Distributed digital antenna system

• US 20040106435A1
• Filed: 03/24/2003
• Published: 06/03/2004
• Est. Priority Date: 12/03/2002
• Status: Active Grant

• Current Assignee: CommScope Technologies, LLC (CommScope Holding Company, Inc.)
• Original Assignee: ADC Telecommunications Incorporated (TE Connectivity Limited)
• Inventors: Bauman, Donald R., Wala, Philip M., Brennan, Jeffrey O.
• Granted Patent: US 8,958,789 B2
• Time in Patent Office: Days
• US Class Current: 455/562.1
• CPC Class Codes: H04B 1/40 Circuits
• CPC Class Codes: H04B 10/25755 Ring network topology
• CPC Class Codes: H04B 10/25756 Bus network topology
• CPC Class Codes: H04B 10/25759 Details of the reception of RF signal or the optical conversion before the optical fibre
• CPC Class Codes: H04W 16/26 Cell enhancers or enhancement, e.g. for tunnels, building shadow
• CPC Class Codes: H04W 88/085 Access point devices with remote components

Abstract

An optical medium, such as fiber, is tapped to provide an antenna port wherever radio service coverage is desired. Each antenna port is a bi-directional remote unit that receives a digital optical signal from a host unit and transforms the signal to a radio frequency signal for transmission by the remote unit. The remote unit receives radio frequency signals that are converted to digital signals and summed with signals from other remote units and converted to an optical signal for transmission to the host unit.

Claims

1. A distributed digital antenna system comprising:

a host unit that converts a first signal to a transmitted digital optical signal and that converts a received digital optical signal to a second signal;

an optical medium coupled to the host unit to carry the transmitted and received digital optical signals; and

a plurality of remote units daisy-chained along the optical medium such that each remote unit transmits an analog representation of the transmitted digital optical signal and receives a radio frequency signal that is converted by the remote unit to the received digital optical signal.

2. The system of claim 1 wherein the first and second signals are transported over an optical, electrical or wireless medium.

3. The system of claim 1 wherein the optical medium is an optical fiber.

4. The system of claim 1 and further including a base station, coupled to the host unit, that communicates with subscriber units over a radio frequency air interface.

5. The system of claim 4 wherein the base station transmits the first signal and receives the second signal.

6. The system of claim 4 wherein the base station communicates signals from the host unit to a public switched telephone network.

7. A distributed digital antenna system that communicates signals with a base station that is coupled to a data network, the system comprising:

a host unit that converts radio frequency signals from the base station to digital optical signals and that converts digital optical signals from the digital antenna system to radio frequency signals for use by the base station;

an optical medium coupled to the host unit that carries the digital optical signals; and

a plurality of remote units daisy-chained along the optical medium such that each remote unit transmits radio frequency signals over an air interface as an analog representation of the digital optical signals from the base station and receives radio frequency signals over the air interface that are converted by a receiving remote unit to digital optical signals for use by the host unit.

8. The system of claim 7 wherein the radio frequency signals between the base station and the host unit are carried over an optical link.

9. The system of claim 7 wherein the optical medium is an optical fiber that carries multiple wavelengths.

10. The system of claim 7 wherein the optical medium is a first optical fiber that carries a first wavelength from the host unit to the plurality of remote units and a second optical fiber that carries a second wavelength from the plurality of remote units to the host unit.

11. The system of claim 10 wherein the second wavelength carries a digital signal that represents a summation of signals received by each of the plurality of remote units.

12. The system of claim 9 wherein the plurality of remote units each comprise:

an antenna that communicates the radio frequency signals over the air interface;

a plurality of optical-to-electrical converters that convert the forward link digital optical signals input to the remote unit to forward link digital electrical signals and that convert reverse link digital electrical signals to reverse link digital optical signals for output to the host unit;

a digital to analog converter that converts the forward link digital electrical signals to the analog representation;

an analog-to-digital converter that converts the received radio frequency signals to the reverse link digital electrical; and

a summer that sums the reverse link digital electrical signals with reverse link digital signals from previous remote units of the optical medium daisy-chain to generate a summation signal.

