Space diversity system in TDMA communication system

• US 4,218,654 A
• Filed: 02/21/1979
• Issued: 08/19/1980
• Est. Priority Date: 04/28/1978
• Status: Expired due to Term

• Current Assignee: Kokusai Densin Denwa Kabushiki Kaisha
• Original Assignee: Kokusai Densin Denwa Kabushiki Kaisha
• Inventors: Ogawa, Akira, Watanabe, Tatsuo, Saito, Hideki
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US06/013,287
• Time in Patent Office: 545 Days
• Field of Search: 178/69.1, 179/15 AD, 179/15 BS, 325/3, 325/4, 325/42, 325/56, 325/65, 343/100 ST
• US Class Current: 370/324
• CPC Class Codes: H04B 7/0845 per branch equalization, e.g. by an FIR-filter or RAKE receiver per antenna branch rake receivers as such H04B1/7115
• CPC Class Codes: H04B 7/0894 using different delays between antennas
• CPC Class Codes: H04B 7/18534 for enhancing link reliablility, e.g. satellites diversity
• CPC Class Codes: H04B 7/2041 Spot beam multiple access
• CPC Class Codes: H04B 7/2125 Synchronisation

Abstract

A space diversity system in a TDMA communication system employing a communication satellite, in which in order to equalize the path lengths of respective sending paths at the start of communication, a pre-burst is sent out to one of the paths making up the diversity system in a time slot of one frame assigned to an instant station. A sub-burst is sent out to the other of the paths in the assigned time slot. A relative time difference between the pre-burst and the sub-burst is detected from signals sent back to the instant station from the communication satellite or signals received by a distant terrestral station via the communication satellite. On the basis of the result of a comparison operation of relative time difference between the pre-burst and the sub-burst at the time of their sending-out from the instant station with a relative time difference between the pre-burst and the sub-burst received via the communication satellite, variable delay means inserted in one of the paths is controlled so that the two relative time differences become equal to each other.

Claims

1. A space diversity system in a TDMA communication system employing a communication satellite including:

equalizing means for equalizing the path lengths of respective sending paths at the start of communication;

said equalizing means comprising pre-burst sending means for sending a pre-burst out to one of the paths making up the diversity system in a time slot of one frame assigned to an instant station;

sub-burst sending means for sending a sub-burst out to the other of the paths in the assigned time slot;

time difference detecting means for detecting a relative time difference between the pre-burst and the sub-burst from signals sent back to the instant station from the communication satellite or signals received by a distant terrestrial station via the communication satellite;

comparison means for comparing a relative time difference between the pre-burst and the sub-burst at the time of their sending-out from the instant station with a relative time difference between the pre-burst and the sub-burst received via the communication satellite; and

variable delay means inserted in one of the paths and controlled by said comparison means so that the two relative time differences become equal to each other.

2. A space diversity system in a TDMA communication system employing a communication satellite including:

equalizing means for equalizing the path lengths of respective sending paths at the start of communication;

said equalizing means comprising pre-burst sending means for sending a pre-burst out to one of the paths making up the diversity system in a time slot of one frame assigned to an instant station;

sub-burst sending means for sending a sub-burst out to the other of the paths in the assigned time slot;

time distance detecting means for detecting a relative time difference between the pre-burst and the sub-burst from signals sent back to the instant station from the communication satellite or signals received by a distant terrestrial station via the communication satellite;

comparison means for comparing a relative time difference between the pre-burst and the sub-burst at the time of their sending-out from the instant station with a relative time difference between the pre-burst and the sub-burst received via the communication satellite, variable delay means inserted in one of the paths and controlled by said comparison means so that the two relative time differences become equal to each other;

wherein after the path length equalization at the start of communication, a signal transmitting burst is sent out to a path in operation in the time slot assigned to the station, while a sub-burst is sent out to a stand-by path of diversity in a sub-burst time slot of the frame for each frame or on a time shared basis;

wherein relative time difference between the signal transmitting burst and sub-burst is detected from signals sent back to the station via the communication satellite; and

wherein when the detected relative time difference is different from a predetermined relative time difference between the signal transmitting burst and the sub-burst at the time of their sending-out, said variable delay means inserted in one of the paths is controlled so that the two relative time differences become equal to each other.