Mobile communication system

• US 6,219,347 B1
• Filed: 02/12/1999
• Issued: 04/17/2001
• Est. Priority Date: 08/08/1997
• Status: Expired due to Term

• Current Assignee: TCL Communication Technology Holdings Ltd. (TCL Technology Group Corp.)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Uchida, Yoshinori, Suzuki, Kuniyuki
• Primary Examiner(s): TON, DANG T
• Application Number:
  US09/242,250
• Time in Patent Office: 795 Days
• Field of Search: 370/342, 370/320, 370/324, 370/347, 370/441, 370/442, 370/465, 370/332, 370/311, 370/319, 370/321, 370/329, 370/331, 370/333, 370/334, 370/335-338, 370/341, 370/349, 370/348, 455/38.3, 455/522, 455/422, 455/560, 455/436, 375/130, 375/140
• US Class Current: 370/347
• CPC Class Codes: H04W 36/249 according to timing information
• CPC Class Codes: H04W 36/324 by mobility data, e.g. speed data
• CPC Class Codes: H04W 56/0025 synchronizing potentially movable access points

Abstract

A mobile communication system wherein a mobile station measures the distances between the mobile station and a plurality of adjacent radio base stations each from a time difference, eliminated by a fixed time difference, between the top time position of a time-divided CDMA burst signal received from a radio base station and the top time position of a time-divided CDMA burst signal transmitted to the radio base station in response to an instruction from the radio base station so that the top of the time-divided CDMA burst signal may come to the top time position of a time slot, and utilizes a result of the measurement for a hand-over discrimination, and frame synchronization between the radio base stations is established with a high degree of accuracy so that a plurality of radio base stations may operate in a same frame synchronization condition.

Claims

1. A mobile communication system having a plurality of mobile stations and at least one radio base station in which bidirectional communication using a time-divided CDMA system is performed between said mobile stations and said at least one radio base station,

wherein each of said mobile stations measures a time difference having a fixed period of time subtracted therefrom, between a time that a time-divided CDMA burst signal is received from said radio base station and a time that a time-divided CDMA burst signal is transmitted by that respective mobile station in response to an instruction of said radio base station so that the transmitted time-divided CDMA burst signal may arrive at said radio base station at a start time position of a time slot of said time-divided CDMA system, and transmits information of the measured time difference to said radio base station.

2. A mobile communication system having a plurality of mobile stations and at least one radio base station in which bidirectional communication is performed between said mobile stations and sad at least one radio base station using a TDMA/time-divided CDMA sharing system wherein a time slot of the time-divided CDMA system is inserted in time slots of a frame construction of a TDMA system,

wherein each of said mobile stations measures a time difference having a fixed period of time subtracted therefrom, between a time that a time-divided CDMA burst signal is received from said radio base station and a time that a time-divided CDMA burst signal is transmitted by that respective mobile station in response to an instruction of said radio base station so that the transmitted time-divided CDMA burst signal may arrive at said radio base station at a start time position of a time slot of said TDMA/time-divided CDMA sharing system, and transmits information of the measured time difference to said radio base station.

3. A mobile communication system according to claim 2,

wherein the time difference having a fixed period of time subtracted therefrom, between the start time position of the time-divided CDMA burst signal received from said radio base station by each of said mobile stations and the start time position of the time-divided CDMA burst signal transmitted from the mobile station to said radio base station is measured in a chip rate unit which is used in time-divided CDMA communication.

4. A mobile communication system according to claim 2,

wherein each of said mobile stations is radio-connected to one radio base station,

wherein during a communication, a time difference having a fixed period of time subtracted therefrom, is measured between a start time position of a time-divided CDMA burst signal received from any radio base station other than the one radio base station and the start time position of the time-divided CDMA burst signal received from the one radio base station to which the mobile station is radio connected, and

wherein information of the measured time difference is transmitted to the one radio base station to which the mobile station is radio connected.

