2014년 이동 및 무선통신 단기강좌
3GPP LTE(-A): Part IILTE System MAC/Network Layer
2014. 8. 29.Jae-Hyun [email protected]
Wireless Internet aNd Network Engineering Research Lab.http://winner.ajou.ac.kr
School of Electrical and Computer Engineering Ajou University, Korea
Contents
LTE network overview• Standardization of LTE• LTE Network Architecture
User plane protocol• Packet Data Convergence Protocol• Radio Link Control• Medium Access Control
Control plane protocol• C-Plane Overview• Mobility Control• Radio Resource Management• Summary of C-Plane: Initial Attach Procedure
2
Introduction
3
LTE network overviewStandardization of LTELTE Network Architecture
4
3GPP Standard Documents
5
3GPP TS 36.300 overview
6
Title 3GPP TS 36.300
Scope Overview and overall description of E-UTRAN radio interface
protocol
Contentssection contents
4 Overall Architecture
5 Physical Layer계층별기능 및구조
6 Layer 2
7 RRC
8 E-UTRAN identities
주요 기능 설명
9 ARQ and HARQ
10 Mobility
11 Scheduling and Rate Control
12 DRX in RRC_CONNECTED
13 QoS
section contents
14 Security
주요 기능 설명
15 MBMS
16Radio Resource Management
aspects
17 Void
18 UE capabilities
19 S1 interface 인터페이스 별 프로토콜설명
20 X2 interface
21 Void
22Support for Self-configuration and
Self-optimization
23 Others
LTE Channel Architecture
7
PDCP: Packet Data Convergence Protocol SRB: Signalling Radio Bearer PCCH: Paging Control Channel
BCCH: Broadcast Control Channel CCCH: Common Control Channel DCCH: Dedicated Control Channel
PCH: Paging Channel BCH: Broadcast Channel RACH: Random Access Channel
DL-SCH: DownLink Shared CHannel UL-SCH: UpLink Shared Channel PBCH: Physical Broadcast Channel
PRACH: Physical Random Access Channel PDSCH: Physical Downlink Shared Channel PUSCH: Physical Uplink Shared Channel
LTE network overviewStandardization of LTELTE Network Architecture
8
Evolution of Network Architecture
9
cdma2000 Solutions Evolution :Reference Architecture for Voice Traffic
10
IP
64k PCM/32K ADPCM
PCM
BTS
ATMAAL2
ATM
Packet Pipes ATM
PCM/ Channelized T1
PSAXPSAXPSAX
MSCPSTN
Media Gateway
PSAXPSAXPSAX
MSC
BTS
ATMAAL2
ATM
Packet Pipes
PCM
Media Gateway
APX8000
Voice call Flow
64k PCM/32K ADPCM100BT
Ethernet
GX550 GX550
1
2 3
1
1 TDM
2
3
ATM :PCM 64 kbps
ATM :ADPCM 32 kbps
Tandem Tandem
4
4 IP :G.726 32 kbps
100BTEthernet
TMX880 TMX880
APX8000
RNCRNC5
5 IP :Vocoder bypass
2.5G
3G
3G+
UMTS Architecture(Release 99)
3GPP Release 1999 Network Architecture
11
RNC
RNC
BSC
SGSN
MSCVLR
Iub (ATM)
Node B
Node BPSTN
SS7
HLR
GGSN Internet
Iub (ATM)
Iu-ps (ATM)
Iu-ps (ATM)
Iu-ps (ATM)
Iu-cs (ATM)
Iu-cs (ATM)
A-interface
Gn(GTP/IP) Gi(IP)
BTS
UE
Uu
Iur (ATM)
UMTS Architecture(Release-4)
3GPP Release 4 Network Architecture
12
RNC
RNC
SGSN
MGW
Node B
Node B
PSTN
SS7
HSSHLR
GGSN Internet
IubIu-ps
Gn(GTP/IP) Gi(IP)
IurIu-cs(bearer)
MSC Server
GMSC Server
MGW
SS7 GW
SS7 GW
PCM
Iu-cs(control)
H248/IP H248/IP
RTP/IP
IP
Iub
HSS Home Subscriber Server MGW : Media Gateway
UMTS Architecture(Release-5)
13
RNC
RNC SGSN
Node B
PSTN
SS7
HSSHLR
GGSN
InternetGi(IP)
Iur
Iu
CSCF
R-SGW
PCMGn
Cx
Iub
MGWGi
CSCF
MGCFMg
T-SGW
SS7
McGrMRF
Mr
Gi
RNC : Radio Network Controller SGSN : Serving GPRS Support Node GGSN : Gateway GPRS Support Node CSCF : Call State Control Function MGCF : Media Gateway Control Function MRF : Multimedia Resource Function
SS7 : Signal System No.7 R-SGW : Roaming Signaling Gateway T-SGW : Transport Signaling Gateway
Radio Access Network (RAN)(UTRAN)
3G Core Network (CN) External Network
LTE- Evolution Path of Core Network
14
E-UTRAN(Evolved Universal Terrestrial Radio Access Network)
X2
S1
• NB : NodeB• RNC : Radio Network Controller• SGSN : Serving GPRS Support Node• GGSN : Gateway GPRS Support Node
• eNB : E-UTRAN NodeB• aGW : Access Gateway• MME : Mobility Management Entity• UPE : User Plane Entity
Overall Architectural Overview
EPS (Evolved Packet System) network elements
15
Evolved Packet Core (EPC)E-UTRAN
3GPP TS 36.300 V11.6.0 “E-UTRA and E-UTRAN; Overall description”, June, 2013
Interface for data planeInterface for control plane
E-SMLC: Evolved Serving Mobile Location Centre GMLC: Gateway Mobile Location Centre
HSS: Home Subscriber Server PCRF: Policy Control and Charging Rules Function
Core Network Elements
16
Network Elements Features
PCRF(Policy Control and Charging Rules Function)
Policy control decision making Controlling the flow-based charging functionalities in the PCEF (Policy Control
Enforcement Function) which resides in the P-GW• QoS authorization (QoS class identifier and bit rates)
HSS(Home Subscriber Server)
Contains users’ SAE subscription data such as EPS-subscribed QoS profile and any access restrictions for roaming
Information about the PDNs to which the user can connect Identity of the MME to which the user is currently attached or registered
E-SMLC(Evolved Serving Mobile Location Centre)
Manage the overall coordination and scheduling of resources required to find the location of a UE attached to E-UTRAN
Calculate the final location of UE based on the estimates it receives Estimate the UE speed and the achieved accuracy
GMLC (Gateway Mobile Location Centre)
Contain functionalities required to support location services Send positioning requests to the MME and receives the final location estimates
Core Network Elements
17
Network Elements Features
