KR20060079105A - Apparatus and method for selecting serving sector in a mobile communication system - Google Patents

Abstract

The present invention relates to an apparatus and method for selecting a serving sector in a mobile communication system. The present invention provides an apparatus and method that can prevent unnecessary switching of the serving sector and waste of resources by efficiently selecting the serving sector.

A method according to the present invention is a method for determining a serving sector using a signal received from a base station, the method comprising: measuring the strength of a pilot signal received from a sector of an active set; Calculating a difference in the strength of the signal received from the sector of the active set, updating the selection parameters by comparing the calculated difference value with a predetermined threshold value, and updating the updated selection parameters and comparison parameters. And determining an optimal serving sector from the active sectors.

Cell, serving sector, serving sector determination, active sector, mobile communication system.

Description

Apparatus and method for selecting a serving sector in a mobile communication system {APPARATUS AND METHOD FOR SELECTING SERVING SECTOR IN A MOBILE COMMUNICATION SYSTEM}

1 is a configuration diagram of a base station and a terminal of a general CDMA communication system having a cellular structure;

2 is a control flowchart of a terminal for determining an optimal sector in a CDMA communication system according to the present invention;

3 is a control flowchart of a process for updating a selection parameter according to a preferred embodiment of the present invention;

4 is a control flowchart of selecting an optimal sector in an access terminal according to an embodiment of the present invention;

5 is an internal block diagram of an access terminal according to an embodiment of the present invention;

The present invention relates to an apparatus and method for selecting a sector in a wireless communication system, and more particularly, to an apparatus and method for selecting a serving sector in a mobile communication system.

Typically, a representative system of a wireless communication system is a mobile communication system. Such a mobile communication system refers to a system developed to provide a user to communicate without being restricted by a location. The mobile communication system has evolved from an initial voice oriented system to a system for providing data service gradually. As such, various systems, such as 1xEV-DO system, called HDR, and 1xEV-DV system, have been developed and commercialized.

The CDMA mobile communication system distinguishes users using orthogonal codes, which are limited resources, thereby providing voice services and / or data services. Since communication is performed using limited resources as described above, in order to provide faster data service to more users, a technique of performing communication by dividing a cell, which is a range of one base station, into sector units has been developed and used.

Therefore, a typical CDMA communication system has cells composed of several base stations, and one base station is divided into several sectors. Therefore, a terminal located in an area of a specific base station communicates with the network mainly through a sector in which the terminal is located. In this case, an access terminal (AT) may belong to one or more cells or sectors to perform communication. As described above, when communicating with two or more cells or sectors in a CDMA mobile communication system performing communication, traffic to be provided to a user is routed to each sector. As a result, the access terminal receives traffic from all active cells or sectors to which it belongs.

1 is a configuration diagram of a base station and a terminal of a general CDMA communication system having a cellular structure. Hereinafter, the shape of the base stations and the position of the terminal of a general CDMA communication system having a cellular structure will be described with reference to FIG. 1.

In FIG. 1, a first base station BS1 110, a second base station BS2 120, and a third base station BS3 130 are illustrated. Each of the base stations 110, 120, and 130 has three sectors, respectively, the first base station 110 has a sector of X1, Y1, and Z1, and the second base station 120 has a sector of X2, Y2, and Z2. The third base station 130 has sectors of X3, Y3, and Z3. As shown in FIG. 1, the access terminal (AT) 101 is located at the edge of the first base station, and belongs to X1 and is located at the boundary with Y1.

As shown in FIG. 1, when the access terminal 101 is located, the terminal may be located in a handover area. Therefore, in a typical mobile communication system, when soft handover is performed, the same signals are received from at least two sectors or more sectors. This means that the same data is routed to different sectors and eventually delivered to the access terminal 101.

On the other hand, in a system such as 1XEV-DV or 1XEV-DO or HSDA, which are high-speed data rate DMA data communication systems, only one sector is routed when data is transmitted to one terminal to maximize the forward link output of data traffic. . That is, data is transmitted to only one access terminal. Therefore, the access terminal must continue to check all active sectors, select the optimal serving sector among them, and notify the network. The network then transmits the data to the optimal serving sector known by the access terminal. This optimal serving sector selection is also referred to as 'site selection transmission diversity'.

