How to deal with a thousand nodes: M2M communication over cellular networks A. Maeder NEC Laboratories Europe [email protected] Outline ▐ Introduction to M2M communications  The M2M use case landscape  Properties and requirements ▐ Challenges for mobile cellular networks  Architecture  Challenges on RAN and core network ▐ Current efforts in standardization  ETSI: end-to-end framework for M2M  3GPP: Keep the operators into the value chain  IEEE: Optimize the radio access ▐ Conclusion and outlook ITG Zukunft der Netze 2011 The M2M use case landscape ITG Zukunft der Netze 2011 What is the issue? ▐ Cellular mobile networks are designed for human communication  Interactive communication between humans (voice, video)  Data communication involving humans (web browsing, file downloads, etc).  Communication is connection-centric ▐ Cellular mobile networks are optimized for traffic characteristics of human-based communication applications  Communication with a certain length (sessions) and data volume  Communication with a certain interaction frequency and patterns (talklisten, download-reading, etc.) But: M2M communication is different ITG Zukunft der Netze 2011 Example: Smart Grid/Smart Metering ▐ Control and reading of metering/infrastructure Wind Turbine Home displays TV, Computer Data Center Solar Panel In-Home Energy Display Wan Communication Light Meters Coms Appliances Temperature Breaker Valves Smart Water Smart Gas Smart Elec. Small message sizes Low to medium frequent communication Relaxed delay requirements High requirements on energy efficiency? Large number of devices “Alarm” scenarios ITG Zukunft der Netze 2011 Gateway Image source: ETSI Example scenario: smart meters per single cell Estimation based on census data One smart meter assumed per household ITG Zukunft der Netze 2011 Example: Intelligent Transport Systems High speed mobility Very high mobility/latency requirements Car-to-X: High mobility High speed Very low latency Security Image source: ETSI ITG Zukunft der Netze 2011 Properties and requirements of M2M applications Smart meters eHealth ITS Surveillance Mobility none Pedestrian /vehicular Vehicular none Message size Small (few kB) Medium? Medium large Traffic pattern Regular Regular/irregular Regular/irregular Regular Device density Very high (up to ten thousands per cell) Medium High low Latency requirements low (up to hours) Medium (seconds) Very high (few milliseconds) Medium (< 200ms) Power efficiency requirements High (battery powered meters) High (battery power devices) Low low Reliability High High High medium Security requirements High Very high Very high medium Diverse and challenging requirements for today’s mobile networks Requirements and traffic patterns are not clear today! ITG Zukunft der Netze 2011 Cellular M2M architecture Mobile operator M2M operator domain domain HSS M2M server applications M2M platform P-GW MTC server abstraction layer S-GW MME Mobile operator core network local How to integrate? breakout Radio Access Network (RAN) management operation control data transport addressing locating MTC device UE small cell eNB MTC device eNB femto/small cell UE femto/small cell ITG Zukunft der Netze 2011 eNB MTC device M2M device application M2M device application Challenges for radio access ▐ ▐ ▐ ▐ ▐ ▐ Many devices Long idle intervals Small message transmission Uplink is bottleneck Energy efficiency Human communication must not be affected! RACH Congestion eNB ITG Zukunft der Netze 2011 UE 1 eNB Random Access Preamble Random Access Response 3 2 Scheduled Transmission Contention Resolution 4 Random access procedure in LTE for attachment, uplink bandwidth requests ▐ Proposed solutions: ▐ Dedicated RACH ▐ Time backoff classes ▐ Slotted access ▐ Group coordination ▐ Access barring ▐ Randomization Challenges for non-access stratum Signaling congestion HSS S6a S11 MME S/P-GW S1-MME ▐ Each data transmission from idle mode requires a bearer setup  Complex procedure with several CN entities involved  Large overhead for small message sizes  May lead to signaling congestion and high computational load S1-U ▐ Proposed solutions: eNB ITG Zukunft der Netze 2011  Signaling aggregation  Signaling rejection/differentiation  Signaling reduction for MTC device classes Trade-off between control and scalability Security Charging QoS Management Monitoring Scheduled access Control Large device numbers Low latency Low power consumption Small burst transmission Low cost Low overhead Scalability Diverse and partially contradicting requirements Balancing mobile and M2M operator needs Is it sufficient to modify existing technologies? ITG Zukunft der Netze 2011 Activities in standards: ETSI ▐ ETSI develops an end-to-end framework for M2M ▐ Architecture highlights  Generic service capabilities for M2M applications in M2M server, gateway and devices  M2M identification and addressing scheme Network Domain  Framework for security and service bootstrap  Resource management framework ▐ Independent of transport network Device and Gateway Domain ▐ Interaction with MNO core network functions (but not access) ITG Zukunft der Netze 2011 M2M Applications M2M Service Capabilities M2M Management Functions Core Network (CN) Network Management Functions Access Network M2M Applications M2MService Capabilities M2M Gateway M2M M2MArea Area Network Network M2M Device M2M Applications M2M Service Capabilities M2M Device Activities in standards: 3GPP ▐ Two work items: network improvements for MTC (NIMTC, Rel. 10) and system improvements for MTC (SIMTC, Rel. 11) MTC User ▐ Current focus on architecture (MTC server), Service Logic Components control plane, services, features: TR 23.888 MTC Server Generic Service Layer API ▐ Study on RAN improvements finished in Sept.  TR 37.868, section on RAN overload control  Extended Access Barring (EAB) selected as solution Focus on architecture/services /signaling 3GPP MTC Service Abstraction Layer MTCsms SMSC MTCsms MTC Device MTCu PDN 3GPP PLMN MTC Server IWK Function 3GPP bearer services / SMS / IMS MTC Server MTC Server MTCsh MTCi PGW ... HSS 3GPP HPLMN 3GPP VPLMN eNB, RNC or BSC MTCi 3GPP MTC architecture ITG Zukunft der Netze 2011 MTCu MTC MTC MTC Device Device Device 3GPP MTC service abstraction Activities in standards: IEEE 802.16p ▐ ▐ ▐ ▐ IEEE 802.16p: started in Sept. 2009 Extension of 802.16e (WiMAX) and 802.16m (WiMAX 2.0) MAC and minimal OFDMA PHY enhancements Current status: enhancements for network entry, group control, multicast, mobility, dedicated random access resources ▐ Letter ballot in Nov. 2011, publish 2012 MNO (Mobile Network Operator) Access Service Network Focus on air interface/MAC IEEE 802.16 Non M2M device IEEE 802.16 M2M device Non IEEE 802.16 M2M device IEEE 802.16 M2M device Connectivity Service Network R1 M2M Server R1 IEEE 802.16 BS R1 802.16p M2M service reference system architecture ITG Zukunft der Netze 2011 M2M Subscriber Conclusion and Outlook ▐ M2M is an enabler of the Internet of Things. ▐ M2M is challenging for today’s and future cellular networks:  Interworking between M2M operator and mobile operator.  Diverse traffic characteristics and requirements on QoS, energy efficiency, … ▐ Efforts in Standards: “Fix” existing systems by adding as much as necessary, as less as possible. ▐ Research needs to think beyond this approach  M2M applications imply novel network performance metrics  Flexible MAC, low-overhead protocols, virtualization, energy efficiency, hierarchical networks, …  First step: M2M traffic models for popular use cases (e.g. smart meters)!  Talk to industries and users of M2M communications. ITG Zukunft der Netze 2011