Advanced Wireless Settings Reference Guide

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mac913
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PostPosted: Tue May 05, 2009 18:16    Post subject: Reply with quote
vtphilk wrote:
My vote is for add to the wiki.

And I disagree too technical. If you are not interested in the 'too technical' stuff you probably should not be mucking with advanced wireless settings Smile


I agree, I like the detail gives me a better understanding how all the setting interact with each other.

I've saved this post as a favorite. Thanks everyone! Very Happy

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darthn
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PostPosted: Tue May 05, 2009 18:24    Post subject: Reply with quote
Sticky this and add it to the wiki!
redhawk0
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PostPosted: Tue May 05, 2009 19:02    Post subject: Reply with quote
I love this thread....and I originally thought it would be a good sticky...however, I thought about it more.

It is probably best to make this a wiki entry so corrections can be made to it. Settings seem to be added and removed by the devs on a regular basis...the document must also be volatile and the wiki would be a good place so the edits can be made if the OP should "disappear"

This thread is a great place to start brainstorming and working the "kinks" out and document the details....then consolidate the entire thing into a single wiki entry.

I don't know who does the "Help" pages of the web gui...but maybe that person could incorporate the "dumbed down" version for the general public. The wiki could then contain the in depth information found in this thread.

redhawk

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stephensuley
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PostPosted: Wed May 06, 2009 1:15    Post subject: Reply with quote
Beacon Interval is updated...comments?



Beacon Interval
Range 1 and 65,535 milliseconds. The default value is 100.

The help file says...
The Beacon Interval value indicates the frequency interval of the beacon. A beacon is a packet broadcast by the router to synchronize the wireless network. 50 is recommended in poor reception.

How it Works:


The term beacon signifies a specific data transmission from the wireless access point (AP), which carries the SSID, the channel number and security protocols such as WEP (Wired Equivalent Protection) or WPA (Wi-Fi Protected Access). This transmission does not contain the link layer address of another Wi-Fi device, therefore it can be received by any LAN client.The beacon frame, which is a type of management frame, can be likened with the "heartbeat" of a wireless LAN, enabling stations to establish and maintain communications in an orderly fashion.

What is a Beacon Interval
As mentioned above, the beacon interval is a fixed, configurable parameter. Typically, the beacon interval setting is not touched at all in the WLAN network installation phase, but the default value selected by the equipment supplier is used. If the beacon interval is long, maximum capacity in the Access Point is achieved. However, it will the take a long time for WLAN terminals to scan for Access Points in the area and to update RSSI and load information for already found Access Points. This obviously reduces terminal throughput and wastes battery. On the other hand, if the beacon interval in short, passive scanning performed by the WLAN terminals will be faster, but the overall capacity of the Access Point will be reduced.



**NOTE There are no special rules for sending beacons, and they must be sent using the mandatory 802.11 carrier sense multiple access / collision avoidance (CSMA/CA) algorithm. If another station is sending a frame when the beacon is to be sent, then the access point (or NIC in an ad hoc network) must wait. As a result, the actual time between beacons may be longer than the beacon interval. Clients, however, compensate for this inaccuracy by utilizing the timestamp found within the beacon packet information.


What is a Beacon?
A typical beacon frame is approximately fifty bytes long, with about half of that being a common frame header and cyclic redundancy checking (CRC) field. As with other frames, the header includes source and destination MAC addresses as well as other information regarding the communications process. The destination address is always set to all ones, which is the broadcast Medium Access Control (MAC) address. This forces all other stations on the applicable channel to receive and process each beacon frame. The CRC field provides error detection capability.


The beacon's frame body resides between the header and the CRC field and constitutes the other half of the beacon frame. Each beacon frame carries the following information in the frame body:

Beacon interval. This represents the amount of time between beacon transmissions. Before a station enters power save mode, the station needs the beacon interval to know when to wake up to receive the beacon (and learn whether there are buffered frames at the access point).


Timestamp. After receiving a beacon frame, a station uses the timestamp value to update its local clock. This process enables synchronization among all stations that are associated with the same access point.


Service Set Identifier (SSID). The SSID identifies a specific wireless LAN. Before associating with a particular wireless LAN, a client must have the same SSID configured as the access point. By default, access points include the SSID in the beacon frame to enable sniffing functions (such as that provided by Windows XP) to identify the SSID and automatically configure the wireless network interface card (NIC) with the proper SSID. DD-Wrt also has an option to disable the SSID from being broadcast in beacon frames to reduce security issues.


