Apparatus and method for reducing message collision between mobile stations simultaneously accessing a base station in a CDMA cellular communications system

• US 20060121897A1
• Filed: 01/09/2006
• Published: 06/08/2006
• Est. Priority Date: 03/05/1992
• Status: Abandoned Application

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tiedemann, Edward G. Jr., Padovani, Roberto, Weaver, Lindsay A. Jr.
• Application Number:
  US11/328,786
• Publication Number:
  US 20060121897A1
• Time in Patent Office: Days
• US Class Current: 455/434
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04B 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker
• CPC Class Codes: H04J 13/10 Code generation
• CPC Class Codes: H04J 13/16 Code allocation
• CPC Class Codes: H04L 1/188 Time-out mechanisms
• CPC Class Codes: H04L 1/1887 Scheduling and prioritising arrangements
• CPC Class Codes: H04W 52/48 during retransmission after error or non-acknowledgment
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment
• CPC Class Codes: H04W 74/002 Transmission of channel access control information
• CPC Class Codes: H04W 74/08 Non-scheduled access, e.g. ALOHA hybrid access H04W74/02
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access
• CPC Class Codes: H04W 74/0841 with collision treatment
• CPC Class Codes: H04W 74/0866 using a dedicated channel for access

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.

Claims

1. A method for an access request attempt of a communication station in a communication network, comprising:

sending a plurality of probe sequences to said communication station;

including in each of said probe sequences a plurality of probes; and

terminating said access request attempt if after said sending of any of said probes in any of said probe sequences an acknowledge message is received from said communication station.

2. The method as in claim 1 further including providing said plurality of probes with increasing power levels in each of said probe sequences.

3. The method as in claim 1 further including separating said probe sequences by random delays.

4. The method as in claim 1 further including separating said plurality of probes by random delays.

5. The method as in claim 1 further including sending said plurality of probe sequences through different access channels.

6. The method as in claim 1 further including abandoning said request for initial access request if after said sending of a predetermined number of said probe sequences no acknowledgement message is received from said communication station.

7. An apparatus in a communication network, comprising:

means for sending a plurality of probe sequences for an access request attempt to a communication station;

means for including in each of said probe sequences a plurality of probes having increasing power levels; and

means for terminating said access request attempt if after any of said probes in any of said probe sequences an acknowledge message is received from said communication station.

8. The apparatus as in claim 7 further including means for providing said plurality of probes with increasing power levels in each of said probe sequences.

9. The apparatus as in claim 7 further including means for separating said probe sequences by random delays.

10. The apparatus as in claim 7 further including means for separating said plurality of probes by random delays.

11. The apparatus as in claim 7 further including means for sending said plurality of probe sequences through different access channels.

12. The apparatus as in claim 7 further including means for abandoning said access request attempt if after a predetermined number of said probe sequences no acknowledgement message is received from said communication station.

13. Electrical signals transmitted via a carrier wave to a communication station in a communication system, said electrical signals comprising computer-readable instructions for:

sending a plurality of probe sequences for an access request attempt to said communication station;

including in each of said probe sequences a plurality of probes having increasing power levels; and

terminating said access request attempt if after said sending of any of said probes in any of said probe sequences an acknowledge message is received from said communication station.