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Advanced Wireless

The Advanced Wireless menu contains settings for advanced tuning of Wi-Fi interfaces. Changing these settings from the defaults is not recommended unless you are experienced with advanced Wi-Fi settings. All default settings in the dropdown menus on this page are noted with an asterisk (*). For basic Wi-Fi settings, see the wiki page for the Network menu.

Afterburner

Enabling Afterburner turns on support for Broadcom's frame-bursting and compression technology to improve 802.11g wireless throughput. This feature is also known as 125 High Speed Mode (or 125HSM) and goes by other names with other hardware vendors. Theoretically, this boosts signalling rates to 125 MB/s. Realistically, one can expect 30-40 Mb/s throughput in real world environments. Since this is a proprietary protocol extension, effectiveness will vary depending on the client device maker as well.

Options:

  • Disable *
  • Enable
  • Auto

AP Isolation

When enabled, wireless clients will not be able to communicate with each other through the FreshTomato router, but will be able to communicate with the router itself or to the Internet. This may be useful on guest networks, to prevent hacking and other security problems. This doesn't guarantee security, however. For example, this setting does NOT prevent ad hoc Wi-Fi connections between client devices, or direct Bluetooth or NFC connections.

Options:

  • Disable *
  • Enable

Authentication Type

This option controls whether clients must use shared keys to authenticate. Shared Key is disabled in some wireless security modes, for compatibility.

Options:

  • Auto *
  • Shared Key

Protected Management Frames

Three configuration options exist for Protected Management Frames (PMF). [Note: Protected Management Frame (PMF) feature is also known as Management Frame Protection (MFP)]

Options:

  • Disable *
  • Capable (Note: wireless clients, capable of PMF or not, can connect to the network –> Please check your wireless clients for connectivity problems!)
  • Required (Note: Only PMF-capable clients can connect to the network)

By default, this wireless security enhancement option is disabled because not all wireless clients support it. Support for this option is available starting with release 2021.6 (only for ARM hardware).

Basic Rate

The Basic Rate Set is a list of rates at which the router reports it can sync. with wireless client devices. A router regularly broadcasts the Basic Rate Set in its beacon packets. In this way, wireless clients in your network know which rates will be used. The Router will also advertise that it will automatically select the best rate for transmission.

Options:

  • Default *
  • 1-2 Mbps
  • All

Default: Tomato advertises that it can sync. at all standard wireless rates. This includes: 6, 9, 12, 18, 24, 36, 48, and 54 Mbps in addition to the 802.11b rates of 1, 2, 5.5 and 11Mbps.

1-2 Mbps: This setting is sometimes required for compatibility with 802.11b clients, if they don't connect via the Default setting.

All: This setting makes Tomato advertise all wireless rates supported in hardware.

Beacon Interval

This specifies the period of time between one beacon broadcast and the next. A beacon is a packet broadcast by the router to synchronize the wireless network and serve other administrative functions. (Default: 100 ms).

CTS Protection Mode

Options:

  • Disable *
  • Auto

This function could more appropriately be called RTS/CTS Protection Mode. Wireless client devices transmitting to a router cannot detect when other devices on the same network are also transmitting. When more than one client transmits at a time, data collisions occur. The router is then forced to discard data from both clients. This increases error rates and reduces speed. When Clear-to-Send Protection is on, a computer must send a RTS (Request to Send) frame to the router. This is basically a request to be allowed to transmit at that moment in time. In return, the router must send back a Clear-To-Send frame indicating the client can send data. In this way, CTS Protection Mode determines the order in which computers contact the access point/router. Typically, CTS frames are not sent/needed until the client has a data frame to send that meets a certain size threshold. That threshold frame size can be set in the RTS Threshold field. See below for details about that setting. CTS is typically used for 802.11b/g/n/ac protocols. RTS-CTS is typically used with 802.11a/b/g protocols.

Auto: determines which computer can reach the FreshTomato router at a specific time through CTS and its send (RTS) packet. Disabled is the recommended setting, since well-designed networks rarely need it. However, if you are experiencing lots of physical layer collisions, then you might try enabling this and tuning the RTS Threshold setting.

