May 222020
 

For the past 2 years now, there’s been quite a bit in the press about the next evolution of mobile telephony standards.

The 5G standard is supposed to bring with it higher speeds and greater user density handling. As with a lot of systems, “5G” itself, describes a family of standards… some concern the use of millimetre-wave communications for tower-to-handset communications, some cover the communications channels for more modest frequencies in the high UHF bands.

One thing that I really can’t get my head around is the so-called claims of health effects.

Now, these are as old as radio communications itself. And for sure, danger to radio transmissions does increase with frequency, proximity and transmit power. There is a reason why radio transmitter sites such as those that broadcast medium wave radio or television are fenced off: electrocution is a real risk at high power.

0G: glorified two-way radios

Mobile phones originally were little more than up-market cordless phones. They often were a luggable device if they were portable at all. Many were not, they were installed into a vehicle (hence “mobile”). No such thing as cell hand-over, and often incoming calls had to be manually switched.

Often the sets were half-duplex, and despite using a hand-set, would have a very distinctive “radio” feel to them, requiring the user use a call-sign when initiating a call, and pressing a push-to-talk button to switch between listening and talking modes.

These did not see much deployment outside the US or maybe Europe.

1G: cellular communications

Back in the late 80s, when AMPS mobile phones (1G) were little more than executive toys, there might not have been much press about, but I’m sure there’d be anecdotal evidence of people being concerned about “radiation”.

If any standard was going to cause problems, it’d have been 1G, since the sets generally used much higher transmit power to compensate for the lack of coverage. They were little more than glorified FM transceivers with a little digital control channel on the side which implemented the selective calling and cell hand-off.

This was the first standard we saw here in Australia, and was the first to be actually practical. Analogue services didn’t last that long, and because of the expense of running AMPS services, they were mostly an expensive luxury. So that did limit its up-take.

2G: voice goes digital

The next big change was 2G, which replaced the analogue FM voice channel and used digital modulation techniques. GSM (which used Gaussian Minimum Shift Keying) and CDMA (which used phase shift keying) encoded everything in a single digital transmission.

This meant audio could be compressed (with some loss in fidelity), and have forward error correction added to make the signal more robust to noise. The cells could handle more users than the 1G services could. Transmit power could be reduced, improving battery life and the sets became cheaper to make and services became more economical.

Then came all the claims that 2G was going to cause us to develop brain cancer.

Now, many of those 2G services started popping up in the mid 90s… has there been a mass pandemic of cancer cases? Nope! About the only thing GSM was bad for, was its ability to leak into any audio frequency circuit.

2G went through a few sub-revisions, but it basically was AMPS done digitally, so fundamentally worked much the same. A sore point was how data was handled. 2G and its predecessors all tried to emulate what the wired network was doing: establishing a dedicated circuit between callers.

The Internet was really starting to get popular, and people wanted a way to access it on the move. GPRS did allow for some of that, but it really didn’t work that well due to the way 2G saw the world, so things moved on.

3G: packet switching

The big change here was the move from “circuits” to sending data around in packets. This is more like how the Internet operates, and so it meant the services could better support an Internet connection.

Voice still went the old-fashioned way, dedicated circuits, since the QoS (quality of service) could be better maintained that way.

The cells could support more users than 2G could, and the packet mode meant mobile Internet finally became a “thing” for most people.

I don’t recall there being the same concern about health as there was for 2G… it was probably still simmering below the surface. Services were deployed further afield and of course, the uptake continued.

4G: bye bye circuit switching

4G or LTE is the current standard that most of us are using. The biggest change is it ditches the circuit switching used in 1G, 2G and 3G. Voice is done using VoLTE… basically the voice call is sent the same way calls are routed over the Internet.

The cell towers are no longer trying to keep a “circuit” connected to your phone as you move around, instead it’s just directing packets. It’s your handset’s problem to sort out whether it heard a given packet already, or re-arrange incoming packets if they arrive out-of-order.

To make this work, obviously the latency inherent in 3G had to be addressed. As a sweetener, the speeds were bumped up, and the voice CODEC could be updated, so we gained wide-band voice calls. (Pity Bluetooth hasn’t kept up!)

