1-Network Architecture - Slides

LTE Network Architecture

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LTE Network Architecture  Basic LTE Network Architecture Overview     

Function of the eNodeB Function of the X2 Function of the Serving Gateway Function of the PDN Gateway Some of the functions of the MME

 LTE Carriers    

RSRP, RSSI, RSRQ Frequency-division duplexing(FDD) Re-Farming Time-Division Duplexing (TDD)

2

LTE Network Architecture Evolved UTRAN (E-UTRAN)

Evolved Packet Core (EPC)

UMTS Terrestrial Radio Access Network

HSS

ALL IP NETWORK MME: Mobility Management Entity

S6a

Evolved Node B (eNB) LTE-UE

MME

X2 S1-MME

S11

Signalling

S5

S1-U

Internet/IMS

LTE-Uu S3

DATA

DATA S4

Serving Gateway

DATA

PDN Gateway

DATA

SGSN

Connection to 3G network

S3 interface connects MME directly to SGSN for signaling to support mobility across LTEand UTRAN 3

LTE Network Architecture Evolved UTRAN (E-UTRAN) Evolved Packet Core (EPC) EPS (Evolved Packet switched System) UMTS Terrestrial Radio HSS EPS Bearer Access Network ALL IP NETWORK 'EPS Bearer' as a pipe line through which data traffic flows PDN Serving MME: Mobility Management Entity Gateway S6a Gateway

Radio Bearer Evolved Node B (eNB) LTE-UE Signalling

X2- Bearer S1 S1-MME

MME

S5 - Bearer S11 S5

S1-U

Internet/IMS

LTE-Uu S3

DATA

DATA S4

Serving Gateway

DATA

PDN Gateway

DATA

SGSN

Connection to 3G network

S3 interface connects MME directly to SGSN for signaling to support mobility across LTEand UTRAN 4

Evolved Node B (eNB) Evolved UTRAN (E-UTRAN) S1-MME

MME

Signalling

HANDOVE R

Source eNodeB

Target eNodeB

X2

Evolved Node B (eNB)

Admission control Load Control Packet Scheduling

Evolved Node B (eNB) DATA

S1-U Evolved Node B (eNB)

In LTE, eNBs (evolved NodeB) manage radio resource and mobility: • Admission control • Load Control • Packet Scheduling

Admission control Load Control Packet Scheduling

5

eNodeB –Control Plane control plane RRC CONNECTION RECONFIGURATION message is the command to modify an RRC connection. · To establish/modify/release Radio Bearers · To perform Handover · To setup/modify/release Measurements

Evolved Node B (eNB)

Signalling

RRC Connection Reconfiguration

RRC

PDCP RLC MAC

RRC: Measurement Report

Other examples – RRCConnectionReject – RRCConnectionRelease – RRCConnectionRequest – RRCConnectionSetup

PDCP

RLC MAC L1

L1 eNode B

RRC

AirInterface

eNode B 6

UDP (User Datagram Protocol)

RLC UDP (User Datagram Protocol) UDP (User Datagram Protocol) Application

PACKET SWITCH

TCP/UDP

PACKET SWITCH

IP Relay

RLC MAC L1

UE

AirInterface

GTP-U

RLC

UDP

MAC

IP

L1

L1/L2

eNode B

S1

IP

IP

Relay

PDCP

TCP/UDP

Relay

IP

PDCP

Application

PACKET SWITCH

GTP-U

GTP-U

GTP-U

UDP

UDP

UDP

IP

IP

L1/L2

L1/L2

Serving Gateway

S5/S8

IP

L1/L2

L1/L2 SGi

L1/L2 PDN Gateway

Server

7

eNodeB interfaces

LTE-Uu Air-Interface

Evolved Node B (eNB)

