KR20080069814A - Method and apparatus for determining a traffic transmitting timing in a mobile communication system - Google Patents

Abstract

A method for determining traffic transmitting timing in a mobile communication system and an apparatus therefor are provided to receive a frame safely within the maximum permission arrival time even though a transmitting time is variable, and to reduce production costs because of no need of GPS device. A method for determining a traffic transmitting timing in a mobile communication system includes the steps of transmitting a traffic frame through a forward link(502); receiving the traffic frame transmitted from a base station via a reverse link and receiving time information measured in the base station(504); determining whether the present step is the initial offset adjustment or not(506); if so in the step of 506, calculating an offset value by the received time information(508); if not so in the step of 506, determining whether the offset adjustment is activated or not, and the timing of the present offset adjustment is adequate or not with reference to the present system setup(510); if so in the step of 510, returning to the step of 508; changing the designation of the transmitting timing of the forward traffic frame by reflecting the offset value(512); transmitting the traffic frame at the designated timing(514); and if not in the step of 510, returning to the step of 514.

Description

METHOD AND APPARATUS FOR DETERMINING A TRAFFIC TRANSMITTING TIMING IN A MOBILE COMMUNICATION SYSTEM}

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

2 is a diagram showing the internal configuration of the base station and control station shown in FIG. 1 according to an embodiment of the present invention.

3 is a diagram illustrating a process of determining, when a control station transmits a forward traffic frame to a base station according to an embodiment of the present invention.

4 is a table showing a result of adjusting a next traffic frame transmission time based on a previous frame reception time received from a base station according to an embodiment of the present invention.

5 is a flowchart illustrating a forward traffic frame transmission process at a control station according to an embodiment of the present invention.

6 is a flowchart illustrating traffic frame processing at a base station according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

102, 220: control station 104a, 104b: relay line

106a, 106b, 202: base station 108a, 108b, 108c: mobile station

110, 234: GPS satellites 112a, 112b, 218: GPS antenna

208: reception time measurement device 216: reception time transmission device

226: transmission timing adjusting device 232: offset determining device

The present invention relates to a method and apparatus for determining a time point for transmitting a traffic frame through exchange of feedback information between mobile communication system devices.

In general, a mobile communication system includes a mobile station, a base transceiver station (BTS) and a control station (BSC), and the base station is connected to the control station by an E1 or T1 relay line. The base station is located between the mobile station and the control station, connects a call channel through a wireless link with the mobile station, and performs call control and maintenance functions for the mobile station. The control station performs control processing for the plurality of base stations and simultaneously connects with various external wired and wireless networks in cooperation with the switching station. The control station also performs the state management and radio resource management functions of the base station, and performs the soft handoff function between the base stations. When a call is attempted from a mobile station, data from the mobile station, such as voice, SMS data, etc., is transmitted over the radio link to the channel device of the base station. Then, the channel device of the base station transmits the received data to the selector device of the control station in the reverse direction through the relay line connected to the base station. In addition, in the case of the forward signal, the selector device of the control station receives the data transmitted from the external network via the switching station, and transmits the data to the channel device of the base station in the forward direction through the relay line connected to the control station, The channel device of the base station transmits the received data to the mobile station through a wireless link.

As such, since data is transmitted and received through the relay line between the base station and the control station, time synchronization is required for the transmission and reception of such data. In this regard, the base station and the control station each have a GPS receiver capable of receiving a GPS satellite signal, and it is common to adjust time synchronization for data transmission and reception using a clock signal obtained from the received GPS signal.

In more detail with respect to the transmission and reception of traffic frames between the base station and the control station of the mobile communication system, the transmission of the traffic frame is a predetermined time period, for example, in the case of the CDMA system, the transmission of the traffic frame is every 20msec. In addition, in order to prevent inter-signal interference to and from each mobile station belonging to the same sector of the base station and to increase the capacity of each base station sector, transmission and reception of traffic frames for each mobile station are performed at different time intervals. In this way, each traffic frame is transmitted and received by a predetermined frame period at a time that is distorted from the system time by a predetermined time, and a frame offset is an integer value indicating how much time the corresponding traffic frame is transmitted or received is distorted from the system time. Say In the case of a CDMA system, since the frame offset is represented by 4 bits, up to 16 frames may be provided, and up to 16 frame offsets may exist at intervals of 1.25 msec within a frame transmission period of 20 msec.

