KR20020018204A - A method for controlling the admission of a call in CDMA network - Google Patents

Abstract

PURPOSE: A method for controlling call admission in a CDMA(Code Division Multiple Access) network is provided to improve the quality of a forward link by determining whether a generated new call is admitted with reference to forward power consumption. CONSTITUTION: If the admission of a new call is requested from an MS(Mobile Station)(10) to a BS(Base Station)(20)(S201), the BS(20) transmits a pilot signal to the MS(10) and requests a receipt measurement value to the pilot signal to the MS(10)(S202). The BS(20) receives a receipt power value and an Ec/Io value of the pilot signal and stores the received receipt power value and Ec/Io value of the pilot signal(S203), and requests a call profile including a call type, a minimum request transmission speed, and a minimum request value of the Ec/Io to the MS(10)(S204). The MS(10) sends the call profile to the BS(20)(S205). The BS calculates a minimum transmission power to be assigned to the new call on the basis of the call profile, the Ec/Io value, and the mean receipt power value(S206). The BS(20) compares the calculated minimum transmission power value with a redundancy transmission power value(S207). If the minimum transmission power value is not more than the redundancy transmission power value, the BS(20) admits the new call and transmits a channel assignment message to the MS(10)(S208). If the minimum transmission power value is more than the redundancy transmission power value, the BS(20) rejects the new call and transmits a reject notification message to the MS(10)(S209).

Description

A method for controlling the admission of a call in CDMA network

The present invention relates to a call admission control method in a code division multiple access (CDMA) network, and more particularly, to improve the quality of a forward link by determining whether to accept a new call generated in consideration of forward power consumption. The present invention relates to a call admission control method in a code division multiple access network.

In the existing IS-95A communication system, since the capacity of the forward direction, which is generally limited by interference, is larger than the reverse direction, it is decided whether to accept a new call mainly based on the power level of the reverse direction.

That is, in a reverse environment, since signals transmitted from an unspecified number of terminals are received by one specific base station, mutual orthogonality between codes used by each terminal is difficult to be guaranteed from the standpoint of the receiving base station. Since one specific base station transmits signals to multiple terminals at the same time, each terminal receives multiple signals at the same time, thereby ensuring mutual orthogonality between the received signal codes. Therefore, since each terminal in the forward environment can remove received signals destined for another terminal other than itself very well as compared to the reverse environment, the call admission control method in the conventional IS-95A communication system mainly uses the reverse power. It was decided based on the level.

However, in the case of next generation CDMA networks such as IS-95C and IMT-200 communication systems, a technique for maximizing orthogonality between received channel codes is provided by allowing a plurality of signals received at a base station to arrive simultaneously even in a reverse environment. As a result, the relative difference in capacity relative to the forward direction in the IS-95A is reduced. Also, in the forward environment, the power control cycle can be shortened to provide more sophisticated power control methods. In the next generation CDMA network, when data services such as Internet browsing are to be applied / performed, the data volume of the forward traffic is generally reversed. Since the amount of data is larger than the amount of traffic, the required transmission rate in the forward direction may be much larger than the transmission rate required in the reverse direction based on one call. Accordingly, the importance of call admission control based on the quality of the forward link is greatly emphasized. There is a situation.

The present invention has been created for the forward call admission control required as described above, and its object is to maintain the quality of a call currently being serviced above a predetermined criterion and to maximize the acceptability of a new call. To provide a way.

Another object of the present invention is to prepare a CDMA network to maximize the acceptability of a new call while maintaining the quality of a call currently being serviced above a predetermined standard in preparation for a call quality degradation of a target cell due to an increase in power in a neighbor cell after call acceptance. To provide a call admission control method in.

1 is a view for explaining the terminology and structure for the use of forward power in the fixed station of the present invention,

2 is a flowchart of a rock lock control method in a CDMA network according to an embodiment of the present invention;

3 is a flowchart of a rock lock control method in a CDMA network according to another embodiment of the present invention;

4 is a graph of a probability distribution function previously stored in a fixed station according to the present invention, and is an example of a statistical distribution function graph of a received interference amount of a mobile station during an average talk time according to a type of a call stored in advance corresponding to a current interference density value.

5A is an example of a function graph showing the correlation between the interference density value ΔI and the power depletion probability P increased according to the present invention.

FIG. 5B is a table listing the function graph of FIG. 5A.

