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Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots.^[1] The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium (e.g. radio frequency channel) while using only a part of its channel capacity. TDMA is used in the digital 2Gcellular systems such as Global System for Mobile Communications (GSM), IS-136, Personal Digital Cellular (PDC) and iDEN, and in the Digital Enhanced Cordless Telecommunications (DECT) standard for portable phones. TDMA was first used in satellite communication systems by Western Union in its Westar 3 communications satellite in 1979. It is now used extensively in satellite communications,^[2][3][4][5]combat-net radio systems, and passive optical network (PON) networks for upstream traffic from premises to the operator. For usage of Dynamic TDMA packet mode communication, see below.

TDMA is a type of time-division multiplexing (TDM), with the special point that instead of having one transmitter connected to one receiver, there are multiple transmitters. In the case of the uplink from a mobile phone to a base station this becomes particularly difficult because the mobile phone can move around and vary the timing advance required to make its transmission match the gap in transmission from its peers.

• 2TDMA in mobile phone systems

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Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube. Active oldest votes. Up vote 1 down vote accepted. A time slot, is a regular time during the day, it may be several hours, however, never longer than 8 hours. In general a time slot more or less an hour, and you may set more than one aside for something. Total Short Preamble transfer time is a constant at 96 usec (microseconds) What does this all mean to the end user? Most access points (AP) and broadband Wi-Fi routers are configured for a Long Preamble or have a setting that automatically detects the preamble and adjusts accordingly.

TDMA characteristics[edit]

• Shares single carrier frequency with multiple users
• Non-continuous transmission makes handoff simpler
• Slots can be assigned on demand in dynamic TDMA
• Less stringent power control than CDMA due to reduced intra cell interference
• Higher synchronization overhead than CDMA
• Advanced equalization may be necessary for high data rates if the channel is 'frequency selective' and creates Intersymbol interference
• Cell breathing (borrowing resources from adjacent cells) is more complicated than in CDMA
• Frequency/slot allocation complexity
• Pulsating power envelope: interference with other devices

TDMA in mobile phone systems[edit]

2G systems[edit]

Most 2G cellular systems, with the notable exception of IS-95, are based on TDMA. GSM, D-AMPS, PDC, iDEN, and PHS are examples of TDMA cellular systems. GSM combines TDMA with Frequency Hopping and wideband transmission to minimize common types of interference.

In the GSM system, the synchronization of the mobile phones is achieved by sending timing advance commands from the base station which instructs the mobile phone to transmit earlier and by how much. This compensates for the propagation delay resulting from the light speed velocity of radio waves. The mobile phone is not allowed to transmit for its entire time slot, but there is a guard interval at the end of each time slot. As the transmission moves into the guard period, the mobile network adjusts the timing advance to synchronize the transmission.

Initial synchronization of a phone requires even more care. Before a mobile transmits there is no way to actually know the offset required. For this reason, an entire time slot has to be dedicated to mobiles attempting to contact the network; this is known as the random-access channel (RACH) in GSM. The mobile attempts to broadcast at the beginning of the time slot, as received from the network. If the mobile is located next to the base station, there will be no time delay and this will succeed. If, however, the mobile phone is at just less than 35 km from the base station, the time delay will mean the mobile's broadcast arrives at the very end of the time slot. In that case, the mobile will be instructed to broadcast its messages starting nearly a whole time slot earlier than would be expected otherwise. Finally, if the mobile is beyond the 35 km cell range in GSM, then the RACH will arrive in a neighbouring time slot and be ignored. It is this feature, rather than limitations of power, that limits the range of a GSM cell to 35 km when no special extension techniques are used. By changing the synchronization between the uplink and downlink at the base station, however, this limitation can be overcome.^{[citation needed]}

3G systems[edit]

Although most major 3G systems are primarily based upon CDMA,^[6] time-division duplexing (TDD), packet scheduling (dynamic TDMA) and packet oriented multiple access schemes are available in 3G form, combined with CDMA to take advantage of the benefits of both technologies.

While the most popular form of the UMTS 3G system uses CDMA and frequency division duplexing (FDD) instead of TDMA, TDMA is combined with CDMA and time-division duplexing in two standard UMTS UTRA.

