Superluminal communications

Superluminal communications or FTL communications is the science and technology of transmitting information faster than conventional, EM-based means allow. The only means of faster-than-light communication known to the modern civilizations is to use wavespace, a colloquial term for fairly narrow slipspace layers not traversible by matter but optimal for transmitting EM signals. On the basic level, wavespace communications function like normal telecommunications, albeit propagated through a medium where electromagnetic radiation can travel faster than light. A wavespace communicator includes three principal components: a transmitter (usually a high-energy maser), a slipspace field generator that routes the transmitter's radiation through a small wormhole, and a receiving antenna adjoining that wormhole. Transmitter- or receiver-only systems also exist, though these are mostly limited to emergency beacons or immature network technologies such as that used by the UNSC up until the 2570s. Other means of faster-than-light communication involve probes or courier ships sent through slipspace.

Terminology
The medium through which faster-than-light transmissions travel is known as wavespace. Covenant wavespace transceivers are commonly known as wavecasters, while the UNSC calls them wavespace relays, slipwave relays or simply comm buoys. The Phoenix Initiative's post-war commercial comm network is known as Slipnet.

Covenant wavespace transmissions, especially those of importance, are commonly known as missives.

Overview
Broadly speaking, there are two major types of wavespace communicator:
 * Broadcast: a non-focused radio signal propagated through wavespace. Most useful over short ranges (less than 20-30 AU for the UNSC); will scatter more and more as the distance increases.
 * Point-to-point: effectively a high-power maser pointed at a wavespace portal, with a receiver at the other end. Most interstellar comm relay systems use this method.

Technically, there is no distinction between wavespace and slipspace; the former is merely a term for specific dimensional sets within the latter. Thus, wavespace shares many of its limitations and quirks with slipspace in general. Wavespace encompasses slipspace pathways too infinitesimal for matter to traverse, while enabling optimal and energy-efficient passage for radiation. Like normal slipspace, there are "layers" to wavespace, with "higher" layers being more efficient but more difficult to tap into. Useful wavespace bands are also very narrow, much more so than slipspace pathways, making wavespace communication like trying to thread a series of tiny needles over a distance.

This is also why focused tightbeam-like transmissions are much easier to keep coherent over a distance than omnidirectional broadcasts. Because of the chaotic, non-Euclidean nature of slipspace, the photons that carry information are increasingly prone to scattering over long ranges, and may arrive incomplete and out of order, rendering transmissions unintelligible. On ranges longer than a few AUs, one must know — at least roughly — where they're sending, and focus the data-stream to that target. Omnidirectional broadcasts are possible, but across interstellar ranges, special methods (such as Forerunner modulating crystals) are needed to maintain coherence in the signal, and even then scattering can be an issue.

Like slipspace travel, sending signals through wavespace is a complex interplay of several main factors: Energy, the "resolution" of the interface, and computing power. With enough energy, signals can be "brute-forced" through wavespace, and this is how the first UNSC communicators worked. The Covenant have an abundance of energy as well as high-resolution interfaces, enabling their wavecasters to deftly weave efficient trajectories through wavespace, like a scalpel to the UNSC's hammer. However, the limits the Covenant imposed on high-end computing also placed limits on their ability to calculate pathways, leaving them with technology that is technically very impressive but rather poorly optimized.

