Closed loop power control for TDMA links

• US 6,747,960 B2
• Filed: 12/21/2001
• Issued: 06/08/2004
• Est. Priority Date: 12/21/2001
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Tillotson, Brian Jay
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): Lee, Andy
• Application Number:
  US10/032,346
• Publication Number:
  US 20030117981A1
• Time in Patent Office: 900 Days
• Field of Search: 370/316, 370/317, 370/318, 370/320, 370/326, 370/321, 370/330, 370/331, 370/332, 370/336, 370/345, 370/347, 455/436, 455/440, 455/443, 455/9, 455/10, 455/13.1, 455/13.4, 455/501, 455/504, 455/507, 455/522, 455/63.1, 455/67.13, 455/67.16
• US Class Current: 370/318
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/228 using past power values or information
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment

Abstract

A method and apparatus for implementing closed loop power control for RF transmissions over a plurality of TDMA links. A data file including of the power level and time interval for each transmission from a given primary node to each one of a plurality of secondary nodes in a TDMA network is maintained in a buffer. Power level correction messages are transmitted by each secondary node back to the primary node indicating a power correction needed to maintain closure of a communication link with a given secondary node. The power level of subsequent transmissions from the primary node are modified such that only that amount of power needed to maintain closure of the link with each secondary node is used. Time stamp information from each secondary node is also used to update the buffer to ensure that power level corrections are being accurately applied. The system and method thus helps to avoid situations of interference with other non-target nodes or devices which might occur if a higher power level than necessary is used in communicating with each of the secondary nodes.

Claims

1. A method for controlling a transmit power of a signal transmitted from a first communication node to a plurality of secondary communication nodes communicating with said first node, in closed loop fashion, in accordance with a multiplexed communication scheme, said method comprising:

using said first node to transmit a signal to a selected one of said secondary nodes;

creating a data file for said transmitted signal, said data file including a transmit power level value indicative of a power level of said transmitted signal and a time interval during which said transmitted signal has occurred;

using said selected secondary node to receive said transmitted signal;

causing said selected secondary node to transmit back to said first node a power correction message indicative of a needed change in a power level of said transmitted signal, an indication of when said transmitted signal was received in time, and a time stamp indicating a time that said power correction message was transmitted; and

using said power correction message and said indication of when said transmitted signal was received to determine which one of said transmitted signals said power correction message corresponds to, and a degree of power level adjustment needed to be applied to said corresponding transmitted signal, in real time, to maintain a minimum predetermined received signal strength for a subsequently transmitted signal to said selected secondary node.

2. The method of claim 1, wherein a plurality of transmitted signals are transmitted to said secondary communication nodes in accordance with a time division multiple access (TDMA) communications scheme.

3. The method of claim 1, wherein said data file is updated to reflect a time of receipt of said power correction message from said selected secondary node.

4. A method for controlling a transmit power of a signal transmitted from a first communication node to a plurality of secondary communication nodes communicating with said first node, in closed loop fashion, in accordance with a multiplexed communication scheme, said method comprising:

using said first node to transmit a signal to each one of a plurality of secondary nodes in accordance with said multiplexed communication scheme;

maintaining a buffer having a data file of each transmission to each of said secondary nodes, said data file including a power level of said signal transmitted to each of said secondary nodes;

using each of said secondary nodes to receive its associated said signal from said first node;

causing each one of said secondary nodes to transmit back to said first node, a power level correction message indicative of a needed correction in a power level of a subsequent transmission from said first node;

causing said first node to adjust a power level of a subsequently transmitted signal to any one of said secondary nodes whenever said power correction message received from one of said secondary nodes indicates that said power level in said data file associated with a given said secondary node needs to be adjusted to maintain a signal strength of said signal received by said given secondary node within a predetermined signal strength range; and

updating said data file associated with said given secondary node to reflect the most recent power level of said signal transmitted to said given secondary node.

5. The method of claim 4, wherein said method further comprises:

maintaining a time of transmission with each said data file, said time of transmission indicating the time at which the most recent said transmission was sent to each of said secondary nodes.

6. The method of claim 4, wherein said method further comprises:

maintaining a start time of each said transmission and an end time of each said transmission in each said data file.

7. The method of claim 4, wherein said multiplexed communication scheme comprises a time division multiple access (TDMA) scheme;

and

wherein each of said secondary nodes are assigned a specific time slot by said first node, in accordance with said TDMA scheme.

8. A method for controlling a transmit power of a signal transmitted from a first communication node to a plurality of secondary communication nodes communicating with said first node, in closed loop fashion, in accordance with a multiplexed communication scheme, said method comprising:

using said first node to transmit a signal to each one of said secondary nodes;

creating a plurality of data files, each said data file being associated with one of said secondary nodes, each said data file including a time interval and a power level for each said transmission to its associated said secondary node;

using said secondary nodes to receive said transmitted signals;

causing each said secondary node to transmit back to said first node a power correction message indicative of a needed change in a power level of a signal transmitted from said first node, and an indication of when said transmitted signal was received in time; and

using said power correction messages received from said secondary nodes to adjust said power levels contained in said data files for each of said selected nodes to maintain a received signal strength of said signals received by said secondary nodes within predetermined desired ranges; and

updating said data files to reflect a most recent power level and time of transmission for each said transmitted signal to each said secondary node.

9. The method of claim 8, wherein each said secondary node applies a time stamp to said signals transmitted therefrom to apprise said first node of a time that a given one of said transmitted signals from said first node was received.

10. The method of claim 8, wherein said communications scheme comprises a time division multiple access (TDMA) scheme.

11. The method of claim 10, wherein each said secondary node is assigned a time slot during which it communicates with said first node.

12. A method of controlling a transmit power of a signal transmitted from a first communication node to a plurality of secondary communication nodes communicating with said first node, in closed loop fashion, said method comprising:

using said secondary nodes to receive signals transmitted by said first node;

causing each said secondary node to transmit back to said first node a power correction message indicative of a needed change in a power level of a subsequent transmission to be made from said first node;

maintaining data files of transmissions from said first node to each of said secondary nodes, said data files including a power level of each said transmission and a time interval during which each said transmission is made;

using said power correction message and said time interval to determine which one said transmitted signals said power correction message corresponds to;

matching said power correction messages from each of said secondary nodes to specific ones of each of said previously transmitted signals from said first node compiled in said data files; and

using power level information stored in said data files to modify subsequent transmissions to said secondary nodes based on said power correction messages received by said first node from each said secondary node to adjust a power level of each of said subsequent transmission to maintain said subsequent transmissions within predetermined power ranges.

13. The method of claim 12, wherein each said record comprises a time interval associated with each said transmission to a given one of said secondary nodes.

14. The method of claim 12, wherein each said record comprises a power level of at least a last one of said transmissions from said first node to a given one of said secondary nodes.