5. A mobile communication system according to claim 2,

wherein each of said mobile stations includes:

a correlation reception/despread-spectrum coding calculation section for extracting an original signal, which is not in a spread-spectrum coded condition, from a spread-spectrum coded signal sent thereto from said radio base station;

a channel reception/TDMA demodulation section for demodulating a time-divided CDMA signal despread-spectrum coded by said correlation reception/despread-spectrum coding calculation section and extracting a necessary signal from a format of a signal obtained by the demodulation;

a digital-to-analog conversion section for decoding an information signal from the signal extracted by said channel reception/TDMA demodulation section into an analog signal and forwarding the analog signal to a man-machine interface section;

an analog-to-digital conversion section for coding an information signal from said man-machine interface section into a digital code signal;

a channel transmission/TDMA multiplexing section for multiplexing the signal coded by said analog-to-digital conversion section;

a spread-spectrum coding calculation section for spectrum-spreading the information multiplexed by said channel transmission/TDMA multiplexing section on a frequency axis using a spread-spectrum code allocated to the self station;

a burst control/intra-frame time setting and time measurement section for controlling and adjusting an emission time of a burst signal which emits the information spread-spectrum coded by said spread-spectrum coding calculation section in response to an instruction of said radio base station and measuring the time difference, eliminated by the fixed time difference, between the top time position of the time-divided CDMA burst signal received from said radio base station and the top time position of the time-divided CDMA burst signal transmitted to said radio base station in a chip rate unit which is used in time-divided CDMA communication; and

a spread-spectrum code generator-chip rate generator for generating a chip rate to be used for the time-divided CDMA communication and the spread-spectrum code allocated to the self station and for supplying the chip rate and the spread-spectrum code to said burst control/intra-frame time setting and time measurement section or said correlation reception/despread-spectrum coding calculation section and spread-spectrum coding calculation section.

6. A mobile communication system according to claim 2,

wherein said radio base station includes:

a plurality of signal processing sections each including a correlation reception/despread-spectrum coding calculation section for extracting an original signal from a spread-spectrum coded signal, a channel reception/TDMA demodulation section for demodulating a despread-spectrum coded time-divided CDMA signal and extracting a necessary signal, a conversion section for decoding the extracted signal into an information signal and outputting the information signal to a network interface section, another conversion section for coding an information signal inputted from said network interface section, a channel transmission/TDMA multiplexing section for multiplexing the coded signal, a spread-spectrum coding calculation section for spectrum-spreading the multiplexed information on a frequency axis, a burst control/intra-frame time setting and time measurement section for controlling and adjusting an emission time of a burst signal which emits the spread-spectrum coded information and for performing time setting and time measurement in a frame, and a spread-spectrum code generator-chip rate generator for generating a chip rate to be used for the time measurement and the spread-spectrum code allocated to the self station; and

a signal distribution and addition section for adding signals outputted from said signal processing sections and outputting a result of the addition to a transmission section and for distributing a signal received by a reception section to said signal processing sections.

7. A mobile communication system according to claim 6,

wherein in at least one of said signal processing sections of said radio base station,

said conversion section for decoding the information signal is constructed as a digital-to-analog conversion section for decoding the signal extracted by said channel reception/TDMA demodulation section into an analog information signal and outputting the analog information signal to an analog network interface section, and

said conversion section for coding an information signal is constructed as an analog-to-digital conversion section for coding an information signal inputted from said analog network interface section into a digital code signal.

8. A mobile communication system according to claim 5,

wherein said channel reception/TDMA demodulation section of each of said mobile stations includes a demultiplexing section for separating an information signal and control information included in a time slot selected from among a plurality of time slots and destined for the self station, an information signal memory for temporarily storing the information signal and a control information memory for temporarily storing the control information,

wherein said channel transmission/TDMA multiplexing section includes an information signal memory for temporarily storing an information signal to be transmitted, a control information memory for temporarily storing control information to be transmitted, and a multiplexing section for composing the information signal and the control information and multiplexing the composed signal in a time slot allocated to the self station, and

wherein the mobile station includes a control information processor for decoding the control information from said radio base station, instructing the mobile station of various functions based on the decoded control information and transmitting a response to the control information to said radio base station.

9. A mobile communication system having a plurality of mobile stations and at least one radio base station in which bidirectional communication is performed between said mobile stations and said at least one radio base station using a TDMA/time-divided CDMA sharing system wherein a time slot of the time-divided CDMA system is inserted in time slots of a frame construction of a TDMA system,

wherein each of said radio base stations includes:

a first process of receiving, when first participating in said system, a TDMA control channel transmitted from said radio base station, transmitting control information to said radio base station using a designated TDMA control channel based on the received information, and performing communication of necessary control information with said radio base station via the bidirectional TDMA control channels,

a second process of communicating, when a TDMA speech channel is designated, using the TDMA speech channel, and

a third process of communicating by using the time-divided CDMA speech channel when a time-divided CDMA speech channel is designated.

