L1/L2 Handoff Considerations based on Universal Mobile Telecommunications System (UMTS)

Transcription

1 L1/L2 Handoff Considerations based on Universal Mobile Telecommunications System (UMTS) Steve Dick InterDigital Communications Corporation 11 November

2 UTRAN Architecture 11 November , InterDigital Communications Corporation 2

3 UTRA and cdma2000 based on Code Division Multiple Access(CDMA) 11 November , InterDigital Communications Corporation 3

4 Universal Terrestrial Radio Access (UTRA) L1/L2 functions L1 GC Nt DC Duplication avoidance Physical (PHY) GC Nt DC UuS boundary L2 C-plane signalling U-plane information Medium Access Control (MAC) Radio Link Control() control control control control RRC control PDCP PDCP L3 Radio Bearers L2/PDCP BMC L2/BMC Broadcast/Multicast(B MC) Packet Data Convergence Protocol(PDCP) MAC PHY L2/ Logical Channels L2/MAC Transport Channels L1 11 November , InterDigital Communications Corporation 4

5 Mobility Functions Cell Reselection Handover 11 November , InterDigital Communications Corporation 5

6 Handover Types Intra-RAT (Radio Access Technology) Intra-Frequency Hard Soft Inter-Frequency Intra-Mode (TDD <>TDD) Inter-Mode (FDD<>TDD) Inter-RAT UMTS<>GSM UMTS <>WLAN 11 November , InterDigital Communications Corporation 6

7 Soft and Hard Handover Soft Handover Cell 1 Cell 2 Hard Handover Cell 1 Cell 2 11 November , InterDigital Communications Corporation 7

8 Soft Handover is well suited to CDMA User Equipment (UE) is connected to several access points at the same time. The soft handover function includes measurement phase, decision algorithm in UTRAN ACTIVE SET UPDATE procedure. Spreading Factor and Rake Receiver permit simultaneous processing of multiple transmissions Rake Combining of transmissions from different Base Stations similar to multipath processing 11 November , InterDigital Communications Corporation 8

9 Hard Handover Time Line Y-Axis Cell 1 Y-Axis Ideal Switch Point Disconnect Cell 1 Connect Cell2 Cell 2 Handover Delay Interrupt Time Delay Signal to Interference Ratio measurement Higher Layer Signaling Decisions in Radio Network Controller Interruption Time Cell search and synchronization Acquire in-sync indication from network 11 November , InterDigital Communications Corporation 9

10 General Measurement Requirements Pilot power, Signal to Noise Ratio Basis for handover Identification of a new cell Within a specified time period Two basic criteria for reporting Periodic Reporting Event Triggered Reporting 11 November , InterDigital Communications Corporation 10

11 Compressed Mode Required for Inter-frequency measurements Single Receiver UE s must be given time to make the necessary measurements on the different WCDMA carrier frequency. 1 to 7 slots per (15 slot) frame can be allocated for the UE to perform this intra frequency (hard handover). Can either be in the middle of a single frame or spread over two frames. 11 November , InterDigital Communications Corporation 11

12 UTRA Measurements Measurements by UE Measurements by Network CPICH RSCP (Received Signal Code Power) Received total wideband power CPICH Ec/Io SIR UTRA Carrier RSSI SIRerror GSM carrier RSSI Transmitted carrier power Transport channel BLER Transmitted code power UE transmitted power Physical channel BER SFN-CFN observed time difference Round trip time SFN-SFN observed time difference Transport Channel BER UE Rx-Tx time difference UTRAN GPS Timing of Cell Frames for UE positioning Observed time difference to GSM cell PRACH/PCPCH Propagation delay P-CCPCH RSCP Acknowledged PRACH preambles UE GPS Timing of Cell Frames for UE Detected PCPCH access preambles positioning Acknowledged PCPCH access preambles SFN-SFN observed time difference 11 November , InterDigital Communications Corporation 12

13 Handover Measurement Reporting The Network Radio Resource Controller sends MEASUREMENT CONTROL message to the UE Measurement type The radio links to evaluate The reporting criteria Measurement identity number. The UE configures L1 to start measurements. When measurement reporting criteria are fulfilled the UE sends a MEASUREMENT REPORT message. UE-RRC UE-L1 SRNC-RRC Reporting criteria fulfilled CPHY-Measurement-REQ CPHY-Measurement-IND MEASUREMENT REPORT Measurement Measurement CPHY-Measurement-IND Uu Iub MEASUREMENT CONTROL 11 November , InterDigital Communications Corporation 13

14 Power / Battery Life Size, Weight Complexity Derived Guidelines Practical Issues Permit single receiver design Permit UE to sleep when not connected Time synchronized Base Stations cdma2000, cdmaone yes UTRA FDD - no UTRA TDD - not required, but optional 11 November , InterDigital Communications Corporation 14

15 References WCDMA for UMTS, Radio Access for Third Generation Mobile Communications, Harri Holma and Antti Toskala, John Wiley & Sons, Ltd, 2000 Websites: InterNational Engineering Consortium ( The Hong Kong Polytechnic University-Department of Electronic & Information Engineering, UMTS World Third Generation Partnership Project 11 November , InterDigital Communications Corporation 15