The base station receives the traffic frame from the control station, then performs certain processing and then sends the traffic frame back to the mobile station over the radio link. With this in mind, the base station must receive a traffic frame from the control station at least several msec before transmitting the data frame over the radio link (in this specification, the base station must receive the traffic frame in order to process the traffic frame within that period). The final point in time at which a traffic frame should be received is called the "maximum allowed arrival time"). For this purpose, the control station should appropriately determine the timing of transmitting the traffic frame to the base station in consideration of the transmission time of the base station for each traffic frame. That is, the time point at which the traffic frame is transmitted from the control station to the base station depends on the frame offset.

In fact, since the traffic frame transmission and reception between the control station and the base station is performed through the relay line having a limited bandwidth, the transmission delay of the traffic frame transmission and reception may be variable according to load variation or handoff occurrence of the relay line. In this situation where the transmission delay is variable, a situation may occur in which the base station cannot receive a traffic frame within the maximum allowable arrival time even if the transmission from the control station is made at the correct time. Similarly, even if the correct transmission is made by the control station, the base station may receive two or more traffic frames within the maximum allowed arrival time.

If the base station does not receive any traffic frames until the maximum allowed arrival time within any frame period, the base station transmits a null frame that contains no data during radio transmission in that frame period, and the mobile station " "Im missing" phenomenon. In addition, due to the reduction of the transmission delay, when the base station receives two traffics within the maximum allowable arrival time within an arbitrary frame period, a discarded frame occurs because the base station cannot process one of them. do.

Accordingly, there is a need for a method and apparatus that can dynamically perform an appropriate time point of traffic frame transmission between a base station and a control station in consideration of a transmission delay.

Accordingly, an object of the present invention is to provide a method and apparatus for dynamically finding an appropriate time point of traffic frame transmission between mobile communication system devices through exchange of feedback information.

According to one aspect of the invention, a method is provided for a transmitting station in a mobile communication system to determine when to send traffic. According to the method, the transmitting station transmits the traffic, and receives from the receiving station a measurement of the time that the traffic was received at the receiving station. Then, an offset for adjusting the traffic transmission time point is calculated from the received measurement value, and the traffic transmission time point is adjusted based on the calculated offset.

According to still another feature of the present invention, a control station for determining forward traffic transmission timing through exchange of forward and reverse traffic is provided without depending on the GPS signal receiving apparatus.

According to an embodiment of the present invention, the control station acquires the information of the traffic reception time measured by the base station from the signal receiving apparatus for receiving the reverse traffic and the received reverse traffic, and the next forward transmission traffic by the obtained traffic And a reverse traffic processor including an offset determination device for determining an offset for the target. The control station also includes a forward traffic processor including a signal transmission device for transmitting forward traffic and a transmission time adjustment device for adjusting a transmission time of the forward traffic.

According to still another aspect of the present invention, a forward traffic processor including a signal reception device for receiving forward traffic, a reception time measurement device for measuring a time at which the received forward traffic is received, and a signal transmission device for transmitting reverse traffic And a reverse traffic processor including a reception time transmission apparatus including a measurement value of the received time in the reverse traffic.

The present invention will be described in detail with reference to the accompanying drawings. In the following description, the case where the control station transmits a traffic frame to the base station in the forward link will be described. However, it should be noted that the present invention can be applied to the reverse link. In the following description, detailed descriptions of well-known functions and configurations will be omitted when the gist of the present invention may be unnecessarily obscured.