10. A mobile communication system according to claim 9, wherein in said first process of each of said mobile stations, after said radio base station receiving a TDMA control information signal burst from a respective mobile station discriminates that the received burst is at an appropriate burst position and transmits the discrimination information to the respective mobile station via the control channel, the mobile station measures a time difference between a start time position of a TDMA control signal burst transmitted from said radio base station and a start time position of a TDMA control signal burst transmitted from the respective mobile station to said radio base station in an information symbol rate unit and transmits the time difference information to said radio base station.

11. A mobile communication system according to claim 9, wherein in said second process of each of said mobile stations, after said radio base station receiving a TDMA speech information signal burst from a respective mobile station discriminates that the received burst is at an appropriate burst position and transmits the discrimination information to the respective mobile station via a control channel in a speech channel, the mobile station measures a time difference having a fixed period of time subtracted therefrom between a start time position of a TDMA speech signal burst transmitted from said radio base station and a start time position of a TDMA speech signal burst transmitted from the respective mobile station to said radio base station in a time-divided CDMA chip rate unit and transmits the time difference information to said radio base station.

12. A mobile communication system according to claim 9, wherein in said third process of each of said mobile stations, after said radio base station receiving a time-divided CDMA speech information signal burst from a respective mobile station discriminates that the received burst is at an appropriate burst position and transmits, if it is discriminated that the received burst is at an appropriate burst position, the discrimination information to the respective mobile station via a control channel in a speech channel, the mobile station measures a time difference having a fixed period of time subtracted therefrom, between a start time position of a time-divided CDMA speech signal burst transmitted from said radio base station and a start time position of a time-divided CDMA speech signal burst transmitted from the respective mobile station to said radio base station in a time-divided CDMA chip rate unit and transmits the time difference information to said radio base station.

13. A mobile communication system having a plurality of mobile stations and at least one radio base station in which bidirectional communication is performed between said plurality of mobile stations and sad at least one radio base station using a TDMA/time-divided CDMA sharing system that a time slot of the time-divided CDMA system is inserted in time slots of a frame construction of a TDMA system,

wherein each of said mobile stations measures a time difference having a fixed period of time subtracted therefrom, between a start time position of a TDMA burst or a time-divided CDMA burst received from said radio base station and a start time position of a TDMA burst or a time-divided CDMA burst transmitted by that mobile station to said radio base station in a chip rate unit and transmits the time difference information to said radio base station, and

wherein a mobile switching center which accommodates a plurality of radio base stations has a function of calculating distances between said radio base stations and said mobile stations based on the time difference information collected from said radio base stations and storing distance information obtained from said time difference information.

14. A mobile communication system according to claim 13, wherein said mobile switching center measures distances between each of said mobile stations and a plurality of radio base stations around each mobile station, supervises the measured distances, and if the distance to a respective mobile station is shorter from any other one of the radio base stations than from the radio base station to which the mobile station is connected, forwards to the respective mobile station a hand-over starting instruction so as to newly set a radio channel to the one radio base station.

15. A mobile communication system according to claim 14, wherein when said mobile switching center tries to forward a hand-over starting instruction to the radio base station nearest to the respective mobile station, if that radio base station is a radio base station of a different operator than the radio base station to which said respective mobile station is presently radio-connected, said mobile switching center transmits a hand-over starting instruction to the radio base station nearest to the respective mobile station via a public system and a mobile switching center of the different operator.

16. A mobile communication system having a plurality of mobile stations and a plurality of radio base stations in which bidirectional communication using a time-divided CDMA system is performed between said plurality of mobile stations and said plurality of radio base stations,

wherein when a time-divided CDMA control signal burst transmitted from a radio base station is received by a tributary base station, said tributary base station measures a time difference having a fixed period of time subtracted therefrom, between a start time position of a time-divided CDMA burst signal received from said radio base station and a start time position of a time-divided CDMA burst signal transmitted from said tributary base station in response to an instruction from said transmitting radio base station so that a beginning of the time-divided CDMA burst signal may arrive at said tributary radio base position at a start time position of a time slot, and transmits the measurement information therefrom to said transmitting radio base station.

