Title of Invention

"APPARATUS AND METHOD FOR RE-TRANS MITTING ERRONEOUS PACKET DATA OF WIRELESS LOCAL LOOP"

Abstract There is disclosed an apparatus and method for re-transmitting erroneous packet data can reduce the data transmission delay resulting from the inter-layer movement of data generated during a re-transmission of erroneous data, and the transmission delay of packet data resulting from overhead time because the re-transmission of erroneous data is conducted by physical layers. Accordingly, it is possible to enable a rapid data transmission. This results in a reduction in the load of the WLL system, thereby allowing an improvement in reliance to be expected. Each of the physical layers includes a buffer 120 and 125, a timer 130 and 135, a controller 110 and 115, and a radio frequency unit 150 and 155.
Full Text 2
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an apparatus and method for re-transmitting erroneous packet data of a wireless local loop (WLL) , and more particularly to an apparatus and method for conducting re-transmission of erroneous packet data on a physical layer in a WLL.
Description of the Related Art
A system, which is used for data communications between open system interconnections (OSIs), is divided into 7 layers in terms of functional commonness and independency. For respective layers, necessary protocols are stipulated. In most of current wire and wireless communication systems, such OSI 7Layers are referenced.
OSI 7Layers include a physical layer (Layerl), a data_link layer (Layer2), a network layer (Layer3), a transport layer (Layer4), a session layer (Layer5), a presentation layer (Layer6), and an application layer (Layer7) .
Generally, transmission data is generated at an upper layer, for example, Layer7, Layer6, Layer5, or Layer4, and

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applied to a lowermost layer via intermediate layers. The transmission data from the lowermost layer is then transmitted to the lowermost layer "of the counterpart via a physical medium, that is, a line, so that it is finally transmitted to a desired intermediate or upper layer.
Conventionally, re-transmission of erroneous data is carried out at the data_link layer (Layer2) or transport layer (Layer4).
The re-transmission at the data_link layer (Layer2) is achieved using a Go-Back-N method or a Selective-Repeat method. The Go-Back-N method is a method in which in response to a negative acknowledgement (NAK) signal indicative of the fact that there is an error in transmission data, the transmission data is re-transmitted. On the other hand, in accordance with the Selective-Repeat method, only the erroneous data is retransmitted.
The re-transmission at the transport layer (Layer4) is achieved using TCP/IP. In accordance with this method, if there is no acknowledgement (ACK) signal, indicative of a normal reception of 8-Kbyte data, from the reception end, the 8-Kbyte data is re-transmitted from the transmission-end TCP/IP (Layer4).
A system for transmitting packet data may be of a circuit mode or of a packet mode in accordance with the transmission type of data. In the circuit mode system, a path is set between

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a transmission node and a reception node so that the path is exclusively used until the connection between the transmission and reception nodes is cut off.
In accordance with the packet mode system, data is transmitted in the form of packets each having a desired length. Accordingly, one line can be simultaneously used by a plurality of terminals without being exclusively used by one terminal. In the packet mode system, it is necessary to use overhead data, indicative of the destination of data and the start and end of data, for every packet. The data transmission time is increased by the overhead prefixed to each packet. The same problem is involved in the case in which re-transmission of data is made due to the generation of errors in packet data.

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SUMMARY OF THE INVENTION
Therefore, an object of the invention is to provide an apparatus and method for re-transmitting erroneous packet data of a WLL, which are capable of reducing the data transmission delay resulting from the inter-layer movement of data generated during a re-transmission of erroneous data, and the transmission delay of packet data resulting from overhead time, thereby improving the efficiency and speed of data transmission.
In accordance with one aspect, the present invention provides An apparatus for re-transmitting erroneous packet data in a wireless local loop,' comprising: a buffer for storing data transmitted, to prepare the data for an erroneous transmission of the data; a timer for limiting a time taken to wait for an acknowledgement to the transmission of the data; a controller

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for controlling the buffer and the timer to allow a data retransmission function to be carried out; and a radio frequency unit for transmitting packet data over the air under the condition in which the packet data is entrained in a radio frequency signal.
In accordance with another aspect, the present invention provides a method for re-transmitting erroneous packet data in a wireless local loop, comprising the steps of: (a) transmitting data while storing the data in a buffer; (b) operating a timer simultaneously with the transmission of the data, thereby counting a time taken to wait for an acknowledgement to the transmission of the data; and (c) if no acknowledgement signal is received until the operation of the timer is terminated or if a negative acknowledgement signal is received, then re-transmitting the data stored in the buffer ; said steps (a) to (c) being carried out in a physical layer.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description when taken in conjunction with the drawings, in which:
Fig. 1 is a block diagram illustrating a conventional procedure for re-transmitting erroneous packet data;
Fig. 2 is a block diagram illustrating a method for re-

