Space diversity receiving system for multi-direction time division multiplex communication

• US 4,530,087 A
• Filed: 05/13/1983
• Issued: 07/16/1985
• Est. Priority Date: 05/21/1982
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Yamamoto, Kazuhiro
• Primary Examiner(s): Orsino, Jr., Joseph A.
• Application Number:
  US06/494,116
• Time in Patent Office: 795 Days
• Field of Search: 375/40, 375/100, 455/52, 455/133, 455/134, 455/135, 455/140, 370/104, 371/8
• US Class Current: 370/350
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04L 1/06 using space diversity

Abstract

A space diversity receiving system for the central station of a multi-direction time division multiplex communication network having a plurality of satellite stations, and one central station. Each satellite station transmits signals to the central station during an assigned time slot. The central station receives burst signals from the satellite stations. A first receiver has a main antenna. A second receiver has a supplementary antenna. Both receivers include a demodulator coupled to the corresponding antenna and a detector for detecting bit errors in the resulting demodulated signals, and for providing error pulses when appropriate. Each satellite station, needing space diversity, has a counter for competitively counting the error pulses from the receivers. A signal switcher responds to the demodulated signals and the counter for selecting a demodulated signal having a lower bit error rate.

Claims

1. A space diversity system for a central station of a multi-direction time division multiplex communication network comprising a plurality of satellite stations and one central station, in which each satellite station transmits signals to said central station in a time slot which is individually assigned thereto and said central station receives burst signals from said satellite stations, said central station comprising:

a first receiver means having a main antenna;

a second receiver means having a supplementary antenna, each of said first and second receiver means including demodulator means for demodulating input signals from the corresponding antenna and detector means for producing error pulses responsive to detection of bit errors in the demodulated signals;

counter means individually associated with each satellite station needing space diversity, for competitively counting the error pulses from said first and second receiver means to provide a control signal;

first gate means provided on the input side of each of said counter means for controlling the supplying of said error pulses to said counter means in response to a burst timing signal for identifying each satellite station time slot;

a signal switching means responsive to said demodulated signals and said control signal for selecting and providing as its output the demodulated signal having a lower bit error rate; and

second gate means provided on the output side of each of said counter means for controlling the supplying of said control signal to said signal switching means in response to said burst timing signal.

2. A time division multiplex system comprising a plurality of outlying stations and one central station, each of said outlying stations transmitting during individually associated time slots, means for transmitting digital signals over a plurality of transmission paths between said central station and said outlying stations, at least some of said paths having adverse propagation characteristics, duplicate antenna and receiver means at said central station for receiving signals thus transmitted over each of said paths having adverse characteristics, a plurality of control means for detecting and counting bit errors received from each of said duplicate receiver means, each of said control means being individually associated with a corresponding one of said outlying stations, and gate means on opposite sides of each of said control means for selectively gating the signals from the duplicate receivers through said control means, means for selectively operating said gate means during the time slots assigned to the outlying station which is individually associated with control means, and means responsive to said control means for selecting the one of said duplicate receiver means which has the lower number of bit errors.

3. The system of claim 2, wherein said system is a multi-directional time division multiplex network and each of said outlying stations is a satellite station.

4. A time division multiplex system comprising a plurality of outlying stations and one central station, each of said outlying stations transmitting signals in bursts during time slots which are individually associated with corresponding ones of said outlying stations, means for transmitting digital signals over a plurality of transmission paths between said central station and said outlying stations, at least some of said paths having adverse propagation characteristics, duplicate antenna and receiver means at said central station for receiving signals thus transmitted over each of said paths having adverse characteristics, a plurality of control means for detecting and counting bit errors received from each of said duplicate receiver means, each of said control means being individually associated with a corresponding one of said outlying stations, clock means common to all of said stations for selectively identifying each of said stations, gating means individually associated with each of said plurality of said control means for selectively enabling signals from said corresponding one of said outlying stations to pass through said control means, means responsive to said clock means for simultaneously causing an outlying station to transmit said burst signals and for causing said associated gate means to enable said control means to receive said burst signals, and means responsive to said control means for selecting the one of said duplicate receiver means which has the lower number of bit errors.