U.S. patent application number 14/558419 was filed with the patent office on 2015-03-26 for method of limiting transmission rate.
This patent application is currently assigned to LG ELECTRONICS INC.. The applicant listed for this patent is LG ELECTRONICS INC.. Invention is credited to Yong Ho SEOK.
Application Number | 20150085652 14/558419 |
Document ID | / |
Family ID | 42665711 |
Filed Date | 2015-03-26 |
United States Patent
Application |
20150085652 |
Kind Code |
A1 |
SEOK; Yong Ho |
March 26, 2015 |
METHOD OF LIMITING TRANSMISSION RATE
Abstract
A method for limiting a transmission rate is provided. The
method includes receiving a pause management message comprising
pause scheduling information including a pause time at which an
uplink transmission of a data frame is to be paused and a paused
duration indicating a duration during which transmission of the
data frame is to be paused, and pause station information
indicating a station which is to pause transmission the data frame,
from an access point (AP); and pausing transmission of the data
frame during the paused duration starting from the pause time
according to the pause management message, and then resuming
transmission. According to exemplary embodiments of the present
invention, a transmission rate limiting mechanism suitable for a
VHT WLAN can be provided.
Inventors: |
SEOK; Yong Ho; (Anyang-si,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG ELECTRONICS INC. |
Seoul |
|
KR |
|
|
Assignee: |
LG ELECTRONICS INC.
Seoul
KR
|
Family ID: |
42665711 |
Appl. No.: |
14/558419 |
Filed: |
December 2, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13202972 |
Aug 23, 2011 |
8929219 |
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PCT/KR2009/004415 |
Aug 7, 2009 |
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14558419 |
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61154770 |
Feb 24, 2009 |
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Current U.S.
Class: |
370/230 |
Current CPC
Class: |
H04L 47/24 20130101;
H04L 47/14 20130101; H04L 47/10 20130101; H04L 47/13 20130101; H04W
28/12 20130101; H04W 28/0215 20130101; H04L 47/11 20130101; H04W
28/0205 20130101; H04W 28/0247 20130101; H04L 47/266 20130101; H04L
47/2483 20130101; H04W 84/12 20130101 |
Class at
Publication: |
370/230 |
International
Class: |
H04W 28/02 20060101
H04W028/02; H04L 12/851 20060101 H04L012/851; H04L 12/801 20060101
H04L012/801 |
Claims
1. A method for performing flow control in a wireless local area
network (LAN), the method comprising: receiving, by a wireless
station, a control signal comprising pause duration information and
station information, the pause duration information indicating a
duration during which transmission of at least one data frame
having a traffic identifier (TID) is to be paused, the station
information comprising an individual address or broadcast address
associated with the wireless station; pausing, by the wireless
station, the transmission of the at least one data frame during the
duration indicated by the pause duration information without
pausing transmission of a control frame; and resuming, by the
wireless station, the transmission of the at least one data frame
on expiration of the paused duration.
2. The method of claim 1, wherein the pause duration information
indicates amount of time in microseconds.
3. The method of claim 1, wherein the control signal comprises a
pause management action frame comprising a category field, followed
by an action field, followed by the pause duration information.
4. A wireless station for performing flow control in a wireless
local area network (LAN), comprising: a radio frequency (RF) unit
configured to transmit and receive signals; and a processor coupled
to the RF unit and configured to: receive a control signal
comprising pause duration information and station information, the
pause duration information indicating a duration during which
transmission of at least one data frame having a traffic identifier
(TID) is to be paused, the station information comprising an
individual address or broadcast address associated with the
wireless station; pause the transmission of the at least one data
frame during the duration indicated by the pause duration
information without pausing transmission of a control frame; and
resume the transmission of the at least one data frame on
expiration of the paused duration.
5. The wireless station of claim 4, wherein the pause duration
information indicates amount of time in microseconds.
6. The wireless station of claim 4, wherein the control signal
comprises a pause management action frame comprising a category
field, followed by an action field, followed by the pause duration
information.
Description
TECHNICAL FIELD
[0001] The present invention relates to a wireless local access
network (WLAN) and, more particularly, to a method of limiting a
transmission rate in a very high throughput (VHT) WLAN.
