KR20000060617A - Apparatus and method for call access of mobile station by selecting cdma channel - Google Patents

Abstract

PURPOSE: A mobile-station call access apparatus is provided to minimize the possibility of a mobile-station call access fail due to the degradation of wireless circumstance. CONSTITUTION: A mobile-station call access apparatus comprises a mobile station(100), a base station(200), a call processor(210), and first and second frequency allotting devices(220,230). The mobile station(100) tries to access a call. The base station(200) provides a plurality of CDMA channels which are capable of serving to the mobile station(100), and transmits a signal message associated with call setting through a mobile station-accessed channel. The call processor(210) controls a call process in the base station(200). The first and second frequency allotting devices(220,230) are connected to the call processor(210), and allot a frequency to the mobile station(100).

Description

{APPARATUS AND METHOD FOR CALL ACCESS OF MOBILE STATION BY SELECTING CDMA CHANNEL}

The present invention relates to a code division multiple access (CDMA) mobile communication system, and in particular, attempts to access a call by selecting an optimal access channel from a plurality of candidate access channels that can be set up, and fails the call access attempt. A call access apparatus and method of a CDMA communication system mobile station for switching an access channel to an access channel.

In a code division multiple access system, an idle state mobile station that does not make a call is tuned to the base station by receiving a probe signal through an access channel of the base station. A mobile station tuned to a base station can perform origination or reception on the paging channel of the base station. The process of retrieving a probe signal from a base station through an access channel is called an access attempt of the mobile station.

1 is a flow chart of a conventional access attempt. As shown in FIG. 1, when access is started (s101), the access CDMA channel (ACCH) is set to the calculated CDMA channel (Hashed CDMA Channel (HCCH)). s102), access is attempted (s103). When the access is first attempted, the base station sets the PROBE value and the SEQ value to 0 (s104). The probe signal is transmitted through the access CDMA channel (s105), and the mobile station waits for a response from the mobile station (s106).

If a response is received from the mobile station, the access is successful (s107). However, if there is no response, the PROBE value is increased by 1 to increase the power intensity of the probe signal by one step (s108), and the PROBE value is compared with NUM_STEP, which is a predetermined threshold (s109). As a result of the comparison, if the PROBE value is less than or equal to the NUM_STEP value, the process is performed again from (s105).

However, if the PROBE value exceeds the NUM_STEP value, the SEQ value is increased by 1 (s100), and the SEQ value is compared with the MAX_REQ_SEQ (or MAX_RESP_SEQ) value (s111). If the comparison results in the SEQ value exceeding the MAX_REQ_SEQ (or MAX_RESP_SEQ) value, the access is failed (s112). If not exceeded, restart from the step (s105) again.

As noted above, the base station incrementally increases the signal transmitted over the access channel, i.e., the probe signal, until it reaches a threshold, thereby allowing the mobile station to access the base station.

In a CDMA mobile communication system environment that conforms to the air interface standard for a CDMA mobile communication system, an idle state mobile station maintains a stable wireless environment by appropriately performing idle handoff according to the change of the wireless environment. However, once the call access attempt step is entered, no handoff is performed until the traffic channel is obtained.

Therefore, if the radio environment of the base station with which the mobile station is tuning is rapidly changed or the mobile station enters another adjacent base station while the mobile station attempts to access the call, the radio environment quality of the base station with which the mobile station is tuning is deteriorated and the call is accessed. The problem is that the chance of failing an attempt is increased.

In order to compensate for the problem caused by the impossibility of handoff in the above-mentioned call access, and to compensate for the problem of call access attempt failure that may occur while the mobile station moves between cell base stations between base stations, an "Access Handoff" Introduce the concept of The access handoff allows the mobile station to perform a handoff to a nearby base station in accordance with the change of radio environment in the call access attempt phase.

However, the access handoff may also be poor in pilot strength of an adjacent base station and thus may not perform access handoff, that is, an active pilot strength of a CDMA channel to which a mobile station is attempting to access a call, or access may be poor. Reliable call access in case of failure of base station forward link or reverse link such as inaccessibility due to channel failure or paging channel loss due to paging channel failure during call access attempt There was a problem that does not guarantee.

The present invention was devised to solve the problems of the prior art operating as described above, and to minimize the possibility of mobile station call access failure due to poor wireless environment in mobile station call access and to ensure more stable call access, An object of the present invention is to provide a call access apparatus and method for a mobile station through code division multiple access channel selection.

