A Tutorial on Multiple Access Technologies for Beyond 3G Mobile Networks Speaker: Chen-Nien Tsai Authors: A. Jamalipour et al. IEEE Communications Magazine, February 2005

2005/5/102 Outline Introduction Introduction A Review of Multiple Access Technologies A Review of Multiple Access Technologies Key Features of 3G Multiple Access Technologies Key Features of 3G Multiple Access Technologies Multiple Access Technologies For B3G Systems Multiple Access Technologies For B3G Systems Conclusions Conclusions

2005/5/103 Introduction (1/3) Beyond third-generation (B3G) wireless cellular systems... Beyond third-generation (B3G) wireless cellular systems... –can achieve high-data-rate transmission. –are capable of delivering multiple services to users. –should provide services comparable to those offered by wired networks. –Multimedia, VoIP, network games, etc.

2005/5/104 Introduction (2/3) One of the main issues involved in the development of B3G systems is the choice of multiple access (MA) technology. One of the main issues involved in the development of B3G systems is the choice of multiple access (MA) technology. The choice of MA technique could significantly enhance or lower the service quality. The choice of MA technique could significantly enhance or lower the service quality.

2005/5/105 Introduction (3/3) The existing MA techniques used in 2G/3G systems are basically suitable for voice communications but not for burst data traffic. The existing MA techniques used in 2G/3G systems are basically suitable for voice communications but not for burst data traffic. Therefore, the need to develop new MA techniques for B3G becomes imperative. Therefore, the need to develop new MA techniques for B3G becomes imperative.

2005/5/106 Outline Introduction Introduction A Review of Multiple Access Technologies A Review of Multiple Access Technologies Key Features of 3G Multiple Access Technologies Key Features of 3G Multiple Access Technologies Multiple Access Technologies For B3G Systems Multiple Access Technologies For B3G Systems Conclusions Conclusions

2005/5/107 A Review of Multiple Access Technologies A telecommunications network has finite resources (bandwidth). A telecommunications network has finite resources (bandwidth). More than one user will access such limited bandwidth. More than one user will access such limited bandwidth. An MA scheme must to control the share of bandwidth among multiple users An MA scheme must to control the share of bandwidth among multiple users –Everyone can use services. –No single user spends all available resources.

2005/5/108 What is Multiple Access? The techniques that enable multiple users to share limited network resources efficiently. The techniques that enable multiple users to share limited network resources efficiently. Four basic MA schemes Four basic MA schemes –FDMA (Frequency-Division MA) –TDMA (Time-Division MA) –CDMA (Code-Division MA) –SDMA (Space-Division MA)

2005/5/109 A Review of Multiple Access Technologies FDMA (1/2) Dividing the available frequency spectrum into some frequency channels. Dividing the available frequency spectrum into some frequency channels. Each channel occupies a portion of total available bandwidth and is given to a single user. Each channel occupies a portion of total available bandwidth and is given to a single user. Multiple users using separate frequency channels could access the same system. Multiple users using separate frequency channels could access the same system.

2005/5/1010 A Review of Multiple Access Technologies FDMA (2/2)

2005/5/1011 Dividing the time axis into portions or time slots, each assigned to a single user to transmit data information. Dividing the time axis into portions or time slots, each assigned to a single user to transmit data information. Frame and multiframe concept Frame and multiframe concept –A user could send a large data file within time slots of periodical frames. –Data from a single user always sits in the same time slot position of a frame. A Review of Multiple Access Technologies TDMA (1/3)

2005/5/1012 A Review of Multiple Access Technologies TDMA (2/3)

2005/5/1013 A Review of Multiple Access Technologies TDMA (3/3) TDMA has kept its dominance in wired and wireless systems for many years. TDMA has kept its dominance in wired and wireless systems for many years. –2G (GSM) and 2.5G (GPRS) adopted TDMA as their MA scheme. In a TDMA system, the used system bandwidth is usually divided in to smaller frequency channels. In a TDMA system, the used system bandwidth is usually divided in to smaller frequency channels. –Hybrid FDMA/TDMA system

2005/5/1014 A Review of Multiple Access Technologies Hybrid FDMA/TDMA

2005/5/1015 A Review of Multiple Access Technologies CDMA (1/3) In both FDMA and TDMA techniques the number of channels or time slots is fixed. In both FDMA and TDMA techniques the number of channels or time slots is fixed. –By increasing the number of services from simple voice to more burst data transmissions, it lack of efficiency in utilizing the scarce spectrum. –Hence, CDMA schemes started to come into commercial systems.

