Transcript
LTE Mobility
Air Interface – Rel’99 / Rel 4 CELL URA
CELLPCH
CELL DCH QoS
CELL FACH NO QoS
IDLE
Air Interface – Rel’99 / Rel 4 CELL URA
CELLPCH
CELL DCH QoS
CELL FACH NO QoS
IDLE
LTE – Always on In the early deployment phase, LTE coverage will certainly be restricted to city and hot spot areas. MORE HO’s than Rel’99 Cell DCH Connected
Connection Cell FACH Establishment/ Release
Handover
LTE Connected
Handover
GSM Connected
GPRS Packet Transfer Connection Establishment/Release
Cell URA Cell PCH
Connection Establishment/Release
Reselection IDLE
LTE _IDLE
GSM/GPRS IDLE
UE Power up
UE Power up
DL Syn and Physical Channel ID
Acquire another LTE Cell
Find MIB – MIB – System BW MCC +MNC SIB’s supported
PLMN ID matches
PCFICH ProcessingKnows the set up of PDCCH
Retrieval of SIB’s Cell Selection Parameters After Attach – Attach –Defaulf Defaulf Bearer/IP adress
Cell Barred Cell Selection Successful
Yes Pre-amble / Attach
EPS Mobility Management Evolved Packet Core (EPC)
Evolved UTRAN (E-UTRAN)
EPS Mobility Management 2 states: EMM-DEREGISTERED EMM-REGISTERED HSS
MME: Mobility Management Entity
S6a
Evolved Node B (eNB)
MME
X2 S1-MME
PCRF
S11
LTE-UE
S5
S1-U LTE-Uu
S7
Serving Gateway
Internet PDN Gateway
EPS Mobility Management 2 states • EMM-DEREGISTERED: • In this state the MME holds no valid location •
information about the UE Successful Attach and Tracking Area Update (TAU) procedures lead to transition to EMMREGISTERED
EMM-REGISTERED: •In this state the MME holds location information for the UE at least to the accuracy of a tracking area •In this state the UE performs TAU procedures, responds to paging messages and performs the service request procedure if there is uplink data to be sent
MME
MME
Tracking Area update - IDLE LTE Non Access Stratum (NAS) The LTE NAS protocol software enables communication with the MME in the LTE core network and handles functions of mobility
•Tracking Area Identity = MCC (Mobile Country Code), MNC (Mobile Network Code) and TAC (Tracking Area Code Tracking Area
Tracking Area NAS: Tracking Area update
s6a MME
Home HSS
Tracking Area update - IDLE Tracking areas are allowed to overlap: one cell can belong to multiple tracking areas TAI1
TAI1-2
TAI1
TAI1-2
TAI1 TAI2 TAI2 TAI2 TAI2 TAI2 TAI2 TAI2 TAI2 TAI2 TAI2 TAI2 TAI3 TAI3 TAI3 TAI3
NAS: Tracking Area update
MME
LTE Functional Nodes- Management Entity (MME Tracking Area Update Request S-TMSI/IMSI, PDN address allocation
Tracking Area Update Accept
MME
S1-MME (Control Plane)
Tracking Area Update Complete
NAS Protocols
S1-AP SCTP IP
eNB
L1/L2 S1-U (User Plane)
•Tracking area (TA) is similar to Location/routing area in 2G/3G
•Tracking Area Identity = MCC (Mobile Country Code), MNC (Mobile Network Code) and TAC (Tracking Area
User PDUs
GTP-U UDP IP
Serving Gateway
LTE Functional Nodes- (MME) IMSI: Home -HSS •Used to uniquely identify a subscriber world-wide.