1 is a flow chart of a conventional access attempt.

2 is a radio environment diagram of a mobile station according to the present invention;

3 is an access attempt flow chart in accordance with the present invention.

4 is a flowchart of candidate access CDMA channel selection in accordance with the present invention.

5 is a flow diagram of an access CDMA channel selection in accordance with the present invention.

<Explanation of symbols for main parts of drawing>

100: mobile station 200: base station

210: call processing processor 220, 230: frequency allocation device

PROBE: Counter of Access Probe

NUM_STEP: Maxium of access probe sequence

SEQ: Counter of Access Attempt

MAX_REQ_SEQ: Maxium of access attempt sequence

ATTEMPT_SEQ_THRE SHOLD: Maximum threshold of access attempt sequence of a CDMA channel

CACCH: Candidate Access CDMA channel

P_ST: Pilot Strength

A preferred embodiment of a call access apparatus of a mobile station through code division multiple access channel selection according to the present invention, which is invented to achieve the above object,

At least one mobile station (100) attempting to access the call;

At least one base station (200) providing a plurality of CDMA channels serviceable to the mobile station and transmitting a call setup related signal message through a CDMA channel accessed by the mobile station;

A call processing processor 210 for controlling call processing in the base station; And

And a first and a second frequency allocation device (220) (230), which are connected to the call processing processor in the base station and assign a frequency to a mobile station.

A preferred embodiment of a call access method of a mobile station through code division multiple access channel selection according to the present invention,

Starting access (s201),

Selecting a CACCH (s202),

Selecting an ACCH after the CACCH selection (s203);

After the ACCH selection, attempting to access through the ACCH (s204),

Setting the PROBE value and the SEQ value to 0 for the access attempt (s205);

Transmitting a probe signal through the ACCH (s206),

Checking whether a response has been received (s207),

If a response is received, processing for access success (s208),

If no response is received, increasing the PROBE value by 1 (s209).

Comparing the PROBE value with a NUM_STEP value (s210);

If the PROBE value exceeds the NUM_STEP value, increasing the SEQ value by 1 (s211),

Comparing the SEQ value with a maximum value of an access attempt sequence (s212),

If the SEQ value exceeds the maximum value of the access attempt sequence, access failure processing (s213),

If not exceeding, comparing the SEQ value with a predetermined access attempt threshold for limiting the SEQ value (s214),

Selecting another CACCH as a new ACCH if the SEQ value exceeds the access attempt threshold (s215); and

If the ACCH is not equal to the HCCH, a step s216 of continuing access attempt is performed.

Another preferred embodiment of a call access method of a mobile station through code division multiple access channel selection according to the present invention is a method for responding to a call request or an incoming call of a mobile station in a wireless communication system using a code division multiple access technique. ,

The mobile station selecting a hash tuned CDMA channel from among a plurality of CDMA channels included in the most recently received CDMA channel list from the base station and tuning to the hash tuned CDMA channel;

Selecting among the remaining CDMA channels included in the CDMA channel list and not the hash tuned CDMA channel, CDMA channels whose pilot signal strength is greater than a predetermined call connectable pilot threshold;

Selecting a CDMA channel having the largest pilot strength among the selected CDMA channels as a candidate access CDMA channel (s202);

Comparing the pilot strength of the hash tuned CDMA channel with a predetermined call connectable pilot threshold;

Selecting the hash tuned CDMA channel as an optimal access channel if the pilot strength of the hash tuned CDMA channel is greater than a predetermined call connectable pilot threshold as a result of the comparison;

If the pilot strength of the hash tuned CDMA channel is not greater than a predetermined call connectable pilot threshold, whether the pilot strength of the candidate access CDMA channel is greater than the pilot strength of the hash tuned CDMA channel by a predetermined access pilot comparison threshold. Confirming;

If the pilot strength of the candidate access CDMA channel is greater than a pilot strength of the hash tuned CDMA channel by a predetermined access pilot comparison threshold, selecting the candidate access CDMA channel as an optimal access CDMA channel;

If the pilot strength of the candidate access CDMA channel is not greater than a pilot strength of the hash tuned CDMA channel by a predetermined access pilot comparison threshold, selecting the hash tuned CDMA channel as an optimal access CDMA channel;

Setting, by the base station, PROBE and SEQ for controlling access attempts of the mobile station to 0, and transmitting a probe signal through the selected access CDMA channel;

After transmitting the probe signal, determining that the access is successful when a response is received from the mobile station;

After transmitting the probe signal, if no response is received from the mobile station, increasing the PROBE by 1 and comparing the increased PROBE to a predetermined PROBE threshold;

If the comparison results in the increased PROBE not exceeding the PROBE threshold, returning to transmitting a probe signal on the selected access CDMA channel;

If the comparison results in the increased PROBE exceeding the PROBE threshold, increasing the SEQ by 1 and comparing the increased SEQ to a predetermined SEQ threshold;

If the comparison results in the increased SEQ not exceeding the SEQ threshold, returning to transmitting a probe signal over the selected access CDMA channel; And

And determining that the access fails if the increased SEQ value exceeds the SEQ threshold value.

