CDMA mobile communication scheme with effective use of sector configuration

• US 6,011,787 A
• Filed: 03/20/1997
• Issued: 01/04/2000
• Est. Priority Date: 03/21/1996
• Status: Expired due to Term

• Current Assignee: NTT Mobile Communications Network Inc. (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Mobile Communications Network Inc. (Nippon Telegraph and Telephone Corporation)
• Inventors: Nakamura, Takehiro, Onoe, Seizo, Nakano, Etsuhiro
• Primary Examiner(s): Patel, Ajit
• Assistant Examiner(s): NGUYEN, BRIAN D
• Application Number:
  US08/821,347
• Time in Patent Office: 1,020 Days
• Field of Search: 370/320, 370/328, 370/332, 370/335, 370/342, 370/441, 370/237, 370/230, 375/200, 455/422
• US Class Current: 370/335
• CPC Class Codes: H04B 7/0857 using maximum ratio combining techniques, e.g. signal-to- interference ratio [SIR], received signal strenght indication [RSS]
• CPC Class Codes: H04W 16/00 Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
• CPC Class Codes: H04W 16/02 Resource partitioning among network components, e.g. reuse partitioning
• CPC Class Codes: H04W 16/24 Cell structures
• CPC Class Codes: H04W 48/12 using downlink control channel

Abstract

A CDMA mobile communication scheme capable of increasing a number of sectors while not increasing a number of perch channel spread codes and not jamming the control channel traffic, so as to obtain the capacity increase effect by the use of the sector configuration effectively. At the base station, a perch channel spread by an identical perch channel spread code assigned to the base station is transmitted from each one of at least two sectors of the base station. Then, upward signals from each mobile station are received at more than one reception sectors, the upward signals received at more than one reception sectors are despread by using an identical uplink spread code, and a maximal ratio combining of despread upward signals is carried out, in a case of carrying out a simultaneous reception at more than one reception sectors. Also, downward signals are spread by using an identical downlink spread code, and spread downward signals are transmitted from more than one transmission sectors to each mobile station, in a case of carrying out a simultaneous transmission from more than one transmission sectors.

Claims

1. A method of mobile communication in a CDMA mobile communication system including base stations connected to a communication network and mobile stations for carrying out communications in a CDMA scheme with the base stations, each base station having a plurality of sectors dividing a cell of each base station, the method comprising the steps of:

transmitting a perch channel spread by a single perch channel spread code assigned to each base station, from each one of at least two sectors of each base station, such that each mobile station determines its connection target base station according to perch channels received from different base stations;

receiving upward signals at more than one reception sectors of each base station from those mobile stations which determined each base station as their connection target base station according to the perch channel transmitted by the transmitting step, despreading the upward signals received at said more than one reception sectors by using an identical uplink spread code, and carrying out a maximal ratio combining of despread upward signals at each base station, in a case of carrying out a simultaneous reception at said more than one reception sectors; and

spreading downward signals by using an identical downlink spread code at each base station, and transmitting spread downward signals from more than one transmission sectors of each base station to those mobile stations which determined each base station as their connection target base station according to the perch channel transmitted by the transmitting step, in a case of carrying out a simultaneous transmission from said more than one transmission sectors.

2. The method of claim 1, wherein at the transmitting step, the perch channel is transmitted from every one of said plurality of sectors.

3. The method of claim 1, further comprising the step of:

selecting at least one reception sector for receiving the upward signals from each mobile station and at least one transmission sector for transmitting the downward signals to each mobile station, at each base station.

4. The method of claim 1, wherein the receiving step always carries out the simultaneous reception at all of said plurality of sectors.

5. The method of claim 1, further comprising the steps of:

measuring receiving levels of the upward signals by using a level scanning receiver device provided in correspondence to each sector, by sequentially scanning uplink spread codes assigned to those mobile stations which are currently communicating with each base station; and

selecting at least one reception sector for receiving the upward signals from each mobile station, according to the receiving levels measured by the measuring step, at each base station.