V-HSS
•Its structure is kept in form of •MCC+MNC+MSIN:MCC •MSIN: mobile subscriber identification number
S6a
MME uses the IMSI to locate the HSS holding the subscribers permanent registration data for tracking area updates and attaches. NAS Protocols
eNB
S1-AP SCTP
Tracking Area Update Request
IP L1/L2
S-TMSI/IMSI,
S1-MME (Control Plane)
MME
LTE Functional Nodes- (MME) S-TMSI: •It is dynamically allocated by the serving MME. •Its main purpose is to avoid usage of IMSI on air. •Internally the allocating MME can translate STMSI into IMSI and vice versa. NAS Protocols
eNB
S1-AP SCTP
Tracking Area Update Request
IP L1/L2
S-TMSI/IMSI,
S1-MME (Control Plane)
MME
Summary Attach EMM deregistered
EMM registered Detach
EMM-DEREGISTERED: •In this state the MME holds no valid location information about the UE
•Successful Attach and Tracking Area Update (TAU) procedures lead to transition to EMMREGISTERED
EPS Mobility Management
RRC States – Idle OR Connected In the early deployment phase, LTE coverage will certainly be restricted to city and hot spot areas.
Cell DCH Connected
Connection Cell FACH Establishment/ Release
Handover
LTE Connected
GPRS Packet Transfer Connection Establishment/Release
Cell URA Cell PCH
IDLE
Handover
GSM Connected
LTE _IDLE
Cell Selection /Reselection
Connection Establishment/Release
GSM/GPRS IDLE
RRC Connected – Always ON
HSS
MME triggered SAE bearer setup: This happens typically during the attach procedure of an UE. HO Handovers supported – Signaling Bearer to MME
MME S1-MME (Control Plane)
S11 LTE-Uu
eNB S1-U
Serving Gateway
DEFAULT SAE Bearer Service
S5
PDN Gateway Internet
External Bearer Service
RRC Connected
HSS
MME triggered SAE bearer setup: Depending on the information coming from HSS, the MME will set up an initial SAE bearer, also known as the default SAE bearer. This SAE bearer provides the initial connectivity of the UE with its external data network
S1-MME (Control Plane)
MME S1-MME (Control Plane)
S11 LTE-Uu
eNB S1-U
Serving Gateway
DEFAULT SAE Bearer Service
S5
PDN Gateway Internet
External Bearer Service
IP Address Allocation with Default bearer
Setting up a default bearer IDLE
RRC Connected
•Cell Selection done by UE •Based on UE measurements •Controlled by parameters
•Network controlled handovers •Based on UE measurements •ALWAYS ON
MUST PERFORM ATTACH CCCH:RRC Connection Request • Admission control
CCCH:RRC Connection Set up DCCH:RRC Connection Set up Complete Connected DEFAULT BEARER SET UP
IP Address Allocation with Default bearer
LTE Functional Nodes- default SAE bearer. LTE-Uu
eNB S1-U
Serving Gateway
S5
PDN Gateway Internet
SIP server SIP
default SAE bearer NGBR
•The default SAE bearer is created after the UE performs the attach. •Subsequent SAE bearers are known as dedicated SAE bearers. •They are expected to be allocated on a per application base VoIP
dedicated SAE bearers - GBR
Dedicated SAE bearers are to be triggered by Service Request
Set up dedicated SAE bearers. LTE-Uu
eNB S1-U
Serving Gateway
S5
PDN Gateway Internet
External Bearer Service
default SAE bearer NGBR
SERVICE REQUEST
RRC Reconfig
RRC ACK
SERVICE REQUEST
MME
Initial Context
Context ACK
Update Bearer
Update ACK
RRC IDLE
HSS
•IDLE •NO S1 BEARER •Cell Selection done by UE •Based on UE measurements •TRACKING AREA UPDATE
MME S1-MME (Control Plane)
LTE-Uu
eNB S1-U
Serving Gateway
S5
•In this state the MME holds location information for the UE at least to the accuracy of a tracking area •In this state the UE performs TAU procedures, responds to paging messages and performs the service request procedure if there is uplink data to be sent
PDN Gateway Internet
LTE Functional Nodes- (MME) LTE-Uu
MME
Paging S-TMSI,
Paging S-TMSI,
Service Request S-TMSI RRC_Connected Connected
Serving Gateway
PDN Gateway Internet
DL Packet Notification
DL Data
RRC IDLE – Cell Selection
