Erik Dahlman
`Stefan Parkvall
`Johan Skold
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`4G LTE/LTE-Advanced
`for Mobile Broadband
`
`IPR2019-00128
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`

`

`4G LTE/LTE-Advanced
`for Mobile Broadband
`
`Erik Dahlman, Stefan Parkvall, and
`Johan Sköld
`
`AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD
`PARIS • SAN DIEGO • SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO
`
`Academic Press is an imprint of Elsevier
`
`IPR2019-00128
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`

`

`|PR2019-00128
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`Qualcomm 2021, p. 4
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`IPR2019-00128
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`

`

`Academic Press is an imprint of Elsevier
`The Boulevard, Langford Lane, Kidlington, Oxford, OX5 1GB, UK
`30 Corporate Drive, Suite 400, Burlington, MA 01803, USA
`
`First published 2011
`
`Copyright © 2011 Erik Dahlman, Stefan Parkvall & Johan Sköld. Published by Elsevier Ltd. All rights reserved
`
`The rights of Erik Dahlman, Stefan Parkvall & Johan Sköld to be identified as the authors of this work has been
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`Sc1bre Foundc1tion
`
`IPR2019-00128
`Qualcomm 2021, p. 5
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`

`

`Preface
`
`During the past years, there has been a quickly rising interest in radio access technologies for pro-
`viding mobile as well as nomadic and fixed services for voice, video, and data. The difference in
`design, implementation, and use between telecom and datacom technologies is also becoming more
`blurred. One example is cellular technologies from the telecom world being used for broadband data
`and wireless LAN from the datacom world being used for voice-over IP.
`Today, the most widespread radio access technology for mobile communication is digital cellular,
`with the number of users passing 5 billion by 2010, which is more than half of the world’s popula-
`tion. It has emerged from early deployments of an expensive voice service for a few car-borne users,
`to today’s widespread use of mobile-communication devices that provide a range of mobile services
`and often include camera, MP3 player, and PDA functions. With this widespread use and increasing
`interest in mobile communication, a continuing evolution ahead is foreseen.
`This book describes LTE, developed in 3GPP (Third Generation Partnership Project) and provid-
`ing true 4G broadband mobile access, starting from the first version in release 8 and through the con-
`tinuing evolution to release 10, the latest version of LTE. Release 10, also known as LTE-Advanced,
`is of particular interest as it is the major technology approved by the ITU as fulfilling the IMT-
`Advanced requirements. The description in this book is based on LTE release 10 and thus provides a
`complete description of the LTE-Advanced radio access from the bottom up.
`Chapter 1 gives the background to LTE and its evolution, looking also at the different standards
`bodies and organizations involved in the process of defining 4G. It also gives a discussion of the rea-
`sons and driving forces behind the evolution.
`Chapters 2–6 provide a deeper insight into some of the technologies that are part of LTE and its
`evolution. Because of its generic nature, these chapters can be used as a background not only for LTE
`as described in this book, but also for readers who want to understand the technology behind other
`systems, such as WCDMA/HSPA, WiMAX, and CDMA2000.
`Chapters 7–17 constitute the main part of the book. As a start, an introductory technical over-
`view of LTE is given, where the most important technology components are introduced based on
`the generic technologies described in previous chapters. The following chapters provide a detailed
`description of the protocol structure, the downlink and uplink transmission schemes, and the associ-
`ated mechanisms for scheduling, retransmission and interference handling. Broadcast operation and
`relaying are also described. This is followed by a discussion of the spectrum flexibility and the associ-
`ated requirements from an RF perspective.
`Finally, in Chapters 18–20, an assessment is made on LTE. Through an overview of similar tech-
`nologies developed in other standards bodies, it will be clear that the technologies adopted for the
`evolution in 3GPP are implemented in many other systems as well. Finally, looking into the future,
`it will be seen that the evolution does not stop with LTE-Advanced but that new features are continu-
`ously added to LTE in order to meet future requirements.
`
`xiii
`
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`

`

`Acknowledgements
`
`We thank all our colleagues at Ericsson for assisting in this project by helping with contributions to
`the book, giving suggestions and comments on the contents, and taking part in the huge team effort of
`developing LTE.
`The standardization process involves people from all parts of the world, and we acknowledge the
`efforts of our colleagues in the wireless industry in general and in 3GPP RAN in particular. Without
`their work and contributions to the standardization, this book would not have been possible.
`Finally, we are immensely grateful to our families for bearing with us and supporting us during
`the long process of writing this book.
`
`xv
`
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`IPR2019-00128
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`

