Method for transmitting pilot channels and a cellular radio system

• US 6,415,163 B1
• Filed: 01/24/1997
• Issued: 07/02/2002
• Est. Priority Date: 05/24/1995
• Status: Expired due to Term

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Telecommunications Oy (Nokia Corporation)
• Inventors: Muszynski, Peter, Keskitalo, Ilkka, Laiho-Steffens, Jaana
• Primary Examiner(s): VO, NGUYEN THANH
• Application Number:
  US08/776,263
• Time in Patent Office: 1,985 Days
• Field of Search: 455/422, 455/432, 455/433, 455/436, 455/437, 455/438, 455/442, 455/456, 455/522, 455/440, 455/443, 455/450, 455/561, 455/562, 370/320, 370/335, 370/441, 370/491
• US Class Current: 455/562.1
• CPC Class Codes: H04B 1/76 Pilot transmitters or receivers for control of transmission or for equalising
• CPC Class Codes: H04B 7/022 Site diversity; Macro-diversity using two or more spaced independent antennas H04B7/04
• CPC Class Codes: H04B 7/0491 using two or more sectors, i.e. sector diversity
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04W 16/28 using beam steering
• CPC Class Codes: H04W 48/12 using downlink control channel

Abstract

A cellular radio system and a method for transmitting pilot channels in a cellular radio network includes, in each cell, at least one base station communicating with mobile stations located within its area. The base stations transmit a data signal in the downlink direction by using transmission directions that change in time and which transmit information about the system to the mobile stations on control channels. In order to enable the most efficient use of the pilot channels, the base stations transmit at least one first pilot channel with a predetermined radiation pattern and second pilot channels on transmission directions that change in time. The predetermined radiation pattern determines the cell coverage area.

Claims

1. A method for transmitting pilot signals in a cellular radio network, having in each cell, at least one base station configured to communicate with mobile stations located within its coverage area, the communication including (i) transmitting at least one data signal in a downlink direction using transmission directions that change in time, and (ii) transmitting information about the network to said mobile stations on control channels, said method comprising:

said at least one base station transmitting at least one first pilot signal to all mobile stations within the cell, said pilot signal having a predetermined radiation pattern, said radiation pattern defining the coverage area, and

said at least one base station transmitting a second pilot signal in said transmission directions that change in time,

wherein said second pilot signal is incapable of carrying control information, and

wherein said at least one data signal and said second pilot signal are transmitted using matching radiation patterns.

2. The method as claimed in claim 1, wherein said mobile stations use power measured from said first pilot channel transmitted having said predetermined radiation pattern to facilitate a handover.

3. The method as claimed in claim 1, wherein said mobile stations use said received second pilot channel as phase references in coherent reception of said at least one data signal.

4. The method as claimed in claim 1, wherein

said base station receives a signal from one of said mobile stations through an antenna group, said antenna group comprising a plurality of antennas,

incoming directions and delays of signal components are searched for in said signal, and

when said at least one data signal is transmitted from said base station to said one mobile station, said radiation pattern is formed based on a power measurement of said signal.

5. The method as claimed in claim 4, wherein said one mobile station transmits to said base station information about a number, a power level, and a relative delay of a plurality of components of said at least one data signal received at said one mobile station, and said information is used by said base station to form said radiation pattern of said signal to be transmitted to said one mobile station.

6. The method as claimed in claim 1, wherein said predetermined radiation pattern has an omnidirectional form.

7. The method as claimed in claim 1, wherein, when said predetermined radiation pattern is transmitted, a higher transmit power is used than on channels using traffic channels.

8. The method as claimed in claim 1, wherein, when said predetermined radiation pattern is received, a larger processing gain is used than on channels using traffic channels.

9. The method as claimed in claim 1, wherein radiation patterns used in said transmission directions that change in time have a substantially beam-like shape.

