Is there a reason we keep trying to use higher frequencies in every new wireless standard (Wi-Fi, 5G, now 6G) instead of trying to increase the maximum possible bitrate per second into lower frequencies? Have we already reached the physical limits of the amount of data the can be encoded at a particular frequency?
Lower frequencies have the advantage of longer distances and permeating through obstructions better. I suppose limited bandwidth and considerations of the number of devices coexisting is a limiting factor.
> Have we already reached the physical limits of the amount of data the can be encoded at a particular frequency?
Basically, yes (if you take into account other consideration like radiated power, transmitter consumed power, multipath tolerance, Doppler shift tolerance and so on). Everything is a tradeoff. We could e. g. use higher-order modulation, but that would result in higher peak-to-average power ratio, meaning less efficient transmitter. We could reduce cyclic prefix length, but that would reduce multipath tolerance. And so on.
Another important reason why higher frequencies are preferred is frequency reuse. Longer distance and penetration is not always an advantage for a mobile network. A lot of radio space is wasted in areas where the signal is too weak to be usable but strong enough to interfere with useful signals at the same frequency. In denser areas you want to cram in more base stations, and if the radiation is attenuated quickly with distance, you would need less spectrum space overall.
>Longer distance and penetration is not always an advantage
Exactly. When I was running WiFi for PyCon, I kept the radios lower (on tables) and the power levels at the lower end (especially for 2.4GHz, which a lot of devices still were limited to at the time). Human bodies do a good job of limiting the cell size and interference between adjacent APs in that model. I could count on at least a couple people every conference to track me down and tell me I needed to increase the power on the APs. ;-)
One event I particularly remember, the venue had ONE AP (and they had assured us that they could provide WiFi coverage for our 500 users, that was set to high power, their AP I found during the event, it was on the floor under a bench outside the master ballroom. This was the venue that I eventually tracked down was handing out DHCP leases with IP addresses that had a gateway address in a different subnet than the client IP. That was, admittedly, 2005, but the confidence they had in being able to serve our attendees, despite us telling them it wasn't going to be as easy as they thought, was stunning.
We don’t move to higher frequencies just because we’ve run out of ways to pack more data into lower bands. The main reason is that higher frequencies offer much wider chunks of spectrum, which directly leads to higher potential data rates. Advanced modulation/coding techniques can squeeze more capacity out of lower bands, but there are fundamental physical and regulatory limits, like Shannon’s limit and the crowded/heavily licensed spectrum below 6 GHz that make it harder to keep increasing speeds at those lower frequencies.
In addition to what others have said, Often from a network perspective you want smaller range.
At the end of the day, there is a total speed limit of Mb/s/Hz.
For example, in cities, with a high population density, you could theoretically have a single cell tower providing data for everyone.
However, the speed would be slow, as for a given bandwidth six the data is shared between everyone in the city.
Alternatively, one could have 100 towers, and then the data would only have to be shared by those within range. But for this to work, one of the design constraints is that a smaller range is beneficial, so that multiple towers do not interfere with each other.
5G's trick is MIMO. Basically just using more channel space for more data. In some places that means 3G/4G spectrum + 24GHz + 60GHz. And responding when you close a door and the 60GHz goes away. In some parts of the world where licensing worked out differently, it might just be a couple chunks of old 4G spectrum. Its not a monolith.
I used to have some early engineering material outlining what had been approved for use in each country and 24GHz was pretty damn common. Could be that changed I havent kept up.
I do know in Australia we have sweet FA and 5G isnt very interesting at all.
mmWave is amazing in any kind of packed arena/stadium. Never was able to even use my phone at a basic level before, now can get low latency gigabit+ speeds which is insane.
In practice sub-6 bands are just good enough in most scenarios. We're 5+ years into mmWave deployments in the US and there's still very little interest or regulatory push worldwide.
For instance it's completely stalled in South Korea which has one of the highest 5G coverage and market penetration. In Japan I found articles from 2023 claiming the mmWave coverage was "0.01%" then, I don't know if it expanded in the meantime. In Europe there's virtually zero production deployments or devices sold with the compatible modem/antennas. While there are small deployments in Australian cities, Apple doesn't bother selling compatible models. Etc.