Regulatory Mode

Options:

  • Off *
  • 802.11d
  • 802.11h

This option lets you choose which wireless standards are followed. Countries (usually adjoining) that share a common set of regulations are referred to in the 802.11 specification as regulatory domains. Four major regulatory bodies have authority over almost all of the world's technology regulations:

  1. Federal Communications Commission or “FCC” (USA)
  2. European Telecommunications Standards Institute or “ETSI”
  3. Telecom Engineering Center or “TELEC” (Japan)
  4. (South) Korea Communications Commission (KCC)

Each domain has strict regulations for parameters such as antenna gain, transmit power, channel selection. Many countries choose to adhere to the standards completely. A few countries modify an existing standard to their own unique needs. This can create complications.

802.11d: This supplemental standard adds the requirements and definitions necessary to allow 802.11 wireless equipment to operate in markets not served by the current standard. This includes anywhere other than the Americas (FCC), Europe (ETSI), Japan (TELEC), China, Israel, Singapore, and Taiwan.[1]

802.11h: 802.11h is the IEEE standard for Spectrum and Transmit Power Management Extensions. It solves problems like interference with satellites and radar using the same 5 GHz frequency band. The standard provides Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC) to the IEEE 802.11a MAC. (Media Access Control layer).


advanced-wireless-composite.jpg

Country / Region

(Default: Singapore / 12)

Country code AND rev(ision) define the possible channel list, power and other regulations for each country. The current wireless driver (year 2020 and newer) supports approximately 290 countries and 2000 combinations of country code and revision.

Example Country / Region and Country Rev choices:

  • CY / 4 - Country: CY (Cyprus) AND Country Rev: 4
  • CZ / 4 - Country: CZ (Czech Republic) AND Country Rev: 4
  • EU / 13 - Country: EU (Europe) AND Country Rev: 13
  • EU / 33 - Country: EU (Europe) AND Country Rev: 33
  • EU / 53 - Country: EU (Europe) AND Country Rev: 53
  • EU / 78 - Country: EU (Europe) AND Country Rev: 78
  • DE / 7 - Country: DE (Germany) AND Country Rev: 7
  • PL / 4 - Country: PL (Poland) AND Country Rev: 4
  • FR / 5 - Country: FR (France) AND Country Rev: 5
  • GB / 6 - Country: GB (Great Britain) AND Country Rev: 6
  • FI / 4 - Country: FI (Finland) AND Country Rev: 4
  • HU / 4 - Country: HU (Hungary) AND Country Rev: 4
  • ES / 4 - Country: ES (Spain) AND Country Rev: 4
  • IT / 4 - Country: IT (Italy) AND Country Rev: 4
  • US / 0 - Country: US (USA) AND Country Rev: 0
  • Q2 / 96 - Country: Q2 (USA) AND Country Rev: 96 (Asus default setup for USA and SDK7 router RT-AC3200)
  • CA / 223 - Country: CA (Canada) AND Country Rev: 223
  • BR / 17 - Country: BR (Brazil) AND Country Rev: 17
  • BR / 20 - Country: BR (Brazil) AND Country Rev: 20
  • RU / 50 - Country: RU (Russia) AND Country Rev: 50
  • CN / 38 - Country: CN (China) AND Country Rev: 38
  • CN / 224 - Country: CN (China) AND Country Rev: 224
  • AU / 43 - Country: AU (Australia) AND Country Rev: 43
  • AU / 44 - Country: AU (Australia) AND Country Rev: 44
  • SG / 12 - Country: SG (Singapore) AND Country Rev: 12 (default *)

Some combinations of Country and revision codes are invalid, and will not work together. For example, if you set country to USA, and change only country to “US” and leave revision at “12” that would be invalid. You need to change country / region to “US” and country revision to “0” to have a working combination.

Most users will be able to choose the correct settings from those in the Wireless menu. However, there are many more settings.

