Envistacom White Paper

By Tom Cox

May 2014

Comparative Analysis of VSATs and Deployable Earth Terminals in a Dynamic, Growing High-Data Environment

Envistacom White Paper

Comparative Analysis of VSATs and Deployable Earth Terminals | © Envistacom 2014. All rights reserved. | Page 2

This paper serves to identify the key variables in making a good decision on the type,

size, and robustness of a deployable communications platform.

Overview Providing satellite communications solutions for a dynamic

enterprise can be a significant challenge. Engineers continuously

manage various trade-offs and analyses to find the correct

solution for an environment where the bandwidth needs are in a

continuous state of flux.

This paper serves to identify the key variables in making a good

decision on the type, size, and robustness of a deployable

communications platform. Our aim is to provide consumers of

satellite communications in a large, growing C2 environment with

a primer to choose the best solution.

Generally speaking, there are three classes of satellite

communications solutions:

1. Very Small Aperture Terminal (VSAT)

2. Deployable Earth Terminal Terminal

3. Teleport

Each class provides a different level of communications

infrastructure for the local Enterprise as well as the global

Enterprise networks. This paper will discuss the tradeoffs of

VSATs and Deployable Earth Terminals specifically in the case

of the Balad Airbase Network.

Assumptions:

Location - Balad, Iraq

Throughput Requirement - 10MBPS up / 10MBPS down

Committed Information Rate - 100%

Contention Ratio - 1:1

Frequency Band - Ku-Band


Very Small Aperture Terminals (VSATs) With more than 40 million terminals deployed across the globe,

VSATs represent the most common and least expensive solution

for deployable communications. A VSAT typically includes a

small antenna in the 0.5 - 3.0 meter range and a transmitter with

two to 20 Watts of output power.

VSATs provide consumer and enterprise customers with up to 4

MBPS uplink throughput and 10 MBPS of downlink throughput.

More typically, VSATs provide up to 1 MBPS up and 4-6 MBPS

down. They are easy to install and relatively inexpensive,

typically costing between $15K - $200K per terminal depending

on throughput and ruggedness.

The biggest advantage of a VSAT is its size and simplicity. VSATs

install quickly and have very few active components. They can

be shipped commercially and typically weigh less than 200 lbs.

Once manually aligned to the satellite, they operate

autonomously and are easy to manage.

The biggest disadvantages of VSATs are their reliability, cost of

bandwidth, and actual throughput. VSATs are single-threaded

systems, so if a component fails, the entire network fails. Satellite

operators treat VSATs as “disadvantaged terminals” because

they are power-limited. Remote terminals have to transmit with

more power, which costs end users more money per megahertz

of bandwidth. VSATs have a limited amount of power to transmit

with as well, so they can only transmit a limited amount of data.

VSATs typically operate in large networks that have high

contention ratios. A typical VSAT will have a contention ratio of

10:1, meaning at peak usage times, the VSAT may only be able to

use 1/10th of the maximum throughput. Contention ratios can be

as high as 100:1 in peak load times, meaning that users may be

forced to a total aggregated circuit speed of 32-64KBPS,

resulting in lost data or dropped VoIP calls. Paying for a lower

contention ratio becomes prohibitively expensive and may

require a dedicated circuit. A dedicated circuit on a VSAT is the

least cost-effective satellite option.

Figure 1. Typical VSAT Terminal


Deployable Earth Terminals Deployable Earth Terminal terminals are in between VSATs and

teleports. They represent the class of terminals that provide the

greatest flexibility in enterprise communications solutions. The

US military and other Foreign Military Sales (FMS) programs have

made extensive use of deployable earth terminals - more than

100 systems - throughout the Southwest Asia region in support of

Command & Control (C2) operations at all bases in the region.

Balad, AB had seven (7) such deployable terminals providing

inter-theater and global reach back connectivity during US

operation of the airbase. VSATs are typically used for smaller,

temporary tactical C2 operations as well as Morale, Welfare and

Recreation (MWR) services for the stationed soldiers, civilians and

contractors.

A Deployable Earth Terminal typically includes a medium-sized

antenna in the 3.0 - 7.0 meter range. These terminals require a

greater upfront investment in ground equipment than a VSAT,

and can cost anywhere from $500K up to $2M depending on

the level of reliability, capacity, transportability, and ruggedness.

The biggest advantages of a Deployable Earth Terminals are

their flexibility, reliability, and expandable capacity. Deployable

Earth Terminals can be shipped commercially and can be fully

operational within 8 hours of delivery. They are fully redundant

systems meaning they rarely fail and they can support up to 100

MBPS up / 200 MBPS down of throughput.

