LTE Mobility1 Copyright 2010 AIRCOM International Air Interface – Rel’99 / Rel 4 CELL URA CELLPCH CELL DCH QoS CELL FACH NO QoS IDLE 2 Copyright 2010 AIRCOM International 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 Handover LTE Connected Handover GSM Connected Connection Cell FACH Establishment/ Release Cell URA Cell PCH GPRS Packet Transfer Connection Establishment/Release Connection Establishment/Release Reselection IDLE LTE _IDLE GSM/GPRS IDLE 3 Copyright 2010 AIRCOM International UE Power up UE Power up DL Syn and Physical Channel ID Acquire another LTE Cell Find 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 Cell Barred Cell Selection Successful 4 After Attach –Defaulf Bearer/IP adress Yes Pre-amble / Attach Copyright 2010 AIRCOM International EPS Mobility Management Evolved Packet Core (EPC) EPS Mobility Management 2 states: EMM-DEREGISTERED EMM-REGISTERED HSS Evolved UTRAN (E-UTRAN) MME: Mobility Management Entity S6a X2 S1-MME S11 S1-U LTE-Uu Serving Gateway MME S7 PCRF Evolved Node B (eNB) LTE-UE S5 Internet PDN Gateway 5 Copyright 2010 AIRCOM International . 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 MME 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 6 Copyright 2010 AIRCOM International . MNC (Mobile Network Code) and TAC (Tracking Area Code Tracking Area Tracking Area NAS: Tracking Area update 7 s6a MME Home HSS Copyright 2010 AIRCOM International .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).Tracking Area update . Tracking Area update .IDLE Tracking areas are allowed to overlap: one cell can belong to multiple tracking areas TAI1 TAI1-2 TAI1 TAI1-2 TAI2 TAI1 TAI2 TAI2 TAI2 TAI2 TAI2 TAI2 TAI2 TAI2 TAI2 TAI2 TAI3 TAI3 TAI3 TAI3 8 NAS: Tracking Area update MME Copyright 2010 AIRCOM International . MNC (Mobile Network Code) and TAC (Tracking Area 9 Code User PDUs GTP-U UDP IP Serving Gateway Copyright 2010 AIRCOM International L1/L2 .LTE Functional Nodes.Management Entity (MME Tracking Area Update Request S-TMSI/IMSI. PDN address allocation Tracking Area Update Accept MME Tracking Area Update Complete S1-MME (Control Plane) 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). •Its structure is kept in form of •MCC+MNC+MSIN:MCC •MSIN: mobile subscriber identification number MME uses the IMSI to locate the HSS holding the subscribers permanent registration data for tracking area updates and attaches. 10 IP L1/L2 S1-MME (Control Plane) Copyright 2010 AIRCOM International . NAS Protocols V-HSS S6a eNB S1-AP SCTP MME Tracking Area Update Request S-TMSI/IMSI.LTE Functional Nodes.(MME) IMSI: Home -HSS •Used to uniquely identify a subscriber world-wide. •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 MME Tracking Area Update Request S-TMSI/IMSI.(MME) S-TMSI: •It is dynamically allocated by the serving MME. 11 IP L1/L2 S1-MME (Control Plane) Copyright 2010 AIRCOM International .LTE Functional Nodes. Summary Attach EMM deregistered 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 EMM registered EPS Mobility Management 12 Copyright 2010 AIRCOM International . GSM Connected GPRS Packet Transfer Connection Establishment/Release Connection Establishment/Release Cell DCH Connected Handover LTE Connected Handover Connection Cell FACH Establishment/ Release Cell URA Cell PCH IDLE LTE _IDLE GSM/GPRS IDLE Cell Selection /Reselection 13 Copyright 2010 AIRCOM International .RRC States – Idle OR Connected In the early deployment phase. LTE coverage will certainly be restricted to city and hot spot areas. HO Handovers supported – Signaling Bearer to MME HSS MME S1-MME (Control Plane) S11 LTE-Uu eNB S1-U Serving Gateway PDN Gateway Internet S5 DEFAULT SAE Bearer Service External Bearer Service 14 System Architecture Evolution.RRC Connected – Always ON MME triggered SAE bearer setup: This happens typically during the attach procedure of an UE.SAE Copyright 2010 AIRCOM International . also known as the default SAE bearer.SAE Copyright 2010 AIRCOM International .RRC Connected MME triggered SAE bearer setup: Depending on the information coming