Radio Conditions SINR

MME: Mobility Management Entity

S1-MME

Control Plane

dynamic adaptive modulation

64QAM

16QAM Data

QPSK

scheduler

Data

Serving Gateway

Data

User Plane

S1-U I need to give QoS

8

Serving Gateway MME: Mobility Management Entity

S1-U

S11

DATA

DATA

S5

Serving Gateway EPS Bearer Radio Bearer

S1 - Bearer

S5 - Bearer

9

Serving Gateway MME: Mobility Management Entity

S1-U

S11

DATA

DATA

S5

3G

Serving Gateway SGSN

RNC 10

MME control plane

Home Subscriber Server

Evolved Node B (eNB)

HSS

MME: Mobility Management Entity IMSI

Tracking Area

S-TMSI

S1-MME

Signalling

tracking area update Attach : IMSI OR GUTI

NAS

NAS Paging

RRC

RRC Signalling

PDCP

International mobile Subscriber Identity or IMSI

PDCP

RLC

MAC

RRC

RLC AirInterface

The TMSI It is allocated to a particular subscriber's (U)SIM card) during initial attach.

MAC

L1

L1

UE

eNode B

11

Paging with s-TMSI The UE needs to know the MME id For routing NAS message to the appropriate MME

12

Attach Accept

S1-MME

MME: Mobility Management Entity Group 1 Code 1

Attach Accept

Periodic TAU: Upon the expiry of timer T3412

Globally Unique Temporary ID

13

Globally Unique Temporary ID

Tracking Area

Tracking Area

MME Group

The TRACKING AREA UPDATING (TAU) procedure is always initiated by the UE.

MME Code

MME Code

NAS: Tracking Area update

Normal TAU Combined TAU Periodic TAU: Upon the expiry of timer T3412 MME load balancing: When the UE receives RRC CONNECTION RELEASE message with cause „load balancing TAU required', it initiates TAU procedure

14

User plane - Bearers

LTE-Uu

S1-U

Serving Gateway

S5

PGateway

PDN

End to End Bearer

External Bearer

EPS Bearer

Radio Bearer

S1 - Bearer

S5 - Bearer

E-RAB

Evolved Packet switched System

15

Bearers LTE-Uu

S1-U

Packet Scheduling

Serving Gateway

S5

PDN

PDN

Default Bearer

Default EPS Bearer : Be established during Attach Process Allocate IP address to UE Does not have specifc QoS (only Nominal QoS is applied). Packet Scheduling

PGateway

Dedicated Bearer Does not allocate any additional IP address to UE Is linked to a specified default EPS bearer

Dedicated Bearer

Dedicated Bearer Normally be established during the call setup after idle mode. Have a specific (usually guaranteed) QoS

Packet Scheduling

Packet Scheduling

Default Bearer

Default bearers are created on a per PDN basis.

Dedicated Bearer

Each default bearer comes with an IP address

16

Packet Data Network Gateway LTE-Uu

S1-U

Serving Gateway

S5

PGateway

PDN

The PDN GW provides connectivity to the UE to external packet data networks by being the point of exit and entry of traffic for the UE. A UE may have simultaneous connectivity with more than one PDN GW for accessing multiple PDNs.

The PDN GW performs policy enforcement, packet filtering for each user, charging support, lawful Interception

17

Traffic Flow Templates (TFT) Each EPS bearer is associated with a traffic flow template (TFT). This comprises a set of packet filters, one for each of the packet flows that make up the bearer. The PDN GW performs policy enforcement, packet filtering for each user, charging support, lawful Interception

Packet filters Packet filters

EPS Bearer ID Data Bearer 8

GTP-U Tunnel 8

GTP-U Tunnel 8

Packet filters

Data Bearer 8

GTP-U Tunnel 8

GTP-U Tunnel 8

Packet filters

• Source address (with subnet mask) • IP protocol number (TCP, UDP) • Destination port • Source port range • Type of Service (TOS) (IPv4) • Flow-Label (IPv6 only)

Dedicated EPS bearer

PGateway 18

Traffic Flow Templates (TFT) 0

4

8

VERS

HLEN

16 TOS

24

31

Total Length

Identification Time To Live

19

Flags

Protocol

Fragment Offset Header Checksum

Source IP Address Destination IP Address IP Options (If any)

Padding

DATA ...

