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LTE-Overview
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Copyright © 2011, [email protected]
2
Outline
• Overview• Network architecture• Protocol stack• Resource element• Frame structure
– TDD frame configuration– TDD special subframe
• MIMO• Random access procedure
Copyright © 2011, [email protected]
3
LTE Overview
• LTE – Long Term Evolution: The 4th generation telecommunication standards.– Evolved from the 3GPP system.(R8)– RAN: LTE– Core: SAE(System Architecture Evolution)
• Characteristics:– Packet switching– All – IP network– Higher data rate– OFDMA based– MIMO supported
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Resource element
• The basic unit when allocating carrier resource.
• Resource Element(RE):– One subcarrier by one
symbol
• Resource Block(RB):– 12 subcarriers by 7
symbol
• Resource Element Group(REG):– For control plane– One REG has 4 or 6
REs.
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LTE Frame Structure
• One radio frame has 10 ms:– 10 subframes, each
of 1 ms.
• Duplexing:– FDD– TDD
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LTE TDD Frame
• UL-DL configuration:– LTE TDD can have 7
UL-DL subframe configurations.
• Special Subframe:– Provide a gap to allow
switching from DL to UL a transition subframe.
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MIMO
• Multiple-Input Multiple-Output: – multiple antennas at
both the transmitter and receiver to improve communication performance.
• Better throughput• Longer transmission
distance
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MIMO modes
• Downlink Transmission Mode:– Release 8 have defined 7 transmission modes.
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Random Access Procedure
• Random access purpose: Set up the RRC (Radio Resource Control) connection when:– Idle state or initial power on– Handover– Synchronization– Reset RRC
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References
• TDD LTE Air Interfaces v.1• TS 33.401 3GPP System Architecture Evolution (SAE):
Security architecture • TS 36.213 Evolved Universal Terrestrial Radio Access
(E-UTRA); Physical layer procedures • TS 36.321 Evolved Universal Terrestrial Radio Access
(E-UTRA); Medium Access Control (MAC) protocol specification