5G: new frequencies, higher speed, smaller cells

So far, the cellular standards have largely co-existed in the same frequency bands. 4G actually varies quite a bit in frequency, but basically there are bands from the low UHF around 410MHz right up to microwave at 2600MHz.

Higher frequencies

5G has been contentious because some implementations of it reach even higher. Frequency Range 1 used in the 5G NR standard is basically much the same as 4G, but frequency range 2 soars as high as 40GHz.

Now, in terms of the electromagnetic spectrum, compared to other forms of radiation that we rely on for survival (and have done ever since life first began on this planet), this might as well be DC!

Infrared radiation, which is the very bottom of the “light” spectrum, starts at 300GHz. At these frequencies, we typically forget about frequencies, and instead consider wavelengths (1mm in this case). Visible light is even higher, 430THz (yes, that’s T for tera!).

Now, where do we start to worry about radiation? The nasty stuff begins with ultraviolet radiation, specifically UVC which is at a dizzying 1.1PHz (yes, that’s peta-hertz). It’s worth noting that UVB, which is a little lower in frequency can cause problems when exposure is excessive… however none is dangerous too, you actually need UVB exposure on your body to produce vitamin D for survival!

Dielectric heating

So that’s where the danger is in terms of frequency. I did mention that danger also increases with power… this is why microwave ovens, which typically operate at a fairly modest 2.4GHz frequency, pose a risk.

No, they won’t make you develop cancer, but the danger there is when there’s a lot of power, it can cause dielectric heating. That is, it causes molecules to move around, and in doing so, collide transferring energy which is then given off as heat. It happens at all frequencies in the EM spectrum, but it starts to become more practical at microwave frequencies.

To do something like cook dinner, a microwave oven bombards your food with hundreds of watts of RF energy at it. The microwave has a thick RF shield around it for a reason! If that shield is doing what it should, you might be exposed to no more than a watt of energy escaping the shield. Not enough to cause any significant heating.

I hear that if you put a 4W power amp on a 2.4GHz WiFi access point and put your hand in front of the antenna, you can “feel” framing packets. (Never tried this myself.) That’s pretty high power for most microwave links, and would be many orders of magnitude more than what any cell phone would be capable of.

Verdict: not a health risk

In my view, there’s practically no risk in terms of health effects from 5G. I expect my reasoning above will be thoroughly rubbished by those who are protesting against the roll-out.

However, that does not mean I am in favour of 5G.

The case against 5G

So I seem to be sticking up for 5G above, but let me make one thing abundantly clear, for us here in Australia, I do not think 5G is the “right” thing for us to use. It’s perfectly safe in terms of health effects, but simply the wrong tool for the job.

Small cells

Did I mention before the cells were smaller? Compared to its predecessors, 5G cells are tiny! The whole point of 5G was to serve a large number of users in a small area. Think of 10s of thousands of people crammed into a single stadium (okay, once COVID-19 is put to bed). That’s the use case for 5G.

5G’s range when deployed on the lower bands, is about on par with 4G. Maybe a little better in certain ideal conditions with higher speeds. This is likely the variant we’re most likely to see outside of major city CBDs. How reliable it is at that higher speed remains to be seen, as there’s a crazy amount of DSP going on to make stuff work at those data rates.

5G when deployed with mmWave bands, barely makes 500 metres. This will make deployment in the suburbs prohibitively expensive. Outdoor Wi-Fi or WiMAX might not be as fast, but would be more cost-effective!

Processor load

Did I mention about the crazy amount of DSP going on? To process data streams that exceed 1Gbps, you’re doing a lot of processing to extract the data out of the radio signal. 5G leans heavily on MIMO for its higher speeds, basically dividing the high-rate stream into parts which are directed to separate antennas. This reduces the bandwidth needed to achieve a high data rate, but it does make processing the signal at the far end more complex.

Consequently, the current crop of 5G handsets run hot. How hot? Well, subject them to 29.5°C, and they shut down! Now, think about the weather we get in this country? How many days have we experienced lately where 29°C has been a daily minimum, not a maximum?

