D E S C R I P T I O N

RETRANSMISSION MANAGEMENT FOR WIRELESS CO

APPARATUS

Technical Field

The present invention relates to a wir

communication apparatus suitable for a cell

wireless LAN apparatus

Background Art

In a CSMA/CA type wireless communicati

represented by wireless LAN communication d

IEEE 802 11 in conventional wireless commun

systems, if an acknowledgement frame (Ack f

transmission data cannot be received, the t

data is retransmitted In this case, on th

the retry count and lifetime unique to each

transmission data, retransmission is limite

the retry count and transmittable time of t

transmission data

In the QoS (Quality of Service) -extend

LAN standard IEEE 802 lie, communication is

control method using centralized control is

HCCA (HCF Controlled Channel Access) method

former access control method using distribu

is called an EDCA (Enhanced Distributed Cha

method A wireless LAN terminal is able to

medium by using one of these access control

acquire TXOP (transmission opportunity) rep

period during which a plurality of data can

transmitted, and communicate data during th

period (see IEEE 802 lie Draft 13 0, IEEE

P802 Ile/Dl3 0, January 2005 below)

In IEEE 802 Hn aiming at high-speed t

has proposed a method in which a terminal h

acquired a TXOP period gives a part of this

to the data receiving terminal, and bi-dire

communication is performed by a piggy back

the TXOP period, thereby increasing the tra

efficiency This method is called a bi-dir

data flow or reverse direction

In IEEE 802 Hn, unlike in the existin

802 11 standard, an aggregation frame is fo

terminal (initiator) transmits an IAC frame

receiving terminal (responder) returns an R

when SIFS has elapsed after that, thereby p

IAC-RAC frame exchange Alternatively, RTS

exchange defined by IEEE 802 11 may also be

instead of IAC-RAC frame exchange

When IAC-RAC frame exchange is to be p

the bi-directional data flow, the data rece

terminal notifies a data frame length and t

data rate, which the terminal can transmit

part of a TXOP period, by writing the data

frame

On the basis of the values written in

frame, the transmitting terminal determines

(RDG duration reverse direction communicat

permission period) of the TXOP period, whic

given after an aggregation frame is transmi

transmitting terminal writes the determined

duration in an IAC frame, attaches the IAC

head of the aggregation frame, and transmit

aggregation frame when SIFS has elapsed aft

bi-directional data flow is used, the recei

terminal transmits the Block Ack frame when

elapsed by using the piggy back method by w

data frames are transmitted as they are agg

the Block Ack frame, thereby simultaneously

transmitting the data and Block Ack frame

case, the transmission time of the aggregat

formed by aggregating several data frames i

Ack frame cannot exceed the time of the RDG

written in the IAC frame

In this manner, a part of the TXOP per

by the transmitting terminal can be given t

receiving terminal

If the receiving terminal further requ

duration when transmitting an aggregation f

piggy back method, the receiving terminal c

request an RDG duration by writing, in an R

data frame length and transmission data rat

for transmission, and returning the RAC fra

attaching it to the head of the aggregation

transmitted by the piggy back method (see T

The following problem arises if the re

limiting method for each transmission data

the existing IEEE 802 11 is applied to the

retransmission limiting method for burst tr

such as the Block Ack method defined in the

conventional IEEE 802 lie That is, if dat

error has occurred by burst transmission is

simultaneously with new transmission data,

transmissions are excessively concentrated

terminal

Also, when the transmission opportunit

having a plurality of priority degrees are

accordance with the priority degrees as def

conventional IEEE 802 lie, the transmission

opportunities are excessively given to the

priority degree

The above problem similarly arises in

aggregation method by which a plurality of

data are aggregated into one frame as burst

problem also similarly arises in the bi-dir

data flow method by piggy back in which a p

error occurs in the data transmitted from t

transmitting side and an error occurs in on

transmitted from the receiving side, the tr

side need not retransmit the data Therefo

retransmission band is allocated to the rec

so the data in which the error has occurred

retransmitted unless the receiving terminal

the transmission right

In addition, when data transmission is

from a terminal station to a base station i

method of IEEE 802 lie, a QoS Cf-poll frame

transmitted to give the terminal station th

transmission right of a TXOP period, and th

having acquired the transmission right tran

during this TXOP period If a transmission

the like occurs in the TXOP period and TXOP

reallocation is immediately performed, TXOP

may be concentrated to the same terminal

Disclosure of Invention

It is, therefore, an object of the pre

invention to provide a wireless communicati

According to one aspect of the present

a wireless communication apparatus includes

transmitting device which transmits a first

frame in which first transmission data fram

aggregated, a measuring device which measur

value of retransmission of each of the firs

transmission data frames, a storage to stor

value of the number value of retransmission

determination device which determines wheth

number value of retransmission of each of t

transmission data frames exceeds the limiti

transmission buffer which buffers the first

transmission data frames for which it is de

that the number value of retransmission doe

the limiting value, and discards the first

data frames for which it is determined that

value of retransmission exceeds the limitin

the first transmission data frames, and a

retransmitting device which retransmits the

aggregation frame in which the first transm

frames buffered in the transmission buffer

data flow method,

FIG 3 is a view for explaining a conv

retransmission method in burst transmission

FIG 4 is a view for explaining a retr

limiting method using the lifetime for each

exchange sequence of burst data when retran

performed in burst transmission,

FIG 5 is a view for explaining the bi

data flow method which is a piggy back type

bi-directional communication method using a

frame,

FIG 6 is a view for explaining a retr

limiting method according to the second emb

using the retry count for each frame exchan

of burst data,

FIG 7 is a view for explaining a retr

limiting method according to the third embo

FIG 8 is another view for explaining

retransmission limiting method according to

embodiment

Best Mode for Carrying Out the Inve

communication methods from which the effect

present embodiment can be expected, so the

embodiment is applicable not only to IEEE 8

also to general wireless communication meth

