[FS#1373] Linksys E1700 wireless unstable and jams other WiFi channels with LEDE

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Matt (mjcmatrix) 

Attached to Project - OpenWrt/LEDE Project
Summary - Linksys E1700 wireless unstable and jams other WiFi channels with LEDE
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Critical
Priority - Very Low
Reported Version - lede-17.01
Due in Version - Undecided
Due Date - Undecided
Details - Device: Linksys E1700 (dual antenna, 2.4Ghz only)
Techdata:  https://openwrt.org/toh/hwdata/linksys/linksys_e1700
LEDE firmware installed: lede-17.01.4-ramips-mt7620-e1700-squashfs-factory.bin
LEDE supported since commit: https://git.lede-project.org/?p=source.git;a=commit;h=d738d22bf8303bd84e925b2b0c90793a1f3d89e5
LEDE supported since rel: 17.01.0
LEDE supported current rel: 17.01.4

Good: Openwrt/LEDE installs fine and generally runs well. Linux stable. LAN stable. LuCI works. SSH works. Able to access DSL modem web interface on WAN side through LUCI interface configuration, etc.

Bad: Wireless radio is unstable and unusable.
Symptoms observed:
  1. jamming across all WiFi channels
      - other nearby WiFi networks on different channels are disrupted (e.g. channels 4 and 12)
      - connection is lost to these other wireless networks from multiple devices and test pings show there is packet loss. (This happens after booting the Linksys E1700 LEDE device with wireless enabled)
  2. difficulty connecting to a new LEDE wireless network
      - seemingly placement of laptop 'not too close' and 'not too far' is required plus several attempts to successfully join the network
      - once connected, ping tests show some packet loss, intermittent variable round trip time (30ms-2400ms) and regular network drops (within a few minutes).

Test environment:
  - Existing, working Linksys WAG200G router in home with an existing SSID and DSL connection
  - Client: Ubuntu laptop (Asus Zenbook UX310U)
  - Client: Android phone (Pixel)
  - WiFi scanner and 'nmcli d wifi' are used to monitor wireless networks

Tested with settings:
  - Linksys E1700 (with OpenWRT/LEDE installed) wireless network on channel 4
  - Existing router (Linksys WAG200G) wireless network on channel 12
  - WLAN security mode: WPA2 Personal, PSK

Steps to reproduce:
  1. Have a Linksys E1700 device for testing and some other device with an existing wireless network on which a test laptop and phone are connected
  2. Upgrade firmware on new Linksys E1700 device to lede-17.01.4-ramips-mt7620-e1700-squashfs-factory.bin using factory GUI (from original firmware version 1.0.0: FW_E1700_v1.0.00.081_20131220.bin).
  3. Boot into LEDE. Perform initial setup. Configure wireless interface on channel 4 (or any channel other than the existing), security mode: WPA2 PSK, visible SSID
  4. Enable Wireless
  5. Note that soon after, all client devices in proximity become disconnected from the unrelated wireless network operating on channel 12 - this is the 'jamming effect' observed
  6. Try to connect the test laptop to the LEDE wireless network. Joining is difficult/unreliable (regardless of distance of the router from the laptop)
  7. When connectivity is established, ping the router from the test laptop. This will show some dropped packets and intermittent huge variation on round trip times  (30ms-2400ms). Network will drop regularly and hard to get back on.
  8. Repeat test with LEDE Linksys E1700 device on same channel, different channels, busy and free channels, etc. - makes no difference to outcome.
  9. Disable Wireless.  (Jamming effect seems to remain until power off but can't be 100% sure.)
  10. Power off the Linksys. The jamming effect disappears and the adversely affected devices reconnect to their original other network(s).

Steps taken to isolate fault:
  1. Restore firmware to Linksys factory default firmware (1.0.0).
  2. Create the same test wireless network and connect the test laptop to it.
  3. Ping test. This shows 100%, no packet loss, stable low round trip time.
  4. Connect the test laptop to the existing wireless network. Ping test. 100%. No side effects can be observed on other networks or client devices.
  5. Repeat LEDE router test from various distances.

This seems to rule out a hardware fault. Seems to be a radio fault.

There are two antennae on the E1700. It is unclear to me how these interact or how they can be configured.

I would be grateful if somebody can offer an explanation/suspicion of cause for this as I have not seen this with a WiFi device before. If LEDE can be patched to fix this then I am happy to help conduct further diagnostics if someone is willing to look at this.


Flash map for Linksys E1700:

root at LEDE:~# cat /proc/mtd
dev:    size   erasesize  name
mtd0: 00030000 00001000 "u-boot"
mtd1: 00010000 00001000 "config"
mtd2: 00010000 00001000 "factory"
mtd3: 007b0000 00001000 "firmware"
mtd4: 001286c8 00001000 "kernel"
mtd5: 00687938 00001000 "rootfs"
mtd6: 00458000 00001000 "rootfs_data"

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1373