Xiaomi Redmi Note 4X (Snapdragon - Mido) - Wifi along with Bluetooth = bad network experience and sporadical Bluetooth connection issues
crok - crok.bic @XDA - crokbic @TelegramThe SoC in the phone theoretically can support 802.11ac (2x2:1)
but the actual SoC in the phone does not support it, it's not built in (it's in WCN3680b) - only 802.11n.
The phone's SoC has a WCN3660B and it has no 802.11ac (in WCN3680B there is).
This is what the phone can do for you 802.11n:
1x1:1 antenna config and thus ^ ^ ^ | | | | | '-- 1 possible data stream | '-- 1 RX antenna '-- 1 TX antenna
- so one antenna, the antenna has a Tx/Rx integrated switch thus (with one antenna) there's no possibility for MIMO, nor beamforming (not even physically possible)
- but that's a 802.11ac feature anyway (and as I mentioned the chip inside does not support it).
- (Note: BT is using the same antenna! You can easily experience the slowdown of Wifi connection along with an active and traffic forwarding BT connection because the internal switch has to switch to BT TX/RX too.)
- Long or Short GI (800ns | 400ns)
- Channel bandwidth: 20 or 40MHz (HT20 | HT40)
All in all: this phone's capabilities are:
Wifi | Freq | Channel | Guard | Max conn speed "type" | | bandw | Interval | (1 stream) ---------+----------+----------+----------+---------------- 802 11g | 2.4GHz | 20MHz | 800ns | 54Mbps 802 11n | 2.4/5GHz | 20MHz | 800ns | 65Mbps 802 11n | 2.4/5GHz | 20MHz | 400ns | 72Mbps 802 11n | 2.4/5GHz | 40MHz | 800ns | 135Mbps 802 11n | 2.4/5GHz | 40MHz | 400ns | 150Mbps
So all your tweaks should be supported on both the phone and the AP (wireless router, AP, whatever) side as well.
Most people say that it was better in MIUI. Indeed, it was and is. When both Wifi and Bluetooth are running at the same time MIUI lets the Wifi work more "aggressively" and Bluetooth still works. Google it how Wifi is dealing with the half-duplex behavior of the media (RF field) and how the backoff timer is working in CSMA/CA. That's the key. The backoff timer works differently and the internal switching (the IC that is swithing between the WLAN and BT circuitry) is quicker.. well not really quicker but let's say optimised. Sometimes this optimisation is the cause of killing the connection (BT beacon starvation during long and high volume wifi traffic consisted of small IP packets, vice versa - but these are atypical for a _normal_ user), so I just want to say that even the MIUI implementation has gaps just most ppl doesn't see it.
You cannot do any better than these with an end device with only one antenna.
Some basics for WLANs:
At carrier freq. 2.4GHz the channels are 5 MHz wide.
40 MHz channel bandwidth means your wifi occupies eight channels, 20 means four.
If you look at the pics linked below (or any other in this search)
you will find out what co-channel interference means
and how it affects your signal-to-noise ratio
(not only the strength of your signal is important
but it's quality/interpretability as well).
https://en.wikipedia.org/wiki/List_of_WLAN_channels#/media/File:NonOverlappingChannels2.4GHz802.11-en.svg
https://www.google.com/search?q=non-overlapping+channels&num=50&newwindow=1&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjMw_j9t6_fAhWFkSwKHafMDwoQ_AUIDigB&biw=1366&bih=641#imgrc=E9Kvq1J3NmrZZM:
So, let's see the G/N channels..
Each channel is 5MHz away from the next channel
and considering using 20MHz channel width
the non-overlapping channels are 20Mhz (+5Mhz guard) away from each other (802.11g/n):
____________________________________________________
| 1 2412Mhz \
| 2 2417Mhz |
| 3 2422Mhz +- << #1 is non overlapping @20MHz channel width
| 4 2427MHz |
\_ 5_2432MHz_/_________________________________________
/ 6 2437MHz \
| 7 2442Mhz |
| 8 2447Mhz +- << #6 is non overlapping @20MHz channel width
| 9 2452MHz |
\_10_2457Mhz_/_________________________________________
/ 11 2462Mhz \
| 12 2467Mhz |
| 13 2472Mhz +- << #11 is non overlapping @20MHz channel width
| 14 2484Mhz |
|____________/_________________________________________
This is only for demonstrational purposes,
only for a better / quicker understanding.