Deployable terminals also have a lower cost per megahertz of

bandwidth than VSATs. Typically VSATs are able to transmit 1

MBPS per 1 MHz of bandwidth, whereas deployable earth

terminals can transmit 2 MBPS per 1 MHz of bandwidth,

representing a 50% recurring bandwidth cost savings.

Deployable earth terminals typically operate dedicated circuits

and do not deal with contention ratios or degraded service

issues at peak usage times. This guarantees 100% of the

satellite bandwidth is available 100% of the time. The major

disadvantage of a deployable earth terminal is the upfront cost

of the terminal.

A Deployable Earth Terminal may not be

appropriate for a use case where less than 1MBPS up / 4MBPS down of

throughput is required, or if the users can tolerate outages or bandwidth

throttling during peak usage times of the day.

Figure 2. Deployable Earth Terminal


Terminal Size VSAT antennas are typically between 0.5M and 2.4M in aperture

diameter, whereas deployable earth terminals range in size from

3.0M to 7.0M. The larger surface area of the deployable earth

terminal reflector allows for far greater signal gain, and can

transmit far more power.

A 1.0M (40”) VSAT antenna provides 3.142 m2 of surface area,

which translates to 40dBi of passive gain. A 3.7M deployable

earth terminal antenna provides 43.0 m2 of surface area (1300%

increase), which translates to 51dBi of gain. This passive gain

difference is critical in determining several factors, including the

cost of bandwidth, maximum transmit bandwidth, susceptibility to

weather (rain fade), and how far out to the edge of a satellite

beam the terminal can be located.

At an aperture size of 3.3M, satellite earth terminals have enough

receive sensitivity (gain) to access the noise floor of most

commercial satellites. This means that a 3.3M antenna operates

at the same signal-to-noise ratio as a far larger teleport antenna.

Any antenna smaller than 3.3M will have a degraded signal-to-

noise ratio, meaning that for every dB of lost gain, the

transmitting station must transmit 1 dB more in power to close the

satellite link to the VSAT terminal.

Maximum Data Rates At the high end, VSATs have a maximum data rate throughput of

4 MBPS up and 10 MBPS down. More typical VSATs that are

provided by commercial service providers - such as the one

currently fielded at the Balad Airbase - provide 1 MBPS up and 4-

6 MBPS down with a contention ratio of 10:1. Therefore, at peak

usage times, this leaves the remote user with as little as

128KBPS uplink and 640KBPS downlink for their entire user

population.

Additionally if the end user wishes to increase the throughput

beyond these levels, a new larger terminal will be required to

upgrade the link. Deployable earth terminals can provide as

much as 100 MBPS up and 200 MBPS down, and with newer

satellite technology called “High Throughput Satellites” (such as

Inmarsat GX and Viasat-1), can potentially even provide up to 1

Figure 3. Comparison of aperture size


GBPS of throughput in both directions. Deployable earth

terminals typically operate dedicated circuits resulting in a

guaranteed Committed Information Rate (CIR) of 100%, or a

contention ratio of 1:1. This means the throughput will never drop

below the minimum CIR delivering higher performance and

reliability for voice, video, and data services.

Cost of Bandwidth VSATs provide an inexpensive communications solution in high-

contention networks, however as the user increases the

minimum Committed Information Rate (CIR), the cost increases

significantly. If a VSAT is used to deliver a dedicated circuit (100%

CIR, 1:1 contention ratio), the cost of bandwidth per megahertz is

typically 25-30% higher than a deployable earth terminal. This is

because the distant end teleport must transmit a more powerful

carrier, and the satellite uses more resources to provide the link.

Additionally, VSATs can typically provide 1 MBPS of data for

every 1 MHz of bandwidth, whereas a deployable earth terminal

can typically provide 2 MBPS of data for every 1 MHz of

bandwidth. Since satellite providers charge based on power and

bandwidth, this means the cost of bandwidth for a deployable

earth terminal is substantially lower than that of a VSAT.

Scalability VSATs are limited in their throughput, therefore in order to scale

the network service beyond their 1 MBPS up / 4-6 MBPS down

capacity, a second VSAT or a larger terminal is needed. If

additional modems or baseband gear is needed, these must be

stored in additional transit cases or inside a customer-provided

building within 100 feet of the VSAT antenna.

Deployable earth terminals are miniature teleports and have

anywhere from 3 to 6 full racks of electronic hardware space

inside an environmentally-controlled shelter co-located with the

antenna, allowing for expansion of up to 20 satellite modems

and network connections. Additionally, with the bandwidth

capacity of a typical deployable earth terminal, no hardware

changes are necessary to scale from a 10 MBPS/10 MBPS circuit

all the way up to a 100 MBPS/200 MBPS circuit.


