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Transcript
Presentation of WP2 – Scenarios and Target System Architectures FP7 ICT Objective 1.1 The Network of the Future Leader: Thales Communications & Security The research leading to these results has received funding from the European Community's Seventh Framework Programme under grant agreement n° 248993. 1 WP2 – Presentation Outline • WP2 description, organization and objectives • Highlights on the achievements 2 WP2 in LOLA WP1: Management WP3: Traffic Modeling and Measurement WP2: Scenarios and Target System Architectures Testbed 1 WP5: Integration and Demonstration WP4: PHY/MAC Algorithms WP6: Dissemination Testbed 2 Testbed 3 IP, scientific dissemination, standards 3/11 WP2 – Tasks and Objectives • WP2 Objectives (from DoW) – Define the application scenarios for low-latency wireless communications – Provide basic system architectures and requirements for the project implementation • Task 2.1: Application scenarios refinement – Define the scenarios to be targeted in the LOLA project – Select the most interesting scenarios for implementation ( link to WP5) • Task 2.2: Target System Architectures – Describe the target network topologies • Provide an initial framework for the architecture elements studied and specified in detail in the project ( output to WP3/WP4) – Describe the sources of latency in current systems • Sets the scene for the latency-reducing MAC/PHY adaptations to both LTE/LTE-A and rapidly-deployable mesh network topologies ( link to T4.1) – Forum for exchange on innovations considered in the core WPs 4 Topologies • LOLA targets two network topologies: – LTE/LTE-A cellular networks: Topology A – Rapidly deployable mesh networks: Topology B LTE-A WP2 planning, Year 1 2010 Deliverables/Milestones M 1 M 2 M 3 M 4 M 5 M 6 M 7 M 8 M 9 M 10 M 11 D2.1 Target Application Scenarios D2.2 Target System Architectures MS3: System Scenarios Defined MS4: Definition of high-level System Architectures MS3 and D2.1 accomplished in M4 and early M5 MS4 accomplished in M6 and D2.2 in M7 Officially, WP2 finalized its activities in M7, after the delivery of D2.2 M 12 WP2 Deliverable 2.1 • D2.1 Target Application Scenarios: – – – – Delivered on May 7th, 2010 Contributions from all partners, industrial partners more involved Classification of the application scenarios High level description of the application scenarios • Latency and identification of parameters influencing it • Relationship with LOLA: topology, testbed, interest – Choice of the most interesting application scenarios • From the latency analysis/improvement point of view 7 Summary of D2.1 Results Gaming Scenarios Scenario On-line Gaming Gaming on Sport Events Latency Related Latency Current Target Bottlenecks Parameters Latency Network delay User density PHY/MAC layers, Network layer (external IP), Application layer Cell capacity, User density 80 ms (Uplane, 1 way) Topol. Testb. Interest Depends on access techn. A 1, 2 ++ 40 ms A 1, 2 + 25 ms (Uplane) Summary of D2.1 Results (cont’) M2M Scenarios Scenario Auto Pilot Sensorbased Alarm or Event Detection On-line interaction for life support systems M2M Game Team Tracking Latency Bottlenecks PHY/MAC layers, Network layer (external IP), Application layer PHY/MAC layers if dedicated PHY link C-plane time for setting up the data channel PHY/MAC layers, Network layer Connection establishment, Network delay, Queue management at application layer Related Parameters Cell capacity, Handover, Network density Latency Target Current Latency Topol. Testb. Interest 30 ms (Uplane) 46 ms A 1, 2 + Power consumption, Network capacity, Reliability No particular or outstanding influencing parameter User density, Cell capacity, Cell load, Handover Link outage, Robustness, Mobility 2-12 ms (1 way, U- and Cplanes) Depends on technology A, B 1, 2 ++ < 500 ms NA A 1 + 55 ms (Uplane) 75 ms A 1, 2 ++ 1s (U- and Cplanes) 1 s – 10 s B 3 + Summary of D2.1 Results (cont’) Human remote control, alarm and event detection Scenario Remote Medicine Remote Control Ad hoc Public Safety Communications Latency Bottlenecks PHY/MAC layers, Network layer (external IP), Application layer Related Parameters User density, Handover, Throughput (for video) PHY/MAC layers (multihop links, relays), Network layer PHY/MAC layers (multihop links, relays, priority management) Throughput, Reliability Throughput, Reliability Latency Target Current Latency Topol. Testb. Interest 200 ms (U-plane) > 200 ms A 1, 2 + < 100 ms (U-plane + displaying) Hundreds of ms A B 1, 2 3 ++ 300 ms – 1 s (call setup) < 500 ms (voice) Depends on topology and service B 3 + Online Gaming Application • Use case: First Person Shooter (FPS): – FPS is recognized as one