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3 gpp lte-mac

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Md Sharique Iqbal
Md Sharique Iqbal

This document discusses the Medium Access Control (MAC) layer in 3GPP Long Term Evolution (LTE) cellular networks. It covers topics such as LTE channel architecture with physical, transport, and logical channels; functions of the MAC layer including mapping channels, error correction, priority handling, and logical channel prioritization; MAC sublayer organization in the downlink and uplink; and downlink and uplink channel types including their purposes and characteristics. The document is intended to provide an overview of the MAC layer and channel structure in LTE networks.

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EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems 3GPP LTE Channels and MAC Layer © 2009 EventHelix.com Inc. All Rights Reserved.
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE MAC Layer Functions Mapping between Transparent and Logical Channels Error Correction Through Hybrid ARQ Priority Handling with Dynamic Scheduling Logical Channel Prioritization MAC © 2009 EventHelix.com Inc. 2
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems MAC in the LTE Protocol Stack © 2009 EventHelix.com Inc. 3 MME NAS eNodeB RRC PDCP RLC MAC PHY UE NAS RRC PDCP RLC MAC PHY
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Channel Architecture PHY Physical Channels MAC Transport Channels RLC Logical Channels 1. RLC layer passes data to the MAC layer as logical channels. 2. The MAC layer formats and sends the logical channel data as transport channel. 3. The physical layer encodes the transport channel data to physical channels. © 2009 EventHelix.com Inc. 4
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems Downlink PDCP, RLC and MAC Sublayer Organization Segm. ARQ etc Multiplexing UE1 Segm. ARQ etc ... HARQ Multiplexing UEn HARQ BCCH PCCH Scheduling / Priority Handling Logical Channels Transport Channels MAC RLC Segm. ARQ etc Segm. ARQ etc PDCP ROHC ROHC ROHC ROHC Radio Bearers Security Security Security Security ... CCCH © 2009 EventHelix.com Inc. 5
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems Uplink PDCP, RLC and MAC Sublayer Organization Multiplexing ... HARQ Scheduling / Priority Handling Transport Channels MAC RLC PDCP Segm. ARQ etc Segm. ARQ etc Logical Channels ROHC ROHC Radio Bearers Security Security CCCH © 2009 EventHelix.com Inc. 6
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Channels BCCHPCCH CCCH DCCH DTCH MCCH MTCH BCHPCH DL-SCH MCH Downlink Logical channels Downlink Transport channels Downlink Physical channelsPBCH PDSCH PMCH PDCCH PHICH © 2009 EventHelix.com Inc. 7
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Logical Channels 1 • A downlink channel that transfers paging information and system information change notifications. • This channel is used for paging when the network does not know the location cell of the UE. Paging Control Channel (PCCH) • A downlink channel for broadcasting system control information. Broadcast Control Channel (BCCH) • Channel for transmitting control information between UEs and network. • This channel is used for UEs having no RRC connection with the network. Common Control Channel (CCCH) © 2009 EventHelix.com Inc. 8
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Logical Channels 2 • A point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. • Used by UEs having an RRC connection. Dedicated Control Channel (DCCH) • A point-to-point channel, dedicated to one UE, for the transfer of user information. • A DTCH can exist in both uplink and downlink. Dedicated Traffic Channel (DTCH) • A point-to-multipoint downlink channel used for transmitting MBMS control information from the network to the UE, for one or several MTCHs. • This channel is only used by UEs that receive MBMS. Multicast Control Channel (MCCH) • A point-to-multipoint downlink channel for transmitting traffic data from the network to the UE. • This channel is only used by UEs that receive MBMS. Multicast Traffic Channel (MTCH) © 2009 EventHelix.com Inc. 9
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Transport Channels 1 • Supports UE discontinuous reception (DRX) to enable UE power saving • Broadcasts in the entire coverage area of the cell; • Mapped to physical resources which can be used dynamically also for traffic/other control channels. Paging Channel (PCH) • Fixed, pre-defined transport format • Broadcast in the entire coverage area of the cell Broadcast Channel (BCH) • Broadcasts in the entire coverage area of the cell; • Supports MBSFN combining of MBMS transmission on multiple cells; • Supports semi-static resource allocation e.g. with a time frame of a long cyclic prefix. Multicast Channel (MCH) © 2009 EventHelix.com Inc. 10
