Mobile communication system with shared time slots and frequency channels

• US 6,590,878 B1
• Filed: 01/15/1999
• Issued: 07/08/2003
• Est. Priority Date: 06/16/1997
• 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: Matsumoto, Shinji, Uchida, Yoshinori
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): Levitan, Dmitry
• Application Number:
  US09/214,940
• Time in Patent Office: 1,635 Days
• Field of Search: 370/347, 370/465, 370/330, 370/431, 370/218, 370/334, 370/319, 370/320, 370/321, 370/337, 370/335, 370/342, 370/343, 370/345, 370/441, 370/442, 370/478, 370/479, 370/480, 370/458
• US Class Current: 370/330
• CPC Class Codes: H04B 7/2618 using hybrid code-time division multiple access [CDMA-TDMA]
• CPC Class Codes: H04W 16/30 Special cell shapes, e.g. doughnuts or ring cells

Abstract

In a mobile communication system and a WLL communication system sharing a frequency or a time slot including time-divided CDMA method and TDMA method, radio waves are divided into groups according to a magnitude of a transmitting power and each group is assigned to a different time slot. Further, a frame synchronization is established among the base stations based on the transmitted radio waves, and cellular communication systems and PCS systems each having different time slot length are performed under a same frame synchronization.

Claims

1. A mobile communication system with shared time slots and shared frequency channels comprising:

a plurality of mobile stations such as automobile telephones and portable telephone units;

at least one base station; and

at least one mobile switching center connected to the base station, radio communication between said mobile stations and said base station being performed by using time-divided code division multiple access (CDMA) signals that share time slots and frequencies with time division multiple access (TDMA) signals or share only time slots with TDMA signals, wherein

said mobile switching center comprises;

time slot management means for controlling a transmission power of a TDMA signal sharing a time slot and a frequency channel with a time-divided CDMA signal to a minimum necessary level so as to improve the quality of the CDMA signal.

2. A mobile communication system as claimed in claim 1, further comprising at least one wireless local loop (WLL), wherein the mobile switching center comprises a memory, the mobile switching center identifies the WLL station belonging to the base station connected to the mobile switching center, stores radio information and relationship information of the WLL station as station identification information in the memory, and the mobile switching center uses the relationship information of the WLL station stored in the memory when initiating communication with the WLL station.

3. A mobile communication system as claimed in claim 2, wherein when completing the radio communication with the WLL station, the mobile switching center updates the relationship information of the WLL station stored in the memory by using relationship information obtained by radio communication.

4. A mobile communication system as claimed in claim 2, wherein when starting a radio communication with the WLL station, the mobile switching center transmits the relationship information of the WLL station to the base station, the base station receives the relationship information of the WLL station, a transmitter incorporated in the base station controls a transmission power of a radio wave which is sent to the WLL station according to a position of the WLL station by using the received relationship information of the WLL station, and transmits the radio wave of a controlled transmission power to the WLL station.

5. A mobile communication system as claimed in claim 2, wherein when starting a radio communication with the WLL station, the mobile switching center controls the transmission power of a radio wave transmitted from the base station connected to the WLL station according to a position of the WLL station by using the relationship information of the WLL station stored in the memory and a time slot to be used for communication with said WLL station is set to a time slot corresponding to the transmission power of the radio wave.

6. A mobile communication system as claimed in claim 2, wherein the mobile switching center classifies said at least one mobile station and said at least one WLL station according to a magnitude of a transmission power of the TDMA signal, assigns a different time slot to each classification, sets zones in one cell in a virtual manner for each classification, and locates the mobile station and the WLL station using the TDMA signals sharing time slots and frequency channels with time-divided CDMA signals in a zone of said base station, and the mobile switching center stores allocation information of the mobile station and the WLL station in the memory for controlling.

7. A mobile communication system as claimed in claim 1, further comprising at least one wireless local loop (WLL), wherein a transmitter in each of the mobile stations, the WLL stations, and the base stations controls, under the control of the mobile switching center, transmission power of at least one of said plurality of TDMA signals that shares a time slot and frequency channel with at least one of said time-divided CDMA signals.

8. A mobile communication system as claimed in claim 7, wherein the mobile switching center classifies said at least one mobile station and said at least one WLL station according to a magnitude of a transmission power of the TDMA signals that share time slots and frequency channels with time-divided CDMA signals, and assigns a different time slot to each classification.