Supported rates. Each beacon carries information that describes the rates that the particular wireless LAN supports. For example, a beacon may indicate that only 1, 2, and 5.5Mbps data rates are available. As a result, an 802.11b station would stay within limits and not use 11 Mbps. With this information, stations can use performance metrics to decide which access point to associate with.


Parameter Sets. The beacon includes information about the specific signaling methods (such as frequency hopping spread spectrum, CTS Protection mode and RTS Threshold,direct sequence spread spectrum, etc.). For example, a beacon would include in the appropriate parameter set the channel number that an 802.11b access point is using. Likewise, a beacon belonging to frequency hopping network would indicate hopping pattern and dwell time.


Capability Information. This signifies requirements of stations that wish to belong to the wireless LAN that the beacon represents. For example, this information may indicate that all clients must use wired equivalent privacy (WEP) in order to participate on the network.


Traffic Indication Map (TIM). An access point periodically sends the TIM within a beacon to identify which stations using power saving mode have data frames waiting for them in the access point's buffer. The TIM identifies a station by the association ID that the access point assigned during the association process.


**NOTE Today beacon frames also contain a load information that informs WLAN terminals currently connected to a specific Access Point or considering making a handover to that Access Point about the load situation. This information helps the WLANterminals in making correct handover decision, in addition to the information from the comparisons of RSSI readings obtained by scanning, and thus ensures that WLAN traffic is divided more evenly between all Access Points in the area.



TWEAK:


By increasing the beacon interval, you can reduce the number of beacons and associated overhead, but that will likely delay the association and roaming process because stations scanning for available access points may miss the beacons.

You can decrease the beacon interval, which increases the rate of beacons. This will make the association and roaming process very responsive; however, the network will incur additional overhead and throughput will go down.

In addition, stations using power save mode will need to consume more power because they'll need to awaken more often, which reduces power saving mode benefits.
In an idle network, beacons dominate all other traffic.


Guide to tweaking:
The amount of overhead that the transmissions of beacon frames generate is substantial; however, the beacon serves a variety of functions. For example, each beacon transmission identifies the presence of an access point.

How a beacon interval impacts the client
By default, radio NICs passively scan all RF channels and listen for beacons coming from access points in order to find a suitable access point.
When a beacon is found, the radio NIC learns a great deal about that particular network. This enables a ranking of access points based on the received signal strength of the beacon, along with capability information regarding the network. The radio NIC can then associate with the most preferable access point. After association, the station continues to scan for other beacons in case the signal from the currently-associated access point become too weak to maintain communications. As the radio NIC receives beacons from the associated access point, the radio NIC updates its local clock to maintain timing synchronization with the access point and other stations. In addition, the radio NIC will abide by any other changes, such as data rate, that the frame body of the beacon indicates. The beacons also support stations implementing power saving mode. With infrastructure networks, the access point will buffer frames destined for sleeping stations and announce which radio NICs have frames waiting through the TIM (DTIMS) that's part of the beacon


Do clients send beacon frames too??...
As apposed to beacons sent out by AP's, Clients send out "probe request" frames; It's like an opposite to a beacon, clients use a probe request packets to play there role in the 802.11 WLAN. An 802.11 probe response frame is very similar to a beacon frame, except that probe responses don't carry the TIM info and are only sent in response to a probe request. A client may send a probe request frame to trigger a probe response when the client needs to obtain information from another client on the same WLAN. A client, for instance, will broadcast a probe request when using active scanning to determine which access points are within range for possible association. Some sniffing software (e.g., NetStumbler) tools send probe requests so that access points will respond with desired info.

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stephensuley
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PostPosted: Wed May 06, 2009 16:45    Post subject: Reply with quote
And CTS has now been updated with the following;

CTS Protection mode
The default mode value is set to Auto.


The help file says...
When set to Auto, a protection mechanism will ensure that your Wireless-B devices will connect to the Wireless-G router when many Wireless-G devices are present. However, performance of your Wireless-G devices may be decreased.


How it works:
CTS Protection mode is a is a protection mechanism that operates on the physical (PHY) level frame. At a very high level summary of the process when multiple devices are connected to an access point, they can occasionally be transmitting data to the access point at the same time because neither one can see the other client well enough to determine if it is transmitting on the channel or not. When this happens, the AP will discard both pieces of colliding data, thus contributing to error rates. CTS (clear to send) protection skirts this issue by delegating which device gets to transmit at a given time.