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Transport Channels 2 • Supports Hybrid ARQ • Supports dynamic link adaptation by varying the modulation, coding and transmit power • Optionally supports broadcast in the entire cell; • Optionally supports beam forming • Supports both dynamic and semi-static resource allocation • Supports UE discontinuous reception (DRX) to enable UE power saving • Supports MBMS transmission Downlink Shared Channel (DL-SCH) © 2009 EventHelix.com Inc. 11
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Physical Channels 1 • Carries the DL-SCH and PCH • QPSK, 16-QAM, and 64-QAM Modulation Physical Downlink Shared Channel (PDSCH) • Informs the UE about the resource allocation of PCH and DL-SCH, and Hybrid ARQ information related to DL-SCH • Carries the uplink scheduling grant • QPSK Modulation Physical Downlink Control Channel (PDCCH) • Carries Hybrid ARQ ACK/NAKs in response to uplink transmissions. • QPSK Modulation Physical Hybrid ARQ Indicator Channel (PHICH) © 2009 EventHelix.com Inc. 12
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Physical Channels 2 •The coded BCH transport block is mapped to four sub-frames within a 40 ms interval. 40 ms timing is blindly detected, i.e. there is no explicit signalling indicating 40 ms timing •Each sub-frame is assumed to be self-decodable, i.e. the BCH can be decoded from a single reception, assuming sufficiently good channel conditions. •QPSK Modulation Physical Broadcast Channel (PBCH) •Carries the MCH •QPSK, 16-QAM, and 64-QAM Modulation Physical Multicast Channel (PMCH) © 2009 EventHelix.com Inc. 13
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Uplink Channels CCCH DCCH DTCH UL-SCHRACH Uplink Logical channels Uplink Transport channels Uplink Physical channels PRACH PUSCH PUCCH © 2009 EventHelix.com Inc. 14
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Uplink Logical Channels • Channel for transmitting control information between UEs and network. • This channel is used for UEs having no RRC connection with the network. Common Control Channel (CCCH) • A point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. • Used by UEs having an RRC connection. Dedicated Control Channel (DCCH) • A point-to-point channel, dedicated to one UE, for the transfer of user information. • A DTCH can exist in both uplink and downlink. Dedicated Traffic Channel (DTCH) © 2009 EventHelix.com Inc. 15
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Uplink Transport Channels • Channel carries minimal information • Transmissions on the channel may be lost due to collisions Random Access Channel (RACH) • Optional support for beam forming • Supports dynamic link adaptation by varying the transmit power and potentially modulation and coding • Supports Hybrid ARQ • Supports dynamic and semi-static resource allocation Uplink Shared Channel (UL-SCH) © 2009 EventHelix.com Inc. 16
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Uplink Physical Channels • Carries the random access preamble • The random access preambles are generated from Zadoff-Chu sequences with zero correlation zone, generated from one or several root Zadoff-Chu sequences. Physical Radio Access Channel (PRACH) • Carries the UL-SCH • QPSK, 16-QAM, and 64-QAM Modulation Physical Uplink Shared Channel (PUSCH) • Carries Hybrid ARQ ACK/NAKs in response to downlink transmission • Carries Scheduling Request (SR) • Carries CQI reports • BPSK and QPSK Modulation Packet Uplink Control Channel (PUCCH) © 2009 EventHelix.com Inc. 17
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems RNTI Mapping • When MAC uses the PDCCH to indicate radio resource allocation, the RNTI that is mapped on the PDCCH depends on the logical channel type: DTCCH and DTCH C-RNTI Temporary C-RNTI Semi Persistent C-RNTI PCCH P-RNTI RA Resp. on DL-SCH RA-RNTI CCCH Temporary C-RNTI BCCH SI-RNTI © 2009 EventHelix.com Inc. 18
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems Random Access Procedure Contention Resolution Uplink control message is transmitted on the granted uplink resource and the contention resolution timer is started The contention resolution timer is stopped when the lower layers indicate that the message has been acknowledged Random Access Response Reception on PDCCH Match the preamble to receive the response Apply the timing advance in the message Process uplink resource grant Random Access Preamble Transmission Set Preamble Target Power Ask Physical Layer to Transmit Preamble Random Access Resource Selection Select Random Access Preamble Determine the next available PRACH Sub-frame © 2009 EventHelix.com Inc. 19
