System and method for reducing cumulative noise in a distributed antenna network

• US 6,128,470 A
• Filed: 07/18/1996
• Issued: 10/03/2000
• Est. Priority Date: 07/18/1996
• Status: Expired due to Term

• Current Assignee: Entrust Technologies Limited, Unwired Planet LLC (JP Morgan Chase & Co)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Eckstein, Larry, Huffman, Jacque, Naidu, Arun
• Primary Examiner(s): RAO, ANAND SHASHIKANT
• Application Number:
  US08/683,187
• Time in Patent Office: 1,538 Days
• Field of Search: 455/422, 455/33.1, 455/33.2, 455/33.3, 455/33.4, 455/54.1, 455/56.1, 455/52.1, 455/50.1, 455/10, 455/14, 455/15, 455/16, 455/17, 455/18, 455/19, 379/58, 379/59, 379/60
• US Class Current: 455/16
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
• CPC Class Codes: H04B 7/0802 using antenna selection H04B7/0868 takes precedence; antenna beam directivity switching H01Q3/24

Abstract

A communications system and method are provided for reducing noise in a distributed antenna network. The system includes a plurality of remote antenna units with each remote antenna unit including a receiver for receiving input signals, a signal strength processor for determining whether a valid signal is present at its respective remote antenna unit and an output controller for switching off the network connection when no valid signal is present. As a result, the cumulative noise generated by uplink stages connected to the remote antenna units is reduced by switching off the network connection of remote antennas that are do not have to be connected. The communications system and method may further include an output controller for controlling the output for its respective remote antenna unit based on the comparison by the signal strength processor. The output controller may control the network connection of the remote antennas by switching off their connection to the network when the signal strength processor determines that the signal strength level is below a noise threshold level. The output controller may control the output of the remote antenna units by switching off their connection to the network when the signal strength processor determines that the signal strength level is below a noise threshold level and by switching on the connection to the network when the input signal strength level is greater than or equal to the noise threshold level.

Claims

1. A communication system for reducing noise in a distributed antenna network, comprising:

a plurality of remote antenna units, each of said remote antenna units including,

a receiver for receiving input signals,

a signal strength processor for detecting levels of said input signals for said remote antenna unit and comparing the levels of said input signals with first and second noise threshold levels, and

an output controller for switching off a network connection for said remote antenna unit when said signal strength processor determines that the levels of said input signals are less than the first noise threshold level and switching on the network connection for said remote antenna unit when said signal strength processor determines that the levels of said input signals are greater than or equal to the second noise threshold level, wherein the second noise threshold level is greater than the first noise threshold level, and wherein a) when the levels of the input signals are between the first and second noise threshold levels and the network connection for the remote antenna unit is off, and then the levels of the input signals meet the second noise threshold level, the output controller switches on the network connection for the remote antenna unit; and

b) when the levels of the input signals are between the first and second noise threshold levels and the network connection for the remote antenna unit is on, and then the levels of the input signals cross the first noise threshold level, the output controller switches off the network connection for the remote antenna unit; and

a central unit for remotely adjusting the first and second noise threshold levels for each remote antenna unit.

2. A communication system according to claim 1, wherein at least one of the first and second noise threshold levels is set slightly greater than the noise floor of the uplink for the remote antenna units.

3. A communication system according to claim 1, wherein said signal strength processor comprises:

a signal strength detector for detecting the level of said input signals;

a threshold reference generator for variably setting the first and second noise threshold levels, wherein the central Unit remotely controls the threshold reference generator; and

a comparator for comparing the levels of said input signals with the first and second noise threshold levels.

4. A communication system for reducing cumulative noise in the uplink stages of a distributed antenna network, comprising:

transceivers for sending and receiving information;

a plurality of remote antenna units operatively communicative with said transceiver, each of said remote antenna units including,

a receiver for receiving input signals,

a signal strength processor for detecting levels of said input signals for said remote antenna unit and comparing the levels of said input signals with first and second noise threshold levels, and

an output controller for switching the output of said remote antenna unit on and off in response to the comparison by said signal strength processor; and

a central unit for remotely adjusting the first and second noise threshold levels for each remote antenna unit, wherein

said output controller switches on the connection between the network and said remote antenna unit when said signal strength processor determines that the levels of said input signal are greater than or equal to the second noise threshold level and said output controller switches off the connection between the network and said remote antenna unit off when said signal strength processor determines that the levels of said input signal are less than the first noise threshold level, wherein the second noise threshold level is greater than the first noise threshold level, and wherein a) when the levels of the input signals are between the first and second noise threshold levels and the network connection between the network and the remote antenna unit is off, and then the levels of the input signals meet the second noise threshold level, the output controller switches on the network connection between the network and the remote antenna unit; and

b) when the levels of the input signals are between the first and second noise threshold levels and the network connection between the network and the remote antenna unit is on, and then the levels of the input signals cross the first noise threshold level, the output controller switches off the network connection between the network and the remote antenna unit.

5. A communication system according to claim 4, wherein said receiver in each of said remote antenna units comprises:

an antenna for receiving an RF input signal;

a low noise amplifier and a preselecting filter for amplifying and filtering said RF input signal;

a first local oscillator, a first mixer and an intermediate filter for processing the filtered RF input signal; and

a second local oscillator and a second mixer for further processing the signal output from said intermediate filter.

