Have you ever wondered why your smartphone delivers faster speed on the Downlink VS the Uplink?

Smartphone Speedtest.png

Have you asked yourself this question?  Do you know the answer?  If you were to ask this question at a family gathering, or with friends around a meal, I bet you would get some very interesting speculative answers.  Well, I have done asked the question, and the answers were quite interesting.  Here are some of the most interesting answers I received:

  • It is because there are too many people on the network.
  • The service provider must be throttling me
  • It is probably because of my cellular plan.
  • The service provider does it on purpose, so we do not stream from our phone or USB sticks, as they want us to get a landline for that.
  • The Service provider knows that I listen to more music than I talk.
  • My phone is getting old; I should change it!

Well although none of the above is the real technical reason, there is a bit of truth in some of them.  The fact is that the main reasons are both technologic and economic ones.

From the technical perspective, the main reason is that the UE’s (user equipment) are pretty much all fitted with a SISO radio on the transmit side.  SISO stands for Single Input and Single Output; this means that your LTE smartphone only uses a single transmitter when it is talking to the tower site.  However, your smartphone, the very same unit, is fitted with MIMO on the receiver side.   MIMO stands for Multiple Input and Multiple Output.  Meanwhile, the tower sites are fitted with MIMO transmitters and receivers, so quite simply, since tower site equipment is emitting on multiple radios to connect to your phone it can transmit more information in the direction of the phone.  However, the phone can only transmit on a single transmitter, hence the lower capacity.

From an economic perspective, the new smartphones are now already fetching USD$1,000, and they are only SISO on the uplink.  Ask yourself, would I pay even more money for a MIMO uplink smartphone, so that I can have a more symmetrical throughput?  Perhaps a few of you would, but then your smartphone battery life would also be greatly affected.  Would you be ok with that?

When looking at it practically, do we need more capacity on the uplink for our smartphones?   Not really, what application or use case would drive the added capacity requirement on the uplink?   The fact is that from any smartphone we spend more time downloading than uploading. It may be different from a USB stick or a mobile router with an LTE built-in capability.  Perhaps it would be useful to have it there, and yes, it is coming.   After all the mobile routers are usually connected via an AC outlet or the DC power available in the vehicle, so battery life is not applicable in these cases.

So, the next time you are with family or friends, try it!   Ask them the question, and see if you receive similar answers to what I received.


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