According to the present invention, a candidate access CDMA channel (CACCH) is selected using a CDMA channel list of a base station and a call settable pilot threshold for a mobile station attempting to access a base station. Next, an optimal access channel is selected among the calculated CDMA channels tuned through the candidate access CDMA channel (CACCH) and the CDMA channel list hashing.

However, if the mobile station fails to access the call for a time corresponding to a predetermined access attempt threshold in the call access attempt, the access attempt is performed by switching the selected candidate access channel to an access channel.

Hereinafter, described in detail with reference to the accompanying drawings, preferred embodiments of the present invention.

FIG. 2 is a radio environment diagram of a mobile station according to the present invention. As shown in FIG. 2, at least one mobile station 100 attempting to access a call and a plurality of CDMAs capable of serving the at least one mobile station 100 are provided. At least one base station 200 capable of providing a channel and transmitting a signaling message relating to call establishment over a channel accessed by the at least one mobile station 100 and controlling call processing within the base station 200 It consists of a call processing processor 210 and the first and second frequency allocation device (220, 230) connected to the call processing processor 210 to allocate a frequency to the at least one mobile station 100, The operation and effects thereof will be described in detail with reference to FIGS. 2 to 5 as follows.

3 is a flowchart of an access attempt according to the present invention, FIG. 4 is a flowchart of selecting a candidate access CDMA channel (CACCH) according to the present invention, and FIG. 5 is a flowchart of selecting an access CDMA channel (ACCH) according to the present invention.

The base station 200 provides a plurality of serviceable CDMA channels, and transmits a list thereof to the mobile station 100 as a list of CDMA channels, thereby ensuring the tuning of the mobile station 100 for each CDMA channel. The mobile station 100 having received the CDMA channel list from the base station 200 hashes it to determine the CDMA channel (HCCH) to tune.

When a tuned CDMA channel (HCCH) is selected, the mobile station receives overhead information, which is control information of the base station, through the paging channel of the tuned base station. The update operation is performed and idle handoff is performed to the neighbor base station if necessary.

When an outgoing call setup request is made to an idle mobile station or an incoming call from the base station 200 is received, that is, when communication with the base station 200 is required, the mobile station 100 is in a system access state (system). access state). To this end, the mobile station updates the control information of the base station 200 with the latest information, and then performs an access attempt according to the control information provided by the base station 200 through an access parameter message.

In attempting to access the mobile station 100 in this method, it is necessary to perform two steps of prior work before first generating an access probe containing the access message of the base station 200.

The first step is to select the CACCH from the list of the last updated CDMA channel after the mobile station enters the system access state (s202), and the second step is to the step (s202) and the CDMA channel that the mobile station is currently tuning In step S203, an optimal access channel is selected from the selected CACCH.

Hereinafter, the step s202 will be described with reference to FIG. 4.

In step s306, the mobile station 100 arbitrarily sets the strength of the pilot signal for each of the CDMA channels specified in the most recently received CDMA channel list except for the HCCH currently tuned through hashing, and the arbitrarily set call access. Compare the possible pilot thresholds.

In step s308, the CDMA channel having the best pilot strength while satisfying the call accessible pilot threshold value among the CDMA channels to be compared is selected as the CACCH. In step s309, when there is no CDMA channel that satisfies the above comparison condition, CACCH becomes HCCH.

In this case, the call-accessible pilot threshold value may be provided through an access parameter message in the base station 200, use existing handoff control information T_ADD and T_DROP, or generate and manage a value by the mobile station 100 itself. The call accessible pilot threshold should be determined at a level that ensures good call access of the mobile station 100.

In addition, the step s203 will be described with reference to FIG. 5 as follows.

In step s402, the mobile station 100 compares the call-accessible pilot threshold with the pilot strength of the CDMA channel currently tuned through hashing, and if it meets the call-accessible pilot threshold, then selects the current hashing-tuned CDMA channel. Select as an access channel.