of the most latency critical type of online gaming, because of high precision and tight deadline – High reactivity of the system to guarantee high reactivity of the game – Different architectures • Peer-to-peer, local server, centralized servers – Possible high user density – Target latency: < 80 ms, one way – Target topology: A eNodeB Evolved Packet Core (EPC) S-GW P-GW UE MME eNodeB Server Internet Gaming Server M2M Game • Use case: virtual bike race Biker – The opponents are on different locations, they race one against the other thanks to the measurements taken by the sensors – High reactivity of the system for guaranteeing high reactivity of the game, especially in the photo-finish phase – Possible high user density, high cell load, different cell capacities, presence of hand over – Target latency: < 55 ms, one way, precision required for photo-finish phase – Target topology: A S-GW P-GW MME Biker eNodeB eNodeB Evolved Packet Core (EPC) eNodeB S-GW P-GW EPC MME Server Internet Gaming Server Sensor-based Applications • A variety of applications are possible or imaginable: – Use case 1: Control of critical structures, e.g. oil and gas transportations, electricity infrastructure... • Typically use dedicated systems to guarantee very low latency, especially for critical infrastructures or data • In certain applications, we could think to replace the dedicated link with a LTE/LTE-A link – Use case 2: video surveillance of a site • Topology A could be used for a fixed need (e.g. stadium) • Topology B for a temporary need – High reactivity of the system for guaranteeing high reactivity of the game, especially in the photo-finish phase – Related parameters highly depends on the application, as well as the latency targets Mesh node Remote control • Use case: control of unmanned ground or aerial vehicles (UGV/UAV) for security/control/support/maintenance purposes – Activity in dangerous places (maintenance in nuclear plants during accidents), support to security/rescue operations – Short command cycle for command and control of the UGV/UAV or for the control of its sensors (e.g. steerable video cameras) – Possible high throughput required, reliability is required – Target latency: < 100 ms, two-ways – Target topology: A or B Mesh node UGV UGV UGV Remote control center Mesh node Internet Local control center WP2 Deliverable 2.2 • D2.2 Target Network Architectures: – Delivered on July 20th, 2010 – Contributions from all partners – Description of the target network architectures for Topology A and B • A historical evolution of 3GPP architecture is provided too – Description of the current protocol stacks in both topologies – Definitions of latency – First latency estimations • Latency budgets – Identification of latency sources for both topologies 15 Topology A Architecture • The generic LTE architecture is shown above, then it can be declined in different ways according to the application Topology A Architecture applied to M2M • Below we present the generic Topology A architecture coupled with a general M2M eco-system – Different architectural configurations can be used adapted to the specific needs of the application Topology A Protocol Stack • Inherited from LTE and oriented towards LTE-Advanced • The project works in parallel with LTE Rel-10 definition 18 Topology B Architecture • Rapidly deployable mesh networks: – Only small-medium deployment size are targeted – Built on the CHORIST mesh network Cluster-Head Mesh Router Edge Router Other Access Technology Communication 1 (example) Communication 2 (example) 19 Topology B Protocol Stack • Inherited from CHORIST (OFDMA) • Convergence towards LTE stack (frame, low level signalling) – Addition of mesh functionalities – Synergy/convergence towards cellular networks 20 Definition of Latency • User-plane (U-plane) latency: – Common to both topologies – One-way transit time between an SDU packet being available at the IP layer in the user terminal and the availability of this packet (PDU) at the IP layer in a remote node or vice versa • Control-plane (C-plane) latency (connection setup latency): – Transition time from one terminal state to another plus the time taken by the first data packet to successfully reach the receiver reference point – Terminal states in two topologies are not exactly the same (“Active” and “Standby” are replaced by “Connected” and “Associated”) Topology A Latency Estimations for Top A DELAY COMPONENTS DELAY VALUE Transmission time uplink + downlink 2 ms Buffering time (0.5 transmission time) × 2 × 0.5 × 1 ms = 1 ms Retransmissions 10% 2 × 0.1 × 8 ms = 1.6 ms Uplink scheduling request 0.5 × 5 ms = 2.5 ms Uplink scheduling grant 4 ms UE delay estimated 4 ms eNodeB delay estimated 4 ms Core