9. A mobile communication system as claimed in claim 1, wherein even if any subscriber is not calling a WLL station, the WLL station is capable of receiving a plurality of control channels transmitted from the plurality of base stations, of measuring the time difference between frame synchronization information of the plurality of base stations, and of transmitting the measured information of the time difference to one of, both of, or the plurality of base stations.

10. A mobile communication system with shared time slots and shared frequency channels comprising:

a plurality of mobile stations such as automobile telephones and portable telephone units;

at least one wireless local loop (WLL) station;

at least one base station; and

at least one mobile switching center connected to the base station,

radio communication being performed between said mobile stations and said base station by using time-divided code division multiple access (CDMA) signals that share time slots and frequencies with time division multiple access (TDMA) signals or share only time slots with TDMA signals, wherein

said mobile switching center comprises;

control channel allocation means for determining whether to allow said base station, said mobile stations and said WLL station to use a TDMA signal as the control channel, to use one of a TDMA signal and a time-divided CDMA signal selected in accordance with a level of congestion, to use a TDMA signal and a time-divided CDMA signal alternatively depending on a current frame being transmitted, or to use a plurality of TDMA signals and a plurality of time-divided CDMA signals alternately depending on a current frame being transmitted.

11. A mobile communication system as claimed in claim 10, wherein the mobile station or the WLL station transmits and receives the control signal of the time-divided CDMA method and the control signal of the TDMA method and, at the same time, processes information relating to the control signal of the time-divided CDMA method and information relating to the control signal of the TDMA method, receives the TDMA control channel information and the time-divided CDMA control channel information while in a state of receiving broadcasting control channel information, and when communicating the control information, selects one of the TDMA control channel and the time-divided CDMA control channel and transmits the control information to the base station and the mobile switching center using the selected control channel.

12. A mobile communication system as claimed in claim 10, wherein either the base station or the mobile switching center, or both the base station and the mobile switching center, transmit and receive the control signal of the time-divided CDMA method and the control signal of the TDMA method and, at the same time, process information relating to the control signal of the time-divided CDMA method and information relating to the control signal of the TDMA method, or select either processing of the information relating to the control signal of the time-divided CDMA method or processing of the information relating to the control signal of the TDMA method.

13. A mobile communication system as claimed in claim 10, wherein either the base station or the mobile switching center, or both the base station and the mobile switching center, transmit and receive the control signal of the time-divided CDMA method and the control signal of the TDMA method and, at the same time, process information relating to the control signal of the time-divided CDMA method and information relating to the control signal of the TDMA method, and broadcast information relating to a traffic rate of the time-divided CDMA control channel and the TDMA control channel through a broadcasting control channel of the time-divided CDMA control channel and the TDMA control channel, and the mobile station or the WLL station selects one of the time-divided CDMA control channel and the TDMA control channel.

14. A mobile communication system as claimed in claim 10, wherein either the base station or the mobile switching center, or both the base station and the mobile switching center, transmit and receive the control signal of the time-divided CDMA method and the control signal of the TDMA method and, at the same time, process information relating to the control signal of the time-divided CDMA method and information relating to the control signal of the TDMA method, transmit and receive the time-divided CDMA control channel by using one time frame, and transmit and receive the TDMA control channel by using a following time frame so that the time-divided CDMA control channel and the TDMA control channel are transmitted and received alternately per frame.

15. A synchronized multi-operator mobile communication system with shared time slots and shared frequency channels comprising:

a plurality of mobile stations such as automobile telephones and portable telephone units;

at least one wireless local loop (WLL) station;

a plurality of base stations belonging to respective multiple operators; and

a plurality of mobile switching centers belonging to respective operators of different radio communication systems, and connected to respective ones of said plurality of base stations,

radio communication being performed between said mobile stations and said base stations by using time-divided code division multiple access (CDMA) signals that share time slots and frequencies with time division multiple access (TDMA) signals or share only time slots with TDMA signals, wherein

each of said mobile switching centers comprises;

information storing means for storing information related to control channels provided by said plurality of base stations; and

each of said plurality of base stations comprises;

control signal transmitting means for transmitting either a TDMA control signal or a time-divided CDMA control signal; and

time slot and frequency channel configuration sharing means for sharing the same time slot and frequency channel configuration for frame synchronization, by selectively using a control signal transmitted from a reference base station belonging to a different operator, in accordance with the information stored in said information storing means.

