S-UMTS Simulator Description

The S-UMTS simulator is implemented on top of an open-source Network Simulator 3 (ns-3) and reuses the Satellite Network Simulator 3 (SNS3) architecture. S-UMTS simulator models a full interactive multi-spot beam satellite network with a geostationary satellite and transparent star (bent-pipe) payload. By its nature, ns-3 is an event-driven simulator proceeding in non-uniform time steps. In contrast to the clock-driven simulations, the testbed reflects better the state-machine nature of communication equipment.

Broadband Global Area Network (BGAN) is a mobile satellite communications service by Inmarsat, which is providing reliable, cost-effective global broadband data and voice using compact, lightweight portable terminals. ETSI standard TS 102 744 for the Satellite Universal Mobile Telecommunications System (S-UMTS) is grounded on the proprietary Inmarsat air interface covering the protocol stack under the transport layer. S-UMTS system simulator models the S-UMTS Family SL protocol stack and related geostationary satellite scenario. The simulator can be used to estimate the suitability of S- UMTS/BGAN air interface protocols for different SatCom and service use cases.

Similar to the SNS3, the architecture consists of three types of nodes: a radio network controller (RNC), a bent-pipe transparent satellite, and User Equipment (UE). The simulator modelling focuses on the Bearer Connection (BCn) and Bearer Control (BCt) protocol layers. The physical layer phenomena is abstracted to cover the link quality measurements for the upper layers and per-packet accept/reject based on ModCod robustness. In addition, the ns-3 environment provides the higher layer protocols to model data sources and logging statistics.

The S-UMTS simulator handles uplink/downlink data transmission and link adaptation for multiple users sharing the channel. In this context, the main features are: 

1. UE scheduling using granular time-frequency slots

2. Reserved (dedicated) or contention (random) access 

3. Bit level modelling of the signaling data units (e.g., to convey status and return link schedule information)

4. Connection layer packet segmentation and reassembly operation with both unacknowledged and acknowledged mode operation

In addition, the simulator supports NavSim traces by University of Salzburg for UE mobility and data traffic. The simulator outcome includes statistics for SINR, throughput, link delay, ModCod adaptation, and scheduler  bandwidth utilization. 

References:

1. Network Simulator 3, http://www.nsnam.org

2. J. Puttonen at al., “Satellite Model for Network Simulator 3,” in International Conference onSimulation Tools and Techniques (SIMUTools), Lisbon, Portugal, 2014.

3. ETSI TS 102 744, Satellite Earth Stations and Systems (SES); Family SL Satellite Radio Interface, Parts 1-4.