What is a High-Throughput Satellite?

What is HTS or a High-Throughput Satellite?

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- everything RF

Mar 3, 2021

High-throughput Satellite or HTS is a communication satellite that provides more throughput than conventional communication satellites (Fixed Satellite Service). Higher-throughput refers to a significant increase in capacity when using the same amount of orbital spectrum. The increase in capacity typically ranges from 2 to more than 100 times as much capacity as the classic FSS (Fixed Satellite Service). This significantly reduces the cost per bit.

For example, ViaSat-1 which was launched in 2011 was one of the first High Throughput Satellites that had with a total capacity in excess of 140 Gbit/s. It practically had more capacity than all other commercial communications satellites over North America combined. ViaSat-1 held the Guinness record for the world's highest capacity communications satellite, which offered more than 100 times the capacity offered by a conventional FSS satellite.

ViaSat-1 - HTS Satellite Launched in 2011

How is this High-Throughput achieved?

To gain this significant increase in capacity an HTS leverages a high-level of frequency re-use and spot beam technology. Traditional satellite technology utilizes a broad single beam or a few beams which cover large areas that are sometimes thousands of kilometers. Spot beam technology uses multiple narrow beams which allow it to re-use the same frequency band. Now, we can already figure out that the key difference between FSS and HTS is the size of their beams on the ground. 

FSS beams are very wide-spread and at times cover an entire continent, and therefore, along with the beam the available RF power also gets spread across a wide geography. Thus, the obtained spectral efficiency is low. HTS, on the other hand, uses multiple “spot beams” with smaller footprints, each covering a smaller region. Hence, each of them will provide a separate signal and thus the overall system will have much better spectral efficiency, and in turn support higher speeds.

HTS almost exclusively boasts over frequency re-use, lets take a clear idea of the concept. We know, a traditional satellite is based on wide beam, i.e., it uses a single frequency to cover an entire geographic region. That frequency for that region will remain unusable for the satellite or it might cause interference. Hence, the given satellite can use a frequency only once. By contrast in an HTS approach, instead of wide beams multiple spot beams are used that cover smaller areas. If the frequency used in one spot is far enough from another spot, several beams can reuse the same frequency band. With no question of interference, the same frequency can serve two or more separate geographies and sets of clients. This frequency re-use along with multiple spot-beam boosts the capacity of the given satellite system for a given amount of frequency band allocated to the system.

The primary user requirement of HTS is Broadband Internet access service (point-to-point) to regions unserved or underserved by terrestrial technologies. In regions where high-quality broadband through our ground infrastructure is not available or maybe not possible, satellite technology is the most appropriate solution. Now, HTS platforms that were originally aimed to serve the consumer market only are branching out to offer their services in government and enterprise markets as well. Basic connectivity in remote areas is also being covered under satellite technology. Such satellites are also suitable for cellular backhaul; they provide high-capacity links to support isolated base stations of terrestrial networks that too at highly reduced cost per bit. HTS can also serve point-to-multipoint applications and even broadcast services such as DTH distribution to relatively small geographic areas served by a single spot beam.

Note: In the last 10 years, the majority of high-throughput satellites were operated only in the Ka-band, and hence, many people feel that HTS only operates in the Ka-band. However, this is not true, HTS can be deployed in many spectrum bands. Though they are mainly found in the Ku-band (lower) and the Ka-band (higher) bands.