Shaping mobile networks for the IoT

Transcription

1 Shaping mobile networks for the IoT Massimo Condoluci Research Associate Department of Informatics Centre for Telecommunications Research King s College London

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4 Outline Introduction to IoT and LPWA technologies Introduction to mobile networks Cellular IoT The IoT in the mobile core network 4

5 Introduction to IoT and Low Power Wide Area (LPWA) Networks Massimo Condoluci Research Associate Department of Informatics Centre for Telecommunications Research King s College London

6 Internet of Things 6

7 Internet of Things Orange and Ericsson, Traffic Model for legacy GPRS MTC; document GP GPP GERAN meeting #69, Feb

8 Machine-type communications 8

9 Internet of Things Zone Central Urban MTC Devices Per Cell (164560) ( ) Smartphones per Cell Zone Pop. Density SqKm per Pop. Density per Household Household density per sqkm Cell Radius Km Household per cell MTC Devices Per Household Central 1E Urban 7.5E (4114) (29508) Zone MTC Devices Per Cell (no Mob.) Device Triggered Reporting Time T (Sync Unif. Over T) (Async Beta Over T) Packet Size (UL) Network Triggered Reporting Time T (Sync Unif. Over T) (Async Beta Over T) Packet Size (DL/UL) Central m, 5m, 1h, 12h, 24h 1000, m, 5m, 1h, 12h, 24h 1000,10000/400 Urban m, 5m, 1h, 12h, 24h 1000, m, 5m, 1h, 12h, 24h 1000,10000/400 3GPP TR Annex B and TR Annex E 9

10 Internet of Things Total density: device/sqkm Total traffic: ~35000 device/hour = ~10 pkts/s Orange and Ericsson, Traffic Model for legacy GPRS MTC; document GP GPP GERAN meeting #69, Feb

11 Machine-type communications Human-type traffic Machine-type traffic Traffic direction Bi-directional Mainly uplink Message size Large/Very Large Small Traffic duration From 10s of seconds to minutes Very short (one transmission) Delay Variable Usually delay-tolerant Transmission periodicity No period, frequent sessions From 10s of minutes to hours Mobility From static to high-mobility Static, very low Information priority Usually low From low to high Amount of devices 100s per cell 1000s per cell (target ~35000) Battery lifetime Re-charge whenever a socket is available! In the order of years 11

12 Low Power Wide Area (LPWA) Objectives Battery duration ~10 years Optimized for the transmission of brief messages Low module cost (<5$) Coverage in the order of 10s of km for a cell Outdoor, indoor, deep-indoor, underground coverage High link budget with narrowband modulation Short time-to-market Support very huge number of devices (massive MTC - mmtc) End-to-end secure connectivity (application authentication) 12

13 LPWA vs Other Techonologies 13

14 Low Power Wide Area (LPWA) LPWA Technologies LoRa RPMA Ingenu ISM Band SigFox Weightless Licensed spectrum LTE-M 3GPP LTE Cat.0 3GPP: Rel. 12 NB-IOT EC-GSM-IoT 14

15 LPWA vs other technologies Billion global connection covered by different wireless networks (Machina Research, May 2015) 15

16 SigFox Ultra Narrowband Modulation (200 khz) Each message is 100 Hz, and transferred at 100/600 bps UL message Up to 12-bytes payload and takes an average 2s For a 12-byte data payload, a Sigfox frame will use 26 bytes in total Max 140 msg/day per device DL message The payload allowance in downlink messages is 8 bytes Max 4 msg/day per device Star network architecture The broadcasted message is received by any base station in the range, (3 on average) 16

17 LoRA Based on Chirp Spreading Spectrum (CSS) Exploitation of multiple gateway The network replies through the best gateway Three classes of devices Class A The device has two DL windows after a UL transmission Class B The device gets extra DL windows in addition to those of class A Class C The device can always receive in DL 17

18 Cellular IoT The idea is to provide connectivity to IoT devices via cellular networks Ad-hoc radio interfaces tailored for IoT requirements Exploitation of the same physical layer technique as current cellular technologies, to guarantee a deployment via a software update of currently deployed base stations Re-utilization of the core network Take advantage of the already available cellular coverage EC-GSM-IoT Enhancement of EGPRS LTE-M Enhancement of LTE with extended power saving modes NB-IoT New radio added tailored for low-end market 18

19 LPWA scenario 19

20 LPWA comparison U. Raza, P. Kulkarni and M. Sooriyabandara, "Low Power Wide Area Networks: An Overview," in IEEE Communications Surveys & Tutorials, vol. 19, no. 2, pp , Secondquarter H. Wang and A. O. Fapojuwo, "A Survey of Enabling Technologies of Low Power and Long Range Machine-to-Machine Communications," in IEEE Communications Surveys & Tutorials, vol. PP, no. 99, pp