BACKGROUND ART
[0002] Recently, diverse wireless communication technologies are
under development in line with the advancement of information
communication technology. Among them, a wireless local area network
(WLAN) is a technique allowing mobile terminals such as personal
digital assistants (PDAs), lap top computers, portable multimedia
players (PMPs), and the like, to wirelessly access the Internet at
homes, offices or in a particular service providing area based on a
radio frequency technology.
[0003] Since IEEE (Institute of Electrical and Electronics
Engineers) 802, a standardization organization of a WLAN technique,
was established in February 1980, a great deal of standardization
works have been conducted.
[0004] The early WLAN technique supported the rate of 1.about.2
Mbps through frequency hopping, spread spectrum, infrared
communications, and the like, by using a 2.4 GHz frequency based on
IEEE 802.11, and recently a maximum rate of 54 Mbps can be
supported by applying orthogonal frequency division multiplex
(OFDM) technology to the WLAN. Further, IEEE 802.11 are putting
standards of various techniques, such as improvement of quality of
service (QoS), allowing compatibility of access point (AP)
protocols, achievement of security enhancement, measurement radio
resource measurement, wireless access vehicular environment,
ensuring fast roaming, establishing a mesh network, interworking
with an external network, wireless network management, and the
like, into practical use or are still developing them.
[0005] Among the IEEE 802.11, IEEE 802.11b supports a maximum of 11
Mbs communication speed while using the frequency band of 2.4 GHz.
IEEE 802.11a which has been commercialized following the IEEE
802.11b uses the frequency band of 5 GHz, not 2.4 GHz, to reduce
the influence of an interference compared with the considerably
congested frequency band of 2.4 GHz and has a communication speed
increased up to a maximum 54 Mbps by using the OFDM technique.
However, IEEE 802.11a has shortcomings in that its communication
distance is shorter than that of IEEE 802.11b. Meanwhile, IEEE
802.11g uses the frequency band of 2.4 GHz, like IEEE 802.11b, to
implement a communication speed of a maximum 54 Mbps and satisfies
backward compatibility, and as such, IEEE 802.11g receives much
attention. Also, IEEE 802.11b is superior to IEEE 802.11a, in the
aspect of the communication distance.
[0006] IEEE 802.11n has been lately stipulated as a technique
standard to overcome the limitation in the communication speed
which has been admitted as a weak spot of the WLAN. IEEE 802.11n
aims to increase the speed and reliability of a network and extend
an operation distance of a wireless network.
[0007] In more detail, IEEE 802.11n supports a high throughput (HT)
of more than a maximum 540 Mbps as a data processing speed, and is
based on a multiple input and multiple output (MIMO) technique
using multiple antennas at both ends of a transmission unit and a
reception unit to minimize a transmission error and maximize a data
rate.
[0008] Also, IEEE 802.11n standard may use orthogonal frequency
division multiplex (OFDM) to increase the speed as well as using a
coding scheme that transmits several duplicates to enhance data
reliability.
[0009] As the WLAN is widely spreading and applications using WLAN
are diversified, recently, the necessity for a new WLAN system
emerges to support a higher throughput than the data processing
speed supported by IEEE 802.11n. A very high throughput (VHT) WLAN
system is one of the newly proposed IEEE 802.11 WLAN systems in
order to support a data processing speed of 10 Gbps or faster. The
term of VHT WLAN system is arbitrary, and currently, a feasibility
test is performed on a 4.times.4 MIMO and a system using a channel
bandwidth of 80 MHz or higher to provide throughput of 1 Gbps or
faster.
[0010] The key application of IEEE 802.11 VHT is HD video streaming
To enhance the quality of service of HD video streaming, a rate
limiting mechanism is used.
[0011] Rate limiting is used to control the rate of traffic sent or
received on a network interface. Traffic that is less than or equal
to the specified rate is sent, whereas traffic that exceeds the
rate is dropped or delayed. A device that performs rate limiting is
a rate limiter.
[0012] Rate limiting has been performed by policing (discarding
excess packets), queuing (delaying packets in transit) or
congestion control (manipulating the protocol's congestion
mechanism).
[0013] For rate limiting in a wired network, Ethernet is utilizing
PAUSE frame. PAUSE is a flow control mechanism on full duplex
Ethernet link segments defined by IEEE 802.3x and uses MAC Control
frames to carry the PAUSE commands. The MAC Control opcode for
PAUSE is 0X0001 (hexadecimal). Only stations configured for
full-duplex operation may send PAUSE frames.
