DD-WRT:Atheros/ath wireless settings

Introduction
This page shows the contents and descriptions of standard and advanced wireless settings for Atheros based routers based on the latest current driver in use which is ath9k. '''Not every driver shows every possible setting shown here! Some routers will have less''' If you are a Broadcom or Ralink user, please refer to this page for Broadcom/Ralink wireless settings.

Wireless Physical Interface
Available Interfaces: ath0, ath1 (Varies by router)

If you have a dual band router ath1 will be displayed below ath0 with the same available settings. Ath0 is the 2.4GHz radio and ath1 is the 5GHz radio. If you create a VAP for 2.4GHz or 5GHz radio the VAPs will be labeled ath0.1 and ath1.1 respectively. Refer to this thread for some info about VAPs with Atheros.

Wireless Mode
Available Settings: AP, Client, Client Bridge, Adhoc, WDS Station, WDS AP

Recommended Setting: AP for most users, Client or WDS if you are more advanced and know you need it

Determines how the specific wireless interface of the router is to behave. If you want to run a normal access point which most do, AP would be your choice. Client and Client Bridge are the Atheros equivalent Broadcom's Repeater and Repeater Bridge settings.

Wireless Network Mode
Available Settings(2.4GHz): Disabled, Mixed, B-Only, G-Only, BG-Mixed, NG-Mixed, N-Only

Available Settings(5GHz): Disabled, A-Only, NA-Mixed, Mixed

Recommended Setting: Mixed or NG-Mixed/NA-Mixed

Controls which 802.11 signals are being broadcast by the radio. Depending on the selected network mode your wireless channel list and maximum TX power can vary. Mixed is the recommended setting for most people as you are able to use either HT20 or HT40 "properly" with this setting. If you have any issues & hardly use or do not use 802.11b clients, switch to NG-Mixed. N-Only is broken on many units for some time & still is, try to avoid as there is NO performance change from Mixed -> NG-Mixed -> N-Only if all you use is 802.11n clients for either of them. For 5GHz radios, Mixed & NA-Mixed are the same theoretically as all there is for 5GHz spectrum IS 802.11a & 802.11n clients.

Channel Width
Available Settings: Dynamic (20/40 MHz), Turbo (40 MHz), Full (20 MHz), Half (10 MHz), Quarter (5 MHz)

Recommended Setting: Turbo (40 MHz), Full (20 MHz) if using long range (1km+) links or have strong interference in your area such as baby monitors, several other wifi APs etc.

This determines the width of the wireless channel where higher allows more bandwidth but less overlapping channels and lower allows more non-overlapping channels but less bandwidth. It is said that 40 MHz, which enables channel bonding by using two 20 MHz wide channels together, is not "neighbor friendly". This is correct as the wider channel creates more overlap onto other channels, which /could/ create more interference for neighbors, but usually is not an issue unless you are in a VERY packed wireless area. 40 MHz allows your 2.4GHz 802.11n draft devices to connect at their max of 300 Mbps when signal is sufficient as well as a large throughput increase and enables Atheros Super-G*. If Full (20 MHz) is used for 802.11n clients the max connection speed will only be 130 Mbps and 802.11g clients supporting Super-G max connection speed will only be 54 Mbps.

*Note: You MUST have this setting on Turbo (40 MHz) to allow 802.11n devices (2.4GHz & 5GHz) to connect at their max!

*Note 2: 802.11a/g + Turbo (40 MHz) = Super-G!*

*Super-G
This is an Atheros technology to increase the throughput of 802.11g devices and NOT compatible with 40MHz channel width in 802.11n. In order to utilize the Super-G feature you must have an Atheros router capable of broadcasting 40 MHz wide channels, nearly all Atheros routers support this feature, and a Super-G ready client. If you have an Atheros router and Super-G ready client, ensure your wireless network mode is on Mixed or G-Only with Turbo (40 MHz) as the channel width. The client should now connect at the theoretical max link rate of 108 Mbps, doubled that of standard 802.11g 54 Mbps. This feature reaches these speeds by channel bonding, a method that bonds two 20 MHz wide channels together, a similar way 802.11n does. Maximum true throughput with a Super-G client should be around 90 ~ 95 Mbps depending on distance, SNR, noise, & other wireless settings and optimizations.

Wireless Channel
Available Settings: Channels 1 - 14 depending on your regulatory domain & channel width

Recommended Setting: Any if on build r18000 or higher* Use the channel giving most throughput/range/SNR

Controls when channel or frequency your WLAN uses. If you have packet loss or abnormally slow throughput switch to another channel for less interference. All routers default to either channels 1, 6, or 11, it is not recommended to use these channels as most users are inexperienced, and leave them at their defaults. Most of these channels are noisy but for any reason if there isn't many APs around you using these channels, use them.


 * The reduced link rate issue with channels 1, 3, 5 appears to be corrected with the ath9k builds. As well as channel 11's weak TX power, could be Canada/USA's regulatory laws have changed also regarding channel 11 TX power.