Advanced users can see the complete list of settings and their code commit entries here:
For SDK6 routers:
https://bitbucket.org/pedro311/freshtomato-arm/commits/ffb286c7afa64b02bc2136d6bd67ba6f7f6b42b2/raw

For SDK7 routers:
https://bitbucket.org/pedro311/freshtomato-arm/commits/92da4ad49c2df3bc6d17f58c1b564891ce87a048/raw

For example, for SDK6 (ARM models only) builds and country USA, open file “wlc_clm_data.c”
(sysdeps/RT-AC68U/clm/src/wlc_clm_data.c) and go to line ~98738. There, you will see the following:

/** Region definitions */
static const clm_country_rev_definition10_fl_t country_definitions[] = {
    /*      CC    rev      2.4        5            2.4 HT              5 HT  flags */
...
...
    REGION("US", 0 /*  0 */,   A6_58,   29e_2,           An7_62,           29en_9, SCR_2    | CLM_DATA_FLAG_REG_TXBF), /* US/0 */  <-- Line:  98738 (Example provided at advanced-wireless page)
    REGION("US", 1 /*  1 */,   A6_58,   29e_2,           An7_62,           29en_9, SCR_2    | CLM_DATA_FLAG_REG_TXBF), /* US/1 */
    REGION("US", 2 /* 11 */,      A1,     19b,              An4,             19bn, SCR_NONE), /* US/11 */
    REGION("US", 3 /* 13 */,      A5,      15,              An6,              15n, SCR_NONE), /* US/13 */
    REGION("US", 4 /* 14 */,      A6,      15,              An7,              15n, SCR_NONE), /* US/14 */
    REGION("US", 5 /* 18 */,      A9,      15,            An6_2,              15n, SCR_NONE), /* US/18 */
    REGION("US", 6 /* 19 */,      A6,      19,           An8_T2,             19cn, SCR_NONE), /* US/19 */
    REGION("US", 7 /* 20 */,      A3,    19_1,           An1_T3,            19n_1, SCR_NONE), /* US/20 */
...
...



The comment field on the right contains valid country and revision combinations. You can see that country “US” and country rev “12” is NOT a valid setting for the wireless driver. Do not use “#a” or “#r”. They are special values for testing and not for regular use.

NOTE: For MIPS SDK5 (RT and RT-N) builds, there is currently only a country selection setting. Starting with MIPS SDK6 (RT-AC) builds and all ARM-Branches/Versions you will need to choose a country and a country rev. This applies to release 2020-6 and later.

Country Rev

See the Country/Region section above. Revision settings only exist in FreshTomato 2020-6 and later.

Bluetooth Coexistence

Options:

  • Disable *
  • Enable
  • Preemption

Bluetooth and 2.4 GHz Wi-Fi radio waves can interfere with each other, since both operate on the same (2.4 GHz) frequency band. Choosing Enable can help to reduce that interference, by asking the Bluetooth devices to take turns using the same channels as your Wi-Fi.

The Preemptive function will make FreshTomato inform the Bluetooth device about which Bluetooth channel it's operating on. The Bluetooth device can then mark that channel as “in use” and use alternate channels for its own communications.

The Bluetooth devices must support the Bluetooth Coexistence function, or they will be unable to share nicely and this option will have no effect.

Distance / ACK Timing

(Default: 0)

When a router sends a packet to a client, it waits for an ACKnowledgement frame from the client to ensure the packet was received. The time period the router waits for that acknowledgement is called the “ACK timeout” (or “Timing”). Traditionally, ACK Timing is set to the maximum distance of the furthest client device in meters x 2. The doubling is to account for the round-trip distance/time, including the time it takes for the client to receive the packet, and the time for the response to travel back to the router. For example, if you roam with your laptop up to 50 meters from your AP, the setting would be 100. Generally, the default is recommended, except where administrators have a strong knowledge of timing or are building long-distance wireless links.

Typically, 802.11b/g has a range of less than 100 meters. Therefore, one might assume this should never be set higher than 200. However, in scenarios with high power antennas or other long-range gear, the timing settings would need to increase. Longer distance links have been established far beyond the theoretical limits of 802.11 b/g.

