Method and apparatus for bi-directional power control in a digital communication system

• US 5,768,684 A
• Filed: 08/26/1996
• Issued: 06/16/1998
• Est. Priority Date: 03/04/1994
• Status: Expired due to Term

• Current Assignee: CDC Propriete Intellectuelle
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Attwood, Stanley William, Arens, John William, Grubb, Jerrold Lee
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): TO, DORIS HA
• Application Number:
  US08/702,851
• Time in Patent Office: 659 Days
• Field of Search: 455/69, 455/33.1, 455/70, 455/13.4, 455/13.1, 455/53.1, 455/54.1, 455/54.2, 455/56.1, 455/67.1, 455/427, 455/430, 455/517, 455/522, 455/524, 455/507, 455/12.1 , 455/504, 342/352, 342/354, 370/310, 370/318, 370/321, 370/316, 370/347, 370/337
• US Class Current: 455/13.4
• CPC Class Codes: H04B 7/18543 for adaptation of transmission parameters, e.g. power control for detecting or preventing errors in the information received H04L1/00
• CPC Class Codes: H04W 52/20 using error rate

Abstract

In a method and apparatus for maintaining a minimum transmission power level between two communication stations, each station measures the other'"'"'s received signal quality, and returns an indication of signal quality as part of a regular maintenance burst. Each station adjusts its own transmission power level based on the returned signal quality indication. The signal quality indication is based on the received ratio of bit energy to total noise power spectral density which is calculated from an estimated bit-error-rate.

Claims

1. A method of operating a satellite communication node in non-geostationary orbit, said node communicating with mobile units using data packets, each data packet having a payload portion containing digital voice data and digital control data, the method comprising the steps of:

communicating digital voice data within said data packets with said mobile unit over a traffic channel that has a continually changing propagation distance, said digital voice data being communicated in said payload portion of said data packets;

receiving from said mobile unit on said traffic channel at said satellite node, a link-quality indicator (LOI) that represents the quality of said voice data received by said mobile unit on said traffic channel, the LOI being received in said control data portion of said payload portion of said data packets;

adjusting at said node based on said LOI, a transmission power level for subsequent communications on said traffic channel;

repeating the receiving and adjusting steps regularly during the performance of the communicating step to compensate for changes in propagation characteristics as said propagation distance between said satellite node and said mobile unit changes

sending from said satellite node to said mobile unit on said traffic channel, a second LOI representing a quality level of communications received from said mobile unit, said second LOI being sent in said control data portions of said data packets; and

receiving, during the communicating step, digital voice data from said mobile unit on said traffic channel, said voice data having been transmitted by said mobile unit at a power level responsive to said second LOI, said digital voice data being received in said payload portion of said data packets.

wherein some of said data packets have digitized voice data being communicated between the mobile unit and the satellite communication node are devoid of link quality information, and

wherein the repeating of the receiving and adjusting steps regularly, said LQI is included on a regular basis within other data packets that include said digitized voice data.

2. A method as claimed in claim 1 further comprising the step of said satellite node generating said second LQI based on a ratio of received energy per bit to total noise power spectral density of said communications received from said mobile unit over said traffic channel during the communicating step, and wherein said receiving said LQI step comprises the step of receiving said LQI within said data packets, said LQI generated by said mobile unit based on received energy per bit to total noise power spectral density of communications received at said mobile unit over said traffic channel.

3. A method as claimed in claim 2 wherein said satellite communication node provides a plurality of antenna beams on earth'"'"'s surface, said antenna beams having non-interfering traffic channels in adjacent of said antenna beams,

said method further comprising the steps of:

communicating digitized voice data within said data packets with a plurality of mobile units over assigned traffic channels that have continually changing propagation distances, some of said mobile units of said plurality being located in different of said antenna beams;

receiving on said traffic channels within data packets from each mobile unit of said plurality, a LQI representing the quality of said voice data received by each mobile unit on the assigned traffic channel;

individually adjusting transmission power levels of each traffic channel based on the associated LQI; and

repeating the receiving and individually adjusting steps during the performance of the communicating with said plurality step as said propagation distances between said satellite communication node and each of said subscriber units change.