10. A cellular radio system comprising:

in each cell, at least one base station configured to communicate with mobile stations located within its coverage area, the communication including (i) transmitting information about said system to said mobile stations using control channels, and (ii) transmitting at least one data signal to said mobile stations using radiation patterns that change in time,

wherein said at least one base station is configured to transmit at least one first pilot signal to all mobile stations within the cell, said pilot signal having a predetermined radiation pattern, said predetermined radiation pattern defining the coverage area for said cell,

wherein said at least one base station is configured to transmit a second pilot signal in said transmission directions that change in time and said second pilot signal being incapable of carrying control information, and

wherein said at least one data signal and said second pilot signal are transmitted using matching radiation patterns.

11. The cellular radio system as claimed in claim 10, wherein said base station comprises a transmitter which transmits said second pilot channel in the same transmission direction as said at least one data signal.

12. A cellular radio system comprising:

in each cell, at least one base station configured to communicate with mobile stations located within its coverage area, the communication including (i) transmitting information about said system to said mobile stations using control channels, and (ii) transmitting at least one data signal to said mobile stations using transmission directions that change in time,

wherein said at least one base station is configured to transmit at least one first pilot signal to all mobile stations within the cell, said pilot signal having a predetermined radiation pattern, said predetermined radiation pattern defining the coverage area for said cell,

wherein said at least one base station is configured to transmit a second pilot signal in said transmission directions that change in time, said at least one data signal and said second pilot signal are transmitted using matching radiation patterns, and said second pilot signal is incapable of carrying control information, and

wherein said base station comprises;

at least one antenna group, said antenna group including a plurality of antennas,

a group of radio-frequency units connected to said antenna group,

at least one channel unit, an input of said channel unit being configured to receive signals from said radio-frequency units, said channel unit comprising a phaser configured to phase said at least one data signal to be transmitted and received with said antenna group so that a gain obtained from said antenna group is largest in a desired direction,

a control unit configured to control said channel unit,

a separator configured to separate data containing connection quality information from the signals received by each mobile station, and

a baseband unit connected to the output of said channel unit, said channel unit further comprising;

a searcher configured to search for incoming directions and delays of best signal components received from said mobile stations, and

a controller configured to control formation of radiation patterns used when transmitting said at least one data signal from said base station to said mobile station based on a power measurement of said at least one data signal and said connection quality information received from said mobile station.

13. The cellular radio system as claimed in claim 12, wherein each said channel unit further comprises

an encoder which encodes said at least one data signal to be transmitted,

at least one transmission block, an input of said transmission block comprising a signal obtained from said encoder, and

at least one searcher block, an input of said searcher block comprising a signal obtained from said radio-frequency units.

14. The cellular radio system as claimed in claim 13, wherein said searcher block comprises

a phaser, an input of said phaser is a signal obtained from said radio-frequency units,

a detector which detects whether a signal obtained from said phaser and received from a certain incoming direction comprises the desired signal component having a certain delay and which measures the power of said signal component,

a measurer which measures desired incoming directions and delays of said signal to be received, and

an informer which informs said controller of a corresponding channel unit of said incoming direction, delay and power of each detected signal component.

15. The cellular radio system as claimed in claim 13, wherein said transmission block comprises

a modulator, having an input and an output wherein said input of said modulator is a signal obtained from said encoder,

a phaser, an input of said phaser is a signal visible at said output of said modulator, and

a controller which controls said phaser so that said largest gain of said at least one data signal to be transmitted is set in said desired direction.

16. A cellular radio system comprising:

in each cell, at least one base station configured to communicate with mobile stations located within its coverage area, the communication including (i) transmitting information about said system to said mobile stations using control channels, and (ii) transmitting at least one data signal to said mobile stations using transmission directions that change in time,

wherein said at least one base station transmits at least one first pilot signal to all mobile stations within the cell, said pilot signal having a predetermined radiation pattern, said predetermined radiation pattern defining the coverage area for said cell,

wherein said at least one base station is configured to transmit a second pilot signal in said transmission directions that change in time and said second pilot signal is incapable of carrying control information,

wherein said at least one data signal and said second pilot signal are transmitted using matching radiation patterns, and

wherein said base station comprises;

at least one antenna group, said antenna group including a plurality of antennas,

