U.S. patent application number 17/200773 was filed with the patent office on 2021-07-01 for method for sending/receiving data in a wireless packet communication system in which there is simultaneous communication with various terminals.
This patent application is currently assigned to Electronics and Telecommunications Research Institute. The applicant listed for this patent is Electronics and Telecommunications Research Institute. Invention is credited to Jeeyon CHOI, Sok-Kyu LEE.
Application Number | 20210203518 17/200773 |
Document ID | / |
Family ID | 1000005451011 |
Filed Date | 2021-07-01 |
United States Patent
Application |
20210203518 |
Kind Code |
A1 |
CHOI; Jeeyon ; et
al. |
July 1, 2021 |
METHOD FOR SENDING/RECEIVING DATA IN A WIRELESS PACKET
COMMUNICATION SYSTEM IN WHICH THERE IS SIMULTANEOUS COMMUNICATION
WITH VARIOUS TERMINALS
Abstract
A method and apparatus for transmitting a frame to at least one
receiver in a wireless communication system is provided. The
apparatus determines at least one data length in accordance with
each receiver based on a number of symbol for the frame to be
transmitted, determines a maximum data length among the at least
one data length, and determines a length of the frame in time
domain based on the maximum data length. The apparatus generates
the frame in accordance with the length of the frame, the frame
including a first signal field and at least one second signal
field. The first signal field indicates the length of the frame and
each second signal field indicates each data length.
Inventors: |
CHOI; Jeeyon; (Daejeon,
KR) ; LEE; Sok-Kyu; (Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Electronics and Telecommunications Research Institute |
Daejeon |
|
KR |
|
|
Assignee: |
Electronics and Telecommunications
Research Institute
Daejeon
KR
|
Family ID: |
1000005451011 |
Appl. No.: |
17/200773 |
Filed: |
March 13, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16383613 |
Apr 14, 2019 |
10958455 |
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17200773 |
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15067178 |
Mar 11, 2016 |
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16383613 |
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13525220 |
Jun 15, 2012 |
9288017 |
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15067178 |
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PCT/KR2010/009039 |
Dec 16, 2010 |
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13525220 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 12/18 20130101;
H04L 5/0055 20130101; H04W 88/08 20130101; H04B 7/0452 20130101;
H04L 1/0083 20130101; H04W 84/12 20130101; H04L 1/1887 20130101;
H04L 2001/0093 20130101; H04B 5/00 20130101 |
International
Class: |
H04L 12/18 20060101
H04L012/18; H04L 1/00 20060101 H04L001/00; H04L 1/18 20060101
H04L001/18; H04B 5/00 20060101 H04B005/00; H04B 7/0452 20060101
H04B007/0452; H04L 5/00 20060101 H04L005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 18, 2009 |
KR |
10-2009-0127310 |
Feb 4, 2010 |
KR |
10-2010-0010590 |
Jul 9, 2010 |
KR |
10-2010-0066465 |
Claims
1. A communicating method comprising: receiving a Physical layer
Protocol Data Unit (PPDU) from a station, the PPDU comprising a
first training field, a first signal field, a second signal field,
a second training field, a third signal field and a data field,
wherein: the data field comprises service bits, an Aggregated MAC
Protocol Data Unit (A-MPDU), pad bits and tail bits; the first
signal field comprises information related to a length of the PPDU;
and the third signal field comprises information related to a
length of the A-MPDU.
2. The method of claim 1, wherein the first training field precedes
the first signal field, the first signal field precedes the second
signal field, the second signal field precedes the second training
field, the second training field precedes the third signal field,
and the third signal field precedes the data field.
3. The method of claim 2, wherein the service bits comprise
information related to scrambling.
4. The method of claim 3, wherein the first signal field is a
legacy signal (L-SIG) field and the third signal field is a SIG B
field.
5. The method of claim 4, further comprising transmitting an
acknowledgement to the station based on the information related to
the length of the PPDU.
