Fancy a new iPhone 5C or 5S? READ THIS or you may not get 4G data Apple might have launched two new iPhone models on Tuesday, but it launched 10 different variants as Cupertino struggles to cope with the hugely fragmented 4G market. Where a GSM phone might be dual-band or the frequent flyer might shell out for a quad-band handset, Apple's latest phones each come in five variants: two hendeca …
They already use SDR
But you can't "software" define sensible physical aerials nor decent full duplex filters.
SDR lets you easily have any bandwidth (within constraints of aerial, duplex filter, RX LNA and TX PA) and any scheme of modulation (QAM, APSK, COFDM, CDMA etc as used by GSM, CDMA-1, EDGE, 3G, HSPA, WiMax, LTE). SDR isn't really any help at all in doing different bands. You need different physical components.
Good. The SDR marketers make promises that Physics 101 can't keep. I've attended military radio conferences since the 1990s where SDR was pushed as The Next Big Thing. Look up how screwed up the JTRS program is; freaking multi-billion dollar disaster area. Because those leading it were stupid and uneducated.
OF COURSE -> SDR has perfect application in the I.F. strip - for both receive and transmit. Friggen perfect - as long as the code weenies have some oversight by somebody that actually knows something about radio. Like not assuming that other stations are exactly and precisely on frequency, directly sampling at fc and being confused why there's a beat note when receiving AM. Duh.
Those touting SDR need to be viewed with deep suspicion as they have a long history of false claims. Their behaviour has cost billions of dollars.
But surely they can software define the range that the radio needs to look for to pick up the signal , based upon is geographical location?
I assumed that the frequencies are like using different parts of the FM spectrum, so surely your should be able to software tune the phone to the correct frequency, rather than making hardware that can only look at a particular frequency or am I missing something ?
You are missing something. While tuning is possible over a certain range of frequencies, you can't use the same hardware for all of them. Tuning only gets you so far, and becomes less and less efficient when you go away from your centre wavelength.
Hence the reason you had AM and LW and SW on your old radio; They're the same type of modulation, but the frequencies and bandwidths differ so much that a single circuit would become uselessly ineffective if detuned far enough to receive them all.
I suppose the its down to cost then. Radios used to have all the hardware installed and you pushed a button to select, something a GPS system might do for you in this case.
Apple used to be the king of simplicity who cared not for cost. Now we have a bean counter in control and its going wrong.
"...based upon geographical location..."
My iPhone 4S spent a month in Asia. When I landed back in North America, it steadfastly refused to find the Rogers network. I hard reset it, and it still couldn't find the network. It was however looking for location using (probably) GPS.
It wasn't having much luck with the GPS for the simple reason that I WAS DEEP INSIDE THE MADE-OF-METAL TERMINAL BUILDING.
Point being, geographical location is often unknown (by the phone) in the precise location where you'd need it most (having just changed continents, thus 99.99% odds of being inside an airport terminal building).
So I gotta wonder why you can't just have one damned phone variant with its SDR chippery, and have the thing scan around until it goes "oho, there be mobile signals in these bands"?
Maybe two variants if regional frequency variations are so wide that you need separately tuned antennae, but really, ten?
It does do that within for example the 800MHz band to find the various signals for the 4 mobile operators in the UK, however you need different chippery to receive the signals owned by the 3 operators that have signals in the 2.6Ghz band.
SDR means you it can find both 2G and 3G signals in the 900MHz band and both 2G and 4G signals in the 1.8GHz band with two sets of chippery rather than 4, but for different frequency bands a long distance apart, you still need separate chippery to receive the signals.
I think in the UK this problem is remedied by the fact you can't get 4G data anyway - unless you're in the centre of a major city, on a certain carrier, and have vast quantities of disposable income to shell out on astronomical data charges. Watching re-runs of Top Gear in HD on my mobile phone sounds like fun, but not at any cost.