from HSS. the MME will set up an initial SAE bearer. This SAE bearer provides the initial connectivity of the UE with its external data network HSS S1-MME (Control Plane) MME S1-MME (Control Plane) S11 LTE-Uu eNB S1-U Serving Gateway PDN Gateway Internet S5 DEFAULT SAE Bearer Service External Bearer Service IP Address Allocation with Default bearer 15 System Architecture Evolution. Setting up a default bearer IDLE •Cell Selection done by UE •Based on UE measurements •Controlled by parameters MUST PERFORM ATTACH CCCH:RRC Connection Request • Admission control RRC Connected •Network controlled handovers •Based on UE measurements •ALWAYS ON CCCH:RRC Connection Set up DCCH:RRC Connection Set up Complete Connected DEFAULT BEARER SET UP 16 IP Address Allocation with Default bearer Copyright 2010 AIRCOM International . LTE Functional Nodes.default SAE bearer. •They are expected to be allocated on a per application base VoIP dedicated SAE bearers . 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.GBR Dedicated SAE bearers are to be triggered by Service Request 17 Copyright 2010 AIRCOM International . •Subsequent SAE bearers are known as dedicated SAE bearers. Set up dedicated SAE bearers. LTE-Uu eNB S1-U Serving Gateway S5 PDN Gateway Internet default SAE bearer NGBR External Bearer Service SERVICE REQUEST SERVICE REQUEST MME RRC Reconfig Initial Context RRC ACK Context ACK Update Bearer Update ACK 18 Copyright 2010 AIRCOM International . responds to paging messages and performs the service request procedure if there is uplink data to be sent 19 Copyright 2010 AIRCOM International .RRC IDLE •IDLE •NO S1 BEARER •Cell Selection done by UE •Based on UE measurements •TRACKING AREA UPDATE S1-MME (Control Plane) HSS MME LTE-Uu eNB S1-U Serving Gateway S5 PDN Gateway Internet •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. LTE Functional Nodes. DL Packet Notification DL Data Service Request S-TMSI RRC_Connected Connected 20 Copyright 2010 AIRCOM International . Paging S-TMSI.(MME) LTE-Uu MME Serving Gateway PDN Gateway Internet Paging S-TMSI. RRC IDLE – Cell Selection eNB 21 Copyright 2010 AIRCOM International . RRC IDLE BCCH SIB’s BCH MIB Radio Block DL-SCH PDSCH PBCH 22 Copyright 2010 AIRCOM International . 08Mhz 23 Copyright 2010 AIRCOM International .RRC IDLE Logical channels BCCH MIB BCH DL-SCH Transport channels Physical channels PBCH PDSCH 20Mhz BW MIB BW = 1. 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 24 Copyright 2010 AIRCOM International .RSRP (Reference Signal Received Power) RSRP is a RSSI type of measurement. 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) 25 Copyright 2010 AIRCOM International . Cell Reselection: PCI Measurement criteria PCI PCI PCI Measured neighbours S – criteria Srx > Q rxlevmeas – (qrxlevmin – Qrelevmin offset) R – criteria neighboring cell was ranked with the highest value R Suitable neighbours Best ranked cell Re-selection if not serving cell 26 Copyright 2010 AIRCOM International . 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 27 Copyright 2010 AIRCOM International . RSRP (Reference Signal Received Power) RSRP is a RSSI type of measurement. RSRP is applicable in both RRC_idle and RRC_connected modes 20Mhz BW REF BW = 1.08Mhz 28 Copyright 2010 AIRCOM International . It measures the average received power over the resource elements that carry cell-specific reference signals within certain frequency bandwidth. 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) 29 Copyright 2010 AIRCOM International . n for candidate neighbouring cells for cell reselection 30 Copyright 2010 AIRCOM International .Qoffsets.s + Qhysts cell) Best ranked cell Rn = Qmeas.Cell Reselection: R-Criterion PCI Measurement criteria PCI PCI PCI Measured neighbours S – criteria Suitable neighbours R – criteria Rs = Qmeas.n . Cell Reselection: R-Criterion Rs = Qmeas. whose value ranges between 0 and 31 seconds 31 Copyright 2010 AIRCOM International .n Treselection the time interval value Treselection.n RSRP (dBM) Rn Qmeas.s + Qhysts (for the serving