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems DL-SCH Data Transfer Data Delivery and Acknowledgement If data in the Soft buffer is successfully decoded and no error is detected, send positive acknowledgement If data decoding in the Soft buffer results in an error, a negative acknowledgement is sent. Hybrid ARQ Operation If received NDI != previous NDI or first transmission: Soft buffer contents are replaced with new data If received NDI == previous NDI: Soft buffer data is chase combined with the new data Downlink Assignment Received on PDCCH Message indicates if there is transmission on the DL- SCH for the UE. New Data Indicator (NDI) is updated © 2009 EventHelix.com Inc. 20
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems UL-SCH Data Transfer UE transmits the uplink data on the assigned resources. Hybrid ARQ is used. Uplink Grant assigns uplink resources for transmission Power Headroom Report (PHR) communicates the additional return power available at the UE. Buffer Status Report (BSR) is sent to report pending data in uplink buffers. Scheduling Request (SR) is sent to initiate uplink data transfer. © 2009 EventHelix.com Inc. 21
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems Explore More Specification Title 3GPP TS 36.300 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 3GPP TS 36.321 Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocol specification 3GPP TS 36.211 Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation © 2009 EventHelix.com Inc. 22
EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems Thank You Links Description EventStudio System Designer 4.0 Sequence diagram based systems engineering tool. VisualEther Protocol Analyzer 1.0 Wireshark based visual protocol analysis and system design reverse engineering tool. Telecom Call Flows GSM, SIP, H.323, ISUP, LTE and IMS call flows. TCP/IP Sequence Diagrams TCP/IP explained with sequence diagrams. Real-time and Embedded System Articles Real-time and embedded systems, call flows and object oriented design articles. © 2009 EventHelix.com Inc. 23 Thank you for visiting EventHelix.com. The following links provide more information about telecom design tools and techniques:

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3 gpp lte-mac

  • 1. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems 3GPP LTE Channels and MAC Layer © 2009 EventHelix.com Inc. All Rights Reserved.
  • 2. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE MAC Layer Functions Mapping between Transparent and Logical Channels Error Correction Through Hybrid ARQ Priority Handling with Dynamic Scheduling Logical Channel Prioritization MAC © 2009 EventHelix.com Inc. 2
  • 3. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems MAC in the LTE Protocol Stack © 2009 EventHelix.com Inc. 3 MME NAS eNodeB RRC PDCP RLC MAC PHY UE NAS RRC PDCP RLC MAC PHY
  • 4. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Channel Architecture PHY Physical Channels MAC Transport Channels RLC Logical Channels 1. RLC layer passes data to the MAC layer as logical channels. 2. The MAC layer formats and sends the logical channel data as transport channel. 3. The physical layer encodes the transport channel data to physical channels. © 2009 EventHelix.com Inc. 4
  • 5. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems Downlink PDCP, RLC and MAC Sublayer Organization Segm. ARQ etc Multiplexing UE1 Segm. ARQ etc ... HARQ Multiplexing UEn HARQ BCCH PCCH Scheduling / Priority Handling Logical Channels Transport Channels MAC RLC Segm. ARQ etc Segm. ARQ etc PDCP ROHC ROHC ROHC ROHC Radio Bearers Security Security Security Security ... CCCH © 2009 EventHelix.com Inc. 5
  • 6. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems Uplink PDCP, RLC and MAC Sublayer Organization Multiplexing ... HARQ Scheduling / Priority Handling Transport Channels MAC RLC PDCP Segm. ARQ etc Segm. ARQ etc Logical Channels ROHC ROHC Radio Bearers Security Security CCCH © 2009 EventHelix.com Inc. 6
  • 7. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Channels BCCHPCCH CCCH DCCH DTCH MCCH MTCH BCHPCH DL-SCH MCH Downlink Logical channels Downlink Transport channels Downlink Physical channelsPBCH PDSCH PMCH PDCCH PHICH © 2009 EventHelix.com Inc. 7