Reliability VSATs provide limited reliability for their end users. A typical

VSAT will provide approximately 98% availability (175 hours per

year of downtime), and the Mean-Time-To-Repair (MTTR) a VSAT

is between 30 minutes and 2 hours, depending on the availability

of trained technicians. VSATs are single-threaded systems,

meaning they have several single points of failure in active

components. Additionally, most VSAT antennas are manually

pointed, so if the antenna is misaligned by a wind gust or an

accidental bump, a trained operator must realign the antenna.

Deployable earth terminals are extremely reliable systems, which

is a key reason they are chosen for critical C2 operations and

base-wide infrastructure support. Since 1999, Deployable earth

terminals fielded by US CENTCOM and US AFRICOM in

Southwest Asia have provided 99.95% availability (4.3 hours per

year of downtime) in the harsh conditions like those at the Balad AB.

The downtime is mostly attributable to satellite/sun conjunctions,

which happen twice a year at each equinox (spring and fall) and

impact every satellite link in the world. Additionally, the Mean-

Time-To-Repair (MTTR) is less than 1 second. These terminals

have 1:1 or 1:2 redundancy in all active components, along with

state-of-the-art monitor and control (M&C) software which

exponentially increases their reliability and gives engineers

remote troubleshooting, control, and configuration capability.

Deployable earth terminal antennas are automatically controlled,

positioned, and continuously track the satellite. This helps to

avoid issues such as the antenna losing the satellite link by being

moved by wind gusts or other forces. This motorization of the

antenna also increases satellite options to use inclined orbit

satellites that are typically lower in cost, and to quickly and simply

switch to a different satellite if necessary.


Parameter 1.2M VSAT 3.8M Deployable Earth Terminal

Antenna Aperture Size 1.2M 3.8M

Passive Antenna Gain (Ku-Band) 40 dBi 51 dBi

Maximum Transmit EIRP 58.6 dBW 82.1 dBW

Maximum G/T 20.8 dB/K 32 dB/K

Antenna Positioning Manual (typ) Auto-Track

Scalability 1 Carrier 20 Carriers

MBPS of Throughput per MHz of Bandwidth 1.0 1.8 - 2.2

Max Uplink Throughput 4 MBPS 100 MBPS

Max Downlink Throughput 20 MBPS 200 MBPS

% Link Availability 98.0% (typ.) 99.95%

Outage Hours Per Year (max) 175 Hours (typ.) 4.3 Hours

Mean-Time-Between-Critical-Failure (MTBCF) 25,000 Hours 1,000,000+ Hours

Mean-Time-To-Repair (MTTR) 30 min. - 2 hrs. < 1 sec

User Interface Modem Console M&C Software Suite

Electronics Enclosure Customer Provided Integrated Shelter

UPS Power N/A 15 minutes

Automatic Power Transfer to Generator N/A Integrated Generator &Transfer Switch

Redundancy & Protection None 1:1 or 1:2

Tradeoffs For users seeking a backhaul connection to a larger enterprise

network or the Internet, the tradeoffs in determining the

appropriate class of terminal are many. Below is a list of the

common tradeoffs, and how to weigh them when making a

determination.


Historical Use Cases

AT&T Calling Center, Bagram Afghanistan

This system was installed by AT&T to provide 12

simultaneous phone conversations or 2 simultaneous

video teleconferences (via Skype) between soldiers

and family members back home. The terminal was

replaced with a larger 3.8M terminal two weeks after

installation due to the high demand for service.

Tactical C2 Forward Operations - Battalion

This SIPR/NIPR Access Portal (SNAP) terminal

provides forward operating bases (Battalion level

operations center) with 8 VoIP phone lines and a total

throughput of 4MBPS/4MBPS in a TDMA network.

SNAP provides secure C2 communications and non-

secure Internet access for non-critical operations.

Deployable Ku-Band Earth Terminals (DKETs)

Since 1999, DataPath (now Rockwell Collins) has

provided more than 100 DKET terminals to the US

Army and other US and FMS users. The vast majority

of these terminals have been fielded to SWA. They

provide heavy backhaul traffic and intra-theater

networking support, and are an integral component to

the C2 network for CENTCOM and AFRICOM.

We can help your operation Envistacom delivers end-to-end communications, networking, and security solutions to the diverse markets of defense, government, and commercial enterprises. Contact us today to learn more about what we can do for you.

470-255-2500 [email protected]

© Envistacom 2014. All rights reserved. (V2_5-14-2014)

About Envistacom Headquartered in Atlanta, Envistacom is a privately-

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application and security solutions to defense,

government and commercial enterprises. Envistacom

designs and delivers the right technology solutions to

meet unique and complex business challenges. Their

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