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transmitting erroneous packet data in accordance with the present invention;
Fig. 3 is a block diagram illustrating the structure of a physical layer adapted to re-transmit erroneous packet data; and
Tig. 4 is a flow chart illustrating the method for retransmitting data erroneously transmitted, in accordance with the present invention.
Respective general functions of layers illustrated in Fig. 1, pertaining to a conventional procedure for re-transmitting erroneous packet data will be described hereinafter.
Transport layers 10 and 15 manage the quality of the communication network for transmission cf data. Each of network layers executes a desired routine using the communication network, and sets a connection to the counterpart system. Data_link layers 20 and 25 establish line links, detect transmission errors, and recover those transmission errors. Physical layers 30 and 35 control electrical and mechanical conditions to allow a physical connection of lines, and a

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maintenance and cut-off of that physical connection. The physical medium 40 is a wire or wireless transmission line for transmitting data signals received from the physical layers 30 and 35, In Fig. 1, network layers are not shown for the convenience of illustration. Also, the transport layers are denoted by "TCP/IP".
Now, the conventional re-transmission method for erroneous packet data will be described in conjunction with Fig. 1.
The transmission-end terminal (base station) of a WLL system generates data at its upper layer, and applies the generated data to Layerl 30 via Layer2 20. The data from Layerl 30 is transmitted to Layerl 35 of the reception-end terminal, and then sent to the upper layer of the reception-end terminal via the layers of the reception-end terminal.
The method for processing errors generated during the above transmission procedure may be varied, depending on the transmission control method used.
In accordance with a go-back-N method and a selective-repeat method, re-transmission of data is carried out by the data_link layers 20 and 25. When the data_link layer 20 is informed of the generation of errors from the reception end, it transmits again associated data stored in its buffer. This data is sent to the reception-end Layerl 35 via a wireless transmission line via Layerl 30. The data is finally

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transmitted to the reception-end data_link layer 25.
In accordance with the re-transmission method using TCP/IPs, the transports layers 10 and 15 carry out retransmission of data. When the transmission-end transport layer 10 is informed of the generation of errors from the reception end, it transmits again associated data stored in its buffer. This data is then sent to the reception-end Layerl 35 via Layer3, Layer2 20, Layerl 30, and a wire transmission line. Finally, the data is transmitted to the reception-end transport layer 15 via the reception-end Layer2 25 and Layer3.
Packet data, which is transmitted as mentioned above; is added with overhead data at its leading and trailing ends, respectively. The overhead data added to the leading end of the packet data contains information about synchronization and destination address, etc. The overhead data added to the trailing end of the packet data contains information about the detection and correction of errors generated during the transmission of data. For example, where data is transmitted for 5 to 107 ms, the leading and trailing overheads take transmission times' of 60 ms and 20 ms, respectively. Thus, the time taken to transmit the overheads in the packet mode is substantially equal to the transmission time of data associated with those overheads. For this reason, the delay of transmission resulting from the overhead time is importantly treated in the go-back-N method and the TCP/IP re-transmission

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method inevitably involving the re-transmission of a frame with a certain size or at a certain interval, as compared to the selective repeat method adapted to re-transmit a particular frame involving errors.
Furthermore, the re-transmission of data is not requested until erroneous data reaches the upper layer because it is carried out by the upper layer. For this reason, loss of time is inevitably involved.
Fig. 2 is a block diagram illustrating a method for retransmitting erroneous packet data in accordance with the present invention. Fig. 3 is a block diagram illustrating the structure of a physical layer adapted to re-transmit erroneous packet data.
The functions and operations of respective layers illustrated in Fig. 2 are the same as those of the conventional case illustrated in Fig. 1. In accordance with the present invention, however, the re-transmission of erroneous data is carried out by physical layers 30 and 35, as compared to the conventional case in which the re-transmission of erroneous data is carried out transport layers 10 and 20 or data_link layers 20 and 25. As shown in Fig. 3, the physical layer 30 includes a controller 110, a buffer 120, a timer 130, and a