CTS Protection mode and DD-wrt:
In its default configuration dd-wrt uses it as a to provide a way of ensuring coexistence between the legacy and the new wifi devices. Adding to that by using CTS protection mode and modifying RTS threshold value you can tweak the operation of the CTS protection mechanism this can then be combined with the Fragmentation Threshold tweak to help troubleshoot\fix connectivity and\or performance issues etc. Remember tweaking the CTS protection process by manipulating the RTS and the Fragmentation Threshold value often comes at a price usually by decreasing the overall throughput to the WLAN.



Once CTS Protection mode is configured correctly within your WLAN environment there are specific scenarios that occur and the software will activate the CTS protection mechanisms;

Here are a few examples of what triggers CTS to be employed by the dd-wrt router software.


CTS Protection trigger 1; - NON-default dd-wrt behavior
A client that wants to use the radio channel to send data packet(s) of a size that is equal or above the defined RTS threshold value.

CTS Protection trigger 2; -default dd-wrt behavior
A 802.11g client attempts to connect to a SSID that is using channel bonding. Transmissions using a 40 MHz channel in the presence of 802.11a or 802.11g clients require using CTS protection mode. This will apply the CTS protection mechanism on both 20 MHz halves of the 40 MHz channel, to prevent interference with legacy devices and allow proper operation of the 802.11a and 802.11g clients.

CTS Protection trigger 3; -default dd-wrt behavior
If you are running in mixed wireless mode on a 802.11n router and you have 802.11b clients in your environment. CTS Protection is used to allow the 802.11b client to operate correctly and also not to interfere with the operation of the 802.11a,g, and N client transmissions.

Also;
- An 11b device associates to the AP. - same as trigger 3
- An 11b AP on the same channel can be heard by the AP - variant on trigger 3
- The AP hears an 11g AP that is in protection because of an 11b device associated. -another variation of the trigger 3 event.




**NOTE: Trigger 1 will never happen on the dd-wrt default configuration due to the the default values of the RTS Threshold being 2347 and the the Fragmentation Threshold value being 2346. Based on the data packet fragmentation threshold default value at 2346 in size dd-wrt will apply fragmentation to all packets meeting this criteria. Because of this fragmentation process the 2347 packet size needed to trigger the RTS threshold is never reached.


For a closer look at what happens in one of these cases lets look at a case like trigger number 1 list above and the steps in the CTS protection process.


Example. A client that wants to use the radio channel to send data packet(s) of a size that is equal or above the defined RTS threshold value.


Steps in the CTS Protection mode process for the above example.

1.) The client wishing to send date over the channel first sends an RTS (request to send) packet to the AP.

2.) As the AP broadcast it beacons packet over the WLAN as part of its normal operation, The beacon packet has information within it that declares to all the clients on the entire WLAN not to try and send any information for a specified period of time. The AP then sends a CTS packet to the client that requested the CTS in the first place. The AP has made a single client the "owner" of the wifi channel and then the AP listens only to that client until it is done transmitting; its in protection mode.

3.)The process is repeated for all request to transfer data,which for whatever reason triggers the CTS protection mechanisms, on a first come first serve basis.



TWEAK:
Implementing additional CTS Protection mode triggers and there frequency of operation on top of the default dd-wrt CTS protection mode configuration;

1.) The AP running dd-wrt has the CTS Protection mode is set to Auto by default and then you could adjust the RTS threshold value to something lower then 2346 (Which is the default fragmentation threshold value on dd-wrt) on the AP.

2.) All clients connected to the dd-wrt AP are configured for CTS\RTS mode as apposed to setting of "disabled" or "CTS-Self" mode.


***NOTE Typically the The RTS Threshold value on dd-wrt is only lowered when needed to address or troubleshoot some sort of connectivity or performance issue with a client or all clients on a WLAN. Adjusting the value is a balancing act between getting your problem fixed and losing overall WLAN speed. The more times CTS protection mode is triggered in a period of time "its frequency" the more impact it will have; good or bad. So start with 2340, then 2320, 2300 etc...


Guide when to use and why.

-If your trying to tweak out every drop of performance in an ideal setup then you can disable this on the AP and clients. Test again to see if it helps for better results, it should.