6. The method of claim 4, further comprising processing the A-MPDU
based on the information related to the length of the A-MPDU.
7. A communication apparatus comprising: a circuitry, wherein the
circuitry is configured to cause the communication apparatus to
receive a Physical layer Protocol Data Unit (PPDU) from a station,
the PPDU comprising a first training field, a first signal field, a
second signal field, a second training field, a third signal field
and a data field, wherein: the data field comprises service bits,
an Aggregated MAC Protocol Data Unit (A-MPDU), pad bits and tail
bits; the first signal field comprises information related to a
length of the PPDU; and the third signal field comprises
information related to a length of the A-MPDU.
8. The communication apparatus of claim 7, wherein the first
training field precedes the first signal field, the first signal
field precedes the second signal field, the second signal field
precedes the second training field, the second training field
precedes the third signal field, and the third signal field
precedes the data field.
9. The communication apparatus of claim 8, wherein the service bits
comprise information related to scrambling.
10. The communication apparatus of claim 9, wherein the first
signal field is a legacy signal (L-SIG) field and the third signal
field is a SIG B field.
11. The communication apparatus of claim 10, wherein the circuitry
is further configured to cause the communication apparatus to
transmit an acknowledgement to the station based on the information
related to the length of the PPDU.
12. The communication apparatus of claim 10, wherein the circuitry
is further configured to cause the communication apparatus to
process the A-MPDU based on the information related to the length
of the A-MPDU.
13. A device for a station comprising: a circuitry, wherein the
circuitry is configured to cause the station to receive a Physical
layer Protocol Data Unit (PPDU) from another station, the PPDU
comprising a first training field, a first signal field, a second
signal field, a second training field, a third signal field and a
data field, wherein: the data field comprises service bits, an
Aggregated MAC Protocol Data Unit (A-MPDU), pad bits and tail bits;
the first signal field comprises information related to a length of
the PPDU; and the third signal field comprises information related
to a length of the A-MPDU.
14. The device of claim 13, wherein the first training field
precedes the first signal field, the first signal field precedes
the second signal field, the second signal field precedes the
second training field, the second training field precedes the third
signal field, and the third signal field precedes the data
field.
15. The device of claim 14, wherein the service bits comprise
information related to scrambling.
16. The device of claim 15, wherein the first signal field is a
legacy signal (L-SIG) field and the third signal field is a SIG B
field.
17. The device of claim 16, wherein the circuitry is further
configured to cause the station to transmit an acknowledgement to
the another station based on the information related to the length
of the PPDU.
18. The device of claim 16, wherein the circuitry is further
configured to cause the station to process the A-MPDU based on the
information related to the length of the A-MPDU.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/383,613, filed Apr. 14, 2019 (now pending),
which is a continuation of U.S. patent application Ser. No.
15/067,178, filed Mar. 11, 2016 (abandoned), which is a
continuation of U.S. patent application Ser. No. 13/525,220, filed
Jun. 15, 2012 (now U.S. Pat. No. 9,288,017), which is a
continuation of International Application No. PCT/KR2010/009039,
filed Dec. 16, 2010, which claimed priority to Korean Application
No. 10-2010-0066465, filed Jul. 9, 2010, Korean Application No.
10-2010-0010590, filed Feb. 4, 2010, and Korean Application No.
10-2009-0127310, filed Dec. 18, 2009, in the Korean Intellectual
Property Office, all of the disclosures of which are hereby
incorporated by reference.
BACKGROUND
(1) Field
[0002] Exemplary embodiments of the present invention relate to a
method for transmitting/receiving data when one station is to
communicate with several stations at the same time, in a wireless
packet communication system, in particular, a near field wireless
communication system.
(2) Discussion of the Background
[0003] Basically, the wireless LAN supports a basic service set
(BBS) including an access point (AP) and a plurality of wireless
stations excluding the AP. The AP serves as an access point of a
distribution system (DS). Hereafter, the AP and the stations are
commonly called `station`.