P-GW (PDN Gateway) IP address allocation for the UE QoS enforcement and flow-based charging according to the PCRF
S-GW (Serving Gateway)
All user IP packets are transferred through the S-GW LMA (Local Mobility Anchor) when the UE moves between eNode-Bs Retains the information about the bearers when the UE is in idle state Temporarily buffers downlink data while the MME initiates paging of the UE to
re-establish the bearers Collecting information for charging (the volume of data sent/rcvd) Mobility anchor for inter-working with GPRS and UMTS
MME(Mobility Management Entity)
Process the signaling between the UE and the CN (Core Network) (NAS: Non-Access Stratum)
Bearer & Connection management• Establishment, maintenance and release of the bearers• Establishment of the connection and security between the network and
UE
Access Network
Overall Network Architecture E-UTRAN consists of eNBs eNBs are interconnected with each other by X2 interface eNBs are connected by means of S1 interface to the EPC S1 interface supports a many-to-many relation between MMEs/S-GW
and eNBs
18 3GPP TS 36.300 V11.6.0 “E-UTRA and E-UTRAN; Overall description”, June, 2013
S1 S1
S1 S1X2X2 S1
S1
S1 S5
S1
Access Network
The eNB hosts following functions RRM (Radio Resource Management)
Radio Bearer Control Radio Admission Control Connection Mobility Control Dynamic allocation of resources to UEs (scheduling)
Processing user plane data IP header compression and encryption of user data stream AS security Selection of an MME at UE attachment when no routing to an MME
can be determined from the information provided by the UE Forwarding of user plane data towards S-GW
Measurement and measurement reporting configuration for mobility and scheduling
Scheduling and transmission of control messages from the MME paging messages broadcast information PWS (Public Warning System) messages
CSG (Closed Subscriber Group) handling
Transport level packet marking in the uplink (ex. Setting the DSCP (DiffServ Code Point)
19 3GPP TS 36.300 V11.6.0 “E-UTRA and E-UTRAN; Overall description”, June, 2013
Access Network: User Plane U-Plane PDCP (Packet Data Convergence Protocol) RLC (radio Link Control)MAC (Medium Access Control) GTP (GPRS Tunneling Protocol) on the S1 (eNB↔S-GW) on the S5/S8 (S-GW ↔ P-GW)
20
• C-Plane
S5/S8a
eNB
LTE-Uu
UEApplication
IP
PDCP
L1
MAC
RLC
S1-U
PDCP
L1
MAC
RLC
GTP-U
L1
L2
UDP/IP
S-GWGTP-U
L1
L2
UDP/IP
GTP-U
L1
L2
UDP/IP
P-GW
IP
GTP-U
L1
L2
UDP/IP
SGi
Servers PDNApplication
IP
Access Network: Control Plane C-Plane Idle state Cell selection/reselection(based on radio link quality, cell status,
radio access technology), paging ,system information acquisition
Connected state RRC(radio resource control): CH quality, neighboring cell
information, mobility procedures
21
eNB
LTE-Uu
UENAS
RRC
PDCP
L1
MAC
RLC
S1-MME
PDCP
L1
MAC
RLC
SCTP
L1
L2
IP
RRC S1-AP
MMENAS
S1-AP
SCTP
L1
L2
IPAS
Interfaces
X2 and S1 user plane aspect IP packet for a UE is encapsulated and tunneled using GTP-U (GPRS Tunneling
Protocol – User Plane) Local transport protocol is UDP
• No flow control, No error control
X2 and S1 control plane aspect S1AP (S1 Application Protocol) is used to transport the signaling message
between eNode-B and the MME Local transport protocol is SCTP
• Guarantees delivery of signaling messages• Support multiple SAE bearers
22
User plane for S1-U interface Control plane for S1-MME Interface
3GPP TS 36.300 V11.6.0 “E-UTRA and E-UTRAN; Overall description”, June, 2013
SCTP : Stream Control Transmission Protocol
EPS Bearer Service Architecture
EPS bearer / E-RAB is established when the UE connects to a PDN Default bearer remains established throughout the lifetime of the PDN connection
Dedicated bearer Any additional EPS bearer/E-RAB that is established to the same
PDN is referred to as a dedicated bearer.
23
P-GWS-GW PeerEntity
UE eNB
EPS Bearer
Radio Bearer S1 Bearer
End-to-end Service
External Bearer
Radio S5/S8
Internet
S1
E-UTRAN EPC
Gi
E-RAB S5/S8 Bearer
3GPP TS 36.300 V11.6.0 “E-UTRA and E-UTRAN; Overall description”, June, 2013
QoS and EPS Bearers
Multiple applications have different QoSrequirements Different bearers are set up within EPS each being associated with a QoS
GBR bearers Permanent allocation of dedicated transmission resources ex) VoIP
Non-GBR bearers Do not guarantee any particular bit rate ex) web browsing, FTP transfer
Each bearer has an associated QCI, and an ARP Priority and packet delay budget RLC mode, scheduling policy, queue management and rate shaping policy
24GBR : Minimum Guaranteed Bit Rate QCI: QoS Class Identifier ARP: Allocation and Retention Priority
Standardized QCI for LTE
QCI(QoS Class Identifier)
ResourceType
Priority
PacketDelay
Budget
PacketError Loss
RateExample Services
1
GBR
2 100ms 10-2 Conversational Voice
2 4 150ms 10-3 Conversational Video (Live Streaming)
3 3 50ms 10-3 Real Time Gaming
4 5 300ms 10-6 Non-Conversational Video (Buffered Streaming)
5
Non-GBR
1 100ms 10-6 IMS Signaling
6 6 300ms 10-6Video (Buffered Streaming),TCP-based (e.g., www, e-mail, chat, ftp, p2p file sharing,
progressive video, etc.)
7 7 100ms 10-3 Voice, Video (Live Streaming)Interactive Gaming
8 8300ms 10-6
Video (Buffered Streaming),TCP-based (e.g., www, e-mail, chat, ftp, p2p file sharing,
progressive video, etc.)9 9
25 3GPP TS 23.203 v12.1.0, “Policy and charging control architecture,” Jun. 2013.