2005/5/1016 A Review of Multiple Access Technologies CDMA (2/3) In a CDMA system … In a CDMA system … –Each user is assigned a spreading code. –User ’ s information is spread into a much wider spectrum using a high clock (chip) rate. –It is possible to send multiple users ’ information on the same frequency spectrum. CDMA is an MA scheme that has no fixed maximum number of users. (in theory) CDMA is an MA scheme that has no fixed maximum number of users. (in theory)

2005/5/1017 A Review of Multiple Access Technologies CDMA (3/3)

2005/5/1018 A Review of Multiple Access Technologies SDMA (1/2) In SDMA, users are separated in a spatial way. In SDMA, users are separated in a spatial way. Generally an adaptive array antenna technique is adopted. Generally an adaptive array antenna technique is adopted. One disadvantage is the difficulty of separating two users who are placed near the base station. One disadvantage is the difficulty of separating two users who are placed near the base station.

2005/5/1019 A Review of Multiple Access Technologies SDMA (2/2) Time Frequency Space

2005/5/1020 Outline Introduction Introduction A Review of Multiple Access Technologies A Review of Multiple Access Technologies Key Features of 3G Multiple Access Technologies Key Features of 3G Multiple Access Technologies Multiple Access Technologies For B3G Systems Multiple Access Technologies For B3G Systems Conclusions Conclusions

2005/5/1021 Key Features of 3G Multiple Access Technologies (1/3) International Mobile Telecommunications (IMT-2000) is the “ umbrella specification ” of all 3G systems. International Mobile Telecommunications (IMT-2000) is the “ umbrella specification ” of all 3G systems. –IMT Direct Spread (DS-CDMA, aka UTRA-FDD) –IMT Time Code (TD-CDMA, aka UTRA-TDD) –IMT Multicarrier (MC-CDMA, aka CDMA 2000) –IMT Single Carrier (SC-CDMA, aka UWC-136) –IMT Frequency Time (IMT-FT, aka DECT)

2005/5/1022 Key Features of 3G Multiple Access Technologies IMT-2000 Family

2005/5/1023 Key Features of 3G Multiple Access Technologies (2/3) IMT-2000 has five standard, four of which are based on CDMA. IMT-2000 has five standard, four of which are based on CDMA. –CDMA is a promising access technology for high-data-rate wireless communications. The advantages of CDMA The advantages of CDMA –Tolerance to the effects of channel fading. –Efficient frequency reuse. –Soft handover among cells is achievable.

2005/5/1024 Key Features of 3G Multiple Access Technologies (3/3) Near-far problem Near-far problem –A signal transmitted by a user who is far from the base station can easily be blocked by a signal from a nearby user. –Calls for a power control technique.

2005/5/1025 Key Features of 3G Multiple Access Technologies UMTS Stands for Universal Mobile Telecommunication System. Stands for Universal Mobile Telecommunication System. It ’ s the most important one of the 3G telecommunications systems It ’ s the most important one of the 3G telecommunications systems Two modes of operation in the UMTS terrestrial radio access (UTRA) Two modes of operation in the UMTS terrestrial radio access (UTRA) –Time-division duplex (UTRA-TDD) –Frequency-division duplex (UTRA-FDD)

2005/5/1026 Key Features of 3G Multiple Access Technologies IMT Direct Spread The most important IMT-2000 system. The most important IMT-2000 system. It ’ s being developed by 3GPP consortium It ’ s being developed by 3GPP consortium –UTRA-FDD UTRA-FDD is purely a CDMA-base system, but can be considered a combination of CDMA with FDMA. UTRA-FDD is purely a CDMA-base system, but can be considered a combination of CDMA with FDMA. UTRA-FDD separating frequency spectrum for downlink and uplink. UTRA-FDD separating frequency spectrum for downlink and uplink.

