Re: Weak Signal and slow tx Rate with RTL8723AE

[Larry Finger <Larry.Finger@lwfinger.net>]

On 12/04/2013 03:40 PM, David Pinilla Caparrós wrote:
> Hello,
>
> I have mailed with Larry Finger asking for a problem and he has
> pointed me to this list.
>
> I am an Arch Linux User with a Clevo based laptop.
>
> It ships with the RTL8723AE. I have been reading posts around the net
> and found that some people are having problems and talking about the
> driver and something about the RX or TX Power.
>
>
> With the 2 APs wich I usually use I can only reach 18Mb/s of Bit rate
> whatever the signal level or link quality is. Both of them are 802.11
> G and not N I think.
>
> The connection is very unstable. Sometimes powering the wifi off and
> on increases the performance a bit when it's impossible to do anything
> (pings to gateway don't reply)
>
> If they are related to the driver, I would be proud to help with
> anything that I am able to. Testing for example.
>
> I have a recent version of the stable Kernel but I dont know if the
> firmware files are up to date.
>
>
>
> Some data:
>
> 03:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8723AE
> PCIe Wireless Network Adapter
>      Subsystem: Realtek Semiconductor Co., Ltd. Device 0726
>      Flags: bus master, fast devsel, latency 0, IRQ 18
>      I/O ports at d000 [size=256]
>      Memory at f7900000 (64-bit, non-prefetchable) [size=16K]
>      Capabilities: [40] Power Management version 3
>      Capabilities: [50] MSI: Enable- Count=1/1 Maskable- 64bit+
>      Capabilities: [70] Express Endpoint, MSI 00
>      Capabilities: [100] Advanced Error Reporting
>      Capabilities: [140] Virtual Channel
>      Capabilities: [160] Device Serial Number 01-23-87-fe-ff-4c-e0-00
>      Kernel driver in use: rtl8723ae
>      Kernel modules: rtl8723ae
>
>   root  ~  dmesg | grep rtl
> [    2.734124] rtl8723ae 0000:03:00.0: enabling device (0000 -> 0003)
> [    2.749732] rtl8723ae: Using firmware rtlwifi/rtl8723fw_B.bin
> [    2.752940] ieee80211 phy0: Selected rate control algorithm 'rtl_rc'
> [    2.753057] rtlwifi: wireless switch is on
> [ 8838.570486] rtlwifi: wireless switch is o
>
>
>   root  ~  uname -a
> Linux DPini-Laptop 3.12.2-1-ARCH #1 SMP PREEMPT Fri Nov 29 21:14:15
> CET 2013 x86_64 GNU/Linux
>
>
> Iwconfig:
>
> wlp3s0    IEEE 802.11bgn  ESSID:"Pinis_AP"
>            Mode:Managed  Frequency:2.462 GHz  Access Point: 00:1A:2B:12:34:56
>            Bit Rate=18 Mb/s   Tx-Power=20 dBm
>            Retry  long limit:7   RTS thr=2347 B   Fragment thr:off
>            Encryption key:off
>            Power Management:off
>            Link Quality=50/70  Signal level=-60 dBm
>            Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
>            Tx excessive retries:0  Invalid misc:9   Missed beacon:0
>
>   root  ~  rfkill list
> 0: phy0: Wireless LAN
>      Soft blocked: no
>      Hard blocked: no
> 1: hci0: Bluetooth
>      Soft blocked: no
>      Hard blocked: no
>
>   root  ⋯  lib  firmware  rtlwifi  md5sum rtl8723fw*
> ce50dfe07dbb1bfe9e14bdb315a4b28a  rtl8723fw_B.bin
> 69ccaffbe94cc0ef1b89c25290e19b2e  rtl8723fw.bin

Those md5sums match those of the latest firmware.

Your signal is a bit lower than mine. My iwconfig shows

wlp14s0   IEEE 802.11bgn  ESSID:"NETGEAR81"
           Mode:Managed  Frequency:2.437 GHz  Access Point: 20:E5:2A:01:F7:EA
           Bit Rate=7.2 Mb/s   Tx-Power=20 dBm
           Retry  long limit:7   RTS thr=2347 B   Fragment thr:off
           Power Management:off
           Link Quality=60/70  Signal level=-50 dBm
           Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
           Tx excessive retries:0  Invalid misc:2254   Missed beacon:0

My AP is 802.11n. Note that the 7.2 Mbps is misleading. When I pushed data 
through using netperf, it jumped to 72.2 Mbps, and my throughput was

TCP_MAERTS Test:  30.64 27.65 30.54 28.86 33.33 33.59 37.86 39.40 39.76 37.20
RX Results: max 39.76, min 27.65. Mean 33.88(4.22)

TCP_STREAM Test:  35.34 37.34 29.59 20.10 36.11 40.24 40.67 41.93 38.08 33.93
TX Results: max 41.93, min 20.10. Mean 35.33(6.13)

When I switch to an 802.11g AP, I get the following:

TCP_MAERTS Test:  10.77 10.81 11.53 11.69 10.46 10.16 11.04 10.66  7.34 10.90
RX Results: max 11.69, min  7.34. Mean 10.54(1.15)

TCP_STREAM Test:   5.74  6.24  6.76  6.43  7.37  6.23  7.63  7.07  7.07  6.50
TX Results: max  7.63, min  5.74. Mean  6.70(0.55)

Those numbers could probably be improved, but without any details on how the 
chip works, what could one do. Messing with power settings on the amplifiers 
could lead to destruction of radios. I cannot take that chance.

As to stability, I am in the middle of a long-term test of rtl8723ae. After 
roughly 86,000 seconds of connect time, I have had only 9 disconnections, and 
all were due to a bug in the roaming code that I have so far been unable to 
find. The interface thinks it has lost the APs beacons, does a disconnect, and 
immediately reconnects. Otherwise, the connection was stable until I forced a 
reconnect to my G AP for this reply.

Unfortunately, I have no idea what to do for your complaints. If you want higher 
throughput, then an 802.11n AP seems warranted.

Larry