Adaptive modulation method

• US 6,452,964 B1
• Filed: 03/23/1999
• Issued: 09/17/2002
• Est. Priority Date: 06/05/1998
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Yoshida, Makoto
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Kim, Heechul
• Application Number:
  US09/274,783
• Time in Patent Office: 1,274 Days
• Field of Search: 375/262, 375/219, 375/142, 375/227, 375/222, 370/252, 370/347
• US Class Current: 375/222
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0021 in which the algorithm uses adaptive thresholds
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 27/38 Demodulator circuits; Receiver circuits

Abstract

In the present invention, a modulation level estimation unit calculates the square error of the minimum value of distances between each signal point received at a modulation level ML and the signal point of a received signal at each modulation level ML. A received power measurement unit measures the received power level of the received signal. A modulation level estimation unit calculates the value obtained by multiplying the square error calculated at each modulation level ML, by a weighted calculation from both a threshold power level for switching the modulation level ML and the received power level as a likelihood value at each modulation level ML. Then, the modulation level estimation unit estimates a modulation level ML corresponding to the maximum likelihood value of all the likelihood values at the modulation level ML as a modulation level ML of the received signal, without transmitting any codewords on the used modulation level.

Claims

1. A radio transmission method for flexibly controlling a modulation level according to conditions of transmission paths, comprising the steps of:

calculating a square error of a minimum value of distances between each signal point to be received at a modulation level and a signal point of a received signal for each modulation level;

measuring a received power level of a received signal;

calculating a value obtained by multiplying a square error calculated at each modulation level by a weighted calculation from both a threshold power level for switching a modulation level and a received power level as a likelihood value at each modulation level; and

estimating a modulation level corresponding to a maximum likelihood value of all the likelihood values at each modulation level.

2. A radio transmission method for flexibly controlling a modulation level according to conditions of transmission paths, comprising the steps of:

calculating a square error of a minimum value of distances between each signal point to be received at a modulation level and a signal point of a received signal for each modulation level;

measuring an average throughput of a received signal;

changing each threshold power level for switching each modulation level, based on the average throughput;

measuring a received power level of a received signal;

calculating a value obtained by multiplying a square error calculated at each modulation level by a weighted calculation from both a threshold power level for switching a modulation level and a received power level as a likelihood value at each modulation level; and

estimating a modulation level corresponding to a maximum likelihood value of all the likelihood values at each modulation level.

3. A radio transmission method for flexibly controlling a modulation level according to conditions of transmission paths, comprising the steps of:

calculating a square error of a minimum value of distances between each signal point to be received at a modulation level and a signal point of a received signal for each modulation level;

measuring a received power level of a received signal;

measuring an average throughput of a received signal;

calculating a value obtained by multiplying a square error calculated at each modulation level by a weighted calculation from both a threshold power level for switching a modulation level and a average throughput as a likelihood value at each modulation level; and

estimating a modulation level corresponding to a maximum likelihood value of all the likelihood values at each modulation level.

4. A radio transmission system for flexibly controlling a modulation level according to conditions of transmission paths, comprising:

a circuit for calculating a square error of a minimum value of distances between each signal point to be received at a modulation level and at a signal point of a received signal at each modulation level;

a circuit for measuring a received power level of a received signal;

a circuit for calculating a value obtained by multiplying a square error calculated at each modulation level by a weighted calculation from both a threshold power level for switching a modulation level and an average throughput as a likelihood value at each modulation level; and

a circuit for estimating a modulation level corresponding to a maximum likelihood value of all the likelihood values at each modulation level.

5. A radio transmission system for flexibly controlling a modulation level according to conditions of transmission paths, comprising:

a circuit for calculating a square error of a minimum value of distances between each signal point to be received at a modulation level and a signal point of a received signal for each modulation level;

a circuit for measuring an average throughput of a received signal;

a circuit for changing each threshold power level for switching a modulation level, based on an average throughput;

a circuit for measuring a received power level of a received signal;

a circuit for calculating a value obtained by multiplying a square error calculated at each modulation level by a weighted calculation from both a threshold power level for switching a modulation level and an average throughput as a likelihood value at each modulation level; and

a circuit for estimating a modulation level corresponding to a maximum likelihood value of all the likelihood values at each modulation level.

6. A radio transmission system for flexibly controlling a modulation level according to conditions of transmission paths, comprising:

a circuit for calculating a square error of a minimum value of distances between each signal point to be received at a modulation level and a signal point of a received signal for each modulation level;

a circuit for measuring a received power level of a received signal;

a circuit for reporting weighted functions corresponding to a reported average throughput;

a circuit for measuring an average throughput of a received signal;

a circuit for calculating a value obtained by multiplying a square error calculated at each modulation level by a weighted calculation from both a threshold power level for switching a modulation level and an average throughput as a likelihood value at each modulation level; and

a circuit for estimating a modulation level corresponding to a maximum likelihood value of all the likelihood values at each modulation level.