※ Explanation of code for main part of drawing

10: mobile station 20: fixed station

In order to achieve the above object, the rock lock control method in a CDMA network according to the present invention is a call control method in a fixed station through communication between a mobile station and a fixed station, wherein the mobile station is requested to accept a new call from the mobile station. Requesting a measurement value for a pilot signal from the user; Receiving a energy-to-chip energy-to-interference density ratio (Ec / Io) value of the pilot signal measured from the mobile station by the request; A third step of requesting the mobile station a profile of the call including the desired type of call, the minimum required transmission rate (R _req ), and the minimum required value of the energy per bit to interference density ratio ((Eb / Io) _req ]; A fourth step of calculating a minimum transmit power value to be allocated to the new call based on the profile of the call received from the mobile station by the request and the Ec / Io value received in the second step; And a fifth step of comparing the calculated minimum transmission power value with the currently available forward margin power value, and determining whether to accept the new call according to the comparison result.

In order to achieve the above object, the method of controlling a lake lock in a CDMA network according to the present invention is a call control method in a fixed station through communication between a mobile station and a fixed station. Requesting a mobile station for a measurement on a pilot signal; The received power value Rx _pilot and the energy-to-chip density ratio Ec / Io value of the pilot signal measured from the mobile station are received by the request, and the received power value Rx _pilot of the received pilot signal and Correspondingly, a second step of calculating a forward link loss and an interference density based on a difference between transmit power values Tx _pilot of the corresponding pilot signal transmitted from the fixed station itself; A third step of requesting the mobile station a profile of the call including the desired type of call, the minimum required transmission rate (R _req ), and the minimum required value of the energy per bit to interference density ratio ((Eb / Io) _req ]; Calculating a minimum transmit power value to be allocated to the new call based on the call profile received from the mobile station by the request and the value received in the second step and the calculated value (the link loss and the interference density). Fourth step; A fifth step of calculating a residual forward transmit power value usable when it is assumed that the calculated minimum transmit power value is allocated to the new call; Calculating a ratio of the usable remaining forward transmit power value to the minimum transmit power value; Based on the statistical distribution function (probability characteristic) of the received interference amount of the mobile station for a predetermined time after the preset current time corresponding to the current interference density value calculated in the second step, and the ratio value calculated in the sixth step. A seventh step of obtaining a power depletion probability for the predetermined time; And an eighth step of comparing the obtained power depletion probability with a predetermined threshold probability, and determining whether to accept the new call according to the comparison result, in particular, the statistical probability characteristic of the seventh step is probability density. The power depletion probability is increased by the ratio calculated in the sixth step from the current interference density value among the total areas of the entire intervals formed by the probability density function graph. It is characterized by the ratio which occupies the area of the area | region which becomes more than a density value.

As described above, the method of controlling the rock lock in the CDMA network according to the present invention includes the mobile station as a mobile station (MS), a base station (BS), a control station (BSC) and a switching station (BS). MSC: Mobile Switching Center (MSC), which is a system for controlling the operation of the mobile station as a counterpart of the mobile station, and is performed through mutual communication such as signal exchange between the fixed stations, and for implementing the present invention, the following prerequisites Is required.

First, the maximum value of forward power that can be allocated by one fixed station is limited, and it is impossible to allocate power above this maximum value.

Second, only the power of the traffic channel can be adjusted by the forward power control, and the power of the pilot channel, paging channel, and synchronization channel is constantly fixed.

Third, when each new call occurs, the fixed station receives a profile of various new calls from the mobile station through service negotiation between the mobile station and the fixed station.

Fourth, the average talk time is statistically calculated for each call type (voice call or data call).

Fifth, the operator and the power drain caused by insufficient allocation of power to the probability (Call Dropping Probability) that could cause the cutting arc currently call service quality objectives Threshold: try to keep below _{(T QoS Target Quality of Service)} .

Sixth, if the amount of received interference of any mobile station is known at present, a distribution function for knowing the distribution of received interference of the mobile station for a predetermined time after the present time point is statistically calculated and stored in the fixed station.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the rock lock control method in a CDMA network according to a preferred embodiment of the present invention, it will be described on the premise that all six conditions are provided.