User Plane ProtocolPacket Data Convergence ProtocolRadio Link ControlMedium Access Control
26
Overview of User Plane Protocol
PDCP layer Process RRC messages in the control plane and IP
messages in the user plane Header compression Security reordering and retransmission during handover
RLC layer Segmentation and reassembly ARQ Reordering for HARQ
MAC layer Multiplexing of data from different radio bearer Achieve QoS for each radio bearer Report the eNodeB to the buffer size for uplink
27
PDCP : Packet Data Convergence Protocol RLC: Radio Link Control MAC: Medium Access Control HARQ : Hybrid Automatic Repeat RequestQoS : Quality of Service
S5/S8a
eNB
LTE-Uu
UEApplication
IP
PDCP
L1
MAC
RLC
S1-U
PDCP
L1
MAC
RLC
GTP-U
L1
L2
UDP/IP
S-GWGTP-U
L1
L2
UDP/IP
GTP-U
L1
L2
UDP/IP
P-GW
IP
GTP-U
L1
L2
UDP/IP
SGi
Servers PDNApplication
IP
PDCP overview
Functions Header compression/
decompression of user plane data
Security Ciphering and deciphering for
user plane and control plane data Integrity protection and
verification for control plane data
Handover support In-sequence delivery and
reordering of upper layer PDUs at handover
Lossless handover for user plane data mapped on RLC Acknowledge Mode (AM)
Discard for timeout user plane data
28
* 3GPP TS 36.323 v11.2.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Packet Data Convergence Protocol (PDCP) specification”(Release 11), April, 2013
Header Compression
Robust Header Compression (ROHC) Introduced RFC 3095 and RFC 4815 Increase channel efficiency by reducing overhead Robust at unreliable link Three different mode : Unidirectional mode(U-mode), Bidirectional
Optimistic mode(O-mode), and Bidirectional Reliable mode(R-mode) Compression example VoIP (in the active period)
• payload 5,11~32 bytes ([email protected]~12.2kbps)+ header 40/60 bytes (RTP 12+UDP 8+IPv4 20/IPv6 40) payload 32 bytes + header 4~6 bytes
29 acticom mobile networks, http://www.acticom.de/en/
Wireless Link
Payload RTP UDP IP
CompressorDe-Compressor
Framing/Error Detection
RoHC Context
Payload H
CompressedHeader
RoHC Context
PayloadIP RTP UDP
CompressorDe-Compressor
Framing/Error Detection
Sender Receiver
Header Compression
Header Fields Classification
30
Type DescriptionInferred” They are never sent and they can
be known by other component in the header
Static* Send only once, their valuesnever change during the stream
Static-def**
Send only once, they give the definition of the stream
Static-known^
They are never sent and their values are known
Changing< Header fields with a changing value. The change can be periodic or randomly. They are always send
Ver*
ToS< Flow ID**Length” Next
Header* Hop Limit<
Source Address**
Destination Address**
Source Port** Destination Port**Length” Checksum<
Ver^ P* E* CCnt< M< P.Type< Sequence Number<
Timestamp<
Source Synchronization Indentification(SSRC)**
Source Contribution Identification (1st)<
Contributing source (CSRC)<
Source Contribution Identification (last)<
Application Data
0 15 31
IPv6
UDP
RTP
Header Compression
Header Fields Classification
31
Type DescriptionInferred” They are never sent and they can
be known by other component in the header
Static* Send only once, their valuesnever change during the stream
Static-def**
Send only once, they give the definition of the stream
Static-known^
They are never sent and their values are known
Changing< Header fields with a changing value. The change can be periodic or randomly. They are always send
Static Info
ROHC header
Application Data
1 byte
3~5 bytes
Header Compression
ROHC compression with U,O,R operation mode
32
Security
LTE security distribution NAS security Carried out for NAS messages / between UE and MME NAS messages are integrity protected and ciphered with extra NAS
security header
AS security (PDCP) Carried out for RRC and user plane data / between UE and eNB RRC messages are integrity protected and ciphered U-plane data is only ciphered
33 3GLTEINFO, http://www.3glteinfo.com/lte-security-architecture-20110325/
Security
Ciphering Prevent unauthorized user from seeing the content of
communication For control plane (RRC) data and user plane data PDCP Control PDUs (ROHC feedback and PDCP status reports)
are not ciphered
Integrity protection Used to detect whether a text is tampered during delivery Control plane (RRC) data For RN, User plane data 32-bit Message Authentication Code for Integrity (MAC-I)
34
PDCP PDU format
PDCP Data PDU User plane PDCP Data PDU Long PDCP SN (12bits) (DRBs mapped on RLC AM or UM) Short PDCP SN (7bits) (DRBs mapped on RLC UM) Integrity protection for RN user plane (DRBs mapped on RLC AM or
RLC UM) Extended PDCP SN (15 bits) (DRBs mapped on RLC AM)
Control plane PDCP Data PDU For control plane SRBs
PDCP Control PDU Interspersed ROHC feedback packet DRBs mapped on RLC AM or RLC UM
Status report DRBs mapped on RLC AM
35
D/C SN or Type MAC-IData(DRB) O SN (7,12, 15 bits) Δ
Data(SRB) X SN (5 bits) O
ROHC feedback O Type X
StatusReport O Type X
* 3GPP TS 36.323 v11.2.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Packet Data Convergence Protocol (PDCP) specification”(Release 11), April, 2013
PDCP PDU format
PDCP Data PDU
36
<User plane PDCP Data PDU with long PDCP SN (12 bits)>
<User plane PDCP Data PDU with short PDCP SN (7 bits)>
<User plane PDCP Data PDU with extended PDCP SN (15 bits)>
<RN user plane PDCP Data PDU with integrity protection><Control plane PDCP Data PDU for SRBs>
* 3GPP TS 36.323 v11.2.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Packet Data Convergence Protocol (PDCP) specification”(Release 11), April, 2013
PDCP PDU format
PDCP Control PDU
37
* 3GPP TS 36.323 v11.2.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Packet Data Convergence Protocol (PDCP) specification”(Release 11), April, 2013
<PDCP Control PDU for interspersed ROHC feedback packet>
<PDCP Control PDU for PDCP status report using a 12 bit SN>
<PDCP Control PDU for PDCP status report using a 15 bit SN>• FMS: PDCP SN of the first missing PDCP SDU
User Plane ProtocolPacket Data Convergence ProtocolRadio Link ControlMedium Access Control
38
RLC Overview
Radio Link Control(RLC) Located between RRC/PDCP and MAC Error correction through ARQ Segmentation/Concatenation/Reassembly of RLC SDUs 3 transfer modes TM (Transfer Mode)
• Only used for RRC messages which do not need RLC configuration• through BCCH, DL/UL CCCH and PCCH
UM (Unacknowledged Mode)• Utilized by delay-sensitive and error-tolerant real-time applications• through DL/UL DTCH, MCCH or MTCH
AM (Acknowledged Mode)• Utilized by error-sensitive and delay-tolerant non-real-time applications• through DL/UL DCCH or DL/UL DTCH
39
SDU: Service Data Unit BCCH: Broadcast Control Channel CCCH: Common Control ChannelPCCH: Paging Control Channel DTCH: Dedicated Traffic Channel MCCH: Multicast Control ChannelMTCH: Multicast Traffic Channel DCCH: Dedicated Control Channel
TM RLC entity
Features No segmentation/ No concatenation No RLC headers Deliver TMD PDUs Only for RRC messages which do not need RLC configuration
SI messages Paging messages RRC messages which are sent when no SRBs other than SRB0
40
< Model of TM RLC entity >BCCH : Broadcast Control Channel PCCH : Paging Control Channel SRB: Signaling Radio BearerCCCH : Common Control Channel SI: System Information TMD: Transparent Mode Data
UM RLC entity
Features Segment or concatenate RLC SDUs Add or remove RLC headers Reorder received RLC PDUs Reassembly of RLC SDUs Used by delay-sensitive and error-tolerant real-time applications VoIP, MBMS
41DTCH : Dedicated Traffic Channel MCCH : Multicast Control Channel SDU: Service Data UnitMTCH : Multicast Traffic Channel MBMS: Multimedia Broadcast/Multicast ServiceUMD: Unacknowledged Mode Data
< Model of UM RLC entity >
concatenation
UM data transfer
42< Example of PDU loss detection with HARQ reordering >
AM RLC entity
Features Similar function of UM RLC entity Support ARQ (Stop and Wait) Detect the loss of AMD PDU and request retransmission to peer Deliver AMD PDU, AMD PDU segment and STATUS PDU Used by error-sensitive and delay-tolerant non-real-time applications
Interactive/background type services: Web-browsing, file downloading
43
< Model of AM RLC entity >
ARQ: Automatic Repeat reQuest
AM data transfer
Retransmission and resegmentation Status reports from receiving side ACK/NACK
RLC data PDU is stored in retransmission buffer Resegment the original RLC PDU into smaller PDU segments
44< Example of RLC re-segmentation >
Data flow through L2 protocol stack
45A. Larmo et al., "The LTE link-layer design," Communications Magazine, IEEE , April 2009.