[0014] When a station wishes to send a PAUSE command, it sends the
MAC Control frame to the 48-bit destination multicast MAC address
of 01-80C2-00-00-01. This particular address has been reserved for
use in PAUSE frames.
[0015] A PAUSE frame includes the period of pause time being
requested, in the form of two byte unsigned integer (0 through
65535). This number is the requested duration of the pause. The
pause time is measured in units of pause "quanta", where each unit
is equal to 512 bit times.
[0016] In IEEE 802.11h, An AP in a BSS may schedule quiet intervals
by transmitting one or more Quiet elements in Beacon frames and
Probe Response frames. Quiet element has the Quiet Period field,
the Quiet Duration field, and the Quiet Offset field. However, an
effective method that may control a transmission rate without
pausing all the transmissions is required.
DISCLOSURE
Technical Problem
[0017] Therefore, an object of the present invention is to provide
a transmission rate limiting mechanism suitable for a very high
throughput (VHT) wireless LAN (WLAN). An overload can be prevented
and radio resources can be effectively used by limiting a
transmission rate.
Technical Solution
[0018] According to an aspect of the present invention, a method
for limiting a transmission rate is provided. The method includes
receiving a pause management message comprising pause scheduling
information including a pause time at which an uplink transmission
of a data frame is to be paused and a paused duration indicating a
duration during which transmission of the data frame is to be
paused, and pause station information indicating a station which is
to pause transmission the data frame, from an access point (AP);
and pausing transmission of the data frame during the paused
duration starting from the pause time according to the pause
management message, and then resuming transmission. According to
exemplary embodiments of the present invention, a transmission rate
limiting mechanism suitable for a VHT WLAN can be provided.
[0019] And according to another aspect of the present invention, a
method for limiting a transmission rate in a wireless LAN system is
provided. The method includes detecting, by an access point (AP),
an overload generated in receiving a data frame from a station; and
transmitting a pause management message for pausing uplink
transmission of the data frame to the station; wherein the pause
management message comprises pause scheduling information
comprising a pause time at which transmission of the data frame is
paused and a paused duration indicating a duration during which
transmission of the data frame is paused, and pause station
information indicating a station that transmits the data frame.
Advantageous Effects
[0020] According to exemplary embodiments of the present invention,
a transmission rate limiting mechanism suitable for a VHT WLAN can
be provided. In addition, an overload that has been already
generated or that may be generated at traffic can be prevented
without having to completely pause transmission.
[0021] Also, a channel state and the characteristics of a data
frame can be reflected for a pause scheduling. Thus, a transmission
rate can be controlled according to the characteristics of a data
frame to thereby effectively utilize radio resources.
DESCRIPTION OF DRAWINGS
[0022] FIG. 1 illustrates the configuration of a very high
throughput (VHT) WLAN that can employ an embodiment of the present
invention.
[0023] FIG. 2 illustrates a quiet element used to limit a
transmission rate according to the related art.
[0024] FIG. 3 is a flow chart illustrating a method for limiting a
transmission rate according to an exemplary embodiment of the
present invention.
[0025] FIG. 4 illustrates the method for limiting a transmission
rate according to an exemplary embodiment of the present
invention.
[0026] FIG. 5 illustrates a format of a pause management message
transmitted according to an exemplary embodiment of the present
invention.
MODE FOR INVENTION
[0027] FIG. 1 illustrates the configuration of a very high
throughput (VHT) WLAN that can employ an embodiment of the present
invention.
[0028] With reference to FIG. 1, a WLAN system such as the VHT WLAN
system includes one or more of basic service sets (BSSs). A BSS
refers to a set of stations (STAs) that can communicate with each
other in synchronization, not a concept indicating a particular
area. Like the WLAN system to which the exemplary embodiments of
the present invention are applicable, a BSS that supports the data
processing at a high speed of 1 GHz or faster at a MAC SAP (service
access point) is called a VHT BSS.
[0029] The VHT BSS may be divided into an infrastructure BSS and an
independent BSS (IBSS). FIG. 1 illustrates the infrastructure
BSS.
[0030] The infrastructure BSS (BSS1 and BSS2) includes one or more
of non-AP STA1, non-AP STA3, and non-AP STA4, access points (APs)
(AP STA1 and AP STA2), stations providing a distribution service,
and a distribution system (DS) connecting the plurality of APs (AP
STA1 and AP STA2). In the infrastructure BSS, the AP stations
manage the NON-AP stations of the BSSs.