However, higher ACK Timing comes at the cost of lower throughput. If set too high, packets could be lost as the router waits for the ACK window to timeout for ACK frames that were never going to arrive. It will also resend the “unacknowledged” packet to the client, thinking it might not have received it yet. If ACK Timing is too low, the router may drop returning ACK frames too early, and again resend the original “unacknowledged” packet. This too might lower throughput.

DTIM Interval

(Default: 1)

A Delivery Traffic Indication Message (DTIM) message is a field included in some beacon frames. It informs clients that the access point/router has buffered or multicast/broadcast data to receive. When in power-save mode, a client device may sleep for one or more beacon intervals, then wake up for beacon frames that include DTIMs. A DTIM message notifies sleeping clients that they will need to wake up to receive the waiting frames.

The DTIM Interval specifies how often a beacon frame includes a DTIM message, expressed as the number of beacon frames that will be sent before a DTIM is included in a beacon frame. DTIM Interval values range 1 to 255. The DTIM Interval value is included in each beacon frame. Following a beacon frame that includes a DTIM, the router will release any existing buffered broadcast and/or multicast data. This means that the DTIM message is included in every second beacon frame.

  • Shorter DTIM Intervals force network clients to wake up more often to be ready to receive broadcast/multicast traffic. This puts higher loads on the clients, which may increase power consumption, which may cause battery-powered devices to drain faster.
  • Longer DTIM Intervals let clients sleep longer and save power. However, with the router waiting to send the data, it may have to buffer more of the broadcast/multicast data. The extra buffering could cause overruns if the router can't store all the data until it can be sent. Thus, longer intervals can slow throughput.

In other words, wireless clients may have conflicting requirements for power consumption and communication throughput when in power-save mode.

Fragmentation Threshold

(Default: 2346)

IP fragmentation is the process of the IP layer breaking down datagrams into smaller pieces (fragments). The destination host, or sometimes intermediate routers reassemble the fragmented pieces to make the message whole again. This is usually done to reduce the size of the datagrams so that the pieces can pass through a link with a smaller MTU than the original datagram size.

This option specifies the maximum size of datagram that can occur before it is fragmented into multiple datagrams. Similar to RTS Threshold, tuning the Fragmentation Threshold setting may reduce frequent collisions on the network. Too low values may cause poor network performance. The default setting is reccomended.

Frame Burst

Options

  • Disabled *
  • Enabled

Frame-bursting is a link layer protocol used to increase the throughput of connections on links between 802.11a/b/g/n hosts under certain network conditions. It does this by reducing the overhead used in the wireless session between hosts. It grew from standards first introduced in the 802.11e QoS specification for link layer connections.

Network protocols for shared media are designed so that any host that has sent a MAC layer frame is then supposed to yield the medium and wait for a fixed period of time. This helps create a fair use of the medium by multiple users.

Frame bursting allows wireless clients to upload data at faster speeds by using the wait intervals between frames to “burst” a series of up to three frames before waiting the required period. As usual, there are compromises. Frame Burst can cause unfair allocation of airtime on networks where where only some clients support Frame Burst. The wait periods between frames were not originally designed to include data traffic. The recommended setting is Disabled, unless there are very few hosts on your network. Broadcom's implementation of this feature is called “Express Technology”.

Maximum Clients

(Default: 128)

This specifies the maximum number of clients that can be connected to the wireless network. It is not recommened to increase this number, as the likely result will be an overloaded network with slow throughput. There is little harm in testing a lower number. This can be useful to reduce network traffic, or for security purposes.

Multicast Rate

Options:

  • Auto *
  • 1 Mbps
  • … up to
  • 54 Mbps

This setting controls the rate at which hosts can send multicast packets to a multicast group. Traffic exceeding this rate is discarded. Optimizing this rate can lower collisions, especially when multiple devices or services are being run at the same time. Optimization may be essential for applications which stream video and corporate communications.

For small, basic networks, the default should work fine. However, on larger networks, it's recommended that you adjust this setting. Typically, switching to the lowest setting is the quickest, easiest way to optimize your system. However, networks with more client devices will likely require higher settings to be effective. Setting this too high can impact performance, so you may need to test to ensure that your setting isn’t using up all of the bandwidth on just one device.