2005/5/1027 Key Features of 3G Multiple Access Technologies IMT Time Code (1/4) It ’ s also being developed by 3GPP consortium It ’ s also being developed by 3GPP consortium –UTRA-TDD Can be considered a combination of CDMA with TDMA. Can be considered a combination of CDMA with TDMA. UTRA-TDD using the same spectrum for both uplink and downlink channels. UTRA-TDD using the same spectrum for both uplink and downlink channels.

2005/5/1028 Key Features of 3G Multiple Access Technologies IMT Time Code (2/4) For both UTRA-TDD and UTRA-FDD For both UTRA-TDD and UTRA-FDD –Each carrier has a bandwidth of 5MHz. –Chip rate is 3.84 Mcps –Each carrier is divided into 10-ms radio frames, and each frame further into 15 time slots.

2005/5/1029 Key Features of 3G Multiple Access Technologies IMT Time Code (3/4)

2005/5/1030 Key Features of 3G Multiple Access Technologies IMT Time Code (4/4) Advantages Advantages –It ’ s possible to flexibly arrange different numbers of time slots on uplink and downlink. –It can change the ratio of uplink and downlink capacity dynamically. –This concept would be necessary for B3G systems where burst data traffic becomes the dominant part. –Appropriate to share power control information.

2005/5/1031 Key Features of 3G Multiple Access Technologies IMT Multicarrier (1/4) The 3GPP2 promotes the CDMA2000 system. The 3GPP2 promotes the CDMA2000 system. In the world or IMT-2000, this proposal is known as IMT-MC. In the world or IMT-2000, this proposal is known as IMT-MC. CDMA2000 is backward compatible with IS-95 systems, which is a standard for 2G system. CDMA2000 is backward compatible with IS-95 systems, which is a standard for 2G system.

2005/5/1032 Key Features of 3G Multiple Access Technologies IMT Multicarrier (2/4) The chip rate in CDMA2000 will be a multiple of Mcps. The chip rate in CDMA2000 will be a multiple of Mcps. –The maximum rate will be 3x ( Mcps) in the first phase. The original goal was to have a system with three narrowband (1.25 MHz) carriers. The original goal was to have a system with three narrowband (1.25 MHz) carriers. –Same bandwidth as an IS-95 carrier

2005/5/1033 Key Features of 3G Multiple Access Technologies IMT Multicarrier (3/4)

2005/5/1034 Key Features of 3G Multiple Access Technologies IMT Multicarrier (4/4) Advantages over DS-CDMA Advantages over DS-CDMA –Suitable for frequency-selective fading channels. –Low interference and less outband radiation. The disadvantages The disadvantages –Require a high linear amplifier that causes inefficient power consumption.

2005/5/1035 Outline Introduction Introduction A Review of Multiple Access Technologies A Review of Multiple Access Technologies Key Features of 3G Multiple Access Technologies Key Features of 3G Multiple Access Technologies Multiple Access Technologies For B3G Systems Multiple Access Technologies For B3G Systems Conclusions Conclusions

2005/5/1036 Multiple Access Technologies For B3G Systems Main feature required in B3G systems Main feature required in B3G systems –High-data-rate transmission. (10 Mbps or more) It is difficult to introduce an actual compensation method for the fading effect of every user and every subchannel. It is difficult to introduce an actual compensation method for the fading effect of every user and every subchannel. The current CDMA schemes unfortunately do not satisfy the requirement of B3G. The current CDMA schemes unfortunately do not satisfy the requirement of B3G.