[0031] Meanwhile, the IBSS is a BSS operating in an ad-hoc mode.
Because the IBSS does not include an AP VHT STA, it does not have a
centralized management entity. Namely, in the IBSS, non-AP stations
are managed in a distributed manner. In the IBSS, every station may
be a mobile station, and the IBSS establishes a self-contained
network, not allowing an access to a distribution system (DS).
[0032] A station is an arbitrary function medium including a medium
access control (MAC) following the stipulation of IEEE 802.11
standard and a physical layer interface with respect to a wireless
medium, and includes both AP and non-AP stations in a broad sense.
A station supporting high speed data processing of 1 GHz or faster
in a multi-channel environment (to be described) is called a VHT
station. In the VHT WLAN system to which the exemplary embodiments
of the present invention are applicable, stations included in the
BSS may be all VHT stations, or in the BSS, VHT stations and legacy
stations (e.g., an HT STA following IEEE 802.11n) may coexist.
[0033] A station for radio communications includes a processor, a
transceiver, a user interface, and a display unit. The processor is
a function unit devised to generate a frame to be transmitted via a
wireless network or a frame received via the wireless network,
performing various functions to control the station. The
transceiver, which is functionally connected with the processor, is
devised to transmit and receive frames via the wireless network for
the station.
[0034] Among stations STAs, a mobile terminal manipulated by a user
is a non-AP STA (STA1, STA3, STA4, STA6, STA7, and STA8), and
simply referring to a station may indicate a non-AP STA. The non-AP
STA may be referred to by other names such as terminal, wireless
transmit/receive unit (WTRU), user equipment (UE), mobile station
(MS), mobile terminal, mobile subscriber unit, or the like. A
non-AP STA supporting high speed data processing at 1 GHz or faster
in a multi-channel environment (to be described) is called a non-AP
VHT STA or simply a VHT STA.
[0035] The APs (AP1 and AP2) are functional entities for providing
an access to the DS by way of a wireless medium for an STA
associated thereto. In the infrastructure BSS including the APs, in
principle, communications between non-AP STAs are made by way of
the APs, but when a direct link has been established, the non-AP
STAs can directly communicate with each other. The AP may be also
called by other names such as centralized controller, base station
(BS), node-B, base transceiver system (BTS), site controller, and
the like, than the AP. In the multi-channel environment (to be
described), an AP supporting high speed data processing at 1 GHz or
faster is called a VHT AP.
[0036] A plurality of infrastructure BSSs may be connected via the
DS. The plurality of BSSs connected via the DS is called an
extended service set (ESS). STAs included in the ESS may
communicate with each other, and the non-AP STA may move from one
BSS to another BSS within the same ESS while seamlessly performing
communication.
[0037] The DS is a mechanism allowing one AP to communicate with
another AP. Through the DS, an AP may transmit a frame for STAs
associated to the BSS managed by the AP, transfer a frame when one
STA moves to another BSS, or transmit or receive frames to and from
an external network such as a wireline network. The DS is not
necessarily a network. Namely, the DS is not limited to any form so
long as it can provide a certain distribution service defined in
IEEE 802.11 standard. For example, the DS may be a wireless network
such as a mesh network or a physical structure connecting the
APs.
[0038] FIG. 2 illustrates a quiet element used to limit a
transmission rate according to the related art.
[0039] In the BSS, the AP may schedule a quiet interval. The quiet
interval may be scheduled by the AP by including one or more quiet
elements in a beacon frame and a probe response frame and
transmitting the same.
[0040] The quiet element may include an element ID field, a length
field, a quiet count field, a quiet period field, a quiet duration
field, a quiet offset field, and the like.
[0041] The element ID field is set as a certain value indicating a
quite element. The length field may be set as a value indicating
the entire length of subsequent fields by octet.
[0042] The quite count field may be set as a value indicating the
number of target beacon transmission time (TBTT) until a beacon
interval at which a next quiet interval starts. If the quiet count
field is set as 1, it may indicate that the quite interval starts
during a beacon interval starting from a next TBTT. The TBTT starts
as a beacon frame is transmitted, and a duration until when a next
beacon frame is transmitted corresponds to the TBTT.