`

`Abbreviations and Acronyms
`
`3GPP
`3GPP2
`
`ACIR
`ACK
`ACLR
`ACS
`AM
`AMC
`A-MPR
`AMPS
`AQPSK
`ARI
`ARIB
`ARQ
`AS
`ATIS
`AWGN
`
`BC
`BCCH
`BCH
`BER
`BLER
`BM-SC
`BPSK
`BS
`BSC
`BTS
`
`CA
`CC
`
`CCCH
`CCE
`CCSA
`CDD
`CDF
`CDM
`CDMA
`
`Third Generation Partnership Project
`Third Generation Partnership Project 2
`
`Adjacent Channel Interference Ratio
`Acknowledgement (in ARQ protocols)
`Adjacent Channel Leakage Ratio
`Adjacent Channel Selectivity
`Acknowledged Mode (RLC configuration)
`Adaptive Modulation and Coding
`Additional Maximum Power Reduction
`Advanced Mobile Phone System
`Adaptive QPSK
`Acknowledgement Resource Indicator
`Association of Radio Industries and Businesses
`Automatic Repeat-reQuest
`Access Stratum
`Alliance for Telecommunications Industry Solutions
`Additive White Gaussian Noise
`
`Band Category
`Broadcast Control Channel
`Broadcast Channel
`Bit-Error Rate
`Block-Error Rate
`Broadcast Multicast Service Center
`Binary Phase-Shift Keying
`Base Station
`Base Station Controller
`Base Transceiver Station
`
`Carrier Aggregation
` Convolutional Code (in the context of coding), or Component Carrier (in the
`context of carrier aggregation)
`Common Control Channel
`Control Channel Element
`China Communications Standards Association
`Cyclic-Delay Diversity
`Cumulative Density Function
`Code-Division Multiplexing
`Code-Division Multiple Access
`
`xvii
`
`IPR2019-00128
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`

`

`xviii
`
`Abbreviations and Acronyms
`
`CEPT
`CN
`CoMP
`CP
`CPC
`CQI
`C-RAN
`CRC
`C-RNTI
`CRS
`CS
`CS
`CSA
`CSG
`CSI
`CSI-RS
`CW
`
`European Conference of Postal and Telecommunications Administrations
`Core Network
`Coordinated Multi-Point transmission/reception
`Cyclic Prefix
`Continuous Packet Connectivity
`Channel-Quality Indicator
`Centralized RAN
`Cyclic Redundancy Check
`Cell Radio-Network Temporary Identifier
`Cell-specific Reference Signal
`Circuit Switched (or Cyclic Shift)
`Capability Set (for MSR base stations)
`Common Subframe Allocation
`Closed Subscriber Group
`Channel-State Information
`CSI reference signals
`Continuous Wave
`
`Downlink Assignment Index
`DAI
`Dedicated Control Channel
`DCCH
`Dedicated Channel
`DCH
`Downlink Control Information
`DCI
`Decision-Feedback Equalization
`DFE
`Discrete Fourier Transform
`DFT
`DFTS-OFDM DFT-Spread OFDM (DFT-precoded OFDM, see also SC-FDMA)
`DL
`Downlink
`DL-SCH
`Downlink Shared Channel
`DM-RS
`Demodulation Reference Signal
`DRX
`Discontinuous Reception
`DTCH
`Dedicated Traffic Channel
`DTX
`Discontinuous Transmission
`DwPTS
`The downlink part of the special subframe (for TDD operation).
`
`EDGE
`EGPRS
`eNB
`eNodeB
`EPC
`EPS
`ETSI
`E-UTRA
`E-UTRAN
`EV-DO
`EV-DV
`EVM
`
`Enhanced Data rates for GSM Evolution, Enhanced Data rates for Global Evolution
`Enhanced GPRS
`eNodeB
`E-UTRAN NodeB
`Evolved Packet Core
`Evolved Packet System
`European Telecommunications Standards Institute
`Evolved UTRA
`Evolved UTRAN
`Evolution-Data Only (of CDMA2000 1x)
`Evolution-Data and Voice (of CDMA2000 1x)
`Error Vector Magnitude
`
`IPR2019-00128
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`

