KR20100061277A - Correction method for uplink packet transmission time, transmission method for uplink - Google Patents

Abstract

PURPOSE: A method and a device for correcting a transmission point of an uplink packet are provided to minimize the interference among symbols by correcting the transmission point of an uplink packet. CONSTITUTION: A ranging receiver(123) receives a ranging packet. A delay measuring unit(124) confirms the delay time of the ranging packet by comparing the time of the reception of the ranging packet with the base station symbol synchronous signal. A controller(126) sets the correction time of the uplink packet transmission point by checking the delay time. The uplink packet is set to arrive after a first section from the starting point of a cyclic prefix section by the correction fading. The first section is decided in consideration of the maximum transmission speed of the mobile station and the cycle of the cyclic ranging.

Description

Method and apparatus for correcting uplink packet transmission point {CORRECTION METHOD FOR UPLINK PACKET TRANSMISSION TIME, TRANSMISSION METHOD FOR UPLINK}

The present invention relates to a correction method and apparatus at the time of uplink packet transmission.

The present invention is derived from the research conducted as part of the IT growth engine technology development of the Ministry of Knowledge Economy and the Ministry of Information and Telecommunication Research and Development. System development].

In case of using Time Division Duplexing (TDD) in a wireless communication system, for example, an orthogonal frequency division multiplexing (OFDM) system, a frame is downlinked to enable bidirectional communication. It is divided into a downlink section and an uplink section.

In the downlink period, the base station transmits packets to a plurality of mobile stations based on the same time, but in the uplink, since a plurality of mobile stations transmit packets to the base station, each signal arrives differently, resulting in a propagation delay. Inter symbol interference (ISI) may occur. Therefore, ranging is required to perform separate synchronization in consideration of the symbol synchronization signal of the base station with respect to the packet transmission time of a plurality of mobile stations.

On the other hand, packets transmitted by different mobile stations may be transmitted along different paths, where radio waves are multi-reflected to interact with each other. This is called multipath fading. According to a multipath environment, a delay profile due to multipath fading is changed, and thus, it is necessary to set a transmission time point so that a packet arrives before a predetermined time.

In addition, when the distance between the base station and the mobile station is reduced due to the high speed movement of the mobile station, the packet may arrive at the base station before the symbol synchronization signal of the mobile station. This also causes intersymbol interference.

The technical problem to be achieved by the present invention is to correct the transmission time of the uplink packet to minimize the inter-symbol interference in consideration of the multi-path fading and the high-speed movement of the mobile station.

According to an embodiment of the present invention, a method for calibrating an uplink packet transmission time point in a base station includes receiving a ranging packet from a mobile station, measuring a delay time of the ranging packet from a reception time point of the ranging packet, Determining a correction section located after the first section from a start point of the cyclic prefix section; setting a correction time at the time of transmitting the uplink packet based on the delay time and the correction section; and Sending a ranging response message including information about the mobile station to the mobile station.

The measuring may include comparing the start time of the ranging packet with a symbol synchronization signal of the base station and measuring the delay time.

The setting may include setting the correction time so that an uplink packet arrives at the base station in the correction period.

The determining may further include determining the correction section in consideration of the period of periodic ranging and the maximum moving speed of the mobile station.

The length of the first interval may be determined by dividing a value obtained by multiplying a period of periodic ranging by a maximum moving speed of the mobile station by the speed of light.

The correction section may be located before a time in which a second section and the first section are combined from an end point of the cyclic prefix section.

The determining may include determining the second interval in consideration of a delay profile due to multipath fading.

The length of the second interval may be equal to or longer than the delay profile due to multipath fading.

According to another embodiment of the present invention, an apparatus for correcting an uplink packet transmission time includes a ranging receiver for receiving a ranging packet, a delay time of the ranging packet by comparing a reception time of the ranging packet with a base station symbol synchronization signal. A delay measuring unit for checking the delay time, and a controller configured to set a correction time at an uplink packet transmission point, wherein the correction time arrives after the first interval from the start point of the cyclic prefix period. Is set to.

The first interval may be determined in consideration of the period of the periodic ranging and the maximum moving speed of the mobile station.

The length of the first interval may be determined as a value obtained by multiplying the time interval of the periodic ranging by the maximum moving speed of the mobile station by the speed of light.

The correction time may be determined such that the uplink packet arrives from the end time of the cyclic prefix period before the sum of the second interval and the first interval.

The second interval may be determined in consideration of a delay profile due to multipath fading.

The length of the second interval may be equal to or longer than the delay profile.

According to the present invention, in the orthogonal frequency division multiplexing system, the transmission time of the uplink packet is corrected to minimize the inter-symbol interference, thereby ensuring reliability when the base station receives the uplink packet.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “module”, etc. described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. have.

In this specification, a mobile station (MS) includes a terminal, a mobile terminal (MT), a subscriber station (SS), a portable subscriber station (PSS), and a user equipment. It may also refer to a user equipment (UE), an access terminal (AT), and the like, and may include all or some functions of a terminal, a mobile terminal, a subscriber station, a portable subscriber station, a user device, an access terminal, and the like.