[0043] The quiet period field may be set as a value indicating the
number of beacon intervals between starts of regularly scheduled
quiet intervals defined by the quiet element. If the quiet period
field is set as 0, it indicates that a periodical quiet interval is
not defined.
[0044] The quiet duration field may be set as a value indicating a
duration of the quiet interval, and the quiet offset field may be
set as a value indicating an offset between a start time of the
quiet interval and a TBTT specified by the quiet count field. The
value set in the quiet count field is smaller than the beacon
interval.
[0045] When the quiet element is in use, a transmission or a
transmission rate is controlled in an on/off manner. Namely,
transmission is temporarily stopped over every channel during the
quiet interval irrespective of a data type of each transmitted data
or priority of each transmission. Thus, an effective method that
can control a transmission rate without pausing every transmission
is required.
[0046] FIG. 3 is a flow chart illustrating a method for limiting a
transmission rate according to an exemplary embodiment of the
present invention.
[0047] In the exemplary embodiment described with reference to FIG.
3, it is assumed that as a station transmits uplink data to an AP,
the AP, which receives the uplink data, is overloaded.
[0048] First, the station transmits uplink data to the AP (S310).
The station that transmits the uplink data to the AP may be called
a transmission station. In this case, if the station transmits an
excessive amount of data without consideration of a buffer capacity
of the AP, or if a transmission rate of the uplink data is too
large for the buffer capacity of the AP, the AP is overloaded
(S320).
[0049] Then, the AP transmits a pause management message to the
transmission station (S330). The pause management message may have
a format of a pause management action frame. The pause management
action frame will be described later.
[0050] The pause management message includes information for
scheduling pause of a data frame transmission of the station. The
pause scheduling information may be information about a paused
duration indicating how long transmission of a data frame is to be
paused, and in case where transmissions and pauses are repeatedly
performed, the pause scheduling information may be information
about a period of such repetition and an interval of the
repetition.
[0051] If the pause management message is transmitted to a
plurality of stations, the pause management message may include
information indicating a target station of the pause management
message. A station subjected to the transmission pause or a
transmission rate control may be called a pause station, and
information indicating which station is a pause station may be
called pause station information.
[0052] If the degree of pause or transmission rate control is
changed according to an access category of a data frame, the pause
management message may include information about an access
category. In this case, the pause scheduling information has a
value varied according to the access category information.
[0053] When the transmission station receives the pause management
message, it temporarily stops transmission or lowers a transmission
rate through a method of repeatedly performing transmission of a
data frame and pausing transmission and the like (S340). The
transmission station may determine how long a data transmission is
to be paused, in which pattern the data transmission and
transmission pause are to be repeated, how low the transmission
rate is to be dropped, and the like, according to the information
included in the pause management message. As a format of the pause
management message, the format of a pause management action frame
of IEEE 802.11 can be used.
[0054] Namely, if the transmission station transmits an excessive
amount of a data frame for the buffer of a reception station, the
AP may provide control to transmit the pause management message to
the transmission station to reduce a transmission rate to the
AP.
[0055] The AP may transmit the pause management message by using a
directional antenna or an omnidirectional antenna. In particular,
the AP may transmit the pause management message in an
omnidirectional mode or in a broadcast manner. This may bring about
a situation in which a plurality of stations receive the pause
management message transmitted by the AP. Upon receiving the pause
management message, the stations determine whether to pause
transmission of a data frame or whether to limit a transmission
rate according to the pause station information among information
included in the pause management message.
[0056] Or, upon receiving the pause management message, the
stations may check which station or which channel traffic whose
transmission rate is to be controlled by the AP corresponds to
through the pause management message. Namely, the pause management
message may include identification information of traffic targeted
for limitation of the transmission rate. Accordingly, the stations
reduce the transmission amount of the data frame or temporarily
stop transmission of the data frame of a type designated by the
pause management message. In this case, information about a
duration of transmission pause during which transmission of the
data frame is temporarily stopped may be set to be different for
each station or each traffic. Namely, when the station, which has
been transmitting a data frame, receives the pause management
message, it temporarily stops transmission of the data frame during
the designated duration or limits the transmission rate at a
designated point of time according to the information included in
the received pause management message. In addition, in case where
the station repeats transmitting of the data frame to the AP and
pausing the transmissions one or more times within a single TBTT,
it may repeat transmitting and pausing according to paused interval
information.