Packet filters Packet filters

EPS Bearer ID Data Bearer 8

GTP-U Tunnel 8

GTP-U Tunnel 8

Packet filters

Data Bearer 8

GTP-U Tunnel 8

GTP-U Tunnel 8

Packet filters

• Source address (with subnet mask) • IP protocol number (TCP, UDP) • Destination port • Source port range • Type of Service (TOS) (IPv4) • Flow-Label (IPv6 only)

Dedicated EPS bearer

PGateway 19

Bearers-QoS Class Identifier LTE-Uu

S1-U

Serving Gateway

Packet Scheduling

Default Bearer

Packet Scheduling

Dedicated Bearer

S5

PGateway

PDN

A packet with higher priority can be expected to be scheduled before a packet with lower priority.

20

Summary so far Can you answer this Question What is meant by an EPS bearer? “virtual” connection between two endpoints (e.g. a UE and a PDN-GW) A QoS Class Index (QCI) that describes the type of service that makes use of the virtual connection (e.g. conversational voice, streaming video, signaling, best effort, etc). Inside each EPS node, the QCI points to more detailed pre-configured QoS attributes (e.g. maximum delay, residual error rate, etc). These QoS attributes characterize the type of transport service provided by the virtual connection Flow specification that describes the guaranteed and maximum bitrate (GBR, MBR) of the aggregate traffic flow

21

Summary so far Can you answer this Question What is meant by an Traffic Flow Template? A filter specification that describes the traffic flows (in terms of IP addresses, protocols, port numbers, etc) for which the transport service is provided between the two endpoints

filter Serving Gateway

P- Gateway

filter

22

LTE Carriers

Privileged and confidential. The information contained in this material is privileged and confidential, and is intended only for the use of the individual to whom it is addressed and others who have been specifically authorized to receive it. If you are not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this material is strictly prohibited. If you have received this material in error, please destroy it immediately.

What are the Reference Signals-Used for ? SINR ave = Physical Cell Identity

Reference Signals-Used for cell search, channel estimation and neighbour cell monitoring (handover & Cell selection)

S I+N I = Iown + Iother

Path Loss DLRS SINR Path Loss Traffic SINR

Physical Resource block

QPSK, 16QAM, 64QAM 24

Physical Cell Identity (PCI) =20

ref signals

Physical Cell Identity (PCI) =55

64 bit QAM SIB‟s/RRC messages

SINR-4dBm

Down Link Bearers

QPSK

I can now send a measurement report

This is a shared channel (PDSCH )

Power 41.46

SINR+19dB m

I am idle I need to do cell selection Lets look at Ref Signals

25

UE measurements Cell selection/reselection

In handover, it has to measure the signal strength/quality of the neighbour cells & send a report to the network. Event A5. Serving cell becomes worse than an absolute threshold and the neighbouring cells is better than another absolute threshold

In LTE network, a UE measures two parameters on reference signal: • •

RSRP (Reference Signal Received Power)

LTE

3G

In cellular networks, when a mobile moves from cell to cell and performs cell selection/reselection

IDLE

LTE

SIBParameters for cell selection

GSM

UE makes the decision based on Handover RRC CONNECTION RECONFIGURATION

Serving cell MME

Measurement Report A5

neighbouring cell

RSRQ (Reference Signal Received Quality) 26

UE measurements In LTE network, a UE measures two parameters on reference signal: •

RSRP (Reference Signal Received Power)

•

RSRQ (Reference Signal Received Quality)

•Qrxlevmin used for cell selection in 3GPP release 8 •Minimum required RX level in the cell (dBm)

Cell selection/reselection IDLE SIB1/3 Parameters for cell selection

•Qrxlevmin and Qqualmin used for cell selection from 3GPP release 9 •Minimum required quality level in the cell (dB)

Intra Freq Cell Reselection 27

Reference Signal Receive Power

12 sub-carriers

Antenna 1 Without MIMO

RSRP (Reference Signal Receive Power) is the average power of Resource Elements (RE) that carry cell specific Reference Signals (RS) over the entire bandwidth, so RSRP is only measured in the symbols carrying RS