1 is a diagram schematically illustrating a mobile communication system according to an embodiment of the present invention. As shown in FIG. 1, the mobile communication system 100 establishes a radio link and a base station 106a, 106b, respectively, connected to the control station 102 by a control station 102, an E1 or T1 relay line 104a, 104b. Mobile stations 108a, 108b, 108c and GPS satellites 110 that connect to the base stations 106a, 106b via a network.

Each mobile station 108a, 108b, 108c performs traffic frame transmission and reception with the base stations 106a, 106b over a wireless link. As the mobile stations 108a, 108b, and 108c move, handoff may occur between base stations. As shown, the mobile station 108a is in a soft handoff state and is currently present to both the base stations 106a and the base station 106b. Connected. Each base station 106a, 106b is located between each mobile station 108a, 108b, 108c and the control station 102, for each mobile station 108a, 108b, 108c via the radio link interface, and the control station 102. ), The traffic frame is transmitted and received through the relay lines 104a and 104b. The control station 102 performs control of each base station 106a and 106b and a soft handoff function between the base stations 106a and 106b, and simultaneously performs connection with various wired and wireless networks in cooperation with an exchange station (not shown). . The GPS satellite 110 transmits the GPS time determined by the internal atomic clock to each base station 106a or 106b. Note that the control station 102 does not receive GPS signals. Base stations 106a and 106b have GPS receive antennas 112a and 112b, respectively, to receive GPS signals.

2 is a diagram showing the internal configuration of the base station and control station shown in FIG. 1 according to an embodiment of the present invention. Although only one base station is shown in the figure as being connected to the control station, it should be noted that a larger number of base stations can be connected to the control station. In addition, it should be noted that, except for essential components for explaining the present invention, illustration and description of other components are omitted so as not to unnecessarily obscure the subject matter of the present invention.

The base station 202 includes a GPS receiver 204, a forward traffic processor 206, and a reverse traffic processor 212 therein. The GPS receiver 204 obtains accurate time information by the signal received from the GPS satellite 234 via the GPS antenna 218 and provides a clock signal to each device in the base station. The forward traffic processor 206 measures the signal reception device 208 that receives the traffic frame transmitted from the control station 220 by the forward link, and the reception time for the received traffic frame, and transmits the measured time information to the reverse traffic. It includes a reception time measuring device 210 for transmitting to the processing unit 212. The reverse traffic processing unit 212 transmits the reception time measured by the signal transmission device 214 and the reception time measurement device 210 for transmitting the data received through the radio link to the control station 220 by the reverse link. It includes the reception time transmission device 216 to include and transmit.

The control station 220 includes a forward traffic processor 222 and a reverse traffic processor 228 therein. The forward traffic processor 222 includes a signal transmission device 224 for transmitting traffic frames from the base station 202 by the forward link and a transmission time adjustment device 226 for adjusting the timing of such signal transmission. The reverse traffic processor 228 determines an offset for determining an offset to be used to adjust the timing of signal transmission through the signal receiving device 230 and the signal transmitting device 224 that receive the traffic frame from the base station 202 through the reverse link. Device 232.

The offset determination apparatus 232 in the reverse traffic processing unit 228 obtains the traffic frame reception time transmitted from the base station 202 in the traffic frame received through the reverse link, and based on this, the offset of the forward traffic frame to be transmitted through the forward link. Calculate and transmit it to the transmission time adjustment device 226 in the forward traffic processing unit 222. The transmission time adjustment device 226 adjusts the transmission time point for the traffic frame to be transmitted on the forward link according to the criteria determined by the operator based on the information received from the offset determination device 232.

Although not shown, the control station 220 includes its own CPU internal clock and obtains information about the frame period (eg 20 msec for a CDAM system) from its CPU internal clock when generating traffic frames. Each of the above-described reception time measurement apparatus and reception time transmission apparatus in the base station, and the transmission time adjustment apparatus and offset determination apparatus in the control station may be implemented in software or hardware.

3 is a diagram illustrating a process of determining a time point for a control station to transmit a forward traffic frame to a base station according to an embodiment of the present invention.

