Method for estimating the downlink capacity in a spread spectrum wireless communications system

• US 20060211427A1
• Filed: 05/04/2005
• Published: 09/21/2006
• Est. Priority Date: 03/17/2005
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Inventors: Yang, Hong, Zhou, Hai, Newbury, Mark E., Azman, Utku, Casado-Fernandez, Monica
• Granted Patent: US 7,400,887 B2
• Time in Patent Office: Days
• US Class Current: 455/450
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic

Abstract

The per sector or per cell downlink capacity in a spread spectrum wireless network is determined using a single test mobile that is operating within a background of simulated co-channel interference being broadcast in each sector by all cell sites in the network whose capacity is of interest. From all sectors, an Orthogonal Channel Noise Simulator (OCNS) generates a multiple number of calibrated test signals, which are aggregated and broadcast downlink, where each transmitted test signal simulates the downlink power transmitted to a live mobile. Each component test signal in the aggregated OCNS output transmitted in each sector is a sample of a stochastic process with a set mean and standard deviation that are determined from the mean and standard deviation of the power of a real signal transmitted downlink to the test mobile as it is moved around the network'"'"'s coverage area. The capacity of the sector is determined by increasing the number of test signals in each aggregated OCNS output until measurable performance is compromised.

Claims

1. A method of determining capacity in a wireless network in which plural signals are transmitted on a shared downlink channel to plural mobiles within a coverage area of the network, the method comprising:

a) transmitting a real signal on the downlink channel to a test mobile as it is moved on a test route within the network'"'"'s coverage area;

b) transmitting an aggregate of a first plurality of test signals on the downlink channel, each test signal being a sample of a stochastic process that is calibrated to at least one predetermined statistical characteristic of the real signal transmitted to the test mobile that is measured as the test mobile is moved on the test route;

c) determining whether or not an acceptable performance is indicated by at least one predetermined measurable performance characteristic when the real signal and the plurality of test signals are being transmitted as the test mobile is being moved on the test route; and

d) if acceptable performance is determined, determining that the downlink channel has the capacity of handling downlink traffic to at least the first plurality of mobiles.

2. The method of claim 1 wherein if acceptable performance is determined, increasing the first plurality to a second plurality, the second plurality being a greater number than the first plurality, and repeating a) through d) to determine whether the acceptable performance is indicated with the second plurality, and if acceptable performance is indicated with the second plurality, determining that the downlink channel has the capacity of handling downlink traffic to at least this second plurality of mobiles.

3. The method of claim 2 wherein if acceptable performance is determined at the second plurality, increasing the second plurality to successively greater numbers and repeating a) through d) to determine whether acceptable performance is determined for each successively greater number until a plurality is reached at which unacceptable performance is determined.

4. The method of claim 1 wherein if acceptable performance is not determined, decreasing the first plurality to a second plurality, the second plurality being a smaller number than the first plurality, and repeating a) through d) to determine whether the acceptable performance is indicated with the second plurality, and if acceptable performance is determined, determining that the downlink channel has the capacity of handling downlink traffic to at least this second plurality of mobiles.

5. The method of claim 4 wherein if acceptable performance is not determined at the second plurality, decreasing the second plurality to successively smaller numbers and repeating a) through d) to determine whether acceptable performance is determined for each successively smaller eater number until a plurality is reached at which acceptable performance is determined.

6. The method of claim 1 wherein the at least one predetermined statistic characteristic of the real signal transmitted to the test mobile is at least one of a mean and a variance of the real signal.

7. The method of claim 1 wherein the at least one predetermined performance criteria is at least one of an average downlink error rate being greater than a predetermined error rate;

and a percentage of time that a downlink amplifier is in an overload state being greater than a predetermined percent.