`

`Abbreviations and Acronyms
`
`xix
`
`FACH
`FCC
`FDD
`FDM
`FDMA
`FEC
`FFT
`FIR
`FPLMTS
`FRAMES
`FSTD
`
`GERAN
`GGSN
`GP
`GPRS
`GPS
`GSM
`
`HARQ
`HII
`HLR
`HRPD
`HSDPA
`HSPA
`HSS
`HS-SCCH
`
`ICIC
`ICS
`ICT
`IDFT
`IEEE
`IFDMA
`IFFT
`IMT-2000
`
`IMT-Advanced
`
`IP
`IR
`IRC
`ITU
`ITU-R
`
`Forward Access Channel
`Federal Communications Commission
`Frequency Division Duplex
`Frequency-Division Multiplex
`Frequency-Division Multiple Access
`Forward Error Correction
`Fast Fourier Transform
`Finite Impulse Response
`Future Public Land Mobile Telecommunications Systems
`Future Radio Wideband Multiple Access Systems
`Frequency Switched Transmit Diversity
`
`GSM/EDGE Radio Access Network
`Gateway GPRS Support Node
`Guard Period (for TDD operation)
`General Packet Radio Services
`Global Positioning System
`Global System for Mobile communications
`
`Hybrid ARQ
`High-Interference Indicator
`Home Location Register
`High Rate Packet Data
`High-Speed Downlink Packet Access
`High-Speed Packet Access
`Home Subscriber Server
`High-Speed Shared Control Channel
`
`Inter-Cell Interference Coordination
`In-Channel Selectivity
`Information and Communication Technologies
`Inverse DFT
`Institute of Electrical and Electronics Engineers
`Interleaved FDMA
`Inverse Fast Fourier Transform
` International Mobile Telecommunications 2000 (ITU’s name for the family of
`3G standards)
` International Mobile Telecommunications Advanced (ITU’s name for the family
`of 4G standards)
`Internet Protocol
`Incremental Redundancy
`Interference Rejection Combining
`International Telecommunications Union
`International Telecommunications Union-Radiocommunications Sector
`
`IPR2019-00128
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`

`

`xx
`
`Abbreviations and Acronyms
`
`J-TACS
`
`Japanese Total Access Communication System
`
`LAN
`LCID
`LDPC
`LTE
`
`MAC
`MAN
`MBMS
`MBMS-GW
`MBS
`MBSFN
`MC
`MCCH
`MCE
`MCH
`MCS
`MDHO
`MIB
`MIMO
`ML
`MLSE
`MME
`MMS
`MMSE
`MPR
`MRC
`MSA
`MSC
`MSI
`MSP
`MSR
`MSS
`MTCH
`MU-MIMO
`MUX
`
`Local Area Network
`Logical Channel Index
`Low-Density Parity Check Code
`Long-Term Evolution
`
`Medium Access Control
`Metropolitan Area Network
`Multimedia Broadcast/Multicast Service
`MBMS gateway
`Multicast and Broadcast Service
`Multicast-Broadcast Single Frequency Network
`Multi-Carrier
`MBMS Control Channel
`MBMS Coordination Entity
`Multicast Channel
`Modulation and Coding Scheme
`Macro-Diversity Handover
`Master Information Block
`Multiple-Input Multiple-Output
`Maximum Likelihood
`Maximum-Likelihood Sequence Estimation
`Mobility Management Entity
`Multimedia Messaging Service
`Minimum Mean Square Error
`Maximum Power Reduction
`Maximum Ratio Combining
`MCH Subframe Allocation
`Mobile Switching Center
`MCH Scheduling Information
`MCH Scheduling Period
`Multi-Standard Radio
`Mobile Satellite Service
`MBMS Traffic Channel
`Multi-User MIMO
`Multiplexer or Multiplexing
`
`NAK, NACK
`NAS
`
`NDI
`NSPS
`NMT
`
`Negative Acknowledgement (in ARQ protocols)
` Non-Access Stratum (a functional layer between the core network and the terminal
`that supports signaling and user data transfer)
`New-data indicator
`National Security and Public Safety
`Nordisk MobilTelefon (Nordic Mobile Telephony)
`
`IPR2019-00128
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`
`