17. A mobile communication system having a plurality of mobile stations and a plurality of radio base stations in which bidirectional communication is performed between said plurality of mobile stations and said plurality of radio base stations using a TDMA/time-divided CDMA sharing system that a time slot of the time-divided CDMA system is inserted in time slots of a frame construction of a TDMA system,

wherein when a TDMA control signal burst or a time-divided CDMA control signal burst transmitted from a radio base station is received by a tributary base station, said tributary base station measures a time difference having a fixed period of time subtracted therefrom, between a start time position of a TDMA burst signal or a time-divided CDMA burst signal received from said radio base station and a start time position of a time-divided CDMA burst signal transmitted from said tributary base station in response to an instruction from said radio base station so that a start of the time-divided CDMA burst signal may arrive at said radio base position at a start position of a time slot, and transmits the measurement information therefrom to said transmitting radio base station.

18. A mobile communication system according to claim 17, wherein a time difference having a fixed period of time subtracted therefrom, between start time positions of burst signals transmitted and received to and from said transmitting radio base station by said tributary base station is measured in a chip rate unit which is used in time-divided CDMA communication.

19. A mobile communication system according to claim 17, wherein said transmitting radio base station receives a time-divided CDMA control information signal burst transmitted from said tributary base station, discriminates whether or not the received burst is at an appropriate burst position, and transmits the discrimination information to said tributary base station via a control channel when it is discriminated that the received burst is at an appropriate burst position, and

wherein said tributary base station transmits, after receiving the discrimination information, information of a time difference having a fixed period of time subtracted therefrom, between a start time position of a time-divided CDMA control signal burst transmitted from said radio base station and a start time position of a time-divided CDMA control signal burst transmitted from said tributary base station to said transmitting radio base.

20. A mobile communication system according to claim 18,

wherein said radio base station receives a time-divided CDMA control information signal burst transmitted from said tributary base station, discriminates whether or not the received burst is at an appropriate burst position, and transmits the displacement information measured in a chip rate unit of said time-divided CDMA system to said tributary base station via a control channel when it is discriminated that the received burst is displaced from the appropriate burst position, and

wherein said tributary base station corrects a top time position of a time-divided CDMA control signal burst to be transmitted from said tributary base station to said radio base station, based on the information of the displacement received from said radio base station, by a time corresponding to the displacement with reference to a top time position of a time-divided CDMA control signal burst transmitted from said tributary base station to said radio base station and transmits the corrected time-divided CDMA control signal burst to said radio base station.

21. A mobile communication system according to claim 20, wherein when said tributary base station receives a time-divided CDMA control information signal burst transmitted from said radio base station and detects a start time position of the received burst signal, said tributary base station stops transmission of a burst signal of a time slot which should originally be transmitted from said tributary base station, and receives the time-divided CDMA control signal burst transmitted from said radio base station.

25. A mobile communication system according to claim 17, wherein said transmitting radio base station has a function of transmitting, when synchronization information is to be propagated from said radio base station to a plurality of tributary base stations, one or both of a TDMA control signal burst and a time-divided CDMA control signal burst by one or both of a TDMA control channel and a time-divided CDMA control channel, and

wherein each of said tributary base stations has a function of transmitting a TDMA control signal burst or a time-divided CDMA control signal burst by a TDMA control channel or a time-divided CDMA control channel when synchronization information is to be propagated from a respective tributary base station to said radio base station.

22. A mobile communication system having a plurality of mobile stations and a plurality of radio base stations in which bidirectional communication is performed between said plurality of mobile stations and said plurality of radio base stations using a TDMA/time-divided CDMA sharing system that a time slot of the time-divided CDMA system is inserted in time slots of a frame construction of a TDMA system, and

wherein a TDD mobile communication system in which a radio base station receives a time-divided CDMA control information signal burst transmitted from a tributary base station discriminates that the received burst is at an appropriate burst position, and transmits the discrimination information therefrom to said tributary base station via a control channel and said tributary base station transmits, after the discrimination information is received from said radio base station, information of a time difference between a start time position of a time-divided CDMA control signal burst transmitted from said radio base station and a start time position of a time-divided CDMA control signal burst transmitted from said tributary base station to said radio base station to said radio base station is constructed, and

wherein said radio base station performs transmission of one or both of a TDMA control signal burst and a time-divided CDMA control signal burst once for two frames in a beginning slot of the frame.

23. A mobile communication system according to claim 22, wherein when said basic base station tries to transmit one or both of a TDMA control signal burst and a time-divided CDMA control signal burst once for two frames in a beginning slot, in a time slot in which a TDMA control signal burst and a time-divided CDMA control signal burst are not transmitted in a beginning slot thereof, said radio base station receives one or both of a TDMA control signal burst and a time-divided CDMA control signal burst transmitted from said tributary base station.