According to an approach recently known as a method of selecting the optimal serving sector, the access terminal selects a serving sector having the strongest forward link signal among all active sectors and informs the network through a feedback channel.

Next, a process of selecting a serving sector by an access terminal in a general mobile communication system will be described.

Step 1: The access terminal measures and monitors the strength of the forward link signal of all active sectors.

Step 2: The access terminal determines the serving sector by comparing the strengths of the forward link signals of all active sectors. At this time, the sector with the forward link signal of the greatest strength is selected as the serving sector.

Step 3: The access terminal informs the network of the selected serving sector via a feedback channel.

This process is repeated continuously to monitor the strength of the forward signal of all active sectors.

In the above-described method, the sector-to-sector switching is performed quickly by continuously monitoring the forward strength of the active sector at each time point and notifying the network. Therefore, whenever switching of the serving sector occurs, data to be transmitted to the access terminal must be transmitted to the data queue of the sector. Thus, the access terminal cannot receive data until the data queue is ready. This fast switching of serving sectors causes severe network overhead or discontinuous transmission of data to the access terminal. In addition, when the serving sector is selected based on the pilot strength at a specific time, there is a possibility that the pilot strength is high due to incorrect signal strength calculation or surge. In this case, after selecting a serving sector, the effective signal strength received from the sector is reduced. That is, by switching the serving sector quickly without considering the above-mentioned points, it may adversely affect the communication quality due to the discontinuous transmission of data or the selection of an abnormal serving sector.

It is therefore an object of the present invention to provide an apparatus and method for selecting the correct serving sector.

Another object of the present invention is to provide an apparatus and method for preventing unnecessary switching of a network caused by an error in serving sector selection.

It is still another object of the present invention to provide an apparatus and method for selecting a serving sector so as to stably transmit data.

It is yet another object of the present invention to provide an apparatus method for preventing frequent replacement of a serving sector.

Another object of the present invention is to provide an apparatus and method for increasing the throughput of a network.

An apparatus of the present invention for achieving the above objects is a device for determining a serving sector using a signal received from a base station, the received signal strength measuring the strength of the pilot signal received from the serving sector and the active set of sectors Calculates a difference between a measurement unit and a signal strength received from a serving sector and a signal received from a sector of the active set, and compares the calculated difference value with a predetermined threshold value to update the selection parameters; And a controller for determining an optimal serving sector from the active sectors using the updated selection parameters and comparison parameters, and a memory for storing the parameters.

A method of the present invention for achieving the above objects is a method for determining a serving sector using a signal received from a base station, comprising the steps of measuring the strength of the pilot signal received from the sector of the active set, and from the serving sector Calculating a difference between the strength of the received signal and the strength of the signal received from the sector of the active set; updating the selection parameters by comparing the calculated difference value with a predetermined threshold; Determining the optimal serving sector from the active sectors using the parameters and the comparison parameters.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

Before describing the various aspects and details of the invention, it will be useful to describe the environment in which the invention is used. A CDMA system of a data rate for performing a conventional high speed transfer is shown in FIG. As described above, the CDMA system illustrated in FIG. 1 includes three cells, namely, Cell 1, Cell 2, and Cell 3. Each cell also includes three sectors, the description of which has been described above. It is assumed here that the access terminal 101 communicates with three active sectors X1, Y1, and Z3. And it is assumed that the current serving sector is X1. Therefore, data traffic to be provided to the access terminal 101 is routed from the base station BS1 to the sector X1 and transmitted from the sector X1 to the access terminal A.

Thus, access terminal A continuously monitors the forward link signal strength of active sectors X1, Y1, and Z3. At this point, it is assumed that the forward signal strength of sector Z3 is the strongest. The access terminal will then immediately select sector Z3 sector and inform the network. Thus, the data traffic is routed and forwarded to sector Z3 of the third base station 130, which is then sent to access terminal A in sector Z3.