`

`Abbreviations and Acronyms
`
`xxi
`
` NodeB, a logical node handling transmission/reception in multiple cells.
`Commonly, but not necessarily, corresponding to a base station.
`Network Signaling
`
`Orthogonal Cover Code
`Orthogonal Frequency-Division Multiplexing
`Orthogonal Frequency-Division Multiple Access
`Overload Indicator
`Out-Of-Band (emissions)
`
`Peak-to-Average Power Ratio
`Peak-to-Average Ratio (same as PAPR)
`Per-Antenna Rate Control
`Physical Broadcast Channel
`Paging Control Channel
`Physical Control Format Indicator Channel
`Project Coordination Group (in 3GPP)
`Paging Channel
`Policy and Charging Rules Function
`Personal Communications Systems
`Personal Digital Assistant
`Personal Digital Cellular
`Physical Downlink Control Channel
`Packet Data Convergence Protocol
`Physical Downlink Shared Channel
`Packet Data Network
`Protocol Data Unit
`Proportional Fair (a type of scheduler)
`Packet-Data Network Gateway (also PDN-GW)
`Physical Hybrid-ARQ Indicator Channel
`Personal Handy-phone System
`Physical layer
`Physical Multicast Channel
`Precoding-Matrix Indicator
`Plain Old Telephony Services
`Physical Random Access Channel
`Physical Resource Block
`Paging RNTI
`Packet Switched
`Phase Shift Keying
`Primary Synchronization Signal
`Public Switched Telephone Networks
`Physical Uplink Control Channel
`
`NodeB
`
`NS
`
`OCC
`OFDM
`OFDMA
`OI
`OOB
`
`PAPR
`PAR
`PARC
`PBCH
`PCCH
`PCFICH
`PCG
`PCH
`PCRF
`PCS
`PDA
`PDC
`PDCCH
`PDCP
`PDSCH
`PDN
`PDU
`PF
`P-GW
`PHICH
`PHS
`PHY
`PMCH
`PMI
`POTS
`PRACH
`PRB
`P-RNTI
`PS
`PSK
`PSS
`PSTN
`PUCCH
`
`IPR2019-00128
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`

`

`xxii
`
`Abbreviations and Acronyms
`
`PUSC
`PUSCH
`
`QAM
`QoS
`QPP
`QPSK
`
`RAB
`RACH
`RAN
`RA-RNTI
`RAT
`RB
`RE
`RF
`RI
`RIT
`RLC
`RNC
`RNTI
`RNTP
`ROHC
`R-PDCCH
`RR
`RRC
`RRM
`RS
`RSPC
`RSRP
`RSRQ
`RTP
`RTT
`RV
`RX
`
`S1
`S1-c
`S1-u
`SAE
`SCM
`SDMA
`SDO
`SDU
`SEM
`
`Partially Used Subcarriers (for WiMAX)
`Physical Uplink Shared Channel
`
`Quadrature Amplitude Modulation
`Quality-of-Service
`Quadrature Permutation Polynomial
`Quadrature Phase-Shift Keying
`
`Radio Access Bearer
`Random Access Channel
`Radio Access Network
`Random Access RNTI
`Radio Access Technology
`Resource Block
`Reseource Element
`Radio Frequency
`Rank Indicator
`Radio Interface Technology
`Radio Link Control
`Radio Network Controller
`Radio-Network Temporary Identifier
`Relative Narrowband Transmit Power
`Robust Header Compression
`Relay Physical Downlink Control Channel
`Round-Robin (a type of scheduler)
`Radio Resource Control
`Radio Resource Management
`Reference Symbol
`IMT-2000 radio interface specifications
`Reference Signal Received Power
`Reference Signal Received Quality
`Real Time Protocol
`Round-Trip Time
`Redundancy Version
`Receiver
`
`The interface between eNodeB and the Evolved Packet Core.
`The control-plane part of S1
`The user-plane part of S1
`System Architecture Evolution
`Spatial Channel Model
`Spatial Division Multiple Access
`Standards Developing Organization
`Service Data Unit
`Spectrum Emissions Mask
`
`IPR2019-00128
`Qualcomm 2021, p. 14
`
`

