KR20010048443A - Call permissible control method - Google Patents

Abstract

PURPOSE: A method for controlling a call admission is provided to control an originating call and to supply a priority call service to a specific mobile station, and to control overload of a mobile communication system, by using a connection maintenance admission value delay. CONSTITUTION: A mobile communication system(102) decides whether a call is attempted from a mobile station(104). If so, the mobile communication system(102) decides whether an overload is sensed in a connection channel. If so, the mobile communication system(102) detects a connection parameter message transmitted from the mobile station(104). The mobile communication system(102) controls the call attempt on the basis of a parameter for call admission controlling included in the connection parameter message.

Description

Call admission control method {CALL PERMISSIBLE CONTROL METHOD}

The present invention relates to a mobile communication system, and more particularly, to a call admission control method using a call admission control parameter included in a connection parameter message in a mobile communication system.

Many communication systems have multiple transmitters that need to connect randomly to one or more receivers. A local area network is one example of such a multiple access system. Cell phone systems are also an example of a multiple access system. In such a system, if multiple transmitters attempt to transmit at the same time, the messages may interfere or collide with each other. The receiver cannot identify the message involved in the collision. Examples of multiple access protocols are Aloha and Slot Aloha. In the Aloha protocol, each transmitter can transmit a message at any time. If a transmitted message is found to have collided, the transmitter waits for a random delay time and retransmits the message. According to the method, a random delay is introduced to prevent the transmitter from retransmitting at the same time. CDMA is one of a number of technologies for facilitating communication in which a large number of system users exist. US 5,544, 196 discloses an apparatus and method for reducing message collisions between mobile stations simultaneously accessing a base station in a CDMA cellular communication system.

Accordingly, the present invention is to solve such a conventional problem, and the present invention provides a method that can variably control the call admission by using the call admission control parameters included in the connection parameter message in the mobile communication system. There is this.

The present invention to achieve the above object

(a) determining if there is a call attempt from the mobile station;

(b) determining whether an overload is detected in an access channel when there is a call attempt from the mobile station;

(c) detecting a connection parameter message sent from the mobile station when overload is detected on the access channel; And

and (d) controlling a call attempt for the mobile station based on a call admission control parameter included in the detected connection parameter message.

The parameter for call admission control preferably includes a connection sustain tolerance field for twelfth to fifteenth connection overload classes with different call admission ratios.

1 is a block diagram showing a mobile communication system and a mobile station for performing a call admission control method according to an embodiment of the present invention.

2 is a flowchart illustrating a call admission control method according to an embodiment of the present invention.

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102: mobile communication system 104: mobile station

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

When the mobile station is not using a talk channel, communication between the mobile station and the base station is through an access channel. All access channels use a special mode of 4800 bps. The message of the access channel contains information about call origination, call response, command and registration. One or more access channels are paired with all call channels, each access channel being distinguished by a different long pseudo-random code. The base station responds via a call channel message to the particular access channel signal. Similarly, the mobile responds to the call channel message via a corresponding access channel message.

The access channel is a random access scheme CDMA channel. When multiple mobile stations require simultaneous use of the access channel in response to a call channel, the transmitting mobile station may arbitrarily select an access channel from the available access groups, and may arbitrarily select a time sequence from the available pseudo-random time arrays. Unless two or more mobile stations select the same access channel and pseudo noise time arrangement, they can simultaneously receive the above transmitted signal. In order to prevent an excessive number of mobile stations from simultaneously requesting access, the base station controls the access channel transmission speed of the mobile station. If this multiple simultaneous transmissions occur, the energy-to-noise power spectral density per channel of the channel is degraded and the same access channel and pseudo-noise time sequence are used up, eventually exhausting the available processing resources of the base station. The control of the access channel is by means of a connection parameter message transmitted over the call channel. The transmission speed of the access channel can be changed depending on the transmission type and the mobile station class so that it can be used urgently for emergency or maintenance.