21 LPWA comparison 21

22 LPWA comparison U. Raza, P. Kulkarni and M. Sooriyabandara, "Low Power Wide Area Networks: An Overview," in IEEE Communications Surveys & Tutorials, vol. 19, no. 2, pp , Secondquarter H. Wang and A. O. Fapojuwo, "A Survey of Enabling Technologies of Low Power and Long Range Machine-to-Machine Communications," in IEEE Communications Surveys & Tutorials, vol. PP, no. 99, pp

23 LPWA comparison U. Raza, P. Kulkarni and M. Sooriyabandara, "Low Power Wide Area Networks: An Overview," in IEEE Communications Surveys & Tutorials, vol. 19, no. 2, pp , Secondquarter

24 Change of business model (?) Cost of cellular IoT LTE-M and NB-IoT are software-updates of existing LTE cells In theory the cost should be low(er than LoRA) In practice, the cost of deploying cellular IoT is not clear yet Cost of the SLA SLA means somehow radio/core networks reservation/guarantee Currently, business models are mainly based on amount or speed Pay-as-you-go, periodic allowance, up to 20Mbps, etc. Amount/speed charging might mean high cost for cellular IoT Huge number of devices generating very small data traffic means many resources (control-plane traffic) to be used to control such devices Control-plane traffic does not generate revenue for the operator 24

25 Remarks The IoT is becoming real! The IoT has a wide set of use cases Precise information about density of devices, location of devices (indoor, deep indoor, underground), traffic models, etc. still not available The IoT has unique features in terms of traffic and device requirements, thus requiring ad-hoc technologies As well as it is not efficient to support human-type and machine-type traffic types with the same technology, it is not efficient to support different use cases of the IoT with the same technology Supporting the IoT via mobile networks is definitely interesting for operators, it may be interesting for customers depending to the business models adopted by the operators Cellular IoT technologies are more flexible compared to others, and their integration within 3GPP standards means efforts in guaranteeing future backward-compatible evolutions 25

26 Introduction to mobile networks Massimo Condoluci Research Associate Department of Informatics Centre for Telecommunications Research King s College London

27 IoT via cellular networks MTC Server Evolved Packet System (EPS) Evolved Packet Core (EPC) E-UTRAN BS/eNB User Equipments (UEs) 27

28 Radio Access Network (RAN) The Radio Access Network (RAN) has the role of: Connecting the UE to the CN Offering wireless resources to the UE to transfer/receive UP traffic Managing the spectrum Providing the UE with network information (e.g., broadcast information) to allow a UE to trigger a connection request Connection means: The UE is authenticated and authorized The UE will have resources for its data transfer UE enb CN ~200 ms in case of auth. ~35ms without auth. System Information Attachment: Authentication & Authorization Connection request Connection establishment Data transfer 28

29 States (EMM) EPS Mobility Management (ECM) EPS Connection Management (TRAU) Tracking Area Update 29

30 Long Term Evolution Based on OFDM OFDMA for downlink and SC-FDMA for uplink Flexible bandwidth from 1.4 to 20 MHz (i.e., from 6 to 100 resource blocks - RBs) High efficiency in terms of spectrum management 30

31 UL channels in LTE (PRACH) Physical Random Access Channel (PUSCH) Physical Uplink Shared Channel (PUCCH) Physical Uplink Control Channel 31

32 UL channels in LTE (PUSCH) Physical Uplink Shared Channel Carry UP data RBs of the PUSCH are assigned by the BS to the UE The UE performs a scheduling request procedure transmitting the buffet state report (BSR) The BS allocates the RBs (UL grant) Support power control (PRACH) Physical Random Access Channel Composed of 6RBs Preambles (pseudo-orthogonal resources) are sent on the PRACH PRACH is a periodic channel (PRACH periodicity can be varied, usually 5ms) Used to perform the random access (RA) procedure Performed by a UE if it is in idle state to switch in connected mode MTC devices are usually in idle, thus need to switch to connected mode before transmitting The RA is the key procedure in the RAN for MTC traffic 32

33 Random access (RA) procedure 4-way handshake procedure 1. Preamble transmission. Synchronization acquisition to inform the base station (BS) on the incoming request. 2. Random Access Response (RAR). The BS sends the uplink (UL) grant for the connection request. 3. Connection Request. The UE sends the effective connection request. 4. Connection resolution. The BS informs the UE about the accomplishment of the connection establishment 33

