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Motel75 (Offline)
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Default 13-09-2013, 08:07

I've got a Samsung Galaxy S Duos S7562, but find it exceedingly limited. (It's not my main phone, thankfully - I generally much prefer Windows Phone, but there isn't a dual-SIM WP available yet.) It has only 4 MB of internal memory, of which less than half is available, but you can't store apps on the SD card. This makes it semi-useless for things like navigation. Only one SIM may use UMTS. And the phone makes it difficult to dial a number stored on one SIM using the other SIM. It's also relatively slow (single-core 1 GHz processor). But the camera is OK, and it can be sometimes had for around 130 euros.


Current DE: Vodafone, Netzklub; PL: Klucz, Virgin; UK: Giffgaff; US: T-Mobile; IT: Vodafone; UA: Kyivstar; FR: Bouygues; GR: Vodafone
Former DE: Vodafone, T-Mobile, O2, Blauworld, 01051mobile, Solomo, Lycamobile, Simyo, Congstar, Fonic, Edeka Mobile, Lidl Mobile; PL: Heyah, Era, Virgin, Sami Swoi, Orange, POP, iPlus, Carrefour Mova, Telepin Mobi, Play, Lycamobile, T-Mobile; UK: Vodafone, T-Mobile, Virgin; US: T-Mobile, AT&T, Lycamobile; CZ: Vodafone, Oskar; ES: Lebara; GR: Vodafone, Wind; UA: Vodafone; IL: Orange; TR: Turkcell
   
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inquisitor (Offline)
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Default 14-09-2013, 17:53

Quote:
Originally Posted by rfranzq View Post
Well, if you had not started this interesting thread you [and we]
would not have found out this important bit of info---and have prevented much sim-swapping.
Could this be seen as a battery-saving feature?
'It's a feature and not a bug.'
The fact that only one radio module supports UMTS definitely saves battery life as UMTS - despite significantly lower transmission power levels (max. 0.25W vs. 1-2 for GSM) - requires a lot of CPU power for the spreading codes calculations which results in higher power consumption by the baseband processor. Besides impairing standby performance a second UMTS radio module would also increase hardware complexity and - most importantly - production and royality expenses. Further to that simultaneous UMTS support for the second SIM would also be quite pointless to most users as the most relevant advantage of UMTS is its higher data bandwidth but establishing a simultaneous second data session is useless. Instead most users will use the second SIM only for voice and SMS for which GSM still works fine as long as GSM and UMTS coverage are overlapping. However since there are UMTS-only networks without overlapping GSM coverage as a fallback option and since more and more operators are reducing GSM capacity by refarming former GSM spectrum in favour of UMTS or LTE deployments UMTS support for the second SIM is becoming a necessity.
Has anybody actually seen any dual SIM device with dual UMTS support yet?


terminals: Samsung: Galaxy S5 DuoS (G900FD); BLU: Win HD LTE; Nokia: 1200; Asus: Fonepad 7 ME372CG; Huawei data: E3372, Vodafone R201, K3765, E1762;
postpaid: O2 on Business XL; prepaid: DE: Aldi Talk, Lidl; UK: 3; BG: MTel, vivacom; RU: MTS; RS: MTS; UAE: du Tourist SIM; INT'L: toggle mobile
VoIP: sipgate.de (German DID); sipgate.co.uk (British DID); ukddi.com (British DID); sipcall.ch (Swiss DID); megafon.bg (Bulgarian DID); InterVoip.com
   
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DRNewcomb (Offline)
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Default 14-09-2013, 19:22

Quote:
Originally Posted by inquisitor View Post
Instead most users will use the second SIM only for voice and SMS for which GSM still works fine as long as GSM and UMTS coverage are overlapping. However since there are UMTS-only networks without overlapping GSM coverage
Japan and S. Korea come to mind.
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UKSTEVE (Offline)
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Default 17-09-2013, 17:37

I have a Star W007 (for sale - see for sale on here).

It's to stop any signal conflicts - one SIM is on 3G, the other on 2G - means they can both have best signal reception/transmission conditions. If two 3G handsets are in close proximinity, the spread spectrum nature of the signals means you get a lot more bad packets.

It's a clever solution to the problem of using two 3G transceivers in close proximity.

The Star W007 is software-switchable in this regard - i.e. you can switch which transceiver module pairs with which SIM card.

+Steve


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Home mobie: Telefonica O2
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inquisitor (Offline)
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Default 18-09-2013, 21:59

Quote:
Originally Posted by UKSTEVE View Post
It's to stop any signal conflicts - one SIM is on 3G, the other on 2G - means they can both have best signal reception/transmission conditions. If two 3G handsets are in close proximinity, the spread spectrum nature of the signals means you get a lot more bad packets.
If it actually was a problem to establish two separate radio links on adjacent UMTS frequencies from the same handset how could DC-HSPA work which does just the same to increase bandwidth? Integrating two 3G radio modules may be a cost-related problem for budget phones but I think there's no major technical issue at all.
Also keep in mind that the 5 MHz channels of UMTS include guardbands of 580kHz at the upper and lower end. So the actual carrier bandwidth of a UMTS channel is only 3840kHz and all carriers are separated by 1160kHz which should suffice to avoid interferences.


terminals: Samsung: Galaxy S5 DuoS (G900FD); BLU: Win HD LTE; Nokia: 1200; Asus: Fonepad 7 ME372CG; Huawei data: E3372, Vodafone R201, K3765, E1762;
postpaid: O2 on Business XL; prepaid: DE: Aldi Talk, Lidl; UK: 3; BG: MTel, vivacom; RU: MTS; RS: MTS; UAE: du Tourist SIM; INT'L: toggle mobile
VoIP: sipgate.de (German DID); sipgate.co.uk (British DID); ukddi.com (British DID); sipcall.ch (Swiss DID); megafon.bg (Bulgarian DID); InterVoip.com
   
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UKSTEVE (Offline)
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Default 20-09-2013, 17:21

DC-HSPA is - I think - only in Release 8 version at the moment Mr I - all is does is to double the data rates by doubling the bandwidth to 10 MHz (25 MHz).

