Number of streams in mobile tablets/smartphones

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Many 802.11ac-capable tablet and smartphone devices appear to be using 80MHz channel widths, but only one spatial stream. This is due to battery consumption issues I believe.

Do you know of any tablets or smartphones that are planning to use two streams that are in the works (maybe that have new, lower power chipsets that allow them to use 2 streams)? Or, will one stream be the limit for these types of devices?

Nigel.
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Nigel Bowden

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Posted 5 years ago

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Nick Lowe, Official Rep

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Good question. I wonder if they could adopt a more flexible, dynamic approach based on remaining battery life and TX power required to get to the AP.
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Craig Mathias

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I think single-stream will be common for handsets, mostly because configuring multiple antennas in such a small form factor is difficult (although it can be done), and because of the power-consumption issue you mention. Two-stream tablets are very likely; they have enough physical space and room for a larger battery.

Still, single-stream performance of 450 Mbps is quite impressive and should be more than sufficient for the next few years.
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Matthew Gast

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The biggest power sink in 802.11 MIMO is not the power amp, but the DSP required to put 2+ streams on to the same channel. By having only one stream, there's no DSP required and that alone dramatically reduces power consumption. Antennas are hard, too, especially in a smartphone that needs to have WAN and Bluetooth antennas in addition to Wi-Fi.
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Nick Lowe, Official Rep

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Thanks! Does this preclude a dynamic approach based on remaining battery life?
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Matthew Gast

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Yes, it does. Even having the DSP on board means you have to run it (or at least keep it in standby ready to run). The only practical way to prevent the power drain is to not put the DSP in the circuit to begin with.