Control Channel
Available Settings: Upper, lower

Recommended Setting: Any

This setting is only valid when Turbo (40 MHz) is used for channel width. It controls if the secondary, or control channel, which is the second channel used to attain the 40 MHz width, is above or below the primary selected channel. Recent builds have fixed the selectable channels, use upper or lower depending which channel you want.

Wireless Network Name (SSID)
This is where you can choose the name of your wireless network when its being broadcast to roaming clients. You can name this anything you want.

Wireless SSID Broadcast
Available Settings: Enable, disable

Recommended Setting: Enable

Dependent on the setting above, this controls if your SSID is being broadcast or not. When disable is selected many clients still pick up the beacon and display it as "Hidden" along with the AP's MAC address. Disabling is not recommended as it hardly does anything for security, a determined intruder can still access your network with different methods.

Advanced Settings

 * Build 14815 and newer has a tab to show or hide advanced wireless settings.

Regulatory Domain
This determines the channels available in the list for both bands (if you have a dual band router) and the maximum EIRP "legally" allowed by the telecom authorities in chosen country. EIRP is TX power plus antenna gain, an example.

20dBm TX power and 2dBi antenna gain has an EIRP of 22dBm. 22dBm TX power and 0dBi antenna gain also has an EIRP of 22dBm.

Maximum EIRP varies by nation and your max TX power will be capped by the regulatory domain if you have a powerful radio. For example, Canada's max EIRP is 36dBm, with Canada selected and antenna gain at 0dBi. The radios will never go above 36dBm.

TX Power
Recommended Setting: Highest dBm your radios/regulatory domain support

Transmit power (TX) is the amount of "current" or "juice" going to the antennas, it is NOT the output power FROM the antennas, as that is EIRP. Usually more TX power is better as it allows clients further away to "hear" your AP. Assuming the clients also have near equal TX power so the AP can "hear" them back. If TX power is increased too much excess noise can develop and reduce throughput or even range, but with Atheros this does not seem to be much of a problem as most Atheros radios work very well at their max TX power. Maximum TX power is controlled by the radios (power control*), regulatory domain, wireless channel used, and wireless channel width. The default value for most routers currently is 20dBm.

*Power control

A feature which controls the max TX power by the SNR & link speed. The higher the SNR, the lower the TX power will be(this action does not display on the wireless status GUI). See vendor/device specs for more info.

Antenna Gain
Recommended Setting: dBi value of the antenna(s) used on the router

Antenna gain is amount of "gain" or "boost" of signal that the antenna provides. Its a bit complicated but remember this, antennas are not amplifiers. They do not magnify the signal, but instead "focus" the signal in certain directions, yes even omni-directional antennas do it. The higher the gain the better as it increases EIRP which somewhat helps extend range and significantly helps sensitivity. With high sensitivity, the AP is able to hear "faint" clients, clients that may have a low TX power or are just simply very far away. Set this to the correct value of the antennas used on your router, it does do a difference, small, but its there.

Protection Mode
Available Settings: None, CTS, RTS/CTS

Recommended Setting: RTS/CTS

This setting controls whether the clear to send/request to send mechanism is enabled or disabled. When enabled, a RTS/CTS handshake must be completed before data can be transmitted. Sometimes helpful in noisy environments it ensures all clients "take turns" communicating with the AP, if disabled sometimes packet collisions can occur causing a drop in throughput due to retransmission overhead. This is a setting to experiment with if you have high TX/RX packet errors especially in a short time. Most users should leave this set to RTS/CTS for max throughput because the protection mechanism is only enabled automatically when needed, which when its needed, and if its off, your wireless performance can plummet with errors and disconnects. If its not needed it is turned off automatically.

RTS Threshold
Available Settings: Enable, Disable

Recommended Setting: Enable

Only valid if RTS/CTS is enabled, this setting sets the maximum packet size before it is fragmented into smaller packets, if you still have high TX/RX errors with RTS/CTS enabled and RTS Threshold at it's default, try lowering it by 10. Lowering it too much can further create overhead and reduce throughput. Leaving this on the default setting 2346 essentially disables the RTS feature and only leaves CTS enabled as most packets don't exceed 2346 bytes.

Transmission Minimum & Maximum Rate
Available Settings: Auto, 1 Mbps ~ 300 Mbps depending on your network mode selection, channel width, regulatory domain

Recommended Setting: Auto

This setting is completely removed in the more recent builds due to it's lack of working function, it is unknown if it will return. This setting controls the minimum and maximum theoretical rates for connected clients, on certain wireless network modes such as NG-Mixed this setting does not work properly, if at all. It is recommended to leave this setting on Auto if you have the setting, or it returns in future builds.

