Broadband communication system for efficiently transmitting broadband signals

• US 6,417,949 B1
• Filed: 11/05/1999
• Issued: 07/09/2002
• Est. Priority Date: 11/05/1999
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Farhan, Forrest M., Quesenberry, Paul E.
• Primary Examiner(s): Pascal, Leslie
• Assistant Examiner(s): Phan, Hanh
• Application Number:
  US09/434,267
• Time in Patent Office: 977 Days
• Field of Search: 359/180, 359/181, 359/173, 359/184, 359/154, 341/504, 341/110, 375/242, 375/245, 375/259, 375/295, 375/316, 375/243, 375/254
• US Class Current: 398/141
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 12/2874 Processing of data for distribution to the subscribers
• CPC Class Codes: H04L 2212/00 Encapsulation of packets

Abstract

A broadband communication system (60), such as a cable television system, includes a forward path for transmitting information from headend equipment to subscribers and a reverse path for transmitting information from the subscribers to the headend equipment. The reverse path includes a transmitting station (65) that receives a first analog signal, converts the first analog signal to a first digital signal having a first number of bits, encodes the first digital signal to generate a second digital signal having a second number of bits less than the first number of bits, then optically transmits the second digital signal. A receiving station (70), also located in the reverse path, receives the second digital signal, decodes the second digital signal to generate a third digital signal having a third number of bits greater than the second number of bits, then converts the third digital signal to a second analog signal that approximates the first analog signal.

Claims

1. A broadband communication system, comprising:

a transmitting station that receives a first broadband signal having a Gaussian distribution, converts the first broadband signal to a first digital signal having a first number of bits, encodes the first digital signal to generate a second digital signal having a second number of bits less than the first number of bits, then optically transmits the second digital signal,

wherein encoding calculations send higher resolution digital signals for signals located in high probability areas of the Gaussian distribution, and wherein encoding calculations send lower resolution digital signals for signals located in lower probability areas of the Gaussian distribution; and

a receiving station that receives the second digital signal, decodes the second digital signal to generate a third digital signal having a third number of bits greater than the second number of bits, then converts the third digital signal to a second broadband signal that approximates the first broadband signal.

2. The communication system of claim 1, wherein the transmitting station comprises:

an analog-to-digital (A/D) converter for converting the first broadband signal to the first digital signal;

an encoder for encoding the first digital signal in accordance with an encoding map to generate the second digital signal,

wherein the encoding map is determined by the encoding calculations, and wherein the encoding calculations dynamically match the first broadband signal with an amplitude probability function of the first broadband signal and remove bits from the first digital signal in accordance therewith; and

a transmitter for transmitting the second digital signal.

3. The communication system of claim 2, wherein the receiving station comprises:

a receiver for receiving the second digital signal;

a decoder for decoding the second digital signal in accordance with a decoding map to generate the third digital signal,

wherein the decoding map is determined by decoding calculations; and

a digital-to-analog (D/A) converter for converting the third digital signal to the second broadband signal.

4. The communication system of claim 3, wherein the first number of bits included in the first digital signal is equal to the third number of bits included in the third digital signal.

5. The communication system of claim 3, wherein the first number of bits included in the first digital signal is not equal to the third number of bits included in the third digital signal.

6. The communication system of claim 3, wherein the transmitter of the transmitting station receives a first electrical signal that is converted to a digital optical signal for transmission.

7. The communication system of claim 6, wherein the receiver of the receiving station receives the digital optical signal and converts it to a second electrical signal.

8. A broadband communication system, comprising:

a transmitting station for receiving a first analog signal and transmitting an optical signal, the transmitting station including;

an analog-to-digital (A/D) converter for converting the first analog signal to a first digital signal having a first number of bits;

an encoder for encoding the first digital signal to generate a second digital signal having a second number of bits less than the first number of bits,

wherein the encoder encodes according to an encoding map, and wherein the encoding map is determined by encoding calculations that reduces the re-quantization error for frequently transmitted amplitudes of the first analog signal by removing rarely transmitted bits of the first analog signal;

a transmitter for transmitting the second digital signal as the optical signal; and

a receiving station for processing the optical signal, the receiving station including;

a receiver for receiving the second digital signal;

a decoder for decoding the second digital signal to generate a third digital signal having a third number of bits greater than the second number of bits; and

a digital-to-analog (D/A) converter for converting the third digital signal to a second analog signal that approximates the first analog signal.

9. The broadband communication system of claim 8, further comprising:

an optical communication channel for coupling the transmitting station and the receiving station.

10. The broadband communication system of claim 9, wherein the first number of bits included in the first digital signal is equal to the third number of bits included in the third digital signal.

11. The broadband communication system of claim 9, wherein the first number of bits included in the first digital signal is not equal to the third number of bits included in the third digital signal.