User Plane ProtocolPacket Data Convergence ProtocolRadio Link ControlMedium Access Control
46
MAC overview
47
Transport channel name Direction AcronymBroadcast Channel Downlink BCHDownlink Shared Channel Downlink DL-SCHPaging Channel Downlink PCHMulticast Channel Downlink MCHUplink Shared Channel Uplink UL-SCHRandom Access Channel Uplink RACH
Logical channel name Type AcronymBroadcast Control Channel Control BCCHPaging Control Channel Control PCCHCommon Control Channel Control CCCHDedicated Control Channel Control DCCHMulticast Control Channel Control MCCHDedicated Traffic Channel Traffic DTCHMulticast Traffic Channel Traffic MTCH
Functions Channel Mapping Building MAC PDU Random access Scheduling Power saving by Discontinuous
Reception(DRX) Error correction through HARQ Multiplexing / Demultiplexing Transport Format Selection Priority handling Logical Channel prioritization
• 3GPP TS 36.300 V11.5.0, "E-UTRA and E-UTRAN; Overall description; Stage 2(Release 11)", Mar, 2013.• 3GPP TS 36.300 V11.6.0, “E-UTRA and E-UTRAN; Overall description”, June, 2013.
Building MAC PDU(MAC PDU Format)
MAC PDU = MAC Header + MAC Payload MAC subheader Logical Channel ID (LCID), Length(L) field
MAC control element Used for MAC-level peer-to-peer signaling
Buffer status report / UE’s available power headroom in uplink/ DRX command, etc.
Headerless MAC PDU MAC PDU constructed without header Use it when MAC PDU is used to transport data from the PCCH or BCCH
PCCH or BCCH : one-to-one corresponding between MAC SDU and MAC PDU
48
Random Access(RA) Procedure
Purpose RA is performed when UE didn’t assigned resource for data transmission
Contention based Perform when eNB doesn’t know the presence of UE or UE have data to transmit
while UE lost timing information Examples
• Initial access from RRC_IDLE• RRC Connection Re-establishment procedure• UL data arrival during RRC_CONNECTED requiring random access procedure
» E.g. when UL synchronisation status is "non-synchronised" or there are no PUCCH resources for SR available
Non-contention based Perform when eNB know the incoming of UE or eNB have data to transmit while
UE lost timing information Examples
• Handover• For positioning purpose during RRC_CONNECTED requiring RA• DL data arrival during RRC_CONNECTED requiring random access procedure
» E.g. when UL synchronisation status is “non-synchronised”
49
Random Access Procedure- Contention based(1)
50
(0) Selection of preamble : select a preamble in preamble groups
Preambles for contention based access(2 groups, select a group by message size)
Total 64 preambles(spreading codes) in each cell
Preambles forcontention-free access
(1) Preamble Transmission on RACH• Set transmission power : according to DL estimation on RSRP• Power ramping : increase transmission power by number of retrials
(2) RA Response (PDCCH tagged with RA-RNTI + PDSCH)• Send response for a UE if single preamble is detected• This message includes UL resource grant, timing alignment
information for sending third message• Assign a temporary ID for UE(TC-RNTI)
• RSRP : Reference Signal Received Power• RA-RNTI : Random Access Radio Network Temporary Identifier
•TC-RNTI : Temporary Cell Radio Network Temporary Identifier
• No RA Response for UE Backoff Back to Selection of preamble
Random Access Procedure- Contention based(2)
51
(3) First PUSCH TX – Includes TC/C-RNTI
• Conveys actual random access procedure message• If multiple UEs selected same RACH and preamble in (1), collision occurs• No collision eNB detects one C-RNTI and get message from PUSCH
• UE considers as success, and TC-RNTI is promoted to C-RNTI• If (3) is collided No arrival of Contention Resolution for UE Backoff Back to Selection of preamble
(4) Contention Resolution on DL
Random Access Procedure- Non-Contention based
52
(0) RA Preamble Assignment
(1) RA Preamble
(2) RA Response
• eNB assigns to UE a non-contention Random Access Preamble before RA(ex> before handover)
• Transmits non-contention RA Preamble
• Conveys at least timing alignment information and initial UL grant for handover, timing alignment information for DL data arrival, RA-preamble identifier
Data Transmission after RA- Downlink Scheduling(1) Dynamic Scheduling Signal and transmit data without periodicity Signaling is required at each transmission
53
Signaling for dynamic scheduled data
PDCCH
DL-SCH
•PDCCH(Physical Downlink Control Channel)•DL-SCH(Downlink Shared Channel)
Data Transmission after RA- Downlink Scheduling(2) Semi-persistent scheduling Schedule periodical transmission Only the one signaling at first transmission is required Reduce signaling overhead
Scheduling periodicity is configured by RRC
54
PDCCH
DL-SCH
Signaling for semi-persistent data(example : period = 4)
No additional signalling for semi-persistent scheduled data
Data Transmission after RA- Uplink Scheduling Procedure eNodeB notifies the TX slot which can be used by UE for uplink transmission UE sends data through UL-SCH and activates HARQ process
HARQ mechanism : Stop-and-Wait
eNodeB signals transmission result by HARQ ACK/NACK to UE For NACK, eNodeB schedule for retransmission through PDCCH
55
Tx in 5
Txin 7
Tx in 7
ULData
PDCCH
UL-SCH
ACK NACKPHICH
1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
ULData
7
ULData
N=4 N=4UE Response eNB Response
Subframe
• Example for N=4 : UE/eNB response after 4 subframe
•PDCCH(Physical Downlink Control Channel)•UL-SCH(Uplink Shared Channel)•PHICH(Physical HARQ Indicator Channel)
Wireless Packet Scheduling Algorithm
Features of Scheduling Algorithms for Wireless Network Each user experience different transmission speed Channel environment differ by randomly through time Bursty error occurs User’s channel capacity changes by fading Require to estimate channel environment
56
• Additional Slides
Signaling for Resource Allocation
For resource allocation, eNodeB requires… Channel Quality Information(frequency specific) Traffic information(volume and priority, queue
status
Signaling tradeoff Data rate ↔ Overhead
CQI measurement DL : through the feedback of CQIs by UEs UL : by Sounding Reference Signals(SRS) transmitted by
UE to estimate ch. quality Frequency of the CQI reports is configurable
Reduce overhead ↔ Accuracy
Information about queue status DL : directly available at eNB UL : specific reporting mechanism
57
• Additional Slides
Scheduling Algorithms
Opportunistic algorithm / High Rate User First (HRUF) Simplest algorithm considering wireless channel Optimizing the total throughput Assign resources to user with best CQI
Fairness problem occurs If the an user with best channel continuously generates traffic, then other
users cannot be assigned wireless resource Other users cannot transmit their traffic Fairness and QoS are not
assured
58
max ( )i t
( )i t : Maximum transmission rate of user i
• Additional Slides
Scheduling Algorithms
Fair algorithmsMinimize UE latency Ex. Min-Max : Maximizes the minimum allocated rate
Total Throughput reduced
59
max min{ ( )}iit
• Additional Slides
Scheduling Algorithms
Proportional Fair Share Scheduling (PFSS) AlgorithmMaximize Throughput with some degree of fairness Algorithm Basically, schedule UE when its instantaneous channel quality is
high relative to its own average channel Reduce priority of UE by volume of received traffic increase
fairness
60
( )max
ˆ ( )i
i
tt
1 ( -1)( ) 1- ( -1)e e
served rate in slot tt tT T
Te : Estimation interval
m : resource block
f : subframe
2( ) log 1 ( , )i kt SNR m f
Large Te tends to maximize the total average throughputSmall Te tends to maximize fairness
• Additional Slides
Retransmission – HARQ (1/5)
Downlink : Asynchronous adaptive HARQ Asynchronous Retransmission with additional explicit signaling to indicate the HARQ
process number to the receiver
Adaptive HARQ Modulation and coding scheme(MCS), resource allocation can be
changed Non-adaptive HARQ : retransmit with previous MCS and resource
61
Retransmission – HARQ (2/5)
Uplink : Synchronous Non-adaptive/adaptive HARQ Uplink : Synchronous HARQ Synchronous
• Retransmission occur at predefined times relative to the initial transmission to reduce control signaling
62
Grant
Data
PDCCH
UL-SCH
Grant
New/ReTxData
PHICH ACK /NACK
HARQfeedback seen
by the UE
PDCCHseen by the UE
UE behaviour
ACK or NACK
NewTransmission
New transmission accordingto PDCCH
ACKor NACK
Retrans-mission
Retransmission according toPDCCH(adaptive retransmission)
ACK NoneNo (re)transmissionPDCCH is required to resumeRetransmissions
NACK None Non-adaptive retransmission
Power Saving/Fast Wake-up –Discontinuous Reception(DRX)
63
Power saving in UMTS Through the state change from CELL_DCH to IDLE_MODE Fast recovering to CELL_DCH takes undesired delay
•DCH (Dedicated Channel)•FACH (Forward access channel)•PCH (Cell Paging channel)•URA_PCH (URA Paging channel).