-If you want to try 40MHz with your 802.11n clients you might want to start with CTS Protection set to Auto. You do this in case you have 802.11a or g or even some N clients that do not support 40GHz transmissions or "channel bonding" as it is sometimes called.

-If you have a 802.11n based router running in mixed wireless mode that you want to connect 802.11b clients you need to have CTS protection mode set to Auto meaning enabled.

-If CTS Protection makes things faster a network redesign might be needed.

-"CTS to self" based protection - an alternate implementation method of CTS; where by the device willing to send frames over the WLAN first sends a CTS frame to itself. "CTS to self" based protection has less overhead, but it must be taken into account that this only protects against devices receiving CTS frame (e.g. if there are 2 "hidden" stations, there is no use for them to use "CTS to self" protection, because they will not be able to receive CTS sent by other station - in this case stations must use RTS/CTS so that other station knows not to transmit by seeing CTS transmitted by AP).If you have set the CTS protection mode to disabled on the dd-wrt AP, then this is a good choice for the client configuration.

_________________
Location (urban) - 1x Linksys EA8500 (AP wlan0 & wlan1 enabled)
1x Asus 68u (Repeater Bridge w/VAP) - wl0 disabled
1x Asus 87u (Client Bridge) - wl1 disabled


Latest and greatest builds Wink
stephensuley
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Joined: 09 Feb 2008
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PostPosted: Thu May 07, 2009 17:39    Post subject: Reply with quote
RTS Threshold is now updated. Thoughts?

RTS Threshold
Range: 0 - 2347. Default value of 2347 (bytes).


The Help file says..
The router sends Request to Send (RTS) frames to a particular receiving station and negotiates the sending of a data frame. After receiving an RTS, the wireless station responds with a Clear to Send (CTS) frame to acknowledge the right to begin transmission.


How it Works:
The RTS Threshold value is a configurable parameter within the CTS Protection mechanism. The RTS threshold is used as a trigger to engage the back and forth of RTS and CTS messages between AP and client. The triggers purpose is a type of “handshaking” approach that provides and additional layer of control over the use of the shared medium, or in the case of DD-WRT the “Radio Channel” or WLAN. If enabled, A node (client) wishing to send data initiates the process by sending a Request to Send frame (RTS).


How the RTS Threshold value works in DD-WRT.
As discussed in the CTS Protection mode section of this document, when a packet that a DD-WRT access point is transmitting is larger than the RTS threshold set in the configuration, DD-WRT will initiate the CTS Protection mode “handshaking” function. If the network packet being sent is smaller or fragmented to a size lower than the preset RTS threshold size, the CTS Protection mode mechanism will still not be enabled for that packet. Note if the packet size happens to be equal to the threshold, DD-WRT will not use CTS.


Tweak:
In DD-WRT, the default configuration after a flash sets the CTS Protection mode not to get triggered to protect transmissions by RTS. This is due to the fact that Sending RTS frames is turned off by default (threshold >=2347bytes). If the packet size the node wants to transmit is larger than the threshold, the RTS/CTS handshake gets triggered. If the packet size is equal to or less than threshold the data frame gets sent immediately.

The method for enabling RTS-CTS triggers on DD-WRT is different than with client NICs. For DD-WRT, you enable RTS-CTS handshaking triggers within WebGUI by setting a specific packet size threshold (0 - 2347 bytes) in the user configuration interface; only minor modifications are recommended.

Set this value to a 2340bytes as a start, test, then if needed try a lower value….etc…

Save. Apply. Reboot.

Rollback
Set the value back to its default value of 2347bytes and disable RTS threshold triggers in the CTS Protection mode operation on the router.

**A 30/30/30/ hard reset will also set this parameter back to the default value.

_________________
Location (urban) - 1x Linksys EA8500 (AP wlan0 & wlan1 enabled)
1x Asus 68u (Repeater Bridge w/VAP) - wl0 disabled
1x Asus 87u (Client Bridge) - wl1 disabled


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jtrosky
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PostPosted: Thu May 07, 2009 20:19    Post subject: Reply with quote
vtphilk wrote:
My vote is for add to the wiki.

And I disagree too technical. If you are not interested in the 'too technical' stuff you probably should not be mucking with advanced wireless settings Smile


I also think the technical stuff should stay. If you don't understand it, it's a good way to start understanding it! After all, if some of it is too technical for you, you can skip those parts!