TDMA in wired networks[edit]

The ITU-TG.hn standard, which provides high-speed local area networking over existing home wiring (power lines, phone lines and coaxial cables) is based on a TDMA scheme. In G.hn, a 'master' device allocates 'Contention-Free Transmission Opportunities' (CFTXOP) to other 'slave' devices in the network. Only one device can use a CFTXOP at a time, thus avoiding collisions.FlexRay protocol which is also a wired network used for safety-critical communication in modern cars, uses the TDMA method for data transmission control.

Comparison with other multiple-access schemes[edit]

In radio systems, TDMA is usually used alongside frequency-division multiple access (FDMA) and frequency division duplex (FDD); the combination is referred to as FDMA/TDMA/FDD. This is the case in both GSM and IS-136 for example. Exceptions to this include the DECT and Personal Handy-phone System (PHS) micro-cellular systems, UMTS-TDD UMTS variant, and China's TD-SCDMA, which use time-division duplexing, where different time slots are allocated for the base station and handsets on the same frequency.

A major advantage of TDMA is that the radio part of the mobile only needs to listen and broadcast for its own time slot. For the rest of the time, the mobile can carry out measurements on the network, detecting surrounding transmitters on different frequencies. This allows safe inter frequency handovers, something which is difficult in CDMA systems, not supported at all in IS-95 and supported through complex system additions in Universal Mobile Telecommunications System (UMTS). This in turn allows for co-existence of microcell layers with macrocell layers.

CDMA, by comparison, supports 'soft hand-off' which allows a mobile phone to be in communication with up to 6 base stations simultaneously, a type of 'same-frequency handover'. The incoming packets are compared for quality, and the best one is selected. CDMA's 'cell breathing' characteristic, where a terminal on the boundary of two congested cells will be unable to receive a clear signal, can often negate this advantage during peak periods.

A disadvantage of TDMA systems is that they create interference at a frequency which is directly connected to the time slot length. This is the buzz which can sometimes be heard if a TDMA phone is left next to a radio or speakers.^[7] Another disadvantage is that the 'dead time' between time slots limits the potential bandwidth of a TDMA channel. These are implemented in part because of the difficulty in ensuring that different terminals transmit at exactly the times required. Handsets that are moving will need to constantly adjust their timings to ensure their transmission is received at precisely the right time, because as they move further from the base station, their signal will take longer to arrive. This also means that the major TDMA systems have hard limits on cell sizes in terms of range, though in practice the power levels required to receive and transmit over distances greater than the supported range would be mostly impractical anyway.

Dynamic TDMA[edit]

In dynamic time-division multiple access (dynamic TDMA), a scheduling algorithm dynamically reserves a variable number of time slots in each frame to variable bit-rate data streams, based on the traffic demand of each data stream. Dynamic TDMA is used in

• HIPERLAN/2 broadband radio access network.
• IEEE 802.16a WiMax
• Military Radios / Tactical Data Link

See also[edit]

• Channel access methods (CAM)
• Duplex (telecommunications) (FDD, TDD)

References[edit]

1. ^Guowang Miao; Jens Zander; Ki Won Sung; Ben Slimane (2016). Fundamentals of Mobile Data Networks. Cambridge University Press. ISBN1107143217.
2. ^Maine, K.; Devieux, C.; Swan, P. (November 1995). Overview of IRIDIUM satellite network. WESCON'95. IEEE. p. 483.
3. ^Mazzella, M.; Cohen, M.; Rouffet, D.; Louie, M.; Gilhousen, K. S. (April 1993). Multiple access techniques and spectrum utilisation of the GLOBALSTAR mobile satellite system. Fourth IEE Conference on Telecommunications 1993. IET. pp. 306–311.
4. ^Sturza, M. A. (June 1995). Architecture of the TELEDESIC satellite system. International Mobile Satellite Conference. 95. p. 214.
5. ^'ORBCOMM System Overview'(PDF).
6. ^K. Jagannatham, Aditya (2016). Principles of Modern Wireless Communication Systems. McGraw-Hill Education.
7. ^'Minimize GSM buzz noise in mobile phones'. EETimes. July 20, 2009. Retrieved November 22, 2010.