  • 8. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Logical Channels 1 • A downlink channel that transfers paging information and system information change notifications. • This channel is used for paging when the network does not know the location cell of the UE. Paging Control Channel (PCCH) • A downlink channel for broadcasting system control information. Broadcast Control Channel (BCCH) • Channel for transmitting control information between UEs and network. • This channel is used for UEs having no RRC connection with the network. Common Control Channel (CCCH) © 2009 EventHelix.com Inc. 8
  • 9. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Logical Channels 2 • A point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. • Used by UEs having an RRC connection. Dedicated Control Channel (DCCH) • A point-to-point channel, dedicated to one UE, for the transfer of user information. • A DTCH can exist in both uplink and downlink. Dedicated Traffic Channel (DTCH) • A point-to-multipoint downlink channel used for transmitting MBMS control information from the network to the UE, for one or several MTCHs. • This channel is only used by UEs that receive MBMS. Multicast Control Channel (MCCH) • A point-to-multipoint downlink channel for transmitting traffic data from the network to the UE. • This channel is only used by UEs that receive MBMS. Multicast Traffic Channel (MTCH) © 2009 EventHelix.com Inc. 9
  • 10. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Transport Channels 1 • Supports UE discontinuous reception (DRX) to enable UE power saving • Broadcasts in the entire coverage area of the cell; • Mapped to physical resources which can be used dynamically also for traffic/other control channels. Paging Channel (PCH) • Fixed, pre-defined transport format • Broadcast in the entire coverage area of the cell Broadcast Channel (BCH) • Broadcasts in the entire coverage area of the cell; • Supports MBSFN combining of MBMS transmission on multiple cells; • Supports semi-static resource allocation e.g. with a time frame of a long cyclic prefix. Multicast Channel (MCH) © 2009 EventHelix.com Inc. 10
  • 11. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Transport Channels 2 • Supports Hybrid ARQ • Supports dynamic link adaptation by varying the modulation, coding and transmit power • Optionally supports broadcast in the entire cell; • Optionally supports beam forming • Supports both dynamic and semi-static resource allocation • Supports UE discontinuous reception (DRX) to enable UE power saving • Supports MBMS transmission Downlink Shared Channel (DL-SCH) © 2009 EventHelix.com Inc. 11
  • 12. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Physical Channels 1 • Carries the DL-SCH and PCH • QPSK, 16-QAM, and 64-QAM Modulation Physical Downlink Shared Channel (PDSCH) • Informs the UE about the resource allocation of PCH and DL-SCH, and Hybrid ARQ information related to DL-SCH • Carries the uplink scheduling grant • QPSK Modulation Physical Downlink Control Channel (PDCCH) • Carries Hybrid ARQ ACK/NAKs in response to uplink transmissions. • QPSK Modulation Physical Hybrid ARQ Indicator Channel (PHICH) © 2009 EventHelix.com Inc. 12
  • 13. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Downlink Physical Channels 2 •The coded BCH transport block is mapped to four sub-frames within a 40 ms interval. 40 ms timing is blindly detected, i.e. there is no explicit signalling indicating 40 ms timing •Each sub-frame is assumed to be self-decodable, i.e. the BCH can be decoded from a single reception, assuming sufficiently good channel conditions. •QPSK Modulation Physical Broadcast Channel (PBCH) •Carries the MCH •QPSK, 16-QAM, and 64-QAM Modulation Physical Multicast Channel (PMCH) © 2009 EventHelix.com Inc. 13
  • 14. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Uplink Channels CCCH DCCH DTCH UL-SCHRACH Uplink Logical channels Uplink Transport channels Uplink Physical channels PRACH PUSCH PUCCH © 2009 EventHelix.com Inc. 14
  • 15. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Uplink Logical Channels • Channel for transmitting control information between UEs and network. • This channel is used for UEs having no RRC connection with the network. Common Control Channel (CCCH) • A point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. • Used by UEs having an RRC connection. Dedicated Control Channel (DCCH) • A point-to-point channel, dedicated to one UE, for the transfer of user information. • A DTCH can exist in both uplink and downlink. Dedicated Traffic Channel (DTCH) © 2009 EventHelix.com Inc. 15