[0057] Meanwhile, priority may be given according to the access
categories of data frames. That is, limitation of the transmission
rate or pausing of transmission may be differently performed
according to priority. This will be described in detail later with
reference to FIG. 4.
[0058] FIG. 4 illustrates the method for limiting a transmission
rate according to an exemplary embodiment of the present invention.
The method for limiting a transmission rate according to each data
type will now be described.
[0059] The data frames uplink-transmitted to the AP by the station
may be classified into four types of access categories according to
their traffic characteristics. In addition, priority may be
differently set for these access categories. The four access
categories include AC_VO (Access Category_Voice), AC_VI (Access
Category_Video), AC_BE (Access Category_Best Effort), and AC_BK
(Access Category.sub.-- Background).
[0060] In FIGS. 4, (a), (b), (c), and (d) show channels for
transmitting frames according to the access categories of data
based on a time axis, respectively. Specifically, (a) shows a
transmission channel of a voice data frame with an access category
of AC_VO (Access Category_Voice), (b) shows a transmission channel
of a video data frame with an access category of AC_VI (Access
Category_Video), (c) shows a best-effort data frame with an access
category of AC_BE (Acess Category_Best Effort), and (d) shows a
transmission channel of a background data frame with an access
category of AC_BK (Access Category_Background).
[0061] The AP sets a paused period and a contention period
according to each access category. As the contention period becomes
long and as the paused period becomes short, the probability of
acquiring a channel access opportunity or a transmission
opportunity for transmitting a data frame of a corresponding access
category increases, and resultantly, the corresponding access
category has a high priority level.
[0062] The contention period refers to a duration during which
transmission of a data frame is permitted, and the paused period
refers to a duration during which transmission of the data frame is
temporarily stopped. With reference to FIG. 4, it is noted that the
contention period and the paused period are differently controlled
by channel depending on the action categories of data frames
according to the pause management message or the pause management
action frame transmitted by the AP.
[0063] After a beacon frame 400 is transmitted, transmission of a
data frame and pausing transmission may repeat until when a next
beacon frame 405 is transmitted. When the pause management access
frame is received, the station sets a network allocation vector
(NAV) and freezes (i.e., temporarily stops) a current backoff timer
corresponding to a paused TID (Traffic Identifier), thereby
preventing accessing a wireless medium during the paused
period.
[0064] Meanwhile, channel accessing is allowed during a non-paused
period, namely, during the contention period. During the contention
period, the station may reset the NAV and release the freezing of
the backoff timer, to allow accessing a wireless medium.
[0065] In case of the AC_VO in (a), the contention period 410
continues without a paused period. Namely, according to an
exemplary embodiment illustrated in FIG. 4, a voice data frame, a
data frame with the highest priority level, is transmitted without
a pause, resulting in that it most preferentially obtains the
transmission opportunity.
[0066] In case of transmission of a video data frame (i.e., the
data frame with an access category of AC_VI) in (b), the contention
period 410 is short while the paused period 420 is also short. If
transmission of the video data frame is not successfully
transmitted during the first contention period 410, it can be
transmitted during another contention period 410 following the
short paused period 420. Because the contention periods 410 are
repeated, the data frame with the access category of AC_VI can
obtain a relatively frequent transmission opportunity.
[0067] Compared with the data frames with the access categories
AC_VO and AC_VI, the data frames AC_BE and AC_BK with the
relatively low priority levels have the paused period 420 longer
than the contention period 410. The interval between the contention
periods 410 corresponds to the paused period 420. In this case, the
periods during which channel accessing a wireless medium (i.e.
contention period) is allowed is repeated but the interval (i.e.
paused period) is long, so these data frames cannot frequently
obtain the transmission opportunity. Resultantly, the data frames
AC_BE and AC_BK have a lower priority level in the uplink
transmission.
[0068] That is, as described above, the AP may transmit the pause
management access frame to a station by differing the information
such as the paused duration varied according to access categories.
The priority levels of the access categories may be given depending
on the paused period, the paused duration, the paused interval, a
duration of the contention period, or an interval of the contention
period according to these values (i.e., the value of the paused
period, the paused duration, the paused interval).
[0069] FIG. 5 illustrates a format of the pause management message
transmitted according to an exemplary embodiment of the present
invention.
