Dual-SIM - Does using 2 SIM cards affect the perceived network performance?

[jassingh]

More a technical thing about using Dual-SIM phones and the potential impact on speed/network performance, and something I observed recently.

Before I moved to Smarty, I spent a few weeks using a Three SIM card in my Android dual-SIM phone to test out the coverage and signal in areas where I work, live and travel to. Having been happy with the performance, ordered the Smarty plan I wanted, activated and then used that for an additional few weeks and again kept an eye on performance and used a few signal apps to get the lowdown on coverage and how it changed compared to my other provider. I was happy to move from Vodafone anyways given the increase in costs (~14%) for a mere 5GB of data each month, on a 4G-only plan. Doing this kind of testing helps "flush out" potential issues (at home, at work, on the go) before you commit, saving you potential headache.

I used to be with iD mobile (also runs on Three), when it first launched, for few years before that so I already had in mind what kind of experience I would get, but networks are constantly improving these days. The dual-SIM test method also saved me carrying two phones (which I used to do in the past). More recently, I had my number ported and all went smoothly without a hitch, so it was time to boot that Voda SIM out of my phone.

Once I did that, I noticed that the signal from the Smarty SIM has been brilliant - and even better than when I was using the 2 SIMS together. Phone feels more responsive (especially on 5G which seems to be full-pelt!!) - web pages, videos, apps load significantly faster. This is in the same location, and even when I have been out and about I haven't noticed any slowdowns - I never had any issues previously either. Not to mention, better battery life since less drain using 2 radios(?) at the same time, so that is good.

I know that it's also important to place the SIM in the right slot e.g. on many phones only the SIM1 slot supports 5G etc, but the bands/frequencies used by the SIMs can sometimes be a 'shared resource' which perhaps would impair or degrade performance. Meaning what you're seeing is not necessarily representative of the actual network performance compared to, say, using that SIM in a (comparable spec) Single-SIM phone?

Another part of me says, as the SIM slots are unique, the phone is usually free to use whatever bands/frequencies necessary at the cost of hardware resource.

Of course the main point of a Dual-SIM phone is for that extra flexibility who need to use two different networks so for most people I assume its not something they care about, or you may only find yourself using dual-SIM capabilities when considering moving to another network or you go on holiday abroad and use a local SIM there for a short time .. in such cases it gave me something to think about.

We also now have eSIM phones in the mix but I am not sure if the same would apply to that method too - if anyone has any experience of this I would be interested to know!

Can using/testing two SIM cards simultaneously affect the network speed and perceived performance on your phone?
Perhaps for the most accurate test of the network, it's better to use a single SIM in different phones for comparison?
If the performance seems slightly degraded when using 2 SIMS in a phone - does that necessarily reflect on the performance of the network, or that is the nature of Dual-SIM phones?

The answer is probably not going to be straightforward one since every phone, chipset and specification out there varies. 

Interested to see if anyone has any thoughts on this?

[Strandloper · Accepted solution]

@jassingh,

Any slowing of the phone should be perceived, and probably minimal in a dual SIM phone. From my understanding the dual SIM phone will use slightly more battery as it is monitoring two SIMs for incoming calls and texts, and also uses algorithms to choose which SIM to use for making calls and texts (although this will be often have user input to decide or ask for your input).

Certainly my experience of a dual physical SIM phone quite a few years ago, I could decide to use both SIMs, or just one, depending on respective signal strengths at the time, occasionally checking the signal of each SIM.  This was in the days of being an advenced skills first aider for SJA in Surrey, and often encountering variable signal strengths when on duty.

[JJP2 · Accepted solution]

I agree with @Strandloper any reduction in speed / performance should be minimal.

I have used various android dual sim phones over the years, and now have an iPhone 13 mini. 

Naturally, the physical sim slot is used by my Smarty physical sim and the eSIM slot is used by a variety of eSIM’s, of which the iPhone can store 8 eSIM profiles.

Personally, I think dual SIM phones are very useful, especially when travelling.

[Strandloper · Accepted solution]

@jassingh,

Any slowing of the phone should be perceived, and probably minimal in a dual SIM phone. From my understanding the dual SIM phone will use slightly more battery as it is monitoring two SIMs for incoming calls and texts, and also uses algorithms to choose which SIM to use for making calls and texts (although this will be often have user input to decide or ask for your input).

Certainly my experience of a dual physical SIM phone quite a few years ago, I could decide to use both SIMs, or just one, depending on respective signal strengths at the time, occasionally checking the signal of each SIM.  This was in the days of being an advenced skills first aider for SJA in Surrey, and often encountering variable signal strengths when on duty.

[JJP2 · Accepted solution]

I agree with @Strandloper any reduction in speed / performance should be minimal.

I have used various android dual sim phones over the years, and now have an iPhone 13 mini. 

Naturally, the physical sim slot is used by my Smarty physical sim and the eSIM slot is used by a variety of eSIM’s, of which the iPhone can store 8 eSIM profiles.

Personally, I think dual SIM phones are very useful, especially when travelling.

[Chalkychap · Accepted solution]

I'm with @Strandloper and @JJP2 on this - you'd expect any speed / performance hit to be minimal. 

I'd guess without some benchmarking, to test different scenarios in a dual-SIM system handset, one's own experience / observations could be somewhat subjective. 

I reckon dual-SIM devices are great for roaming, and have helped me avoid large roaming charges when I've been somewhere that prohibits use of my SMARTY plan allowances.

[AndrewP_1422753]

It's likely that with a dual-SIM physical phone (that is, with 2 x physical SIMs) - the phone will use more processing power managing both SIMs compared to one, which may appear as slow down, particularly if the processor used in the phone is older. Multi-SIM phones i.e. those with eSIM capability, can manage multiple logical SIMs but as these are usually only available on newer phones with better processors, any visible speed issue on the User Interface, would be reduced.