The mobile sets the mobile time to the system time via a sync channel message and then searches for the call channel. The call channel carries information from the base station to the mobile station via a message. There are four important messages: overhead, calls, commands, and channel assignments. The cellular system configuration may be different for various environments, and information about the system configuration is conveyed through four overhead messages. These overhead messages include system parameter messages, connection parameter messages, neighbor station list messages and CDMA channel list messages. System parameter messages consist of the configuration of the call channel, registration parameters, parameters for pilot signal acquisition, and the like. The access parameters contain information on the configuration of the access channel and the control parameters, some of which provide dynamic feedback to the mobile station to control the transmission speed of the mobile station so that the access channel can be stabilized. The neighbor station list message contains information of neighbor base stations related to handoff. This includes time deviations of pilot PN codes and configuration information of neighboring base stations. The CDMA channel list message contains information about the CDMA frequency assignment, including the calling channel, and the mobile station can immediately find the calling channel.

The call message has one or more mobile station call signals. When a signal from a mobile station calling a base station is received at the base station, the base station sends a call signal, which is usually sent to several base stations. Command refers to a wide range of messages used to control a particular mobile station, which is used extensively, from registration authentication to blocking transmission power of an abnormal mobile station. The channel assignment message may assign the talk channel of the base station to the mobile station, change the assigned call channel and switch the mobile station to use an analog FM system. The calling channel has a special mode called slot mode. In this mode, messages from specific mobile stations are only transmitted through the designated slots at a predetermined time. Through the registration procedure, the mobile station can designate a slot to be used by the base station. These slots occur at least once every 2 seconds up to every 128 seconds. The mobile station using the slot mode can reduce power by turning off the power at a time other than the designated slot. The mobile station may receive only some of the slots by command of the calling channel slot. Since the protocol can be used to inform the mobile station of the completion of transmission of the mobile station using the slot, the mobile station using the battery can greatly save the battery.

Hereinafter, a call admission control method according to an embodiment of the present invention will be described with reference to FIG. 2 is a flowchart illustrating a call admission control method according to an embodiment of the present invention.

In step S201, the mobile communication system 102 determines whether there is a call attempt from the mobile station 104. (The connection between the mobile communication system 102 and each mobile station is omitted in FIG. 1 to avoid confusion in the description. But such connections are included)

As a result of the determination in step S201, when there is no call attempt from the mobile station 104, the processing routine returns to step S201. On the contrary, when it is determined that there is a call attempt from the mobile station 104, the mobile communication system 102 determines whether overload is detected in the access channel (S202).

As a result of the determination in step S202, when no overload is detected in the access channel, the processing routine returns to step S202. Alternatively, if it is determined that overload is detected in the access channel, the mobile communication system 102 detects a connection parameter message sent from the mobile station 104 (step S203).

When delivering a connection parameter message to a base station (not shown) via an access channel, the connection parameter message forms a parameter used by the mobile station 104. When the base station sends a connection parameter, the base station uses a variable length message format as shown in Table 1 below. MSG_TYPE is a message format field, and the base station sets the MSG_TYPE field to '00000010'. PILOT_PN is a pilot PN sequence offset index field, and the base station sets the PILOT_PN field to the pilot PN sequence offset for the base station in units of 64 PN chips. ACC_MSG_SEQ is a connection parameter message sequence number field, and the base station sets the ACC_MSG_SEQ field to ACC_MSG_SEQ. ACC_CHAN is the number of access channels, and the base station sets the ACC_CHAN field to one less than the number of access channels associated with the call channel. NOM_PWR is a nominal transmit power offset field, and the base station sets the NOM_PWR field to a correction factor to be used by mobile stations in the open loop power estimate. INIT_PWR is the initial power offset for the connection, and the base station sets the INIT_PWR field to a correction factor to be used by the mobile stations in the initial transmission open loop power estimate over the access channel.

