KR101300986B1 - Apparatus and method for selecting serving sector in a mobile communication system - Google Patents

Abstract

The present invention measures the strength of a signal received from each of a serving sector and an active set of sectors in a mobile communication system, and between the strength of the signal received from the serving sector and the strength of a signal received from each of the sectors of the active set. Calculate a difference value, update sector selection parameters for each of the sectors of the active set based on the calculated difference value, and select at least one of the sectors of the active set using the updated sector selection parameters And select one of the selected at least one sector as a final serving sector using a comparison parameter determined based on reliability of a reverse signal, wherein the comparison parameter is a DRC Lock (Data Rate Control) received from the selected at least one sector. Lock) bit.

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 an access terminal for determining an optimal sector in a CDMA communication system according to an embodiment of the present invention;

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

4 is a control flowchart of an access terminal when selecting an optimal sector 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 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 including several base stations, and one cell is divided into several sectors. Therefore, a terminal located in an area of a specific base station mainly communicates with a network in a sector where it is located. In this case, an access terminal (AT) may belong to one or more cells or sectors to perform communication. In the CDMA communication system in which communication is performed as described above, traffic to be provided to a user is routed to each sector when communication is performed in two or more cells or sectors. As a result, the access terminal can receive 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. The first to third base stations 110, 120, and 130 each have three sectors. Specifically, the first base station 110 has a sector of X1, Y1, Z1, the second base station 120 has a sector of X2, Y2, Z2, and the third base station 130 has X3, Y3. , Has a sector of Z3. As shown in FIG. 1, the access terminal (AT) 101 is located at the edge of the cell of the first base station 100 and is included in the X1 sector located at the boundary with Y1.

That is, the access terminal 101 is located in the handover area. 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 is because the same data is routed to different sectors and consequently delivered to the access terminal 101.

On the other hand, in systems such as 1XEV-DV or 1XEV-DO or HSDA, which are high-speed data rate DMA data communication systems, one data may be transmitted to one access terminal to maximize the forward link output of data traffic. Route only to sectors. Therefore, the access terminal must continuously inspect all active sectors, select the optimal serving sector among the active sectors, 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'.

As a method of selecting the optimal serving sector, an access terminal selects a serving sector having the strongest forward link signal among all active sectors and informs the network of this via 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 selects 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. And, 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.

According to an aspect of the present invention, there is provided an apparatus comprising: An apparatus for selecting a serving sector in a mobile communication system, the apparatus comprising: a received signal strength measuring unit measuring an intensity of a signal received from each of a sector of a serving sector and an active set, a strength of a signal received from the serving sector, and Compute the difference value between the strengths of the signals received from each of the sectors of the active set, update sector selection parameters for each of the sectors of the active set based on the calculated difference value, and update the updated sector selection parameters. A control unit for selecting at least one of the sectors of the active set, and selecting one of the selected at least one sector as a final serving sector using a comparison parameter determined based on reliability of a reverse signal; A memory for storing the selection parameters and the comparison parameter; Comparison parameters include the selected at least one of the Lock DRC (Data Rate Control Lock) bit received from the sector.

According to an aspect of the present invention, A method for selecting a serving sector in a mobile communication system, the method comprising: measuring the strength of a signal received from each of a serving sector and an active set of sectors, the strength of the signal received from the serving sector, and the active set of a sector Calculating a difference value between the strengths of the signals received from each of the signals; updating the sector selection parameters for each of the sectors of the active set based on the calculated difference value; Selecting at least one of the sectors of the active set by using one of the sectors, and selecting one of the at least one sector selected as a final serving sector using a comparison parameter determined based on reliability of a reverse signal. The comparison parameter is a DRC Lock (Data Rat) received from the selected at least one sector. e Control Lock) bit.

