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Current Infrastructure

I am doing network configuration at my place and I am trying to understand and/or figure out a few things. So basically I have two routers at my place where one acts as the primary router (Wireless N300) and other (Wireless N300 + AC433) acts as a Access Point (They are connected by a LAN cable and not by wireless connection). Multiple devices connect to both of these routers through wireless connections of which most use 802.11n except few which use 802.11ac.

Issue

So here are my issues:

  • My notebooks both have a Wireless-N 2x2 adapters. The maximum link speed they can get on my primary router 150 Mbps as against that of 300 Mbps on my AP (Mind you both are only on Wireless N and not on Wireless AC). Why is there a difference in-spite of both being N300 routers?
  • Other question is about my mobiles devices which run on both N and AC. For Wireless AC, the devices catch the complete link speed ie. 433 Mbps however for Wireless N, these devices get only a link speed of 72 - 75 Mbps which is nearby 1/4th of the N300 speed. Why does such difference incur in link speed? Does this have anything to do with lowest device speed or similar sort of phenomenon?

I read a lot of things on internet regarding MIMO, MU-MIMO (which none of my devices are compatible of at present), dual-band, etc but nothing seems to clear my doubt. Hence the question here.

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Apologies if I go over anything you already know =). Also, if you don't already have one, I recommend Acrylic WiFi Home (free) as a good home network scanner.

But to the questions...

My notebooks both have a Wireless-N 2x2 adapters. The maximum link speed they can get on my primary router 150 Mbps as against that of 300 Mbps on my AP (Mind you both are only on Wireless N and not on Wireless AC). Why is there a difference in spite of both being N300 routers?

So we are all clear on this, because a device has a theoretical maximum speed, it does not necessarily mean that device is always attempting to operate at that maximum speed.

Likewise, having a 2x2 adapter does not guarantee ~300 Mbps on Wireless N. For that you need two spacial streams (2x2), a 40 MHz (effective) channel bandwidth, and a short guard interval (short GI - about 400ns). Bandwidth is the key here. 2x2 and a short GI with a 20 MHz bandwidth channel will only net you ~144 Mbps or less.

Possible Issues

In general, possible reasons for the speed disparity between these devices include:

Settings - Wireless devices frequently have settings which allow the theoretical maximum transmission speeds to be set (e.g. ~150 or ~300 Mbps for Wireless N). One or more of your devices may not have this set correctly.

Image Of Router Speed Settings

Interference/Attenuation - These can cause aggressive throttling and packet loss (both bad for speed). Packet loss comes from direct signal interference or signal attenuation (weakening), while throttling is due to frequency congestion and the fact that wireless connections have no packet collision detection (so devices must be extra careful when sending data in "busy" wireless environments).

Interference sources include:

  • Spurious interference from other nearby electronics (e.g. cordless phones, other WiFi networks, your microwave) (packet loss or erroneous throttling).

  • Devices waiting for other (genuine) devices. This could include having too many wireless devices hooked up to one router or devices operating on the same WiFi channel(s) (throttling).

Attenuation sources include general distance between devices and physical structures (windows, walls, doors, floors, etc.). Low power output can also have a negative impact (this can sometime be overcome in device settings).

Channel Bonding - The "40 MHz" channel bandwidth needed for ~300 Mbps on Wireless N is frequently achieved via channel bonding (using two 20MHz bandwidth channels at the same time). If one of those channels is unreliable (due to interference, etc.), ~300 Mbps cannot be achieved (most devices fall back to using a single 20 MHz channel).

Hardware - Devices sometimes just simply do not support ~300 Mbps, especially when operating on 2.4 GHz. This can be due to age of the device, poor quality components, regulatory adherence, over-cautious programming or other interoperability issues.

[My] [o]ther question is about my mobiles devices which run on both N and AC. For Wireless AC, the devices catch the complete link speed ie. 433 Mbps however for Wireless N, these devices get only a link speed of 72 - 75 Mbps which is [nearly] 1/4th of the N300 speed. Why does such [a] difference [occur] in link speed? Does this have anything to do with lowest device speed or similar sort of phenomenon?

The only time I ever personally see speeds that low is with extreme signal attenuation (weak signals). My guess would be low-power mobile devices vs. long distance with lots of obstacles (and yes, Wireless AC will reach places Wireless N will not).

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  • "Wireless AC will reach places Wireless N will not"? This is outright wrong as far as I understand. 5GHz will almost always attenuate faster than 2.4GHz.
    – Aron
    Jun 26 '17 at 3:37
  • Apologies. I probably just worded this poorly. To your point, theoretically, yes. But "beamforming" built into the AC spec, device power overall, antenna design and real-world interference all play a role as well. The net result is that (at least in some instances) devices using AC can "shout" at each other better than devices that use N, even on 2.4 GHz. Jun 26 '17 at 10:18

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