Then, at some point, when sector X1 has the strongest forward link signal, access terminal 101 selects sector X1 as the serving sector. Next time, sector Z3 again has the strongest forward link signal. After a few minutes, there is a possibility that a fast switch between two or more sectors will occur if sector X1 has the strongest forward link signal. Whenever switching of serving sectors occurs in this manner, data to be transmitted to the access terminal 101 must be transmitted to the data queue of the sector. As a result, undesirable fast switching occurs.

2 is a control flowchart of a terminal for determining an optimal sector in a CDMA communication system according to the present invention. Hereinafter, a control flow for determining an optimal sector for a CDMA communication system according to the present invention will be described in detail with reference to FIG. 2.

FIG. 2 according to the present invention described below includes a process of determining an optimal serving sector to implement site select transmit diversity for an access terminal. This process may be implemented in hardware or software at the access terminal. When operating in an HDR system of a CDMA system, the following procedure is performed once in each slot of each HDR system while the access terminal is in a connected state, that is, while communicating with the access network.

The access terminal starts the routine for the first time in step 200, and in step 201 the access terminal measures the forward signal strength of each sector in the active pilot set. The access terminal also measures the forward link signal strength of the current serving sector. The access terminal then updates the sector selection parameters for each sector in step 202. This update uses hysteresis of timing and signal levels for each sector of the active set. This will be described in more detail below. In step 203, the access terminal selects an optimal serving sector based on selection parameter values for each sector. At this time, if there is more than one serving sector candidate, the access terminal uses the comparison parameter to identify the optimal serving sector. The use of such comparison parameters will be described in more detail below. The access terminal then proceeds to step 204 to terminate the process.

3 is a control flowchart of a process for updating a selection parameter according to a preferred embodiment of the present invention. Hereinafter, a control process for updating a selection parameter according to the present invention will be described in detail with reference to FIG. 3.

Prior to the description of FIG. 3, the selection parameters that are updated by using the signal strength measured in each slot of the HDR system have the following values.

(1) DIFF: Indicates the difference between the forward link signal strength of one sector of the active set and the current serving sector.

(2) SELECTION_COUNT: This parameter indicates the number of times the DIFF value is larger than the TH_STRENGTH value. The parameter is increased when FADING_CNT, which will be described later, is 0 and the DIFF value is larger than the TH_STRENGTH value. When a parameter of a corresponding sector changes from 0 to a non-zero value, that is, whenever the value increases, the corresponding sector becomes a candidate of a serving sector. The parameter is also reset after the optimal serving sector is selected.

(3) FADING_COUNT: This parameter indicates the number of times the DIFF value is smaller than the TH_STRENGTH value for the sector serving as the serving sector candidate. The parameter is incremented when the SELECTION_COUNT value is not zero and the DIFF value is less than the TH_STRENGTH value. The parameter is also reset after the optimal serving sector is selected.

Next, an update process of the selection parameter for finding an optimal serving sector will be described based on the above values.

In step 300, the terminal starts the process of updating the selection parameter for finding the optimal serving sector. In step 301, the terminal calculates the difference between the forward link signal strength of the sector of the active set and the forward link signal strength of the current serving sector. . That is, the access terminal calculates the DIFF value for the jth active sector. The access terminal then proceeds to step 302 to check whether the DIFF value of the jth sector is greater than the threshold value TH_STRENGTH. If the check result DIFF value of step 302 is greater than the TH_STRENGTH value, the process proceeds to step 303, otherwise, proceeds to step 306.

First, the case proceeding to step 303 will be described. The access terminal checks whether the FADING_COUNT value of the sector is 0 in step 303. If the FADING_COUNT value is 0, the flow proceeds to step 304, otherwise proceeds to step 305. First, in step 304, the access terminal increases the SELECTION_COUNT value of the sector, stores the DIFF value for the sector, and the process proceeds to step 310 to end the process. On the other hand, if the process proceeds to step 305, the access terminal resets the FADING_COUNT value of the sector to 0, and proceeds to step 310 to end the process.