[0004] According to the IEEE 802.11n standard, when a station
receives a data frame, the station transmits an acknowledgement
(ACK) signal after a short inter frame space (SIFS) in order to
increase the transmission efficiency in a media access control
(MAC) layer, even though there is a difference depending on a
policy for an ACK signal required by the corresponding data
frame.
[0005] FIG. 1 is a timing diagram explaining data transmission in
the MAC layer according to the IEEE 802.11 standard.
[0006] When a station 1 transmits a data frame 101 to a station 2,
the station 2 receives the corresponding data frame and then
transmits an ACK signal 111 after an SIFS which is a predetermined
time. Such a method shown in FIG. 1 is frequently used in the MAC
layer of the wireless LAN.
[0007] Meanwhile, as the number of users using the wireless LAN has
rapidly increased, the request to improve data throughput provided
by one BSS is increasing. In the existing wireless LAN, one station
may communicate with only one station at a certain moment. However,
research has been conducted on technology which enables one station
to communicate with several stations at the same time, in order to
provide a gigabit or more throughput. As the representative
technology, a multi-user MIMO (hereafter, MU-MIMO) scheme and a
multi-frequency channel scheme are provided.
[0008] When those schemes are used, one station may operate as if
the station transmits and receives frames to and from several
terminals through several independent communication paths,
respectively. Accordingly, the station may transmit data to several
stations at the same time. As a result, it is possible to
significantly increase the throughput of the BSS.
[0009] However, when using the several communication paths at the
same time, the station has a limitation in which the transmission
and the reception cannot be performed at the same time through all
the used communication paths. For example, when a certain station
uses a communication path 1 and a communication path 2 at the same
time, the communication path 1 cannot be used for transmission in
case where the communication path 2 is used for reception.
[0010] All data frames used in the wireless LAN have a variable
length. As described above, an ACK or a block ACK is transmitted
immediately after a predetermined time passes from a time point
when the reception of data frames is completed. Therefore, when
data frames are simultaneously to several stations through several
communication paths, the respective stations will transmit an ACK
immediately after a predetermined time passes from a time point
when the reception of the data frames having different lengths was
completed. That is, a station having received a data frame having
the shortest length may transmit an ACK, before the transmission of
the data frames to the other stations is completed. In this case,
the corresponding ACK may not be received.
[0011] This will be described with reference to FIG. 2.
[0012] In FIG. 2, it is assumed that stations 1 and 2 exist and
data are transmitted between the stations 1 and 2 through different
communication paths. That is, when the station 1 transmits a data
frame 201 and a data frame 202 having different lengths, the
transmission of the data frame 201 having a shorter length may be
first completed. In this case, when the length of the data frame
201 is smaller than that of the data frame 202 by an SIFS 221 or
more, the station 2 transmits an ACK 211 immediately after the SIFS
221 passes from a time point when the reception of the data frame
201 is completed.
[0013] However, since the station 1 is still transmitting the data
frame 202 at the time point when the station 2 transmits the ACK
211, a reception impossible section 230 occurs, in which the
station 1 cannot receive the ACK 212 transmitted by the station
2.
SUMMARY
[0014] An embodiment of the present invention is directed to a
method capable of informing stations of the length of a data frame
having the largest length among data frames to be transmitted to
the respective stations, when several communication paths are
used.
[0015] Another embodiment of the present invention is directed to a
method in which a reception station transmits an ACK in a
predetermined time after a time corresponding to the length of the
largest data frame passes, thereby preventing a reception
impossible zone from occurring.
[0016] Other objects and advantages of the present invention can be
understood by the following description, and become apparent with
reference to the embodiments of the present invention. Also, it is
obvious to those skilled in the art to which the present invention
pertains that the objects and advantages of the present invention
can be realized by the means as claimed and combinations
thereof.
