHz.Each carrier has a bandwidth of 5MHz.– Chip rate is 3.84 McpsChip rate is 3.84 Mcps– Each carrier is divided into 10-ms radio framEach carrier is divided into 10-ms radio fram

es, and each frame further into 15 time slots.es, and each frame further into 15 time slots.

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• AdvantagesAdvantages– It’s possible to flexibly arrange different It’s possible to flexibly arrange different

numbers of time slots on uplink and downlink.numbers of time slots on uplink and downlink.– It can change the ratio of uplink and downlink It can change the ratio of uplink and downlink

capacity dynamically.capacity dynamically.– This concept would be necessary for B3G This concept would be necessary for B3G

systems where burst data traffic becomes the systems where burst data traffic becomes the dominant part.dominant part.

– Appropriate to share power control Appropriate to share power control information.information.

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IMT Multicarrier (1/4)IMT Multicarrier (1/4)• The 3GPP2 promotes the CDMA2000 The 3GPP2 promotes the CDMA2000

system.system.

• In the world or IMT-2000, this In the world or IMT-2000, this proposal is known as IMT-MC.proposal is known as IMT-MC.

• CDMA2000 is backward compatible CDMA2000 is backward compatible with IS-95 systems, which is a with IS-95 systems, which is a standard for 2G system.standard for 2G system.

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IMT Multicarrier (2/4)IMT Multicarrier (2/4)• The chip rate in CDMA2000 will be a multThe chip rate in CDMA2000 will be a mult

iple of 1.2288 Mcps.iple of 1.2288 Mcps.– The maximum rate will be 3x (3.6864 Mcps) iThe maximum rate will be 3x (3.6864 Mcps) i

n the first phase.n the first phase.• The original goal was to have a system wThe original goal was to have a system w

ith three narrowband (1.25 MHz) carriers.ith three narrowband (1.25 MHz) carriers.– Same bandwidth as an IS-95 carrierSame bandwidth as an IS-95 carrier

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IMT Multicarrier (3/4)IMT Multicarrier (3/4)

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IMT Multicarrier (4/4)IMT Multicarrier (4/4)• Advantages over DS-CDMAAdvantages over DS-CDMA

– Suitable for frequency-selective fading chanSuitable for frequency-selective fading channels.nels.

– Low interference and less outband radiatioLow interference and less outband radiation.n.

• The disadvantagesThe disadvantages– Require a high linear amplifier that causes iRequire a high linear amplifier that causes i

nefficient power consumption.nefficient power consumption.

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OutlineOutline






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Multiple Access Multiple Access Technologies For B3G Technologies For B3G SystemsSystems• Main feature required in B3G systemsMain feature required in B3G systems

– High-data-rate transmission. (10 Mbps or moHigh-data-rate transmission. (10 Mbps or more)re)

• It is difficult to introduce an actual compIt is difficult to introduce an actual compensation method for the fading effect of ensation method for the fading effect of every user and every subchannel.every user and every subchannel.

• The current CDMA schemes unfortunatelThe current CDMA schemes unfortunately do not satisfy the requirement of B3G.y do not satisfy the requirement of B3G.

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Multiple Access Technologies for B3G systemsMultiple Access Technologies for B3G systems

Advanced MA Schemes Advanced MA Schemes (1/3)(1/3)• Multicarrier DS-CDMA (MC/DS-CDMA)Multicarrier DS-CDMA (MC/DS-CDMA)

– Combination of MC-CDMA and DS-CDMACombination of MC-CDMA and DS-CDMA– Can achieve very-high-data-rate transmissioCan achieve very-high-data-rate transmissio

n with the advantages of both schemes.n with the advantages of both schemes.– Requires an amplifier with high linearity, whRequires an amplifier with high linearity, wh

ich results in power inefficiency. (similar to ich results in power inefficiency. (similar to MC-CDMA)MC-CDMA)

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Advanced MA Schemes Advanced MA Schemes (2/3)(2/3)• TDD-CDMATDD-CDMA

– A modified version of TD-CDMA.A modified version of TD-CDMA.– Better frequency efficiency than UTRA-Better frequency efficiency than UTRA-

FDD.FDD.– Can easily achieve asymmetric Can easily achieve asymmetric

transmissions.transmissions.– Will become a major MA scheme for B3G Will become a major MA scheme for B3G

system.system.