Power Saving/Fast Wake-up –Discontinuous Reception(DRX)
64
RRC_CONNECTED
RRC_IDLE
• DRX UE only listens at certain Intervals• DRX reduced battery consumption• DRX resume transfer even quicker• DRX reduced signaling
Power Saving in LTE/LTE-Advanced : Discontinuous Reception(DRX) Power saving with maintaining connected states When need power saving Change to DRX mode while maintain RRC_CONNECTED state UE can fast wake-up, because it maintain connectivity with eNodeB
Power Saving/Fast Wake-up –Discontinuous Reception (DRX) UE does not monitor the downlink channels during
such DRX period HARQ Round Trip Time (RTT) Short cycle, Long cycle Wake-up and check downlink during “on duration” only By two timer, control wake-up interval(=short DRX cycle and long
DRX cycle)
65
①
③
ActivateInactivity timer
ActivateShort DRX Cycle Timer
④
② ⑤
⑥ enter short DRX mode enter long DRX mode
Control Plane ProtocolC-Plane OverviewMobility ControlRadio Resource ManagementSummary of C-Plane: Initial Attach Procedure
66
Control Plane Protocol Overview
Non-access stratum PLMN selection Tracking area update Paging Authentication EPS bearer establishment,
modification and release
Access stratum control plane radio-specific functionalities The AS interacts
with the NAS (upper layers)
67RRC: Radio Resource Control PDCP: Packet Data Convergence ProtocolRLC: Radio Link Control PLMN: Public Land Mobile Network EPS: Evolved Packet System
eNB
PHY
UE
PHY
MAC
RLC
MAC
MME
RLC
NAS NAS
RRC RRC
PDCP PDCP
PHY
MAC
IP
S1-AP
SCTP
PHY
MAC
IP
S1-AP
SCTP
LTE-Uu(radio interface)
S1-MME(logical interface)
Control Plane Protocol Overview: NAS Overview Highest stratum of c-plane (UE <-> MME) S1-MME (eNB – MME)
Main functions EPS mobility management UE mobility
EPS session management IP connectivity between the UE and a P-GW
Security integrity protection and ciphering of NAS signaling messages.
68 3GPP TS 24.301 V10.7.0 “UMTS; LTE; NAS; EPS; Stage 3”, July, 2012 3GPP TS 24.401 V8.9.0 “ LTE; GPRS enhancements for E-UTRAN access”, March, 2010
Control Plane Protocol Overview: RRC Overview AS of c-plane (UE <-> eNB) LTE-Uu interface
Main functions Broadcast SI related to NAS and AS Paging Establishment of an RRC connection (UE<->E-UTRAN) Security functions (key management) Establishment of p-to-p Radio BearersMobility functions QoS management functions UE measurement reporting NAS direct message transfer (NAS<->UE)
69 3GPP, "TS 36.331 V10.5.0 Radio Resource Control (RRC) Protocol specification (Release 10)," ed, 2012.
NAS/RRC State
Protocol State Description
NAS(UE,MME)
EMM-Deregistered • UE is detached• No EMM context has been established in UE and MME.
EMM-Registered • UE has been attached• IP has been assigned• An EMM Context has been established • A default EPS Bearer has been activated• The MME knows the location of the UE(TA).
ECM-Idle • No NAS signaling connection (ECM connection)• No UE context held in E-UTRAN(eNB)• The MME knows the location of the UE(TA)
ECM-Connected • NAS signaling connection (ECM connection; a RRC connection & a S1 signaling connection)
• The MME knows the location of the UE(cell)
RRC(UE,eNB)
RRC-Idle • RRC connection has not been established.RRC-Connected • RRC connection has been established.
70TA: Tracking Area EMM: EPS Mobility Management ECM: EPS Connection ManagementMME: Mobility Management Entity1. Netmanias, “EMM and ECM States,” http://www.netmanias.com, 2013.
NAS/RRC State
71
When UE is switched on for the first time after subscription
When UE is switched on after a long time after the power has been turned off
There exists no UE context in the UE and MME.
NAS/RRC State
72
When UE is switched on within a certain period of time after the power has been turned off
When ECM connection is released during communication due to radio link failure
Some UE context can still be stored in the UE and MME (e.g., to avoid running an AKA procedure during every attach procedure).
NAS/RRC State
73
When UE is attached to the network (MME) and using services
The mobility of UE is handled by handover
NAS/RRC State
74
NAS/RRC State
75
When UE is attached to the network (MME) and not using any service
NAS/RRC State
76
Control Plane Protocol Overview: RRC States
RRC_IDLE UE known in EPC and has IP
address UE location known on Tracking
Area level Paging in TA controlled by EPC UE-based cell-selection and TA
update
RRC_CONNECTED UE known in EPC and E-
UTRAN/eNB UE location known on cell level Unicast data transfer is possible eNB-based mobility DRX supported for power
saving
77
2.
3.