`

`Abbreviations and Acronyms
`
`xxiii
`
`Spreading Factor
`Space-Frequency Block Coding
` Single-Frequency Network (in general, see also MBSFN) or System Frame Number
`(in 3GPP)
`Space–Frequency Time Diversity
`Serving GPRS Support Node
`Serving Gateway
`System Information message
`System Information Block
`Successive Interference Combining
`Subscriber Identity Module
`Signal-to-Interference-and-Noise Ratio
`Signal-to-Interference Ratio
`System Information RNTI
`Short Message Service
`Signal-to-Noise Ratio
`Soft Handover
`Spatial Orthogonal-Resource Transmit Diversity
`Scheduling Request
`Sounding Reference Signal
`Secondary Synchronization Signal
`Space–Time Block Coding
`Space–Time Coding
`Space-Time Transmit Diversity
`Single-User MIMO
`
`Total Access Communication System
`Transmission Control Protocol
`Temporary C-RNTI
`Time-Division Code-Division Multiple Access
`Time-Division Duplex
`Time-Division Multiplexing
`Time-Division Multiple Access
`Time-Division-Synchronous Code-Division Multiple Access
`Transport Format
`Telecommunications Industry Association
`Transparent Mode (RLC configuration)
`Technical Report
`Technical Specification
`Technical Specification Group
`Telecommunications Technology Association
`Telecommunications Technology Committee
`Transmission Time Interval
`Transmitter
`
`SF
`SFBC
`SFN
`
`SFTD
`SGSN
`S-GW
`SI
`SIB
`SIC
`SIM
`SINR
`SIR
`SI-RNTI
`SMS
`SNR
`SOHO
`SORTD
`SR
`SRS
`SSS
`STBC
`STC
`STTD
`SU-MIMO
`
`TACS
`TCP
`TC-RNTI
`TD-CDMA
`TDD
`TDM
`TDMA
`TD-SCDMA
`TF
`TIA
`TM
`TR
`TS
`TSG
`TTA
`TTC
`TTI
`TX
`
`IPR2019-00128
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`

`

`xxiv
`
`Abbreviations and Acronyms
`
`UCI
`UE
`UL
`UL-SCH
`UM
`UMB
`UMTS
`UpPTS
`US-TDMA
`UTRA
`UTRAN
`
`VAMOS
`VoIP
`VRB
`
`WAN
`WARC
`WCDMA
`WG
`WiMAX
`WLAN
`WMAN
`WP5D
`WRC
`
`X2
`
`ZC
`ZF
`
`Uplink Control Information
`User Equipment, the 3GPP name for the mobile terminal
`Uplink
`Uplink Shared Channel
`Unacknowledged Mode (RLC configuration)
`Ultra Mobile Broadband
`Universal Mobile Telecommunications System
`The uplink part of the special subframe (for TDD operation).
`US Time-Division Multiple Access standard
`Universal Terrestrial Radio Access
`Universal Terrestrial Radio Access Network
`
`Voice services over Adaptive Multi-user channels
`Voice-over-IP
`Virtual Resource Block
`
`Wide Area Network
`World Administrative Radio Congress
`Wideband Code-Division Multiple Access
`Working Group
`Worldwide Interoperability for Microwave Access
`Wireless Local Area Network
`Wireless Metropolitan Area Network
`Working Party 5D
`World Radiocommunication Conference
`
`The interface between eNodeBs.
`
`Zadoff-Chu
`Zero Forcing
`
`IPR2019-00128
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`
`

`

`Radio-Interface Architecture
`
`CHAPTER
`
`8
`
`This chapter contains a brief overview of the overall architecture of an LTE radio-access network
`and the associated core network, followed by descriptions of the radio-access network user-plane and
`control-plane protocols.
`
`8.1 OVERALL SYSTEM ARCHITECTURE
`In parallel to the work on the LTE radio-access technology in 3GPP, the overall system architecture
`of both the Radio-Access Network (RAN) and the Core Network (CN) was revisited, including the
`split of functionality between the two network parts. This work was known as the System Architecture
`Evolution (SAE) and resulted in a flat RAN architecture, as well as a new core network architecture
`referred to as the Evolved Packet Core (EPC). Together, the LTE RAN and the EPC can be referred to
`as the Evolved Packet System (EPS).1
`The RAN is responsible for all radio-related functionality of the overall network including, for
`example, scheduling, radio-resource handling, retransmission protocols, coding and various multi-
`antenna schemes. These functions will be discussed in detail in the subsequent chapters.
`The EPC is responsible for functions not related to the radio interface but needed for providing a
`complete mobile-broadband network. This includes, for example, authentication, charging functional-
`ity, and setup of end-to-end connections. Handling these functions separately, instead of integrating
`them into the RAN, is beneficial as it allows for several radio-access technologies to be served by the
`same core network.
`Although this book focuses on the LTE RAN, a brief overview of the EPC, as well as how it con-
`nects to the RAN, is useful. For an excellent in-depth discussion of EPC, the reader is referred to [9].
`
`8.1.1 Core Network
`The EPC is a radical evolution from the GSM/GPRS core network used for GSM and WCDMA/
`HSPA. EPC supports access to the packet-switched domain only, with no access to the circuit-
`switched domain. It consists of several different types of nodes, some of which are briefly described
`below and illustrated in Figure 8.1.
`
`1 UTRAN, the WCDMA/HSPA radio-access network, is also part of the EPS.
`
`4G LTE/LTE-Advanced for Mobile Broadband.
`
`© 2011 Erik Dahlman, Stefan Parkvall & Johan Sköld. Published by Elsevier Ltd. All rights reserved.2011
`
`109
`
`IPR2019-00128
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`
`