The operation principle of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this 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 conventional data rate CDMA communication system for performing high speed transmission is shown in FIG. The CDMA communication system shown in FIG. 1 is composed of a total of three cells including Cell 1, Cell 2, and Cell 3. In addition, each of cells 1 to 3 includes three sectors, and description thereof is as described above. It is assumed here that the access terminal 101 communicates using three active sectors X1, Y1, and Z3. And it is assumed that the serving sector of the current access terminal 101 is X1. Thus, the data traffic to be provided to the access terminal 101 is routed from the first base station 110 to sector X1 and transmitted from sector X1 to access terminal 101.

Therefore, the access terminal 101 continuously monitors the forward link signal strength of the 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 101 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, and then the forwarded data traffic is sent to the access terminal 101 at sector Z3.

Then, at some point, if 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. Thereafter, 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. Thus, undesirable fast transitions occur.

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

2 illustrates a process of determining an optimal serving sector to implement site selection transmit diversity for an access terminal. 2 may be implemented in hardware or software in an access terminal. In the HDR communication system of the CDMA communication system, a process described below is performed once in each slot of each HDR communication system while the access terminal is in a connected state, that is, while communicating with the access network.

The access terminal first starts the process of determining the optimal serving sector in step 200. In step 201, the access terminal measures the forward link 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 sector 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. How to use these comparison parameters will be described in detail below. Thereafter, the access terminal proceeds to step 204 to terminate the process.

3 is a control flowchart for updating a sector selection parameter according to an embodiment of the present invention.

Prior to the description of FIG. 3, sector selection parameters that are updated using the strength of the signal measured in each slot of the HDR communication 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: It indicates the number of times DIFF value is larger than TH_STRENGTH value. The parameter is incremented when FADING_CNT is 0 and the DIFF value is greater than the TH_STRENGTH value. When a parameter of a corresponding sector changes from 0 to a non-zero value, that is, each time 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: For a sector serving as a serving sector candidate, the DIFF value is smaller than the TH_STRENGTH value. 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, a process of updating a sector selection parameter for finding an optimal serving sector based on the above values will be described.

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

First, a case in which the access terminal proceeds to step 303 will be described. In step 303, the access terminal checks whether the FADING_COUNT value of the sector is zero. If the check result FADING_COUNT value is 0, the access terminal proceeds to step 304, otherwise proceeds to step 305. In step 304, the access terminal increases the SELECTION_COUNT value of the sector, stores the DIFF value for the sector, and proceeds to step 310 to complete all processes. On the other hand, when the access terminal proceeds to step 305, the access terminal resets the FADING_COUNT value to 0, and proceeds to step 310 to end all processes.

Meanwhile, when the access terminal proceeds from step 302 to step 306, the access terminal checks whether the SELECTION_COUNT value is zero. If the access result of the check in step 306 SELECTION_COUNT value is 0, the access terminal proceeds to step 310 and ends all processes.

On the other hand, if the SELECTION_COUNT value is not 0, the access terminal proceeds to step 307 to increase the FADING_COUNT value of the corresponding sector of the sector, and proceeds to step 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 is equal to the MAX_FADING_COUNT value in step 308, the access terminal proceeds to step 309; otherwise, proceeds to step 310 to end all processes. 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 complete all processes.

The above-described processes are processes for updating the sector 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 an access terminal when selecting an optimal sector according to an embodiment of the present invention. It should be noted that the process described in FIG. 4 is performed for each HDR slot to identify an optimal serving sector.

The process of FIG. 4 starts in step 400, and when the process 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. The access terminal selects an optimal serving sector from the determined sectors. Thus, the access terminal proceeds to step 402 and uses the 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 DRC Lock bit information is used only in the 1X EVDO system. The DRC Lock bit information is received in all sectors of the active set. The DRC Lock bit information indicates the reliability of the reverse link. If the DRC Lock bit received from the sector determined in step 401 is '0', that is, if the reverse link is not reliable, the display of the sector is released.

Here, a weighted average value of the 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 using Equation 1 below.

In Equation 1, DIFF _i represents a difference value between the strength of the signal received from the serving sector and the strength of the signal received from the i-th sector of the active set, and W _i represents a weight assigned to DIFF _i . Determined by i / MAX_SELECTION_COUNT, MAX_SELECTION_COUNT indicates the number of sectors of the active set.