[0070] The pause management message as transmitted according to the
exemplary embodiments described above with reference to FIGS. 3 and
4 may follow the format of the pause management action frame, and
FIG. 5 illustrates the format of the pause management action frame.
In FIG. 5, the order of the fields is shown, but the present
invention is not limited thereto and the scope of the present
invention is not limited by the order of the fields.
[0071] The pause management action frame includes a category field
510, an action field 520, a paused STA address field 530, a paused
TID (Traffic Identifier) field 540, a paused offset field 550, a
paused interval field 560, a paused duration field 570, a paused
channel set field 580, and the like.
[0072] The AP may transmit the pause management action frame to
each station. If a buffer is overloaded due to uplink transmission
of the stations, the AP transmits the pause management action frame
to the corresponding station which has uplink-transmitted an
excessive amount of data.
[0073] Information for controlling a transmission rate or
transmission pause may be included, particularly, in the paused STA
Address field 530, the paused TID field 540, the paused offset
field 550, the paused interval field 560, and the paused duration
field 570, in the pause management action frame.
[0074] The pause management action frame may include pause station
information. For example, an address of a station targeted for
pausing transmission by the AP may be included as a paused station
address in the paused STA Address field 530 of the pause management
action frame.
[0075] Here, the paused station address may be a unicast address or
a group address. If a transmission rate of a data frame according
to transmission in a multicast manner is excessive, the AP may
designate a group address to limit corresponding traffic.
[0076] Also, the paused STA Address may be a MAC (Media Access
Control) address of a corresponding transmission station. Namely,
the paused station address of the paused STA Address field 530 may
be set as a MAC address of a receiver whose data frame reception is
to be paused or limited by the pause management action frame.
[0077] The paused TID of the paused TID field 540 is set as a TID
of paused traffic. Namely, the AP may designate overloaded traffic
to thus control transmission pause.
[0078] The pause management action frame includes pause scheduling
information regarding pause of transmission from the station to the
AP and resuming of transmission. The pause scheduling information
indicate when data frame transmission is paused, how long the data
frame transmission is paused, when the data frame transmission is
resumed, what kind of repetition period of pausing and resuming,
and the like. The pause scheduling information is included in the
fields such as the paused offset field 550, the paused interval
field 560, and the paused duration field 570.
[0079] The paused offset in the paused offset field 550 refers to a
time duration starting from the TBTT (Target Beacon Transmission
Time) to a point of time from which a pause time starts. For
example, if the paused offset is 10?s, the pause time starts in
10?s after (i.e., from a point of time when) a next beacon frame is
received (or after a next TBTT starts).
[0080] The paused interval field 560 includes information
indicating a temporal interval between pause times. The paused
interval is set as an interval between consecutive paused
times.
[0081] The paused duration field 570 includes information about a
paused duration which is set as the length of the paused time.
[0082] The station postpones channel accessing for paused traffic
as long as the paused duration by freezing the current backoff
timer for the paused TID.
[0083] As afore-mentioned, the pause scheduling information may be
set to be different according to an access category of a data frame
to be transmitted. Namely, because the paused interval, the paused
duration, etc., are differently set according to the priority level
of the access categories of the data frames, the transmission
amount can be more effectively controlled for user convenience.
[0084] The paused channel set field 580 is set as the number of a
channel subjected to a transmission pause or a limitation of the
transmission rate.
[0085] If the field value of the paused set field 580 is set as a
value not 0, the station may postpone channel accessing to a
particular sub-channel of 20 MHz. If the field value of the paused
channel set field 580 is set as 0, the station postpones channel
accessing to every channel.
[0086] This is because the VHT BSS uses a broadband channel of 80
MHz, and the AP can specify a paused channel set. Here, the paused
channel refers to a sub-channel of 20 MHz.
[0087] The method described so far may be implemented by
microprocessors, controllers, microcontrollers, application
specific integrated circuits (ASICs), and the like, according to
software or program codes coded to perform the methods. Designing,
developing, and implementing of the codes may be obvious to the
skilled person in the art based on the description of the present
invention.
[0088] The preferred embodiments of the present invention have been
described with reference to the accompanying drawings, and it will
be apparent to those skilled in the art that various modifications
and variations can be made in the present invention without
departing from the scope of the invention. Thus, it is intended
that any future modifications of the embodiments of the present
invention will come within the scope of the appended claims and
their equivalents.
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