24. A mobile communication system according to claim 23,

wherein in a time slot that said basic base station receives one or both of a TDMA control signal burst and a time-divided CDMA control signal burst transmitted from said tributary base station, even if the time slot is one or both of a TDMA speech signal burst and a time-divided CDMA speech signal burst which should originally be transmitted as a down-link by said radio base station, the transmission is stopped and one or both of the TDMA control signal burst and the time-divided CDMA control signal burst from said tributary base station are received.

30. A mobile communication system according to claim 22, wherein said transmitting radio base station has a function of transmitting, when synchronization information is to be propagated from said radio base station to a plurality of tributary base stations, one or both of a TDMA control signal burst and a time-divided CDMA control signal burst by one or both of a TDMA control channel and a time-divided CDMA control channel, and

wherein each of said tributary base stations has a function of transmitting a TDMA control signal burst or a time-divided CDMA control signal burst by a TDMA control channel or a time-divided CDMA control channel when synchronization information is to be propagated from a respective tributary base station to said radio base station.

26. A mobile communication system having a plurality of mobile stations and a plurality of radio base stations in which bidirectional communication is performed between said plurality of mobile stations and said plurality of radio base stations using a TDMA/time-divided CDMA sharing system that a time slot of the time-divided CDMA system is inserted in time slots of a frame construction of a TDMA system,

wherein when a time difference having a fixed period of time subtracted therefrom, between a start time position of a received burst position at a tributary base station of said plurality of base stations and a start time position of a TDMA burst signal or a time-divided CDMA burst signal transmitted from said tributary base station to said radio base station is measured in a chip rate unit of the time-divided CDMA by said tributary base station when a TDMA control signal burst or a time-divided CDMA control signal burst transmitted from a radio base station is received by said tributary base station, and the measurement information is transmitted from said tributary base station to said transmitting radio base station to set frame synchronization between said radio base stations,

frame synchronization between said radio base stations is first established using a TDMA control channel, and then

establishment of frame synchronization between said radio base stations in a chip rate unit of the time-divided CDMA is performed using a time-divided CDMA control channel, and then information of a displacement time from a start time position of a time-divided CDMA control signal burst received from said transmitting radio base station by said tributary base station when frame synchronization between said radio base stations is established in a chip rate unit of the time-divided CDMA to a top time position of a time-divided CDMA control signal burst transmitted from said tributary base station to said transmitting radio base station is stored into a memory of at least one of said tributary base station, or a mobile switching center which accommodates said tributary base station.

27. A mobile communication system according to claim 26, wherein after frame synchronization between said radio base stations is established in a chip rate unit of the time-divided CDMA,

said tributary base station stops transmission of a time-divided CDMA control signal burst therefrom to said radio base station and adjusts top time positions of time-divided CDMA control signal bursts to be transmitted to a plurality of mobile stations in accordance with the information of the time of displacement stored in said memory from a start time position of the time-divided CDMA control signal burst received from said transmitting radio base station, and

said transmitting radio base station uses a time slot, in which said radio base station has received the time-divided CDMA control signal from said tributary base station, as a speech channel to down-links to said plurality of mobile stations, and transmits a time-divided CDMA speech signal burst.

28. A mobile communication system according to claim 27,

wherein after frame synchronization between said radio base stations is established in a chip rate unit of the time-divided CDMA,

when, while said radio base station uses a time slot, with which said radio base station has received a time-divided CDMA control signal from said tributary base station, as a speech channel for a down-link to a plurality of mobile stations, a call request to the mobile station which has used the down-link disappears, transmission of a time-divided CDMA speech signal burst to the mobile station is stopped in the time slot, and reception of a time-divided CDMA control signal burst from said tributary base station is resumed to effect frame synchronization establishment between said radio base stations.

29. A mobile communication system according to claim 26,

wherein when one of said radio base stations tries to establish frame synchronization with another one of said radio base stations,

frame synchronization between the radio base stations is established first using a TDMA control channel, and then

it is discriminated whether or not use of a time-divided CDMA control channel is allowed, and if use of a time-divided CDMA control channel is not allowed, then frame synchronization between the radio base stations using the TDMA control channel is repeated, and,

after use of the time-divided CDMA control channel becomes allowed, establishment of frame synchronization between the radio base stations is performed in a chip rate unit of the time-divided CDMA using the time-divided CDMA control channel.