From DD-WRT Wiki

You are here: Wiki mainpage / Scripting / SSH/Telnet & The CLI / wl (wireless options) command

'wl' is probably the most important tool in the routers firmware to access and control wireless hardware. It can be accesed from a telnet or SSH terminal or through the Web Interface. Tools such as Wiviz or Kismet Server/Drone use it to configure the radios, monitor packets and extract information directly from them.

[edit]Setup

No setup is required as 'wl' comes with all Broadcom DD-WRT installations.

(For Atheros Hardware, this functionality is absent/less developed, and users will need to use the 'ifconfig' and 'wl_atheros' commands instead.

See these threads: wl command 'not found', Regarding 'wl command not found' and others)

[edit]Usage

Most of the wireless options can be accessed using the program 'wl' via the console window. This program has many more options than our WRT is able to process. Some can only be used in Client Mode and others only in Access Point (AP) Mode.

Note For NEWD-2 builds, you must specify the interface when performing a command.

Example:

If you have multiple radios, then each one will have it's own interface, i.e eth2, eth3

[edit]Common Tasks

[edit]Toggle radio on/off, restart, etc

• ~ # wl up

reinitialize adapter and mark as up

• ~ # wl down

reset adapter and mark as down

• ~ # wl out

mark adapter down but do not reset hardware.

• ~ # wl radio

toggle radio on/off

• ~ # wl restart

restart the driver. (Driver must already be down)

[edit]Alphabetical list of commands

[edit]aciargs

Get/Set various aci tuning parameters. Choices are:

[edit]addwep

Set an encryption key.

[edit]aes

Set AES options.

[edit]antdiv

Sets which antenna to use to receive on.

Note: can be used in conjunction with 'wl txant' to set the transmit antenna.

[edit]ap

Set AP mode: 0 (STA) or 1 (AP)

[edit]assoc

Print information about current network association. (also known as 'status')

[edit]assoclist

AP only: Get the list of associated MAC addresses.

[edit]atten

Set the transmit attenuation for B band.

[edit]authe_sta_list

Get authenticated sta mac address list

[edit]autho_sta_list

Get authorized sta mac address list

[edit]authorize

Restrict traffic to 802.1X packets until 802.1X authorization succeeds

[edit]band

Returns or sets the current band

[edit]bands

Return the list of available 802.11 bands

[edit]bssid

Get the BSSID value, error if STA and not associated

[edit]cap

Display WL Capabilities

[edit]channel

Set the channel:

[edit]channel_qa

Get last channel quality measurment

[edit]channel_qa_start

Start a channel quality measurment

[edit]clk

set board clock state. return error for set_clk attempt if the driver is not down

[edit]cmds

Generates a short list of all available wl commands.

(Most wireless options can be set and monitored via the wl console program.)

This program has many more options than our WRT is able to process.
Some can only be used in Client Mode and others only in Access Point (AP) Mode.

[edit]country

Select Country code for use with 802.11d

[edit]constraint

Send an 802.11h Power Constraint IE

[edit]crsuprs

Manufacturing test: set carrier suppression mode.

[edit]csa

Send an 802.11h channel switch anouncement

[edit]cwmin

Set the cwmin. (integer [1, 255])

[edit]cwmax

Set the cwmax. (integer [256, 2047])

[edit]disassoc

Disassociate from the current BSS/IBSS.

[edit]dtim

Get/Set DTIM

[edit]dump

print driver software state and chip registers to stdout

[edit]deauthenticate

Deauthenticate a STA from the AP with optional reason code (AP ONLY)

[edit]deauthorize

Do not restrict traffic to 802.1X packets until 802.1X authorization succeeds

[edit]eap

Restrict traffic to 802.1X packets until 802.1X authorization succeeds

[edit]chanlist

Return valid channels for the current settings is nice.

[edit]channels

Return valid channels for the current settings.

[edit]channels_in_country

Return valid channels for the country specified.

[edit]curpower

Return current tx power settings

[edit]evm

Start an EVM test on the given channel, or stop EVM test.

[edit]frameburst

Disable/Enable frameburst mode

[edit]fasttimer

Get/Set High frequency watchdog timeout (tx_power) [15 sec]

[edit]frag

Set the fragmentation threshhold. (integer [256, 2346])

[edit]fqacurcy

Manufacturing test: set frequency accuracy mode.