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Advanced MA Schemes Advanced MA Schemes (3/3)(3/3)• Orthogonal frequency-division MA Orthogonal frequency-division MA

(OFDMA)(OFDMA)– Has attracted much attention in the IEEE Has attracted much attention in the IEEE

802.16 standard.802.16 standard.– The concept is essentially the same as The concept is essentially the same as

FDMA, but it has some advantages.FDMA, but it has some advantages.– Transmission with different rates among Transmission with different rates among

users is available according to each users is available according to each user’s requirement.user’s requirement.

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OutlineOutline






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ConclusionsConclusions

• The technologies for MA schemes The technologies for MA schemes that have been adopted in 3G that have been adopted in 3G systems are examined.systems are examined.

• None of the existing MA techniques None of the existing MA techniques would be able to satisfy the would be able to satisfy the transmission criteria in B3G system.transmission criteria in B3G system.

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ConclusionsConclusions

• Next-generation networks will be develoNext-generation networks will be developed through good management and a cped through good management and a combination of the advanced MA technolombination of the advanced MA technologies, rather than the development of nogies, rather than the development of new schemes.ew schemes.

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ReferencesReferences

• A. Jamalipour, T. Wada, and T. Yamazato, "A Tutorial A. Jamalipour, T. Wada, and T. Yamazato, "A Tutorial on Multiple Access Technologies for Beyond 3G Mobile on Multiple Access Technologies for Beyond 3G Mobile Networks," Networks," IEEE Communications MagazineIEEE Communications Magazine, vol. 43, n, vol. 43, no. 2, Feb. 2005, pp. 110-117.o. 2, Feb. 2005, pp. 110-117.

• Juha Korhonen, Juha Korhonen, Introduction to 3G Mobile CommunicIntroduction to 3G Mobile Communications 2nd ed.ations 2nd ed., Artech House, 2003., Artech House, 2003.

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B3G MA schemesB3G MA schemes

• L.-L. Yang and L. Hanzo, “Multicarrier DS-CDMA: A MuL.-L. Yang and L. Hanzo, “Multicarrier DS-CDMA: A Multiple Access Scheme for Ubiquitous Broadband Wirelltiple Access Scheme for Ubiquitous Broadband Wireless Communications,” ess Communications,” IEEE Communications MagaziIEEE Communications Magazinene, vol. 41, no. 10, Oct. 2003, pp. 116-124., vol. 41, no. 10, Oct. 2003, pp. 116-124.

• R. Esmailzadeh and M. Nakagawa, “TDD-CDMA for thR. Esmailzadeh and M. Nakagawa, “TDD-CDMA for the 4th Generation of Wireless Communications,” e 4th Generation of Wireless Communications,” IEEE IEEE Communications MagazineCommunications Magazine, vol. 41, no. 8, Aug. 2003, p, vol. 41, no. 8, Aug. 2003, pp. 8-15.p. 8-15.

• P. Xia, S. Zhou, and G. B. Giannakis, “Bandwidth- and P. Xia, S. Zhou, and G. B. Giannakis, “Bandwidth- and power-Efficient Multicarrier Multiple Access,” power-Efficient Multicarrier Multiple Access,” IEEE TrIEEE Trans. Communans. Commun., vol. 51, no.11, Nov. 2003, pp. 1828-37.., vol. 51, no.11, Nov. 2003, pp. 1828-37.

a tutorial on multiple access technologies for beyond 3g mobile networks

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