Rules and limitations

 * Like slipspace, wavespace has layers. The higher a layer, the further a transmission reaches. Higher layers require more precision and more energy to tap into, and the Covenant and later the UNSC have accessed only the lowest few.
 * In order to listen to a broadcast, you have to access the layer it is being transmitted on. This is only possible by using a receiver tuned to that specific layer (advanced wavespace receivers, such as those used by the Covenant, can be tuned to a spectrum of layers at a time).
 * You can transmit a narrow beam, or broadcast a signal omnidirectionally with greatly reduced range. The more focused the signal, the more reliable it is.
 * Interstellar slipwave signals are not easily intercepted unless one knows exactly where and what to look for. If you know roughly where the recipient (e.g. a planet or ship) is, it is most useful to point your relay in their direction.
 * Although Wavespace is more orderly than Slipspace, it does not match up 1:1 with realspace. Locations need to be mapped to one another, and the relation between Wavespace and Realspace tends to drift.
 * Slipspace currents affect the speed, accuracy and coherence of wavespace transmissions as well, and a transmission going against the current can be considerably slower than one sent either through calm wavespace or along a current. This variance is similar to that experienced by ships traveling in slipspace, i.e. up to 20% faster or slower than average depending on the direction and strength of the current.
 * Gravity affects wavespace. As transmissions are scattered by the mass shadows of gravity wells and the interference of variances in the interstellar medium, they become warped and distorted; parts of the content are lost, or arrive in a random order, making them useless. As such, it is preferable to place communication relays in Lagrange points or even at a system's edge, though the best Covenant communications systems can compensate for this.
 * A network of wavespace communicators need to broadcast often and make periodic adjustments to their aim to stay in contact. The frequency of adjustment increases as the distance between a broadcaster and a receiver increases. At the maximum range that the best Covenant communication signals can reach (roughly 4,000 light-years), it requires almost constant input or the signal will wander off target.
 * Wavespace communications cannot be used while in slipspace; it has been theorized that the stochastic interplay between the inter-nestled slipspace fields may result in a catastrophic higher-dimensional singularity.
 * The further you're transmitting, the more unpredictable the transmission. The signal may arrive late, or the information content may be out of order.

Network types
Human interstellar communications networks operate in three distinct layers:
 * The first is the planetary net, encompassing a single world and its orbital space. The planetary net requires no wavespace technology, as it has no detectable light lag. The vast majority of civilian data transfer occurs within the bounds of individual planetary nets.
 * The second is the system net, which encompasses a star system. Prior to the advent of FTL communications, noticeable light lag would occur at interplanetary scales, meaning that the interplanetary network cannot act as a single real-time net but rather a "meta-network" in which different planets' and habitats' discrete networks communicate with one another through a complex set of protocols. The communication delay varies from seconds with planet-moon distances to minutes with close interplanetary distances and hours with long interplanetary distances. In a wavespace-based network, this lag is effectively eliminated, and some systems have been able to link their colonies in a singular real-time network.
 * The third layer is the interstellar meta-network, in which planetary and/or system networks exchange data with one another. Not all data is automatically exchanged, and networks have complex protocols for determining what is transmitted. Civilian communications, especially, must go through complex filtering protocols, with limited bandwidth allotted to civilian messages. Even with the advent of wavespace communications, this process is not instantaneous. While far swifter than in the preceding centuries, the speeds of interstellar data transfer are now somewhat comparable to previous in-system transfer speeds, with lag time measured in hours or days. In terms of the experience, civilian communication across interstellar distances has historically been much akin to overseas correspondences in the Age of Sail. Superluminal communications has made it possible to develop intersystem message boards, though correspondence on such platforms is still relatively slow due to lag time.

Data couriers
Prior to the development of wavespace communicators, the UNSC and human civilization overall had to rely on slipspace-capable starships to deliver messages over interstellar distances. Across the Outer Colonies, communications were most often carried in the databanks of various civilian ships, such as automated freighters. However, within the Inner Colonies and other major population centers, various corporations operated entire fleets of dedicated courier ships with cargo composed entirely of hard drive space. These ships flitted in and out of systems incessantly on predetermined paths like paternoster elevators, refreshing the local system- or planetary networks with new data as they moved about. On the most trafficked routes, there could be multiple courier ships carrying virtually the entire data of a system network on the way at a time. On the other hand, many remote colonies would only see periodic updates of key news and mail when data-carrying freighters traveled there on a weekly or monthly basis, or even less frequently. This informational isolation also did its part to exacerbate the Outer Colonies' physical distance. With virtually all of the major human colonies linked via wavespace by the later decades of the 26th century, interstellar information exchange has increased drastically, though most correspondence still occurs between the inhabitants of a colony.

COM launchers
Created in the later years of the Human-Covenant War, the slipspace COM launcher is a secure military system that launches a self-guided probe through slipspace at a specified destination. It has several advantages over wavespace relays. The main challenge with wavespace communications is that you're essentially trying to throw a curveball and hit a tiny target increasingly far away, whereas with slipspace travel you're actively modulating the slipspace around you as you go. This is also why the UNSC's first success with FTL comms was the COM launcher; as the probes are capable of independently navigating slipspace on the way and didn't have to do all the calculations at the source. Even after the advent of wavespace comms, the probes remain more reliable and secure for long-range comms, though they do remain prohibitively expensive.