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 finish all processes.

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

5 is an internal block diagram of an access terminal according to an 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. The duplexer 521 distinguishes a path between a transmission signal and a reception signal, outputs a signal received from an antenna ANT to the RF receiver 522, and outputs a signal received from the RF transmitter 523 to the antenna. 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 a band of a signal to be transmitted, and then outputs it to the duplexer 521.

The modem 533 demodulates and decodes the received signal and outputs the same 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, encoding and decoding operations. Such a modem may be composed of one single chip or two or more different modems for data processing such as video.

The control unit 511 performs overall control of the wireless unit 520 and the control of the modem 533, and stores specific control data in the memory 543 or reads data from the memory 543. Perform the action. Accordingly, the controller 511 performs the control operations of FIGS. 2, 3, and 4 described above. That is, 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 performs control of operations performed in the access terminal.

The key input unit 541 generates a key signal input by the user and provides the generated key signal 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 by the controller 511. Can be. The display unit 545 may generally be 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, an unnecessary network switching 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)

In the method for selecting a serving sector in a mobile communication system, Measuring the strength of a signal received from each of the serving sector and the active set of sectors, Calculating a difference between the strength of the signal received from the serving sector and the strength of the signal received from each of the sectors of the active set; Updating sector selection parameters for each of the sectors of the active set based on the calculated difference value; Selecting at least one of the sectors of the active set using the updated sector selection parameters; Selecting one of the selected at least one sector as a final serving sector using a comparison parameter determined based on reliability of a reverse signal, And wherein the comparison parameter comprises a Data Rate Control Lock (DRC Lock) bit received from the selected at least one sector. The method of claim 1, The sector selection parameters are And a first parameter for counting the number of times when the calculated difference is greater than the threshold, and a second parameter for counting the number of times when the calculated difference is less than the threshold. How to choose. delete The method of claim 1, Selecting one of the selected at least one sector as the final serving sector, A weighted average value of the signal strengths of the selected at least one sector is calculated using Equation 2 below, and a sector corresponding to the maximum weighted average value among the calculated at least one weighted average value is selected as the final serving sector. Serving sector selection method in a mobile communication system comprising a process. &Quot; (2) "

In Equation 2, DIFF _i represents a difference value between the strength of the signal received from the serving sector and the signal received from the i-th sector of the active set, and W _i represents a weight assigned to DIFF _i . Determined by i / MAX_SELECTION_COUNT, MAX_SELECTION_COUNT represents the number of sectors in the active set. An apparatus for selecting a serving sector in a mobile communication system, A received signal strength measuring unit for measuring the strength of a signal received from each of a serving sector and an active set of sectors; Compute a difference value between the strength of the signal received from the serving sector and the strength of the signal received from each of the sectors of the active set, and based on the calculated difference value, a sector selection parameter for each of the sectors of the active set. Select at least one of the sectors of the active set using the updated sector selection parameters, and finally serve one of the selected at least one sector using a comparison parameter determined based on the reliability of a reverse signal. A control unit for selecting sectors; A memory for storing the updated sector selection parameters and the comparison parameter, And the comparison parameter comprises a Data Rate Control Lock (DRC Lock) bit received from the selected at least one sector. 6. The method of claim 5, The selected sector parameters are And a first parameter for counting the number of times when the calculated difference is greater than the threshold, and a second parameter for counting the number of times when the calculated difference is less than the threshold. Optional device. delete 6. The method of claim 5, The control unit, A weighted average value of the signal strengths of the selected at least one sector is calculated using Equation 3 below, and a sector corresponding to the maximum weighted average value among the calculated at least one weighted average value is selected as the final serving sector. Serving sector selection device in a mobile communication system, characterized in that. &Quot; (3) "

In Equation 3, DIFF _i represents a difference value between the signal strength received from the serving sector and the signal received from the i-th sector of the active set, and W _i represents a weight assigned to DIFF _i . Determined by i / MAX_SELECTION_COUNT, MAX_SELECTION_COUNT represents the number of sectors in the active set.

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