Satellite Link Technologies (Updated)

This one is for all you Starlink and SkyMuster users who have to use them due to the remoteness of their properties. In these technologies there is two examples of how they are deployed, which provide very remote customers with access to the internet. What satellites are is really a floating relay station. So satellite technologies are based around three core components.

Name	Role
Orbital Satellite Station (OSS)	Acts as a data relay receiving information from the ground user terminal and relaying it to the ground receiver station it works effectively as a relay bouncing ground traffic off the station from users and then sending to GRS's
Ground User Terminal (GUT)	This is what we commonly associate with the "dish" this is how users connect to the orbital stations and send and recieve traffic from this station often operating at a much lower frequency then ground receiver stations.
Ground Receiver Station (GRS)	Are basically "satellite data aggregator nodes" they talk all of the GUT's data and sends it to a from the multitudes of users to these facilities that have high bandwidth connectivity via fibreoptic connections, they are usually located in the country in which the traffic destined for.

Geostationary

This is commonly what is offered via Skymesh, the way it functions is there is a base-station and a satellite access station placed in space, this satellite is placed a long distance from earth which allows a single satellite to provide coverage for a large area the reason this is possible is due to the concept of transmit aperture this is approximately a cone formed by the transmitters and receivers on a satellite these systems are typically very high bandwidth single potentially more satellite if there is more than one they use what is called an ISL (Inter-satellite link) this forms a bridge between two or more satellites which can either be done using another radiolink like the transducers and transceivers on the actual satellite, or they can use a point-to-point connection using a laser beam.

Inter-satellite link

This is what is used to 'bridge satellites that are not directly reachable' due various factors, but the inter satellite link can be one of two designs. One design is standard radiowaves or microwaves, this is similar to how you would transmit a radio signal P2P (Point to Point) allowing for a 'bridge' between two separate satellite communication nodes orbital station itself. Microwave links are often parabolic antennas attached to a "mast" that then relays the traffic from one end point to the next some common high frequency point to point links are 60Ghz and others these are often used on earth to transmit data between for example cell towers who are remote and have no ability to connect via fibreoptic primary link trunks. Same goes for ISLs they are used to bridge one node to another and relay traffic between them, and ISLs are typically half duplex unless dual single mode lasers are used in the case of a satellite that would look like two independent transmission frequencies one for the upstream and one for the downstream. The other version of an ISL is based on lasers in space effectively it is "empty" at least for the purposes of laser communication you can fire a laseer from one point in space to another with very little attenuation even less than in fibreoptic links, this works off typically WDM (Wave division multiplexing) which is very similar to how the NBN does data transmission you run two independent laser beam wavelengths down one cable to allow you to transmit both independently other name of this is called a GPON (Gigabit Passive Optical Network) then reconstruct it on the other side, ISL units like those used in starlink are effectively this same technological idea but no single mode or multimode fibre cable is used, however it might be very similar to the SM modules used to transmit single mode data over 25Kms for example but in space you can transmit much further and much faster, with no regard for the water refraction effect just 1 point to another point. ISLs can also degrade in performance if the amount of people connected to the network is larger than the ISL can cope with there is a direct relationship between the total number of users on the starlink network and the maximum achievable bandwidth permitted.

Low Earth Orbit (LEO)

This is what people commonly talk about as Starlink, this is what we call a low earth orbit satellite constellation, where the workload between satellite is distributed across a fully connected mesh network, that simply means all the satellite have an ISL (Inter-satellite link) an ISL is another name for backbone link. On Starlink V2 sats is used to connect all of these small "cellphone towers" in space because that is effectively what they are, using a phased array antenna the to create a wide enough transmit aperture multiple satellite as needed this is why there is so many Starlink sats deployed up there, it is to allow them to have the maximum coverage possible by swarming together the satellites to make them behave as a single network and ensure the best coverage. Secondly low earth satellite purely because of their nature have much lower latency travel time to the satellite is much shorter and therefore high speeds are possible and low enough latency for online gaming. Starlink units come in two types the fixed point phased array design and the tracking version. a phased array can be "steered" toward a target transmitter however the aperture angle permitted by the phase array is limited, usually a few degrees. One way to mitigate this is by using a self-tracking antenna it still uses the standard phased array while it also employs a rotational around the the base and a tilt based angle adjustment to maximize coverage.