Wavespace communications
While humanity has had the theoretical basis for wavespace for almost as long as slipspace theory has existed, it was only through research into Covenant slipspace technology during the war that enabled the UNSC to build the first functional FTL communicators. As with slipspace navigation, the main problem was accuracy and resolution; human technology simply could not parse the fractal dimensions of slipspace in enough detail over a distance to effectively send signals through. Slipspace travel, meanwhile, was easier because the Shaw-Fujikawa drive can constantly recalibrate the ship's flight path as it traverses slipspace.

Though prototypes of FTL communicators existed throughout the 2530s and 2540s, the first designs were large, energy-inefficient and cumbersome. While smaller prototypes were created, they tended to be extremely unreliable and were rarely able to keep their signals coherent across interstellar distances. What the UNSC did learn around this time was creating wavespace receivers capable of listening in on Covenant transmissions, and doing so quite effectively. By 2552, these receiver devices could be miniaturized to fit an individual suit of MJOLNIR armor, into which the technology was incorporated in the Mark V generation, though these components were highly expensive and state-of-the-art.

The first practical wavecasters, then still limited to in-system transmissions, were installed on select remaining Inner Colony systems' early-warning listening posts in the second half of the 2540s. For that time, and for several years onward, they remained in strict FLEETCOM priority use only. These early wavecasters were very limited in the complexity of data they could reliably transmit, strings of plain text being virtually the norm until 2555. By 2552, a handful of Navy battlegroups had short-range communicators installed for in-system coordination. The core Inner Colonies were also equipped with a primitive fixed intersystem warning network enabling communications to reach nearby systems within hours; this, for example, allowed the UNSC to recall fleets from nearby systems to Reach upon the Fall of Reach.

Coupled with earlier discoveries, along with the capture of a number of Huragok in the final months of the war, study of Covenant equipment captured over Reach during Operation: FORTRESS SIEGE considerably improved the UNSC's understanding of wavespace, specifically in the area of making relays more portable and less sensitive to interference and synchronization errors. By 2553, the first intersystem-capable wavespace communicators were installed on select Navy ships, and by 2560, all independently-operating Naval units had at least one long-distance communicator equipped, usually on the flagship or as a set of deployable relay satellites as these were more reliable than ship-borne devices.

It was only in the 2560s that the technology panned out in commercial use, through the Phoenix Initiative-launched Slipnet project. As the UNSC's resources remained limited, the construction of the colonies' slipwave communicator network was privatized to the Slipnet Consortium, consisting of several human telecommunications companies.

Superluminal communications had a massive impact on human communication. The notion of comparatively fast communication with other star systems, or even real-time communication within a star system was if not alien, at least a speculative fancy at best to most people in the first half of the 26th century. It would come to revolutionize how people and societies conceptualize themselves in the overall framework of the human sphere, a new information revolution akin to the telephone or the internet on Earth. And it had major ramifications on the inner workings of the UNSC and human civilization as a whole. They could now comfortably colonize worlds further away, as despite the travel time, communications took much less time. Both colonial populations were also now to talk to one another in more reasonable time spans, which in time would come to reduce alienation in many places. However, casual interaction with other star systems — such as the Internet of today — would still be some time away. Individual planets and/or systems mostly still have their own isolated networks, and interaction between those networks is more akin to old-fashioned mail than the real-time global communication provided by the Internet.

Development
Communication burst speed: 1.8 LY/hour (avg.); Range: ~14 LY; Information content: Plain text strings
 * First generation (2544-2554)

Wavespace relays (both transmitters and receivers) must be calibrated to a fairly specific distance and destination, which in practice limits them to point-to-point transmissions between individual relays; meaning a relay cannot receive messages from outside the region it is attuned to. Relays would constantly drift out of focus; in the early years, they had to be manually recalibrated, before reliable auto-correction mechanisms were developed in the mid-to-late 2550s.

