Networks Without Barriers DVB-RCS Mesh Networks for Data, VoIP and GSM Karl Petter Sundby, Sr. System Engineer STM Norway June 2008 www.stmi.com
Adapting DVB-RCS to the Bent-pipe Mesh Environment Key Challenges Distinguishing Star vs. Mesh Links: In measuring & managing link performance For capacity requests by VSATs In the Terminal Burst Time Plan (TBPT ) use of TBTP also for controlling reception Concurrent TDMA burst reception Full-mesh or subnet limited IP routing Efficiency for thin route mesh traffic Mesh Logical Diagram and Key Elements HQ Office Internet PSTN Hub & Gateway Mesh VSAT Mesh VSAT Mesh VSAT PSTN Mesh Gateway Major Office Mesh Gateway The mesh link is a logical link concept, it may employ various TDMA Carriers. A given TDMA Carrier may be shared by both mesh & star links 2
Key Enabling Technologies for Mesh Networking Wideband Burst Demodulators for mesh VSATs Low-cost, 36 MHz wide, 4 concurrent TDMA bursts received Reducing burst blocking probability to <10-5 (vs. > 5% for single) Extended NCC functionality Capable of 1000 s of active mesh VSATs and 10,000 s of mesh routes Extended terminal processing and queuing logic TCP Acceleration on all active mesh links Applying seven (7) QoS Groups on all active mesh links Local routing table for all active mesh links Efficient processing of capacity requests for all active mesh links Time-out on inactive mesh links; Reports on degraded mesh links 3
Mesh Functional Diagram and Key Elements Hub need not receive all TDMA Carriers (if some carriers are dedicated to mesh) PSTN or GSM DVB-S2 Forward Link Return & Mesh Links can dynamically share all TDMA Carriers, If desired Mesh Gateways with multiple burst transmitters and wide-band burst receivers Internet or Intranet SatLink Hub Mesh VSATs with wide-band burst receivers PSTN Major Office All Mesh VSATs & Gateways can receive the TDMA transmissions of all others, plus the DVB-S2 forward link (if within same beam footprint) 4
Mesh Applications Dedicated Hub Applications: Large, general purpose Govt. / Corp networks (voice, video and data all over IP) Large rural telephony networks (sold to telecom operators) Shared Hub (i.e., Teleport) Applications: Bandwidth flexible private lines (point-to-point) for any media Small video conferencing mesh networks SCADA applications with multiple control centers Smaller general purpose Govt. / Corp. networks Smaller rural telephony applications (10 to 100 sites) With use of Mesh Gateways for all larger sites 5
VoIP in the Mesh The Thin Route Efficiency Challenge VoIP mesh networks with 1000 s of VSATs (e.g. for rural telephony solution) Higher packet latency for low traffic on mesh links low slot rate for one voice call on link (no multiplexing) Low rate voice codec need minimum latency in VSAT inherent high voice codec latency For reasonable bandwidth efficiency this necessitates: Encapsulation and IP stack (i.e. IP, UDP, RTP) header compression Consideration of a smaller TDMA burst size Facilitates higher burst frequency Improved performance for these short bursts 6
GSM in the Mesh Thin & Thick Routes GSM over IP becoming common for back-haul Thin Route efficiency requires powerful header compression whereas Thick Route can also benefit from multiple voice samples per IP packet GSM has a centralized architecture (all traffic to MSC) Local switching (at VSAT) possible if BSC is co-located with BTS GSM over Mesh not possible unless MSC is also co-located with VSAT This is not viable since MSC is large & expensive Blend of GSM and VoIP (with SIP routing) can offer mesh networking for rural GSM but requires some administrative enhancements Solutions can be further adapted for future 3G/4G cellular 7
Mesh GSM Diagram Single Hop between Towns MF-TDMA Optimized VoIP & A over IP Optimized VoIP PRI, SS7 or R2 PSTN Incoming & Outgoing Calls from/to PSTN E1s Voice over IP SatLink MF-TDMA Bandwidth-on-Demand with Voice QoS GSM BSS VoIP SIP Gateways SIP A SatLink Carrier-Class Hub System or Mesh Gateway GSM Handsets MSC 8
Example GSM Tri-Sector Configurations BTS BTS BTS BTS BTS BTS Abis over IP to BSC (at hub) LAN Switch Abis over IP SatLink 1910 or 1000 IDU A over IP to MSC (at hub) VoIP within mesh BSC & VoIP Media Gateway A over IP VoIP/SIP for Mesh Links SatLink 1910 IDU BSCs reside at hub no local switching Local BSC enables local call switching VoIP/SIP enable Mesh GSM calls 9
SCADA in the Mesh Deployed as one of several mesh subnets controlled by a shared satellite hub Shares resources with other applications like other SCADA networks Benefits from statistical multiplexing Can be given precedence relative to other traffic Supported by high efficiency volume oriented BoD resource control Suits traffic with low sensitivity to delay jitter 10
Conclusions Extension of DVB-RCS to mesh is straight forward, but with some technical challenges STM has implemented DVB-RCS mesh capabilities Mesh networks have variety of useful applications, but voice networking is the major mesh application especially for rural telephony VoIP over mesh can be made very efficient GSM over mesh poses further challenges, but they are not insurmountable Solutions for GSM over mesh can be used as basis for voice networking in 3G/4G cellular 11
Networks Without Barriers Questions? SatLink 1910 Meshed Terminal SatLink Meshed Gateway www.stmi.com STM Group, Inc. 2 Faraday Irvine, CA, 92618 USA STM Norway AS Vollsveien 21 N-1366 Lysaker, Norway