1 is a view for explaining the term and structure for the use of forward power in a fixed station of the present invention, Tx _pilot is the transmission power of the pilot channel, Tx _sync is the transmission power of the synchronization channel, Tx _paging is the transmission power of the paging channel, Tx _traffic is the transmit power of the traffic (or call) channel, R is the unassigned free transmit power, Tx _current is the total transmit power currently in use, and Tx _max is the total maximum transmit power, where Defined as "R = Tx _max -Tx _current " and "Tx _current = Tx _pilot + Tx _sync + Tx _paging + Tx _traffic ", among which the power control is possible, the transmission power (Tx) of the traffic channel as described above _traffic ).

2 is a flowchart of a rock lock control method in a CDMA network according to an embodiment of the present invention.

First, when a new call is accepted from the mobile station (MS) 10 to the fixed station (BS) 20 (Call Request Message) (S201), the fixed station 20 signals a pilot to the mobile station 10. In addition to transmitting the signal, a received measurement value for the pilot signal is requested (Pilot Measurement Request) (S202).

Subsequently, the mobile station 10 measures the average received power value Rx _pilot and the energy-to-chip energy density ratio Ec / Io of the pilot signal to the fixed station 20 according to the request of the fixed station 20. Send Pilot Measurement. The fixed station 20 receives and stores the Rx _pilot and Ec / Io values (S203), then the desired type of call (data call or voice call) to the mobile station 10, the minimum required transmission rate (R _req ), And a call profile (Call Profile Request) including a minimum required value of energy to interference density per bit [(Eb / Io) _req ] (Call Profile Request) (S204).

The mobile station 10 sends the desired profile of the call to the fixed station 20 according to the request (Send the Call Profile) (S205). The fixed station 20 assigns a minimum transmit power Tx _new to be allocated to the new call based on the profile of the call received from the mobile station 10 and the Ec / Io value and Rx _pilot value received and stored in step S203. Calculation (S206), the description of the calculation process will be described later.

Finally, the fixed station 20 compares the calculated minimum transmission power value Tx _new with the unassigned and currently available spare transmission power value Res (S207). If the value does not exceed the currently available forward transmit power value, the new call is accepted (Admit), and a channel assignment message is transmitted to the mobile station 10 (S208). If the value exceeds, the new call is rejected. Reject and transmit a reject notification to the mobile station 10 (S209).

The calculation process of the minimum transmission power Tx _new in step S206 will be described below.

First, the following Equation (1) is established from Ec / Io and Rx _pilot received and stored in step S203, and the sum of the forward total noise and the interference can be obtained from the equation (1). The total noise becomes a noise value measured by the mobile station 10 when there is no call volume, and thus the inerference value can be known.

Ec / Io = Rx _pilot / (Total Noise + Interference) ---- (1)

In addition, the following Equation (2) can be established from the received call profile, where Rx _new is the minimum received power that the mobile station 10 should receive, and W is the bandwidth.

(Eb / Io) _req = [Rx _new / (Total Noise + Interference)] × [W / R _req ] ---- (2)

Rewriting Equation (2) with respect to Rx _new is equal to Equation (3) below.

Rx _new = (Eb / Io) _req × R _req / W × (Total Noise + Interference) ---- (3)

Since "(Total Noise + Interference) = Rx _pilot / (Ec / Io)" in Equation (1), when this is substituted into Equation (3), the following Equation (4) is obtained.

Rx _new = (Eb / Io) _req × R _req / W × Rx _pilot / (Ec / Io) ---- (4)

In Equation (4), since the values of all the items on the right side are known, the minimum reception force Rx _new that the mobile station should receive can be obtained.

In addition, the forward link loss (Link Loss) is as shown in the following equation (5), and since the Rx _pilot / Tx _pilot is known, the link loss value can be obtained.

Link Loss = Rx _pilot / Tx _pilot = Rx _new / Tx _new ---- (5)

Finally, the minimum transmission power Tx _new to be allocated to the _{new call} is obtained by substituting the Rx _new value and the link loss value obtained based on Equation (4) into the Equation (5).

On the other hand, in the relation between Equation (4) and Equation (5), if Equation (4) is rewritten with respect to the minimum transmission power Tx _new , the following Equation (6) is obtained.

Tx _new = (Eb / Io) _req × R _req / W × Tx _pilot / (Ec / Io) ---- (6)

Since the values of all the items on the right side are known in Equation (4), the minimum transmit power value Tx _new on the left side can be obtained. Thus, when the minimum transmit power value is obtained based on Equation (6). In step S203, the Rx _pilot may not be received, and the link loss may not be obtained.