[0017] In accordance with an embodiment of the present invention,
there is provided a data transmission method in which a
transmission station transmits different data at the same time. The
data transmission method includes: acquiring length information of
data having the largest length among the different data; generating
a first signal field containing the length information of the data
having the largest length; and transmitting the first signal field
such that all stations receive the first signal field.
[0018] In accordance with another embodiment of the present
invention, there is provided a data reception method in which a
reception station receives data from a transmission station
transmitting different data to a plurality of reception stations at
the same time. The data reception method includes: receiving a
first signal field containing length information of data having the
largest length among the different data transmitted to the
respective reception stations at the same time; receiving data; and
waiting for a predetermined time after a time indicated by the
length information based on the length information contained in the
first signal field, and transmitting an acknowledgement (ACK) of
the received data.
[0019] In accordance with the embodiment of the present invention,
when one station transmits data to several stations at the same
time by using several communication paths and receives ACK signals,
a reception impossible zone does not occur. Therefore,
communication may be smoothly performed.
BRIEF DESCRIPTION OF DRAWINGS
[0020] FIG. 1 is a timing diagram explaining data transmission in a
MAC layer according to the IEEE 802.11 standard.
[0021] FIG. 2 is a diagram showing a case in which a problem occurs
due to the superposition of ACK signals depending on data lengths
for several communication paths used in a wireless communication
system.
[0022] FIG. 3 is a diagram showing the structure a general PPDU
used in a wireless communication system.
[0023] FIG. 4 is a diagram showing a signal field used in a
wireless LAN system.
[0024] FIG. 5 is a timing diagram in a case in which the entire PHY
overhead is transmitted by using a communication path through which
all stations may receive data in accordance with a first embodiment
of the present invention.
[0025] FIG. 6 is a timing diagram in a case in which a part of the
PHY overhead is transmitted by using a communication path through
which all stations may receive data, and the other parts of the PHY
overhead are transmitted by using communication paths independent
of each other in accordance with a second embodiment of the present
invention.
[0026] FIG. 7 is a timing diagram in a case in which the entire PHY
overhead is transmitted by using communication paths independent of
each other in accordance with a third embodiment of the present
invention.
[0027] FIG. 8 is a timing diagram in a case in which a signal field
is divided into two parts in accordance with the fourth embodiment
of the present invention.
[0028] FIG. 9 is a diagram showing a case in which length
information contained in an L-SIG field is used in accordance with
the embodiment of the present invention.
[0029] FIG. 10 is a diagram showing a case in which length
information contained in an L-SIG field is used to represent the
time length of the longest data frame and an SIG field contains
length information on the data amounts of data frames to be
transmitted to the respective stations.
[0030] FIG. 11 is a diagram showing a case in which length
information contained in an L-SIG field is used to represent the
time length of the longest data frame and SIG B fields included in
the respective communication fields contain length information on
the data amounts of data frames to be transmitted to the respective
stations.
[0031] FIG. 12 is a diagram showing a case in which a tail is
additionally attached to the back of an MPDU or A-MPDU.
[0032] FIG. 13 is a diagram showing a case in which a tail is
additionally attached to the back of an MPDU or A-MPDU.
DETAILED DESCRIPTION
[0033] Exemplary embodiments of the present invention will be
described below in more detail with reference to the accompanying
drawings. The present invention may, however, be embodied in
different forms and should not be constructed as limited to the
embodiments set forth herein. Rather, these embodiments are
provided so that this disclosure will be thorough and complete, and
will fully convey the scope of the present invention to those
skilled in the art.
[0034] A wireless communication system includes a MAC layer and a
physical (PHY) layer, each of which attaches overhead information
required for processing data. Therefore, a transmission unit of the
PHY layer attaches information for data processing of the PHY layer
to data received from the MAC layer and then transmits the data
through a wireless channel, and a reception unit of the PHY layer
extracts data to be transferred to the MAC layer by using the
attached information.
[0035] At this time, a PHY protocol data unit (PPDU) which is
outputted to the wireless channel by the PHY layer has a structure
as shown in FIG. 3.