16. A mobile communication system as claimed in claim 15, wherein each of the plurality of base stations transmits the TDMA control signal or the time-divided CDMA control signal, one base station belonging to one operator interrupts the transmission of the control signal in a time slot while transmitting notice information to the mobile stations or to the WLL stations, and receives a control signal of another base station belonging to another operator during the interrupted time slot and synchronizes its own time frame with a time frame of the other base station belonging to the other operator.

17. A mobile communication system as claimed in claim 16, wherein when a base station belonging to an operator and acting as the standard breaks down and interrupts the transmission of the control channel, the plurality of base stations select and use a control channel of another base station belonging to another operator as an alternative standard.

18. A mobile communication system as claimed in claim 17, wherein when a base station belonging to an operator and acting as the standard breaks down and interrupts the transmission of the control channel, the plurality of base stations select and use a control channel of other base station belonging to other operator as an alternative standard, and the plurality of base stations and the mobile switching centers stores the order of the other base station to be the standard into a memory incorporated in each of the plurality of base stations and the mobile switching centers, and abandon the failed base station as the standard, and newly select another base station as the standard for frame synchronization according to the order stored in the memory.

19. A synchronized multi-operator mobile communication system with shared time slots and shared frequency channels comprising:

a plurality of mobile stations such as automobile telephones and portable telephone units;

a at least one wireless local loop (WLL) station;

a plurality of base stations belonging to respective multiple operators; and

a plurality of mobile switching centers belonging to respective operators of different radio communication systems, and connected to respective ones of said plurality of base stations,

radio communication being performed between said mobile stations and said base stations by using time-divided code division multiple access (CDMA) signals that share time slots and frequencies with time division multiple access (TDMA) signals or share only time slots with TDMA signals, wherein

each of said plurality of mobile stations comprises;

monitoring means for receiving control signals from base stations belonging to different operators, so as to collect time-difference information indicating a time difference between the received control signals, and for transmitting the time-difference information to a selected one of said plurality of base stations via selected ones of said plurality of mobile switching centers; and

each of said plurality of base stations comprises;

frame synchronization recovery means for recovering frame synchronization between said plurality of base stations in accordance with the time-difference information transmitted from each of said plurality of mobile stations.

20. A mobile communication system as claimed in claim 19, wherein when there is no WLL station or no mobile station in the peripheral areas in which the cells formed by the radio waves from the plurality of base stations are overlapped, a supervision station is placed at a position where the radio waves from the plurality of base stations can be received, and the supervision station measures the time difference among the frame synchronization information of the plurality of base stations, and transmits the measured information of the time difference to one of, or both of, or the plurality of base stations.

21. A mobile communication system with shared time slots and shared frequency channels comprising:

a plurality of mobile stations such as automobile telephones and portable telephone units;

at least one wireless local loop (WLL) station;

a plurality of base stations; and

at least one mobile switching center connected to said plurality of base stations,

radio communication being performed between said mobile stations and said base stations by using time-divided code division multiple access (CDMA) signals that share time slots and frequencies with time division multiple access (TDMA) signals or share only time slots with TDMA signals, wherein

said mobile switching center comprises;

time slot designation means for designating time slots used by said plurality of mobile stations, the WLL station and said plurality of base stations such that a given time slot is allocated to a plurality of zones that belong to different cells of said communication system and do not overlap each other.

22. A mobile communication system with shared time slots and shared frequency channels comprising:

a plurality of mobile stations such as automobile telephones and portable telephone units;

at least one wireless local loop (WLL) station;

a plurality of base stations; and

at least one mobile switching center connected to said plurality of base stations;

radio communication being performed between said mobile stations and said base stations by using time-divided code division multiple access (CDMA) signals that share time slots and frequencies with time division multiple access (TDMA) signals or share only time slots with TDMA signals, wherein

said mobile switching center comprises;

control means for controlling personal communication services (PCS) time slots and cellular time slots to be synchronized along a time line.