According to the exemplary embodiment of FIG. 2 described above, it is possible to prevent disconnection of an existing busy call that may occur while accepting a new call, and the fixed station 20 controls to make a call with minimum power when a new call is connected. As the call progresses, the mobile station 10 may request an increase in transmission speed, which requires additional power allocation, and thus, the fixed station 20 may additionally supply power in consideration of the margin of the current forward power. Can be.

However, even when the rock lock control is performed according to the exemplary embodiment of FIG. 2, there may be a case in which exhaustion of forward power that may be allocated may occur.

In other words, when the forward interference on the target cell is increased due to the acceptance of a new call in the neighboring cell, or when the link loss occurs more largely due to a change in the position of any mobile station in the target cell, the mobile station is sent to the fixed station. It may require additional allocation of power, thereby depleting the power resources that the fixed station can allocate in the forward direction. If you do not take this possibility into account when a new call occurs in advance, it is possible that the call you are currently accepting may not be guaranteed enough call pain by the new call currently accepted, and in the worst case, the call may be disconnected. .

The operator needs to set the threshold T _QoS of call disconnection probability according to the cell environment, meet the call type and call profile of the new call, and provide the minimum required power Tx calculated according to the embodiment of FIG. _The probability that the total forward power plus _new exceeds the maximum available power Tx _max during the average talk time according to the type of new call, accepts the call if it does not exceed the T _QoS , and rejects the call if it exceeds the implementation of FIG. 2. For example, it is possible to prevent the call quality degradation and / or call disconnection caused by power exhaustion after accepting the call.

However, it is difficult to calculate the probability by applying the above criteria as it is, and it is very inefficient to prevent the power shortage caused by the position movement of the mobile station, because the link loss is very large dynamic even in one cell. The possibility of call truncation could be reduced if it could fluctuate within the dynamic range and limiting the acceptance of new calls by considering all of these factors, but the power capacity to accommodate a call in one cell would be greatly reduced. Because it results.

Accordingly, the present invention provides a case in which forward power exhaustion occurs due to an increase in interference of neighboring cells. The call admission control method to prevent this is implemented as follows.

Each call on the current call requests the fixed station 20 to increase the power of a signal received by the mobile station 10 at the same rate as the increase rate of interference in order to maintain the same quality at the mobile station when interference increases. do. In FIG. 1, since the power allocated to all calls currently in the call is Tx _traffie and the limit to increase the maximum is "Tx _traffic + R", the maximum value of the possible power increase rate is "(Tx _traffic + R) / Tx _traffic ". Therefore, if interference by neighboring cells increases by more than "(Tx _traffic + R) / Tx _traffic " times, the depletion of allocable forward power occurs. Therefore, when a new call is accepted, the probability that the interference by neighboring cells is increased by "(Tx _traffic + R) / Tx _traffic " times more than the present time, and if the probability does not exceed the T _QoS , the call is accepted and exceeded. To reject the call.

Next, it will be described in more detail with reference to FIG.

3 is a flowchart illustrating a call admission control method in a CDMA network according to another embodiment of the present invention, in which the call admission control of FIG. 2 is performed in consideration of only the current power usage level and the spare power in the target cell. In addition to the control method, the call admission control method further considers interference of the neighboring cell to the target cell.

In FIG. 3, when a new call is accepted from a mobile station (MS) 10 to a fixed station (BS) 20 (Call Request Message) (S301), the fixed station 20 sends a pilot ( Pilot) signal is transmitted and a received measurement value for the pilot signal is requested (Pilot Measurement Request) (S302).

Subsequently, the mobile station 10 measures the average received power value Rx _pilot of the pilot signal and the energy-to-chip density ratio Ec / Io of the pilot signal to the fixed station 20 according to the request of the fixed station 20. Send (Send Pilot Measurement) (S303). The fixed station 20 receives the Rx _pilot and Ec / Io transmitted from the mobile station 10 and transmits the received power value Rx _pilot of the received pilot signal and correspondingly transmitted from the fixed station 20 itself. Based on the difference between the transmit power values (Tx _pilot ) of the pilot signal, that is, the forward link loss (Link Loss) is calculated based on Equation (5), and the current forward interference density based on Equation (1). (Interference) is obtained (S304).

The fixed station 20 may then request the mobile station 10 the desired type of call (data call or voice call), the minimum required transmission rate R _req , and the minimum required value of the energy-to-bit energy-to-interference density ratio [(Eb / Io). Call profile including the _req ] (Call Profile Request) (S305).