the embodiment will be explained by taking,

example, a case in which the piggy back typ

bi-directional data flow method proposed in

802 Hn is applied as one of burst transmis

communication methods Note that a burst t

communication method to which the present e

applicable is not limited to the bi-directi

flow method For example, the present embo

applicable to a method which uses a poll ty

instead of a band allocation method for a r

terminal in the bi-directional data flow me

As is well known, in wireless communic

CSMA/CA, a wireless communication terminal

intends to transmit data packet by packet p

carrier sense before transmission of each d

avoiding collision with packets from other

In burst transmission in which a plurality

aggregation method, a plurality of transmis

are aggregated into one frame and the frame

transmitted by burst transmission In this

various aggregation methods are possible

a method in which a plurality of MAC frames

aggregated into one PHY frame and a preambl

attached to only the head of the frame, and

which increases the error estimation accura

inserting a mid preamble in the middle of o

frame The present embodiment is not limit

specific aggregation method, and applicable

communication methods which perform burst-l

transmission In addition, the present emb

applicable not only to transmission using a

frames, but also to a communication method

performs burst transmission in which data f

spaced by SIFS periods or RIFS periods in a

communication period

As shown in FIG 1, a wireless communi

apparatus 101 according to this embodiment

transmission data manager 102 which has a t

and, when a plurality of transmission data

transmitted by burst transmission, performs

retransmission limitation for each frame ex

sequence of burst data, which is different

retransmission limitation unique to each tr

data performed by the transmission data man

transmission processor 104 which performs a

transmitting process, and a reception proce

which performs a received frame identificat

and a receiving process by which, e g , a b

acknowledgement is formed

The transmission data manager 102 comp

transmission queue manager 106 which has a

queue for buffering transmission data, a pa

transmissibility determination unit 107 whi

a retransmission limitation unique to each

data, and a backoff processor 108 which per

backoff processing based on CSMA/CA

The transmission queue manager 106 inc

counter for counting the retry count of eac

transmission data

transmission queue manager 106 by using the

the lifetime of each transmission data obta

transmission/reception state manager 110 (t

described later) by using a timer, thereby

whether to retransmit each packet

The access controller 103 comprises a

transmitting/receiving method determination

which determines, e g , a data transmitting

be used in data transmission such as an agg

method or bi-directional data flow method,

of TXOP, and a retransmission limiting meth

to the present embodiment which is performe

frame exchange sequence of burst data, the

transmission/reception state manager 110 wh

the timings of data transmission/reception

the transmitting/receiving method determine

data transmitting/receiving method determin

109, performs access control in a retransmi

process and the like, and, when a plurality

transmission data are to be transmitted by

transmission, performs a retransmission lim

frames, and a carrier sense unit 112 which

carrier sense information required in the b

processor 108

The transmission/reception state manag

includes a timer for measuring the lifetime

frame exchange sequence of burst data

The reception processor 105 comprises

information identification unit 113 which i

the success or failure of the reception of

frame and control information in the receiv

and a bitmap formation unit 114 which, when

is received, forms a bitmap of acknowledgem

placed in an acknowledgement frame from the

failure of the reception of each frame in t

data

First, a burst transmission method per

the bi-directional data flow method will be

with reference to FIG 2 In the bi-direct

flow method, a terminal A 201 having acquir

transmission right describes the use of the

bi-directional data flow method in an IAC (

returns the RAC frame 204 The terminal A2

received the RAC frame 204 forms an aggrega

by aggregating a plurality of transmission

attaching the IAC frame 205 to the head of

and transmits the aggregation frame In th

transmission period 206, which is determine

basis of, e g , the information described i

frame 204, to be given to the terminal B 20

described in the IAC frame 205 When recei

aggregation frame having the IAC frame 205

the head, the terminal B 202 forms a Block

207 containing the reception status of each

Then, the terminal B 202 forms an aggregati

adding an RAC frame 208 before the Block Ac

and aggregating a plurality of transmission

transmitted to the terminal A 201 after the

frame 207, and returns the aggregation fram

that the transmission period of the aggrega

returned by the terminal B 202 does not exc

transmission period 206 given from the term

to the terminal B 202 Note also that it i

received a plurality of number of times T

of the bi-directional data flow method is d

detail in TGn Sync Proposal Technical Speci

IEEE 802 ll-04/889r4, March 2005 described

In a conventional retransmission metho

FIG 3, after frame exchange between an IAC

RAC frame is completed, a terminal A 301 ca

RDG duration as a transmission period to be

to a terminal B 302, writes the RDG duratio

frame, forms an aggregation frame together

plurality of transmission data Data 1-A, Da

3-A, and Data 4-A from the terminal A 301,

transmits the aggregation frame The termi

having received the plurality of transmissi

1-A, Data 2-A, Data 3-A, and Data 4-A trans

the terminal A 301 forms a Block Ack frame

describing the reception statuses of the pl

transmission data The terminal B 302 form

aggregation frame which falls within the ra

RDG duration as the transmission period giv

terminal A 301, by aggregating the Block Ac

In the first burst data frame exchange

304 performed by the bi-directional data fl

if Data 3-A and Data 4-A transmitted by the

301 are transmission errors, the terminal A

from the reception statuses described in th

frame 303 that Data 3-A and Date 4-A must b

retransmitted Therefore, when returning a

frame 305 describing the reception statuses

plurality of transmission data Data 1-B, Da

3-B, and Data 4-B transmitted by the termin

the terminal A 301 does not return only the

Frame 209 as shown in FIG 2, but forms an

frame by aggregating the Block Ack frame 30

frame 306, Data 3-A and Data 4-A as the ret

data, and Data 5-A as new data, and transmi

aggregation frame The terminal A 301 dete

Data 2-B and Data 3-B transmitted by the te

are transmission errors when forming the Bl

frame 305, so the terminal A 301 describes

frame 306 a period during which the termina