5G isn’t the future for Australia

We need a wireless standard that goes the distance, and can take the heat! 5G is not looking so great in this marathon race. Personally, I’d like to see more investment into the 4G services and getting those rolled out to more locations. There’s plenty of locations that are less than a day’s drive from most capital cities, where mobile coverage is next to useless.

Plenty of modern 4GX handsets also suffer technical elitism… they see 3G services, but then refuse to talk to them, instead dropping to -1G: brick emulation. There’s a reason I stick by my rather ancient ZTE T83 and why I had high hopes for the Kite.

I think for the most part, many of the wireless standards we see have been driven by Europe and Asia, both areas with high population densities and relatively cool annual temperatures.

It saddens me when I hear Telstra tell everybody that they “aspire” to be a technology company, when back in the early 90s, Telecom Australia very much was a technology company, and a well respected trail-blazing one at that! It’s time they pulled their finger out and returned to those days.

Jun 142018
 

So, last Sunday we did a trip up the Brisbane Valley to do a rekkie for the Yarraman to Wulkuraka bike ride that Brisbane WICEN will be assisting in at the end of next month.

The area is known to be quite patchy where phone reception is concerned, with Linville shown to be highly unreliable… Telstra recommends external antennas are required to get any sort of service.  So it seemed a good place to take the Kite and try it out in a weak signal area.

3G coverage in Linville, with external antenna.

4G coverage in Linville, with external antenna.

4GX coverage in Linville, with external antenna.

Sadly, I didn’t get as much time as I would have liked to perform these tests, and it would have been great to compare against a few others… but I was able to take some screenshots on the way up of the three phones, all on the same network (Telstra), using their internal antennas (and the small whip in the case of the Kite).  However, we got there in the afternoon, and there were clouds gathering, so we had to get to Moore.

In any case, Telstra seems to have pulled their socks up since those maps were updated… as I found I was getting reasonable coverage on the T83.  The Kite was in the car at the time, I didn’t want it getting damaged if I came off the bike or if the heavens opened up.

I did manage to take some screenshots on the three phones on the way up.

This is not that scientific, and a bit crude since I couldn’t take the screenshots at exactly the same moment.  Plus, we were travelling at 100km/hr for much of the run.  There was one point where we stopped for breakfast at Fernvale, I can’t recall exactly what time that was or whether I got a screenshot from all three phones at that time.

The T84 is the only phone out of the three that can do the 4GX 700MHz band.

Time ZTE T83 ZTE T84 iSquare Mobility Kite v1 Notes
2018-06-10T06:08:16 t83 at 2018-06-10T06:08:16 Leaving Brisbane
2018-06-10T06:09:24 kite at 2018-06-10T06:09:24
2018-06-10T06:09:33 t83 at 2018-06-10T06:09:33
2018-06-10T06:26:17 t83 at 2018-06-10T06:26:17
2018-06-10T06:26:25 kite at 2018-06-10T06:26:25
2018-06-10T07:30:27 t84 at 2018-06-10T07:30:27 A rare moment where the T84 beats the others.  My guess is this is a 4GX (700MHz) cell.
2018-06-10T07:30:34 kite at 2018-06-10T07:30:34
2018-06-10T07:30:39 t83 at 2018-06-10T07:30:39
2018-06-10T07:41:48 kite at 2018-06-10T07:41:48
2018-06-10T07:41:54 t84 at 2018-06-10T07:41:54 HSPA coverage… one of the few times we see the T84 drop back to 3G.
2018-06-10T07:42:01 t83 at 2018-06-10T07:42:01
2018-06-10T07:51:34 t83 at 2018-06-10T07:51:34 Patchy coverage at times en route to Moore.
2018-06-10T07:51:45 kite at 2018-06-10T07:51:45
2018-06-10T08:24:57 kite at 2018-06-10T08:24:57 For grins, trying out Optus coverage on the Kite at Moore.  There’s a tower at Benarkin, not sure if there’s one closer to Moore.
2018-06-10T08:25:39 kite at 2018-06-10T08:25:39
2018-06-10T08:54:28 t84 at 2018-06-10T08:54:28
2018-06-10T08:54:35 kite at 2018-06-10T08:54:35 En route to Benarkin, we lose contact with Telstra on all three devices.
2018-06-10T08:54:39 t83 at 2018-06-10T08:54:39
2018-06-10T09:35:14 kite at 2018-06-10T09:35:14 In Benarkin.
2018-06-10T09:35:22 t83 at 2018-06-10T09:35:22
2018-06-10T10:25:27 kite at 2018-06-10T10:25:27
2018-06-10T10:25:48 t83 at 2018-06-10T10:25:48