Preamble

Options:

  • Long *
  • Short

In wireless networking, the preamble (or “header”) is a section of data at the head of data link layer frames which contains information wireless devices need to send and receive data. Part of the preamble involves the length of the CRC (Cyclic Redundancy Check) block for communication between the router/AP and roaming wireless adapters. CRC is commonly used to detect data transmission errors.

Generally, all wireless devices on the network should use the same preamble type. If they don't, they will have trouble communicating. On some legacy wireless equipment, Preamble type may bet set with a physical switch. Current hardware has this setting available in its web interface or command-line interface.

The deafult setting is Long, to maintain compatibility with older equipment. Long preamble is also recommended for longer-distance connections or links with weak signals, since both require more extensive error checking. The Short preamble can be used on modern equipment which transmits strong signals in a fairly low-interference environment.

802.11n Preamble

Options:

  • Auto
  • Mixed Mode *
  • Greenfield
  • GF-BRCM

For an explanation of basic concepts of the wireless preamble, see the Preamble section above.

Auto: TBD.

Mixed Mode: Mixed Mode transmissions can be decoded by 802.11a/g clients, providing backwards compatibility. In Mixed mode, 802.11n devices transmit a legacy format preamble, followed by an HT format preamble and a legacy radio signal. A Mixed mode device must also send legacy format CTS-to-Self or RTS/CTS (Request to Send/Clear to Send) frames before transmitting. These mechanisms let other 802.11a/b/g devices sense a busy network medium and wait for another turn to transmit. This alows for backwards compatiblity with earlier protocols, but reduces throughput, compared with Greenfield, or GF-BRCM modes.

Greenfield: This 802.11n mode is also known as “High Throughput” or “HT” mode. In this mode, the protocol improves efficieny by using a high throughput modulation method and a shorter preamble. Neither of these is supported on 802.11a/b/g devices. This preamble mode compromises backwards compatiblity and can reduce throughput on some 802.11n devices not fully compatible with the standard.

GF-BRCM: TBD.

Overlapping BSS Coexistence

Options:

  • Off * Channel width settings will function as configured.
  • On: If Tomato detects interference, it will switch from use of 40 MHz channel width to 20MHz channel width.

RTS Threshold

(Default: 2347)

When CTS (Clear-to-Send) Protection is on, a host must send an RTS (Request-to-Send) frame to the router to obtain permission to transmit data frames at that time. In return, the router must send back a Clear-To-Send frame, indicating the client can send data. In this way, CTS Protection Mode determines the order in which computers contact the access point/router. Typically, CTS frames are not sent/needed until the client has a data frame to send that meets a certain size threshold. That threshold frame size is set here, in the RTS Threshold field.

Transmit Power

(Default: 0)

This allows you to override regulatory and other limitations and increase or lower the Transmit Power, in mW (milliwatts). The default setting is “0”, which uses the regulated power level for your chosen country setting. It is recommended that before you increase Transmit Power to improve signal range, you try signal-reception solutions first, such as relocating your router/AP to a more central location, elevating it, or (if supported) using better, external higher gain antennas.

Lowering Transmit Power can be useful for increasing security. For example, if power is too low to reach past the boundaries of your property, it will be harder for others to snoop on your connection. Doing so could also reduce interference received by other, nearby radio equipment.

Transmission Rate

Options:

  • Auto *
  • 1 Mbps
  • … up to
  • 54 Mbps

The default/recommended setting is Auto.

AC-PHY Interference Mitigation

This option is only available for AC capable wireless ICs / interfaces

  • None * (default)
  • desense based on glitch count (opt. 1)
  • limit pktgain based on hwaci (opt. 2)
  • limit pktgain based on w2/nb (opt. 3)
  • opt. 1 AND opt. 2
  • opt. 1 AND opt. 3
  • opt. 2 AND opt. 3
  • opt. 1 AND opt. 2 AND opt. 3 (All option enabled)

Interference Mitigation

This option is only available for NON-AC capable wireless ICs / interfaces

  • None * (default)
  • Non-WLAN
  • WLAN Manual
  • WLAN Auto
  • WLAN Auto with Noise Reduction

WMM

Wireless Multimedia options:

  • Auto
  • Disable
  • Enable * (default and also recommended setup)

Note: Disabling WMM will/should result in clients falling back to 802.11a/g rates (54 Mbit/s).