34 Random access (RA) procedure An eye into the RA: 64 preambles are defined by the network 54 preambles are reserved for contention-based RA When UEs wake up (i.e., the MTC application generates a packet to be transmitted), they wait for the first available RA opportunity to send a randomly chosen preamble If two or more UEs select the same preamble, a collision may occur Collision means that the colliding UEs have to perform a new RA attempt 54 preambles every 5ms means that the maximum PRACH has preamble/s In a ideal scenario without collisions, the PRACH can support UE/s Practically, collisions limit the capacity of PRACH A collision occurs if two or more devices select the same preamble in the same RA opportunity 34

35 Random access (RA) procedure Idle Transmission Reception 35

36 Random access (RA) procedure A collision occurs if two or more devices select the same preamble in the same RA opportunity 1000 UEs transmitting in 1s brings to 5 device per RA opportunity (RA periodicity 5ms) with a collision probability lower than 10% Capacity is an issue for the RA procedure only when considering scenarios with event-correlated transmissions A fire alarm has been reported and 1000s of devices perform the RA simultaneously (or in a very short period of time) 36

37 LTE: pros and cons Pros High data rates (reaching 100s Mbps with LTE-Advanced) Low latency (8ms to complete a HARQ process) Somehow future-proof ( easy process to switch from LTE to LTE-A) Enough capacity on the PRACH to support most (but not all!) of MTC use cases Cons High data rates does not necessarily mean high capacity (in terms of UEs simultaneously active) An LTE cell supporting 10 Mbps as a channel data rate might mean: YES: one device downloading a file with ~10Mbps throughput NO: 1000s UE simultaneously transmitting at 10 kbps! High energy consumption Cost 37

38 LTE vs LPWA 38

39 Remarks The physical layer of LTE has some interesting characteristics OFDM is very flexible, as it allows a variable composition of symbols and subcarriers Symbol duration and sub-carrier spacing can be adapted LTE has some built-in mechanisms to reduce energy consumption UEs switch to idle mode to reduce the energy consumption The energy consumption in idle mode is still high for IoT devices The integration of IoT within LTE/EPC networks allows to re-utilize the high-level procedures already defined Authentication, authorization, security Reachability of devices Mapping to QoS (please note, this doesn t necessarily mean that IoT traffic has strict QoS, it means that the operator will know the amount of traffic in the network and will be then able to perform adequate reservation of resources) 39

40 Cellular IoT Massimo Condoluci Research Associate Department of Informatics Centre for Telecommunications Research King s College London

41 From LTE to.. Cellular IoT What do we need? Lower cost of modules and installation This will allow the economy to scale Re-using available spectrum and technologies Simplified transmission/reception hardware Reducing UE capabilities (e.g., no need for 16/64-QAM) Extended coverage IoT devices can be deployed outdoor, indoor, deep indoor, underground Reducing the sub-carrier spacing (operating with smaller bandwidth increases robustness of the signal) Repetitions Lower energy consumption Difficulties (i.e., high-cost) in replacing the battery of 1000s of devices, especially for those in challenging location Please note, a duration of 10 years means that.. Once deployed, the technology needs to be available (without any change!) for.. at least 10 years! Introducing new classes of UEs with lower transmission power Allowing devices to sleep by improving the idle/connected management 41

42 LTE-M 42

43 Narrowband-IoT (NB-IoT) 43

44 Lower cost 200 khz GSM (200 khz each) LTE 200 khz LTE LTE-M has a bandwidth of 1.4 MHz (6 RBs) NB-IoT has a bandwidth of 200 khz (1 RB) LTE 6 RBs or 1 RB LTE has a bandwidth from 6 to 100 RBs (typically, 5 MHZ, i.e., 25 RBs) 44

45 Deployment scenarios 45

46 Narrow Band Extended coverage Lower bandwidth Repetitions Wide Band Same Power Noise Floor Better SNR 46

47 Extended coverage 47

48 Lower energy consumption What does it happen during the idle period? 48

49 Lower energy consumption What does it happen during the idle period? 49

50 Lower energy consumption 50

51 Lower energy consumption 51

52 Lower energy consumption 52

53 LTE-M vs NB-IoT Coverage measure as Maximum Coupling Loss Dino Flore, 3GPP standards for Internet of Things, Feb

54 Into NB-IoT Repetitions in NB-IoT are introduced to have different coverage classes Variable number of repetitions: 1, 2, 4, 8,. Up to 128 (UL) and 2048 (DL) NB-IoT defines three coverage classes Normal (outdoor, MCL 144db), Robust (outdoor, MCL 154db), Extreme (deep indoor/underground, MCL 164db) Each channel is repeated a number of times equal to the number of repetitions of the coverage class the channel is associated to Transmission parameters MTU Size: 1500B Maximum Transport Block Size: 680 DL, 1000 UL (Rel. 13) New narrowband channels (limited set compared to LTE) NPBCH, NPDCCH, NPDSCH, NPUSCH, NPRACH 48 sub-carries reserved for the NPRACH Each coverage class has its sub-carrier set and each NPRACH periodicity 54