So what does the above show?  Well, for starters, it is apparent that the T83 gets left in the dust by both devices.  This is interesting as my T83 definitely was the more reliable on our last trip into the Snowy Mountains, regularly getting a signal in places where the T84 failed.

Two spots I’d love to take the Kite would be Dumboy Creek (4km outside Delungra on the Gwydir Highway) and Sawpit Creek (just outside Jindabyne), but both are a bit far for a day trip!  It’s unlikely I’ll be venturing that far south again this year.

On this trip up the Brisbane Valley though, I observed that when the signal got weak, the Kite was more willing to drop back to 3G, whereas the two ZTE phones hung onto that little scrap of 4G.  Yes, 4G might give clearer call quality and faster speeds in ideal conditions, but these conditions are not ideal, we’re in fringe coverage.

The 4G standards use much more dense forms of modulation (QPSK, 16-QAM or 64-QAM) than 3G (QPSK only) trading off spectral efficiency for signal-to-noise performance, thus lean more heavily on forward error correction to achieve communications in adverse conditions.  When a symbol is corrupted, more data is lost with these standards.  3G might be slower, but sometimes slow and steady wins the race, fast and flaky is a recipe of frustration.

A more scientific experiment, where we are stationary, and can let each device “settle” before taking a reading, would be worthwhile.  Without a doubt, the Kite runs rings around the T83.  The T84 is less clear: the T84 and the Kite both run the same chipset; the Qualcomm MSM8916.  The T83 runs the older MSM8930.

By rights, the T84 and Kite should perform nearly identical, with the Kite having the advantage of a high-gain whip antenna instead of a more conventional patch panel antenna.  The only edge the T84 has, is the 700MHz band, which isn’t that heavily deployed here in Australia right now.

The T83 and T84 can take an external antenna, but the socket is designed for cradle use and isn’t as rugged or durable as the SMA connector used on the Kite.  It’s soldered to the PCB, and when a cable is plugged in, it disconnects the internal antenna.

Thus damage to this connector can render these phones useless.  The SMA connector on the Kite however is a pigtail to an IPX socket inside … a readily available off-the-shelf (mail-order) part.  People may not like the whip sticking out though.

The Kite does ship with a patch antenna, which is about 75% efficient; so maybe 0dBi at best, however I think making the case another 10mm longer and incorporating the whip into the top of the phone so the antenna can tuck away when not needed, is a better plan.  It would not be hard to make the case accommodate it so it’s invisible and can fold out, or be replaced with a coax connection to an external antenna.

If there’s time, I’ll try to get some more conclusive tests done, but there’s no guarantees on that.

May 192018
 

Recently, a new project sprang up on the Hackaday.io site; it was for the KiteBoard, an open-source cellular development platform.  In a nutshell, this is a single-board-computer that embeds a full mobile system-on-chip and runs the Android operating system.  The project is seeking crowd funding for the second version of this platform.

With it, you can build smartphones (of course), tablets, tele-presence robots, or really, any project which can benefit from a beefy CPU with a built-in cellular modem.  It comes as a kit, which you then assemble yourself.  The level of difficulty in assembly is no greater than that of assembling a desktop PC: the circuit boards are pre-populated, you just need to connect them together.  In this version, some soldering of pushbuttons and wires is needed: all through-hole components.  No reflow ovens or solder paste is necessary here, an 8-year-old could do it.