5.HO
Control Plane Protocol Overview: UE Operation in RRC States
RRC_IDLEMonitors a paging channel incoming calls system information change ETWS, CMAS
measurement cell (re-)selection Acquire system information
(MIB, SIBs)
RRC_CONNECTEDMonitors a Paging channel
and/or SIB1 detect system information change
Monitor control channelsassociated and data channel
Provide channel quality and feedback information
measurement and reportingAcquire system information
78DRX: Discontinuous Reception ETWS: Earthquake and Tsunami Warning SystemCMAS: Commercial Mobile Alert Service
Control Plane Protocol Overview: UE Camping Procedure
79 Bong Youl (Vrian) Cho, “LTE RRC/RRM”, TTA LTE/MIMO Standards/Technology Trainning, May 2012
AS
PHY
RRC
NAS
(2) TriggerSystemAcquisition
(4) ScheduleBroadcast ControlChannel read
(6) Process SIB1Check PLMNIs Cell reserved?Is CSG Id valid?Cell belong to Forbidden TA?Cell barred?If fail, go back to (3)If ok, go to (7)
(8) All SIBsobtained
(10) Service Obtained(Camped)
(1) PLMN selectionRead USIMRead stored info on MESelect Band, PLMN, etc
(3) AcquisitionScan Band/Freq
(5) Read MIB/SIB1Using SI-RNTI (7) SIB2 and Other SIBs
(9) Cell isSelected and UE camps
RRC Services
Services provided to upper layers Broadcast of common control information Notification of UEs in RRC_IDLE receiving call, ETWS, CMAS
Transfer of dedicated control information information for one specific UE
Services expected from lower layers PDCP Integrity protection and ciphering
RLC Reliable and in-sequence transfer of information
• without introducing duplicates• with support for segmentation and concatenation
80ETWS: Earthquake and Tsunami Warning System CMAS: Commercial Mobile Alert Service
RRC Functions
81
Broadcast of system information
NAS common information For UEs in RRC_IDLE
• Cell (re-)selection parameters• Neighboring cell information
For UEs in RRC_CONNECTED• Common channel configuration information
RRC connection control
Paging Establishment/modification/release of RRC connection or DRBs Initial security activation RRC connection mobility Radio configuration control (ARQ, HARQ, DRX) QoS control Recovery from radio link failure
Inter-RAT mobility Security activation Transfer of RRC context information
Measurement configuration control and reporting
Establishment/modification/release of measurements Setup and release of measurement gaps Measurement reporting
Transfer of information Dedicated NAS information Non-3GPP dedicated information UE radio access capability information
Others Generic protocol error handling Support of self-configuration and self-optimization
Connection Control
Security activation Ciphering of both control plane RRC data (SRBs 1 and 2) and
user plane data (all DRBs) Integrity protection which is used for control plane data only
Connection establishment, modification and release DRB establishment, modification and release
82SRB: Signaling Radio Bearers DRB: Date Radio Bearers
Connection Establishment and Release
83
Data
DRB Establishment: Signaling Radio Bearers SRB: radio bearers that are used only for the
transmission of RRC and NAS messages SRB0 For RRC messages Using the CCCH logical channel
SRB1 For RRC messages (which may include a piggybacked NAS message) For NAS messages prior to establishment of SRB2 All using DCCH logical channel
SRB2 For NAS messages Using DCCH logical channel Lower-priority than SRB1 Always configured by E-UTRAN after security activation
84CCCH: Common Control Channel DCCH: Dedicated Control Channel
DRB Establishment : Signaling Radio Bearers
85
An EPS bearer is mapped (1-to-1) to a DRB A DRB is mapped (1-to-1) to a DTCH logical channel All logical channels are mapped (n-to-1) to the DL-SCH
or UL-SCH DL-SCH or UL-SCH are mapped (1-to-1) to the
corresponding PDSCH or PUSCH
Control Plane ProtocolC-Plane OverviewMobility ControlRadio Resource ManagementSummary of C-Plane: Initial Attach Procedure
86
Mobility Control
Criteria for cell selection or reselection Radio link quality: primary criterion UE capability Subscriber type Cell type
E-UTRAN provides a list of neighboring frequencies and cells; white-list or black-list
87
Mobility in RRC_IDLE: PLMN and Cell Selection PLMN selection The NAS handles PLMN selection based on a list of available PLMNs
provided by the AS
Cell selection (EMM-DEREGISTERED) The UE searching for the strongest cell on all supported carrier
frequencies of each supported RAT Using NAS’s support and stored information from a previous access Requirement: not take too long
Cell reselection (EMM-REGISTERED) Move the UE to the best cell of the selected PLMN
88
Mobility in RRC_IDLE: Cell Reselection
89
RRC_IDLE Mobility
Measurement and evaluation of serving cell
Measurement of neighbour cells
Evaluation of neighbour cells for cell reselection
Acquisition of the system information of the target cell
Cell reselection to the target cell
Mobility in RRC_IDLE: Cell Selection Criteria
90
Cell selection: received level & qualitySrxlev &Squal
Srxlev rxlevmeas rxlevmin rxlevminoffsetSqual qualmeas qualmin qualminoffset
rxlevmeas: Measured cell RX level value (RSRP)
qualmeas: Measured cell quality value (RSRQ)
rxlevmin: Minimum required RX level in the cell (dBm), in SIB1
qualmin: Minimum required quality level in the cell (dB), in SIB1
rxlevminoffset, qualminoffset: offsets which may be configured to
prevent ping-pong between PLMNs, in SIB1
Mobility in RRC_CONNECTED
91
Mobility in RRC_CONNECTED: Handover
UE
Measurement Report
RRCConnectionReconfiguration
Handover Preparation
Source eNB Target eNB
Random access procedure
RRCConnectionReconfigurationComplete
UE RRC context information(UE capabilities, current AS-
configuration, UE-specific RRM information
Handover command
information for random access(mobility control, radio resource configuration), dedicated radio resource security configuration, C-RNTI
92
Mobility in RRC_CONNECTED: Handover Handover from Macro cell to macro cell HO triggering condition UE satisfies A3 condition during TTT
-> HO request to S-eNB -> HO execution
93
• A3 satisfaction
• H/O completion
• HO execution
TTT HO delay
Hyst + offset
Mobility in RRC_CONNECTED : Seamless Handover Seamless handover OBJECTIVE : Interruption Time Minimization Used for all RBs carrying control plane data and user plane data
mapped on RLC UM Loss tolerant and delay sensitive
eNB forwards only non-transmitted SDUs via X2 to target eNB If transmission was started but has not been successfully
received packets are lostMinimum complexity because context is not transferred
between eNB via X2 ROHC, COUNTS context is reset
94 3GPP TS 36.323, “E-UTRA; PDCP specification.”
Mobility in RRC_CONNECTED : Seamless Handover Seamless handover in the downlink
95
SDUs are transmitted to eNBin sequence
손실된패킷은재전송되지않음
전송하지못한패킷은 X2로전달
Reordering은 UE가수행
3GPP TS 36.323, “E-UTRA; PDCP specification.”
Mobility in RRC_CONNECTED : Lossless Handover Lossless handover OBJECTIVE : In-Sequence Delivery without Losses Possible because PDCP adds a sequence number to packets Applied for radio bearers that are mapped on RLC-AM Delay-tolerant and loss-sensitive
Un-acknowledged packets are forwarded via X2 an retransmitted they may be received twice
ROHC context is reset
96 3GPP TS 36.323, “E-UTRA; PDCP specification.”
Mobility in RRC_CONNECTED : Lossless Handover Lossless handover in the uplink
97
SDUs are delivered to the GW in sequence
Serving eNB transfers via X2, out-of-sequence SDUs
STATUS TRANSFER contains Sequence and Hyper Frame Numbers
Unacknowledged SDUs are retransmitted duplicity of P4
3GPP TS 36.323, “E-UTRA; PDCP specification.”