Only tangentially related, but on my MacBook Pro simply running
cat /dev/random
causes my terminal to hang and my speakers start emitting a loud buzzing sound until the terminal is force-quit or system is restarted.
I can understand the terminal not being able to handle the amount of data from /dev/random but for the speakers to start emitting sounds as a result of this is certainly very strange. Almost like /dev/random was being piped into /dev/audio or something. Anyone have an explanation?
This ASCII 7 (C escape "\a"), which when printed emits a bell sound. The exact sound is terminal dependent, and modern terminals won't use the PC speaker but rather play a sound using the audio hardware (which is required on Macs because they don't have a PC speaker). The bell isn't expected to be emitted often and quickly in series, so depending on the capabilities of the terminal program and the audio hardware, it may go haywire trying to play a more complex/longer sound repeatedly or overlapping (like seeming to lock up or slow down as the audio is queued). Your terminal may be configured to "flash" instead of emitting a sound when ASCII 7 is printed -- this may be implemented as rendering the entire window in reverse video for a short duration. A series of discrete bells played quickly may sound like a tone with a rising pitch. Other terminal oddities could occur if ANSI escape sequences. There are many ANSI escape sequences, for changing colors of text, moving the cursor, changing the typeface, or for querying terminal capabilities or customizing the terminal window title bar, that when printed randomly may make the terminal go haywire.
My initial thought is you're getting escape sequences or other signals to trigger the bell/chime. I've never had it crash a terminal but I've never really used a macbook. A common one I'll see in gnome terminal is the terminal printing out some info about itself (I guess there's a way to get some info back from the other side of a link) or changing the title bar.
An easy test would be to have something dump that bell character to the terminal as fast as possible and see if that does it, and also try /dev/zero to check that doesn't.
I had a United flight from SFO to YVR late last year and to my surprise, despite the notes that audio / video calls are disabled, I was able to have a crisp and clear FaceTime call! I was blown away by this, I always thought that the end-to-end bandwidth is sparingly low for such applications.
How can you possibly compare the Indian armed action to regain occupied territory and her sovereignty back from the Portuguese to anything else? It was the only time India had to resort to military action, and it was shortly after her independence.
> How can you possibly compare the Indian armed action to regain occupied territory and her sovereignty back from the Portuguese to anything else?
Quite easily. The claim was that India was never the aggressor, not that all the aggressions were justified by some extenuating circumstance or national interest or whatnot. The "never the aggressor" claim clearly doesn't hold for https://en.wikipedia.org/wiki/Annexation_of_Portuguese_India. I'm not saying that India shouldn't have done it, note, just that India has in fact used military aggression when it felt its national interests warrant it, which is perfectly normal for nation-states.
We can have a long discussion about whether we expect such situations, where national interests are judged to warrant military aggression, to arise in the future. But that's a discussion that should be had, not dismissed by appealing to untrue claims about history.
> It was the only time India had to resort to military action
Did you stop reading halfway though my comment?
Seriously, I think India has done a quite good job, as nation-states go, at not attacking its neighbors. But claiming things like "it was the only time India had to resort to military action" just doesn't look like it's supported by the facts to me. "One of the few times", yes.
I understand what you're saying, but I feel the "aggressor" is the party that first commits an unwarranted action. India was in the process of decolonization and the Portuguese refused to leave, despite prior repeated non-violent requests. If the cops are called on an individual for trespassing, would you call the cops the aggressor for trying to remove the individual?
> but I feel the "aggressor" is the party that first commits an unwarranted action
That right there is a problem at the heart of the concept of "aggressor": what time point do we pick as the baseline such that actions that lead to changes after that are aggression but actions before that are the status quo?
This played out in Europe with Alsace-Lorraine, where the Germans felt that the French took it away from them in 1919, while the French felt that the Germans took it away from them in 1871 and they just recovered it in 1919. Oh, but the Germans felt like the French had taken that territory away from them in the 17th and 18th century...
This is obviously a situation that is somewhat different from that of the Portuguese possessions in India. But it highlights the fact that "unwarranted" can be hard to define objectively. In practice, it tends to get defined by the victors writing the history books, though nowadays it can get decided by self-determination referenda and _then_ the victors (possibly of the referendum, possibly of resulting armed conflicts) writing history books.