1 ms

Reference Signals occupy 8 out of 168 symbols(14x12) 28

Reference Signal Receive Power RSRP (Reference Signal Receive Power) is the average power of Resource Elements (RE) that carry cell specific Reference Signals (RS) over the entire bandwidth, so RSRP is only measured in the symbols carrying RS Reference signals similar to CPICH in WCDMA

Reference signals reduce the maximum achievable user plane bit rate by occupying a subset of the resource block symbol locations

12 sub-carriers

Used for cell search, channel estimation and neighbour cell monitoring

Without MIMO

Reference signals are distributed in both the time and frequency domains

Antenna 1

1 ms Reference Signals occupy 8 out of 168 symbols

RSRP measures signal power from a specific sector while excluding noise and interference from other sectors 29

Sub channel RSRP (Reference Signal Receive Power) is the average power of Resource Elements (RE) that carry cell specific Reference Signals (RS) over the entire bandwidth, so RSRP is only measured in the symbols carrying Reference Signals

30

Reference Signal Received Power (RSRP)

31

Received Signal Strength Indicator RSSI is effectively a measurement of all of the power contained in the applicable spectrum (1.4, 3, 5, 10, 15 or 20MHz). This could be signals, control channels, data channels, adjacent cell power, background noise, everything. RSSI varies with LTE downlink bandwidth

Point of interest 32

Reference Signal Receive Quality RSRP provides information about signal strength and RSSI helps in determining interference and noise information. This is the reason, RSRQ (Reference Signal Receive Quality) measurement and calculation is based on both RSRP and RSSI

RSRQ is defined as the ratio N×RSRP / (EUTRA carrier RSSI)

33

Reference Signal Received Quality (RSRQ)

LOADED UNLOADED RSRQ affected by cell loads.

34

Reference Signal Receive Quality Bandwidth 1.4 (MHz) # of RBs 6 Subcarrier s

72

3

5

10

15

20

15

25

50

75

100

180 300 600 900 1200

Point of interest

RSRQ = n x RSRP/RSSI RSRQ = 10 log 25 + (-102.77 –(- 82 .71) =13.97 + (-20.06) =-6.09 35

Measurement Reports: Received Signal Received Power (RSRP)  Equivalent to CPICH RSCP (absolute power measurement)  Represents the average power of a Resource Element occupied by the cell specific Reference Signal (excludes the cyclic prefix power)  Average is taken in linear units  Measured from the first antenna port by default  Can also be measured from both the first and second antenna ports  The reference point for the RSRP shall be the antenna connector of the UE  If receiver diversity is in use by the UE, the reported value shall not be lower than the corresponding RSRP of any of the individual diversity branches

36

Measurement Reports: Received Received Signal Received Quality (RSRQ)  Equivalent to CPICH Ec/Io (signal to noise measurement)  Defined as: RSRQ = n x RSRP/RSSI

• „N‟ is the number of Resource Blocks over which the RSSI is measured • RSSI is measured from OFDMA symbols which include the cell specific Reference Signals for antenna port 0 • The reference point for the RSRQ shall be the antenna connector of the UE

37

Summary so far RSRP provides information about signal strength and RSSI helps in determining interference and noise information

RSRQ (Reference Signal Receive Quality) measurement and calculation is based on both RSRP and RSSI RSRQ = n x RSRP/RSSI

What does this tell you?