Early relays as of the late 2540s and early 50s had to be placed at the very edge of star systems. These devices were strictly for military and government use.

Communication burst speed: 2 LY/hour (avg.); Range: ~21 LY; Information content: Plain text, images, some audio
 * Second generation (2555-2570)

Communication bursts had an average speed of two light-years per hour, and though more consistent than slipspace travel, the exact speed also varies based on the local slipspace topology. This puts Epsilon Eridani at around five hours from Earth, and the more distant colonies at three days away. The second generation saw the emergence of the first commercial FTL communicators under the Slipnet Consortium.

The maximum range of second-gen UNSC wavespace communication bursts is ~21 light-years. This means that communiques transmitted throughout the Human Sphere must be bounced through an elaborate network of relays as opposed to, for example, a relay on Earth being able to transmit to a remote colony directly. This also means that a malfunctioning, damaged or missing relay on the way will compromise the entire system. To counter this, the UNSC was quick to develop at least one redundancy for each relay. The 2560s saw the introduction of an additional "shadow relay" network of stealth-enabled wavespace buoys, used for both the interstellar early-warning network and in the event the normal relay system were to be sabotaged.

Similar to slipspace entry and exit points, relays should be installed in gravitationally stable locations, such as Lagrange points, to minimize interference; gravity wells can easily scatter transmissions or warp them off target.

By 2560, most UNSC ships had in-system "broadcast" communicators installed to eliminate light lag. Ship-portable interstellar communication relays remained scarce, and only fitted on fleet flagships or important logistics vessels since 2554; even then, fixed relays remained more reliable. Flotillas or squadrons operating in systems without comm relays would often deploy a stationary relay satellite in a local Lagrange point for communication as this remained more reliable than using a ship-borne system. In star systems with existing communications networks, ships would simply link to the nearest relay.

Communication burst speed: 7 LY/hour (avg.); Range: ~50-70 LY
 * Third generation (2567-)

By the late 2560s, the wavespace technology used by the UNSC military and the Phoenix Initiative was already capable of communications around twice the speed, range and reliability, though civilian networks were slower to adapt. By this point, some colonies, particularly those of the Via Casilina Community, had also made deals with ex-Covenant signals guilds to set up their own homegrown networks based on the Covenant technological base.

Specialized precision devices based on the earlier COM launchers were capable of even greater ranges and speeds.

Applications
Slipbeacons are emergency-use, broadcast-type wavespace signal transmitters. Due to the constraints of the technology, however, they have a very short range and actually require another ship to be nearby (usually within the same system) to pick up the signal; their operational lifespan is limited as well by their power supply. Some late-war and post-war types are able to send out both close-range bursts of several AU and remote signals to a distance of up to 30 AU, though how often the more energetic long-range signals can be transmitted is also dependent on the power available.
 * Slipbeacons

The telemetry probe was a mid-war innovation and one of the UNSC's first viable wavespace technologies. The probe is a small, stealthed drone designed to attach itself to an enemy craft as it jumps away, record its slipspace path and the coordinates of the destination, and then transmit them back to the UNSC using a wavespace relay. However, the early probes were extremely unreliable and had only worked once as of 2537, both because of the unreliability of the wavespace technology at the time and because the Covenant typically detected and destroyed the probe before it could attach itself on one of their ships. By the late and post-war eras, the technology had improved considerably with the overall advancements in the UNSC's understanding of wavespace.
 * Telemetry probes

Covenant
The Covenant relied on several varieties of wavespace telecommunications technology to retain cohesion within the vast Holy Ecumene. Like many other Covenant technologies, Covenant wavespace communicators rely heavily on gravitic technology. Gravitational lensing is used to focus the transmitter's beam as well as to capture the signal at the destination, via a gravitic field-based receiving medium directly reverse-engineered from a Forerunner equivalent (where UNSC counterparts must rely on physical antennas).

Most Covenant wavecasters have a fairly limited range. Those installed on most mainline Covenant ministerial warships can reliably transmit over a hundred light-years of calm slipspace, but rarely reach over 200 LYs without scattering beyond legibility. Civilian vessels or lesser military craft often lack wavecasters altogether, instead relying on their fleets' flagships or deployable communications beacons for interstellar transmissions. The few smaller ships that do have FTL comms are usually forced to make do with short-range transmitters capable of reaching several dozen light-years at most. Only wealthy clans and guilds have access to devices approaching military ones in transmission range and clarity.