[edit]glacialtimer

Get/Set Very Low frequency watchdog timeout (measurelo) [120 sec]

[edit]gmode

Set the 54g Mode

• LegacyB -
• Auto [default]
• BDeferred -
• Performance -
• LRS - Limited Rate Support used to improve compatibility with older 802.11b cards.
• Afterburner -

[edit]gmode_protection

Get G protection mode.

[edit]gmode_protection_control

Get/Set 11g protection mode control alg.

[edit]gmode_protection_cts

Get/Set 11g protection type to CTS

[edit]gmode_protection_override

Get/Set 11g protection mode override.

[edit]ignore_bcns

AP only (G mode): Check for beacons without NONERP element (0=Examine beacons, 1=Ignore beacons)

[edit]int

Interrupt Test - remember to precede by 'wl down' and follow by 'wl up'

[edit]interference

Get/Set interference mitigation mode. Choices are:

[edit]infra

Set Infrastructure mode: 0 (ad-hoc IBSS) or 1 (managed BSS)

[edit]isup

Get driver operational state (0=down, 1=up)

[edit]join

Join a specified network SSID.

Join syntax is:

[edit]keys

Prints a list of the current WEP keys

[edit]lazywds

Set or get 'lazy' WDS mode (dynamically grant WDS membership to anyone).

[edit]lbt

Loopback Test - remember to precede by 'wl down' and follow by 'wl up'

[edit]legacy_erp

Get/Set 11g legacy ERP inclusion (0=disable, 1=enable)

[edit]locale

OBSOLETE: use 'wl country'

[edit]lrl

lrlSet the long retry limit. (integer [1, 255])

[edit]mac

Set or get the list of source MAC address matches.

[edit]macmode

Set the mode of the MAC list.

[edit]macreg

Get/Set any mac registers(include IHR and SB)

[edit]measure_req

Send an 802.11h measurement request.

[edit]monitor

set monitor mode

[edit]mrate

force a fixed multicast rate:

• After using wl mrate set the multicast rate, how to check if it has been correctly setted? How to get the current mrate value? Skygunner

[edit]msglevel

set driver console debugging message bitvector

[edit]noise

Get noise (moving average) right after tx in dBm

[edit]nvdump

print nvram variables to stdoutNo function.Use nvram show!

[edit]nvget

get the value of an nvram variable

[edit]nvset

set an nvram variable

[edit]passive

Puts scan engine into passive mode

[edit]phylist

Return the list of available phytypes

[edit]phyreg

Get/Set a phy register.

[edit]radioreg

Get/Set a radio register.

[edit]phytype

Get phy type

[edit]pktcnt

Get the summary of good and bad packets.

[edit]plcphdr

Set the plcp header.

[edit]PM

set driver power management mode:

[edit]powerindex

Set the transmit power for A band(0-63).

[edit]prb_resp_timeout

Get/Set probe response timeout

[edit]primary_key

Set or get index of primary key

[edit]promisc

set promiscuous mode ethernet address reception

[edit]pwr_percent

Get/Set power output percentage

[edit]quiet

Send an 802.11h quiet command.

[edit]radar

Enable/Disable radar

[edit]radio

When used without arguments, toggles radio on/off.

[edit]rate

force a fixed rate:

[edit]ratedump

print driver rate selection tunables and per-scb state to stdout

[edit]rateparam

set driver rate selection tunables

[edit]rateset

Returns or sets the supported and basic rateset.

[edit]reboot

Reboot platform

[edit]revinfo

get hardware revision information

[edit]regulatory

Get/Set regulatory domain mode (802.11d). Driver must be down.

[edit]roam_delta

Set the roam candidate qualification delta. (integer)

[edit]rm_rep

Get current radio measurement report

[edit]rm_req

Request a radio measurement of type basic, cca, or rpi

G Mode Short Slot Time Card

[edit]rmwep

Remove the encryption key at the specified key index.

[edit]roam_scan_period

Set the roam candidate qualification delta. (integer)

[edit]roam_trigger

Set the roam trigger RSSI threshold. (integer)

[edit]rssi

Get the current RSSI (signal strength) value.

