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A Tutorial on Multiple Access Technologies for Beyond 3G Mobile Networks

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. Outline. Introduction A Review of Multiple Access Technologies Key Features of 3G Multiple Access Technologies

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A Tutorial on Multiple Access Technologies for Beyond 3G Mobile Networks

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  1. 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

  2. Outline • Introduction • A Review of Multiple Access Technologies • Key Features of 3G Multiple Access Technologies • Multiple Access Technologies For B3G Systems • Conclusions

  3. Introduction (1/3) • 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.

  4. Introduction (2/3) • 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.

  5. Introduction (3/3) • 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.

  6. Outline • Introduction • A Review of Multiple Access Technologies • Key Features of 3G Multiple Access Technologies • Multiple Access Technologies For B3G Systems • Conclusions

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

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

  9. A Review of Multiple Access TechnologiesFDMA (1/2) • 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. • Multiple users using separate frequency channels could access the same system.

  10. A Review of Multiple Access TechnologiesFDMA (2/2)

  11. A Review of Multiple Access TechnologiesTDMA (1/3) • Dividing the time axis into portions or time slots, each assigned to a single user to transmit data information. • 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.

  12. A Review of Multiple Access TechnologiesTDMA (2/3)

  13. A Review of Multiple Access TechnologiesTDMA (3/3) • 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. • Hybrid FDMA/TDMA system

  14. A Review of Multiple Access TechnologiesHybrid FDMA/TDMA

  15. A Review of Multiple Access TechnologiesCDMA (1/3) • 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.

  16. A Review of Multiple Access TechnologiesCDMA (2/3) • 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)

  17. A Review of Multiple Access TechnologiesCDMA (3/3)

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

  19. A Review of Multiple Access TechnologiesSDMA (2/2) Space Time Frequency

  20. Outline • Introduction • A Review of Multiple Access Technologies • Key Features of 3G Multiple Access Technologies • Multiple Access Technologies For B3G Systems • Conclusions

  21. Key Features of 3G Multiple Access Technologies (1/3) • International Mobile Telecommunications-2000 (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)

  22. Key Features of 3G Multiple Access TechnologiesIMT-2000 Family

  23. Key Features of 3G Multiple Access Technologies (2/3) • 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 • Tolerance to the effects of channel fading. • Efficient frequency reuse. • Soft handover among cells is achievable.

  24. Key Features of 3G Multiple Access Technologies (3/3) • 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.

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

  26. Key Features of 3G Multiple Access TechnologiesIMT Direct Spread • The most important IMT-2000 system. • 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 separating frequency spectrum for downlink and uplink.

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

  28. Key Features of 3G Multiple Access TechnologiesIMT Time Code (2/4) • 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.

  29. Key Features of 3G Multiple Access TechnologiesIMT Time Code (3/4)

  30. Key Features of 3G Multiple Access TechnologiesIMT Time Code (4/4) • 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.

  31. Key Features of 3G Multiple Access TechnologiesIMT Multicarrier (1/4) • The 3GPP2 promotes the CDMA2000 system. • 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.

  32. Key Features of 3G Multiple Access TechnologiesIMT Multicarrier (2/4) • The chip rate in CDMA2000 will be a multiple of 1.2288 Mcps. • The maximum rate will be 3x (3.6864 Mcps) in the first phase. • The original goal was to have a system with three narrowband (1.25 MHz) carriers. • Same bandwidth as an IS-95 carrier

  33. Key Features of 3G Multiple Access TechnologiesIMT Multicarrier (3/4)

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

  35. Outline • Introduction • A Review of Multiple Access Technologies • Key Features of 3G Multiple Access Technologies • Multiple Access Technologies For B3G Systems • Conclusions

  36. Multiple Access Technologies For 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. • The current CDMA schemes unfortunately do not satisfy the requirement of B3G.

  37. Multiple Access Technologies for B3G systemsAdvanced MA Schemes (1/3) • 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)

  38. Multiple Access Technologies for B3G systemsAdvanced MA Schemes (2/3) • 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.

  39. Multiple Access Technologies for B3G systemsAdvanced MA Schemes (3/3) • Orthogonal frequency-division MA (OFDMA) • Has attracted much attention in the IEEE 802.16 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.

  40. Outline • Introduction • A Review of Multiple Access Technologies • Key Features of 3G Multiple Access Technologies • Multiple Access Technologies For B3G Systems • Conclusions

  41. Conclusions • 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.

  42. 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.

  43. 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. 110-117. • Juha Korhonen, Introduction to 3G Mobile Communications 2nd ed., Artech House, 2003.

  44. 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. 116-124. • R. Esmailzadeh and M. Nakagawa, “TDD-CDMA for the 4th Generation of Wireless Communications,”IEEE Communications Magazine, vol. 41, no. 8, Aug. 2003, pp. 8-15. • 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. 1828-37.

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