eNB
RRC IDLE BCCH SIB’s
BCH
DL-SCH
MIB
Radio Block
PBCH
PDSCH
RRC IDLE Logical channels BCCH
MIB BCH
Transport channels DL-SCH
Physical channels PBCH
W B z h M 0 2
MIB BW = 1.08Mhz
PDSCH
RSRP (Reference Signal Received Power) RSRP is a RSSI type of measurement. It measures the average received power over the resource elements that carry cellspecific reference signals within certain frequency bandwidth . RSRP is applicable in both RRC_idle and RRC_connected modes
Radio Block
reference signals Are transmitted in ALL radio blocks
Physical Cell Identity (PCI) The UE moving towards a new cell and identifies the Physical Cell Identity (PCI) based on the Synchronization signals Physical Cell Identity (PCI) = 504
P-SCH
S-SCH
•P-SCH: for cell search and identification by the UE -Carries part of the cell ID (one of 3 orthogonal sequences)
•S-SCH: for cell search and identification by the UE Carries the remainder of the cell ID (one of 168 binary sequences)
Cell Reselection: PCI
PCI
PCI
PCI
Measurement criteria
Measured neighbours S – criteria Srx > Q rxlevmeas – (qrxlevmin – Qrelevmin offset)
Suitable neighbours
R – criteria neighboring cell was ranked with the highest value R
Best ranked cell
Re-selection if not serving cell
LTE_ACTIVE idle (Cell Selection) LTE_ACTIVE idle
RRC – Idle Cell Selection done by UE Base on UE Measurements
For a cell to be suitable: S rx level>0 Srx > Q rxlevmeas – (qrxlevmin – Qrelevmin offset) Q rxlevmeas RSRP (Reference Signal Received Power)
reference signals Are transmitted in ALL radio blocks
RSRP (Reference Signal Received Power) RSRP is a RSSI type of measurement. It measures the average received power over the resource elements that carry cell-specific reference signals within certain frequency bandwidth. RSRP is applicable in both RRC_idle and RRC_connected modes
W B z h M 0 2
REF BW = 1.08Mhz
LTE_ACTIVE idle (Cell Selection) For a cell to be suitable: S rx level>0 Srx > Q rxlevmeas – (qrxlevmin – Qrelevmin offset) Srx = -100 – (-80) = -20 (Will not do cell selection)
Q qrxlevmin =-80dBm
Q rxlevmeas=-100dBm Will not do cell selection Q rxlevmeas RSRP (Reference Signal Received Power)
Cell Reselection: R-Criterion PCI
PCI
PCI
Measurement criteria
Measured neighbours S – criteria
Suitable neighbours R – criteria Rs = Qmeas,s + Qhysts cell)
Rn = Qmeas,n - Qoffsets,n for candidate neighbouring cells for cell reselection
Best ranked cell
PCI
Cell Reselection: R-Criterion Rs = Qmeas,s + Qhysts (for the serving cell)
) M B d ( P R S R
Rn > Rs =>“cell reselecti
Qmeas,n
Rn
Qmeas,s Qhysts
Rs Qoffsets,n Treselection the time interval value Treselection, whose value ranges between 0 and 31 seconds
HANDOVER – RRC CONNECTED
LTE Functional Nodes- Management Entity (MME S1-AP UE ID: •Two additional temporary identifiers allocated by eNB and MME: - eNB S1-AP UE ID - MME S1-AP IE ID
S1-MME (Control Plane)
MME
NAS Protocols
S1-AP SCTP IP
eNB
L1/L2 S1-U (User Plane) User PDUs
GTP-U UDP IP
Serving Gateway
LTE Functional Nodes- X2 X2-CP X2-UP (Control Plane) (User Plane)
Connected Mode User PDUs
X2-AP
eNB
GTP-U
X2 SCTP
UDP
IP
IP
L1/L2
L1/L2
eNB
User plane switching in Handover
RLC
RLC
RLC
X2 Connection
RLC
RLC RLC
Handover Connected Mode Mobility In LTE_ACTIVE, when a UE moves between two LTE cells
User Plane TCP/UDP
A T A D Serving Gateway
MME
NAS
GTP -C
UDP IP L2 Ethernet NAS
L1-SDH
GTP -C
UDP
GTP -U
UDP
IP
IP
L2 Ethernet
L2 Ethernet
L1-SDH
L1-SDH
S1AP SCTP IP L2 (Ethernet)
Control
IP
NAS
PDCP RLC
RRC RLC
MAC
MAC
PHY
PHY
Control
NAS RRC RLC MAC PHY
S1AP SCTP IP L2 (Ethernet)
DIRECTION S1Cont rol MME
LTE Functional Nodes-eNodeB •2G network operators need to define the neighbour lists • Also 3G network operators need to define the neighbour lists but it is possible for UE to detect the new cells outside neighbour list which makes neighbour list creation simpler.