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radio frequency unit 150. In similar, the physical layer 145 includes a controller 115, a buffer 125, a timer 135, and a radio frequency unit 155.
Each of the buffers 120 and 125 serves to temporarily store data transmitted. Data stored in each of the buffers 120 and 125 has the form of a final data frame capable of being transmitted on a transmission line without any processing.
Each of the timers 130 and 135 is a time counter adapted to limit the time, for which the transmission end waits for an acknowledgement to a transmission of data after the data transmission is made.
The controllers 110 and 115 control respective buffers 120 and 125, and respective timers 130 and 135, in order to enable functions required for transmission of data to be carried out.
Each of the radio frequency units 150 and 155 serves to transmit packet data over the air under the condition in which the packet data is entrained in a signal of a desired radio frequency.
Fig. 4 is a flow chart illustrating the method for retransmitting data erroneously transmitted, in accordance with the present invention.
The base station 100 and terminal 200 of the WLL system illustrated in Fig. 3 may serve as a transmission end and a reception end, respectively, and vice versa. Since these base

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station and terminal have the same function, they are referred to as a transmission end and a reception end, respectively, for the convenience of description.
Data generated from an upper layer included in a transmission-end data transmitting unit, that is, Layer4, Layer5, Layer6, or Layer7, is applied to the physical layers 140 and 145 via Layer3 and Layer2. The data is transmitted over the air via respective radio frequency units 150 and 155 after being processed in accordance with a desired transmission procedure conducted by the physical layers 140 and 145.
Now, a preferred embodiment of the present invention will be described in conjunction with Fig. 4.
Data generated from an upper layer, that is, Layer4, Layer5, Layer6, or Layer7, is stored in the buffers 120 and 125 before its transmission (Step S10). In response to the data storage, the timers 130 and 135 begin to operate (Step S20) . Each of the timers 130 and 135 is adapted to limit the time, for which the transmission end waits for an acknowledgement to a transmission of data after the data transmission is made, when an abnormal transmission of data is made.
Once the timers 130 and 135 operate, the controllers 110 and 115 check whether or not an acknowledgement signal corresponding to "ACK (Acknowledgement)" or "NAK (Negative Acknowledgement}" is received (Step S30). When no acknowledgement signal is received, the controllers 110 and 115

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repeatedly conduct the checking procedure until the operations of the timers 130 and 135 are terminated. (Step S40). When the acknowledgement signal is received before the operations of the timers 130 and 135 are terminated, these operations of the timers 130 and 135 are forcedly terminated.
Where the acknowledgement signal corresponds to "ACK" the above procedure is terminated without any re-transmission of data.
On the other hand, where the acknowledgement signal corresponds to "NAK", the controllers 110 and 115 re-transmit associated data stored in the buffers 120 and 125, respectively (Steps S50 and S60) .
If the timers 130 and 135 terminate before no acknowledgement signal is received, the associated data stored in the buffers 120 and 125 is re-transmitted, as in the case in which the acknowledgement signal corresponding to "NAK" is received (Step S60). The re-transmission procedure is repeated until the acknowledgement signal corresponding to "ACK" is received
As apparent from the above description, the apparatus and method for re-transmitting erroneous packet data in accordance with the present invention can reduce the data transmission delay resulting from the inter-layer movement of data generated during a re-transmission of erroneous data, and the transmission delay of packet data resulting from overhead time

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because the re-transmission of erroneous data is conducted by the lowermost layers, that is, the physical layers 140 and 145, as compared to the case in which the re-transmission of erroneous data is conducted by upper layers such as TCP/IP layers or data_link layers. Accordingly, it is possible to enable a rapid data transmission. This results in a reduction in the load of the WLL system, thereby allowing an improvement in reliance to be expected.
Although the preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

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WE CLAIM:
1. An apparatus for re-transmitting erroneous packet data
in a wireless local loop, comprising:
a buffer for storing data transmitted, to prepare the data for an erroneous transmission of the data;
a timer for limiting a time taken to wait for an acknowledgement to the transmission of the data;
a controller for controlling the buffer and the timer to allow a data re-transmission function to be carried out; and
a radio frequency unit for transmitting packet data over the air under the condition in which the packet data is entrained in a radio frequency signal.
2. The apparatus according to claim 1, wherein the
buffer, the timer, the controller, and the radio frequency unit
operate in a physical layer.
3. The apparatus according to claim 1, wherein the buffer
is adapted to store a final data frame.
4. The apparatus according to claim 1, wherein the
controller is adapted to transmit only data involving errors.
5. A method for re-transmitting erroneous packet data in
13