This is why the channels 1, 6 and 11 are called non-overlapping
and you can see that using 40MHz channel width only one range can/will be non-overlapping:
____________________________________________________
| 1 2412Mhz \
| 2 2417Mhz |
| 3 2422Mhz |
| 4 2427MHz |
| 5 2432MHz +- << non overlapping @40MHz channel width
| 6 2437MHz |
| 7 2442Mhz |
| 8 2447Mhz |
\ _9_2452MHz_/_________________________________________
/ 10 2457Mhz \
| 11 2462Mhz |
| 12 2467Mhz | ... .. . and "the rest"
| 13 2472Mhz |
| 14 2484Mhz |
|____________/_________________________________________
This is only for demonstrational purposes,
only for a better / quicker understanding.
Each channel's signals - as you can see - will be interfering with lots of others if you are not careful enough. If you are living in a flat, crowded by other WLAN APs using different channels and those are (more than likely..) overlapping with your 40MHz channel settings.. your RF field is screwed.. and you will experience bad networking even when your signal icon says it's five by five... .. . now you hopefully understand why. And this is why - hell a lot of times - a 20MHz bandwidth setting results in way better and more stable (although lower link speed) connection than a 40Mhz one.
"Normally" if you are using let's say ch6 & 20MHz channel width
it will be overlapping from ch6 to ch10 + (5MHz guard).
That's why we are calling 1, 6 and 11 non-overlapping - channels' bandwidths are not interfering with each other.
Let's say you set ch6 and 40MHz channel width
It will be interfering with all traffic on channels between ch2 and ch10!
It will be overlapping.. Hope you get the math & physics.
If it's overlapping it will make the signal to noise ratio bad.
Even though the signal strength (and the actual wifi icon) will be "strong five by five"
you will experience slowness, packet drops and resendings, timeouts, et cetera..
because of the interferences frames will get lost in transit.
Choose the SSID's channel wisely, crosscheck the environment with the above diagram
and the Wifi Analyser diagram (don't rely 100% on what the Wifi analyser is advising
to be better, 99% of the time it does not consider the thing I'm trying to explain above).
A channel with more SSID but less interference is way better
than a channel with overlapping SSID traffic (interference)
because even though there are probably more devices
and thus presumably the backoff time will be more..
BUT the devices are actually able to SEE each other's frames
and won't cause interference, drops and uninterpretable frames
caused by transmitting at the same time and causing "jamming"
(consider the fact there are a lot of control frames as well, not only IP / user traffic!!)..
Everything is depending on the actual RF environment.
Probably when you are experiencing issues it's simply more crowded,
like more people are using Skype or other kind streaming traffic
(small/large frames at constant rate - that's what it really making busy and killing
the RF environment in terms of Wifi transmission).
It will cause a lot of backoff time, pings even to the first hop - your AP / router
for example - can increase significantly (just Google what is "CSMA/CA"
and you will see why it is important to be able to interpret a frame of other devices).
Setting WLAN data rates and b/g/n compatibility: try to avoid lower data rates,
all WLAN management traffic (beacons, etc) will be transmitted
at the lowest possible data rate to give chance to the lowest data rate device too
to connect and transmit traffic to/from the AP/WLAN router.
Setting "b" compatibility nowadays is actually bad, noone uses "b" at home nowadays
but still a lot of SOHO routers are using "b" for beacons - that will mean
a lot of "airtime" is wasted on devices that will never ever respond
or want to connect and thus it is a built-in "retracting force" of your traffic.
Phones (and most laptops still.. -.-') used to have only one antenna though
so you won't have more than one data stream to and from them.
The things is: you can have a spider-like SOHO router or whatever it looks like
with n+1; n>6 antennas with 3 or 4 radio transcivers.. or anything..
