A CONTROL FRAMEWORK FOR ADAPTIVE CAPACITY ALLOCATION IN MOBILE DVB-RCS

Transcription

1 A CONTROL FRAMEWORK FOR ADAPTIVE CAPACITY ALLOCATION IN MOBILE DVB-RCS JA-2330 Integration Meeting Nedo Celandroni*, Franco Davoli, Erina Ferro*, Alberto Gotta*, Raffaello Secchi* *ISTI-CNR, Area della Ricerca del C.N.R., Via Moruzzi 1, I Pisa, Italy DIST-University of Genoa and CNIT (Italian National Consortium for Telecommunications), Italy

2 MUltimedia MObile Bandwidth ALlocation (MUMOBAL) architecture Class-based Dynamic Bandwidth Allocation One portion of bandwidth for each typology of traffic and moving boundaries between bandwidth portions In each portion, the Network Control Centre (NCC) assigns bandwidth to the relevant traffic classes, by taking into account their QoS requirements and traffic characteristics Collision free Optimal controller: Optimal DBA Control Algorithm for Service Level Agreement Collision free DAMA: Rate Based Dynamic Capacity Volume Based Dynamic Capacity FCA option Contention access DSA: Contention-based MAC EF traffic: Voice, video & Real Time applications with QoS requirements Large volume AF & BE traffic: web applications, video streaming, interactive and peer-to-peer, etc... Small volume BE traffic: web-browsing, , signaling, etc Collision free Optimal Controller Collision free DAMA Contention access DSA Collision free Optimal Controller Collision free DAMA Contention access DSA

3 Report of recent activities Simulation of LMS channel model (ESA) at packet level and derivation a packet level model Evaluation of performance of error correction techniques to counteract lossy periods Comparison of different access techniques Random Access: Diversity Slotted Aloha Deterministic Access: Demand Assignment Multiple Access Trade-off between bandwidth cost and completion time as concerns TCP performance

4 DVB-RCS/S2 for mobile users Simulation (Matlab/Simulink) of DVB-RCS/S2 chain with ESA channel model In each channel state (LoS, Shadowed, Blocked) Average Packet Error Rate Average Burst Error Length Traces Based on simulation results, we derived a mobile channel description at packet level 3-state Discrete Markov Chain 2-state Discrete Markov Chain (ON-OFF)

5 DVB-RCS for mobile users (uplink) PER (DVB packets) Mobile channel in LoS is substantially different from AWGN Significant differences in PER between LoS and Shadow states Minor differences (less than 1 db) in PER for each state in different environments E c /N 0

6 DVB-S2 for mobile users (downlink) PER (LDPC blocks) PER curves very steep in LoS environment Significant differences in PER between LoS and Shadow states PER curves strongly dependent from modcod E c /N 0

7 Case study: mobile user acts as an FTP client UPLINK: TDMA/DSA DOWNLINK: TDM Highway Rural LMS channel parameters Environment T NB 3.02 s 2.03 s T BL 0.36 s 0.55 s Blocking prob ON/OFF mobile channel HUB station SERVER Terrestrial Segment (50 ms) CLIENT Internet Gateway RTT=600 ms, Segment size=1416b (equivalent to 8 DVB packets), Frame size=20 ms, TCP/Sack

8 Short-lived connections (highway) D V B p a ckets/co n n e ctio n Average Uplink Bandwidth Cost DSA 10% DSA 20% TDMA 1f/s TDMA 2f/s TDMA 4f/s TDMA 8f/s C o m p le tio n T im e [s ] Average Completion Time DSA 10% DSA 20% TDMA 1f/s TDMA 2f/s TDMA 4f/s TDMA 8f/s Connection Length [kb] Connection Length [kb]

9 Long-lived connections (highway) DVB packets/connection Bandwidth Cost DSA TDMA 10% 20% 1 f/s 2 f/s 4 f/s 8 f/s d u ra tio n [s ] Completion Time DSA TDMA 10% 20% 1 f/s 2 f/s 4 f/s 8 f/s DSA may not be suitable for long-lived connections in highway DSA 10% is outperformed by DAMA 1f/s in both duration and cost, while DSA 20% has a duration very close to DAMA 4f/s, but the latter exhibits a significantly lower cost

10 Considerations on DAMA/DSA comparison 1. The smaller the size of file transfer, the higher the gain in terms of bandwidth and connection duration of DSA with respect to DAMA in bandwidth expenditure 2. DSA cost depends on data successfully delivered only, thus it is less sensible to changes in the channel blocking probability 3. DSA is not convenient for long-lived connections in both environments (limited to our investigations) The choice of system parameters is a matter of more complex investigations (e.g. the mobile acts as server). Nevertheless, once the parameters have been selected, cost diagrams will be used to evaluate convenience thresholds. For instance In case DAMA 4f/s and DSA10% are selected as the most convenient options, the threshold file size is about 17 kb and 65 kb for highway and rural environments, respectively

11 Main objectives MUMOBAL objective is to design an MF- TDMA access scheme based on DVB-S2 (RCS) suitable to support various classes of users (fixed, large and small mobile) with different classes of traffic (streaming, TCP, etc.)

12 Future plans Analysis of the case in which the mobile user acts as a server: Operating the choice of the target throughput in DSA and the minimum assignment in DAMA For the server case, in order to obviate to the collisions effect in DSA, a packet level FEC might be necessary Completion of the analysis of the application of PLFEC and inter-leaver to streaming traffic (DVB-S2 and RCS) Review of the DAMA design to optimize a TCP connection in a mobile environment Extension of the Ka-band paper to a journal version