[0036] The overhead information used in the PHY layer may be
roughly divided into a signal field 301 and a training field 302.
The training field 302 is used for synchronization detection and
wireless channel estimation, and the signal field 302 is used for
extracting MAC data (MPDU or A-MPDU) 303.
[0037] A signal field defined in the IEEE 802.11n standard which
provides the highest data rate, among current wireless LAN
standards, has a structure as shown in FIG. 4.
[0038] Among elements composing the signal field, Length 401 is
information representing the length of MAC data included in the
corresponding PPDU, and the PHY layer is set to transfer the
extracted MAC data and the length information to the MAC layer.
[0039] In this embodiment of the present invention, the length
information is used to inform the respective stations of the
largest value among the time lengths of the data frames transmitted
to several stations at the same time. A communication method using
this will be described briefly as follows.
[0040] A station which is to simultaneously transmit data to
several stations by using several communication channels at the
same time attaches a PHY layer overhead in front of the data frames
to be transmitted to the respective stations. At this time, length
information included in a signal field is set to represent the
largest value among the time lengths of the data frames to be
transmitted to the respective stations at the same time. Therefore,
a station receiving data will transmit an ACK after a time
indicated by the length information of the signal field passes,
although the reception of the data frames was completed.
[0041] Then, the several stations which have simultaneously
received the data frames may transmit ACK signals at the same time.
Therefore, a reception impossible zone does not occur, which has
occurred when the conventional technology was used.
[0042] Here, a method of representing a time length needs to be
calculated in the same time unit for all modulation and coding
schemes (MCS). Therefore, the number of symbols constructing a data
frame or a time-unit length such as microsecond may be used.
[0043] A method of attaching a PHY overhead, to which the
embodiment of the present invention is applied, will be described
below.
First Embodiment
[0044] In a first embodiment of the present invention, the entire
PHY overhead is transmitted by using a communication path through
which all stations may receive data. This will be described with
reference to FIG. 5.
[0045] FIG. 5 is a timing diagram in a case in which the entire PHY
overhead is transmitted by using a communication path through which
all stations may receive data in accordance with the first
embodiment of the present invention.
[0046] In FIG. 5, it is assumed that station 1 transmits data
frames 503 and 504 having different lengths to stations 2 and 3,
respectively.
[0047] The station 1 transmits a signal field 510 and a training
field 502 through bands or paths of the data frames 503 and 504, in
order to transmit the entire PHY overhead to all the stations. At
this time, length information included in the signal field 501 is
set to indicate the length of the data frame 504, because the data
frame 504 has the largest length. That is, the length information
represents the length of the data frame 504, as indicated by an
arrow 500 in the signal field 501.
[0048] Then, the stations 2 and 3 receive the data frames 503 and
504 by using the length information of the signal field 501, and
transmit ACK signals 511 and 512 corresponding to the respective
data frames 503 and 504 after waiting for a predetermined SIFS
521.
Second Embodiment
[0049] Next, a second embodiment of the present invention will be
described. In the second embodiment, a part of a PHY overhead is
transmitted by using a communication path through which all
stations may receive data, and the other parts of the PHY overhead
are transmitted by using communication paths independent of each
other. This will be described with reference to FIG. 6.
[0050] FIG. 6 is a timing diagram in a case in which a part of the
PHY overhead is transmitted by using a communication path through
which all stations may receive data, and the other parts of the PHY
overhead are transmitted by using communication paths independent
of each other in accordance with the second embodiment of the
present invention.
[0051] In FIG. 6, it is also assumed that the station 1 transmits
data frames 604 and 605 having different lengths to the stations 2
and 3, respectively.
[0052] The station 1 transmits a signal field 601 by using a
communication path through which all stations may receive data.
