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LTE ( Long Term Evolution)

LTE ( Long Term Evolution). 國立屏東科技大學 資訊管理系. 教材編撰：童曉儒 教授 林美賢. 章節要點 (Chapter keys). Motivation for LTE 3GPP Technology Evolution Why LTE? GSM, GPRS, UMTS LTE Architecture Evolved NodeB ( eNodeB ) MAC protocol eNB Scheduler Multiple Access Frequency Bands MBMS HeNB. MAC protocol.

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LTE ( Long Term Evolution)

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  1. LTE(Long Term Evolution) • 國立屏東科技大學 資訊管理系 • 教材編撰：童曉儒 教授 • 林美賢

  2. 章節要點 (Chapter keys) Motivation for LTE 3GPP Technology Evolution Why LTE? GSM, GPRS, UMTS LTE Architecture Evolved NodeB (eNodeB) MAC protocol eNB Scheduler Multiple Access Frequency Bands MBMS HeNB

  3. MAC protocol 12 10 11 7 5 3 2 4 8 9 6 1 eNB Scheduler Motivation for LTE 章節目錄 (Chapter layouts) 3GPP Technology Evolution Why LTE? GSM, GPRS, UMTS LTE Architecture Evolved NodeB (eNodeB) Multiple Access Frequency Bands MBMS HeNB

  4. Motivation for LTE • LTE: 3GPP Release 8, frozen in December 200. • The motivation: • Need to ensure the continuity of competitiveness of the 3G system for the future • User demand for higher data rates and quality of service • Packet Switch optimised system • Continued demand for cost reduction (CAPEX and OPEX) • Low complexity • Avoid unnecessary fragmentation of technologies for paired and unpaired band operation

  5. 3GPP Technology Evolution

  6. Why LTE? • LTE (Long Term Evolution) or the E-UTRAN (Evolved Universal Terrestrial Access Network), introduced in 3GPP R8, is the access part of the Evolved Packet System (EPS). • The main requirements: • high spectral efficiency, • high peak data rates, • short round trip time • flexibility in frequency and bandwidth • All IP network.

  7. 3GPP Network Solutions from GSM to LTE

  8. GSM, GPRS, UMTS • GSM:circuit switchedconnection with very low data rates. • GPRS: an IP based packet switched network with the evolution of GSM using TDMA (Time Division Multiple Access). • UMTS (Universal Mobile Terrestrial System): • WCDMA (Wideband Code Division Multiple Access) • circuit switched connection for real time services • packet switched connection for datacom services • IP address is allocated to the UE when a datacom service is established and released when the service is released. • Incoming datacom services are therefore still relying upon the circuit switched core for paging.

  9. LTE Architecture • Purely IP based. Both real time services and datacom services will be carried by the IP protocol. • The IP address is allocated when the mobile is switched on and released when switched off. • Access solution: • OFDMA (Orthogonal Frequency Division Multiple Access) • higher order modulation (up to 64QAM), • large bandwidths (up to 20 MHz) • spatial multiplexing in the downlink (up to 4x4 • 75 Mbps in the uplink, and 300 Mbps in the downlink. 

  10. Evolved NodeB (eNodeB) The LTE access network: a network of base stations, evolved NodeB (eNB). No centralized intelligent controller eNBs are normally inter-connected via the X2-interface and towards the core network by the S1-interface. Speed up the connection set-up. Reduce the time required for a handover.

  11. MAC protocol The scheduler is a key component for the achievement of a fast adjusted and efficiently utilized radio resource. LTE: a distributed scheduling, decided by UE eNB leading to fast communication. UMTS: a centralized scheduling, decided by controller and NB The Transmission Time Interval (TTI) is set to only 1 ms.

  12. eNB Scheduler • During each TTI, UEs report their perceived radio quality to eNB. • eNB decides Modulation and Coding scheme. • Prioritize the QoS service requirements amongst the UEs. • delay sensitive real-time services • datacom services • eNB informs the UEs of allocated radio resources both on the downlink and on the uplink. • User data will be carried in a Transport Block (TB).

  13. Multiple Access Multicarrier approach for was chosen by 3GPP. For the downlink, OFDMA (Orthogonal Frequency Division Multiple Access) was selected. For the uplink, SC-FDMA (Single Carrier - Frequency Division Multiple Access) also known as DFT (Discrete Fourier Transform) spread OFDMA.

  14. Frequency Bands • E-UTRA operating bands: 700 MHz up to 2.7GHz. • The available bandwidths are also flexible starting with 1.4 MHz up to 20 MHz. • Support both the time division duplex (TDD) and frequency division duplex (FDD). • In R8 there are 15 bands specified for FDD and eight bands for TTD. • In R9 four bands were added for FDD. • In R9, Multimedia Broadcast Multicast Service (MBMS), and Home eNB (HeNB) are added.

  15. MBMS Broadcast information to all users, for example advertisement. Multicast to a closed group subscribing to a specific service, e.g. streaming TV.

  16. HeNB HeNB is low power eNB that will be used in small cells – femto cells. Provide coverage indoors, in homes or offices. owned by the customer, deployed without any network planning and connected to the operators EPC (Evolved Packet Core).

  17. Reference http://www.3gpp.org/technologies/keywords-acronyms/98-lte

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