Mobility in RRC_CONNECTED : Lossless Handover Lossless handover in the downlink
98
SGW transmits End Marker to serving eNB
Target eNB knows when it can start to transmit SDUs from SGW
SDUs are delivered to the UE in sequence
3GPP TS 36.323, “E-UTRA; PDCP specification.”
Mobility in RRC_CONNECTED: Detailed Handover Procedure (1/3)
99
Adm
issio
n Co
ntro
l
S1-Based handover
Mobility in RRC_CONNECTED: Detailed Handover Procedure (2/3)
100
Mobility in RRC_CONNECTED: Detailed Handover Procedure (3/3)
101
Measurements
Measurement Configuration: RRCConnectionReconfiguration messageMeasurement objects: carrier frequency or list of cells Reporting configurations: RSRP/RSRQ, number of cellsMeasurement identities Quantity configurations: filteringMeasurement gaps: time periods
UE may measure and report Serving cell Listed cells Detected cells on a listed frequency
102RSRP: Reference Signal Received Power RSRQ: Reference Signal Received Quality
Measurements: Measurement report triggering
103
Event Condition
A1 Serving becomes better than threshold:
A2 Serving becomes worse than threshold:
A3Neighbor becomes offset better than Pcell:
A4 Neighbor becomes better than threshold:
A5PCell becomes worse than threshold1 and neighbor becomes better than threshold2:
1 & 2
A6(Rel-10)
Neighbour becomes offset better than SCell:
B1 Inter RAT neighbor becomes better than threshold:
B2PCell becomes worse than threshold1 and inter RAT neighbor becomes better than threshold2: 1 & 2
Mserving/Mn/Mp/Ms: measurement result of serving cell/neighbor cell/Pcell/SCell Of/Oc: frequency/cell specific offsetPCell: Primary (serving) Cell SCell: Secondary (serving) Cell <- carrier aggregation 3GPP, "TS 36.331 V10.5.0 Radio Resource Control (RRC) Protocol specification (Release 10)," ed, 2012.
Measurements: Reference Signal Received Power
RSRPUEs measure RSRP over
the cell-specific RSsPeriodic measurement Intra-freq.: 200ms Inter-freq.: 480ms
(proportion to the DRX cycle)
Requirements intra-frequency: 8 cells inter-frequency: 4 cells * 3
carriers = 12 cells
104
Measurements: Reference Signal Received Quality Reference Signal Received Quality (RSRQ)
RSRQ ∝
RSSI the total received power
• interference from all sources• serving and nonserving cells• adjacent channel interference and thermal noise
LTE Rel-8 RSRQ was applicable only in RRC_CONNECTED state
• Handover
LTE Rel-9 RSRQ was also introduced for RRC_IDLE
• Cell reselection
105RSSI : Received Signal Strength Indicator
Measurements: System Information Blocks
106ETWS: Earthquake and Tsunami Warning Service CMAS: Commercial Mobile Alert SystemMBMS: Multimedia Broadcast/Multicast Services
SIB Contents
MIB • parameters which are essential for a UE’s initial access to the network
SIB1 • parameters needed to determine if a cell is suitable for cell selection• information about the time-domain scheduling of the other SIBs
SIB2 • common and shared channel information
SIB3-8 • parameters used to control intra-frequency, inter-frequency and inter-RAT cell reselection
SIB9 • signal the name of a Home eNodeB (HeNBs)
SIB10-12 • ETWS notifications and CMAS warning messages
SIB13 • MBMS related control information
Measurements: RRC messages to transfer SI (example) MIB(SIB1) message is carried by PBCH(PDSCH) created every 40(80) msec broadcasted every 10(20) msec
Other SI messages are created and broadcasted dynamically on the PDSCH
107
Message Content Period ApplicabilityMIB Most essential parameter 40 ms Idle/connectedSIB1 Cell access related parameters, scheduling information 80 ms Idle/connected1st SI SIB2: Common and shared channel configuration 160 ms Idle/connected2nd SI SIB3: Common cell reselection information and intra-frequency cell
reselection parameters other than the neighbouring cell informationSIB4: Intra-frequency neighbouring cell Information
320 ms Idle only
3rd SI SIB5: Inter-frequency cell reselection information 640 ms Idle only4th SI SIB6: UTRA cell reselection information
SIB7: GERAN cell reselection information640 ms Idle only
PBCH: Physical Broadcast Channel PDSCH: Physical Downlink Shared ChannelSFN: System Frame Number
Paging
Pagingtransmit paging
information to a UE inRRC-IDLE -> RRC-CONNECTED
MME initiates pagingPhone callDL trafficSI changeETWS notification
108
eNB
[NAS: Service Request][eNB UE signalling connection ID]
Random access procedure
<RRC>Paging <S1AP>Paging
<NAS>Service Request
<S1-AP>Initial UE MESSAGE
<S1-AP>Initial Context Setup Request[NAS message]
[MME UE signaling connection ID][Security Context]
[UE Capability Information][Bearer Setup:serving S-GW TEID,
QoS Profile]
<RRC>Radio Bearer Setup
<RRC>Radio Bearer Setup Complete<S1-AP>Initial Context Setup Complete
[eNB UE signalling connection ID][Bearer Setup Confirm:eNB TEID]
P-RNTI check
Monitor PDCCH at certain UE-specific subframes
MMEUE
TA: Tracking Area PDCCH: Physical Downlink Control Channel RNTI: Radio Network Temporary IdentifierP-RNTI: Paging RNTI ETWS: Earthquake and Tsunami Warning service
Send to all eNBs in a TA
, S-TMSI
Paging: Tracking Area
TAI: Global Unique IDPLMN ID + TAC
In order to paging, MME needs TAI Ex) MME1 sends paging to
UE1 => broadcast all the eNBs in TAI1 & TAI2
TAI listUE receives TAI list when it is
connected
TAUWhen UE move out from
own TAI listPeriodic TAU
109TAI: Tracking Area Identifier TAC: Tracking Area Code TAU: Tracking Area Update
Control Plane ProtocolC-Plane OverviewMobility ControlRadio Resource ManagementSummary of C-Plane: Initial Attach Procedure
110
Radio Resource Management: RRM Functions
111
Power control Scheduling Cell search Cell reselection Handover Radio link or connection monitoring Connection establishment and re-establishment Interference management Location services Self-Optimizing network (SON)Network planning
Radio Resource Management: LTE RRM Characteristic
112MBMS: Multimedia Broadcast/Multicast Service
Characteristics DetailsInterference fluctuation • Fast time and frequency domain scheduling
Wide range of DRX • DRX: 0~2.5 sec
Different RATs • LTE, 3GPP & non-3GPP legacy RATs• Different channel structure
Various cell sizes • Macro / femto / pico• A few ‘m’ ~ tens of ‘km’
Various frame structure • FDD(synchronized or unsynchronized), TDD
Low latency requirements • Measurements & reports• HO
Power Control
LTE power control is not as critical as in WCDMA LTE uplink resources are orthogonal
-> no intra-cell interference (theory) frequency selective scheduling
Power ControlMaximize system capacityMinimize inter-cell interference
113SRSs: Sounding Reference Signals RB: Resource Block RE: Resource Element
Power Control: UL Power Control Uplink power control: PUSCH, PUCCH and the SRSs
(unit of RB) · ∆
Semi-static basic open-loop operating point : cell specific power level : factor to trade off the fairness of uplink scheduling against total
cell capacity• PUCCH: always 1 -> maximize fairness for cell edge UE
: downlink pathloss estimate calculated in the UE
dynamic offset updated from subframe to subframe ∆ : MCS dependent power offset : TPC command related power
• TPC command: relative power offset comparing to its previous Tx power, or absolute power
114
SRSs: Sounding Reference Signals RB: Resource Block RE: Resource ElementTPC: Transmitter Power Control 3GPP, "TS 36.213 v10.6.0 LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures
(Release 10)," July 2012.