Furthermore, training fields 602 and 603 are transmitted only
through communication paths for the respective data frames 604 and
605. That is, the training field 602 for detecting the data frame
604 is transmitted only through the communication path for
transmitting the data frame 604, and the training field 603 for
detecting the data frame 605 is transmitted only through the
communication path for transmitting the data frame 605.
[0053] Although the transmission is performed in such a manner, the
stations 2 and 3 may confirm the length of the data frame 605,
because the signal field 601 represents the length of the data
frame 605 which is the longest frame between the data frames 604
and 605, as indicated by reference numeral 600.
[0054] Therefore, the stations 2 and 3 may wait for an SIFS 621
which is a predetermined time, after a time corresponding to the
value indicated by the length information, and then transmit ACK
signals 611 and 612 corresponding to the respective data frames 604
and 605.
Third Embodiment
[0055] In a third embodiment of the present invention, the entire
PHY overhead is transmitted by using communication paths
independent of each other. This will be described with reference to
FIG. 7.
[0056] FIG. 7 is a timing diagram in a case in which the entire PHY
overhead is transmitted by using communication paths independent of
each other in accordance with the third embodiment of the present
invention.
[0057] In FIG. 7, it is also assumed that the station 1 transmits
data frames 704 and 705 having different lengths to the stations 2
and 3, respectively.
[0058] In FIG. 7, training fields 701 and 702 and signal fields 703
and 704 are transmitted in correspondence to the data frames 704
and 705. That is, the training field 701 and the signal field 703
are transmitted through the communication path of the data frame
705, and the training field 702 and the signal field 704 are
transmitted through the communication path of the data frame
706.
[0059] At this time, the signal fields 703 and 704 represent the
length of the data frame 706 which is the longest frame between the
data frames 705 and 706, as indicated by reference numeral 700.
That is, even when the signal fields 703 and 704 are transmitted by
using communication paths independent of each other, the length
information contained in the signal field 703 should be identical
to the length information contained in the signal field 704.
[0060] Therefore, when receiving the data frame 705 and the data
frame 706, the stations 2 and 3 wait for an SIFS 721 which is a
predetermined time, after the reception of the data frame 706 is
completed, and then transmit ACK signals 711 and 712 corresponding
to the respective data frames 705 and 706.
Fourth Embodiment
[0061] In a fourth embodiment of the present invention, a part of a
signal field is transmitted by using a communication path through
which all stations may receive data, and the other part of the
signal field is transmitted by using communication fields
independent of each other. This will be described with reference to
FIG. 8.
[0062] FIG. 8 is a timing diagram in a case in which a signal field
is divided into two parts, one signal field is transmitted through
the communication path through which all stations may receive data,
and the other signal field is transmitted by using communication
fields independent of each other in accordance with the fourth
embodiment of the present invention.
[0063] In FIG. 8, it is also assumed that the station 1 transmits
data frames 806 and 807 having different lengths to the stations 2
and 3.
[0064] Referring to FIG. 8, a signal field 801 transmitted by using
a communication path through which all stations may receive data is
set to represent a length corresponding to the data frame 807
having the largest length between the respective data frames 806
and 807. Through this process, response times of different frames
may be confirmed as described above.
[0065] Next, training fields 802 and 803 are transmitted through
the corresponding communication paths of the respective data frames
806 and 807. Then, signal fields 804 and 805 for indicating the
lengths of the respective data frames 806 and 807 are contained.
That is, the signal field 801 transmitted through the communication
path through which all stations may receive data indicates Length1
810 representing the length of the longest data frame, the signal
field 804 corresponding to the data frame 806 indicates Length2
811, and the signal field 805 corresponding to the data frame 807
indicates Length3 812. Therefore, the length 810 of the actual data
frame and the data frames 806 and 807 may be transmitted by the
respective signal fields. At this time, the length information
contained in the signal field 804 may include a time length or a
length representing a data amount, for example, a length in the
unit of byte.
