Apparatus for searching multipath in spread spectrum communications system and method thereof

• US 20030103555A1
• Filed: 08/01/2002
• Published: 06/05/2003
• Est. Priority Date: 11/30/2001
• Status: Active Grant

• Current Assignee: Uniloc 2017 LLC (SoftBank Group Corp.)
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Han, Kyungtae, Kim, Kyung-Soo, Eo, Ik-Soo, Jung, Hee-Bum
• Granted Patent: US 7,194,018 B2
• Time in Patent Office: Days
• US Class Current: 375/147
• CPC Class Codes: H04B 1/7113 Determination of path profile
• 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

Abstract

A multipath searching apparatus for searching a short-delay multipath in a spread spectrum communications system and a method thereof are provided. The multipath searching apparatus has a radio front-end for converting a received radio signal into a baseband signal and outputting the baseband signal; a profile calculating unit for calculating and outputting the multipath profile of the baseband signal; a first detector for determining whether or not the radio signal traveled along a multipath having a short-delay path by comparing the peak value of the multipath profile with a profile value of a position which is a predetermined time interval before or after the peak of the multipath profile; a path selector for receiving the multipath profile and the detection result of the first detector, generating time delay information for each path, and separating a plurality of paths along which the radio signal traveled; and a receiving unit for receiving the time delay information of the paths, despreading the baseband signal, and combining despread signals. According to the apparatus and method, different paths in a channel having a short-delay path which can occur in indoor or urban environment can be separated and received energy can be gathered so that the performance of the receiver can be improved.

Claims

1. A multipath searching apparatus comprising:

a radio front-end for converting a received radio signal into a baseband signal and outputting the baseband signal;

a profile calculating unit for calculating and outputting the multipath profile of the baseband signal;

a first detector for determining whether or not the radio signal traveled along a multipath having a short-delay path by comparing the peak value of the multipath profile with a profile value of a position which is a predetermined time interval before or after the peak of the multipath profile;

a path selector for receiving the multipath profile and the detection result of the first detector, generating time delay information for each path, and separating a plurality of paths along which the radio signal traveled; and

a receiving unit for receiving the time delay information of the paths, despreading the baseband signal, and combining despread signals.

2. The apparatus of claim 1, wherein the profile calculating unit calculates a power profile based on the power of the radio signal.

3. The apparatus of claim 1, wherein the first detector comprises:

a power delay profile unit for storing a first power profile of a multipath signal having a short-delay;

a correlator for outputting a resulting value with respect to the correlation between the multipath profile and the first power profile; and

a comparator for determining that the signal traveled along a multipath having a short-delay path if the resulting value is greater than a predetermined threshold.

4. The apparatus of claim 1, wherein the first detector comprises:

a first delay searching unit and a third delay searching unit, each for outputting a power profile value at a position which is a predetermined time interval before or after the peak of the multipath power profile of the received signal;

a second delay searching unit for reducing the peak value of the multipath power profile of the received signal to a predetermined value and outputting the reduced value as a first peak value; and

a second comparator for determining whether the received signal traveled along a multipath having a short-delay path by using the output values of the first delay searching unit through the third delay searching unit.

5. The apparatus of claim 4, wherein the first delay searching unit obtains a power profile value at a position 0.5 chips after the peak of the multipath power profile of the received signal and the third delay searching unit obtains a power profile value at a position 0.5 chips before the peak of the multipath power profile of the received signal

6. The apparatus of claim 4, wherein the second comparator determines that the signal traveled along a multipath having a short-delay path if the output values of the first and third delay searching units are greater than the first peak value.

7. The apparatus of claim 1, wherein the path selector obtains time delay information of the radio signal from the multipath power profile.

8. The apparatus of claim 7, wherein if it is determined that the received signal traveled along a short-delay path, the path selector allocates time delay information elements of positions predetermined time interval before and after the peak of the power profile to the receiving unit

9. The apparatus of claim 7, wherein when the time delay information is allocated to the receiving unit, the path selector allocates the time delay information element of a position 0.5 chips before the peak and the time delay information element of a position 0.5 chip time after the peak, to the receiving unit.

10. A multipath searching method comprising the steps of:

(a) converting a received signal into a baseband signal and outputting the baseband signal;

(b) obtaining a multipath profile based on the power of the baseband signal;

(c) determining whether or not the received signal traveled along a multipath having a short-delay path by using the multipath profile, generating time delay information for each path by using the profile and the multipath having a short-delay, and selecting a path; and

(d) receiving the time delay information of the paths, despreading the baseband signal, combining the signals and outputting the combined result.

11. The method of claim 10, wherein step (c) comprises the steps of:

(c1) comparing the peak value of the multipath profile with a predetermined threshold;

(c2) determining that the signal traveled along a multipath having a short-delay path if the peak value is greater than the predetermined value; and

(c3) if the result of determination in step (c2) indicates that the signal traveled along a multipath having a short-delay path, separating the signals into two signals corresponding to two paths and allocating the two paths to a Rake receiver.

12. The method of claim 11, wherein step (c3) further comprises a step for generating time information of a position a predetermined time interval before or after the peak.

13. The method of claim 12, wherein the predetermined time is ±

0.5 chip time.

14. A computer readable recording medium having embodied thereon a computer program for the method of claim 10.