55 Into NB-IoT L. Feltrin, A. Marri, M. Paffetti, R. Verdone, Preliminary evaluation of Nb-IoT technology and its capacity - Dependable Wireless Communications and Localization for the IoT, Graz, Austria, Sep

56 Remarks 3GPP has been actively working to meet the requirements of the IoT over mobile networks New features have been added to improve energy efficiency and to guarantee higher degrees of freedom in terms of reconfiguration New features have been added to improve the coverage Performance achieved by NB-IoT strongly depends on the deployment scenario and configuration parameters The higher the number of repetitions, the more reliable the communication but the lower the spectral efficiency Optimization between thresholds for the different coverage classes, number of repetitions, number of assigned sub-carriers and NPRACH periodicity is needed 56

57 The IoT in the mobile core network Massimo Condoluci Research Associate Department of Informatics Centre for Telecommunications Research King s College London

58 The core network in 4G The CN has the role of: Providing connectivity from/to the UE to/from external Packet Data Networks (PDNs) Allocation of IP addresses Managing the traffic of the UE according to the subscription policies Authentication and authorization of the UEs UE reachability Mobility management MTC Server Core Network (CN) Radio Access Network (RAN) 58

59 The core network in 4G Control plane (CP) User plane (UP) 59

60 The core network in 4G Mobility Management Entity (MME) key control plane element Security functions (authentication, authorization, and NAS signaling) Device mode (idle, active) management Connection/bearer management Handover Selection of the S-GW/P-GW Serving/Packet Gateway (S-GW/P- GW) User plane entities, i.e., transport data packets The S-GW is the local anchor point The P-GW interconnects to external networks 60

61 An eye into the 4G stack 61

62 An eye into the 4G stack Medium Access Control (MAC) Multiplexing/Demultiplexing of MAC SDUs from one or different logical channels onto transport blocks (TBs) Scheduling, LTE channel management HARQ Radio Link Control (RLC) Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM) Packet Data Convergence Control (PDCP) IP header compression/decompression In-sequence delivery Cipherying, integrity protection/verification Radio Resource Control (RRC) Manage the CP between the UE and the RAN (broadcast system information, paging, security, management of radio bearer) Non-access stratum (NAS) Manage the CP between the RAN and the CN Mobility management, session management, CN bearer management 62

63 An eye into the 4G stack 63

64 Bearers in 4G 64

65 (Simplified) bearer establishment procedure in 4G Msg1: Preamble Msg2: RAR Msg3: Connection Request UE1 UE2 UE3 enb MME S/PGW Connection Request Request Forward Request Ack Bearer establishment (UE1) Bearer timer Connection Request Request Forward for UE1 Request Ack Bearer establishment (UE2) Connection Request Connection Request Request Ack Request Forward Request Ack Bearer establishment (UE3) Request Forward Bearer re-setup (UE1) Connection Request Request Forward Request Ack Bearer re-setup (UE2) Assumption: there is a UP packet sent by the UE after the Request Ack 65

66 (real!) bearer establishment procedure in 4G 66

67 4G connectivity model applied to the IoT The 4G connectivity model is an always-on paradigm tailored for MBB The UP connectivity is needed to be always active UP traffic lasts from seconds to minutes (to hours in a boring day/seminar..) The long duration of UP traffic reduces the impact of CP signalling Example Let s assume there are 7 CP messages among the entities in the CN for the procedure of connection establishment On average, a HTC/MBB session has at least 10s of packets MTC has only two packets for each report One report from the UE towards the MTC server One feedback sent from the server towards the UE after the reception of the repot (optional) We need to take into account the difference between the two scenarios in the CN as we did in the radio access 67