No ACK

No Acknowledgement options:

  • Disable * (default)
  • Enable

APSD Mode

Automatic Power Save Delivery options:

  • Disable
  • Enable * (default)

Wireless Multicast Forwarding

Options:

  • Disable * (default)
  • Enable

Turbo QAM

This setting will enable Turbo QAM, Broadcom's name for 256-QAM. Do not confuse this with Broadcom's other Turbo QAM, a modulation scheme used for cablemodem technology. (Requires Wireless Network Mode set to Auto)

Turbo QAM, or 256-QAM is a modulation method in which the two carrier signals are shifted in phase by 90 degrees. These two signals are then modulated and combined. The 90° difference in phase between the two signals means they are “in quadrature”.

In theory, this modulation method makes it possible to transmit more bits per symbol, and thus increase data rates. In reality, most claims of big increases in transfer rates are likely exaggerated. QAM links are more susceptible to noise. As a result, Turbo QAM is generally only useful in very low-noise/interference wireless environments. Many people report it being effective on line-of-sight links of up to about 25 feet. Vendors claim the range with Turbo QAM may improve when beamforming is used. You may need to experiment to see what works best on your network.

Explicit beamforming

Checking this enables Explicit beamforming technology. Traditionally, most Wi-Fi routers and access points have included omnidirectional antennas. These radiate radio energy equally in all directions. This is not always the most effective/efficient way to exchange radio signals with a client device. Much of the signal goes off in directions other than the client or other device. Explicit beamforming improves on this.

Beamforming radiates signals towards the receiver, instead of in an omnidirectional pattern. If the hardware has adequate information to send the radio energy in one particular direction, it will do so. The result can be an increase the signal-to-noise ratio and data rates between the two devices.

Beamforming was introduced starting with 802.11n. but vendors used different standards. This meant beamforming made little differnece in performance. With 802.11ac, the beamforming method was standardized (Explicit). Compatibility across vendors is good. Explicit beamforming requires both client and router/Access point to support the feature. If both devices support it, they'll use a handshake at the beginning of their session to help establish their respective locations and the channel on which they'll communicate.

Beamforming works best at medium range. At short range, the signal power is high enough that the signal-to-noise ratio will support the maximum data rate. At long ranges, beamforming does not offer gains over an omnidirectional antenna.

Universal/Implicit beamforming

Beamforming is a performance feature included in Wi-Fi protocols starting with 802.11n. Beamforming radiates signals more directly towards the receiver, instead of in an omnidirectional pattern, like older equipment. This can result in a higher signal-to-noise ratio and data rates between the two devices exchanging data.

Traditionally, most Wi-Fi routers and access points included omnidirectional antennas. These radiate radio energy equally in all directions. This is not the most effective/efficient way to exchange radio signals to another device. Much of the signal goes off in directions away from the or other wireless device.

With 802.11n, several beamforming methods were allowed, but no standard method existed. A lack of standardization meant beamforming usually provided little performance improvement.

Implicit beamforming is used with legacy devices that don't support beamforming. With Implicit beamforming, the router estimates the channel and determines the radiation direction to improve signal/transmission rate to the client device. However, it won't be able to radiate signal as precisely to the endpoint device as it could if the endpoint supported Explicit beamforming. (See above section). Implicit beamforming is also known as Universal beamforming, since it can theoretically work with almost all client equipment, even that which doesn't support beamforming.

Both access points and clients (which support it) can use beamforming. However, the higher processing power and larger distance between antennas in routers/access points means that most beamforming performance gains should be expected in transmissions from router/AP to client.

Air Time Fairness

Enable/Provide Airtime Fairness between multiple links.

wireless.txt · Last modified: 2021/09/30 15:21 by hogwild