Mobile Network Evolution Part 2

Transcription

1 Mobile Network Evolution Part 2 From UMTS to LTE or How to Further Increase Network Capacity and QoS Andreas Mitschele-Thiel Advanced Mobile Communication Networks 1

2 Outline Evolution from Circuit Switching to Packet Switching Architecture Packet handling Resource management and QoS Comparison with LTE Features and requirements Architecture Protocols Packet handling and resource management Mobility management and HO Self-organization Conclusions References Abbreviations Advanced Mobile Communication Networks 2

3 Review: From GSM to UMTS Base station Base station PSTN Base station +EDGE GSM RAN Base station controller MSC GSM Core (Circuit switched) GMSC HLR AuC EIR node B node B +HSPA node B UTRAN Radio network controller SGSN GPRS Core (Packet Switched) IMS GGSN Internet Advanced Mobile Communication Networks 3

4 Circuit vs. Packet Switched Communication Connection (e.g. voice, CS data) => principle for GSM & UTRAN design clearly defined start and end times no burstiness => dedicated channels connection setup connection release Packet session => supported by GPRS core, IMS, SAE, HSPA, LTE packet arrival times are typically unknown to the system traffic is highly bursty => shared channels & packet scheduling minutes hours seconds Advanced Mobile Communication Networks 4

5 Resource Management in UMTS (radio link) When to free resources? After short or long breaks? hours cell_dch cell_fach URA_PCH idle fast release seconds slow release Advanced Mobile Communication Networks 5

6 Resource Management in UMTS (radio link) When to free resources? After short or long breaks? latency idle setup delay T 3 URA_PCH T 2 transient resource usage cell_fach resource consumption T 1 cell_dch radio resources channel codes HW resources Advanced Mobile Communication Networks 6

7 End-to-End Resource Management in UMTS (contr. plane) A sophisticated QoS architecture TE Local Service Control Transl. MT UMTS BS Adm./Cap. Control UTRAN Adm./Cap. Control RAB Adm./Cap. Control CN EDGE UMTS BS Subscr. Control Gateway Adm./Cap. Control UMTS BS Transl. Ext. Netw. Ext. Service Control Local BS Radio BS Radio BS Iu BS Adm. Iu BS Contr CN BS CN BS Ext. BS UTRA ph. BS M UTRA ph. BS M Iu NS Iu NS BB NS BB NS service primitive interface protocol interface Advanced Mobile Communication Networks 7

8 End-to-End Resource Management in UMTS (user plane) TE MT UTRAN CN EDGE Gateway Ext. Netw. Class if Class if Cond. Cond. Cond. Mapper Mapper Mapper Local BS Resource Resource Resource Resource Resource Resource External BS UTRA phys. BS Iu network service BB network service data flow with indication of direction Advanced Mobile Communication Networks 8

9 Evolution from GSM to UMTS and LTE GSM: voice-dominated, dedicated channels, heavy states GPRS: add support for packet data on shared channels; add IP-based core network EDGE: increased packet data capacity of GSM system UMTS: separate voice and packet data support; focus on dedicated channels and heavy states, complicated RAN architecture and protocols due to macro diversity and QoS requirements HSPA: improved support for packet data; emphasis on shared channels and fast radio resource management IMS: support for IP-based services, e.g. voice (VoIP) LTE: strong packet data support (latency, throughput, control overhead), limited state; simplified protocols; PS only, i.e. no CS core network Transition from circuit switching to packet switching from slow, explicit setup and release of resources to fast channelcondition- and demand-specific resource management Advanced Mobile Communication Networks 9

10 Evolution towards LTE Architecture LTE radio system is a packet-only network - there is no support for circuit-switched services (no MSC) LTE starts on a clean state - everything is up for discussion including the system architecture and the split of functionality between Radio Access Network (RAN) and Core Network (CN) 3GPP (3 rd Generation Partnership Program) study items 3G Long-term Evolution (LTE) for new Radio Access and System Architecture Evolution (SAE) for Evolved Network Advanced Mobile Communication Networks 10

11 Evolution towards LTE Architecture Base station Base station PSTN Base station GSM RAN Base station controller MSC GSM Core (Circuit switched) GMSC HLR AuC EIR e- node B e- node B e-node B S-GW E-UTRAN Radio network controller SGSN EPC GPRS Core (Packet Switched) P-GW IMS GGSN Internet Advanced Mobile Communication Networks 11

