Distributed digital antenna system

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.

What is claimed is: 
     
       1. A distributed digital antenna system comprising:
 a host unit that converts a configured to receive a first signal from a base station communicatively coupled to the host unit and to transmit a second signal to the base station, the host unit further configured to convert the first signal to a transmitted digital optical signal and that converts to convert a received digital optical signal to a the second signal;, wherein the host unit is configured to transmit and receive signals over an optical medium coupled to the host unitto carry the transmitted and received digital optical signals; and 
 a plurality of remote units daisy-chained along the optical medium such that each particular remote unit of the plurality of remote units transmits an analog representation of the transmitted digital optical signal and receives radio frequency signals that are converted by the particular remote unit to a digitized received spectrum, each particular remote unit of the plurality of remote units including a summer that sums the digitized received spectrum with a corresponding digitized received spectrum from any preceding remote unit of the plurality of remote units daisy-chained remote units along the optical medium to generate the received digital optical signal for transmission to the host unit. 
 
     
     
       2. The distributed digital antenna system of  claim 1 , wherein the first signal and the second signals signal are transported over an optical, electrical or wireless medium. 
     
     
       3. The distributed digital antenna system of  claim 1 , wherein the optical medium is an optical fiber. 
     
     
       4. The distributed digital antenna system of  claim 1 and further including a, wherein the base station, coupled to the host unit, that communicates is configured for communicating with subscriber units over a radio frequency air interface. 
     
     
       5. The distributed digital antenna system of claim  4  1, wherein the base station transmits the first signal and receives the second signal. 
     
     
       6. The distributed digital antenna system of claim  4  1, 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 distributed digital antenna system comprising:
 a host unit that converts configured to receive forward link radio frequency signals from the base station and the transmit reverse link radio frequency signals to the base station, the host unit further configured to convert the forward link radio frequency signals received from the base station to forward link digital optical signals and that converts to convert reverse link digital optical signals from the distributed digital antenna system to reverse link radio frequency signals for use by the base station;, wherein the host unit is configured to communicate the forward link digital optical signals across an optical medium coupled to the host unitthat carries the digital optical signals; and 
 a plurality of remote units daisy-chained along the optical medium such that each particular remote unit of the plurality of remote units transmits first radio frequency signals over an air interface as an analog representation of the digital optical signals from the base station and receives second radio frequency signals over the air interface that are converted by a receiving the particular remote unit to a digitized received spectrum, each particular remote unit of the plurality of remote units and the receiving remote unit including a summer that sums the digitized received spectrum with a corresponding digitized received spectrum from any preceding remote unit of the plurality of remote units daisy-chained remote units along the optical medium to generate the received reverse link digital optical signals for use by the host unit. 
 
     
     
       8. The distributed digital antenna system of  claim 7 , wherein the forward link radio frequency signals and the reverse link radio frequency signals communicated between the base station and the host unit are carried over an optical link. 
     
     
       9. The distributed digital antenna system of  claim 7 , wherein the optical medium is an optical fiber that carries multiple wavelengths. 
     
     
       10. The distributed digital antenna 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 distributed digital antenna 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 distributed digital antenna system of  claim 7 , wherein each remote unit of the plurality of remote units each comprise comprises:
 an antenna that communicates the forward link radio frequency signals and the reverse link radio frequency signals over the air interface; 
 a plurality of optical-to-electrical converters that convert forward link digital optical signals input to the remote unit to forward link digital electrical signals and that convert reverse link electrical signals in the digitized received spectrum 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 reverse link radio frequency signals to the reverse link electrical signals in the digitized received spectrum; and 
 wherein the summer sums the reverse link electrical signals in the digitized received spectrum with corresponding reverse link electrical signals in the corresponding digitized received spectrum from the any preceding remote units unit of the plurality of remote units daisy-chained along the optical medium daisy-chain to generate the received reverse link digital optical signals. 
 
     
     
       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 forward link radio frequency signals; 
 an analog-to-digital converter that converts reverse link radio frequency signals from the antenna to a digitized spectrum of reverse link electrical signals; and 
 a summer that sums the reverse link electrical signals in the digitized spectrum from the analog-to-digital converter to with corresponding reverse link electrical signals from the daisy-chain of previous remote units to generate an output digital optical signal. 
 