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a wireless local loop, comprising the steps of:
(a) transmitting data while storing the data in a buffer;
(B) operating a timer simultaneously with the transmission of the data, thereby counting a time taken to wait for an acknowledgement to the transmission of the data; and
(c) if no acknowledgement signal is received until the operation of the timer is terminated or if a negative acknowledgement signal is received, then re-transmitting the data stored in the buffer.
said steps (a) to (c) being carried out in a physical layer.
6. The method according to claim 5, wherein the step (c)
comprises the steps of:
if an acknowledgement signal is received, then terminating the re-transmission procedure; and
if no acknowledgement signal is received, then repeatedly checking whether or not the acknowledgement signal is received, until the operation of the timer is terminated.
7. The method according to claim 5, wherein the steps (b) and (c) are repeatedly carried out • until the acknowledgement signal is received.
8. The method according to claim 5, wherein the buffer is adapted to store a final data frame.

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9. The method according to claim 5, wherein the data re-transmission is made only for data involving errors.
10. An apparatus for re-transmitting erroneous packet data in a wireless local loop, substantially as herein described, particularly with reference to the accompanying drawings.
11. A method for re-transmitting erroneous packet data in a wireless local loop, substantially as herein described, particularly with reference to the accompanying drawings.
There is disclosed an apparatus and method for re-transmitting erroneous packet data can reduce the data transmission delay resulting from the inter-layer movement of data generated during a re-transmission of erroneous data, and the transmission delay of packet data resulting from overhead time because the re-transmission of erroneous data is conducted by physical layers. Accordingly, it is possible to enable a rapid data transmission. This results in a reduction in the load of the WLL system, thereby allowing an improvement in reliance to be expected. Each of the physical layers includes a buffer 120 and 125, a timer 130 and 135, a controller 110 and 115, and a radio frequency unit 150 and 155.

Documents:

00138-cal-2001-abstract.pdf

00138-cal-2001-assignment.pdf

00138-cal-2001-claims.pdf

00138-cal-2001-correspondence.pdf

00138-cal-2001-description(complete).pdf

00138-cal-2001-drawings.pdf

00138-cal-2001-form-1.pdf

00138-cal-2001-form-18.pdf

00138-cal-2001-form-2.pdf

00138-cal-2001-form-3.pdf

00138-cal-2001-form-5.pdf

00138-cal-2001-g.p.a.pdf

00138-cal-2001-letters patent.pdf

00138-cal-2001-priority document others.pdf

00138-cal-2001-priority document.pdf

138-CAL-2001-FORM 15.pdf

138-cal-2001-granted-abstract.pdf

138-cal-2001-granted-assignment.pdf

138-cal-2001-granted-claims.pdf

138-cal-2001-granted-correspondence.pdf

138-cal-2001-granted-description (complete).pdf

138-cal-2001-granted-drawings.pdf

138-cal-2001-granted-examination report.pdf

138-cal-2001-granted-form 1.pdf

138-cal-2001-granted-form 18.pdf

138-cal-2001-granted-form 2.pdf

138-cal-2001-granted-form 3.pdf

138-cal-2001-granted-form 5.pdf

138-cal-2001-granted-gpa.pdf

138-cal-2001-granted-letter patent.pdf

138-cal-2001-granted-priority document.pdf

138-cal-2001-granted-reply to examination report.pdf

138-cal-2001-granted-specification.pdf

138-cal-2001-granted-translated copy of priority document.pdf


Patent Number 201366
Indian Patent Application Number 138/CAL/2001
PG Journal Number 07/2007
Publication Date 16-Feb-2007
Grant Date 16-Feb-2007
Date of Filing 07-Mar-2001
Name of Patentee LG ELECTRONICS INC
Applicant Address 20 ,YOIDO-DONG ,YONGDUNGPO-KU , SEOUL
Inventors:
# Inventor's Name Inventor's Address
1 KIM BO KYUNG LG VILLAT 104 ,659-2,IL-DONG ANYANG , KYUNGKI-DO
PCT International Classification Number G 06F 11/14
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 11670/2000 2000-03-09 Republic of Korea