retransmit Data 2-B and Data 3-B Then, th

an aggregation frame which falls within the

the RDG duration as the transmission period

the terminal A 301, by aggregating an RAC f

Block Ack frame 307, Data 2-B and Data 3-B

retransmission data from the terminal B 302

5-B as new data, and returns this aggregati

the terminal A 301

If a transmission error occurs in the

transmitted by a frame exchange sequence 30

first retransmission of the burst data, an

frame as burst data is retransmitted again

to FIG 3, in a frame exchange sequence 309

second retransmission of the burst data, Da

the terminal A 301 and Data 3-B from the te

are retransmission data, and an aggregation

formed by further aggregating new data afte

retransmission data is transmitted and rece

transmission errors keep occurring in some

transmitted from the terminal A 301 or term

as described above, the problem that data

transmission/reception is kept performed by

using the lifetime for each frame exchange

burst data when the burst data is retransmi

bi-directional data flow method will be exp

with reference to FIGS 1 and 4

When data is stored in the transmissio

the transmission queue manager 106 of the t

data manager 102 of the wireless communicat

apparatus 101 of a terminal A 401, the tran

queue manager 106 instructs the backoff pro

to perform backoff processing The backoff

108 instructed to perform backoff processin

about the use state of a radio space manage

carrier sense unit 112 If the use state i

backoff processor 108 performs a countdown

backoff After completing this backoff cou

backoff processor 108 notifies the transmis

manager 106 of the completion of backoff

backoff completion, the terminal A 401 acqu

transmission right

The transmission queue manager 106 not

backoff completion transmits the number of

of each transmission data has not exceeded

limit (retransmission limitation) of the tr

data After confirming the lifetime and re

each transmission data, the packet transmis

determination unit 107 transmits the number

stored in the transmission queue and the tr

data to the transmission/reception state ma

the access controller 103 The transmissio

state manager 110 notifies the transmitting

method determination unit 109 of the number

stored in the transmission queue to determi

to use the bi-directional data flow method,

to perform IAC-RAC frame exchange before th

transmission of an aggregation frame In t

embodiment, it is determined that the bi-di

data flow method is used and IAC-RAC frame

performed At this time, the transmission/

state manager 110 notified of the determine

transmitting/receiving method from the data

transmitting/receiving method determination

sets (starts) the timer of lifetime 403 for

the use of the bi-directional data flow met

transmits the formed IAC frame to the trans

processor 104 As shown in FIG 4, the tra

processor 104 having received the IAC frame

it as an IAC frame 404 for starting the bi-

data flow method from the terminal A 401 to

B 402

In the terminal B 402 having received

frame 404, the frame information identifica

113 of the reception processor 105 identifi

frame describing the start of the bi-direct

flow method, and transmits to the

transmission/reception state manager 110 a

signal which requests transmission of an RA

describing a transmission rate and frame le

transmitted when the transmission right is

bi-directional data flow The transmission

state manager 110, which has received this

transmission request, of the terminal B 402

the data amount in the transmission queue o

transmission queue manager 106, and determi

transmitted when the transmission right is

bi-directional data flow and an RAC frame w

elapsed after the IAC frame 404 is received

formation/transmission processor 111 forms

and transmits it from the transmission proc

The terminal A 401 receives from the t

402 the RAC frame which responds to the IAC

and starts a first burst data frame exchang

405 by the bi-directional data flow method

has elapsed after frame exchange between th

and RAC frame is completed When the RAC f

received by the terminal A 401, the frame i

identification unit 113 of the reception pr

of the terminal A 401 identifies the receiv

frame As a result of the identification o

frame, the frame information identification

extracts the transmission rate and frame le

are described in the RAC frame, to be trans

the terminal B 402 is given the transmissio

the bi-directional data flow, and notifies

transmission/reception state manager 110 of

transmission right by the bi-directional da

using the values notified from the

transmission/reception state manager 110, t

transmitting/receiving method determination

determines the number of data or a data fra

be transmitted from the terminal A 401 and

(RDG duration) of a part of a TXOP period t

to the terminal B 402 The transmission/re

state manager 110 requests the transmission

manager 106 to extract, from the transmissi

transmission data necessary to perform data

transmission by the number of data or the d

length, which is determined by the data

transmitting/receiving method determination

to be transmitted from the terminal A 401

transmissibility determination unit 107 con

the transmission time of each of the transm

extracted by the transmission queue manager

exceeded the lifetime uniquely managed for

transmission data, and that the retry count

transmission data has not exceeded the retr

and four data frames Data 1-A, Data 2-A, Da

Data 4-A to be transmitted by the first bur

frame exchange sequence 405 p-erformed by th

bi-directional data flow method The frame

formation/transmission processor 111 forms

406 by using the value of RDG duration dete

the data transmitting/receiving method dete

unit 109, forms an aggregation frame by agg

total of five MAC frames, i e , the IAC fra

four data frames Data 1-A, Data 2-A, Data 3

4-A, and transmits the aggregation frame

The terminal B 402 having received the

frame formed by aggregating a total of five

i e , the IAC frame 406 and four data frame

Data 2-A, Data 3-A, and Data 4-A returns an

frame when SIFS has elapsed after the aggre

from the terminal A 401 is received The f

information identification unit 113 in the

processor 105 of the terminal B 402 identif

frame in the aggregation frame received fro

terminal A 401 The frame information iden

frame, and the bitmap formation unit 114 fo

of the reception statuses of the plurality

frames and notifies the transmission/recept

manager 110 of the bitmap The transmissio

state manager 110 notified of the value of

in the IAC frame 406 and the bitmap of the

statuses of the plurality of data frames ex

transmission data Data 1-B, Data 2-B, Data

Data 4-B from the transmission queue manage

order to form an aggregation frame which ca

transmitted by the value of RDG duration in

frame 406 When four transmission data Dat

2-B, Data 3-B, and Data 4-B are extracted f