Downlink power allocation (unit of RE) Cell specific RS EPRE (Energy per RE)
: semi-static (eNB signals UE)
10log : 0dB for all
transmission modes except multi-user MIMO
: UE specific parameter from higher layer
: 2 (transmit diversity with 4 antenna ports) or 1 (otherwise)
: cell specific parameter
from higher layer
PDSCH power to RS, where NO RSs are present, is UE specific and signaled by higher layer as .(ex. -4.77dB)
Cell-specific RS power, signaled in SIB2 (-60~50dBm)
Power Control: DL Power Allocation
115RE: Resource Element 3GPP, "TS 36.213 v10.6.0 LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures
(Release 10)," July 2012.
EPRE
Subcarrier Index[f]
PDCCH power depending on /
For PDSCH power in same symbol as RS an additional cell specific offset is applied, that is signaled by higher layers as (ex. -3.98dB)
Cell Search
Cell Search UE acquires the carrier frequency, timing and cell identity of
cells
Cell search within E-UTRAN Identify one of the 504 unique Physical Cell Identities (PCIs)
RequirementsMaximum permissible cell identification delay(∝ DRX cycle)Minimum synchronization signal quality : the energy per Resource Element (RE) of the synchronization
signal : total received energy of noise and interference on the same RE
116
Case Max. Delay Min. /Intra-frequencyDRX (0~40ms) 800ms -6dB
Inter-frequencyDRX(0~160ms) 3.84s -4dB
Radio Link Failure Handling
1st phase Layer 1 monitors downlink quality and indicates problems to RRC RRC filters L1 indications and starts a timer if no recovery within 1st phase, triggers 2nd phase
Layer 2 monitors random access attempts and indicates problems to RRC RRC triggers 2nd phase
2nd phase – Radio Link Failure (RLF): Possible recovery through an RRC Connection Reestablishment
procedure reestablishment may be performed in any cell to which the UE’s context
is made available If no recovery within 2nd phase, UE goes autonomously to IDLE
117
Inter-Cell Interference
LTE is designed for frequency reuse 1 (To maximize spectrum efficiency) All the neighbor cells are using same frequency channels no cell-planning to deal with the interference issues
Shared channels RB scheduled to cell edge user can be in high interference
->low throughput / call drops
Control channels Neighbor interference -> radio link failures at cell edge.
118
Inter-Cell Interference Coordination
ICIC mitigates interference on traffic channels only Power and frequency domain to mitigate cell-edge interference from
neighbor cells
X2 interface is used to share the information between the eNBs
A.Neighbor eNBs use different sets of RBs improves cell-edge SINR decrease in total throughput
B.Center users: complete range of RBsCell-edge users: different sets of RBs
C.Scheme B + different power schemes For center/cell edge user: low/high power
119
Control Plane ProtocolC-Plane OverviewMobility ControlRadio Resource ManagementSummary of C-Plane: Initial Attach Procedure
120
Summary of Control Plane: Initial Attach Procedure
121
Summary of Initial Attach Procedure
S-GW: Serving Gateway P-GW: Packet Data Network Gateway HSS: Home Subscriber Server PCRF: Policy and Charging Rule Function SPR: Subscriber Profile Repository IMSI: International Mobile Subscriber Identity Netmanias, “EMM Procedure: 1. Initial Attach for Unknown UE (2편),” September, 2011 http://www.netmanias.com/bbs/view.php?id=techdocs&no=74
Summary of Control Plane: Acquisition of IMSI
122
Summary of Initial Attach Procedure
Netmanias, “EMM Procedure: 1. Initial Attach for Unknown UE (2편),” September, 2011
Summary of Control Plane: Acquisition of IMSI
123GUMMEI: Globally Unique MME ID ECGI: E-UTRAN Cell Global Identifier TAI:Tracking Area Identity Netmanias, “EMM Procedure: 1. Initial Attach for Unknown UE (2편),” September, 2011
Summary of Control Plane: Authentication
124
Summary of Initial Attach Procedure
Netmanias, “EMM Procedure: 1. Initial Attach for Unknown UE (2편),” September, 2011
Summary of Control Plane: Authentication
125MCC: Mobile Country Code MNC: Mobile Network CodePLMN: Public Land Mobile Network ID PLMN=MCC+MNC Netmanias, “EMM Procedure: 1. Initial Attach for Unknown UE (2편),” September, 2011
Summary of Control Plane: NAS Security Setup
126
Summary of Initial Attach Procedure
Netmanias, “EMM Procedure: 1. Initial Attach for Unknown UE (2편),” September, 2011
Summary of Control Plane: NAS Security Setup
127 Netmanias, “EMM Procedure: 1. Initial Attach for Unknown UE (2편),” September, 2011
Summary of Control Plane: Location Update
128
Summary of Initial Attach Procedure
Netmanias, “EMM Procedure: 1. Initial Attach for Unknown UE (2편),” September, 2011
Summary of Control Plane: Location Update
129APN: Access Point Name QCI: QoS Class identifier ARP: Allocation and Retention Priority AMBR: Aggregated Maximum Bit Rate Netmanias, “EMM Procedure: 1. Initial Attach for Unknown UE (2편),” September, 2011
Summary of Control Plane: EPS Session Establishment
130
Summary of Initial Attach Procedure
Netmanias, “EMM Procedure: 1. Initial Attach for Unknown UE (2편),” September, 2011
Summary of Control Plane: EPS Session Establishment (1)
131TEID: Tunnel Endpoint ID Netmanias, “EMM Procedure: 1. Initial Attach for Unknown UE (2편),” September, 2011
Summary of Control Plane: EPS Session Establishment (2)
132TEID: Tunnel Endpoint ID Netmanias, “EMM Procedure: 1. Initial Attach for Unknown UE (2편),” September, 2011
Summary of Control Plane: EPS Session Establishment (3)
133 Netmanias, “EMM Procedure: 1. Initial Attach for Unknown UE (2편),” September, 2011
Summary of Control Plane: EPS Session Establishment (4)
134
Summary of Control Plane
135
13
2 4 5
67 9
8 EMM- Registered
Summary
LTE network overview• Standardization of LTE/ Features of LTE/ LTE
Network Architecture/ LTE Physical layer
User plane protocol• PDCP/ RLC/ MAC
Control plane protocol• C-Plane Overview/ Mobility Control/ Radio Resource
Management/ Initial Attach Procedure
136
Thank you !
Q & A137
References 3GPP TS 36.300 V11.6.0 "E-UTRA and E-UTRAN; Overall description", June, 2013 3GPP TS 23.203 v12.1.0, "Policy and charging control architecture," Jun. 2013. 3GPP TS 36.323 v11.2.0, "Evolved Universal Terrestrial Radio Access (E-UTRA); Packet Data Convergence Protocol (PDCP)
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