Synchronous multiport digital 2-way communications network using T1 PCM on a CATV cable

• US 5,124,980 A
• Filed: 03/20/1989
• Issued: 06/23/1992
• Est. Priority Date: 03/20/1989
• Status: Expired due to Fees

• Current Assignee: Gerald G. Maki
• Original Assignee: Gerald G. Maki
• Inventors: Maki, Gerald G.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): KIZOU, HASSAN
• Application Number:
  US07/325,857
• Time in Patent Office: 1,191 Days
• Field of Search: 455/5, 455/3, 455/4, 455/6, 455/234, 455/235, 370/95.2, 370/95.3, 370/85.8, 370/85.1, 370/105.1, 370/103, 370/4, 370/100.1, 370/77, 370/79, 370/85.7, 370/95.1, 370/113, 340/825.08, 379/92, 379/90, 375/109, 375/98, 358/85, 358/86
• US Class Current: 370/498
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04N 7/10 Adaptations for transmission by electrical cable H04N7/12 takes precedence
• CPC Class Codes: H04N 7/173 with two-way working, e.g. subscriber sending a programme selection signal

Abstract

A Synchronous Multiport Digital Communications Network (SMDCN) including a HEAD end Unit (HEADU) and SUBscriber Units (SUBU) providing a large number of simultaneous isolated two-way dial-up digital communications channels between a common head end facility and a large number of subscriber facilities over a broadband transmission medium such as coaxial cable or optical fiber arranged in a bus or tree topology, such as a local area network (LAN) or a cable television (CATV) network. The basic digital channel provided is a 64,000 bit per second data stream, the current standard of the digital telephone industry'"'"'s T1 technology, and therefore readily accommodates voice telephone services. However, the network expressly accommodates higher bit rates up to 1.544 MB/s by combining basic channels. The SMDCN, through utilization of a novel system-wide synchronization technique, allows the provision of standard digital telephone T1 communications services with subscriber access available on an individual DSO channel basis to residential and business subscribers over such a network. This allows a CATV system operator to provide telephone and computer networking services and new pay-per-view entertainment services to his subcribers, in addition to the normal video entertainment services, over the same cable. The CATV network thereby becomes a "local loop" providing all the services a local telephone company offers. In addition, in a Local Area Network (LAN) application, the SMDCN provides major improvement over current technologies in utilization of transmission medium bandwidth, accommodating a larger number of users over a significantly longer network.

Claims

1. A communication system comprising a central head end station connected to a multichannel transmission medium and a plurality of remote stations also connected to said transmission medium at various distances from said head end station, said head end station including receiver means for receiving from said plurality of remote stations a serial synchronous time domain multiplex data stream in baseband or modulated signal form containing a plurality of sequential time slots arranged in a repetitious data frame, each time slot dedicated at any given instant to contain a data word of a predetermined number of bits transmitted by one particular remote station of said plurality of remote stations, and automatic gain control means, hereinafter referred to as AGC means, for setting the gain of said receiver means to an optimum independent value for each of said time slots at or immediately prior to the beginning of each of said time slots, wherein said AGC means includes memory means for storing an independent automatic gain control value, hereinafter referred to as AGC value, associated with each time slot, measurement means for measuring the signal amplitude of said data stream received in each time slot, and correcting means for automatically correcting each of said stored AGC values to compensate for variations in signal level of said data stream.

2. A communication system according to claim 1 wherein said transmission medium consists of one or more broadband cables or one or more optical fibers or a combination of broadband cables and optical fibers.

3. A communications system according to claim 1 wherein said serial synchronous time domain multiplex data stream is of the type known in the telecommunications industry as a T1 multiplex.

4. A communications system according to claim 2 wherein said serial synchronous time domain multiplex data stream is of the type known in the telecommunications industry as a T1 multiplex.

5. In a communication system comprising a central head end station connected to a multichannel transmission medium and a plurality of remote stations also connected to said transmission medium at various distances from said head end station, said head end station including receiver means for receiving from said plurality of remote stations a serial synchronous time domain multiplex data stream in baseband or modulated signal form containing a plurality of sequential time slots arranged in a repetitious data frame, each time slot dedicated at any given instant to contain a data word of a predetermined number of bits transmitted by one of said plurality of remote stations, a method of controlling the gain of said receiver means in a manner to maintain the receiver output at the correct level for optimum detection of every data bit in each of said time slots while receiver input signal level of said data stream varies from one time slot to the next, said method comprising the steps of:

storing in memory means an AGC value for each time slot(, and storing said initial value in memory means);

recalling said AGC value from said memory means at or immediately prior to the beginning of each time slot and applying it to set the gain of said receiver for the duration of said time slot;

measuring the level of said data stream signal occurring within said time slot within said receiver;

comparing said measured data stream signal level with an optimum reference level;

incrementing or decrementing said AGC value by zero, one or more counts each frame in the proper direction to drive said receiver data stream signal level closer to said optimum reference level; and

storing the new AGC value back into said memory means for use at the appropriate time slot of a following frame.

6. A method according to claim 5 in a communication system utilizing a serial synchronous time domain multiplex data stream of the type known in the telecommunications industry as a T1 multiplex.

7. In a communication system comprising a central head end station connected to a multichannel transmission medium and a plurality of remote stations also connected to said transmission medium at various distances from said head end station, the central head end station including:

receiver means for receiving a serial synchronous time domain multiplex data stream in baseband or modulated signal form, said data stream containing a plurality of sequential time slots arranged in a repetitious data frame;

AGC means for setting the gain of said receiver means to an optimum value for the duration of each of said time slots at the beginning of each of said time slots, said AGC means including memory means for storing an independent automatic gain control value associated with each time slot, measurement means for measuring the amplitude of said data stream signal received in each time slot, and correcting means for automatically correcting each of said stored AGC values as required to compensate for variations in signal level of said received data stream.