In theory, DC-HSDPA can support up to 42.2 Mbps, but unlike HSPA, it does not need to rely on MIMO transmission. This is the key.

My understandng is that Release 8 of DC-HSDPA can only operate on adjacent carriers, whilst Release 9 will allow the paired cells to operate on two different frequency bands. I was talking to a Three tech recently who said the carrier is testing Quad Channel - QC-HSPA!

Obviously the spread spectrum nature of 3G / DC-HSPA in this context will result in packet quality degradation, but since it's one handset and one cell site controlling everything, it's not a MAJOR problem.

What I was trying to say - sorry I didn't express myself clearly - is that two 3G transceivers placed side by side would hit packet quality problems - and since we're talking about handsets that are designed cheaply and based on older chip sets, having one 3G and one 2G transceiver in the same handset avoids any problems - and it's cheaper

+Steve


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PO Box 1014, Sheffield S10 5YG, UK

Home mobie: Telefonica O2
Other UK mobiles: 3, Vodafone, Virgin

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RTuesday (Offline)
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Default 26-09-2013, 05:10

Quote:
Originally Posted by inquisitor View Post
I appreciate your thoughts and recommendations on these and further Android dual SIM handsets.
I've been using the Sony Xperia Tipo ST21A2 as my primary phone for about 8 months now. I paid US$138 for it (~ 100), new.

http://www.amazon.com/Sony-Dual-SIM-.../dp/B0093HKO2U

+ cheap (~ 100)
+ changeable battery
+ quadband GSM
+ triband UMTS (850/1900/2100 MHz) (so no 900 3G for Europe)
(note: the ST21i2 has 900/2100 instead)
+ very good battery life
+ normal size mini sims
+ Android 4.0 ICS
+ microSD slot up to 32GB
+ standard micro-USB for charging
+ small
- small low-res screen
- no front-facing camera
- no magnetometer (electronic compass)
- poor camera with no autofocus
- touchscreen could be more responsive

Not a perfect phone, but for the price it's been very useful, especially with the battery lasting for days of travel. Like virtually all these phones, only one SIM can be on 3G at a time (but it can be either sim slot).

Having said that, I'm considering changing it. It's nice and small and light, but this means the screen is just a bit too small, harder to read and more difficult to touch in the right places. But as you know there's not much else out there, at a sensible price. Dual sims are very useful to me (quad sims would be great, I currently have a second plain GSM dual sim phone for the others).


Sims: Telcel MX, T-Mobile US, Virgin Mobile UK, Orange UK, Knowroaming
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petkow (Offline)
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Default 11-04-2014, 13:20

Hello everybody. I just thought I would reawaken this oldish thread as my current multi-handset setup used to work perfectly well up until a few days ago when a rather unfortunate incident of a bottle breaking in my bag left one of those phones covered in rather nice brandy and rather dead!

Has anyone got any recent experiences with any half-decent dual-SIM or triple-SIM android phones?

In the dual-SIM world, I have been particularly looking at the Zopo C3 and how it weighs up against the C2 that Inquisitor has already reviewed above. I am not sure if it is worth the extra money though.

I still like the look of the Zopo C2 and see that it is currently around 168 = 200 Euros (e.g. http://www.amazon.co.uk/gp/product/B00FS99CT8) As far as I can tell, these now come with normal Android and not the Alyiun OS. However, it is a bit confusing as the title of that product suggests 1.2 Ghz quad processor and later in the spec it says 1.5. Then there is the Zopo C2 Platinum which costs a bit more and has same spec again.
So confused!

Quote:
Originally Posted by inquisitor View Post
[list][*]Zopo C2/ZP980
The Zopo ZP980 and C2 share identical hardware, but the later comes with Alyiun OS, a Chinese fork-off of Android, preinstalled which makes it slightly cheaper due to subsidies
+ 5" 1080p IPS screen
+ MTK6589(T) quadcore CPU with up to 1.5 GHz (other versions come with 1.2 GHz)
+ up to 2GB RAM/32 GB ROM (other versions come with 1GB/16GB or 1GB/4GB)
+ microSD slot
+ neat iPhonish design
+ UMTS support for both SIM cards
+ changeable battery
- limited UMTS frequencies and odd frequency combination (850 & 2100 MHz)

Last edited by petkow; 11-04-2014 at 13:37..
   
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petkow (Offline)
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Default 11-04-2014, 14:24

Upon reading more about Zopos I think their newest offering is actually the ZP998 which has a whopping 8 cores! I see it is available for around 219 Euros. http://chinamobilemag.com/zopo-zp998...tphone-review/ Interestingly, this one is confirmed to have 3G radio modules for both SIMs. I am sure the 8 cores are significantly helping with that.

Last edited by petkow; 11-04-2014 at 14:33..
   
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Bossman (Offline)
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Default 11-04-2014, 16:58

The Moto G dual sim is not bad - http://www.amazon.com/gp/aw/d/B00I34...&robot_redir=1


Phones: ASUS zenfone 3, Nexus 4, Lumia 650 dual sim
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