[0066] Then, the stations 2 and 3 receiving the data frames wait
for an SIFS 831 which is a predetermined time from a time point
when the transmission of the data frame 807 which is the longest
frame between the data frames 806 and 807 is completed, and then
transmit ACK signals 821 and 822 corresponding to the respective
data frames 806 and 807.
[0067] In the above-described four embodiments of the present
invention, it has been described that stations which have
simultaneously received data frames transmit ACK signals or block
ACK frames corresponding to the data frames at the same time.
However, the stations may sequentially transmit ACK signals or
block ACK frames, depending on a protocol. In this case, the
transmission time of an ACK signal or block ACK frame which is to
be first transmitted may be decided by the method in accordance
with the embodiments of the present invention, and the transmission
time of an ACK signal or block ACK frame which is to be transmitted
later may be decided by another method.
[0068] Furthermore, the structure of the frames used in the four
embodiments described with reference to the above drawings is a
conceptual structure. Therefore, when the frames are actually
applied, the frames may have a variety of specific forms.
[0069] In the wireless LAN, the backward compatibility with the
existing technology is considered to be very important. Therefore,
even when a more advanced method is used, a disadvantage should not
be given to a station using the existing method. Accordingly, a PHY
layer overhead of the existing method needs to be added in front of
a frame using the new method such that the station using the
existing method may perceive the length of the frame having a new
structure. In this case, length information contained in an L-SIG
field which is one of the PHY layer overheads in the existing
method may be used to represent the largest value among time
lengths of data frames which are to be transmitted to the
respective terminals at the same time.
[0070] A method of representing the length information of a frame
may include a method based on time such as several microseconds or
several symbol lengths and a method based on data amount such as
several bytes or several words. Depending on which method is used
between them, the position of a tail used for coding and decoding
of the PHY layer may be changed.
[0071] Based on this, specific examples of the transmitted frame
will be described with reference to FIGS. 9 to 13. At this time, a
long training field (LTF) may be transferred by using a
communication path through which all stations may receive data, as
shown in FIG. 5, or may be transferred by using a communication
path through only each station may receive data, as shown in FIGS.
6 to 8.
[0072] FIG. 9 is a diagram showing a case in which length
information contained in the L-SIG field is used to represent only
a time length of the longest data frame.
[0073] FIG. 9 shows a case in which different MPDUs or A-MPDUs 902
and 912 are transmitted. In the following descriptions, it is
assumed that the MPDUs 902 and 912 having different lengths from
each other are transmitted.
[0074] Since the end positions of frames for transmitting the MPDUs
902 and 912 having different lengths to several stations at the
same time should be matched with each other, pads should be
inserted into the MAC layer and the PHY layer in order to remove a
difference between the positions. That is, a MAC pad 903 is added
to the back of the MPDU 902, and a PHY pad 904 and a tail 905 are
sequentially added. Here, Service 1 (901) indicates a field for
representing a scramble seed of the PHY layer. Furthermore, a MAC
pad 913 is added to the back of the MPDU 912, and a PHY pad 914 and
a tail 915 are sequentially added. Here, Service 2 (902) indicates
a field for representing a scramble seed of the PHY layer.
[0075] As described above, information for representing the entire
length information according to an MPDU having the largest length
between the MPDUs 902 and 912 having different lengths may be
transmitted by using the length value of the L-SIG field 900, as
indicated by reference numeral 910. At this time, the length value
of the L-SIG field may be used as a time length as it is, or may be
converted into a time length by another method.
[0076] FIG. 10 is a diagram showing a case in which length
information contained in an L-SIG field is used to represent the
time length of the longest data frame and an SIG field contains
length information on the data amounts of data frames to be
transmitted to the respective stations.
[0077] FIG. 10 shows a case in which different MPDUs or A-MPDUs
1012 and 1022 are transmitted. In the following descriptions, it is
assumed that the MPDUs 1012 and 1022 having different lengths from
each other are transmitted.