68 5G use cases Huawei, 5G Network Architecture A high-level perspective,

69 Network slicing in 5G Huawei, 5G Network Architecture A high-level perspective,

70 The core network in 5G Control plane (CP) (Radio) Access Network User plane (UP) 70

71 The core network in 5G Access and Mobility Function (AMF) Termination of RAN CP interface (N2), NAS (N1), NAS ciphering and integrity protection Registration, connection. reachability, mobility management Support of authentication, N2, NAS signalling and mobility management for non- 3GPP access Session Management Function (SMF) Session Management e.g. Session establishment, modify and release, including tunnel maintain between UPF and AN node Selection and control of UP function Configures traffic steering at UPF to route traffic to proper destination Control part of policy enforcement and QoS User Plan Function (UPF) External PDU session point of interconnect to Data Network Packet routing & forwarding, packet inspection and UP part of Policy rule enforcement Traffic usage reporting QoS handling for user plane, e.g. packet filtering, gating, UL/DL rate enforcement 71

72 The core network in 5G Policy and Charge Function (PCF) Supports unified policy framework to govern network behaviour Provides policy rules to Control Plane function(s) to enforce them Implements a Front End to access subscription information relevant for policy decisions in a User Data Repository (UDR) Unified Data Management (UDM) User Data Repository (UDR) - User subscription data, subscription identifiers, etc. Front End (FE) - Acess subscription information stored in a UDR Application Function (AF) Interact with the 3GPP Core Network in order to provide services, e.g. Application influence on traffic routing Accessing Network Capability Exposure Authentication Server Function (AUSF) Store/provide authentication information of the UE 72

73 Access independent core N2 N11 3GPP Access AMF SMF N3 N2 N4 N1 N3IWF N3 UPF N6 Data Network HPLMN N1 NWu Y2 Non-3GPP Networks UE Untrusted Non- 3GPP Access Y1 Non-3GPP InterWorking Function (N3IWF) Support of IPsec tunnel establishment with the UE Termination of the IKEv2/IPsec protocols with the UE Termination and relying of N2 and N3 interfaces to 5G CN for CP and UP, respectively Relaying uplink/downlink control-plane NAS (N1) signalling between the UE and AMF 73

74 Access independent core N3IWF could allow LoRA, SigFox, etc. to be integrated within the 5G CN An operator can manage multiple radio access technologies (RATs) Operators could offer the IoT service via different RATs The chosen RAT can depend on: Coverage/planning (NB-IoT is urban areas, LoRA in sub-urban), use case, price/sla The integration of multi-rat increases the load in the core All traffic from all RATs will be managed by the same core Load issues, especially for the CP due to the procedures for connection establishment NB-IoT LTE-M 5G CN LoRA SigFox Fixed 74

75 URLLC and mmtc slices George Mayer, 3GPP CT Chairman, 5G Infrastructure Work in 3GPP, ETSI Summit on 5G Network Infrastructure 75

76 Design drivers for mmtc slice Features of IoT traffic to be considered/exploited Infrequent transmissions of small packets Need for a low CP signalling to improve efficiency in the network Very high device density Need for a reduction in the UP establishment/management to avoid congestion issues (a UP node can manage a few milions of bearers simultaneously) This aspect is exhacerbated when considering multi-rat scenarios Static/low mobility Some procedures in the CN can be relaxed (e.g., mobility) Features of IoT use cases Devices belonging to the same use case (e.g., gas metering) have similar traffic features (e.g., report period, message size) Generally speaking, devices can be split into groups, each one gathering devices requiring the same traffic treatment 76

77 Grouping UEs to reduce the CP signalling enb PGW UE1 Bearer UE1 UE2 UE3 UE4 Bearer UE2 Bearer UE3 Bearer UE4 4G connectivity model UE5 Bearer UE5 AN UPF UE1 UE2 G1 Bearer G1 5G connectivity UE3 UE4 G2 Bearer G2 model UE5 G3 Bearer G3 77

78 Remarks The mobile core network needs some re-design to efficiently support IoT 5G comes in handy allowing flexibility in the core A proper management of IoT traffic in the core can have multiple benefits Improving efficiency of UP resources Reducing CP signalling Supporting SLA The CN already provides support for enhanced services (e.g., multicasting) which may become of interest for the future of the IoT LoRA + NB-IoT + LTE-M + 5G CN = future-proof IoT? 78

79 Final remarks The IoT is evolving, with new use cases being enabled by the availability of IoT-oriented technologies The IoT requires operators to develop new business models/strategies (SigFox) LoRA, NB-IoT, LTE-M, etc are complementary technologies tailored for different markets NB-IoT looks to be more flexible and tunable compared to LoRA The IoT needs to be properly integrated in the CN, with ad-hoc solutions to avoid congestion What we know: We are currently designing the 5G mmtc slice taking into consideration the requirements of past/current IoT use cases Question: IoT in Disruptively different or just «enhanced»? 79

80 Thanks! Massimo Condoluci Research Associate Department of Informatics Centre for Telecommunications Research King s College London