RSRP level = -70 RSRQ level = -20

38

Frequency-division duplexing(FDD) Band 1 2110-2170 MHz

receiver transmitter

1920-1980 MHZ

Frequency-division duplexing (FDD) means that the transmitter and receiver operate at different carrier frequencies. E-UTRA Band

Bandwidth UL (MHz)

Bandwidth DL (MHz)

Duplex Mode

1

1920-1980

2110-2170

FDD

60Mh z

60Mh z

Bandwidth 1.4 (MHz)

3

5

10

15

20

# of RBs

6

15

25

50

75

100

Subcarriers

72

180

300

600

900

1200

FOR LTE REL‟8 39

Frequency-division duplexing(FDD) 20Mh z

receiver Filters are required

Filters are required

2110-2130 MHz

Type 1: used for the LTE FDD mode systems

transmitter 1920-1940 MHZ

Duplex is a scheme whereby transmissions may be sent in both directions simultaneously Channel separation between the transmission and reception frequencies must be sufficient to enable the receiver not to be unduly affected by the transmitter signal. Filters are required within the base station and also the handset to ensure sufficient isolation of the transmitter signal without desensitising the receiver.

E-UTRA Band

Bandwidth UL (MHz)

Bandwidth DL (MHz)

Duplex Mode

1

1920-1980

2110-2170

FDD

40

Frequency-division duplexing(FDD) 20Mh z 2110-2130 MHz

LTE Subframes then consist of two slots

1920-1940 MHZ

Channel characteristics different in both directions as a result of the use of different frequencies Requires paired spectrum with sufficient frequency separation to allow simultaneous transmission and reception Type 1: used for the LTE FDD mode systems 41

Frequency-division duplexing(FDD) E-UTRA Band

Bandwidth UL (MHz)

Bandwidth DL (MHz)

Duplex Mode

1

1920-1980

2110-2170

FDD

2

1850-1910

1930-1990

FDD

3

1710-1785

1805-1880

FDD

4

1710-1755

2110-2155

FDD

5

824-849

869-894

FDD

6

830-840

875-885

FDD

7

2500-2570

2620-2690

FDD

8

880-915

925-960

FDD

9

1749.9-1784.9

1844.9-1879.9

FDD

10

1710-1770

2110-2170

FDD

11

1427.9-1452.9

1475.9-1500.9

FDD

12

698-716

728-746

FDD

13

77-787

746-756

FDD

14

788-798

758-768

FDD

Europe: Band 7: The 2.6 GHz auctions have been running in a few countries Band 8:is currently used mostly by GSM. The band is attractive from a coverage point of view due to the lower propagation losses.

Being low frequency it's also better at penetrating walls than the 2.6GHz or 1800MHz bands, so it will provide an improved signal when indoors 42

Frequency-division duplexing(FDD) E-UTRA Band

Bandwidth UL (MHz)

Bandwidth DL (MHz)

Duplex Mode

1

1920-1980

2110-2170

FDD

2

1850-1910

1930-1990

FDD

3

1710-1785

1805-1880

FDD

4

1710-1755

2110-2155

FDD

5

824-849

869-894

FDD

6

830-840

875-885

FDD

7

2500-2570

2620-2690

FDD

8

880-915

925-960

FDD

9

1749.9-1784.9

1844.9-1879.9

FDD

10

1710-1770

2110-2170

FDD

11

1427.9-1452.9

1475.9-1500.9

FDD

12

698-716

728-746

FDD

13

77-787

746-756

FDD

14

788-798

758-768

FDD

Band 8:is currently used mostly by GSM. The band is attractive from a coverage point of view due to the lower propagation losses.Supported Channels (non-overlapping) E-UTRA Band

Downlink Bandwidth

1 2 3 4 5 6 7 8

60 60 75 45 25 10 70 35

Channel Bandwidth (MHZ) 1.4 42 53 32 17 25

3 20 23 15 8 11

5 12 12 15 9 5 2 14 7

10 6 6 7 4 2* 1* 7 3*

15 4 4* 5* 3 X 4 -

20 3 3* 3* 2 X 3* -

GSM Bandwidth Available

43

Time-Division Duplexing (TDD) TDD means the transmission and reception occur on the same frequency Same frequency

Dow n

E-UTRA Band

Special

Up

Bandwidth UL (MHz)

Up

Bandwidth DL (MHz)