On the other hand, if the call accessible pilot threshold is not satisfied, in step s404 and s405, the mobile station 100 performs an optimal CDMA channel selection operation among the hashing tuned CDMA channel and the CACCH. In the optimal CDMA channel selection step, the mobile station 100 selects CDMA channels satisfying the following first and second conditions as access channels.

First condition

: Candidate_Access_CDMA_Ch! = Hashed_CDMA_Ch

Second condition

Candidate_Access_CDMA_Ch-hashed_CDMA_Ch> Access_Pilot_Comp.

In the second condition, the Access_Pilot_Comp prevents a phenomenon in which a call is concentrated on a specific CDMA channel to be satisfied in order for Candidate_Access_CDMA_Ch to be selected as an access channel.

That is, in order to attempt to access a call to another CDMA channel other than the CDMA channel hashed and tuned by the mobile station 100, the other CDMA channel satisfies the call access threshold value, and access_Pilot_Comp as much as the hashing tuned CDMA channel. The strength of the pilot should be large enough.

If Candidate_Access_CDMA_Ch satisfies the above first and second conditions, the Candidate_Access_CDMA_Ch is selected as an ACCH. If the above dates do not satisfy the above first and second conditions, the ACCH has an HCCH value.

If the access channel is selected through the two steps s202 and s203, in step s204, the mobile station 100 performs a call access attempt on the selected ACCH. At this time, the call access attempt is performed according to the access control information provided by the base station 200. In particular, the number of access probes for NUM_STEP is attempted by MSG_REQ_SEQ (or MSG_RESP_SEQ) according to NUM_STEP and MSG_REQ_SEQ (or MSG_RESP_SEQ).

When the access is attempted as described above, in step s214, the mobile station 100 compares the arbitrarily set connection attempt threshold value ATTEMPT_SEQ_THRESHOLD with the current connection attempt number SEQ.

If the number of access attempts exceeds the access attempt threshold (ATTEMPT_SEQ_THRESHOLD), in step s215, Candidate _Access_CDMA_Ch is selected as a new ACCH to continue access attempts. The access attempt threshold used in the above step has a value of MSG_REQ_SEQ (or MSG_RESP_SEQ) and may have any other value.

The mobile station 100 that has selected ACCH to CACCH during the call access attempt (s215) performs the remaining access attempts (2 * MAX_REQ_SEQ-ATTEMPT_SEQ_THRESHOLD or 2 * MAX_RESP_SEQ-ATTEMPT_SEQ_ THRESHOLD).

If there is no base station 200 response during the access attempt of MAX_REQ_SEQ or MAX_RESP_SEQ (s207) (s212), in step s213, the mobile station declares a call access attempt failure and transitions to the system decision state, and the call access attempt is Is terminated.

When the call access attempt of the mobile station 100 is received with respect to the call access attempt of the mobile station 100 performing the above steps, the call processing processor 210 of the base station 200 accesses the access channel accessed by the mobile station 100. It sends a response through the paging channel which is a pair of. As a result, the call processing processor 210 of the base station 200 processes a response to the call access attempt to another CDMA channel other than the HCCH tuned through hashing.

The overall flow of the above process is as follows. In the access attempt shown in Fig. 3, a candidate access CDMA channel (CACCH) is selected (s202) and an access CDMA channel (ACCH) is selected (s203) for the access attempt of the mobile station (s201). After performing step s202 and s203, the mobile station attempts to access through the access CDMA channel (ACCH) (s204). When the mobile station starts to attempt access, the base station sets the PROBE value and the SEQ value to 0 (s205), and transmits a probe signal on the access CDMA channel (ACCH) (s206).

Upon receiving a response from the mobile station by the transmission (s207), the base station processes the access success (s208). However, if the response is not received, the PROBE value is increased by 1 (s209), the PROBE value is compared with the NUM_STEP value (s210), and if the NUM_STEP value is not exceeded, the process is performed again from the step (s206).

However, if the PROBE value added with 1 exceeds the NUM_STEP value, the existing SEQ value is increased by 1 (s211), and the SEQ value is compared with the 2 * MAX_REQ_SEQ (or MAX_RESP_SEQ) value (s212). If the SEQ value exceeds 2 * MAX_REQ_SEQ (or MAX_RESP_SEQ) value, access failure is processed (s213). If not, the SEQ value is compared with the ATTEMPT_SEQ_THRESHOLD value (s214).