an analog phaser connected to said antenna group and configured to phase received signals so that a gain obtained from said antenna group is largest in desired beam-like directions,

a group of radio-frequency units, each said radio-frequency unit having an input and an output wherein said input of said radio-frequency units is configured to receive said phased signals,

a digitizer connected to said output of said radio-frequency units and configured to digitize said output of said radio-frequency units,

at least one channel unit, an input of said channel unit being configured to receive digitized signals output from said digitizer, said channel unit comprising at least one measurer and switcher, the measurer and the switcher being configured to (i) search said digitized signals for antenna beams corresponding to incoming directions of a strongest signal component and (ii) measure delays of signal components, and

a controller configured to control said phaser so that said largest gain of signals to be transmitted is set in said desired direction.

17. The base station as claimed in claim 16, wherein said analog phaser comprises a plurality of outputs, each of said outputs is a signal received by an antenna beam pointing in a certain direction.

18. The base station as claimed in claim 16, wherein said switcher

guides desired digitized signals that are visible at an input of said switcher and that have been converted into an intermediate frequency, to a desired demodulator controlled by said measurer, said measurer controlling each said desired demodulator by synchronizing with said digitized signal guided thereto.

19. A method for transmitting pilot channels in a cellular radio network, having in each cell, at least one base station configured to communicate with mobile stations located within a respective area, the communication including (i) transmitting at least one data signal in a downlink direction, and (ii) transmitting system information to respective said mobile stations on control channels, said method comprising:

said at least one base station transmitting at least one first pilot signal to all mobile stations within the cell, said pilot signal having a predetermined radiation pattern, the predetermined radiation pattern defining a coverage area for said cell; and

said at least one base station transmitting a second pilot signal specific for at least one said mobile station located within said coverage area, using an antenna radiation pattern based on at least one signal received by said base station as a result of transmitting by said at least one mobile station,

wherein said at least one data signal and said second pilot signal are transmitted using matching radiation patterns and said second pilot signal being incapable of carrying control information.

20. A cellular radio system comprising:

in each cell, at least one base station configured to communicate with mobile stations located within its coverage area, the communicating including (i) transmitting information about said system to said mobile stations using control channels, and (ii) transmitting at least one data signal to said mobile stations using transmission directions that change in time,

wherein said at least one base station is configured to transmit at least one first pilot signal to all mobile stations within the cell, said pilot signal having a predetermined radiation pattern, said predetermined radiation pattern defining the coverage area for said cell,

wherein said at least one base station is configured to transmit a second pilot signal in said transmission directions that change in time and said second pilot signal is incapable of carrying control information,

wherein said at least one data signal and said second pilot signal are transmitted using matching radiation patterns and

wherein said base station comprises;

at least one antenna group, said antenna group comprising a plurality of antennas,

a group of radio-frequency units each said radio-frequency unit having an input and an output, wherein said input of said radio-frequency units is configured to receive a phased signal,

a digitizer, connected to said output of said radio-frequency units and configured to digitize said output of said radio-frequency units, and

at least one channel unit, an input of said channel unit being configured to receive a digitized signal output from said digitizer, said channel unit comprising at least one measurer and switcher, the measurer and switcher being configured to (i) search said digitized signal for antenna beams corresponding to incoming directions of a strongest signal component and (ii) measure delays of said components.

21. A method for transmitting pilot channels in a cellular radio network, having in each cell, at least one base station configured to communicate with mobile stations located within a respective area, the communication including (i) transmitting at least one data signal in a downlink direction, and (ii) transmitting system information to respective said mobile stations on control channels, said method comprising:

said at least one base station transmitting at least one first pilot signal to all mobile stations within the cell, said pilot signal having a predetermined radiation pattern, the predetermined radiation pattern defining a coverage area for said cell; and

said at least one base station transmitting an un-modulated common control signal specific for at least one said mobile station located within said coverage area, using an antenna radiation pattern based on at least one signal received by said base station as a result of transmitting by said at least one mobile station,

wherein said at least one data signal and said un-modulated common control signal are transmitted using matching radiation patterns.