Apparatus and method for reducing message collision between mobile stations simultaneously accessing a base station in a CDMA cellular communications system
First Claim
1. A method of reducing message collisions between transmitted messages in a communication network, the method comprising:
- determining whether an access attempt is an access channel request;
performing a persistence test for an access channel slot if the access attempt is an access channel request; and
transmitting a first access probe of an access probe sequence in the slot if the persistence test passes.
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Abstract
Collisions between messages simultaneously transmitted by multiple spread-spectrum transmitters are reduced by distributing the transmissions over the available resources of the receiver. Each mobile station in a CDMA system uses one or more randomization methods to distribute its transmissions. In the first randomization, the mobile station time-delays its transmissions by a number of chips of the PN code with which it spreads the transmitted signal. In a second randomization, the mobile station randomly selects the PN code. In a third randomization, the mobile station inserts a random delay between successive message transmissions or probes if it does not receive an acknowledgement after a predetermined timeout period. A predetermined number of such transmissions is called a probe sequence. In a fourth randomization, the mobile station inserts a relatively long random delay between successive probe sequences if it does not receive an acknowledgement of any probe in the sequence.
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Citations
12 Claims
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1. A method of reducing message collisions between transmitted messages in a communication network, the method comprising:
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determining whether an access attempt is an access channel request;
performing a persistence test for an access channel slot if the access attempt is an access channel request; and
transmitting a first access probe of an access probe sequence in the slot if the persistence test passes. - View Dependent Claims (2, 3, 4)
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5. A mobile station apparatus, comprising:
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means for determining whether an access attempt is an access channel request;
means for performing a persistence test for an access channel slot if the access attempt is an access channel request; and
means for transmitting a first access probe of an access probe sequence in the slot if the persistence test passes. - View Dependent Claims (6, 7, 8)
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9. A computer readable medium embodying a method of reducing message collisions between transmitted messages in a communication network, the method comprising:
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determining whether an access attempt is an access channel request;
performing a persistence test for an access channel slot if the access attempt is an access channel request; and
transmitting a first access probe of an access probe sequence in the slot if the persistence test passes. - View Dependent Claims (10, 11, 12)
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Specification