The mobile station 10 sends the desired profile of the call to the fixed station 20 according to the request (Send the Call Profile) (S306). The fixed station 20 assigns a minimum transmit power Tx _new to be allocated to the new call based on the profile of the call received from the mobile station 10 and the Ec / Io value and Rx _pilot value received and stored in step S303. The calculation process is the same as the calculation process in the embodiment of FIG. 2 described above (S307).

In addition, the fixed station 20 calculates the total talk channel power (Tx _traffie ) and the available remaining power amount (R) when it is assumed that the calculated minimum transmission power value (Tx _new ) is allocated to the _new call. A ratio "(Tx _traffic + R) / Tx _traffic " of the threshold power value (Tx _traffic + R) that can be raised to the maximum for the entire talk channel power (Tx _traffie ) is calculated (S308).

Next, in the present invention, if the fixed station 20 knows the amount of interference received by any mobile station, the distribution function for knowing the distribution of the received interference amount of the mobile station for a predetermined time after the current time point is statistically calculated and stored in advance. Statistical distribution function (probability characteristic) of the received interference amount of the mobile station for a predetermined time corresponding to the current interference density value (Interference) calculated in S304 and the maximum of the ratio calculated in step S308, that is, the possible power increase rate Based on the value "(Tx _traffic + R) / Tx _traffic ", the probability P of power depletion for the predetermined time is calculated as follows (S309).

For example, when the total talk channel power Tx _traffie is "1" and the available remaining power amount R is "0.2", the maximum value of the possible power increase rate is "1.2", and the current Is 0.5, the statistical distribution function of the received interference amount of the mobile station for a predetermined time (average talk time according to the type of call) corresponding to the interference density value, that is, the received interference amount of the currently known mobile station If the probability density function (PDF) is found as a distribution function that can know the distribution of the received interference amount of the mobile station for a certain time after the current time point from the above, and the probability density function graph is as shown in Fig. 4, the power depletion probability (P) Is the maximum of the possible power increase ratios from "0.5" which is the current interference density value (I) of the total area of the section which becomes more than the said current interference density value (I) formed with the said probability density function graph of FIG. Value of "1.2" as the increased interference density value (hereinafter abbreviated △ I LA), that is, "0.6 = 0.5 X 1.2" is the ratio (P) of the area occupied by the section becomes equal to or greater than a.

Further, the correlation between the increased interference density value ΔI and the ratio P (ie, power depletion probability) based on the probability density function PDF for the current interference density value I as shown in FIG. 4. Drawing a graph of a function representing, can be represented as shown in Figure 5a. Accordingly, after calculating the current interference density value I, the increased interference density value ΔI, and the power depletion probability probability P based on the function of FIG. 5A with accumulated statistics, As shown in FIG. 5B, the relationship between the values I, ΔI, and P is stored in a table, and when a new call is applied, the current interference density value I and the increased interference density value ΔI are processed through the above-described process. ), It is possible to immediately know the power depletion probability (P) that will be generated after allocating a call to the requested new call based on the previously stored table.

As described above, the step S309 is performed to calculate the power depletion probability P. Then, the power depletion probability P is finally compared with the service quality target threshold T _QoS (S310). As a result, if the probability of power exhaustion does not exceed the TQoS, the new call is accepted (Admit), and a channel assignment message is transmitted to the mobile station 10 (S311). Reject and transmits a reject notification message to the mobile station 10 (S312).

As described in detail above, the call admission control method in the CDMA network according to the present invention maintains the quality of a call currently being serviced above a predetermined criterion, maximizes the acceptability of a new call, and saves the data from a neighboring cell previously stored as statistical data. By controlling the call acceptance based on the interference distribution, it is possible to prevent the degradation of the call of the target cell due to the power increase in the neighboring cell after the call acceptance, and to determine the acceptance of the new call while guaranteeing the target call quality of service. There is an effect that can be used efficiently without wasting resources.