Covenant slipspace communications are fast, but instantaneous only over short distances. Depending on the specific technology in use, long-ranged missives (i.e. over thousands of LYs) can still take days to arrive.

Similarly to humanity, the Covenant had wavecaster technology in some form almost as long as they had slipspace travel, owing in part thanks to the Sangheili's long starfaring history prior to the War of Beginnings. These original technologies, like their transportation equivalents, were largely "home-grown" technologies due to the Sangheili cultural distaste for tampering with the artefacts of the Forerunners. However, these technologies were eventually enhanced with revelations gleaned from researching Forerunner artefacts. The conquest of the Rhiln collective in the 2nd century CE would later see the Covenant reap the spoils of war from the shattered Rhiln dyson swarm - whom had utilised extremely advanced wavespace communications technology to enhance the speed of thought for their collective shared consciousness. Coming at the trailing end of the First Illumination, this saw a generational jump in FTL communications throughout the Covenant.

Grand wavecasters
There are also devices, known as grand wavecasters, that are capable of much greater ranges through the use of Forerunner-sourced modulating crystals that tap into higher layers of wavespace. The grand wavecasters number in the low hundreds and are found in the primary domain capitals, key reliquaries, and the flagships of major Covenant fleets. They were used exclusively for strategically important empire-wide communication.

Grand wavecasters use arcane Forerunner techniques to link, as far as anyone can tell, directly into the other devices of their type; as such, they were capable of raising High Charity virtually wherever in Covenant space it was, unless it moved beyond their range. They cannot be listened in by anyone other than those with access to devices capable of reaching the same higher wavespace layers, making the network effectively self-contained. Through these, the Hierarchs' sermons could be broadcast to the entire Covenant. Though even these transmissions are not instantaneous, they are much faster than ordinary wavecasters. Planetary or regional lords and/or the synodic magistrates were responsible for relaying these sermons to their subjects across the entire domain.

The grand wavecaster network is reliable up to around 3,000 light-years, and has a maximum range of about 4,000 light-years. As with slipspace travel, sending messages along a galactic spiral arm is more reliable than sending them to another spiral arm; due to this, the grand wavecaster network had several relays installed at regular intervals far outside the core Covenant Sphere both along the Orion Arm and in the Perseus and Sagittarius Arms, for example. These stations were manned and acted as both remote listening posts and relays for exploratory fleets which operated far outside the Holy Ecumene, though even their range was limited to the overall neighborhood of the Orion Arm. Fleets sent to circumnavigate the galaxy, for example, were virtually on their own as they left the region and passed into Ulterior regions.

Firmly in the realm of Entrusted technology, a special religious order formerly under the oversight of the Ministry of Edification oversaw this network, and were the only ones capable of properly maintaining it. Even after the onset of the Great Schism, there exists a sacred order borne out of the remains of the Ministry of Edification that remains capable of repairing the grand wavecasters. They are near-universally respected and allowed passage past factional borders due to the strategically crucial nature of their work.

The Covenant's imperial wavecaster network also had a "signal fire" system based around a handful of very simple encrypted and pre-programmed messages understood only by the High Council. The messages would pass through every domain's grand wavecaster without said domains' authorities being fully aware of their contents. This was a security measure to ensure delicate information did not end up in the wrong hands or was not tampered on the war, e.g. in the event a wavecaster became compromised by a subversive regional faction. At the start of the Great Schism, the Prophet of Truth used this network to issue his ultimatum to high-ranking San'Shyuum in the domains, compelling them to cast down the Sangheili and elevate the Jiralhanae in their stead. However, only a small number of the domain magistrates actually followed Truth's orders in the end.

Other communications networks
Outside the imperial communications network, Covenant FTL communications capabilities varied greatly. Generally, the communications technology available outside the ministries was considerably inferior, and heavily regulated. Individual guilds and clans (or associations thereof), regional governments, and various organizations frequently had their own communications networks, often not much larger than several systems.