field Length (bits) MSG_TYPE ('00000010') 8 PILOT_PN 9 ACC_MSG_SEQ 6 ACC_CHAN 5 NOM_PWR 4 INIT_PWR 5 PWR_STEP 3 NUM_STEP 4 MAX_CAP_SZ 3 PAM_SZ 4 PSIST (0-9) 6 PSIST (10) 3 PSIST (11) 3 PSIST (12) 3 PSIST (13) 3 PSIST (14) 3 PSIST (15) 3 MSG_PSIST 3 REG_PSIST 3 PROBE_PN_RAN 4 ACC_TMO 4 PROBE_BKOFF 4 BKOFF 4 MAX_REQ_SEQ 4 MAX_RSP_SEQ 4 AUTH 2 RAND 0 or 32 RESERVED 7

PWR_STEP is a power increment field, and the base station sets the PWR_STEP field to its value by causing the mobile stations to increase the transmission power between successive access probes in a connection probe sequence in dB. NUM_STEP is a number field of access probes, and the base station sets the NUM_STEP field to one less than the maximum number of access probe mobile stations to be transmitted in a single access probe sequence. MAX_CAP_SZ is a maximum access channel message capsule dimension field, and the base station sets the MAX_CAP_SZ field to a value in the range of 0 to 7, which is 3 less than the maximum number of access channel frames in the access channel message capsule. PAM_SZ is an access channel preamble length field, and the base station sets the PAM_SZ field to one less than the number of access channel frames so that the mobile station is transmitted in each access channel preamble.

PSIST (0-9) can be changed by the access channel overload control function as a connection sustained allowance for a mobile station having a connection overload rating of 0 to 9. The mobile station 104 using the test overload class 10 and the emergency overload class 11 using the PSIST 10 and the PSIST 11, respectively, is not affected by the delay for the call attempt regardless of the PSIST 0-9. According to the embodiment of the present invention, the connection persistence allowance PSIST 12-15 for the twelfth to fifteenth connection overload classes operates distinctly from the PSIST (0-9), the PSIST (10), and the PSIST (11). The PSIST 12-15 has a different call admission ratio or sets a value for a special purpose mobile station and performs the function of a parameter for call admission control. Accordingly, the call limiting / blocking function operates according to the PSIST (12-15) value transmitted from the mobile station in the mobile telephone system, and the mobile station according to the present invention is distinguished from the general mobile station so that call admission is continued to provide priority call function. . For example, in the mobile station according to the present invention, the PSIST 12, the PSIST 13, the PSIST 14, and the PSIST 15 may have 60, 70, 80, and 90 allowances, respectively.

In step S204, the mobile communication system 102 controls the call attempt to the mobile station 104 based on the call admission control parameter included in the detected connection parameter message. That is, the mobile communication system 102 transmits a response connection parameter message to the mobile station 104 via the call channel according to the call admission control parameter to adjust the delay of the call attempt for the mobile station 204.

As described above, the present invention utilizes a connection sustain tolerance delay to provide call calling restriction / blocking and preferential call service for a particular mobile station. The present invention also controls the overload of the mobile communication system by implementing the automatic access channel overload control function in the CDMA scheme utilizing the access channel occupancy and access sustained tolerance delay.

While the invention has been shown and described with respect to certain preferred embodiments thereof, the invention is not limited to the embodiments described above, but in the field to which the invention pertains without departing from the spirit of the invention as claimed in the claims. Any person with ordinary knowledge will be able to make various modifications.

Claims (2)

(a) determining if there is a call attempt from the mobile station; (b) determining whether an overload is detected in an access channel when there is a call attempt from the mobile station; (c) detecting a connection parameter message sent from the mobile station when overload is detected on the access channel; And (d) controlling a call attempt for the mobile station based on a call admission control parameter included in the detected connection parameter message. 2. The method of claim 1, wherein the parameter for call admission control comprises a connection duration tolerance field for twelfth to fifteenth connection overload classes having different call admission ratios.