transmission queue manager 106, the packet

transmissibility determination unit 107 con

the transmission time of each transmission

exceeded the lifetime uniquely managed for

transmission data, and that the retry count

transmission data has not exceeded the retr

the transmission data, and transmits the fo

transmission data to the transmission/recep

formation/transmission processor 111 forms

frame, forms a Block Ack frame 407 by using

of the reception statuses of the plurality

frames, which is formed by the bitmap forma

114, forms an aggregation frame by aggregat

of six MAC frames, i e , the RAC frame, the

frame 407, and four data frames Data 1-B, D

Data 3-B, and Data 4-B, and returns this ag

frame Note that the value of RDG duration

in the IAC frame 406 cannot be exceeded

When the aggregation frame returned fr

terminal B 402 is received, the frame infor

identification unit 113 of the reception pr

of the terminal A 401 detects by the bitmap

reception statuses described in the Block A

transmitted from the terminal B 402 that Da

Data 4-A transmitted by the terminal A 401

normally received Subsequently, when a bi

reception statuses of the plurality of data

aggregated after the Block Ack frame 407 is

using the frame information identification

transmission/reception manager 110, which h

determined that retransmission is necessary

terminal A 401 notifies the packet transmis

determination unit 107 that retransmission

performed, and the packet transmissibility

determination unit 107 counts up the retry

Data 3-A and Data 4-A as the retransmission

the terminal A 401, and confirms that each

retry count has not reached the upper limit

retry count of the data, and that the lifet

to each data has not expired After confir

the retry count has not reached the upper l

retry count and the lifetime unique to each

not expired, the packet transmissibility de

unit 107 notifies the data transmitting/rec

method determination unit 109 of the frame

retransmission frame and the length of a ne

existing in the transmission queue, via the

transmission/reception manager 110, and the

transmitting/receiving method determination

determines that period of a frame exchange

unit 109 and necessary when data is retrans

determines whether the frame exchange seque

which is the period necessary when data is

retransmitted, for the first retransmission

burst data can be transmitted within the re

of the timer of the lifetime 403 for each f

exchange sequence of the burst data If th

exchange sequence 408 for the first retrans

the burst data can be transmitted within th

time of the timer of the lifetime 403 for e

exchange sequence of the burst data, the fi

retransmission of the burst data is perform

In the frame exchange sequence 408 for

retransmission of the burst data, the data

transmitting/receiving method determination

has already confirmed that Data 3-A and Dat

retransmission data from the terminal A 401

reached the upper limits of the retry count

lifetime unique to each data has not expire

packet transmissibility determination unit

retry bits of Data 3-A and Data 4-A, extrac

Data 5-A as the new transmission data to th

transmission/reception manager 110 The

transmission/reception manager 110 transmit

frame formation/transmission processor 111,

transmission period for retransmission to b

the terminal B 402, which is determined by

transmitting/receiving method determination

Data 3-A and Data 4-A as the retransmission

5-A as the new transmission data, and that

the statuses of the plurality of data frame

after the Block Ack frame 407, which is for

bitmap formation unit 114 The frame

formation/transmission processor 111 transm

frame exchange sequence 408 for the first

retransmission of the burst data, an aggreg

formed by aggregating an IAC frame describi

transmission period for retransmission to b

the terminal B 402, a Block Ack frame which

reception statuses to the terminal B 402, D

1 Data 4-A as the retransmission data, and Da

the new transmission data, when SIFS has el

terminal A 401 After confirming that the

of the retry count is not reached and the l

not expired for both Data 2-B and Data 3-B,

terminal B 402 forms an aggregation frame b

aggregating Data 2-B and Data 3-B as the re

data after an RAC frame and Block Ack frame

setting retry bits of Data 2-B and Data 3-B

aggregating Data 5 as new data, and returns

aggregation frame when SIFS has elapsed, th

performing the frame exchange sequence 408

first retransmission of the burst data

When the aggregation frame returned fr

terminal B 402 is received by the terminal

frame exchange sequence 408 for the first

retransmission of the burst data, the frame

identification unit 113 of the reception pr

of the terminal A 401 analyzes the bitmap o

reception statuses described in a Block Ack

transmitted from the terminal B 402, and de

Data 5-A newly transmitted by the terminal

frame exchange sequence 408 for the first

retransmitted by the terminal B 402 in the

exchange sequence 408 for the first retrans

the burst data is not normally received T

transmission/reception manager 110, which h

these pieces of information indicating the

receptions, of the terminal A 401 determine

retransmission is necessary The

transmission/reception manager 110, which h

determined that retransmission is necessary

terminal A 401 notifies the packet transmis

determination unit 107 that retransmission

performed, and the packet transmissibility

determination unit 107 counts up the retry

Data 5-A as the retransmission data from th

401, and confirms that the counted-up retry

not reached the upper limit of the retry co

data, and that the lifetime unique to the d

expired Since Data 5-A whose retry count

are confirmed is data newly transmitted in

exchange sequence 408 for the first retrans

the burst data, the upper limit of the retr

the length of a new frame existing in the t

queue, via the transmission/reception manag

the data transmitting/receiving method dete

unit 109 determines that period of a frame

sequence 410 for the second retransmission

data, which is necessary when data is retra

The data transmitting/receiving method dete

unit 109 notifies the transmission/receptio

110 of the determined period of the frame e

sequence 410 for the second retransmission

data The transmission/reception manager 1

determines whether the frame exchange seque

which is notified by the data transmitting/

method determination unit 109 and serves as

period when data is retransmitted, for the

retransmission of the burst data can be tra

within the remaining time of the timer of t

403 for each frame exchange sequence of the

As shown in FIG 4, if the frame exchange s

for the second retransmission of the burst

be transmitted within the remaining time of

first retransmission of the burst data, and

a burst data frame exchange sequence 412 pe

another terminal by the bi-directional data

method In this case, it is already confir