6. The method of claim 1, further comprising the steps of:

measuring receiving levels of the upward signals by using a level scanning receiver device provided in correspondence to each mobile station, by sequentially switching a sector for carrying out a reception using an uplink spread code assigned to each mobile station; and

selecting at least one reception sector for receiving the upward signals from each mobile station, according to the receiving levels measured by the measuring step, at each base station.

7. The method of claim 1, further comprising the steps of:

measuring receiving levels of the upward signals by using a receiver device for receiving the upward signals from each mobile station which is provided in correspondence to one sector among said more than one reception sectors, by sequentially switching a sector for carrying out a reception using an uplink spread code assigned to each mobile station, when a difference between a receiving level at said one sector and a largest receiving level among said more than one reception sectors becomes greater than a prescribed value while the simultaneous reception at said more than one reception sectors is carried out; and

selecting said more than one reception sectors for receiving the upward signals from each mobile station, according to the receiving levels measured by the measuring step, at each base station.

8. The method of claim 1, further comprising the step of:

selecting those sectors among said plurality of sectors which are currently receiving the upward signals from each mobile station, as transmission sectors for transmitting the downward signals to each mobile station, at each base station; and

wherein the spreading step carries out the simultaneous transmission from the transmission sectors selected by the selecting step, by using an identical transmission power for each transmission sector.

9. The method of claim 1, further comprising the step of:

selecting one sector for which a receiving level is largest among those sectors which are currently receiving the upward signals from each mobile station, as a transmission sector for transmitting the downward signals to each mobile station, at each base station.

10. The method of claim 1, further comprising the step of:

selecting those sectors among said plurality of sectors which are currently receiving the upward signals from each mobile station, as transmission sectors for transmitting the downward signals to each mobile station, at each base station; and

wherein the spreading step carries out the simultaneous transmission from the transmission sectors selected by the selecting step, by using a transmission power ratio equal to a receiving level ratio for the transmission sectors.

11. The method of claim 1, wherein at the transmitting step, the perch channel transmitted from each sector contains a sector information for identifying each sector, and the method further comprises the steps of:

selecting one transmission sector for transmitting the downward signals to each mobile station, according to the sector information contained in the connection target perch channel transmitted from each sector, at each mobile station; and

notifying said one transmission sector selected by the selecting step from each mobile station to the base station by using the sector information contained in the perch channel transmitted from each sector, so that the spreading step carries out a transmission from said one transmission sector.

12. The method of claim 1, wherein the spreading step transmits the downward signals from different sectors through communication channels at different timings with respect to a transmission timing of the perch channel, and the method further comprises the steps of:

identifying each sector from which the downward signals are currently received at each mobile station according to a difference between a receiving timing of the perch channel and a receiving timing of each communication channel, measuring a receiving level of a communication channel for each identified sector, and notifying each identified sector and a measured receiving level for each identified sector from each mobile station to the connection target base station; and

selecting at least one transmission sector for transmitting the downward signals to each mobile station, according to the measured receiving level for each identified sector notified from each mobile station, at the connection target base station.

13. The method of claim 12, wherein the selecting step selects more than one transmission sectors, and the spreading step carries out the simultaneous transmission from said more than one transmission sectors selected by the selecting step, by using an identical transmission power for said more than one transmission sectors.

14. The method of claim 1, wherein the spreading step transmits the downward signals from different sectors through communication channels at different timings within a search range of a RAKE receiver of each mobile station, said different timings being set so that the communication channels of different sectors are separable by the RAKE receiver of each mobile station.

