VSAT Bandwidth Allocation

The two most common methods of bandwidth allocation associated with Maritime VSAT are dedicated services, typically Single Channel Per Carrier (SCPC), and shared services, typically based on Time Division Multiplex (TDM)/Time Division Multiple Access (TDMA). The majority of Service Providers offer maritime VSAT solutions that are based on shared IP-based VSAT solutions, but dedicated bandwidth allocation is still in use in markets with higher bandwidth requirements (such as on cruise ships and for seismic vessels regularly transmitting data).  The two bandwidth allocation methods can be defined as follows:


SCPC – Single Channel Per Carrier


  • Similar to having a private/leased line, bandwidth is not shared with any others
  • Supports high speed, enterprise-level connectivity, suitable for handling heavy data and voice traffic
  • Connection can be over-scaled to guarantee reliable connectivity even in worse-case scenarios
  • Comtech and Paradise are examples of SCPC solutions



TDM/TDMA – Time Division Multiple Access


  • An overall pool of bandwidth is shared between multiple ships
  • Bandwidth is normally allocated per ship based on traffic demand and Quality of Service (commonly referred to as QoS) agreements
  • Each ship will normally have agreed a Committed Information Rate (CIR) with its Service Provider, which assures a specified level of guaranteed bandwidth at all times
  • A Maximum Information Rate (MIR) will also be stated, which represents the size of the complete shared data pool and is the maximum level bandwidth can reach, as it becomes available
  • Typically, the actual onboard service experienced will be between the CIR and MIR indicated
  • iDirect and Newtec are typical examples of shared access solutions



Vsat Frequency Band
Maritime VSAT Purchasing Chain