  • 16. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Uplink Transport Channels • Channel carries minimal information • Transmissions on the channel may be lost due to collisions Random Access Channel (RACH) • Optional support for beam forming • Supports dynamic link adaptation by varying the transmit power and potentially modulation and coding • Supports Hybrid ARQ • Supports dynamic and semi-static resource allocation Uplink Shared Channel (UL-SCH) © 2009 EventHelix.com Inc. 16
  • 17. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems LTE Uplink Physical Channels • Carries the random access preamble • The random access preambles are generated from Zadoff-Chu sequences with zero correlation zone, generated from one or several root Zadoff-Chu sequences. Physical Radio Access Channel (PRACH) • Carries the UL-SCH • QPSK, 16-QAM, and 64-QAM Modulation Physical Uplink Shared Channel (PUSCH) • Carries Hybrid ARQ ACK/NAKs in response to downlink transmission • Carries Scheduling Request (SR) • Carries CQI reports • BPSK and QPSK Modulation Packet Uplink Control Channel (PUCCH) © 2009 EventHelix.com Inc. 17
  • 18. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems RNTI Mapping • When MAC uses the PDCCH to indicate radio resource allocation, the RNTI that is mapped on the PDCCH depends on the logical channel type: DTCCH and DTCH C-RNTI Temporary C-RNTI Semi Persistent C-RNTI PCCH P-RNTI RA Resp. on DL-SCH RA-RNTI CCCH Temporary C-RNTI BCCH SI-RNTI © 2009 EventHelix.com Inc. 18
  • 19. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems Random Access Procedure Contention Resolution Uplink control message is transmitted on the granted uplink resource and the contention resolution timer is started The contention resolution timer is stopped when the lower layers indicate that the message has been acknowledged Random Access Response Reception on PDCCH Match the preamble to receive the response Apply the timing advance in the message Process uplink resource grant Random Access Preamble Transmission Set Preamble Target Power Ask Physical Layer to Transmit Preamble Random Access Resource Selection Select Random Access Preamble Determine the next available PRACH Sub-frame © 2009 EventHelix.com Inc. 19
  • 20. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems DL-SCH Data Transfer Data Delivery and Acknowledgement If data in the Soft buffer is successfully decoded and no error is detected, send positive acknowledgement If data decoding in the Soft buffer results in an error, a negative acknowledgement is sent. Hybrid ARQ Operation If received NDI != previous NDI or first transmission: Soft buffer contents are replaced with new data If received NDI == previous NDI: Soft buffer data is chase combined with the new data Downlink Assignment Received on PDCCH Message indicates if there is transmission on the DL- SCH for the UE. New Data Indicator (NDI) is updated © 2009 EventHelix.com Inc. 20
  • 21. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems UL-SCH Data Transfer UE transmits the uplink data on the assigned resources. Hybrid ARQ is used. Uplink Grant assigns uplink resources for transmission Power Headroom Report (PHR) communicates the additional return power available at the UE. Buffer Status Report (BSR) is sent to report pending data in uplink buffers. Scheduling Request (SR) is sent to initiate uplink data transfer. © 2009 EventHelix.com Inc. 21
  • 22. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems Explore More Specification Title 3GPP TS 36.300 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 3GPP TS 36.321 Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocol specification 3GPP TS 36.211 Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation © 2009 EventHelix.com Inc. 22
  • 23. EventHelix.com • telecommunication design • systems engineering • real-time and embedded systems Thank You Links Description EventStudio System Designer 4.0 Sequence diagram based systems engineering tool. VisualEther Protocol Analyzer 1.0 Wireshark based visual protocol analysis and system design reverse engineering tool. Telecom Call Flows GSM, SIP, H.323, ISUP, LTE and IMS call flows. TCP/IP Sequence Diagrams TCP/IP explained with sequence diagrams. Real-time and Embedded System Articles Real-time and embedded systems, call flows and object oriented design articles. © 2009 EventHelix.com Inc. 23 Thank you for visiting EventHelix.com. The following links provide more information about telecom design tools and techniques: