Apparatus and method for controlling adaptive modulation and coding in an orthogonal frequency division multiplexing communication system

• US 7,492,701 B2
• Filed: 11/18/2004
• Issued: 02/17/2009
• Est. Priority Date: 11/19/2003
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Song, Kee-Bong, Lee, Dong-Jun
• Primary Examiner(s): Backer; Firmin
• Assistant Examiner(s): NGUYEN, PHUONGCHAU BA
• Application Number:
  US10/992,164
• Publication Number:
  US 20050157639A1
• Time in Patent Office: 1,552 Days
• Field of Search: None
• US Class Current: 370/208
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04W 52/262 taking into account adaptive modulation and coding [AMC] scheme AMC per se H04L1/0001

Abstract

A method and apparatus for controlling AMC in an OFDM communication system in which an entire frequency band is divided into a plurality of sub-carrier bands. In the AMC controlling method, power and a number of transmission bits are calculated for each of the sub-carriers in a predetermined method for each of coding methods available in the OFDM communication system. A data rate for each of the coding methods is calculated based on the number of transmission bits and the power for each sub-carrier. A coding method having a highest of the calculated data rates is selected and a modulation method is determined according to a number of transmission bits in the determined coding method.

Claims

1. A method of controlling adaptive modulation and coding (AMC) in an orthogonal frequency division multiplexing (OFDM) communication system in which an entire frequency band is divided into a plurality of sub-carrier bands, comprising the steps of:

(1) calculating a power and a number of transmission bits for each of the sub-carriers in a predetermined method for each coding method available in the OFDM communication system;

(2) calculating a data rate for each coding method based on the number of transmission bits and the power for each sub-carrier;

(3) determining a coding method having a highest of the calculated data rates for the OFDM communication system; and

(4) determining a modulation method for the OFDM communication system according to a number of transmission bits in the determined coding method;

wherein the step of calculating the number of transmission bits and the power for each sub-carrier for each of the coding methods is performed by

$\underset{\underset{\underset{{\tilde{P}}_1,\mathrm{\dots <br><br>}<br><br>,{\tilde{P}}_N}{m_{1,}<br><br><br><br>\mathrm{\dots <br><br>}<br><br><br><br>m_N}}{i\in <br><br>\left\{1,\mathrm{\dots <br><br>}<br><br>,V\right\}}}{\max }<br><br><br><br>R=r<br><br>\left(C_i\right)<br><br><br><br>\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>m_n$

where i is an index of a coding method available in the OFDM communication system, R(C_i) is a coding rate of an ith coding method C_i, and m_n is a number of transmission bits for an nth sub-carrier P_n is transmit power of bits transmitted on the nth sub-carrier.

2. The method of claim 1, further comprising the steps of:

(5) applying a scaling factor to the calculated power for the determined coding method; and

(6) determining a resulting power as the power for each sub-carrier.

3. The method of claim 2, wherein the scaling factor is determined according to a number of bits included most in the transmission bits for each sub-carrier.

4. The method of claim 1, wherein the number of transmission bits and the power for each sub-carrier calculated by

$\underset{\underset{\underset{{\tilde{P}}_1,\mathrm{\dots <br><br>}<br><br>,{\tilde{P}}_N}{m_{1,}<br><br><br><br>\mathrm{\dots <br><br>}<br><br><br><br>m_N}}{i\in \; <li></li>\left\{1,\mathrm{\dots <br><br>}<br><br>,V\right\}}}{\max }<br><br><br><br>R=r<br><br>\left(C_i\right)<br><br><br><br>\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>m_n$

are limited by

$m_n\le <br><br>\min <br><br>\left\{{\log }_2\left(1+\frac{d_H<br><br>\left(C_i\right)<br><br><br><br>{<br><br>H_n<br><br>}^2<br><br>{\tilde{P}}_n}{\mathrm{\Gamma <br><br>}}\right),m_{\max }\right\}$

where d_H(C_i) is a minimum Hamming distance of bits coded in an ith coding method C_i, H_n is a fading coefficient of an nth sub-carrier, m_max is a maximum number of bits transmittable for each of the sub-carriers, and Γ

is a constant determined by a packet error rate,

$\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>{\tilde{P}}_n\le <br><br>P_T$

where P_T is a maximum transmit power available in the OFDM communication system.

