Cell search method for multi-mode telecommunication apparatus, such apparatus, and computer program for implementing the method

• US 8,744,438 B2
• Filed: 11/27/2008
• Issued: 06/03/2014
• Est. Priority Date: 11/29/2007
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Lindoff, Bengt, Nilsson, Johan, Palenius, Torgny
• Primary Examiner(s): PATEL, MAHENDRA R
• Application Number:
  US12/745,259
• Publication Number:
  US 20110034168A1
• Time in Patent Office: 2,014 Days
• Field of Search: 455/434, 455436-444, 455/552.1, 455/428, 370/329, 370/203, 370/335, 709/217
• US Class Current: 455/434
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• CPC Class Codes: H04J 11/0086 Search parameters, e.g. search strategy, accumulation length, range of search, thresholds code acquisition in DSSS H04B1/7075
• CPC Class Codes: H04L 27/0012 arrangements for identifying the type of modulation
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface
• CPC Class Codes: H04W 36/24 Reselection being triggered by specific parameters

Abstract

A cell search method for a multi-mode telecommunication apparatus is disclosed. The method comprises receiving signals present in a frequency range; transforming received signals into frequency domain; estimating power spectral density from transformed signals; estimating probability of different communication modes by correlating the estimated power spectral density with power spectral density signatures of said different communication modes; and performing cell search according to estimated most probable communication mode. Such an apparatus and a computer program for performing the method are also disclosed.

Claims

1. A cell search method for a multi-mode telecommunication apparatus, the method comprising:

receiving signals present in a frequency range;

transforming received signals into frequency domain;

estimating power spectral density from transformed signals;

estimating probability of different communication modes by correlating the estimated power spectral density with power spectral density signatures of said different communication modes;

performing cell search according to estimated most probable communication mode;

ranking said different communication modes according to their estimated probability;

if no cell search match is found on the most probable communication mode, performing cell search for the other different communication modes in order of decreasing probability; and

basing performance of the method on a comparison of a received signal strength indicator, RSSI, with a predetermined threshold.

2. The method according to claim 1, wherein said estimation of power spectral density from transformed signals comprises averaging over a time corresponding to a predetermined number of expected symbols for any of the communication modes.

3. The method according to claim 2, wherein said estimation of power spectral density from transformed signals further comprises averaging over a predetermined number of expected carriers for any of the communication modes.

4. The method according to claim 1, further comprising determining the RSSI for the received signals.

5. The method according to claim 4, further comprising wherein basing performance of the method on a comparison of the received RSSI with the predetermined threshold comprises:

continuing the receiving of signals, if the RSSI is below a predetermined threshold, until the RSSI becomes above the predetermined threshold before performing said transforming, estimating power spectral density, estimating probability, and cell searching.

6. The method according to claim 4, further comprising determining frequencies holding peaks of power, wherein said correlation of estimated power spectral density with power spectral density signatures of said different communication modes is performed for frequency values on and in vicinity of said frequencies holding peaks of power.

7. The method according to claim 6, wherein said cell search according to estimated most probable communication mode is performed on and in vicinity of said frequencies holding peaks of power.

8. A multi-mode telecommunication apparatus comprising:

a radio receiver arranged to receive signals present in a frequency range;

a transformer means arranged to transform signals received by the radio receiver into frequency domain;

a power spectral density estimator arranged to estimate power spectral density of signals transformed by the transformer;

a probability estimator arranged to estimate probability of different communication modes, said probability estimator comprising a correlator arranged to correlate the estimated power spectral density with power spectral density signatures of said different communication modes;

a plurality of cell searchers, each arranged to perform cell searching for a communication mode; and

a controller arranged to assign the one of said plurality of cell searchers to perform cell search according to the estimated most probable communication mode,

wherein the controller is further arranged to;

rank said different communication modes according to their estimated probability;

if no cell search match is found on the most probable communication mode, assign another of said plurality of cell searchers to perform cell search for another of the different communication modes in order of decreasing probability; and

base operation of the controller on a comparison of a received signal strength indicator, RSSI, with a predetermined threshold.

9. The apparatus according to claim 8, wherein said power spectral density estimator comprises averaging means arranged to provide an average over a time corresponding to a predetermined number of expected symbols for any of the communication modes.

10. The apparatus according to claim 9, wherein said averaging means further is arranged to average over a predetermined number of expected carriers for any of the communication modes.

11. The apparatus according to claim 8, further comprising RSSI determination means arranged to provide RSSI for the received signals.

12. The apparatus according to claim 11, wherein the controller is arranged to control the receiving of signals to continue, if the RSSI is below a predetermined threshold, until the RSSI becomes above the predetermined threshold before activating said transformer, power spectral density estimator, probability estimator, and any of the cell searchers.

13. The apparatus according to claim 11, wherein the controller is further arranged to determine frequencies holding peaks of power, such that said correlator is controlled to perform said correlation of estimated power spectral density with power spectral density signatures of said different communication modes for frequency values on and in vicinity of said frequencies holding peaks of power.

14. The apparatus according to claim 13, wherein said assigned cell searcher controlled to perform cell searching according to estimated most probable communication mode is controlled to perform cell searching on and in vicinity of said frequencies holding peaks of power.

15. A non-transitory computer readable storage medium having stored therein instructions, which when executed by a processor cause the processor to perform a cell search method for a multi-mode telecommunication apparatus, the method comprising:

receiving signals present in a frequency range;

transforming received signals into frequency domain;

estimating power spectral density from transformed signals;

estimating probability of different communication modes by correlating the estimated power spectral density with power spectral density signatures of said different communication modes;

performing cell search according to estimated most probable communication mode;

ranking said different communication modes according to their estimated probability;

if no cell search match is found on the most probable communication mode, performing cell search for the other different communication modes in order of decreasing probability; and

basing performance of the method on a comparison of a received signal strength indicator, RSSI, with a predetermined threshold.