Very true, but here's a perfected revision:
I think in the UK this problem is remedied by the fact you can't get 4G data anyway - unless you're in the centre of a major city, on a certain carrier, and have vast quantities of disposable income to shell out on astronomical data charges. Watching re-runs of Top Gear in HD on my mobile phone sounds like no fun, at any cost.
The AT&T "4G" HSPA+ works great where I live, I often get over 10Mb/s from it. So the fact I don't have LTE where I live yet is totally irrelevant to me, because I don't see any point to more speed than that. The only time it matters is when a football game drives up the local population by 50% and the cell sites start to become overwhelmed.
If I find 3G at a comparable speed when traveling, I certainly won't care if my phone can't access the local flavor of 4G - especially since I'd likely turn off mobile data entirely and rely only on Wifi for data because international roaming data prices are so ridiculous.
It is funny how the world seemed to agree pretty widely on 2100 MHz for 3G, but is so fragmented when it comes to 4G.
Does this mean that the current generation of Freeview boxes / tuners in existing kit are looking at a life expectancy of four years, tops? I am aware several places have had issues with Freeview following the introduction of 4G, but I thought that was a 'tell the box to rescan' job.
the use of 800MHz for 4G can mean problems for boxes without decent filters...the at800 group are providing filters to stop these signals interfering (if your Freeview signal uses the channels near 800MHz you're more likely affected. retuning wont help if the signal you want is at eg 792MHz! ;-)
however the proposals that have been put forward are to squeeze the frequencies used by freeview and to take away the 700-800MHz range - giving it to 4G/LTE instead. this would require some more remapping of main broadcast antennae and set-top boxes would have to be re-tuned to use the new channels - the knock on effect may be less channels on freeview in total...less HD content etc - OFCOM want the UK population to shift to getting content via broadband(!)
Yes. It does mean that. Not because of frequencies, but because the limited spectrum available after release of '700 MHz' won't be enough to reconstruct the services we have now, at their current coverage levels, unless the newer DVB-T2 standard and AVC/H.264 compression is used for many more of the services.
If you have Freeview HD equipment, you'll be fine. Any non-HD gear quite possibly won't work, or won't receive all SD services, after this band is released. You should check that any new equipment has the 'Freeview HD' logo (YouView equipment is fully DVB-T2/AVC compatible, but doesn't fully implement IPTV in the same way as the Freeview HD logo now requires, so can't have the logo).
If the decision to switch to DVB-T2/H.264 isn't taken, then it should just be a case of retuning the box. It'll still scan channels 49 to 69, it just won't find anything up there.
Personally, I don't think the case has been made for release of this band. It seems to suffer from circular reasoning: the predicted demand for bandwidth comes from demand for linear TV on mobile devices, so we have to turn off the current linear TV broadcast in order to make space to send it over an inferior protocol?
Ze beatings will continue until morale improves!
Also, you say that you cannot change the laws of physics. However, after a few hours with me and this cattle-prod, you will be singing a very different tune. Soon, all will be resolved, and I'll have you providing unicorn steaks for the canteen as well.
The problems with 4G frequency bands, channel allocations and radio's, is going to be the same for all handset manufacturers. The focus on Apple isn't particularly helpful. The basis of the article shows that phones that will be capable of operating outside of their native home region on 4G are going to be very thin on the ground for a while; so don't think that you'll be able to buy an unlocked phone abroad and it to work at home on anything other than 3G.
The iPhone specific part of this that is relevant to the UK/EU is that the variants being sold here (iPhone 5s Model A1457) only support LTE (Bands 1, 2, 3, 5, 7, 8, 20) of which only the following applies to the UK:.
Band 3: 1.8-Ghz - EE, 3
Band 7: 2.6-Ghz - Vodafone, EE
Band 20: 800-Mhz - O2, Vodafone, 3, BT
Obviously, the EE network on Band 3 currently has the most coverage.
What is also interesting with respect to the iPhone 5s is the caveat on the Carphone Warehouse site: "SIM free iPhone 5s will lock to the network of the first SIM used."
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