If the comparison results in that the SEQ value does not exceed the ATTEMPT_SEQ_THRESHOLD value, the process returns to the step s206. However, if the SEQ value exceeds the ATTEMPT_SEQ_THRESHOLD value, the candidate access CDMA channel (CACCH) is selected as a new access CDMA channel (ACCH) (s215) and the access attempt is continued.

At this time, the access CDMA channel (ACCH) is compared with the calculated CDMA channel (HCCH), and if the same step (s216), if not the access failure process (s213).

The candidate access CDMA channel selection process shown in FIG. 4 sets the selected CDMA channel (select_cdma_ch) and the candidate access CDMA channel (CACCH) to null, and the CDMA channel list (i) to 0 (s301). The CDMA channel select_cdma_ch is selected as the CDMA channel list i (s302).

The state of the selected CDMA channel (select_cdma_ch) is compared with null (s303), and if not null, the process returns to CACCH again (s304). However, if the state of the selected CDMA channel (select_cdma_ch) is null, the selected CDMA channel (select_cdma_ch) is compared with the HCCH, and if different, the existing CDMA channel list (i) is increased by 1 (s310), and again from step s302 Rerun

If the same in s305, P_ST (selected CDMA channel) is compared with a call accessible pilot threshold (access_pilot_threshold) (s306). As a result, if P_ST (the selected CDMA channel) does not exceed the call accessible pilot threshold (access_pilot_threshold), the step (s310) is performed, and if it exceeds, it is checked whether the CACCH state is null (s307).

If the CACCH state is null, P_ST (selected CDMA channel) is compared with P_ST (CACCH) (s308). As a result, if P_ST (the selected CDMA channel) does not exceed P_ST (CACCH), the process of step S310 is performed again.

However, if P_ST (the selected CDMA channel) exceeds P_ST (CACCH), that is, no CDMA channel satisfies the comparison condition, the CACCH becomes HCCH (s309). On the other hand, if it is not null in the step (s307) and performs the step of (s309).

The access CDMA channel selection flow shown in FIG. 5 selects the ACCH as HCCH (s401), and compares the P_ST (HCCH) with the call accessible pilot threshold (access_pilot_ threshold) (s402). If P_ST (HCCH) does not exceed the call-accessible pilot threshold, it is checked whether CACCH is null (s403), and if it is null, P_ST (HCCH) is excluded from P_ST (CACCH) for optimal CDMA channel selection. s404).

In addition, the difference between the excluded channel Diff_Pilot and the pilot strength for the HCCH (Access_Pilot_Comp) is compared (s405), and the difference between the excluded channel Diff_Pilot and the pilot strength for the HCCH (Access_Pilot_Comp) is not exceeded. Otherwise, ACCH is selected as the CACCH, CACCH is selected as the HCCH (s406), and then returned to ACCH (s407).

On the other hand, in (s402) P_ST (HCCH) exceeds the access pilot threshold (access_pilot_ threshold), the state of CACCH is not null in (s403), the channel (Diff_Pilot) excluded in (s405) is HCCH When the difference between the pilot strengths of the two values (Access_Pilot_Comp) is exceeded, the operation s407 is performed immediately.

As described in detail above, the present invention allows the mobile station to select an optimal access channel using the base station's CDMA channel list when attempting to access the mobile station, thereby increasing the call setup success rate of the mobile station and consequently improving the call quality. It works.

Claims (5)