Please, keep the technical stuff there and let the reader decide which info they want to use!
stephensuley
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Joined: 09 Feb 2008
Posts: 641
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PostPosted: Thu May 07, 2009 21:05    Post subject: Reply with quote
jtrosky wrote:
vtphilk wrote:
My vote is for add to the wiki.

And I disagree too technical. If you are not interested in the 'too technical' stuff you probably should not be mucking with advanced wireless settings Smile


I also think the technical stuff should stay. If you don't understand it, it's a good way to start understanding it! After all, if some of it is too technical for you, you can skip those parts!

Please, keep the technical stuff there and let the reader decide which info they want to use!


Thank you and thank everyone for the feedback and suggestions.

_________________
Location (urban) - 1x Linksys EA8500 (AP wlan0 & wlan1 enabled)
1x Asus 68u (Repeater Bridge w/VAP) - wl0 disabled
1x Asus 87u (Client Bridge) - wl1 disabled


Latest and greatest builds Wink
stephensuley
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PostPosted: Sat May 09, 2009 19:42    Post subject: Reply with quote
The guide was updated with this information please let me know if you find errors or want to contribute.


Wireless Channel
Default values are Channel Selection is 6, and channel width is 20MHz.


Help File says....
Select the appropriate channel from the list provided to correspond with your network settings (in North America between channel 1 and 11, in Europe 1 and 13, in Japan all 14 channels). All devices in your wireless network must use the same channel in order to function correctly. Try to avoid conflicts with other wireless networks by choosing a channel where the upper and lower three channels are not in use.


How it works...
IEEE 802.11 is a set of standards that are published for the purposes of carrying out wireless local area network (WLAN) computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are implemented by the IEEE LAN/MAN Standards Committee ( aka "IEEE 802").


2.4GHz Channels
2.4GHz band in the 802.11 standard uses radio frequencies in the range of 2412-2484 MHz. 802.11 splits up the frequencies within the band into 14 radio channels, numbered 1-14. These are the 14 channels designated in the 2.4 GHz range spaced 5 MHz apart (with the exception of a 12 MHz spacing before Channel 14). The frequency range of a channel partially overlaps with the next one, so not all the channels are therefore independent. On a 2.4GHz band radio in DD-WRT routers, channels 1, 6 and 11 have no overlap with each other; those three channels are known in the wireless community as the "standard" for wireless channel independence within the 2.4GHz band.

In North America this 2.4GHz "band" is implemented by dividing the 2.4GHz band into 13 channels each with a width of 22 MHz but also spaced only 5 MHz apart, with channel 1 centred on 2412 MHz and 13 on 2472, to which Japan adds a 14th channel 12 MHz above channel 13.

**NOTE - The specifics of the frequency range and how channels are allocated is regulated by country. Usually constrained in part by how each country allocates radio spectrum to various services. For example, Japan has #1-#14, Europe #1-#13 and the FCC in the US allows #1-#11 channels all with in the same band. DD-WRT allows the use of all channels; this doesn't mean your client wireless adapter can support channels outside of its licensed region.



5GHz Channels


[not finished]


How it works in DD-WRT:
To configure your radio channels in the WebGUI you browse to the "Basic Settings" under the "Wireless" page on your DD-WRT router.

If you have dual band router (ie. Two Radios inside the router) you will see two sections for configurations listed in this page with the headings as "wl0" for the 2.4GHz radio and "wl1" for the 5GHz radio.

DD-WRT uses two terms to describe the radios modes or operation;

Wireless mode, this determines if the router will be used as an Access Point, Repeater, Client or in an Ad-hoc configuration mode. Channel options are only avalaible to a router running in AP or Ad-Hoc wireless mode.

Wireless Network mode, this setting determines what wireless protocols will be offered to the wireless clients that try to connect to the router. Depending on the wireless network mode your radio is configured for DD-WRT will have additional channel options for you to configure if you choose.


For this example of the channel options lets exmine DD-WRT running on "Linksys WRT610n" hardware which happens to be a 802.11n Dual-Band Router.


wl0 radio ( 2.4GHz band )


802.11b/g and n and mixed modes of all three are offered by DD-WRT running on top of 802.11n hardware , no matter which mode is selected the 2.4GHz band radio can only use radio frequencies in the range of 2412-2484 MHz (channels 1 to 14);

Wireless Mode: AP
Wireless Network Mode: B-Only, G-Only and BG-Mixed

DD-WRT channel options when configured in the wireless modes above:

1) - Channel Selection
Channel selections offered by DD-WRT are 1 to 14 or the DD-WRT "Auto" channel selection feature.