23. A mobile communication system as claimed in claim 22, wherein the time-divided time slot for cellular is a time-divided CDMA time slot for cellular, and the time-divided time slot for PCS is a time-divided CDMA time slot for PCS, and the mobile stations, the WLL stations, and the base stations control, under instruction of the mobile switching centers, the sharing of the time-divided CDMA time slot for cellular and the time-divided CDMA time slot for PCS in the same time-divided time slot so that a guard time of the time-divided CDMA time slot for cellular becomes longer than a guard time of the time-divided CDMA time slot for PCS.

24. A mobile communication system as claimed in claim 22, wherein the time-divided time slot for cellular is a TDMA time slot for cellular, and the time-divided time slot for PCS is a TDMA time slot for PCS, and the mobile stations, the WLL stations, and the base stations control, under instruction of the mobile switching stations, the sharing of the TDMA time slot for cellular and the TDMA time slot for PCS in the same time-divided time slot so that a guard time of the TDMA time slot for cellular is longer than a guard time of the TDMA time slot for PCS.

25. A mobile communication system as claimed in claim 22, wherein the time-divided time slot for cellular is a time-divided CDMA time slot for cellular and a TDMA time slot for cellular, and the time-divided time slot for PCS is a time-divided CDMA time slot for PCS and a TDMA time slot for PCS, and the mobile stations, the WLL stations, and the base stations control, under instruction of the mobile switching stations, the sharing of the time-divided CDMA time slot for cellular and the TDMA time slot for cellular and the time-divided CDMA time slot for PCS and the TDMA time slot for PCS in the same time-divided time slot so that a guard time of the TDMA time slot for cellular becomes longer than a guard time of the TDMA time slot for PCS.

26. A mobile communication system with shared time slots and shared frequency channels comprising:

a plurality of mobile stations such as automobile telephones and portable telephone units;

at least one wireless local loop (WLL) station;

a plurality of base stations; and

at least one mobile switching center connected to said plurality of base stations;

radio communication being performed between said mobile stations and said base stations by using time-divided code division multiple access (CDMA) signals that share time slots and frequencies with time division multiple access (TDMA) signals or share only time slots with TDMA signals, wherein

each of said plurality of base stations comprises;

measuring means for measuring a first time difference between a transmission of a radio wave from that base station to one of said plurality of mobile stations, and a reception thereof;

each of said plurality of mobile stations comprises;

transmitting means for transmitting to a first base station a second time difference that elapses between an arrival of a first radio wave from the first base station and an arrival of a second radio wave from a second base station; and

said mobile switching center comprises;

time slot management means for receiving the first time difference and the second time difference, so as to determine a third time difference that should be provided by an associated one of said plurality of mobile stations between a transmission of a radio wave and a head of a frame.

27. A mobile communication system as claimed in claim 26, wherein the information of the time difference is stored in a memory in each of the plurality of mobile switching centers.

28. A synchronized multi-operator mobile communication system with shared time slots and shared frequency signals comprising:

a plurality of mobile stations such as automobile telephones and portable telephone units;

at least one wireless local loop (WLL) station;

a plurality of base stations belonging to respective multiple operators; and

a plurality of mobile switching centers belonging to respective operators of different radio communication systems, and connected to respective ones of said plurality of base stations,

radio communication being performed by using time-divided code division multiple access (CDMA) signals that share time slots and frequencies with time division multiple access (TDMA) signals or share only time slots with TDMA signals, wherein

the WLL station comprises;

monitoring means for receiving control signals from base stations belonging to different operators, so as to collect time-difference information indicating a time difference between the received control signals, and for transmitting the time-difference information to a selected one of said plurality of base stations via selected ones of said plurality of mobile switching centers; and

each of said plurality of base stations comprises;

frame synchronization recovery means for recovering frame synchronization between said plurality of base stations in accordance with the time-difference information transmitted from the WLL station.

29. A mobile communication system as claimed in claim 28, wherein when there is no WLL station or no mobile station in the peripheral areas in which the cells formed by the radio waves from the plurality of base stations are overlapped, a supervision station is placed at a position where the radio waves from the plurality of base stations can be received, and the supervision station measures the time difference among the frame synchronization information of the plurality of base stations, and transmits the measured information of the time difference to at least one of said plurality of base stations.