Short Preamble
Available Settings: Enable, Disable

Recommended Setting: Enable

If you have 802.11b clients in your network try enabling this, if they have problems connecting or with performance then leave it disabled. Preamble is at the head or front of the PLCP which devices need in order to start transferring data. The long preamble ensure compatibility with legacy 802.11b devices but can slightly reduce throughput at high data rates. The support for short preamble which is reducing the header's size by 50%, down to 9 bytes, is optional for 802.11b. 802.11g and newer all support short preamble, so if you do not have and 802.11b devices in your network you can enable this for a small throughput increase.

http://wireless.subsignal.org/index.php?title=WLAN-Optimierung

TX & RX Antenna Chains
Available Settings: 1, 1+2, 1+3, 1+2+3

Recommended Setting: Varies by router

This setting is critical for proper, smooth, fast Wi-Fi performance. 2x2 routers will either have TX/RX chains at 1+2/1+2, 1+3/1+3, 1+2/1+3, or 1+3/1+2. This can take some time to find the proper setting but its worth it, you can more easily find the correct setting by using a 802.11n draft 2.0 client thats capable of 300 Mbps link. Note the TX/RX link rates on the wireless status page, when set incorrectly one or both of the rates will drop to a much lower speed such as 200, 170, 81 etc. This is best done with the client less than 10 feet from the AP with clear line of sight. Some routers with chains set incorrectly such as D-Link DIR-615 C1, will deny connections to clients, heavily reduce throughput, and other errors. Searching the FCC ID of your router will aid in setting the correct chain settings. Some popular routers such as the Netgear WNDR3700 and D-Link DIR-825 B1/B2 require both chains set at 1+2 for proper Wi-Fi performance. Default is not always right!*

*With recent builds (at least r20000+) most units have the proper defaults preset & invalid options removed, such as 1+2+3 for TX/RX on WNDR3700 as the router only has 2 chains each therefor only has 1 & 1+2 available to be selected.

AP Isolation
Available Settings: Enable, Disable

Recommended Setting: Disable for most users, enable for public hotspot

AP Isolation allows clients connected to the same AP to communicate with each other or not, very much like Ad-Hoc mode. If you run a Wi-Fi hotspot its recommended you enable this for privacy/security reasons. If you want files to be shared from client to client in your home network, AP isolation must be disabled. This setting does not influence Wi-Fi throughput. If this setting is enabled it will break online play on some gaming devices such as Nintendo's DS system.

Radar Detection
Available Settings: Enable, Disable

Recommended Setting: Disabled for most users. Enabled if country law requires it.

Radar Detection (DFS: Dynamic Frequency Selection). If enabled, radar detection will change the frequency only when it identifies a military radar nearby in it's frequency. Most users shouldn't have any interference issues even those living near military locations.

ScanList
A list of channels to be used when searching, seperated by comma. Specially usefull when using SuperChannel feature.

Sensitivity Range (ACK Timing)
Available Settings: 0 - 999999

Recommended Setting: 0 - 2000 for both 2.4 & 5 GHz, greater than 2000 only when needed for long distance links

ACK timing is also a throughput controller, too high and your devices will literally be "waiting" too long and time will be passing with them at idle. Too low and active transmissions could be cut off causing retransmissions which create overhead, that lowers throughput. The AP sends a packet and all clients must wait for XXX time, where XXX is the ACK timing, the client then receives that packet and responds to the AP with an ACK(nowledgement), AP sees the AP then finally everyone is free to transmit.

Most users want this between 0 - 2000 (2.4 or 5 GHz), the distance used is meters and needs to be doubled the distance of the furthest client from the AP (plus some headroom). Doubled because the signal travels to the client and back, double the distance. In earlier builds with the older madwifi driver reducing ACK from default 2000 to 1500 caused a throughput increase of 0.6 Mbps - 1 Mbps, though with modern builds (r18000+) using the new ath9k driver, along with the internal changes to ACK timing, reducing to 1500 does about nothing for throughput, one would have to drop below 900m at least, as well with the current ath9k builds an ACK timing of 0 DOES disable it completely like on Broadcom, this is generally the new best setting. But if you do not disable ACK timing remember an ACK timing too low can cause issues described above.

Long distance links, such as 2 KM+ will need to increase this setting accordingly. 4000m for 2km, 6000m for 3km, and so on.

Max Associated Clients
Available Settings: 1 - 256

Recommended Setting: Any

Determines the maximum number of clients that can be connected to the AP at any given time. Hotspot users will find this very handy.

MTik Compatibility
Available Settings: Enable, Disable

Recommended Setting: Disable

It activates a beta WDS compatibility with Mikrotik RouterOS. It's almost useless. Only use it when you're testing stuffs from dd-wrt.

Network Configuration
Available Settings: Unbridged, Bridged

Recommended Setting: Bridged for most users

This setting controls if the wireless interface is "bridged" with the LAN ports. Bridged meaning a client on the wireless interface and a client on the Ethernet LAN interface are on the same network on the same subnet. Unbridged allows you to "separate" the WLAN (wireless LAN) by giving it its own subnet and even its own DHCP server. If you want a unbridged interface, you are better off creating a VAP instead of unbridging the main interface.