Under a contract from ESA and Inmarsat, Square Peg supplied an MCP-based Channel Unit Subsystem (CUS) for a portable BGAN Satellite Access Station (SAS).  Square Peg also supplied the RF Subsystem (RFS) for the Micro-SAS, which leveraged the LxL links of the Inmarsat 4 satellites to provide a SAS interface via L-band.

The Square Peg equipment was integrated with a Radio Network Controller (RNC) provided by Livewire Digital, a Core Network (CN) provided by Logica and Operational Management System (OMS) provided by Gatehouse and was used to demonstrate multicast transmission over BGAN.


The L-band Micro-SAS offers many benefits, including:

  • Operable over leased bandwidth, independently of the public BGAN RAN, guaranteeing access and QoS
  • Scalable system that can support user groups from a few hundred to many thousands
  • Completely private network, independent of public circuits, and importantly, operated by the owning organisation
  • Able to be quickly deployed and commissioned in remote locations, or incorporated into a vehicle
  • Can run custom features sets for specific user groups or support advanced UT technology that may not be supported by the public Inmarsat BGAN RAN
  • Cost of ownership of a Micro-SAS is a fraction of the investment required for the public Inmarsat BGAN RAN


The architecture of the Micro-SAS is shown below, with the Square Peg CUS and RFS highlighted.

Channel Unit Subsystem

The Channel Unit Subsystem incorporates up to 3 Channel Units (CUs) with a 70 MHz IF.  Each CU supports four independently-tunable 200 kHz subbands, each of which supports up to four forward modulators and four return demodulators.

RF Unit

The RF Unit converts the 70 MHz IF of the Channel Unit to/from L-band, and provides the 10 MHz reference to the CUs.

Outdoor Unit

The Outdoor Unit (ODU) interfaces the RFU to the antenna.  It includes a 60W HPA, LNA and diplexer and provides a serial interface that allows Monitor & Control from the OMS.


The required antenna size depends upon the number of carriers that need to be transmitted simultaneously.  The Micro-SAS was supplied with either a 1.0m pole-mount or 1.2m tripod-mount antenna.



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