First, the control station according to the present embodiment cannot know the absolute time since it cannot receive the GPS signal, and thus transmits the first forward traffic frame to the base station at any point in time. The base station can know the absolute time by the GPS receiver, and therefore the reception time measuring device in the base station measures the reception time of the corresponding forward traffic frame in relation to the maximum allowable arrival time. Then, the reception time transmission apparatus of the base station includes the measured time information in the header information of the frame and transmits the feedback when the traffic frame is transmitted to the control station through the reverse link. The offset determination apparatus of the control station needs to adjust the offset compared to the previous transmission time when the base station transmits the next forward frame based on the information on the time when the base station receives the traffic frame received from the base station by the reverse link. Determine. Then, the apparatus for adjusting the transmission time of the control station adjusts the timing for future forward frame transmission by reflecting the determined offset, and transmits the frame to the base station again through the forward link at the adjusted transmission time. In this manner, the frame transmission time is adjusted at the control station every time traffic frame transmission is made by the control station or at regular intervals. According to one embodiment of the present invention, the offset determination performed by the offset determination apparatus of the control station is as follows.

Offset = (16 + arrival margin-reception time) modulo 16 ...... (Equation 1)

Here, the arrival margin is a constant value determined by the system so that the forward traffic frame can be safely received within a certain range even if the transmission delay of the relay line varies to some extent. For example, in a system in which the arrival margin is set to 5, the offset value is 14 when the frame reception time by the base station is measured as 7.

After the offset value is determined, if the transmission time adjustment device of the control station reflects the offset value determined in the adjustment of the actual frame transmission time, it may be changed depending on the operator's setting. May be stored in a computer readable medium. By designating the correction interval at the time of transmission by the offset value, the operator can achieve efficient operation of the relay line and improvement of service quality.

4 is a table illustrating a result of adjusting a next frame transmission time based on a previous frame reception time received from a base station according to an embodiment of the present invention. As shown, the table 400 includes an initial timer index 402 at which the previous forward frame was transmitted from the control station, a reception time 404 of the forward frame measured at the base station, and an offset value determined by the offset determination device ( 406, and records that include an update timer index 408 for this time for the control station to forward frame transmission.

의 타이머 인덱스 보정에 의한다. According to this embodiment, the control station has 16 timer indexes, one for every 1.25 msec (1.25 msec is called 1PCG) within a frame transmission period of 20 msec, and transmits a forward frame in accordance with each timer index. The base station measures the time at which the forward frame is received in the frame transmission period of 20 msec in units of PCG, and then feeds back to the control station. The offset determination apparatus of the control station calculates the offset value in PCG units. In this embodiment, the offset value is determined by Equation 1 above, but the arrival margin is set to 5PCG. In addition, the correction for the offset value x is

By the timer index correction.

As a specific example, if the forward frame transmitted when the initial timer index is 7 is measured as being received at time 7 at the base station, the offset value is 14. In the present embodiment having 16 timer indexes within a total period of 20 msec, the offset value 14 has the same meaning as -2, so the timer index is adjusted to -1 and updated to 6. In another case, the offset value is 3 if the forward frame transmitted when the initial timer index is 6 is measured as being received at time 2 at the base station. At this time, the timer index is adjusted to +1 and updated to 7.

5 is a flowchart illustrating a forward traffic transmission process at a control station according to an embodiment of the present invention.

First, the signal transmission apparatus in the forward traffic processing section of the control station transmits a traffic frame over the forward link at any time (502). It then receives the traffic frame transmitted from the base station via the reverse link and receives the time information measured at the base station therefrom (504). The offset determination apparatus determines (506) whether the current step is the first offset adjustment. If it is determined in step 506 that the first offset adjustment is made, an offset value is calculated 508 based on the received time information.