5-A as an object of retransmission in the t

401 that the retry count has not reached th

limit of the retry count of the data and th

unique to the data has not expired, so Data

returned to the transmission queue in the t

queue manager 106

The operation after the retransmission

burst data is interrupted is not limited to

data transmission/reception process perform

another terminal by the aggregation method,

also possible to advance to, e g , burst da

transmission performed for another priority

the same terminal by the aggregation method

transmission performed for another terminal

other than the aggregation method, burst da

transmission performed for another priority

the same terminal by a method other than th

DCF method of IEEE 802 11 or the EDCA metho

802 lie Referring to FIG 4, the interval

Block Ack frame 411 and the burst data fram

sequence 412 performed for another terminal

bi-directional data flow method is short

the burst data frame exchange sequence 412

for another terminal by the aggregation met

HCCA method, this interval can be an interv

performing PIFS carrier sense If the burs

exchange sequence 412 performed for another

the aggregation method is the EDCA method,

interval can be an interval for performing

sense and backoff processing

Also, when the transmission/reception

manager 110 in the access controller 103 of

terminal A 401 determines whether the frame

sequence 410 for the second retransmission

data can be transmitted within the remainin

the timer of the lifetime 403 for each fram

sequence of the burst data, if the whole fr

sequence 410 for the second retransmission

data, retransmission is performed by using

retransmission data without attaching any n

there is a time for transmitting only Data

retransmission data and Data 6-A as new dat

terminal A 401, only the data from the term

is transmitted without using the bi-directi

flow method That is, data transmission/re

be performed within a transmissible range i

with the remaining time of the timer of the

403 for each frame exchange sequence of the

In this embodiment, as the method of s

retransmission, the Implicit Block Ack Requ

proposed in IEEE 802 Hn is used as a metho

increasing the efficiency of the Block Ack

standardized by IEEE 802 He This is the

omits a Block Ack Request frame which is ne

receive a Block Ack frame indicating the re

status of transmission data from terminal B

Block Ack method of IEEE 802 He Since th

retransmission limiting method according to

embodiment can be used regardless of the me

and 3 for the both in the first retransmiss

However, the number of data to be aggregate

limit the form of use of this embodiment, s

of data to be aggregated can be variable or

the same for terminals A and B

Although an IAC frame and RAC frame ar

at the start of data transmission in this e

it is also possible to use a method in whic

frame and CTS frame are exchanged instead o

frame and RAC frame or terminal A transmits

frame, or to start aggregation frame transm

immediately after the data transmission rig

acquired without performing any frame excha

the IAC frame and the like In addition, a

is used as a method by which terminal A giv

transmission period to terminal B, but anot

such as a QoS Cf-PoIl frame may also be use

described later in the second embodiment, o

transmission period may also be described i

frame without using any other frame If no

is used at the head of each aggregation fra

transmissibility determination unit 107 of

transmission data manager 102 of the wirele

communication apparatus 101 determines whet

discard the transmission data by using the

and lifetime uniquely managed for the trans

data The transmission data is returned to

transmission queue in the transmission queu

106, if the timer of the lifetime 403 for e

exchange sequence of burst data has expired

retry count uniquely managed for the transm

has not reached the upper limit of the retr

the lifetime uniquely managed for the trans

has not expired If the retry count unique

for the transmission data has exceeded the

of the retry count or the lifetime uniquely

the transmission data has expired, the data

returned to the transmission queue but disc

In this embodiment as described above,

retransmission of burst data in burst trans

be limited for each frame exchange sequence

burst data, so scheduling calculations can

embodiment except that the retry count for

exchange sequence of burst data is used ins

using the lifetime 403 for each frame excha

of burst data to limit the retransmission o

data as explained in the first embodiment,

QoS Cf-PoIl frame is used instead of an IAC

RAC frame by the bi-directional data flow m

is a piggy back type bi-directional communi

method, so the differences from the first e

will be mainly explained below

First, a communication method conformi

bi-directional data flow method which is a

type bi-directional communication method us

Cf-PoIl frame will be explained with refere

FIG 5 Before data transmission, a termin

having acquired the transmission right afte

carrier sense and backoff processing or aft

carrier sense notifies a terminal B 502 tha

transmission is to be performed by transmit

frame 503 to the terminal B 502 The termi

returns a CTS frame 504 to the terminal A 5

aggregating the QoS Cf-PoIl frame 505 and D

Data 2-A, Data 3-A, and Data 4-A as data to

transmitted to the terminal B 502, and tran

aggregation frame to the terminal B 502 T

B 502 having received the aggregation frame

QoS Cf-PoIl frame 505 attached to the head

period 506 to be given to the terminal B 50

QoS Cf-PoIl frame 505 The terminal B 502

Block Ack frame 507 for returning the recep

statuses of Data 1-A, Data 2-A, Data 3-A, a

as the received data, forms an aggregation

aggregating, after the Block Ack frame 507,

Data 2-B, Data 3-B, and Data 4-B as data to

transmitted to the terminal A 501, and tran

aggregation frame In this case, the termi

forms an aggregation frame which does not e

period 506 to be given to the terminal B 50

Cf-PoIl frame 505, as the aggregation frame

returned The terminal A 501 having receiv

aggregation frame returned from the termina

having the Block Ack frame 507 attached to

transmitted and no more data is transmitted

terminal A 501, the transmission process fr

terminal A 501 can be completed by the tran

the Block Ack frame 508 Also, if an NAV (

Allocation Vector) for performing virtual c

to avoid transmission from other terminals

more than the transmission end time of the

frame 508 by the RTS frame 503 and CTS fram

possible to use a method of clearing the NA

transmitting a Cf-end frame when SIFS has e

the transmission of the Block Ack frame 508

to clear the NAV

A case in which the retry count for ea

exchange sequence of burst data is used as

retransmission limiting method according to

embodiment when retransmission in burst tra

performed by the bi-directional data flow m

piggy back type bi-directional communicatio

