Digital mobile communication system capable of establishing mutual synchronization among a plurality of radio base stations

• US 5,912,886 A
• Filed: 02/07/1997
• Issued: 06/15/1999
• Est. Priority Date: 02/09/1996
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Sugawara, Koji, Takahashi, Hideaki
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): BEAULIEU, YONEL
• Application Number:
  US08/796,951
• Time in Patent Office: 858 Days
• Field of Search: 370/350, 370/324, 370/503, 370/516, 370/517, 370/519, 375/355, 375/356
• US Class Current: 370/350
• CPC Class Codes: H04B 7/2693 Centralised synchronisation, i.e. using external universal time reference, e.g. by using a global positioning system [GPS] or by distributing time reference over the wireline network
• CPC Class Codes: H04J 3/0602 Systems characterised by the synchronising information used
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging

Abstract

A mobile communication system is capable of establishing mutual synchronization of radio communication channels among a plurality of radio base stations. A synchronization timing control center is included in a wired telephone network as a terminal equipment of the wired telephone network. Each radio base station in the mobile communication network makes a connection to the synchronization timing control center by way of a mobile switching center, for establishing frame synchronization. Each radio base station measures a value of transmission delay between the radio base station and the synchronization timing control center, and then receives a frame signal as a reference signal from the synchronization timing control center. The formal frame signal to be used by each radio base station is reproduced by compensating the received frame signal by the transmission delay value which varies for each radio base station. Once the frame signal has been established, the signal is held by the clock timing of the network synchronization circuit in each radio base station.

Claims

1. A digital mobile communication system for performing a communication between a radio base station and a mobile station by a time division multiple access (TDMA) system, said digital mobile communication system comprising:

a synchronization timing control center installed in a wired telephone network connected to a digital mobile communication network through a mobile switching center having an identification number as a terminal equipment within the wired telephone network, for sending out a frame pulse which constitutes a reference used to synchronize radio communication channels of the radio base station within said digital mobile communication network; and

said radio base station includes;

a call connection control unit for controlling an establishment of call connection with said synchronization timing control center by using said identification number allocated to said mobile switching center within said wired telephone network;

a transmission delay amount measuring unit for measuring a transmission delay of a connection path established to said synchronization timing control center; and

a synchronization signal producing unit for receiving a reference frame pulse sent out from said synchronization timing control center and for correcting said reference frame pulse based on the transmission delay amount measured by said transmission delay amount measuring unit to thereby produce a radio communication channel synchronization signal.

2. A digital mobile communication system as claimed in claim 1 wherein said radio base station being connected to said mobile switching center further comprises:

a network synchronization circuit for extracting a network synchronized pulse supplied from said mobile switching center; and

a synchronization holding circuit for using the extracted network-synchronized pulse as an operation clock of the radio base station, and holding the radio communication synchronization signal produced by said synchronization signal producing unit in response to said operation clock.

3. A digital mobile communication system as claimed in claim 1, wherein said synchronization timing control center is located separate from said mobile switching center, and

wherein communications between said synchronization timing control center and said mobile switching center is provided only by way of said wired telephone network.

5. A digital mobile communication system as claimed in claim 3, wherein:

said synchronization timing control center further comprising;

a second bit pattern signal transmission unit for transmitting a second bit pattern signal; and

a switching unit for switching said connection path being established by said radio base station to said second bit pattern signal transmission unit from said signal turning back unit after a predetermined time has passed since said connection path establishment.

4. A digital mobile communication system for performing a communication between a radio base station and a mobile station by a time division multiple access (TDMA) system, said digital mobile communication system comprising:

a synchronization timing control center installed in a wired communication network connected to a digital mobile communication network through a mobile switching center, for sending out a frame pulse which constitutes a reference used to synchronize radio communication channels of the radio base station within said digital mobile communication network; and

said radio base station includes;

a call connection control unit for controlling an establishment of call connection with said synchronization timing control center;

a transmission delay amount measuring unit for measuring a transmission delay of a connection path established to said synchronization timing control center;

a synchronization signal producing unit for receiving a reference frame pulse sent out from said synchronization timing control center and for correcting said reference frame pulse based on the transmission delay amount measured by said transmission delay amount measuring unit to thereby produce a radio communication channel synchronization signal;

a network synchronization circuit for extracting a network synchronized pulse supplied from said mobile switching center; and

a synchronization holding circuit for using the extracted network-synchronized pulse as an operation clock of the radio base station, and holding the radio communication synchronization signal produced by said synchronization signal producing unit in response to said operation clock,

wherein;

said synchronization timing control center includes a signal turning back unit; and

said transmission delay amount measuring unit includes;

a first bit pattern signal transmission unit for transmitting a first bit pattern signal to said synchronization timing control center when said connection path to said synchronization timing control center is being established;

a first bit pattern signal detecting unit for detecting said first bit pattern signal returned by said signal turning back unit in said synchronization timing control center;

a delay time measuring unit for measuring time defined from a time when said first bit pattern signal transmission unit transmits said first bit pattern signal up to a time when said first bit pattern signal detecting unit detects said first bit pattern signal returned by said signal turning back unit; and

a delay amount correcting unit for judging a half of the delay time measured by said delay time measuring unit as a transmission delay amount.

6. A digital mobile communication system as claimed in claim 4, wherein said second bit pattern signal corresponds to a frame pulse as a synchronization reference of the radio communication channel, and said synchronization signal producing unit further comprises:

a second bit pattern signal detecting unit for detecting said second bit pattern signal for producing a radio communication channel synchronization signal based upon the transmission delay amount judged by said delay amount correcting unit.

7. A method for performing a communication between a radio base station and a mobile station by a time division multiple access (TDMA) system, said method comprising:

sending out, via a synchronization timing control center installed in a wired telephone network, the synchronization timing control center being communicatively connected to a digital mobile communication network through a mobile switching center having an identification number within the wired telephone network, a frame pulse which constitutes a reference used to synchronize radio communication channels of said radio base station within said TDRA system;

controlling, by said radio base station, an establishment of call connection with said synchronization timing control center by using said identification number allocated to said mobile switching center within said wired telephone network;

measuring, by said radio base station, a transmission delay of a connection path established to said synchronization timing control center;

receiving, by said radio base station, a reference frame pulse sent out from said synchronization timing control center; and

correcting, by said radio base station, said reference frame pulse based on the measured transmission delay amount to thereby produce a radio communication channel synchronization signal.