Claims (8)

A call control method in a fixed station through communication between a mobile station and a fixed station, Requesting measurement of a pilot signal from the mobile station when the mobile station is requested to accept a new call; Receiving a energy-to-chip energy-to-interference density ratio (Ec / Io) value of the pilot signal measured from the mobile station by the request; A third step of requesting the mobile station a profile of the call including the desired type of call, the minimum required transmission rate (R _req ), and the minimum required value of the energy per bit to interference density ratio ((Eb / Io) _req ]; A fourth step of calculating a minimum transmit power value to be allocated to the new call based on the profile of the call received from the mobile station by the request and the Ec / Io value received in the second step; And And a fifth step of comparing the calculated minimum transmission power value with the currently available forward transmission power value, and determining whether to accept the new call according to the comparison result. How to control the rock. The method of claim 1, The fourth step, The minimum transmission power value is calculated based on a formula of "minimum transmission power = [(Eb / Io) _req / (Ec / Io)] x (Tx _pilot ) x (R _req / W)", where Tx _pilot is The transmit power value of the pilot signal, W is the bandwidth control method in a code division multiple access network, characterized in that the bandwidth. The method of claim 1, The fourth step, Receive the received power value Rx _pilot of the pilot signal measured from the mobile station at the request of the first step, and based on the formula " Link loss = (Rx _pilot ) / (Tx _pilot ) " A lower first step of calculating a loss; The minimum received power value required by the mobile station is calculated based on a formula of "minimum received power = [(Eb / Io) _req / (Ec / Io)] x (Rx _pilot ) x (R _req / W)". Lower two levels; A third step of calculating the minimum transmission power value by multiplying the calculated minimum reception power value by an inverse of the calculated link loss value, Wherein Tx _pilot is a transmission power value of the pilot signal and W is a bandwidth. The method according to any one of claims 1 to 3, The call type is a rock lock control method in a code division multiple access network, characterized in that it comprises a data call and a voice call. A call control method in a fixed station through communication between a mobile station and a fixed station, Requesting measurement of a pilot signal from the mobile station when the mobile station is requested to accept a new call; Receiving the received power value Rx _pilot and the energy-to-chip energy-to-interference density ratio Ec / Io value of the pilot signal measured from the mobile station by the request, and receiving the received power value Rx _pilot of the received pilot signal and Correspondingly, a second step of calculating a forward link loss and an interference density based on a difference between transmit power values Tx _pilot of the corresponding pilot signal transmitted from the fixed station itself; A third step of requesting the mobile station a profile of the call including the desired type of call, the minimum required transmission rate (R _req ), and the minimum required value of the energy per bit to interference density ratio ((Eb / Io) _req ]; A fourth step of calculating a minimum transmit power value to be allocated to the new call based on the profile of the call received from the mobile station by the request and the value received and calculated in the second step; A fifth step of calculating total talk channel power (Tx _traffie ) and usable remaining power amount (R) when it is assumed that the calculated minimum transmission power value is allocated to the new call; A sixth step of calculating a ratio "(Tx _traffic + R) / Tx _traffic " of a threshold power value (Tx _traffic + R) that can be raised to the current maximum with respect to the total talk channel power (Tx _traffie ); The probability of power depletion occurring based on the statistical distribution function of the received interference amount of the mobile station for a predetermined time corresponding to the current interference density value calculated in the second step and the ratio value calculated in the sixth step Obtaining a seventh step; And an eighth step of comparing the obtained power exhaustion occurrence probability with a preset service threshold probability and determining whether to accept the new call according to the comparison result. Way. The method of claim 5, The statistical distribution function of the seventh step is obtained and stored using a calculation formula of probability density function (PDF), and the probability of occurrence of power depletion is equal to or greater than the current interference density value formed by the probability density function graph. Code division multiple access network, characterized in that the ratio of the area of the interval that is greater than the interference density value (ΔI) increased by the ratio calculated in the sixth step from the current interference density value; How to control lake rock in The method of claim 5, The predetermined time is a rock lock control method in a code division multiple access network, characterized in that the average call time according to the type of the call. The method of claim 5, In the fourth step, the minimum transmission power value is calculated based on a formula of "minimum transmission power = [(Eb / Io) _req / (Ec / Io)] x (Tx _pilot ) x (R _req / W)". _{Alternatively} , the link loss is calculated based on a formula of "link loss = (Rx _pilot ) / (Tx _pilot )", and "minimum received power = [(Eb / Io) _req / (Ec / Io)]. The minimum received power value required by the mobile station is calculated based on the formula × (Rx _pilot ) × (R _req / W) ", and the reciprocal of the calculated link loss value is converted to the calculated minimum received power value. Multiplying the minimum transmission power value, wherein W is a bandwidth;