cell) Rn > Rs =>“cell reselectio Qmeas.s Qhysts Rs Qoffsets. HANDOVER – RRC CONNECTED 32 Copyright 2010 AIRCOM International . Management Entity (MME S1-AP UE ID: •Two additional temporary identifiers allocated by eNB and MME: .MME S1-AP IE ID eNB S1-MME (Control Plane) NAS Protocols MME S1-AP SCTP IP L1/L2 S1-U (User Plane) User PDUs GTP-U UDP IP 33 Serving Gateway Copyright 2010 AIRCOM International L1/L2 .eNB S1-AP UE ID .LTE Functional Nodes. X2 X2-CP X2-UP (Control Plane) (User Plane) Connected Mode User PDUs eNB X2-AP GTP-U X2 SCTP UDP IP IP eNB L1/L2 L1/L2 34 Copyright 2010 AIRCOM International .LTE Functional Nodes. User plane switching in Handover RLC RLC RLC X2 Connection RLC RLC RLC 35 Copyright 2010 AIRCOM International . Handover Connected Mode Mobility In LTE_ACTIVE. when a UE moves between two LTE cells DATA User Plane TCP/UDP IP PDCP RLC MAC PHY Control NAS RRC RLC MAC PHY Serving Gateway MME NAS Control NAS RRC RLC MAC PHY GTP -C UDP IP L2 Ethernet GTP -C UDP IP L2 Ethernet L1-SDH GTP -U UDP IP L2 Ethernet L1-SDH S1AP SCTP IP L2 (Ethernet) NAS S1AP SCTP IP L2 (Ethernet) L1-SDH DIRECTION S1Cont rol MME 36 Copyright 2010 AIRCOM International . 37 Copyright 2010 AIRCOM International .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 38 Copyright 2010 AIRCOM International . 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 39 Copyright 2010 AIRCOM International . Note that a cell may have multiple PLMN identities.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. • CIPL: Unique Cell Identity for a cell within a PLMN Seving eNodeB UE MEASUREMENT RORT WITH PCI Request for Global cell ID UE to decode the Global Cell ID from broadcast channel UE reports Global Cell ID 40 Copyright 2010 AIRCOM International . The configuration server provides the new cell with the GID identity and an IP address OR/AND VLAN ID GID NEW CELL ADDED IP address VLAN Operation Support Systems (OSS) 41 Copyright 2010 AIRCOM International .AUTOMATIC NEIGHBOUR RELATIONS whenever a new cell is introduced into the system it contacts a Operation Support Systems (OSS) in the network. OSS may initiate a network wide re-planning of PCIs when a conflict is detected.5. neighbor cell relation (NCR) 10.10 42 6.10 Operation Support Systems (OSS) PCI= 6 neighbor cell relation (NCR) PCI=10 neighbor cell relation (NCR) 5.5 Copyright 2010 AIRCOM International .6 PCI= 5 Serving Cell PCI=10 neighbor cell relation (NCR) 6. report the conflicts to the Operation Support Systems (OSS PCI= 6 neighbor cell relation (NCR) 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.10 43 Copyright 2010 AIRCOM International . 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. Neighbour Cell Relation (NCR) PCI 50 VLAN ID 20 IP address 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.1. is the neighbour relation already established)? Yes: Initiate handover decision procedure.e.1 UE MEASUREMENT RORT WITH PCI PCI=50 PCI=40 44 Copyright 2010 AIRCOM International .1. Order the UE to report GID. is the neighbour relation already established)? No: Consider the candidate cell as a NCR list candidate. directly or through the core network.e. Obtain connectivity information for the candidate cell and signal to the candidate cell.Example Is the PCI of the candidate cell already known in the serving cell (i. neighbor cell relation (NCR) 40 neighbor cell relation (NCR) UE MEASUREMENT RORT WITH PCI PCI=50 Request for Global cell ID candidate PCI=40 45 Copyright 2010 AIRCOM International . about a mutual addition to the NCR lists of the two cells. Hand over -Inter Frequency Transmission Gap Idle period Minimum one sub-frame Configured in UE by Enode B UE needs Inter frequent Neighbour list 46 Copyright 2010 AIRCOM International . 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? 47 Copyright 2010 AIRCOM International . Questions What is the function of the S-TMSI and what allocates it? The total number of handovers are likely to be higher in LTE than in UMTS.Why? What is meant by a VLAN? 48 Copyright 2010 AIRCOM International ..