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13 LTE: Evolved Packet System (EPS) Architecture Key elements of network architecture MME/S-GW MME/S-GW No more RNC RNC layers/functionalities moves in enb X2 interface for seamless mobility (i.e. data/context forwarding) and interference management Note: Standard only defines logical structure! enb S1 X2 S1 S1 S1 S1 X2 enb S1 X2 enb EPC E-UTRAN EPC = Evolved Packet Core Advanced Mobile Communication Networks 13

14 LTE: Requirements and Performance Targets Advanced Mobile Communication Networks 14

15 LTE Key Features (Release 8) Multiple access scheme DL: OFDMA with Cyclic Prefix (CP) UL: Single Carrier FDMA (SC-FDMA) with CP Adaptive modulation and coding DL modulations: QPSK, 16QAM, and 64QAM UL modulations: QPSK and 16QAM (optional for UE) Rel. 6 Turbo code: Coding rate of 1/3, two 8-state constituent encoders, and a contention-free internal interleaver ARQ within RLC sublayer and Hybrid ARQ within MAC sublayer Advanced MIMO spatial multiplexing techniques (2 or 4) x (2 or 4) downlink and uplink supported Multi-layer transmission with up to four streams Multi-user MIMO also supported Implicit support for interference coordination Support for both FDD and TDD Advanced Mobile Communication Networks 15

16 Multi-antenna Solutions Advanced Mobile Communication Networks 16

17 Scheduling and Resource Allocation (1/2) LTE uses a scheduled, shared channel on both the uplink (UL- SCH) and the downlink (DL-SCH) Normally, there is no concept of an autonomous transmission; all transmissions in both uplink and downlink must be explicitly scheduled LTE allows "semi-persistent" (periodical) allocation of resources, e.g. for VoIP Advanced Mobile Communication Networks 17

18 Scheduling and Resource Allocation (2/2) Basic unit of allocation is called a Resource Block (RB) 12 subcarriers in frequency (= 180 khz) 1 sub-frame in time (= 1 ms, = 14 OFDM symbols) Multiple resource blocks can be allocated to a user in a given subframe The total number of RBs available depends on the operating bandwidth Advanced Mobile Communication Networks 18

19 Interference Coordination Advanced Mobile Communication Networks 19

20 LTE vs. WiMax vs. 3GPP2 WiMAX IMS 3GPP/LTE PCRF IMS 3GPP2/UMB PCRF IMS AAA HA HSS PDN GW AAA HA Authenticator Paging Controller Page buffering CAP-C Handover Control Radio Resource Management ARQ/MAC/PHY L2 Ciphering Classification/ ROHC FA/Router Access Point Local mobility Session setup Bearer mapping Authenticator Paging Controller Session setup MME Handover Control Radio Resource Management ARQ/MAC/PHY E-Node B L2 Ciphering ROHC Bearer mapping Serv GW Local mobility Page buffering Authenticator Paging Controller SRNC Handover Control Radio Resource Management ARQ/MAC/PHY L2 Ciphering ROHC ebts Access GW Local mobility Session setup Bearer mapping IETF-centric architecture IETF-friendly, but still some flavor of UMTS/GPRS GTP, etc IETF-centric architecture Advanced Mobile Communication Networks 20

21 References LTE/SAE A. Toskala et al, UTRAN Long-Term Evolution, Chapter 16 in Holma/ Toskala: WCDMA for UMTS, Wiley 2007 E. Dahlman et al, 3G Evolution, HSPA and LTE for Mobile Broadband, Elsevier Journal, 2007 Special Issue on LTE/ WIMAX, Nachrichtentechnische Zeitung, pp , 1/2007 3rd Generation Partnership Project Long Term Evolution (LTE), official website: Technical Paper, UTRA-UTRAN Long Term Evolution (LTE) and 3GPP System Architecture Evolution (SAE), last update October 2006, available at: ftp://ftp.3gpp.org/inbox/2008_web_files/lta_paper.pdf Standards TS 36.xxx series, RAN Aspects TS , E-UTRAN; Overall description; Stage 2 TR , Feasibility study for evolved Universal Terrestrial Radio Access (UTRA) and Universal Terrestrial Radio Access Network (UTRAN) TR , Physical layer aspect for evolved UTRA TR , 3GPP System Architecture Evolution: Report on Technical Options and Conclusions Self-organizing networks and LTE Self-organizing networks and LTE, NGMN Recommendation on SON and O&M Requirements, Dec. 5, 2008, NGMN, Advanced Mobile Communication Networks 21