Base Station Equipment

Classic Aero GES Channel Unit Subsystem

Classic Aero GES Channel Unit Subsystem

The Inmarsat Classic Aero system provides voice, low-speed data and safety communications services to end users via Aircraft Earth Stations (AESs) installed on airborne platforms and Ground Earth Stations (GESs) which provide the interface between the satellite and terrestrial networks. Classic Aero services are used by most of the world’s airlines and corporate jet operators, as well as governments for VIP aircraft, coast guard and defence agencies. 

A new generation of GESs has been installed by Inmarsat, using Square Peg Communications Inc.’s Multi-Channel Platform (MCP) to provide the modems.

The Inmarsat Classic Aero Channel Unit Subsystem (CUS) is an application of the MCP that provides up to 192 P/R/T or C-channels in a single 7U rack mount chassis. The modems implemented in the CUS are based on those in Square Peg’s Inmarsat Aeronautical Ground Data Unit (GDU), the “gold brick” reference used for type approval of AESs for operation on the Inmarsat network.

The architecture of the MCP is based on the use of a common LAN protocol for communication both within an MCP chassis and with other system elements. This provides a high degree of flexibility in configuring the system. The cards comprising a system can be distributed among multiple synchronized MCP chassis. All elements can be redundant for fault tolerance and high availability. This architecture makes it ideal for GES applications requiring fault tolerance, high availability and fully compliant performance in a compact implementation.

High availability

Hot swappable elements

Ease of maintenance

Up to 6 Channel Units (CUs) per chassis

Up to 16 transmit and 16 receive channels per CU

Integrated voice codecs

Common CU hardware and software for all channel types

Redundant Ethernet interface

Built-in dual polarization support


Channel Unit Subsystem

Enclosure19” / 7U PICMG® 2.16, rack mount
CoolingFront to back
Power suppliesN+1, 115/230V AC or 48V DC
Shelf managers

Dual redundant per PICMG® 2.9

RCMP, CLI, GUI, SNMP interfaces

Alarm dry contact relays

Ethernet switchesDual redundant 10/100 + 2 x 1G
Channel Units1 to 6 front / rear card pairs
Maximum channels per CUS96 Tx + 96 Rx

Channel Unit Functionality

Composite channels4 Tx/Rx (independently tuneable)
Composite channel bandwidth500 kHz
Bearer channels per composite channel4
Operational bearer channel typesP600/1200/10500
Test bearer typesCW, unframed, random data, random symbols
Voice codecs4.8 kb/s AMBE for C8400
9.6 kb/s LPC for C21000
Max. data channels per CU16 P-channel Tx
16 P/R/T-channel Rx
Max. C-channels per CU8 C-channel Tx/Rx

Channel Unit Interfaces

Ethernet interface10/100/1000BaseT
Auto-switching between Switch A, Switch B and front panel
Monitor and control, dataProprietary over TCP/IP
PCM samplesRTP over UDP
Tx/Rx IF frequency range50 to 90 MHz
Max. total power per Tx feed–17 dBm
Max. per-carrier Tx power–29 dBm
Tx phase noise density@ 100 Hz:   ≤ –70 dBc/Hz
@ 1 kHz:     ≤ –80 dBc/Hz
@ 10 kHz:   ≤ –90 dBc/Hz
@ 100 kHz: ≤ –100 dBc/Hz
Tx spurious< –86 dBm for carrier at –29 dBm
Tx 3rd order intermodulation< –55 dBc (2 carriers at –20 dBm)
Tx I/Q imbalancesNegligible
Typical Rx dynamic range–65 to –25 dBm
–10 dBm max total
Reference input10 MHz
Square Peg Communications Inc.
4017 Carling Avenue, Suite 200 
Ottawa, ON, Canada K2K 2A3
Tel + 1 613 271 0044
Fax+ 1 613 271 3007
Contact us for more information:

Contact us for more information:

+ 1 613 271 0044