[0078] Since the end positions of frames for transmitting the MPDUs
1012 and 1022 having different lengths to several stations at the
same time should be matched, pads should be inserted into the MAC
layer and the PHY layer in order to remove a difference between the
positions. That is, a MAC pad 1013 is added to the back of the MPDU
1012, and a PHY pad 1014 and a tail 1015 are sequentially added.
Here, Service 1 (1011) indicates a field for representing a
scramble seed of the PHY layer. Furthermore, a MAC pad 1023 is
added to the back of the MPDU 1022, and a PHY pad 1024 and a tail
1025 are sequentially added. Here, Service 2 (1021) indicates a
field for representing a scramble seed of the PHY layer.
[0079] As described above, information for representing the entire
length information according to an MPDU having the largest length
between the MPDUs 1012 and 1022 having different lengths may be
transmitted by using the length value of the L-SIG field 1000, as
indicated by reference numeral 1030. Furthermore, the information
of the respective MPDUs 1012 and 1022 may be represented by SIG
Length1 and SIG Length2 in an SIG field 1001.
[0080] In such a structure as shown in FIG. 10, the PHY layer of a
reception station may turn off a reception function of the station,
after decoding of data corresponding to the length of a frame
transmitted to the PHY layer is completed. Therefore, power
consumption may be effectively reduced.
[0081] FIG. 11 is a diagram showing a case in which length
information contained in an L-SIG field is used to represent the
time length of the longest data frame and SIG B fields included in
the respective communication fields contain length information on
the data amounts of data frames to be transmitted to the respective
stations.
[0082] FIG. 11 shows a case in which different MPDUs or A-MPDUs
1112 and 1122 are transmitted. In the following descriptions, it is
assumed that the MPDUs 1112 and 1122 having different lengths from
each other are transmitted.
[0083] Since the end positions of frames for transmitting the MPDUs
1112 and 1122 having different lengths to several stations at the
same time should be matched, pads should be inserted into the MAC
layer and the PHY layer in order to remove a difference between the
positions. That is, a MAC pad 1113 is added to the back of the MPDU
1112, and a PHY pad 1114 and a tail 1115 are sequentially added.
Here, Service 1 (1111) indicates a field for representing a
scramble seed of the PHY layer, and SIG B (1110) indicates a field
for representing the length of the MPDU 1112.
[0084] Furthermore, a MAC pad 1123 is added to the back of the MPDU
1122, and a PHY pad 1124 and a tail 1125 are sequentially added.
Here, Service2 (1121) indicates a field for representing a scramble
seed of the PHY layer, and SIG B2 (1120) indicates a field for
representing the length of the MPDU1 1122.
[0085] As described above, information for representing the entire
length information according to an MPDU having the largest length
between the MPDUs 1112 and 1122 having different lengths may be
transmitted by using the length value of the L-SIG field 1000, as
indicated by reference numeral 1130. Furthermore, the information
of the respective MPDUs 1112 and 1122 may be indicated by SIG
Length1 and SIG Length2 in an SIG B1 field 1110 and an SIG B2 field
1120, respectively.
[0086] In such a structure as shown in FIG. 11, the PHY layer of a
reception station may turn off a reception function of the station,
after decoding of data corresponding to the length of a frame
transmitted to the PHY layer is completed. Therefore, power
consumption may be effectively reduced.
[0087] FIGS. 12 and 13 show the same structures as shown in FIGS.
10 and 11, respectively, except that a tail is additionally
attached to the back of a MPDU or A-MPUD. When such a structure is
used, decoding of the MPDU or A-MPUD may be terminated immediately
after Tail A. Therefore, the power consumption in the reception
station may be more effectively reduced than in the structures of
FIGS. 10 and 11.
[0088] While the present invention has been described with respect
to the specific embodiments, it will be apparent to those skilled
in the art that various changes and modifications may be made
without departing from the spirit and scope of the invention as
defined in the following claims.
[0089] Embodiments of the present invention are applied to a WLAN
system using multiple user and multiple access.
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