At least one mobile station attempting to access the call; At least one base station providing a plurality of CDMA channels serviceable to the mobile station and transmitting call establishment related signal messages through a CDMA channel accessed by the mobile station; A call processing processor for controlling call processing in the base station; And And first and second frequency allocation devices coupled to the call processing processor within the base station for allocating frequencies to the mobile stations. Selecting a CACCH (candidate access CDMA channel) for attempting access; Selecting an ACCH (access CDMA channel) after the CACCH selection; After the ACCH selection, setting a value of PROBE (number of access probes) and SEQ (number of access attempts) to 0 in order to attempt access through the ACCH; After the setting, transmitting a probe signal through the ACCH; After the transmission of the probe signal, if the response is received, process access success, and if the response is not received, increasing the PROBE value by one; Comparing the PRONUM value with a predetermined NUM_STEP (maximum of access probe sequence) value for limiting the PROBE value, and increasing the SEQ value by 1 when the PROBE value exceeds the NUM_STEP value; The SEQ value is compared with a maximum value of a predetermined access attempt sequence for limiting the SEQ value, so that if the SEQ value exceeds the maximum value of the access attempt sequence, an access failure is handled; Comparing with a predetermined access attempt threshold for the purpose of limitation; And And if the SEQ value exceeds the access attempt threshold, selecting another CACCH as a new ACCH and continuing the access attempt. The method of claim 2, wherein selecting a CACCH to attempt the access comprises: Setting a CDMA channel and a CACCH to null and a CDMA channel list i to 0 in the CACCH selection process; After the setting, selecting the CDMA channel as a CDMA channel list (i) and confirming whether a state of the selected CDMA channel is null; Comparing the selected CDMA channel with HCCH (calculated CDMA channel) if the state of the selected CDMA channel is null, and comparing P_ST (pilot strength) (selected CDMA channel) with a call accessible pilot threshold if equal; Checking whether the CACCH state is null when the P_ST (selected CDMA channel) exceeds a call accessible pilot threshold; Comparing the P_ST (selected CDMA channel) and P_ST (CACCH) when the CACCH state is null; And And setting CACCH to HCCH if the P_ST (selected CDMA channel) exceeds P_ST (CACCH) as a result of the comparison. The method of claim 3, wherein selecting the ACCH comprises: Selecting an ACCH (access CDMA channel) as an HCCH and comparing a hashed_CDMA_ch (P_ST) with a call accessible pilot threshold value; Comparing the state of the CACCH if the hashed_CDMA_ch (P_ST) does not exceed the call accessible pilot threshold as a result of the comparison; Excluding P_ST (HCCH) from P_ST (CACCH) if the state of the CACCH is null; And Comparing a difference between pilot strengths of the excluded channel and the calculated CDMA channel; If the excluded channel does not exceed the difference in pilot strength for the calculated CDMA channel, selecting ACCH as CACCH, selecting CACCH as HCCH, and returning to the ACCH to access. Call access method of a mobile station through a CDMA communication system. A method for responding to a call request or an incoming call of a mobile station in a wireless communication system using code division multiple access technology, The mobile station selecting a hash tuned CDMA channel from among a plurality of CDMA channels included in the most recently received CDMA channel list from the base station and tuning to the hash tuned CDMA channel; Selecting among the remaining CDMA channels included in the CDMA channel list and not the hash tuned CDMA channel, CDMA channels whose pilot signal strength is greater than a predetermined call connectable pilot threshold; Selecting a CDMA channel having the largest pilot strength among the selected CDMA channels as a candidate access CDMA channel; Comparing the pilot strength of the hash tuned CDMA channel with a predetermined call connectable pilot threshold; Selecting the hash tuned CDMA channel as an optimal access channel if the pilot strength of the hash tuned CDMA channel is greater than a predetermined call connectable pilot threshold as a result of the comparison; If the pilot strength of the hash tuned CDMA channel is not greater than a predetermined call connectable pilot threshold, whether the pilot strength of the candidate access CDMA channel is greater than the pilot strength of the hash tuned CDMA channel by a predetermined access pilot comparison threshold. Confirming; If the pilot strength of the candidate access CDMA channel is greater than a pilot strength of the hash tuned CDMA channel by a predetermined access pilot comparison threshold, selecting the candidate access CDMA channel as an optimal access CDMA channel; If the pilot strength of the candidate access CDMA channel is not greater than a pilot strength of the hash tuned CDMA channel by a predetermined access pilot comparison threshold, selecting the hash tuned CDMA channel as an optimal access CDMA channel; Setting, by the base station, PROBE and SEQ for controlling access attempts of the mobile station to 0, and transmitting a probe signal through the selected access CDMA channel; After transmitting the probe signal, determining that the access is successful when a response is received from the mobile station; After transmitting the probe signal, if no response is received from the mobile station, increasing the PROBE by 1 and comparing the increased PROBE to a predetermined PROBE threshold; If the comparison results in the increased PROBE not exceeding the PROBE threshold, returning to transmitting a probe signal on the selected access CDMA channel; If the comparison results in the increased PROBE exceeding the PROBE threshold, increasing the SEQ by 1 and comparing the increased SEQ to a predetermined SEQ threshold; If the comparison results in the increased SEQ not exceeding the SEQ threshold, returning to transmitting a probe signal over the selected access CDMA channel; And And determining that the access has failed if the increased SEQ exceeds the SEQ threshold, wherein the call access method of the CDMA communication system mobile station through the CDMA channel selection.