On the other hand, if proceeding from step 302 to step 306, the access terminal checks whether the SELECTION_COUNT value is zero. If the SELECTION_COUNT value is 0 in step 306, the routine proceeds to step 310 and ends the routine.

On the other hand, if the result of the check in step 306, the SELECTION_COUNT value is not 0, the access terminal proceeds to step 307 to increase the FADING_COUNT value of the sector of the sector, and proceeds to 308. In step 308, the access terminal checks whether the FADING_COUNT value of the sector is equal to the MAX_FADING_COUNT value. If the FADING_COUNT value in step 308 is equal to the MAX_FADING_COUNT value, the process proceeds to step 309; otherwise, the process proceeds to step 310 to end the routine. In step 309, the access terminal resets the FADING_COUNT value of the sector, decreases the SELECTION_COUNT value of the sector by the PENALTY_COUNT value, and proceeds to step 310 to end the routine.

The above-described processes are processes for updating the selection parameter of FIG. 2. Next, a process for optimal sector selection, step 203 of FIG. 2, will be described.

4 is a control flowchart of selecting an optimal sector in an access terminal according to an exemplary embodiment of the present invention. Hereinafter, a control process for selecting an optimal sector according to the present invention will be described in detail with reference to FIG. 4. Before describing FIG. 4, it should be noted that the process described in FIG. 4 is performed for each HDR slot in order to identify an optimal serving sector.

The process of FIG. 4 begins in step 400, and when the routine of FIG. 4 starts, the access terminal proceeds to step 401 to determine a sector whose SELECTION_COUNT value is equal to the MAX_SELECTION_COUNT value. In other words, the access terminal selects an optimal serving sector from the determined sectors. Accordingly, the access terminal proceeds to step 402 after performing operation 401 and uses comparison variables to select an optimal serving sector from the determined sectors. The following comparison parameters are used to identify the optimal serving sector from the determined sectors.

DRC Lock bit information: The information is used only in the 1X EVDO system. The bit is received from all sectors in the active set. The information indicates the reliability of the reverse link. If the DRC Lock bit received from the sector determined in step 401 is '0', i.e., if the reverse link is unreliable, this sector is unmarked.

Here, a weighted average of pilot signal strengths is calculated for each sector determined as described above for the active set. The sector with the largest weighted average value is selected as the optimal serving sector. The weighted average of the pilot signal strengths is calculated in the same manner as in Equation 1 below.

In Equation 1, W _i is a weight assigned to an i th DIFF value, and is equal to i / MAX_SELECTION_COUNT, and DIFF _i is an i th value of DIFF.

After identifying the optimal sector through the above process, the access terminal proceeds to step 403 to reset the FADING_COUNT and SELECTION_COUNT values for all sectors of the active set, and proceeds to step 404 to end the process.

Next, a device for performing an operation according to the present invention will be described.

5 is a block diagram illustrating an internal configuration of an access terminal according to an exemplary embodiment of the present invention.

The radio 520 of the access terminal includes a duplexer 521, an RF receiver 522, and an RF transmitter 523 therein. The duplexer 521 distinguishes a path between a transmission signal and a reception signal, outputs a signal received from the antenna ANT to the RF receiver 522, and outputs a signal received from the RF transmitter 523 to the antenna ANT. Will output The RF receiver 522 down-converts the received radio signal into a baseband signal and outputs the signal to the modem 533. In addition, the RF receiver 522 outputs a part of the received signal to the received signal strength measuring unit 531. The received signal strength measuring unit 531 measures the received strength of the pilot signal received from each sector or cell and outputs it to the controller 511. The RF transmitter 523 band-up converts the signal received from the modem 533 into the band of the signal to be transmitted, and then outputs the converted signal to the duplexer 521.