15. A base station apparatus for use in a CDMA mobile communication system including base stations connected to a communication network and mobile stations for carrying out communications in a CDMA scheme with the base stations, each base station having a plurality of sectors dividing a cell of each base station, the base station apparatus of each base station comprising:

a perch channel transmission device for transmitting a perch channel spread by a single perch channel spread code assigned to each base station, from each one of at least two sectors of each base station, such that each mobile station determines its connection target base station according to perch channels received from different base stations;

a communication channel reception device for receiving upward signals at more than one reception sectors of each base station from those mobile stations which determined each base station as their connection target base station according to the perch channel transmitted by the perch channel transmission device, despreading the upward signals received at said more than one reception sectors by using an identical uplink spread code, and carrying out a maximal ratio combining of despread upward signals at each base station, in a case of carrying out a simultaneous reception at said more than one reception sectors; and

a communication channel transmission device for spreading downward signals by using an identical downlink spread code at each base station, and transmitting spread downward signals from more than one transmission sectors of each base station to those mobile stations which determined each base station as their connection target base station according to the perch channel transmitted by the perch channel transmission device, in a case of carrying out a simultaneous transmission from said more than one transmission sectors.

16. The apparatus of claim 15, wherein the perch channel transmission device transmits the perch channel from every one of said plurality of sectors.

17. The apparatus of claim 15, further comprising:

a reception sector selection unit for selecting at least one reception sector for receiving the upward signals from each mobile station; and

a transmission sector selection unit for selecting at least one transmission sector for transmitting the downward signals to each mobile station.

18. The apparatus of claim 15, wherein the communication channel reception device always carries out the simultaneous reception at all of said plurality of sectors.

19. The apparatus of claim 15, further comprising:

a level scanning receiver device provided in correspondence to each sector, for measuring receiving levels of the upward signals by sequentially scanning uplink spread codes assigned to those mobile stations which are currently communicating with each base station; and

a reception sector selection unit for selecting at least one reception sector for receiving the upward signals from each mobile station according to the receiving levels measured by the level scanning receiver device.

20. The apparatus of claim 15, further comprising:

a level scanning receiver device provided in correspondence to each mobile station, for measuring receiving levels of the upward signals by sequentially switching a sector for carrying out a reception using an uplink spread code assigned to each mobile station; and

a reception sector selection unit for selecting at least one reception sector for receiving the upward signals from each mobile station according to the receiving levels measured by the level scanning receiver device.

21. The apparatus of claim 15, wherein the communication channel reception device includes:

a receiver device for receiving the upward signals from each mobile station which is provided in correspondence to each sector, the receiver device for one sector among said more than one reception sectors being used for measuring receiving levels of the upward signals by sequentially switching a sector for carrying out a reception using an uplink spread code assigned to each mobile station, when a difference between a receiving level at said one sector and a largest receiving level among said more than one reception sectors becomes greater than a prescribed value while the simultaneous reception at said more than one reception sectors is carried out; and

a reception sector selection unit for selecting said more than one reception sectors for receiving the upward signals from each mobile station according to the receiving levels measured by the receiver device for said one sector.

22. The apparatus of claim 15, further comprising:

a sector selection unit for selecting those sectors among said plurality of sectors which are currently receiving the upward signals from each mobile station, as transmission sectors for transmitting the downward signals to each mobile station; and

wherein the communication channel transmission device carries out the simultaneous transmission from the transmission sectors selected by the sector selection unit, by using an identical transmission power for each transmission sector.

23. The apparatus of claim 15, further comprising:

a sector selection unit for selecting one sector for which a receiving level is largest among those sectors which are currently receiving the upward signals from each mobile station, as a transmission sector for transmitting the downward signals to each mobile station.

24. The apparatus of claim 15, further comprising:

a sector selection unit for selecting those sectors among said plurality of sectors which are currently receiving the upward signals from each mobile station, as transmission sectors for transmitting the downward signals to each mobile station; and

wherein the communication channel transmission device carries out the simultaneous transmission from the transmission sectors selected by the sector selection unit, by using a transmission power ratio equal to a receiving level ratio for the transmission sectors.