4. A method as claimed in claim 3 further comprising the steps of:

generating, by said satellite node an individual LQI for each mobile unit of said plurality, each individual LQI based on the quality of communications received from said each mobile unit;

sending within data packets, said individual LQI to said mobile unit associated therewith on said assigned traffic channel; and

receiving subsequent communications from each of said mobile units, said subsequent communications having been transmitted at a power level responsive to said individual LQI.

5. A method as claimed in claim 4 wherein each of said assigned traffic channels comprise time-slots of a frequency channel that is time division multiplexed and frequency division multiplexed, some of said assigned traffic channels being different time slots on a same frequency channel, and

wherein the individually adjusting step further comprises individually adjusting transmission power levels during assigned time slots of said same frequency channel.

6. A method of operating a node in a communication system adapted for controlling transmission power levels for communication with a mobile unit, said method comprising the steps of:

sending over a communication link at a transmission power level, a communication from said node to said mobile unit;

receiving at said node from said mobile unit, a link-quality indicator (LQI) representing the quality of said communication;

adjusting at said node based on said LQI, said transmission power level of said communication link;

receiving from said mobile unit, a second communication on a second communication link;

said communication system generating a second LQI for said second communication link based on a quality level of said second communication; and

sending said second LQI to said mobile unit, said mobile unit responsive to said second LQI,

wherein said mobile unit transmits digital data over said communication second link, and said generating step comprises the step of generating by said node said second LQI based on a ratio of a received energy per bit to total noise power spectral density of said second communication, said total noise power spectral density including interference noise power,

wherein said generating step further comprising the step of determining said ratio from a bit-error-rate received at said node, and said adjusting step comprises the step of increasing said mobile unit transmission power level when said bit-error-rate exceeds a predetermined value, and

wherein said bit-error-rate is estimated by sampling an instantaneous level of I and Q demodulator output signals when said I output signal is at a peak and said Q output signal is crossing zero.

7. A method of operating a subscriber unit adapted for communicating with a satellite communication node in non-geostationary orbit, said method comprising:

communicating digitized voice data within data packets with said satellite node over a traffic channel that has a continually changing propagation distance;

receiving, within said data packets containing said digitized voice data, on said traffic channel at said subscriber unit, a link-quality indicator (LOI) representing the quality of said voice data received by said satellite node during the communicating step, said LOI being calculated by said satellite communication node and based on a ratio of a received energy per bit to total noise power;

adjusting a transmission power level at said subscriber unit during subsequent performance of the communicating step based on said LOL;

repeating the receiving and adjusting steps regularly during the performance of the communicating step to compensate for changes in propagation characteristics as said propagating distance between said satellite node and said mobile unit changes;

communicating over said traffic channel, data packets containing digitized voice data, some of said data packets being devoid of link quality information;

on a regular basis, including said LQI within said data packets, the including step being part of a regularly performed link maintenance burst;

sending from said subscriber unit to said satellite communication node on said traffic channel, a second LQI within data packets containing digitized voice data, said second LQI based on a second ratio of a received energy per bit to total noise power for communications received at said subscriber unit; and

receiving, during the communicating step, voice data within data packets from said satellite communication node on said traffic channel, said voice data having been transmitted by said satellite communication node at a power level responsive to said second LQI,

wherein the sending step is performed on a regular basis as said propagation distance between said subscriber unit and said satellite communication node changes.

8. A method of operating a satellite communication node adapted for controlling transmission power levels for communication with a mobile unit, said method comprising the steps of:

sending over a communication link at a transmission power level, a communication from said node to said mobile unit;

receiving at said satellite communication node from said mobile unit, a link-quality indicator (LQI) representing the quality of said communication, the receiving step being performed by a receiver;

adjusting at said node based on said LQI, said transmission power level of said communication link;

receiving from said mobile unit, a second communication on a second communication link;

said communication system generating a second LQI for said second communication link based on a signal quality of said second communication, said signal quality including a ratio of a received energy per bit to total noise power spectral density, said ratio determined at least in part from a bit-error-rate of said second communication, said bit-error-rate being estimated by sampling an instantaneous level of I and Q demodulator output signals in said receiver when said I output signal is at a peak and said Q output signal is crossing zero; and

sending said second LQI to said mobile unit, said mobile unit responsive to said second LQI,

wherein said adjusting step comprises the step of increasing said of said first communication link when said bit-error-rate exceeds a predetermined value.