`

`110
`
`CHAPTER 8 Radio-Interface Architecture
`
`Internet
`
`Core Network
`
`MME
`
`MME
`
`S-GW
`
`S1-u
`
`S-GW
`
`S1-u
`
`S1-c
`
`S1-c
`
`S1-c
`
`S1-c
`
`S1-u
`
`S1-u
`
`eNodeB
`
`X2
`
`eNodeB
`
`q
`0---,
`' ' ' ' '
`
`HSS
`
`S6a
`
`MME
`
`S1-c
`
`SGi
`
`P-GW
`
`S5
`
`S-GW
`~---'
`
`S1-u
`
`S11
`
`RAN
`
`eNodeB
`
`FIGURE 8.1
`
`FIGURE 8.2
`
`Core-network (EPC) architecture.
`
`Radio-access-network interfaces.
`
`The Mobility Management Entity (MME) is the control-plane node of the EPC. Its responsibili-
`ties include connection/release of bearers to a terminal, handling of IDLE to ACTIVE transitions, and
`handling of security keys. The functionality operating between the EPC and the terminal is some-
`times referred to as the Non-Access Stratum (NAS), to separate it from the Access Stratum (AS)
`which handles functionality operating between the terminal and the radio-access network.
`The Serving Gateway (S-GW) is the user-plane node connecting the EPC to the LTE RAN. The
`S-GW acts as a mobility anchor when terminals move between eNodeBs (see next section), as well
`as a mobility anchor for other 3GPP technologies (GSM/GPRS and HSPA). Collection of information
`and statistics necessary for charging is also handled by the S-GW.
`The Packet Data Network Gateway (PDN Gateway, P-GW) connects the EPC to the internet.
`Allocation of the IP address for a specific terminal is handled by the P-GW, as well as quality-of-
`service enforcement according to the policy controlled by the PCRF (see below). The P-GW is also
`the mobility anchor for non-3GPP radio-access technologies, such as CDMA2000, connected to the
`EPC.
`In addition, the EPC also contains other types of nodes such as Policy and Charging Rules
`Function (PCRF) responsible for quality-of-service (QoS) handling and charging, and the Home
`Subscriber Service (HSS) node, a database containing subscriber information. There are also some
`additional nodes present as regards network support of Multimedia Broadcast Multicast Services
`(MBMS) (see Chapter 15 for a more detailed description of MBMS, including the related architecture
`aspects).
`It should be noted that the nodes discussed above are logical nodes. In an actual physical imple-
`mentation, several of them may very well be combined. For example, the MME, P-GW, and S-GW
`could very well be combined into a single physical node.
`
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`