using a QoS CF-PoIl frame will be explained

reference to FIGS 1 and 6

In this embodiment, the retry count fo

the first embodiment, and the upper limit o

count for each frame exchange sequence of b

2 That is, burst data is retransmitted on

However, the upper limit of the retry count

frame exchange sequence of burst data is no

2, and can be adjusted in accordance with t

use

When data is stored in a transmission

transmission queue manager 106 of a transmi

manager 102 of a wireless communication app

of a terminal A 601, the transmission right

by performing AIFS carrier sense and backof

or PIFS carrier sense by using a carrier se

and backoff processor 108 in the same manne

first embodiment After the transmission r

acquired, the transmission queue manager 10

the number of data stored in the transmissi

the transmission data to a packet transmiss

determination unit 107 The packet transmi

determination unit 107 confirms that the tr

time of each transmission data has not exce

stored in the transmission queue and the tr

data to a transmission/reception state mana

an access controller 103 The transmission

state manager 110 notifies a data

transmitting/receiving method determination

the number of data stored in the transmissi

and determines, e g , whether to use the bi

data flow method, and whether to perform RT

exchange before transmission of an aggregat

In this embodiment, it is determined that t

bi-directional data flow method is used and

frame exchange is performed The

transmission/reception state manager 110 no

the determined data transmitting/receiving

the data transmitting/receiving method dete

unit 109 initializes the retry count for ea

exchange sequence of burst data (initialize

count to 0) After that, the transmission/

state manager 110 instructs a frame

formation/transmission processor 111 to tra

frame The frame formation/transmission pr

to a terminal B 602

The terminal B 602 having received the

603 returns a CTS frame 604 when SIFS has e

the RTS frame 603 is received As the fram

the RTS frame 603 and CTS frame 604, normal

formats standardized by IEEE 802 11 are use

the transmission/reception state manager 11

terminal A 601 having received the CTS fram

notified of the reception of the CTS frame

frame information identification unit 113 o

reception processor 105 When starting a f

data frame exchange sequence 605 by the bi-

data flow method, the transmission/receptio

manager 110 notifies the data transmitting/

method determination unit 109 of a data len

transmitted The data transmitting/receivi

determination unit 109 determines a transmi

to be given to the terminal B 602 when the

bi-directional data flow method is used, an

the transmission/reception state manager 11

determined transmission period The

transmitting/receiving method determination

The frame formation/transmission processor

QoS Cf-PoIl frame 606 describing the transm

period to be given to the terminal B 602 wh

bi-directional data flow method is used, fo

aggregation frame by aggregating the QoS Cf

606 and Data 1-A, Data 2-A, Data 3-A, and D

the transmission data, and transmits the ag

frame to the terminal B 602 by using the tr

processor 104 As in the first embodiment,

terminal B 602 forms a Block Ack frame 607

the reception statuses of Data 1-A, Data 2-

and Data 4-A, forms an aggregation frame by

the Block Ack frame 607 and Data 1-B, Data

3-B, and Data 4-B as data to be transmitted

terminal A 601, and returns the aggregation

the terminal A 601 In this case, the term

forms a frame which does not exceed that tr

period to be given to the terminal B 602 wh

bi-directional data flow method is used, wh

described in the QoS Cf-PoIl frame 606, as

Data 1-B, Data 2-B, Data 3-B, and Data 4-B

terminal B 602 detects that Data 3-A and Da

transmitted by the terminal A 601 and Data

3-B transmitted by the terminal B 602 are t

errors and must be retransmitted, as in the

embodiment In this case, as in the first

the transmission/reception state manager 11

whether the first retransmission of the bur

possible The transmission/reception state

counts up the retry count for each frame ex

sequence of the burst data from 0 to 1, and

whether the retry count has exceeded 2 as t

limit of the retry count for each frame exc

sequence of the burst data Since the retr

each frame exchange sequence of the burst d

exceeded 2 as the upper limit of the retry

first retransmission of the burst data is p

In a frame exchange sequence 608 for t

retransmission of the burst data, as in the

embodiment, the packet transmissibility det

unit 107 of the terminal A 601 checks the r

610 describing a period to be given to the

602 again, Data 3-A and Data 4-A as the ret

data, and Data 5-A as the new transmission

terminal B 602 having received the aggregat

transmitted from the terminal A 601 in the

exchange sequence 608 for the first retrans

the burst data returns an aggregation frame

aggregating a Block Ack frame, Data 2-B and

the retransmission data, and Data 5-B as ne

transmission data as in the first embodimen

performing the frame exchange sequence 608

first retransmission of the burst data

Then, after frame exchange is complete

frame exchange sequence 608 for the first

retransmission of the burst data, the

transmission/reception state manager 110 of

terminal A 601 confirms transmission errors

transmitted by the terminal A 601 and Data

transmitted by the terminal B 602 If an a

controller 12 of a wireless communication a

determines that the second retransmission i

whether the retry count has exceeded 2 as t

limit of the retry count for each frame exc

sequence of the burst data Since the retr

each frame exchange sequence of the burst d

to 2 as the upper limit of the retry count,

data retransmission process is interrupted

case, the terminal A 601 interrupts the bur

transmission/reception process by transmitt

Ack frame 612, instead of a frame exchange

for the second retransmission of the burst

SIFS has elapsed after the frame exchange s

for the first retransmission of the burst d

advances to a burst data frame exchange seq

performed for another terminal by the bi-di

data flow method using a QoS Cf-PoIl frame

is already confirmed for Data 5-A as an obj

retransmission in the terminal A 601 that t

count has not reached the upper limit of th

count and the lifetime unique to the data h

expired, Data 5-A is returned to the transm

in the transmission queue manager 106

another priority degree in the same termina

aggregation method, burst data transmission

for another terminal by a method other than

aggregation method, burst data transmission

for another priority degree in the same ter

method other than the aggregation method, Q

frame transmission which initiates downlink

transmission performed from a base station

terminal by the HCCA method of IEEE 802 lie

TXOP transmission performed by the HCCA met

802 lie, or data transmission performed by