In AP mode, you must specify the mac address of the wireless card who's signal signal you wish to monitor. You can use wl assoclist to get the client mac list.

In client mode there is no need to specify the MAC address of the AP as it will just use the AP that you are associated with.

See also: Signal Strength on the Script Examples page for a one line script to display a bar graph of the current signal level.

[edit]rssidump

Dump rssi values from aci scans

[edit]rts

Set the RTS threshhold. (integer [0, 2347])

[edit]scan_channel_time

Get/Set scan channel time

[edit]scan_home_time

Get/Set scan home channel dwell time

[edit]scan_nprobes

Get/Set scan parameter for number of probes to use per channel scanned

[edit]scan_passive_time

Get/Set passive scan channel dwell time

[edit]scan_unassoc_time

Get/Set unassociated scan channel dwell time

[edit]scanresults

Return results from last scan.

[edit]scansuppress

Suppress all scans for testing.

[edit]scb_timeout

AP only: inactivity timeout value for authenticated stas

[edit]scbdump

print driver scb state to stdout

[edit]scan

Initiate a scan.

NOTE: 'wl scan' does not work in AP Mode. To scan please use:

[edit]set_pmk

Set passphrase for PMK in driver-resident supplicant.

[edit]shmem

Get/Set a shared memory location.

[edit]shortslot

Get/Set 11g Short Slot Timing mode. (-1=auto, 0=long, 1=short)

[edit]shortslot_override

Get/Set 11g Short Slot Timing mode override. (-1=auto, 0=long, 1=short)

[edit]shortslot_restrict

Get/Set AP Restriction on associations for 11g Short Slot Timing capable STAs.

[edit]slowtimer

Get/Set Low frequency watchdog timeout (nrssislope) [60 sec]

[edit]spect

Get/Set 802.11h Spectrum Management mode.

[edit]srdump

print contents of SPROM to stdout(Functions neither in AP, nor in Client mode for output - really??)

[edit]srl

srl Set the short retry limit. (integer [1, 255])

[edit]ssid

Set or get the current SSID.

[edit]sta_info

wl sta_info <xx:xx:xx:xx:xx:xx>

[edit]status

Print information about current network association. (also known as 'assoc')

[edit]suprates

Free Slots G

Returns or sets the 11g override for the supported rateset.

[edit]tkip

Set TKIP options.

[edit]tkip_countermeasures

Enable or disable TKIP countermeasures (TKIP-enabled AP only)

[edit]tsc

Print Tx Sequence Couter for key at specified key index.

[edit]tssi

Get the tssi value from radio

[edit]txant

Set the transmit antenna

Note: can be used in conjunction with 'wl antdiv' to set the receive antenna

[edit]txpathpwr

Turn the tx path power on or off on 2050 radios

[edit]txpwr

Set transmit power in milliwatts. Range [1, 84]. (Deprecated: Use txpwr1 instead)

This can be set to a value above 84, but it may damage your hardware especially over prolonged use -- use with caution.

[edit]txpwr1

Set tx power in in various units. Choose one of (default: dbm):

Can be combined with:

[edit]txpwrlimit

Return current tx power limit

[edit]ucflags

Get/Set ucode flags

[edit]upgrade

Upgrade the firmware on an embedded device

[edit]ver

Version information

[edit]wake

set driver power-save mode sleep state:

[edit]wds

Set or get the list of WDS member MAC addresses.

[edit]wds_remote_mac

Get WDS link remote endpoint's MAC address

[edit]wds_wpa_role

Get/Set WDS link local endpoint's WPA role

[edit]wds_wpa_role_old

Get WDS link local endpoint's WPA role (old)

[edit]wep

Set WEP options.

[edit]wepstatus

Set or Get WEP status

[edit]wet

Get/Set wireless ethernet bridging mode

[edit]wsec

Wireless security bit vector

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[edit]wsec_test

Generate wsec errors

[edit]wme

Set WME (Wireless Multimedia Extensions) mode (0=off, 1=on)

[edit]wsec_restrict

Drop unencrypted packets if WSEC is enabled

[edit]wpa_auth

WPA authorization mode

[edit]External links

• [1] broadcom-wl-drv (auf Englisch)
• [2] broadcom-wl package(auf Englisch)