`

`8.2 Radio Protocol Architecture
`
`111
`
`8.1.2 Radio-Access Network
`The LTE radio-access network uses a flat architecture with a single type of node2 – the eNodeB.
`The eNodeB is responsible for all radio-related functions in one or several cells. It is important to
`note that an eNodeB is a logical node and not a physical implementation. One common implemen-
`tation of an eNodeB is a three-sector site, where a base station is handling transmissions in three
`cells, although other implementations can be found as well, such as one baseband processing unit to
`which a number of remote radio heads are connected. One example of the latter is a large number of
`indoor cells, or several cells along a highway, belonging to the same eNodeB. Thus, a base station is a
`possible implementation of, but not the same as, an eNodeB.
`As can be seen in Figure 8.2, the eNodeB is connected to the EPC by means of the S1 interface,
`more specifically to the S-GW by means of the S1 user-plane part, S1-u, and to the MME by means
`of the S1 control-plane part, S1-c. One eNodeB can be connected to multiple MMEs/S-GWs for the
`purpose of load sharing and redundancy.
`The X2 interface, connecting eNodeBs to each other, is mainly used to support active-mode
`mobility. This interface may also be used for multi-cell Radio Resource Management (RRM) func-
`tions such as Inter-Cell Interference Coordination (ICIC) discussed in Chapter 13. The X2 interface
`is also used to support lossless mobility between neighboring cells by means of packet forwarding.
`
`8.2 RADIO PROTOCOL ARCHITECTURE
`With the overall network architecture in mind, the RAN protocol architecture for the user as well as
`the control planes can be discussed. Figure 8.3 illustrates the RAN protocol architecture (the MME is,
`as discussed in the previous section, not part of the RAN but is included in the figure for complete-
`ness). As seen in the figure, many of the protocol entities are common to the user and control planes.
`Therefore, although this section mainly describes the protocol architecture from a user-plane perspec-
`tive, the description is in many respects also applicable to the control plane. Control-plane-specific
`aspects are discussed in Section 8.3.
`The LTE radio-access network provides one or more Radio Bearers to which IP packets are
`mapped according to their Quality-of-Service requirements. A general overview of the LTE (user-
`plane) protocol architecture for the downlink is illustrated in Figure 8.4. As will become clear in the
`subsequent discussion, not all the entities illustrated in Figure 8.4 are applicable in all situations. For
`example, neither MAC scheduling nor hybrid ARQ with soft combining is used for broadcast of the
`basic system information. The LTE protocol structure related to uplink transmissions is similar to the
`downlink structure in Figure 8.4, although there are some differences with respect to, for example,
`transport-format selection.
`The different protocol entities of the radio-access network are summarized below and described in
`more detail in the following sections.
`
`l Packet Data Convergence Protocol (PDCP) performs IP header compression to reduce the
`number of bits to transmit over the radio interface. The header-compression mechanism is based
`
`2 The introduction of MBMS (see Chapter 15) in release 9 and relaying (see Chapter 16) in release 10 brings additional
`node types to the RAN.
`
`IPR2019-00128
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`

`

`112
`
`CHAPTER 8 Radio-Interface Architecture
`
`UE
`
`eNodeB
`
`MME
`
`;:::::=~r--------------------------i-----------------------------------•..__I _
`NAS
`NAS
`~~=~1----------------------------+1
`RRC
`RRC
`:=====~)-----------------!
`.
`:====:)-----------------!::====~
`:====:)-----------------!::====~
`~-~)-----------------! _____ __,
`
`PDCP
`
`RLC
`
`MAC
`
`PHY
`
`PDCP
`
`RLC
`
`MAC
`
`PHY
`
`User plane Control plane
`
`User plane Control plane
`
`FIGURE 8.3
`
`Overall RAN protocol architecture.
`
`IP packet
`
`IP packet
`
`User #i
`
`PDCP
`
`Header Compr.
`
`Ciphering
`
`RLC
`
`PDCP
`
`Header Decompr.
`
`Deciphering
`
`Radio Bearers
`
`RLC
`
`version
`
`Redundancy
`
`Payload selection
`
`Segmentation, ARQ
`
`Reassembly, ARQ
`
`Priority handling,
`payload selection
`
`MAC
`
`Retransmission
`control
`
`MAC multiplexing
`
`Hybrid ARQ
`
`Logical Channels
`
`MAC
`
`MAC demultiplexing
`
`Hybrid ARQ
`
`PHY
`
`Transport Channels
`
`PHY
`
`Scheduler
`
`Modulation
`scheme
`
`Antenna and
`resource
`assignment
`
`Coding
`
`Modulation
`
`Antenna and
`resource mapping
`
`Decoding
`
`Demodulation
`
`Antenna and
`resource mapping
`
`eNodeB
`
`terminal (UE)
`
`FIGURE 8.4
`
`LTE protocol architecture (downlink).
`
`IPR2019-00128
`Qualcomm 2021, p. 20
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`