In the present specification, a base station (BS) is a base station (BS), an access point (Access Point, AP), a radio access station (Radio Access Station, RAS), a Node B (Node B), an advanced Node B. (evolved NodeB, eNodeB), Base Transceiver Station (BTS), Mobile Multihop Relay (MMR) -BS, etc. may be referred to as an access point, a wireless access station, Node B, eNodeB, a base transceiver station, MMR-BS It may also include all or part of the function.

A method of correcting a transmission time of an uplink packet will now be described in accordance with an embodiment of the present invention with reference to the drawings.

1 is a diagram illustrating a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 1, a wireless communication system includes a mobile station 110 and a base station 120.

The mobile station 110 is an end point of a wireless channel and accesses the base station 120 using a transmission / reception function and a medium access control (MAC) processing function according to a wireless access system of a wireless communication system, for example, a portable Internet system. High speed packet data is transmitted and received.

The base station 120 receives a radio signal from the mobile station 110 and transmits the radio signal to a control station (not shown) or converts data received from the control station into a radio signal and transmits the radio signal to the mobile station 110. Initial access, inter-sector handover control, and quality of service (QoS) control.

The base station 120 includes an uplink packet transmission time correction apparatus, and the uplink packet transmission time correction apparatus includes an antenna 121, a signal converter 122, a ranging receiver 123, a delay measuring unit 124, and The control unit 126 is included.

Antenna 121 receives the uplink packet directly from mobile station 110.

The signal converter 122 converts an uplink packet having a radio frequency (RF) form into an intermediate frequency (IF).

The ranging receiver 123 informs the controller 126 whether the ranging packet is received. The delay measuring unit 124 measures the delay time of the ranging packet from the base station symbol synchronization signal and the arrival time of the ranging packet and informs the controller 126.

The controller 126 sets the uplink packet transmission time correction time according to the information about the delay time from the delay measuring unit 124.

A method of correcting an uplink packet transmission time will now be described in detail with reference to FIGS. 2 and 3.

2 is a diagram illustrating a frame structure of a wireless communication system according to an embodiment of the present invention, and FIG. 3 is a diagram illustrating a method of correcting an uplink packet transmission time according to an embodiment of the present invention.

According to FIG. 2, one frame Tf includes a downlink section DL and an uplink section. The frame Tf may further include a transmit / receive transition gap (TGT) between the downlink period DL and the uplink period UL, and may also receive / receive at the end of the frame Tf. The transmission transition interval (receive / transmit transition gap, RTG) may further include.

The downlink section DL includes a preamble and a downlink data section, the preamble includes one symbol Ts, and the downlink data section includes a plurality of symbols Ts. The uplink section UL includes an uplink data section including a plurality of symbols Ts, and a part of the uplink data section is used as a control section for performing ranging and the like.

Referring to FIG. 3, one symbol Ts includes a cyclic prefix section Tcp and a data section Td. The cyclic prefix period Tcp is a guard period for preventing inter symbol interference (ISI), and the data period Td is a period for transmitting valid data. The symbol Ts is transmitted and received in synchronization with the base station symbol synchronization signal Bsync.

The ranging packet rp1 transmitted by any one mobile station 110 of the plurality of mobile stations 110 is delayed by D1 compared to the base station symbol synchronization signal Bsync, and the ranging packet transmitted by another mobile station 110. (rp2) is delayed by D2 compared to the base station symbol synchronization signal (Bsync). The control unit 126 of the base station 120 considers the delay times D1 and D2 of the ranging packets rp1 and rp2 so that the uplink packet transmitted by the mobile station 110 arrives at the correction interval Pa. Set a correction time at the time of link packet transmission.

The correction section Pa is a part of the cyclic prefix section Tcp, is spaced apart from the start point of the cyclic prefix section Tcp by the first section Pb, and the first section (P) from the end point of the cyclic prefix section Tcp. Pb) and the second section Pc are separated by the combined length. The first interval Pb is a value considering high-speed movement of the mobile station 110, and the second interval Pc is a value considering a delay profile due to multipath fading.

Ranging is a task of separately synchronizing in order to receive packets transmitted from each mobile station 110 without interference from each other by the base station 120, and the internal synchronization signal of each mobile station 110 is transmitted to the base station 120. Initial ranging to match the synchronization signal of the (initial ranging) and the mobile station 110 is divided into periodic ranging (periodic ranging) that is periodically sent to the base station 120 for synchronization tracking. When the mobile station 110 moves, continuous synchronization is achieved by periodic ranging. However, when the mobile station 110 moves at a high speed, a change in delay time of an uplink packet may occur. Then, an uplink packet arriving at the base station 120 before the symbol synchronization signal Bsync of the base station 120 may be generated before recalibration by periodic ranging, which causes interference between symbols. As shown in an embodiment of the present invention, if the uplink packet arrives after the first interval Pb from the time point at which the cyclic prefix period Tcp starts, inter-symbol interference occurs due to the high-speed movement of the mobile station 110. You can prevent it. The first section Pb may be represented by Equation 1 below.