AUTOMATIC NEIGHBOUR RELATIONS The UE can detect the intra frequency neighbours WITHOUT neighour lists
LTE_Conected
The UE moving towards a new cell and identifies the Physical Cell Identity (PCI) based on the Synchronization signals Physical Cell Identity (PCI) = 504 The measurement report contains information about the PCI and the corresponding RSRP of the candidate cell
UE MEASUREMENT RORT WITH PCI
Seving eNodeB
AUTOMATIC NEIGHBOUR RELATIONS THERE IS NO X2 CONNECTION Therefore the serving eNodeB requests the UE to decode the Global Cell ID from broadcast channel
LTE_Connected state
The PCI cannot uniquely ID cell there could be thousands of cells Seving eNodeB
UE MEASUREMENT RORT WITH PCI
Request for Global cell ID
AUTOMATIC NEIGHBOUR RELATIONS LTE_Connected state The globally unique cell identifier (GID) in LTE consists of two parts: • PLMN Identity: The identity of the Public Land Mobile Network. Note that a cell may have multiple PLMN identities. • CIPL: Unique Cell Identity for a cell within a PLMN Seving eNodeB
UE MEASUREMENT RORT WITH PCI
Request for Global cell ID
UE reports Global Cell ID
UE to decode the Global Cell ID from broadcast channel
AUTOMATIC NEIGHBOUR RELATIONS whenever a new cell is introduced into the system it contacts a Operation Support Systems (OSS) in the network. The configuration server provides the new cell with the GID identity and an IP address OR/AND VLAN ID
NEW CELL ADDED
GID IP address VLAN
Operation Support Systems (OSS)
OSS may initiate a network wide re-planning of PCIs when a conflict is detected. neighbor cell relation (NCR)
neighbor cell relation (NCR)
10,6
6,5,10 Serving Cell PCI=10
PCI= 5
Operation Support Systems (OSS)
PCI= 6 neighbor cell relation (NCR)
5,10
PCI=10
neighbor cell relation (NCR)
6,5
AUTOMATIC NEIGHBOUR RELATIONS The serving cell may order the mobile to read the GID This could be done for example: if the PCI is associated with a cell with handover failures in the past or if a central node such as the OSS has requested it. Or PCI conflicts
This method makes use of mobile measurements to update the neighbour cell relation lists in the cells and to detect local cell identity conflicts, report the conflicts to the Operation Support Systems (OSS
PCI= 6 neighbor cell relation (NCR)
5,10
Example When a measurement report is received from a mobile it is handled according to the following scheme:
Is the PCI of the candidate cell already known in the serving cell (i.e. is the neighbour relation already established)? Yes: Initiate handover decision procedure. Neighbour Cell Relation (NCR) PCI
VLAN ID
IP address
50
20
10.1.1.1 UE MEASUREMENT RORT WITH PCI
PCI=50
PCI=40
Example Is the PCI of the candidate cell already known in the serving cell (i.e. is the neighbour relation already established)? No: Consider the candidate cell as a NCR list candidate. Order the UE to report GID. Obtain connectivity information for the candidate cell and signal to the candidate cell, directly or through the core network, about a mutual addition to the NCR lists of the two cells. neighbor cell relation (NCR) 40
neighbor cell relation (NCR)
UE MEASUREMENT RORT WITH PCI
PCI=50 candidate
Request for Global cell ID
PCI=40
Hand over -Inter Frequency
Transmission Gap Idle period Minimum one sub-frame Configured in UE by Enode B UE needs Inter frequent Neighbour list
Questions How many PCI are there?
What is the function of the MIB?
What physical channel is the MIB transmitted on?
What is the bandwidth of a radio Block?