If it is determined in step 506 that it is not the first offset adjustment, it is determined 510 whether the offset adjustment is active and the timing at which the current offset adjustment is to be made, with reference to the current system setting. If at step 510 the offset adjustment is active and it is determined that the current offset adjustment is to be made, then the procedure proceeds to step 508. After the offset value is obtained in step 508, the apparatus for adjusting the transmission time of the control station changes the designation of the transmission time of the forward traffic frame by reflecting the offset value (512), and transmits the traffic frame at the designated time (514). ). If it is determined in step 510 that the offset adjustment is not active or is not the timing at which the current offset adjustment is to be made, then the procedure proceeds to step 510 as is. Then, forward traffic is transmitted by the designated time point.

6 is a flowchart illustrating traffic frame processing at a base station according to an embodiment of the present invention.

First, the base station receives 602 a traffic frame sent from the control station via the forward link. Then, the reception time of the corresponding traffic frame is measured (604), and the measured time information is inserted into the header of the reverse traffic frame (606). Then, the reverse traffic processor of the base station transmits the traffic frame including the measurement value of the traffic frame reception time in the header to the control station (608).

Although the present invention has been described centering on the adjustment of the forward traffic frame transmission time point from the control station to the base station, it can be applied to the transmission and reception of traffic between the devices of the other mobile communication system. In addition, the present invention has been described based on the case of the CDMA system, but may be applied to other mobile communication systems.

As described above, embodiments of the present invention for understanding the present invention have been described, but as will be appreciated by those skilled in the art, the present invention is not limited to the examples described herein but is not limited to the scope of the present invention. It can be variously modified, reconfigured and replaced. Therefore, it is intended that the present invention cover all modifications and variations that fall within the true spirit and scope of the present invention.

According to the present invention, since the apparatus of the mobile communication system can dynamically determine a new traffic frame transmission time based on the feedback information, even when the transmission time varies, such as an increase in load on the relay line or a handoff between base stations, The frame can be safely received within the allowed arrival time, thereby improving the quality of service. Further, according to the present invention, since the control station does not need to have a GPS receiver, significant cost reduction effect can be expected. Furthermore, according to the present invention, by extracting statistics on offset adjustment for traffic transmission time, it is possible to automatically measure the congestion situation or transmission delay of the relay line, thereby allowing the operator to manage the system stably and efficiently. .

Claims (10)

CLAIMS 1. A method for a transmission station in a mobile communication system to determine when to send traffic, Sending traffic, Receiving from the receiving station a measure of the time the traffic was received at a receiving station, Calculating an offset for adjusting a time point at which the traffic is transmitted from the received measurement value, and Adjusting the time point at which the traffic is transmitted based on the calculated offset Traffic transmission time determination method comprising a. The method of claim 1, And the transmitting station is a base station or a control station. The method of claim 1, Measuring a time at which the receiving station receives the traffic transmitted from the transmitting station, and Including, by the receiving station, the measured value in the traffic sent to the transmitting station. Traffic transmission time determination method further comprising. The method of claim 1, And the mobile communication system is a CDMA mobile communication system. The method of claim 4, wherein The offset calculation step Offset = (16 + arrival margin-above measurement) modulo 16 And the arrival margin is a predetermined value.  The method of claim 5, The traffic transmission time adjustment step is performed according to the adjustment criteria determined by the operator based on the offset. The method of claim 6, Method for determining the time of traffic transmission that the operator can change the adjustment criteria. As a control station, A control station that determines forward traffic transmission timing through exchange of forward and reverse traffic without depending on the GPS signal receiving apparatus. The method of claim 8, A reverse direction including a signal receiving apparatus for receiving reverse traffic and an offset determining apparatus for acquiring information on the traffic reception time measured by the base station from the received reverse traffic, and determining an offset for the next forward transmission traffic by the obtained traffic. A traffic processor, and A forward traffic processor including a signal transmission device for transmitting forward traffic and a transmission time adjustment device for adjusting a transmission time of the forward traffic Control station comprising a. As a base station, A forward traffic processor comprising a signal receiving device for receiving forward traffic, and a reception time measuring device for measuring a time at which the received forward traffic is received; A reverse traffic processor comprising a signal transmitting device for transmitting reverse traffic and a receiving time transmitting device including a measured value of the received time in the reverse traffic Base station comprising a.

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