     
     
       14. The remote unit of  claim 13 and, further including comprising:
 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 output digital optical signal and a second optical-to-electrical converter converts an optical transmit signal from the host unit to the a 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 forward link 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 reverse link digital optical signals, each forward link digital optical signal of the forward link digital optical signals and each reverse link digital optical signal of the reverse link digital optical signals 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 forward link radio frequency signals; 
 an analog-to-digital converter that converts reverse link radio frequency signals from the antenna to a digitized spectrum of reverse link electrical signals; 
 a summer that sums the reverse link electrical signals in the digitized spectrum from the analog-to-digital converter to an output digital optical 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 particular wavelength in the plurality of wavelengths, the wavelength division multiplexer further multiplexes the digital optical signals to the 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 forward link digital optical signal; 
 transmitting the forward link digital optical signal over an optical medium to a plurality of remote units in a daisy-chain configuration along the optical medium; 
 converting the forward link digital optical signal to a forward link digital electrical signal at each remote unit; 
 converting the forward link digital electrical signal to an analog signal for transmission by at least one of the plurality of remote units as a second radio frequency signal; 
 receiving a third radio frequency signal over an air interface of the at least one of the plurality of remote units; 
 converting the third radio frequency signal to a received reverse link electrical signal within a digitized spectrum; and 
 summing the digitized spectrum of the received reverse link electrical signal with a corresponding digitized spectrum of received reverse link electrical signals from previous remote units in the daisy-chain configuration. 
 
     
     
       18. The method of  claim 17 and, further including comprising:
 converting a result of the summing of the digitized spectrum of the received reverse link electrical signal with the corresponding digitized spectrum of the reverse link electrical signals from the previous remote units in the daisy-chain configuration to a reverse link digital optical signal; 
 transmitting the reverse link digital optical signal over the optical medium; and 
 converting the reverse link digital optical signal to a fourth radio frequency signal for use by the base station. 
 
     
     
       19. The method of  claim 17 and, further including comprising:
 demultiplexing the forward link 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 comprising: 
 transmitting information in the fourth radio frequency signal from the base station to a public switched telephone network. 
 
     
     
       21. The method of  claim 18 and, further including comprising:
 multiplexing single wavelength optical signals from the a particular remote unit into a single optical signal comprising a plurality of wavelengths. 
 
     
     
       22. A method for a 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 electrical signal; 
 summing a digitized spectrum of the reverse link electrical signal with a corresponding digitized spectrum of other reverse link electrical signals from other remote terminals that are daisy-chained together over an optical link to create a summed digitized spectrum of reverse link electrical signals; and 
 converting the summed digitized spectrum of reverse link electrical signals to a reverse link summed optical signal for transmission to a host unit communicatively coupled to a base station. 
 
     
     
       23. The system method of claim  1 22, wherein further comprising:
 receiving, at the host unitreceives, a total digitized received spectrum representing thea sum of all digitized received spectrum from thea plurality of remote unitsterminals including the remote terminal and the other remote terminals. 
 
     
     
       24. The method of claim  22 23, wherein the summed digitized spectrum of reverse link electrical signals represents a sum of the digitized spectrum of the reverse link electrical signals of all the plurality of remote terminalsthat are daisy-chained together over the optical link. 
     
     
       25. A distributed digital antenna system comprising:
 a host unit configured to receive a first signal from a base station communicatively coupled to the host unit and to transmit a second signal to the base station, the host unit further configured to convert the first signal to a transmitted digital signal and to convert a received digital signal to the second signal, wherein the host unit is configured to transmit and receive signals over a medium coupled to the host unit; and   a plurality of remote units daisy-chained along the medium such that each particular remote unit of the plurality of remote units transmits an analog representation of the transmitted digital signal and receives radio frequency signals that are converted by the particular remote unit to a digitized received spectrum, each particular remote unit of the plurality of remote units including a summer that sums the digitized received spectrum with a corresponding digitized received spectrum from any preceding remote unit of the plurality of remote units daisy-chained along the optical medium to generate the received digital signal for transmission to the host unit.