6. A communication system according to claim 4, wherein said signal strength processor comprises:

a signal strength detector for detecting the levels of said input signals;

a threshold reference generator for variably setting the first and second noise threshold levels, wherein the central unit remotely controls the threshold reference generator; and

a comparator for comparing the levels of said input signals with the first and second noise threshold levels.

7. A communication system according to claim 6, wherein said signal strength detector comprises a predetermined number of logarithmic amplifiers and a rectifier.

8. A communication system according to claim 4, wherein said output controller comprises a switch for controlling the connection between the output of said remote antenna unit and the network.

9. A communication system according to claim 4, wherein said transceivers are connected to said remote antenna units by an analog transmission media which transports radio signals therebetween.

10. A communication system according to claim 4, wherein at least one of the first and second noise threshold levels is set to be slightly above the noise floor of the uplink for each of said remote antenna units and the network.

11. A communication system for reducing noise in a distributed antenna network, comprising:

a plurality of remote antenna units, each of said remote antenna units including,

a receiver for receiving input signals,

a signal strength processor for detecting levels of said input signals for said remote antenna unit and comparing the levels of said input signals with first and second noise threshold levels, and

an output controller for switching the output of said remote antenna unit on and off in response to the comparison by said signal strength processor; and

a central unit for remotely adjusting the parameters for each of the plurality of remote antenna units, wherein

said output controller switches on the connection between the network and said remote antenna unit when said signal strength processor determines that the levels of said input signal are greater than or equal to the second noise threshold level and said output controller switches off the connection between the network and said remote antenna unit off when said signal strength processor determines that the levels of said input signal are less than the first noise threshold level, wherein the second noise threshold level is greater than the first noise threshold level, and wherein a) when the levels of the input signals are between the first and second noise threshold levels and the network connection between the network and the remote antenna unit is off, and then the levels of the input signals meet the second noise threshold level, the output controller switches on the network connection between the network and the remote antenna unit; and

b) when the levels of the input signals are between the first and second noise threshold levels and the network connection between the network and the remote antenna unit is on, and then the levels of the input signals cross the first noise threshold level, the output controller switches off the network connection between the network and the remote antenna unit.

12. A method for reducing noise in a distributed antenna network of a communication system comprising the steps of:

(a) receiving input signals by a plurality of remote antenna units;

(b) detecting levels of said input signals and comparing the levels of said input signals with first and second noise threshold levels, wherein the second noise threshold level is greater than the first noise threshold level; and

(c) switching off the connection between the network and said remote antenna units when said step (b) determines that said input signals are less than first noise threshold level and switching on the connection between the network and said remote antenna units when said step (b) determines that said input signals are greater than or equal to the second noise threshold level.

13. A method according to claim 12, wherein at least one of the first and second noise threshold levels is set slightly greater than the noise floor of the uplink for the remote antenna units.

14. A method according to claim 12, wherein said step (b) further comprises the steps of:

(b)(1) detecting the level of said input signals;

(b)(2) remotely adjusting the first and second noise threshold levels; and

(b)(3) comparing the level of said input signal with the first and second noise threshold levels.

15. A method for reducing cumulative noise in the uplink stages of a distributed antenna network of a communication system, comprising the steps of:

(a) sending and receiving information;

(b) receiving input signals sent at said step (a) by a plurality of remote antenna units;

(c) detecting the level of said input signals and comparing the level of said input signals with first and second noise threshold levels, wherein the second noise threshold level is greater than the first noise threshold level; and

(d) switching the connection between the network and said remote antenna units on and off in response to the comparison of step (c) by connecting the network and said remote antenna unit when said step (c) determines that the level of said input signal is greater than or equal to the second noise threshold level, and disconnecting the network and said remote antenna unit when said step (c) determines that the level of said input signal is less than the first noise threshold level.

16. A method according to claim 15, wherein said step (c) further comprises the steps of:

(c)(1) detecting the level of said input signals;

(c)(2) remotely adjusting the first and second noise threshold levels; and

(c)(3) comparing the level of said input signal with the first and second noise threshold levels.

17. A method according to claim 15, wherein at least one of the first and second noise threshold levels is set to be slightly above the noise floor of the uplink stage at the output for each of said remote antenna units and the network.

18. A method for reducing noise in a distributed antenna network of a communication system, comprising the steps of:

(a) receiving input signals by a plurality of remote antenna units;

(b) determining whether or not a valid signal is present at each of the plurality of remote antenna units based on first and second noise threshold levels for each of the plurality of remote antenna units, wherein the second noise threshold level is greater than the first noise threshold level, a valid signal is not present at the remote antenna unit when the level of the input signal is less than the first noise threshold level for the remote antenna unit, and a valid signal is present at the remote antenna unit when the level of the input signal is greater than or equal to the second noise threshold level for the remote antenna unit;

(c) disconnecting each remote antenna unit from the network when said signal strength processor determines that a valid signal is not present at the remote antenna unit, and connecting the network and each remote antenna unit when the signal strength processor determines that a valid signal is present at the remote antenna unit; and

(d) remotely adjusting the first and second noise threshold levels for each of the plurality of remote antenna units.