Wireless Mode: AP
Wireless Network Mode: N-Only and Mixed

DD-WRT channel options when configured in the wireless modes above:

1) - Channel Selection
Channel selections offered by DD-WRT are 1 to 14 or the DD-WRT "Auto" channel selection feature.

2) - Channel Width
For 802.11n connected clients channel width value(20MHz or 40MHz) determines if DD-WRT will force the use the "channel bonding" feature using the 2.4GHz radio. "Auto" can be selected as well to use the DD-WRT of automatic selection of channel width . If "Auto" is selected for the channel width value the channel selection value will be reset to use the Auto feature as well.

3) - Wide Channel selection.
If 40MHz is selected as the channel width the wireless channel will be bonded with another channel to provide more preformance. The channel the router uses to bond to the orgional channel selection is known as the "wide channel". The orgional channel selection bonds with either a channel above or below itself. DD-WRT using the "Wide Channel" value will give a user the option to select the upper or lower channel in refence to the main channel selection.


***NOTE - If 40MHz is selected as the channel width value in mixed mode wireless network configuration the use of CTS protection mode must enabled. This feature provides a mechonism for 802.11g clients to be able to connect and operate correctly on the same 2.4GHz radio.



wl1 radio ( 5GHz band )[/b]


802.11a, n and mixed modes of both are offered by DD-WRT running on top of 802.11n hardware , no matter which mode is selected the 5GHz band radio can only use radio frequencies in the range of

Wireless Mode: AP
Wireless Network Mode: A-Only

DD-WRT channel options when configured in the wireless modes above:

1) - Channel Selection
Channel selections offered by DD-WRT are 34 to 216 or the DD-WRT "Auto" channel selection feature.



Wireless Mode: AP
Wireless Network Mode: N-Only and NA-Only

DD-WRT channel options when configured in the wireless modes above:

1) - Channel Selection
Channel selections offered by DD-WRT are 1 to 14 or the DD-WRT "Auto" channel selection feature.

2) - Channel Width
For 802.11n connected clients channel width value(20MHz or 40MHz) determines if DD-WRT will force the use the "channel bonding" feature using the 2.4GHz radio. "Auto" can be selected as well to use the DD-WRT of automatic selection of channel width . If "Auto" is selected for the channel width value the channel selection value will be reset to use the Auto feature as well.

3) - Wide Channel selection.
If 40MHz is selected as the channel width the wireless channel will be bonded with another channel to provide more preformance. The channel the router uses to bond to the orgional channel selection is known as the "wide channel". The orgional channel selection bonds with either a channel above or below itself. DD-WRT using the "Wide Channel" value will give a user the option to select the upper or lower channel in refence to the main channel selection.

***NOTE - If 40MHz is selected as the channel width value in mixed mode wireless network configuration the use of CTS protection mode must enabled. This feature provides a mechonism for 802.11a clients to be able to connect and operate correctly on the same 5GHz radio.

_________________
Location (urban) - 1x Linksys EA8500 (AP wlan0 & wlan1 enabled)
1x Asus 68u (Repeater Bridge w/VAP) - wl0 disabled
1x Asus 87u (Client Bridge) - wl1 disabled


Latest and greatest builds Wink
ad5mb
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Joined: 12 Oct 2008
Posts: 386

PostPosted: Sat May 09, 2009 20:21    Post subject: Reply with quote
Quote:
wl1 radio ( 5GHz band )[/b]


presence of [/b] indicates that you meant to make this bold but it didn't take

you might want to note that you can't select a channel in repeater mode. it will come up.[/list]

_________________
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stephensuley
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Joined: 09 Feb 2008
Posts: 641
Location: Canada

PostPosted: Sat May 09, 2009 21:16    Post subject: Reply with quote
ad5mb wrote:
Quote:
wl1 radio ( 5GHz band )[/b]


presence of [/b] indicates that you meant to make this bold but it didn't take

you might want to note that you can't select a channel in repeater mode. it will come up.[/list]



Good idea....will update...thanks.