method using CSMA/CA such as the DCF method

802 11 or the EDCA method of IEEE 802 lie

In this embodiment, as the method of s

retransmission, the Implicit Block Ack Requ

proposed in IEEE 802 Hn is used as a metho

increasing the efficiency of the Block Ack

standardized by IEEE 802 He This is the

omits a Block Ack Request frame which is ne

receive a Block Ack frame indicating the re

status of transmission data from terminal B

802 lie may also be used Also, in this em

the number of data to be aggregated is 4 fo

terminals A and B in the first frame exchan

and 3 for the both in the first retransmiss

However, the number of data to be aggregate

limit the form of use of this embodiment, s

of data to be aggregated can be variable or

the same for terminals A and B

Although an RTS frame and CTS frame ar

at the start of data transmission in this e

it is also possible to use a method in whic

frame and RAC frame are exchanged instead o

frame and CTS frame or terminal A transmits

frame, or to start aggregation frame transm

immediately after the data transmission rig

acquired without performing any frame excha

the RTS frame and the like In addition, a

frame is used as a method by which terminal

transmission period to terminal B, but it i

possible to use an IAC frame as in the firs

embodiment, or describe the type of the fir

plurality of aggregation frames are transmi

terminal A by burst transmission with an SI

or an interval shorter than that, and trans

plurality of aggregation frames from termin

the transmission period by burst transmissi

falls within the range of the given transmi

period In this case, however, terminal A

QoS Cf-PoIl frame which gives the transmiss

to the last aggregation frame of the plural

aggregation frames to be transmitted by bur

transmission, or places information which g

terminal B the transmission period in the l

aggregation frame

Alternatively, it is also possible to

control frame such as an acknowledgement fr

aggregation frame, and transmit an aggregat

formed by aggregating a plurality of data f

the control frame by burst transmission

As described above, for each transmiss

which cannot be retransmitted because the d

exceeded the upper limit of the retry count

data The transmission data is returned to

transmission queue in the transmission queu

106, if the data has exceeded the upper lim

retry count for each frame exchange sequenc

burst data, but the retry count uniquely ma

the transmission data has not exceeded the

of the retry count, and the lifetime unique

for the transmission data has not expired

retry count uniquely managed for the transm

has exceeded the upper limit of the retry c

lifetime uniquely managed for the transmiss

expired, the data is not returned to the tr

queue but discarded

In this embodiment as described above,

retransmission of burst data in burst trans

be limited for each frame exchange sequence

burst data, so scheduling calculations can

by taking account of the retransmission of

data It is also possible to secure necess

for different QoS requests from a plurality

terminals or a plurality of applications

whether to perform burst data retransmissio

bi-directional data flow method using a QoS

frame explained in the second embodiment, w

described below

In this embodiment, a method of limiti

retransmission by using the retry count for

exchange sequence of burst data as in the s

embodiment will be explained Note that al

retry count for each frame exchange sequenc

data is used in the retransmission limiting

this embodiment, it is also possible to use

lifetime instead of the retry count as in t

embodiment

When this embodiment is compared with

embodiment, transmission errors occur in da

transmitted by terminal A in the second emb

no such error occurs in this embodiment T

this embodiment differs from the second emb

the part of processing which determines whe

perform retransmission However, the rest

the same as the second embodiment, so the d

limiting method using the retry count for e

exchange sequence of burst data in a case i

no error occurs in transmission data from a

701 and transmission data from terminal B i

m burst transmission performed by the bi-d

data flow method using a QoS Cf-PoIl frame,

transmitted from terminal A and the data is

retransmitted from terminal B FIG 8 is a

explaining a retransmission limiting method

retry count for each frame exchange sequenc

data in a case in which if no error occurs

transmission data from terminal A and trans

from terminal B is generated in burst trans

performed by the bi-directional data flow m

a QoS Cf-PoIl frame, no new data is transmi

terminal A and the data is retransmitted fr

B

In this embodiment, the upper limit of

count for each frame sequence of burst data

burst data is retransmitted only once, as i

embodiment However, the upper limit of th

transmission/reception state manager 110 of

controller 103 of the terminal A 701 initia

retry count for each frame exchange sequenc

data (initializes the retry count to 0) I

transmitted by the terminal A 701 are norma

by a terminal B 702 in the first burst data

exchange sequence 703 performed by the bi-d

data flow method, a Block Ack frame 704 for

terminal B 702 indicates that Data 1-A, Dat

3-A, and Data 4-A transmitted by the termin

normally received The transmission/recept

manager 110 of the terminal A 701 having re

aggregation frame returned by the terminal

first burst data frame exchange sequence 70

from the Block Ack frame 704 that all the d

transmitted by the terminal A 701 are norma

and no retransmission is necessary Howeve

2-B and Data 3-B of Data 1-B, Data 2-B, Dat

Data 4-B transmitted by the terminal B 702

received, the transmission/reception state

of the terminal A 701 detects from a recept

of the burst data is necessary in order for

terminal B 702 to perform a retransmission

determines whether the first retransmission

burst data is possible as in the second emb

The transmission/reception state manag

counts up the retry count for each frame ex

sequence of the burst data from 0 to 1, and

whether the retry count has exceeded 2 as t

limit of the retry count for each frame exc

sequence of the burst data Since the retr

each frame exchange sequence of the burst d

exceeded 2 as the upper limit of the retry

first retransmission of the burst data is p

In a frame exchange sequence 705 for t

retransmission of the burst data, a data

transmitting/receiving method determination

the terminal A 701 determines a transmissio

be allocated to the terminal B 702 A fram

formation/transmission processor 111 notifi

transmission period to be allocated to the

702, which is determined by the data

new data Data 5-A, Data β-A, and Data 7-A t

transmitted to the terminal B 702, and tran

aggregation frame The terminal B 702 whic

the transmission period for retransmission

exchange sequence 705 for the first retrans

the burst data checks the retry count and l