From our point of view at the beginning of the 21st century, the Portuguese possession of Goa in the mid-20th was unwarranted but the British possession of the Falklands right now is... well, depends on whom you ask, but generally considered warranted. How much of that is because the population of the Falklands is happy being British subjects, and how much is because the British won the Falklands War? I wish I knew. :(
> If the cops are called on an individual for trespassing, would you call the cops the aggressor for trying to remove the individual?
No, I would not. But this isn't a perfect analogy either. I think it would be _very_ apt as an analogy if India had gotten a UN resolution that the Portuguese need to leave; even more so if UN security forces then threw the Portuguese out. Yes, I realize that this was not realistic at the time, for all sorts of reasons, not least of which was the US explicitly saying it would veto any such resolution, if I read the history correctly.
But as it was, the situation is more akin to the owner of the property being trespassed on seeing that the courts and the police won't help him out and personally kicking the trespasser off the property. Would that be described as "aggression"? It starts to depend on your biases, especially if the trespasser had been there for a while. This last is why the concept of https://en.wikipedia.org/wiki/Adverse_possession exists in English common law, so arguments over squatting and tresspassing won't continue ad infinitum. To some extent this gets applied in the international arena. Of course it doesn't always; then you get wars over territorial changes that happened hundreds or thousands of years ago; no shortage of those in recent history.
Anyway, at the time, there were a number of countries that condemned the Indian military action, including some which in principle supported the idea that the Portuguese possessions in India should become part of India. That is, they felt that the ends were good, but that the means were in fact military aggression and needed to be called out as such. We could try to fit that sort of dynamic into the individual trespasser being removed scenario; that would involve there being a dispute about whether the trespasser was in fact now more like a squatter, as well as dispute about whether forceful removal now, as opposed to peaceful removal, or at least removal by police, after some period of time gaining support for the removal was the better course of action...
Where all that leaves me personally is that I consider violent attacks on a previously broadly accepted status quo as "aggression" but I then have to allow that some "aggression" must be morally acceptable when the status quo either was unjust or has become unjust and no other solutions are available. Unfortunately, "unjust" is not an objective judgement either. :(
The situation with the Portuguese possessions falls into the "has become unjust" bucket for me, assuming the population of those areas wanted the Portuguese out. The Portuguese did not put this to a vote at the time, which is somewhat telling; I'm willing to assume based on time period and general zeitgeist that in fact the population did want them out.
Of course I would be happier to assume that sort of thing if I didn't know about counterexamples like the Falklands and Gibraltar. :( But as a point of comparison, Gibraltar _did_ have a vote on the matter in 1967, which is a pretty similar timeframe; presumably the Portuguese didn't put things to a vote because they were fairly certain they would lose.
> what time point do we pick as the baseline such that actions that lead to changes after that are aggression but actions before that are the status quo?
Not just the point in time, there's also the level of aggression. Many wars have a set of ever-increasing nonmilitary conflicts leading up to them. If you're not defining aggression as a concrete military action, you have to choose a baseline for this too.
If you're allowing governmental-agression-that-may-incite-war to be counted as a "first aggression", then India is doing this right now in Kashmir. Yes, I know, that situation is more complex (and I'd prefer not to discuss it online; there's a lot of nuance lost and it's frustrating), but there are similarities in the situation.
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Anyway, the definition of "aggression" to be used in this context depends on the context of the original statement, which was the argument that India is less likely to be a security threat because it has never been the aggressor. In this context, it is about military aggression, the argument being that a country more likely to escalate a civil issue to war is more likely to escalate to nukes in this modern age. To be clear, I don't feel that India is at all likely to escalate to nukes, due to various other reasons (including possibly personal bias). But I don't think that "India was never the first aggressor" is a valid argument in support of that.
By which definition? The "you could argue" definition that I don't agree with? Or my "personally, I would consider" definition?
By the latter, if country A is arming/training/providing insurgents in country B with no previous attacks by B on A, then A is the aggressor. So in the eastern Ukraine case Russia would be the aggressor.
How do you classify overt and covert military activity by a nation whose territory has been annexed towards the nation that did the annexation? Is it an act of aggression?
Lower frequencies have the advantage of longer distances and permeating through obstructions better. I suppose limited bandwidth and considerations of the number of devices coexisting is a limiting factor.