2005/5/1037 Multiple Access Technologies for B3G systems Advanced MA Schemes (1/3) Multicarrier DS-CDMA (MC/DS-CDMA) Multicarrier DS-CDMA (MC/DS-CDMA) –Combination of MC-CDMA and DS-CDMA –Can achieve very-high-data-rate transmission with the advantages of both schemes. –Requires an amplifier with high linearity, which results in power inefficiency. (similar to MC-CDMA)

2005/5/1038 Multiple Access Technologies for B3G systems Advanced MA Schemes (2/3) TDD-CDMA TDD-CDMA –A modified version of TD-CDMA. –Better frequency efficiency than UTRA-FDD. –Can easily achieve asymmetric transmissions. –Will become a major MA scheme for B3G system.

2005/5/1039 Multiple Access Technologies for B3G systems Advanced MA Schemes (3/3) Orthogonal frequency-division MA (OFDMA) Orthogonal frequency-division MA (OFDMA) –Has attracted much attention in the IEEE standard. –The concept is essentially the same as FDMA, but it has some advantages. –Transmission with different rates among users is available according to each user ’ s requirement.

2005/5/1040 Outline Introduction Introduction A Review of Multiple Access Technologies A Review of Multiple Access Technologies Key Features of 3G Multiple Access Technologies Key Features of 3G Multiple Access Technologies Multiple Access Technologies For B3G Systems Multiple Access Technologies For B3G Systems Conclusions Conclusions

2005/5/1041 Conclusions The technologies for MA schemes that have been adopted in 3G systems are examined. The technologies for MA schemes that have been adopted in 3G systems are examined. None of the existing MA techniques would be able to satisfy the transmission criteria in B3G system. None of the existing MA techniques would be able to satisfy the transmission criteria in B3G system.

2005/5/1042 Conclusions Next-generation networks will be developed through good management and a combination of the advanced MA technologies, rather than the development of new schemes. Next-generation networks will be developed through good management and a combination of the advanced MA technologies, rather than the development of new schemes.

2005/5/1043 References A. Jamalipour, T. Wada, and T. Yamazato, "A Tutorial on Multiple Access Technologies for Beyond 3G Mobile Networks," IEEE Communications Magazine, vol. 43, no. 2, Feb. 2005, pp A. Jamalipour, T. Wada, and T. Yamazato, "A Tutorial on Multiple Access Technologies for Beyond 3G Mobile Networks," IEEE Communications Magazine, vol. 43, no. 2, Feb. 2005, pp Juha Korhonen, Introduction to 3G Mobile Communications 2nd ed., Artech House, Juha Korhonen, Introduction to 3G Mobile Communications 2nd ed., Artech House, 2003.

2005/5/1044 B3G MA schemes L.-L. Yang and L. Hanzo, “ Multicarrier DS-CDMA: A Multiple Access Scheme for Ubiquitous Broadband Wireless Communications, ” IEEE Communications Magazine, vol. 41, no. 10, Oct. 2003, pp L.-L. Yang and L. Hanzo, “ Multicarrier DS-CDMA: A Multiple Access Scheme for Ubiquitous Broadband Wireless Communications, ” IEEE Communications Magazine, vol. 41, no. 10, Oct. 2003, pp R. Esmailzadeh and M. Nakagawa, “ TDD-CDMA for the 4th Generation of Wireless Communications, ” IEEE Communications Magazine, vol. 41, no. 8, Aug. 2003, pp R. Esmailzadeh and M. Nakagawa, “ TDD-CDMA for the 4th Generation of Wireless Communications, ” IEEE Communications Magazine, vol. 41, no. 8, Aug. 2003, pp P. Xia, S. Zhou, and G. B. Giannakis, “ Bandwidth- and power-Efficient Multicarrier Multiple Access, ” IEEE Trans. Commun., vol. 51, no.11, Nov. 2003, pp P. Xia, S. Zhou, and G. B. Giannakis, “ Bandwidth- and power-Efficient Multicarrier Multiple Access, ” IEEE Trans. Commun., vol. 51, no.11, Nov. 2003, pp