_________________
Location (urban) - 1x Linksys EA8500 (AP wlan0 & wlan1 enabled)
1x Asus 68u (Repeater Bridge w/VAP) - wl0 disabled
1x Asus 87u (Client Bridge) - wl1 disabled


Latest and greatest builds Wink
kocoman
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Joined: 27 Oct 2006
Posts: 58

PostPosted: Mon May 18, 2009 17:18    Post subject: Reply with quote
Is this the only place where the guide is posted? So this reference guide is put into the flash bin file?

I have a question about CTS Protection..

According to the Definite guide to 802.11..

Technology Transactions per second Mbps of TCP payload throughput Transactional speed relative to 802.11b

11g, 54 Mbps/no protection 2,336 27.3 4.9
11g, 54 Mbps/CTS-to-self protection 1,113 13.0 2.3
11g, 54 Mbps/RTS/CTS protection 750 8.8 1.6

So turning on the protection slows down the network, why is it good to turn it on? stop wireless random disconnects?

I am trying to improve ping time between my radio card and the dd-wrt router. does adjusting the CTS/RTS help? I have already set my network to force 802.11g only. I want to have ping times of 1ms or less like on the wired network.

Thanks
stephensuley
DD-WRT Guru


Joined: 09 Feb 2008
Posts: 641
Location: Canada

PostPosted: Fri May 22, 2009 20:19    Post subject: Reply with quote
Updated Basic Rate..


Basic Rate
The default value is set to Default.


The help file says...
Depending on the wireless mode you have selected, a default set of supported data rates will be selected. The default setting will ensure maximum compatibility with all devices.1-2Mbps.


How it works
The Basic Rate set is the rates that all clients that want to associate with a given access point must support. For backward compatibility with 802.11b clients, the Basic Rate set is generally 1, 2, 5.5 and 11Mbps. This information is transmitted by an access point as mandatory rates in the Supported Rates element of various management frames.


To help understand look at it this way..as Basic Rate is a setting that is used to determine the minimum requirements the adapter must support to be able to connect successfully whereas Transmission Rate is the maximum limits of the WLAN which the adapter must adhere to , for a successful connection. The Transmit Rate setting is used to set the fastest rate that an AP or wireless router will send data. It can be used to force a lower rate in order to trade off speed for more reliable connection in WLANs where many clients are operating at low signal levels.


NOTE**** Some very old 802.11b clients adapters may only be able to associate with APs advertising a 1, 2 Mbps basic rate set. This is one of the main reasons why dd-wrt allows you to change the Basic Rate setting.



TWEAK:
You would only modify this value as one of the troubleshooting steps if you have a known 802.11b client adapter that is unable to connect to your WLAN, you can modify the default value for the Basic Rate to accommodate the legacy adapter.

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Location (urban) - 1x Linksys EA8500 (AP wlan0 & wlan1 enabled)
1x Asus 68u (Repeater Bridge w/VAP) - wl0 disabled
1x Asus 87u (Client Bridge) - wl1 disabled


Latest and greatest builds Wink
ad5mb
DD-WRT User


Joined: 12 Oct 2008
Posts: 386

PostPosted: Sat May 23, 2009 2:18    Post subject: Reply with quote
Quote:
So turning on the protection slows down the network, why is it good to turn it on? stop wireless random disconnects?


it's a troubleshooting tool.

clients listen to the channel to see if it's clear. if it's clear, they transmit.

in a very large net with clients far from the AP you can have clients that can hear the AP but not each other. so they talk over each other, and nothing gets done.

CTS imposes central control. If the network is faster with CTS on it needs to be redesigned with multiple APs.

CTS does not solve problems in the long run. it identifies problems, and is a short term patch for a situation that needs a long term solution.

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Conventional wisdom among radio guys is that $1 spent on antennas is worth $10 spent on amplifiers. Solve RF problems with antennas to the greatest extent possible before increasing power.
stephensuley
DD-WRT Guru


Joined: 09 Feb 2008
Posts: 641
Location: Canada

PostPosted: Sun Jul 26, 2009 3:45    Post subject: Reply with quote
Anyone have anything new to add?
_________________
Location (urban) - 1x Linksys EA8500 (AP wlan0 & wlan1 enabled)
1x Asus 68u (Repeater Bridge w/VAP) - wl0 disabled
1x Asus 87u (Client Bridge) - wl1 disabled


Latest and greatest builds Wink
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