network 1 ms PDF: GPRS [%] PDF: HSDPA [%] PDF: EDGE [%] PDF: HSUPA [%] PDF: 3G-R99 [%] 80.00% 70.00% 60.00% 20.00% 10.00% Latancy estimations in LTE Topology Example of distribution of latancy in GSM and 3G Network 22 1140< T [ms] <1160 1080< T [ms] <1100 1020< T [ms] <1040 960< T [ms] <980 900< T [ms] <920 840< T [ms] <860 780< T [ms] <800 720< T [ms] <740 660< T [ms] <680 600< T [ms] <620 540< T [ms] <560 480< T [ms] <500 420< T [ms] <440 360< T [ms] <380 300< T [ms] <320 240< T [ms] <260 20.1 ms 180< T [ms] <200 0.00% 120< T [ms] <140 Total delay with scheduling 13.6 ms 30.00% 60< T [ms] <80 pre- 40.00% 0< T [ms] <20 Total delay with allocated resources 50.00% Latency Budgets for Top A • LTE C-plane latency – From IDLE to ACTIVE – FDD assumed – Less than 100 ms – 61 ms + 2*Ts1c + Ts1u – Ts1c: S1-C Transfer delay (2 ms – 15 ms) – Ts1u: S1-U Transfer delay (1 ms – 15 ms) 23 Latency Budgets for Top A • LTE U-plane latency: – – – – Specifications require U-plane latency below 5 ms within RAN LTE_ACTIVE, unloaded conditions and small IP packet assumed Error probability of the 1st HARQ retransmission, p = 30% S1 transfer delay = 1 ms (200 km, 200000 km/s in copper cables) – sGW processing delay = 0.5 ms (assumption) – One-way U-plane latency = 1 + 1.5 + 1 +p*5 + 1 + 0.5 = 6.5 ms 24 Sources of Latency for Top A • C-plane latency major contributions: – eNodeB / UE L1/L2/L3 procedures – Transmission delay – Retransmissions for reliable transfer • U-plane latency: – UE processing delay (header compression, ciphering and RLC/MAC processing) – Resource allocation and physical layer transmission delay: transmission L1 processing, Transmission Time Interval (TTI) subframe alignment and receiver L1 processing – HARQ retransmission delays – eNodeB processing delay (RLC/MAC processing) – eNodeB/ s-GW delay on S1 interface, between the eNodeB and the serving gateway s-GW of the mobile management entity – s-GW processing delay: header decompression and ciphering • Actual delay in a real system will be dependent on system load and radio propagation conditions Sources of Latency for Top A • LOLA simulations in a single-cell LTE scenario – To investigate influence on latency by the following parameters: • Traffic load • Packet segmentation • Probability Density Functions (PDF) for the packet size and inter-arrival time are same for all traffic source • Traffic load increased by increasing the number of users in the cell Latency Estimations for Top B • First indication of the round trip time (RTT) in a simple measurement setting – PING RTT measured – Packet size and inter-departure time was varied – RTT can be optimized if the packet size is a multiple of the RLC payload datat unit and the total data rate remains below the maximum access layer data rate – Strong impact of the number of hops Scenario 1-hop (MR CH) 2-hop (MR – CH – MR) Data Rate 1 10 100 1 1 10 100 1 kbps kbps kbps Mbps kbps kbps kbps Mbps Average RTT (ms) 55.41 62.56 34.65 40.29 89.23 86.69 70.68 147.70 Measurement setup Maximum RTT (ms) 128.68 194.55 53.97 50.38 121.13 99.28 85.46 209.12 Minimum RTT (ms) 38.62 29.60 27.65 26.87 72.99 67.06 53.80 98.3527 Latency Budgets for Top B • U-plane latency budget • Ideal assumptions – – – – Small IP packets (0 bit payload) Unloaded conditions, TDD frame HARQ not used, ARQ used Frame structure inherited from CHORIST • Evaluations: – For the one-hop scenario: RTTMR,IP,ARQ = RTTCH,IP,ARQ = 23.62 ms + 4DIP2PDCP – For the two-hops scenario: RTT2hops,IP,ARQ = 47.24 ms + 8DIP2PDCP. – DIP2PDCP: delay for passing IP packet from PDCP (L2) to IP 28 Sources of Latency for Top B • The processing time of the mesh node has a strong impact, reducing the Transmission Time Interval of the frame could be beneficial • ARQ retransmissions delays – In CHORIST HARQ was not present and ARQ was the only recovery mechanism – Inserting HARQ at Layer 2 should increase robustness and improve latency • Fragmentation and concatenation of the packets at Radio Link Control (RLC) level can have a big impact on latency • Routing at IP level – For small deployment routing time could be lowered through forwarding techniques at access layer • The number of hops – Direct link communications, without passing though the cluster head can be beneficial – Cooperative transmission procedure can also be beneficial 29 Conclusions • WP2 achieved: – Definition of application scenarios for low-latency wireless communications and a selection of mostpromising scenarios for LOLA implementation – Description of basic system architectures and requirements, both for Topology A (LTE/LTE-A) and Topology B (wireless mesh network) – Definition of the concept of latency and of latency budgets – Localization of latency sources