Method and apparatus for implementing measurement based dynamic frequency hopping in wireless communication systems

• US 6,826,409 B2
• Filed: 02/14/2003
• Issued: 11/30/2004
• Est. Priority Date: 12/28/1998
• Status: Expired due to Term

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Kostic, Zoran, Sollenberger, Nelson Ray
• Primary Examiner(s): Milord, Marceau
• Application Number:
  US10/366,379
• Publication Number:
  US 20030119534A1
• Time in Patent Office: 655 Days
• Field of Search: 455/501, 455/502, 455/504, 455/513, 455/525, 455/67.1, 455/67.4, 455/62, 455/63, 455/67.16, 455/67.11, 455/63.1, 375/132, 375/130, 370/260, 370/285, 370/203, 370/329
• US Class Current: 455/501
• CPC Class Codes: H04B 1/715 Interference-related aspects
• CPC Class Codes: H04B 2001/7154 with means for preventing interference
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601

Abstract

Proposed is a method for reducing interference in a frequency hopping wireless communications system. In one embodiment of the present invention, a base station and a terminal station each using an orthogonal frequency division multiplexing (OFDM) technique to simultaneously measure an interference level for each system frequency and to enable high speed frequency hop pattern changes which can follow changes in desired and interfering signal levels due to changes in co-channel interference or shadow fading. The terminal station interference level measurement values are then transmitted to the base station. Next, the base station identifies each frequency hop pattern currently in use by each terminal station communicating with that base station. The base station then uses both the base station interference level measurements and the terminal station interference level measurements to identify each frequency hop pattern in which at least one of the current system frequencies should be replaced with a system frequency having a lower interference level. Next, the base station replaces no more than a predetermined number of the current system frequencies within the identified frequency hop pattern(s). The above steps are executed at each base station within the system while ensuring that nearby interfering base stations do not replace frequencies at the same time.

Claims

1. A method of determining a measure of an interference level at each frequency in a plurality of system frequencies available to a multichannel wireless communication system, comprising:

receiving, at a base station, a plurality of measured values representative of an interference level at each frequency in the plurality of system frequencies available to the base station of the multichannel wireless communication system, wherein the interference levels were measured simultaneously;

measuring, simultaneously, at the base station, an interference level at each frequency in the plurality of system frequencies; and

calculating a quality value for each frequency in the plurality of system frequencies using both the interference levels received at the base station and the interference levels measured at the base station.

2. The method of claim 1, wherein receiving occurs one of after a request issued from the base station and continuously.

3. The method of claim 1, wherein measuring is accomplished using orthogonal frequency division multiplexing (OFDM).

4. A method for reducing interference in a frequency hopping wireless communication system comprising a plurality of base stations each adapted to communicate with one or more of a plurality of terminal stations by transmitting one or more of a plurality of system frequencies through a propagation medium, the method comprising the steps of:

measuring, simultaneously, an interference level for each system frequency; and

transmitting values representing said measured interference levels through the propagation medium to a base station.

5. The method of claim 4, wherein said measuring step is accomplished using orthogonal frequency division multiplexing (OFDM).

6. A computer-readable medium whose contents cause a computer system to reduce interference in a wireless communications system comprising a plurality of base stations each adapted to communicate with one or more of a plurality of terminal stations by transmitting one or more of a plurality of system frequencies through a propagation medium, the computer-readable medium performing the steps of:

measuring, simultaneously, an interference level for each system frequency; and

transmitting values representing said measured interference levels through the propagation medium to a base station.

7. The computer-readable medium of claim 6, wherein said measuring step is accomplished using orthogonal frequency division multiplexing (OFDM).