The break-out board for the CPU card features in addition to connections for all the usual cellular phone signals (e.g. earpiece, microphone, button inputs) a GPIO header that follows the de-facto standard “Raspberry Pi” interface, allowing many Raspberry Pi “hats” to plug directly into this board.

That lends itself greatly to expandability.  Want a eInk or OLED notification display on the back?  A scrolling LED display?  A piano?  A games console?  Knock yourself out!  You, are the designer, you decide.  There are lots of options.

I for one, would consider an amateur radio transceiver, an external antenna socket and a beefier battery.  Presently, I get around with the ZTE T83 (“Telstra Dave”), which works okay, but as it runs an old version of Android (4.1), running newer applications on it is a problem.  I believe it could run something newer, but ZTE believe that their job was finished in 2013 when the first one rolled off the production line.

The box did not include a copy of the kernel sources or any link to where that could be obtained.  (GNU GPL v2 section 2b?  What’s that?)

The successor, the T84 is a little better, in fact it has pretty much the same hardware that’s in Kite, but it struggles in rural areas.  On a recent trip into the Snowy Mountains, my phone would be working fine, when my father’s T84 would report “no service available”.  Clearly, someone at Telstra/ZTE screwed up the firmware on it, and so it fails to switch networks correctly.  Without the sources, we are unable to fix that.  Even something as simple as replacing a battery is neigh on impossible, they’re built like bombs: not designed to be taken apart.

I have no desire to spend money on a company that puts out poorly supported rubbish running pirated operating system kernels.  The story is similar elsewhere, and most devices while better in specs and operating system, lack the external antenna connection that I desire in a phone.

Kite represents a breath of fresh air in that regard.  It is to smart phones, what the Raspberry Pi is to single board computers in general.  It’s not only designed to be taken apart, it’s shipped to you as parts.  Apparently with Kite v2, there’ll be schematics available, so you’ll be able to look-up the datasheets of respective components and be able to make informed decisions about part substitutions.  All antenna connections are socketed, so you can substitute at will.

While the OS isn’t going to be as open as one might like (mobile chipset manufacturers like their black boxes), it’s a BIG step in the right direction.  There’s more scope for supporting this platform long-term, than contemporary ones.

As far as actually using Kite, Shree Kumar was generous enough to organise the loan of a Kite for me to test with the Australian networks.  The phone takes up to two micro-SIMs (about 15mm×12mm); one on the daughter card (this is SIM 1) and one on the CPU card (SIM 2).

For the sake of testing, I figured I’d try it out with the two major networks, Telstra and Optus.  As it happens, my Telstra SIM is too big (they call it a “full-size” SIM now; I remember full-size SIMs being credit-card sized), so rather than chopping up my existing SIM or getting it transferred, I bought and activated a prepaid service.  I also bought a SIM for Optus.  I bought $10 credit for each.

As it happens, the Optus one came with data, the Telstra did not.  No big deal in this case.  The phone does have a limitation in that it will talk to one 3G/4G network and one GSM (2G) network at a time.  Given both networks I chose have abandoned 2G, that pretty much means the dual-SIM functionality on this model is severely hobbled.  That said, either SIM can operate in 3G mode, and so it’s simple enough to switch one SIM into 2G mode then activate the other in 3G/4G mode.  So far, the Kite has spent most of its time on Optus.

Evidently Vodaphone still have a 2G network… at least the Kite does see one 2G cell operated by them.  Long term, this is a problem that all dual-SIM phone chipset makers will have to deal with, a future Kite may well be able to do 3G simultaneously on both SIMs, but for me, this is not a show-stopper.

I’ve put together this review of the Kite.  It’s rare for me to be in front of a camera instead of behind it, and yes, the editing is very rough.  If there is time (there won’t be this weekend) I hope to take the phone out to a rural area and try it out with the more distant networks, but so far it seems happy enough to switch to 3G when I get home, and use 4G when I’m at work, so this I see as a promising sign.

The KickStarter is lagging behind quite a way in the funding goal, but alternate options are being considered for getting this project off-the-ground.  Here’s hoping that the project does get up, and that we get to see Kite v2 being developed and made for real, as I think the mobile phone industry really does need a viable open competitor.