The modem 533 demodulates and decodes the received signal and outputs it to the controller 511 or the display 545. In addition, the modem 533 encodes and modulates a message such as data to be transmitted or a cell selection signal and outputs the same to the RF transmitter 523. Accordingly, the modem 533 performs modulation and demodulation, and encoding and decoding operations. Such a modem may be configured as a single chip or two or more different modems for data processing such as a video.

The controller 511 performs overall control of the wireless unit 520 and control of the modem 533, and stores specific control data in the memory 543 or reads data from the memory 543 to perform a corresponding operation. . Accordingly, the controller 511 performs the control operations of FIGS. 2, 3, and 4 described above. That is, the optimal sector selection is controlled by using the strength information of the signal received from the received signal strength measuring unit 531 and parameters previously stored in the memory 543. The control unit 511 controls other operations performed in the access terminal.

The key input unit 541 generates a key signal input by the user and provides it to the controller 511. The key input unit 541 may be configured in a key metric structure, or may be configured to use a touch screen or a voice signal by matching a specific command. The memory 543 stores parameters according to the present invention, stores control data for controlling the access terminal and various data stored by the user, and temporarily stores control data generated during a control operation in the controller 511. have. The display unit 545 may be generally configured as a liquid crystal display panel (LCD). In addition, the display unit 545 may be configured to display by using a device such as a vibration motor and a light emitting diode.

As described above, when the sector is selected using the present invention, an accurate serving sector can be selected, and thus, unnecessary switching of the network can be prevented, thereby stably transmitting data. In addition, this prevents frequent replacement of the serving sector and increases the throughput of the network.

Claims (8)

A method for determining a serving sector using a signal received from a base station, the method comprising: Measuring the strength of the pilot signal received from the sector of the active set; Calculating a difference between the strength of the signal received from the serving sector and the strength of the signal received from the sector of the active set; Updating the selection parameters by comparing the calculated difference value with a predetermined threshold value; And determining an optimal serving sector from active sectors by using the updated selection parameters and comparison parameters. The method of claim 1, wherein the selection parameter, A parameter that counts the number of times the value of the difference is greater than the predetermined threshold value; And a parameter for counting the number of times when the difference value is smaller than the predetermined threshold value. The method of claim 1, wherein the comparison parameter, A serving sector selection method in a mobile communication system, characterized in that the value determined based on the reliability of the reverse signal. The method of claim 1, wherein determining the optimal serving sector is: A method of selecting a serving sector in a mobile communication system, wherein a sector having a maximum weight average calculated as in Equation 2 is determined as an optimal serving sector.

In Equation 2, W _i is a weight assigned to an i th DIFF value, and is equal to i / MAX_SELECTION_COUNT, and DIFF _i is an i th value of DIFF. DIFF also means the difference between the signal strength of the serving sector and the received signal strength of the i-th sector. An apparatus for determining a serving sector using a signal received from a base station, the apparatus comprising: A received signal strength measuring unit for measuring the strength of a pilot signal received from a serving sector and an active set of sectors; Calculate a difference between the strength of the signal received from the serving sector and the strength of the signal received from the sector of the active set, update the selection parameters by comparing the calculated difference value with a predetermined threshold, and update the selected selection parameter. Control unit for determining an optimal serving sector from the active sectors using the parameters and the comparison parameters; And a memory for storing the parameters. The method of claim 5, wherein the selection parameter, A parameter that counts the number of times the value of the difference is greater than the predetermined threshold value; And a parameter for counting the number of times when the difference value is smaller than the predetermined threshold value. The method of claim 5, wherein the comparison parameter, Serving sector selection device in a mobile communication system, characterized in that the value determined based on the reliability of the reverse signal. The method of claim 5, wherein the control unit, The apparatus for selecting a serving sector in a mobile communication system, wherein, when determining the optimal serving sector, a sector having a maximum weight average calculated as in Equation 3 is determined as an optimal serving sector.

In Equation 3, W _i is a weight assigned to the i-th DIFF value, the same as i / MAX_SELECTION_COUNT, and DIFF _i is the i-th value of DIFF. DIFF also means the difference between the signal strength of the serving sector and the received signal strength of the i-th sector.

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