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Understanding LTE Evolution: From Basic Concepts to Advanced Techniques

Explore the history, basic concepts, and protocol of 3GPP LTE, comparing LTE and LTE-Advanced. Learn about OFDMA, SC-FDMA, multipath effects, frequency fading, multi-antenna techniques, frame structure, and more. Discover the key features of LTE Release 8 and the evolution of LTE-Advanced with advanced transmission and reception techniques, multi-antenna advancements, and larger bandwidth support.

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Understanding LTE Evolution: From Basic Concepts to Advanced Techniques

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  1. 3GPP Long Term Evolution (LTE)

  2. Outline • History of 3GPP LTE • Basic Concepts of LTE • Introduction of LTE Protocol • Comparison of LTE and LTE-Advanced • Conclusion

  3. What is LTE ? • In Nov. 2004, 3GPP began a project to define the long-term evolution (LTE) of Universal Mobile Telecommunications System (UMTS) cellular technology • Higher performance • Backwards compatible • Wide application

  4. Evolution of Radio Access Technologies • LTE (3.9G) : 3GPP release 8~9 • LTE-Advanced :3GPP release 10+ 802.16m 802.16d/e

  5. LTE Basic Concepts • LTE employs OrthogonalFrequency Division Multiple Access (OFDMA) for downlink data transmission and Single Carrier FDMA (SC-FDMA) for uplink transmission

  6. Multipath-Induced Time Delays Result in Inter-Symbol Interference (ISI) βS(t-m) S(t) y(t) : output signal S(t) : input signal S(t-m) : delayed m time input signal n(t) : noise y(t)

  7. Equalizers in Receiver • Against Frequency Selective Fading • Channel transform function Hc(f) • Equalizers transfer function, Heq(f) (Receiver)

  8. Frequency Selective Fading • Coherence bandwidth of the channel is smaller than the bandwidth of the signal Frequency Correlation > 0.9 Bc = 1 / 50α α is r.m.s. delay spread It may be useless even in increasing transmission power

  9. Cyclic Prefixes against multipath

  10. FDM vs. OFDM

  11. LTE-Downlink (OFDM) • Improved spectral efficiency • Reduce ISI effect by cyclic prefix • Against frequency selective fading

  12. LTE Uplink (SC-FDMA) • SC-FDMA is a new single carrier multiple access technique which has similar structure and same performance to OFDMA • A salient advantage of SC-FDMA over OFDM is low to Peak to Average Power Ratio (PAPR) : • Increasing battery life

  13. Multi-antenna techniques

  14. Generic Frame Structure • Allocation of physical resource blocks (PRBs) is handled by a scheduling function at the 3GPP base station (eNodeB) Frame 0 and frame 5 (always downlink)

  15. Resource block • One frame is 10ms  10 subframes  20 slots • One subframe is 1ms  2 slots • One slot is 0.5ms  N resource blocks[ 6 < N < 110] • One resource block is 0.5ms and contains 12 subcarriers from each OFDM symbol

  16. LTE spectrum (bandwidth and duplex) flexibility

  17. LTE Release 8 Key Features (1/2) • High spectral efficiency • OFDM in Downlink • Single‐Carrier FDMA in Uplink • Very low latency • Short setup time & Short transfer delay • Short hand over latency and interruption time • Support of variable bandwidth • 1.4, 3, 5, 10, 15 and 20 MHz • Compatibility and interworking with earlier 3GPP Releases • FDD and TDD within a single radio access  technology • Efficient Multicast/Broadcast

  18. Evolution of LTE-Advanced • Asymmetric transmission bandwidth • Layered OFDMA • Advanced Multi-cell Transmission/Reception Techniques • Enhanced Multi-antenna Transmission Techniques • Support of Larger Bandwidth in LTE-Advanced

  19. Asymmetric transmission bandwidth • Symmetric transmission • voice transmission : UE to UE • Asymmetric transmission • streaming video : the server to the UE (the downlink)

  20. Layered OFDMA • The bandwidth of basic frequency block is, 15–20 MHz • Layered OFDMA radio access scheme in LTE-A will have layered transmission bandwidth, support of layered environments and control signal formats

  21. Advanced Multi-cell Transmission/Reception Techniques • In LTE-A, the advanced multi-cell transmission/reception processes helps in increasing frequency efficiency and cell edge user throughput • Estimation unit • Calculation unit • Determination unit • Feedback unit

  22. Enhanced Multi-antenna Transmission Techniques • In LTE-A, the MIMO scheme has to be further improved in the area of spectrum efficiency, average cell through put and cell edge performances • In LTE-A the antenna configurations of 8x8 in DL and 4x4 in UL are planned

  23. Enhanced Techniques to Extend Coverage Area • Remote Radio Requirements (RREs) using optical fiber should be used in LTE-A as effective technique to extend cell coverage

  24. Support of Larger Bandwidth in LTE-Advanced • Peak data rates up to 1Gbps are expected from bandwidths of 100MHz. OFDM adds additional sub-carrier to increase bandwidth

  25. LTE vs. LTE-Advanced

  26. Conclusion • LTE-A helps in integrating the existing networks, new networks, services and terminals to suit the escalating user demands • LTE-Advanced will be standardized in the 3GPP specification Release 10 (LTE-A) and will be designed to meet the 4G requirements as defined by ITU

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