each retransmission data as in the second e

aggregates, after a Block Ack frame, Data 2

3-B for each of which it is confirmed that

limit of the retry count is not reached and

lifetime has not expired, forms an aggregat

further aggregating new data Data 5-B, and

the aggregation frame to the terminal A 701

Then, after frame exchange is complete

frame exchange sequence 705 for the first

retransmission of the burst data, if the

transmission/reception state manager 110 of

terminal A 701 determines that the data tra

the terminal A 701 are normally received, t

errors occur in the data transmitted by the

702, and the second retransmission is neces

counts up the retry count for each frame ex

sequence of the burst data from 1 to 2, and

whether the retry limit has exceeded 2 as t

limit of the retry count for each frame exc

sequence of the burst data Since the retr

each frame exchange sequence of the burst d

to 2 as the upper limit of the retry count,

transmission/reception state manager 110 in

burst data retransmission process, interrup

data transmission /reception process by tran

Block Ack frame 708 when SIFS has elapsed a

frame exchange sequence 705 for the first

retransmission of the burst data, and advan

burst data frame exchange sequence 709 perf

another terminal by the bi-directional data

a QoS Cf-PoIl frame The operation after t

retransmission of the burst data is interru

limited to the burst data transmission/rece

process performed for another terminal by t

bi-directional data flow method using a QoS

frame, and it is also possible to advance t

aggregation method, QoS Cf-PoIl frame trans

which initiates downlink TXOP transmission

from a base station to a terminal by the HC

IEEE 802 lie or uplink TXOP transmission pe

the HCCA method of IEEE 802 lie, or data tr

performed by an access method using CSMA/CA

DCF method of IEEE 802 11 or the EDCA metho

802 lie

Also, as shown in FIG 8, in a case in

error occurs in transmission data of a term

which has initiated burst data transmission

bi-direction data flow method using a QoS C

frame, errors occur in only transmission da

terminal B 802, and there is no new transmi

from the terminal A 801, a retransmission p

performed to give a transmission period to

B 802 in order to retransmit the data which

transmitted from the terminal B 802 but is

received, this band allocation for retransm

also be performed by the retransmission lim

using the retry count for each frame exchan

transmission errors, a transmission/recepti

manager 110 of the terminal A 801 determine

perform a retransmission process for giving

terminal B 802 a transmission period for

retransmission If no new transmission dat

the terminal A 801 when the burst data retr

process is to be performed, after the first

frame exchange sequence 803 performed by th

bi-directional data flow method using a QoS

frame is completed, the terminal A 801 tran

aggregation frame formed by aggregating a B

frame 804 and a QoS Cf-PoIl frame 805 descr

transmission period to be allocated to the

802, and the terminal B 802 returns an aggr

frame formed by aggregating Data 2-B and Da

the retransmission data and Data 5-B as new

thereby performing a frame exchange sequenc

the first retransmission of the burst data

explained with reference to FIG 7, the

transmission/reception state manager 110 of

terminal A 801 can limit the retransmission

process by transmitting a Block Ack frame 8

has elapsed after the frame exchange sequen

the first retransmission of the burst data,

performing a frame exchange sequence 807 fo

retransmission of the burst data, and advan

burst data frame exchange sequence 809 perf

another terminal by the bi-directional data

using a QoS Cf-PoIl frame The operation a

retransmission of the burst data is interru

limited to the burst data transmission/rece

process performed for another terminal by t

bi-directional data flow method using a QoS

frame, and it is also possible to advance t

burst data transmission performed for anoth

degree in the same terminal by the aggregat

burst data transmission performed for anoth

by a method other than the aggregation meth

data transmission performed for another pri

in the same terminal by a method other than

aggregation method, QoS Cf-PoIl frame trans

which initiates downlink TXOP transmission

Although a method of limiting retransm

using the retry count for each frame exchan

of burst data is explained in this embodime

also possible to use the lifetime for each

exchange sequence of burst data as in the f

embodiment When this lifetime is used, if

remaining period of the lifetime for each f

exchange sequence of burst data is short, i

possible to use, when a retransmission proc

performed, a method by which an aggregation

formed by aggregating only the Block Ack fr

QoS Cf-PoIl frame 805 is transmitted withou

transmitting any new data from terminal A a

FIG 8, only a period during which data hav

reception error and required to be retransm

transmitted is given as the transmission pe

allocated to the terminal B 802, and an agg

frame formed by aggregating only the retran

data is returned

In this embodiment, as the method of s

retransmission, the Implicit Block Ack Requ

Block Ack method of IEEE 802 lie Since th

retransmission limiting method according to

embodiment can be used regardless of the me

selective retransmission, it is unnecessary

Implicit Block Ack Request method as in thi

embodiment, and the existing Block Ack meth

802 lie may also be used Also, in this em

the number of data to be aggregated is 4 fo

terminals A and B in the first frame exchan

and 3 for the both in the first retransmiss

However, the number of data to be aggregate

limit the form of use of this embodiment, s

of data to be aggregated can be variable or

the same for terminals A and B

Although an RTS frame and CTS frame ar

at the start of data transmission in this e

it is also possible to use a method in whic

frame and RAC frame are exchanged instead o

frame and CTS frame or terminal A transmits

frame, or to start aggregation frame transm

immediately after the data transmission rig

field of a Block Ack frame without aggregat

other frame

In this embodiment as described above,

no error occurs in transmission data of ter

an error occurs in only transmission data o

in data transmission/reception performed by

bi-directional data flow method, a retransm

can be allocated to terminal B, thereby red

process by which terminal B reacquires the

right for retransmission

Also, the retransmission of burst data

transmission can be limited for each frame

sequence of the burst data, so scheduling c

can be performed by taking account of the

retransmission of the burst data It is al

to secure necessary bands for different QoS

from a plurality of terminals or a pluralit

applications

Additional advantages and modification

readily occur to those skilled in the art

the invention in its broader aspects is not