X-band and HTS: Efficiencies

XTAR has one customer and one customer only: the military or government user. We see this as a strength, not a limitation, as everything we do is designed to ensure success for that end user. With a lot of talk recently about HTS, we wanted to explain how we compare, especially from the user’s experience. This post is second in a series of four which examines key ways in which HTS and X-band differ according to the needs and requirements of that military/government user.

High Throughput Satellites (HTS) are gaining a lot of notice in regards to efficiencies. Last September, you may recall that XTAR did some testing of our own to compare performance of our X-band capacity versus Ku-band on HTS. Results showed that X-band delivered efficiencies more than two times higher than equivalent Ku-band (HTS).

While efficiencies will vary depending on data rates transmitted, terminals utilized, and coverage areas, XTAR has provided service to a 0.4m antenna transmitting a 10 Mbps carrier at an efficiency of 1.05 bits/Hz over an entire area of interest. High Throughput Satellites would struggle to achieve these types of efficiencies. But the difference in efficiencies is vital, especially when considering the requirements of today’s military or government user.

Using small (sub-meter) antennas efficiently is key for military and government use, especially in Comms-On-The-Move or Comms-On-The-Pause situations when voice, data, imagery and HD video must be transmitted quickly and efficiently. Using X-band translates into lower costs because less bandwidth is used.

How does XTAR achieve such efficiencies? X-band satellites are spaced at least 4° apart, commercial satellites are typically spaced 2° apart. This difference in spacing allows our satellites to operate at higher uplink and downlink EIRP/Power densities. Higher allowable EIRP/Power densities at X-band allow small antennas to transmit without using spread spectrum techniques – which greatly increases bandwidth used, and therefore cost.


While HTS can provide increased data rates and lower costs, these results are best realized when it is delivered as a managed service, which includes equipment purchase and service level agreements. These managed services are often designed around commercial applications that provide the largest user base. Government/military users often have unique support requirements, require custom networks and prefer to use the equipment they already own.

When compared to HTS, X-band is more efficient at delivering capacity to today’s government and military user and is sold in the manner the government prefers to buy. HTS does have advantages, but primarily realizes those advantages in commercial applications. XTAR does not provide satellite service to commercial users. Why is this important? Check back with us next week when we answer that question.