BUT your end-devices have capability restrictions as well,
not just the AP or WLAN router..
If you use 3 end devices in such a situation
all 3 will be able to send and receive at it's max capabilities
but none of them will have the ability to run at the "combined" capability
of the precious and expensive router/AP.. money spent on nothing..
that's just marketing written on the box..
All info is true one-by-one but noone tells the consumers how to interpret it.
Sad but true (it's like RMS power on speakers and amplifiers..).
And the other half of the story depends on your radio environment.
Like if I check the "air" how crowded it is
sometimes I just set a narrower bandwidth (20MHz)
instead of a wider (40MHz) to reduce the possibility of interference
because other "automatic/AI driven" devices will choose non-overlapping channels
(and thus making their signals 100% noise for your traffic, and vice versa..)
and create co-channel interference and always using max. transmit power
to make it even worse (so it will really reach you and harm your signal..
sometimes less is more: smaller "cells" will still work for the owner
BUT not making noisy environment for the others..). And so forth..
Never forget: in a wifi environment (especiall if it's crowded, for example
a flat where possibly 8 neighboring APs/routers are installed as well along with yours)
automatic settings and default settings are always bad.
Check and look around weekly/monthly and adjust your settings,
or ask the neighbors to collaborate - that's the best you can do.
One member on XDA once asked me:
"I never get more than 60mbps of download and upload under the 2.4GHz connected with a link speed of 150mbps.
So, if I lower its bandwidth, will it improve something regarding the signal quality?"
Here's my answer:
60Mbps is quite good actually, considering that it's possible that there are other APs /
routers (we call them "friendly rogue"). TCP is sending data in chunks called a window
and waiting for an acknowledgement to send the next window.
(Google how TCP windowing is working)
If there are drops from the window it will try to recover:
basically by resending the missing piece(s) only (selective ACK)
or resending the whole window again even though there was only one packet missing..
so, imagine
- a crowded environment,
- where there are lot's of neighbors with their own router(s)/AP(s)
- using overlappign and non-overlapping channels as well as
- some of them are using 20MHz channel bandwidth but
- some of them are using 40MHz bandwidth and
- all APs/routers are transmitting at 100% and
- everyone sees everyone else's SSID via beacons... .. .
Google it how much possible throughput reduction will only the control frames
of these APs/routers will create if they are on the same channel
(and yes, that is actually better to be on the same channel
beause if you are on the same channel you can recognise the control frames..
if not on the same channel and it is overlapping channel
it will be pure, uninterpretable noise for your antenna and radio chip..).
Not to mention that some applications are really exploiting the airtime
and will make starve your connection for sure..
(Google carrier-sense multiple access with collision avoidance
and imagine a wireless projector or a TV that is
actually receiving a movie from your PC/laptop
that means constant rate of big packets (frames)
to entertain you with smooth picture).
Another factor here is the transmit energy:
it is limited by the standard (and regulated by the law)
but physics is also funny:
higher freq will mean higher possibility in change of the transmitted symbols
(thus more data at the same time, Google what baud rate is)
but higher freq will mean smaller transmit cell size as well (yeah, radiation..),
so when you go to 5GHz from 2.4GHz with the same transmit power level you will see
that the signal strength will be actually lower and the signal-to-noise much worse,
probably, because lower freq signals are harder to be jammed and
lower freq signals can spread through things more easily then higher freq signals
and less likely will be changed due to reflection, scattering.. et cetera
(oh, boy, I should stop.. I write way too much.. probably too incoherently.)
Please keep in mind and try to act accordingly:
just as others' signal are interfering with yours
your signal is interfering with others', too.
Try not to affect others' network experience ( :
..And why is it sometimes (most of the time.. but that will change!)
things way better at 5GHz - you would ask?
Easy!
Local RF environments today around the 5GHz carrier freq. are not that crowd as around the 2.4GHz carrier freq. and 5GHz has no such natural enemies like 2.4GHz has (Bluetoots.. wristbands, watches, headsets, RF keyboards and mouses.. etc..).