13. A remote unit in a distributed digital antenna system that communicates signals with a base station, the remote unit comprising:

an antenna that communicates radio frequency signals using an air interface standard;

a plurality of optical-to-electrical converters that convert input digital optical signals, from a host unit coupled to the base station and a daisy-chain of previous remote units, to forward link digital electrical signals;

a digital to analog converter that converts the forward link digital electrical signals to analog signals for transmission by the antenna as radio frequency signals;

an analog-to-digital converter that converts radio frequency signals from the antenna to reverse link digital electrical signals; and

a summer that sums the reverse link digital electrical signals from the analog-to-digital converter to reverse link digital signals from the daisy-chain of previous remote units to generate a digital summation signal.

14. The remote unit of claim 13 and further including:

a first optical port that is coupled to either the host unit or a subsequent remote unit of the daisy-chain of remote units; and

a second optical port that is coupled to the daisy-chain of previous remote units.

15. The remote unit of claim 13 wherein a first optical-to-electrical converter of the plurality of optical-to-electrical converters converts an optical summation signal from the daisy-chain of previous remote units to the digital summation signal and a second optical-to-electrical converter converts an optical transmit signal from the host unit to the forward link digital electrical signal for conversion to an analog signal by the digital to analog converter.

16. A remote unit in a distributed digital antenna system that communicates signals with a base station, the remote unit comprising:

an antenna that communicates radio frequency signals using an air interface standard;

a plurality of optical-to-electrical converters that convert digital optical signals, from a host unit coupled to the base station and a daisy-chain of previous remote units, to forward link digital electrical signals, the plurality of optical-to-electrical converters further convert reverse link digital electrical signals to digital optical signals, each digital optical signal comprising a wavelength;

a digital to analog converter that converts the forward link digital electrical signals to analog signals for transmission by the antenna as radio frequency signals;

an analog-to-digital converter that converts radio frequency signals from the antenna to reverse link digital electrical signals;

a summer that sums the reverse link digital electrical signals from the analog-to-digital converter to a digital summation signal from the daisy-chain of previous remote units; and

a wavelength division multiplexer that demultiplexes an input digital optical signal, comprising a plurality of wavelengths, to the digital optical signals each having a wavelength in the plurality of wavelengths, the wavelength division multiplexer further multiplexes digital optical signals to an output digital optical signal comprising the plurality of wavelengths.

17. A method for communicating over a distributed digital antenna system, the method comprising:

converting a first radio frequency signal from a base station to a digital optical signal;

transmitting the digital optical signal over an optical medium to a plurality of remote units in a daisy-chain configuration along the optical medium;

converting the digital optical signal to a forward link digital electrical signal at each remote unit; and

converting the forward link digital electrical signal to an analog signal for transmission by at least one of the remote units as a second radio frequency signal.

18. The method of claim 17 and further including:

a remote unit receiving a third radio frequency signal over an air interface;

converting the third radio frequency signal to a received digital electrical signal;

summing the received digital electrical signal with an input summation signal from previous remote units in the daisy-chain configuration;

converting a result of the summing to a sum digital optical signal;

transmitting the sum digital optical signal over the optical medium; and

converting the sum digital optical signal to a fourth radio frequency signal for use by the base station.

19. The method of claim 17 wherein the digital optical signal comprises a plurality of wavelengths and further including demultiplexing the digital optical signal into a plurality of optical signals each having one wavelength.

20. The method of claim 18 and further including the base station transmitting information in the fourth radio frequency signal to a public switched telephone network.

21. The method of claim 18 and further including multiplexing single wavelength optical signals from the remote unit into a single optical signal comprising a plurality of wavelengths.

22. A method for communicating with a wireless terminal in a geographic area, the method comprising:

transmitting forward link signals to a plurality of fiber optic daisy-chain connected remote antennas;

at the remote antennas, transmitting the forward link signals to the wireless terminal;

receiving reverse link signals from the wireless terminal at at least one of the plurality of fiber optic daisy-chain connected remote antennas; and

summing and forwarding the received reverse link signals at each remote terminal of the daisy-chained remote terminals.

23. A method for remote terminal to communicate with a wireless terminal in a geographic area, the method comprising:

converting an optical signal to a forward link electrical signal;

converting the forward link electrical signal to a forward link analog signal;

transmitting the forward link analog signal to the wireless terminal;

receiving a reverse link analog signal from the wireless terminal;

converting the reverse link analog signal to a reverse link digital signal;

summing the reverse link digital signal with other reverse link digital signals from other remote terminals that are daisy-chained together over an optical link; and

converting the summed reverse link digital signal to a reverse link summed optical signal for transmission to a host unit.