Dow n

Dow n

Duplex Mode

33

1900-1920

1900-1920

TDD

34

2010-2025

2010-2025

TDD

35

1850-1910

1850-1910

TDD

36

1930-1990

1930-1990

TDD

37

1910-1930

1910-1930

TDD

38

2570-2620

2570-2620

TDD

39 40

1880-1920 2300-2400

1880-1920 2300-2400

TDD TDD

Dow n

Dow n

Dow n

TDD in unpaired spectrum, whereby the same frequency channel is used for both downlink and uplink communication

E-UTRA Band

Bandwidth UL (MHz)

Bandwidth DL (MHz)

Duplex Mode

1

1920-1980

2110-2170

FDD

2

1850-1910

1930-1990

FDD

3

1710-1785

1805-1880

FDD

4

1710-1755

2110-2155

FDD

5

824-849

869-894

FDD

6

830-840

875-885

FDD

7

2500-2570

2620-2690

FDD

8

880-915

925-960

FDD

9

1749.9-1784.9

1844.9-1879.9

FDD

10

1710-1770

2110-2170

FDD

11

1427.9-1452.9

1475.9-1500.9

FDD

12

698-716

728-746

FDD

13

77-787

746-756

FDD

14

788-798

758-768

FDD 44

Dow n

Time-Division Duplexing (TDD) While FDD transmissions require a guard band between the transmitter and receiver frequencies.

Down

E-UTRA Band

Bandwidth UL (MHz)

Bandwidth DL (MHz)

Duplex Mode

1

1920-1980

2110-2170

FDD

UP

Down

TDD schemes require a guard time or guard interval between transmission and reception. This must be sufficient to allow the signals travelling from the remote transmitter to arrive before a transmission is started and the receiver inhibited.

DELAY

Down

Large guard period will limit capacity. Down

Special

Up

Up

Down

Down

Special

Down

TDD is not normally suitable for use over long distances as the guard time increases and the channel efficiency falls.

Down

Down

Down

45

Type 2 LTE Frame Structure Frame 0

Frame 1

Down

Special

Up

Up

Up

Down

Special

Up

Up

Up

Down

Special

Up

Up

Down

Down

Special

Up

Up

Down

Down

Special

Up

Down

Down

Down

Special

Up

Down

Down

Down

Special

Up

Up

Up

Down

Down

Down

Down

Down

Down

Special

Up

Up

Down

Down

Down

Down

Down

Down

Down

Special

Up

Down

Down

Down

Down

Down

Down

Down

Down

Special

Up

Up

Up

Down

Special

Up

Up

Down

Frame 5

Frame 6

Frame 0 and frame 5 (always downlink in TDD) Frame 1 and frame 6 is always used as for synchronization in TDD Frame allocation for Uplink and Downlink is settable in TDD 46

Questions ?

47

Questions 1. What best describes RSSI? a. RSSI is the average power of Resource Elements (RE) that carry cell specific Reference Signals (RS) over the entire bandwidth, so RSSI is only measured in the symbols carrying RS b. RSSI is effectively a measurement of all of the power contained in the applicable spectrum (1.4, 3, 5, 10, 15 or 20MHz) c. RSSI helps in determining interference and noise information d. b&c e. None of the above

48

Questions 2. For a 5 MHz bandwidth. The RSSI = -80dBm and the RSRP = -100dbm. What is the RSRQ?

a. b. c. d. e. f.

-58 dB -56.03dB -60dB -30dB -46.04dB None of the above

RSRQ = 10 log 25 + (-100–(- 80 ) =13.97 + (-20) =-6.03 49

Questions 3. In the Attach Accept message. The Globally Unique Temporary ID is transmitted? TRUE FALSE 4. What best describes the Globally Unique Temporary ID. a. It contains the IMSI b. It contains the IMEI c. It contains the ISDN number d. MME code, MME group & M-TMSI

e. All of the above f. None of the Above

50

Questions 5. During which procedure the S-TMSI (SAE-Temporary Mobile Subscriber Identity) and default bearer is allocated? a. At the time of paging b. At the time of initial attach c. All of the above a. A&B a. None of the Above

51

52