`

`8.2 Radio Protocol Architecture
`
`113
`
`on Robust Header Compression (ROHC) [68], a standardized header-compression algorithm also
`used for several mobile-communication technologies. PDCP is also responsible for ciphering and,
`for the control plane, integrity protection of the transmitted data, as well as in-sequence delivery
`and duplicate removal for handover. At the receiver side, the PDCP protocol performs the corre-
`sponding deciphering and decompression operations. There is one PDCP entity per radio bearer
`configured for a terminal.
`l Radio-Link Control (RLC) is responsible for segmentation/concatenation, retransmission hand-
`ling, duplicate detection, and in-sequence delivery to higher layers. The RLC provides services to
`the PDCP in the form of radio bearers. There is one RLC entity per radio bearer configured for a
`terminal.
`l Medium-Access Control (MAC) handles multiplexing of logical channels, hybrid-ARQ retrans-
`missions, and uplink and downlink scheduling. The scheduling functionality is located in the
`eNodeB for both uplink and downlink. The hybrid-ARQ protocol part is present in both the trans-
`mitting and receiving ends of the MAC protocol. The MAC provides services to the RLC in the
`form of logical channels.
`l Physical Layer (PHY) handles coding/decoding, modulation/demodulation, multi-antenna map-
`ping, and other typical physical-layer functions. The physical layer offers services to the MAC
`layer in the form of transport channels.
`
`To summarize the flow of downlink data through all the protocol layers, an example illustration
`for a case with three IP packets, two on one radio bearer and one on another radio bearer, is given in
`Figure 8.5. The data flow in the case of uplink transmission is similar. The PDCP performs (optional)
`IP-header compression, followed by ciphering. A PDCP header is added, carrying information
`required for deciphering in the terminal. The output from the PDCP is forwarded to the RLC.
`The RLC protocol performs concatenation and/or segmentation of the PDCP SDUs3 and adds an
`RLC header. The header is used for in-sequence delivery (per logical channel) in the terminal and
`for identification of RLC PDUs in the case of retransmissions. The RLC PDUs are forwarded to
`the MAC layer, which multiplexes a number of RLC PDUs and attaches a MAC header to form a
`transport block. The transport-block size depends on the instantaneous data rate selected by the link-
`adaptation mechanism. Thus, the link adaptation affects both the MAC and RLC processing. Finally,
`the physical layer attaches a CRC to the transport block for error-detection purposes, performs coding
`and modulation, and transmits the resulting signal, possibly using multiple transmit antennas.
`The remainder of the chapter contains an overview of the RLC, MAC, and physical layers. A
`more detailed description of the LTE physical-layer processing is given in Chapters 10 (downlink)
`and 11 (uplink), followed by descriptions of some specific uplink and downlink radio-interface func-
`tions and procedures in the subsequent chapters.
`
`8.2.1 Radio-Link Control
`The RLC protocol is responsible for segmentation/concatenation of (header-compressed) IP pack-
`ets, also known as RLC SDUs, from the PDCP into suitably sized RLC PDUs. It also handles
`
`3 In general, the data entity from/to a higher protocol layer is known as a Service Data Unit (SDU) and the corresponding
`entity to/from a lower protocol layer entity is called a Protocol Data Unit (PDU).
`
`IPR2019-00128
`Qualcomm 2021, p. 21
`
`

`

`PDCP
`
`'
`
`'
`
`',,
`
`PDCP
`header
`....................................................... !'..........
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`RLC
`
`,
`
`' ,
`
`PDCP SDU
`
`PDCP SDU
`
`'
`
`'
`
`',,
`PDCP
`header
`
`RLC SDU
`
`RLC SDU
`
`I
`
`,
`
`'
`
`'
`
`I
`
`' , :
`
`
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`·- .=l =~r ·-.=:==r ===:::Ir· '
`r •
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`
`I
`
`Radio Bearer 1
`
`header
`l=t
`
`Payload
`
`I
`
`Radio Bearer 1
`
`header
`
`Payload
`
`I
`
`I
`
`:
`
`Radio Bearer 2
`
`Payload
`
`I
`
`r
`header
`•
`'
`
`PDCP SDU
`
`I
`
`I
`
`:
`
`I
`
`r
`
`I
`
`r
`_
`
`PDCP
`header
`
`I
`
`'
`
`"
`~
`
`/
`
`II
`
`RLC SDU
`
`/ <.._
`
`I
`
`' ,
`
`.,
`~
`
`(-
`
`' , ,
`' , ,
`
`RLC
`RLC
`RLC
`header
`header
`header
`- -~-- .. - - - - -~-v - -~-- -
`'~ -~ -
`'
`L
`I
`I
`I
`MAC
`MAC
`MAC
`header
`header
`•
`'
`'
`'
`'
`'
`I
`
`MAC SDU
`
`MAC SDU
`
`PHY
`
`FIGURE 8.5
`
`Example of LTE data flow.
`
`Transport Blo