25. The apparatus of claim 15, wherein the perch channel transmitted from each sector by the perch channel transmission device contains a sector information for identifying each sector, so that each mobile station selects one transmission sector for transmitting the downward signals to each mobile station according to the sector information contained in the perch channel transmitted from each sector, and notifies said one transmission sector to the connection target base station by using the sector information contained in the perch channel transmitted from each sector;

and

the communication channel transmission device carries out a transmission from said one transmission sector notified from each mobile station.

26. The apparatus of claim 15, wherein the communication channel transmission device transmits the downward signals from different sectors through communication channels at different timings with respect to a transmission timing of the perch channel by the perch channel transmission device, so that each mobile station identifies each sector from which the downward signals are currently received according to a difference between a receiving timing of the perch channel and a receiving timing of each communication channel, measures a receiving level of a communication channel for each identified sector, and notifies each identified sector and a measured receiving level for each identified sector to the connection target base station;

and

the apparatus further comprises;

a transmission sector selection unit for selecting at least one transmission sector for transmitting the downward signals to each mobile station according to the measured receiving level for each identified sector notified from each mobile station.

27. The apparatus of claim 26, wherein the transmission sector selection unit selects more than one transmission sectors, and the communication channel transmission device carries out the simultaneous transmission from said more than one transmission sectors selected by the transmission sector selection unit, by using an identical transmission power for said more than one transmission sectors.

28. The apparatus of claim 15, wherein the communication channel transmission device transmits the downward signals from different sectors through communication channels at different timings within a search range of a RAKE receiver of each mobile station, said different timings being set so that the communication channels of different sectors are separable by the RAKE receiver of each mobile station.

29. A mobile station apparatus for use in a CDMA mobile communication system including base stations connected to a communication network and mobile stations for carrying out communications in a CDMA scheme with the base stations, wherein each base station has a plurality of sectors dividing a cell of each base station and transmits a perch channel spread by a single perch channel spread code assigned to each base station, from each one of at least two sectors of each base station, and the perch channel transmitted from each sector contains a sector information for identifying each sector, the mobile station apparatus of each mobile station comprising:

a perch channel reception device for receiving the perch channel transmitted from each sector of each base station, determining a connection target base station according to perch channels received from different base stations, and selecting one transmission sector for transmitting downward signals from the connection target base station to said mobile station apparatus according to the perch channel transmitted from each sector of the connection target base station;

a communication channel reception device for receiving the downward signals transmitted from the connection target base station; and

a communication channel transmission device for transmitting upward signals to the connection target base station, the upward signals containing a portion for notifying said one transmission sector to the connection target base station by using the sector information contained in the perch channel transmitted from each sector of the connection target base station, so that the connection target base station carries out a transmission from said one transmission sector notified from said mobile station apparatus.

30. A mobile station apparatus for use in a CDMA mobile communication system including base stations connected to a communication network and mobile stations for carrying out communications in a CDMA scheme with the base stations, wherein each base station has a plurality of sectors dividing a cell of each base station, transmits a perch channel spread by a single perch channel spread code assigned to each base station, from each one of at least two sectors of each base station, and transmits downward signals from different sectors through communication channels at different timings with respect to a transmission timing of the perch channel, the mobile station apparatus of each mobile station comprising:

a perch channel reception device for receiving the perch channel transmitted from each sector of each base station and determining a connection target base station according to perch channels received from different base stations;

a communication channel reception device for receiving the downward signals transmitted from the connection target base station, identifying each sector from which the downward signals are currently received according to a difference between a receiving timing of the perch channel and a receiving timing of each communication channel, and measuring a receiving level of a communication channel for each identified sector; and

a communication channel transmission device for transmitting upward signals to the connection target base station, the upward signals containing a portion for notifying each identified sector and a measured receiving level for each identified sector to the connection target base station, so that the connection target base station selects at least one transmission sector for transmitting the downward signals from the connection target base station to said mobile station apparatus according to the measured receiving level for each identified sector notified from said mobile station apparatus.