[Equation 1]

Where Vmax is the maximum travel speed of the mobile station, C is the speed of light and Δt is the period of periodic ranging.

Meanwhile, uplink packets transmitted from the mobile station 110 may arrive at the base station 120 along different paths, and multipath fading occurs when the radio waves received along the other paths are multi-reflected to interact with each other. do. However, considering the delay profile due to multipath fading as in the present invention, if the packet arrives at least before the second interval Pc from the end of the cyclic prefix period Tcp, the intersymbol interference due to the multipath fading. This can be prevented from occurring. On the other hand, the delay profile is determined according to the multipath environment.

In addition, in order to consider the periodic ranging period according to the movement of the mobile station 110, from the start point of the second section Pc before the first section Pb described above, that is, the end point of the cyclic prefix section Tcp. To allow the uplink packet to arrive by the length of the first and second intervals Pb and Pc.

Now, a method of correcting an uplink packet transmission time according to an embodiment of the present invention will be described in detail with reference to FIG. 4.

4 is a flowchart illustrating a method of correcting an uplink packet transmission time according to an embodiment of the present invention.

Referring to FIG. 4, the ranging receiver 123 of the base station 120 receives the ranging packet (S401), and the delay measuring unit 124 receives the symbol synchronization signal Bsync and the ranging packet of the base station 120. The delay time of the ranging packet is measured by comparing the reception time points (S402). Then, the information on the delay time of the ranging packet, that is, the ranging message is transmitted to the controller 126 (S403). Then, the controller 126 receives the ranging message (S404), and determines the ranging request according to the delay time of the ranging packet (S405). When it is determined that there is no ranging request, the controller 126 does not perform any operation and when it is determined that there is a ranging request, the controller 126 checks the delay time (S406). Thereafter, the controller 126 sets the first period Pa according to [Equation 1] and the delay profile described above to set the correction time at the time of transmitting the uplink packet (S407). Subsequently, the ranging response message including the transmission correction time information of the uplink packet is transmitted to the mobile station 110 (S408).

Thereafter, the mobile station 110 receives the ranging response message and adjusts the transmission time of the uplink packet of the mobile station 110 using the correction time information included therein to transmit the uplink packet. Thus, the base station 120 can receive uplink packets transmitted from all mobile stations 110 without interference or collision.

The embodiments of the present invention described above are not only implemented through the apparatus and the method, but may be implemented through a program for realizing a function corresponding to the configuration of the embodiments of the present invention or a recording medium on which the program is recorded.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a diagram illustrating a wireless communication system according to an embodiment of the present invention.

2 is a diagram illustrating a frame structure of a wireless communication system according to an embodiment of the present invention.

3 is a diagram illustrating an uplink packet transmission time correction method according to an embodiment of the present invention.

4 is a flowchart illustrating a method of correcting an uplink packet transmission time according to an embodiment of the present invention.

Claims (14)

A method for correcting an uplink packet transmission timing in a base station, Receiving a ranging packet from a mobile station, Measuring a delay time of the ranging packet from a reception time point of the ranging packet, Determining a correction section located after the first section from the start of the cyclic prefix section; Setting a correction time at the time of transmitting the uplink packet based on the delay time and the correction period; and Transmitting a ranging response message including information on the correction time to the mobile station; Correction method at the time of transmitting the uplink packet comprising a. In claim 1, The measuring step, And comparing the start time of the ranging packet with the symbol synchronization signal of the base station and measuring the delay time. In claim 1, The setting step, And setting the correction time so that an uplink packet arrives at the base station in the correction period. In claim 1, The determining step, And determining the correction interval in consideration of the period of periodic ranging and the maximum moving speed of the mobile station. In claim 1, And a length of the first interval is determined by dividing a value obtained by multiplying a period of periodic ranging by a maximum moving speed of the mobile station by the speed of light. In claim 1, And the correction section is located at the time of transmitting an uplink packet located before a time in which a second section and the first section are combined from an end point of the cyclic prefix section. In claim 6, The determining step, And determining the second interval in consideration of a delay profile due to multipath fading. In claim 6, And a length of the second interval is equal to or longer than a delay profile due to multipath fading. A ranging receiver for receiving a ranging packet, A delay measuring unit for checking a delay time of the ranging packet by comparing a reception time of the ranging packet with a base station symbol synchronization signal, and A controller configured to set the correction time at the time of transmitting an uplink packet by checking the delay time Including, The correction time is set such that the uplink packet arrives after the first interval from the start of the cyclic prefix interval. Correction apparatus at the time of uplink packet transmission. The method of claim 9, And the first interval is determined in consideration of a period of periodic ranging and a maximum moving speed of the mobile station. In claim 10, And a length of the first interval is determined by dividing a value obtained by multiplying the time interval of the periodic ranging by the maximum moving speed of the mobile station by the speed of light. In claim 10, And the correction time is determined so that the uplink packet arrives from the end time of the cyclic prefix section before the time in which the second interval and the first interval are combined. In claim 12, And a second interval is determined in consideration of a delay profile due to multipath fading. The method of claim 13, And a length of the second interval is equal to or longer than the delay profile.

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