Other problems that can affect star link ground terminals is heat, high temperatures can lead to the terminals reducing the amount of power they are consuming to prevent them from overheating and shutting down, in Australia this especially important as we can often get temperatures that reach in the 40*C range in some places, other problems with the technology are similar to those found in standard satellite technologies namely rain fading during heavy downpour antennas can have their radio-waves distorted as they are transmitted, causing multi-path loss, this is very similar to if you reflect a mirror off a uneven reflective surface and the path of light rays scatter all over the place, but it also happens to absorb the radiowaves as well similar to how a microwave oven absorbed energy from the microwaves to convert into heat this same process happens, clouds do as well. So you are dealing with the following multi-path effects.

• Refraction (distortion of the signal passing through a medium and being bent)

• Reflection (waves / rays bouncing off the surface of objects or microscopic water droplets)

• Deflection (radio waves outright get shot in multiple different directions)

• Absorption (The energy of the radio-wave is converted to heat and the kinetic energy of a medium slightly changes albeit a tiny amount

The result from all these effects is ghost signals, phase shifts and scattering of the signals so when it arrives at the destination it has to be error checked, cleaned and then processed.

Network Congestion effects

These also show up in terrestrial networks mobile phone towers and other technologies experience the same thing, for example the NBN with fixed wireless suffers considerable degradation as there is limited bandwidth at nodes similar to a geostationary satellite more people less bandwidth available per person, less speed available per person overall, as well as the switching overhead from queuing, shaping and performing other QoS prioritization.

This applies to both LEO and non-LEO based satellites however the reasons are quite similar but different. In he context of geostationary facilities they have a maximum number of transceivers which often very large, but if enough users end up accessing a satellite which has a large number of these transceivers it rapidly becomes a problem as the satellite has to start employing queuing and scheduling to determine the kinds of workloads that ensure "good enough" similar problem occurs on LEO satellites except LEO satellites have another enemy every node traffic has to pass through is similar to that of a routing network, as such if a satellite relays through 20 nodes to get to a destination the latency will be higher if a satellite relayed through 10 nodes instead, so while use LEO satellites ISL links can be very fast the travel time of each traffic hop it not guaranteed while it is attempted to be optimal if a number of nodes are already overloaded the rest of the network will suffer and at any one time the number of satellites available will affect the routing speeds, if there is 2 satellites having 50% each of traffic then this will be considerably more expensive, but also during that node routing they must determine the "fastest" transmission round between each satellite and the ground station receiver.

Traffic Scheduling

To address this problem for users and connections. In the case of both LEO and Geostationary facilities, it is best to use the appropriate hardware and network gear to efficiency and correctly divide up the available bandwidth, this is why QoS prioritization at the WIFI level and the network level should be employed to ensure reliable connectivity instead of focusing on "best effort" missing QoS classification can prevent the allocation of network resources appropriately most WIFI uses.

The term used to describe this kind of scheduler is a CLASS BASED SCHEDULER often include the following this kind of scheduler also works on the satellites themselves.

• Standard Web, Email or other traffic (uses little bandwidth but persistent stable connection)

• Gaming (Can sometimes require lower latency but depends on the game)

• Critical network protocol messages (VOIP, DNS, NTP) often prefer to have low latency

• Video and Audio (High bandwidth but depending if it's realtime will affect how much it is affected realtime video requires both high bandwidth and sometimes low latency as long as the image is reconstructed in a reliable amount of time.

By dividing traffic into classes the resources for each service can be better allocated efficiently while also supporting a large number of client endpoints and devices and maintain reliable service.

How to choose satellite connections

Technology	Reasons for Choice
Starlink	Lower latency, higher bandwidth and connectivity especially good if you want a roaming connectivity provided by your ground terminal station. Roaming costs are very high.
NBN Satellite (Sky Muster)	You do not need low latency, but you can get high bandwidth, Skymuster might be more suitable in places where coverage for starlink is likely to be restricted, such environments might include places that like Africa, or other locations, it also comes down to cost, NBN might be cheaper than Skymuster in some cases. As a business you can actually leverage this as a normal organization and use this as a redundancy path for connections.