Method and apparatus for tracking a communication signal in a wireless communication system

• US 5,987,016 A
• Filed: 11/04/1997
• Issued: 11/16/1999
• Est. Priority Date: 11/04/1997
• Status: Expired due to Term

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: He, Rong
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): Duong, Frank
• Application Number:
  US08/964,124
• Time in Patent Office: 742 Days
• Field of Search: 370/209, 370/320, 370/335, 370/342, 370/441, 375/200, 375/206, 375/347, 375/349, 375/367, 375/376
• US Class Current: 370/335
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 1/7117 Selection, re-selection, allocation or re-allocation of paths to fingers, e.g. timing offset control of allocated fingers
• CPC Class Codes: H04B 2001/70706 using a code tracking loop, e.g. a delay locked loop

Abstract

The method for tracking a mobile communication signal, which operates in a code division multiple access wireless communication system including an antenna (401), and a base site receiver (400) having at least two receiver tracking fingers (F1, F2), includes receiving at the antenna (401) a first multipath signal (119) arriving at an on-time pn-offset (706) with an associated advanced pn-offset value (704) and retard pn-offset value (702) and receiving at the antenna (401) a second multipath signal (107) arriving at an on-time pn-offset (712) with an associated advanced pn-offset value (710) and retard pn-offset value (708). The method further includes determining a spacing between the first multipath signal and the second multipath signal, and adjusting the at least two receiver tracking fingers based on the advanced pn-offset value of one of the multipath signals and the retard pn-offset value of the other multipath signal.

Claims

1. In a code division multiple access wireless communication system, the system including an antenna and a base site receiver for demodulating a plurality of multipath rays representing a mobile communication signal, the base site receiver including at least two receiver tracking fingers, a method for tracking the mobile communication signal comprising:

receiving at the antenna a first multipath signal arriving at a first pn-offset;

receiving at the antenna a second multipath signal arriving at a second pn-offset;

despreading the first multipath signal utilizing a third pn-offset value that is advanced in time from the first pn-offset; and

despreading the second multipath signal utilizing a fourth pn-offset value that is retarded in time from the second pn-offset.

2. The method according to claim 1, wherein the pn-offsets are measured in PN chips.

3. The method according to claim 2, wherein the third pn-offset value is 1/2 PN chip above the first pn-offset.

4. The method according to claim 3, wherein the fourth pn-offset value is 1/2 chip below the second pn-offset.

5. The method according to claim 1, wherein the step of despreading the first multipath signal further comprises the steps of:

receiving at a controller, a plurality of finger manager outputs comprising at least the the first pn-offset associated with the first multipath signal and the second pn-offset associated with the second multipath signal; and

establishing a time difference between the first and the second pn-offset forming an established time difference; and

despreading the first multipath signal utilizing a third pn-offset value that is advanced in time from the first pn-offset, wherein the advancement in time is based on the established time difference.

6. In a code division multipole access wireless communication system, the system including an antenna and a base site receiver for demodulating a plurality of multipath rays representing a mobile communication signal, the base site receiver including at least two receiver fingers, a method for tracking the communication signal comprising:

receiving at the antenna a first multipath signal arriving at a first pn-offset;

receiving at the antenna a second multipath signal arriving at a second pn-offset;

calculating by first delay lock loop associated with one of the at least two receiver fingers, a first advanced pn-offset value and a first retard pn-offset value associated with the first pn-offset;

calculating by a second delay lock loop associated with the other of the at least two receiver fingers, a second advanced pn-offset value and a second retard pn-offset value associated with the second pn-offset;

storing the first and second advanced pn-offset values and the first and second retard pn-offset values;

receiving and storing at the controller, a plurality of finger manager outputs, the plurality comprising at least the first pn-offset associated with the first multipath signal and the second pn-offset associated with the second multipath signal;

establishing, a time difference between the first pn-offset associated with the first multipath signal and the second pn-offset associated with the second multipath signal;

comparing the time difference to a predetermined time difference threshold;

retrieving a previous retard pn-offset value associated with the first multipath signal and a previous advanced pn-offset value associated with the second multipath signal if the time difference is less than the predetermined time difference threshold;

substituting the previous retard pn-offset value and the previous advanced pn-offset values in an operation of the first and second delay lock loop, forming a new adjusted on-time pn-offset location; and

tracking the mobile communication signal at the new adjusted on-time pn-offset location.

7. The method according to claim 6, wherein the pn-offsets are measured in PN chips.

8. In a code division multiple access wireless communication system, the system including a base site receiver for demodulating a plurality of multipath signals representing a mobile communication signal, the base site receiver including at least two receiver fingers, an apparatus for tracking the mobile communication signal comprising:

an antenna for receiving a first and second multipath signal associated with the mobile communication signal;

a searcher for determining a first pn-offset value of the first multipath signal and second pn-offset value of the second multipath signal;

a finger manager for providing the first pn-offset value to one of the at least two receiver fingers, and the second pn-offset value to a the other of the at least two receiver fingers;

a first delay lock loop associated with one of the at least two receiver fingers for calculating a third pn-offset value and a fourth pn-offset value associated with the first pn-offset value of the first multipath signal, and outputting an adjusted first pn-offset to a despreader; and

a second delay lock loop associated with the other of the at least two receiver fingers, for calculating a fourth pn-offset value and a fifth pn-offset value associated with the second pn-offset value, and outputting an adjusted second pn-offset to a despreader.