5. The method of claim 1, wherein the modulation method is Gray mapping.

6. The method of claim 1, wherein the predetermined method is a Levin-Campello algorithm.

7. An apparatus for controlling adaptive modulation and coding (AMC) in an orthogonal frequency division multiplexing (OFDM) communication system in which an entire frequency band is divided into a plurality of sub-carrier bands, comprising:

an AMC controller for calculating a power and a number of transmission bits for each of the sub-carriers in a predetermined method for each coding method available in the OFDM communication system, calculating a data rate for each coding method based on the number of transmission bits and the power for each sub-carrier, determining a coding method having a highest of the calculated data rates for the OFDM communication system, and determining a modulation method for the OFDM communication system according to a number of transmission bits in the determined coding method;

an encoder for encoding input information data bits in the determined coding method; and

a modulator for modulating coded bits received from the encoder in the determined modulation method;

wherein the AMC controller calculates the number of transmission bits and the power for each sub-carrier for each of the coding methods by

$\underset{\underset{\underset{{\tilde{P}}_1,\mathrm{\cdots <br><br>}<br><br>,{\tilde{P}}_N<br><br>}{m_{1,}<br><br>\mathrm{\cdots <br><br>}<br><br><br><br>m_N<br><br>}}{i\in <br><br>\left\{1,\mathrm{\cdots <br><br>}<br><br>,V\right\}}}{\max }<br><br>R=r<br><br>\left(C_i\right)<br><br><br><br>\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>m_n$

where i is an index of a coding method available in the OFDM communication system, r(C_i) is a coding rate of an ith coding method C_i, and m_n is a number of transmission bits for an nth sub-carrier P_n is transmit power of bits transmitted on the nth subcarrier.

8. The apparatus of claim 7, further comprising a transmitter for performing an inverse fast Fourier transform (IFFT) on a modulated signal received from the modulator and RE (Radio Frequency)-processing the IFFT signal.

9. The apparatus of claim 8, wherein the AMC controller applies a scaling factor to the calculated power for the determined coding method and determines a resulting power as the power for each sub-carrier.

10. The apparatus of claim 9, wherein the AMC controller determines the scaling factor according to a number of bits included most in the transmission bits for each sub-carrier.

11. The apparatus of claim 7, wherein the AMC controller limits the number of transmission bits and the power for each sub-carrier calculated by

$\begin{array}{c}\underset{\underset{\underset{{\tilde{P}}_1,\mathrm{\cdots <br><br>}<br><br>,{\tilde{P}}_N<br><br>}{m_{1,}<br><br>\mathrm{\cdots <br><br>}<br><br><br><br>m_N<br><br>}}{i\in \; <li></li>\left\{1,\mathrm{\cdots <br><br>}<br><br>,V\right\}}}{\max }<br><br>R=r<br><br>\left(C_i\right)<br><br><br><br>\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>m_n\\ \mathrm{using}\\ m_n\le <br><br>\min <br><br>\left\{{\log }_2\left(1+\frac{d_H<br><br>\left(C_i\right)<br><br>{<br><br>H_n<br><br>}^2<br><br>{\tilde{P}}_n}{\mathrm{\Gamma <br><br>}}\right),m_{\max }\right\}\end{array}$

where d_H(C_i) is a minimum Hamming distance of bits coded in an ith coding method C_i, H_n is a fading coefficient of an nth sub-carrier, m_max is a maximum number of bits transmittable for each of the sub-carriers, and Γ

is a constant determined by a packet error rate,

$\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>{\tilde{P}}_n\le <br><br>P_T$

where P_T is a maximum transmit power available in the OFDM communication system.

12. The apparatus of claim 7, wherein the modulation method is Gray mapping.

13. The apparatus of claim 7, wherein the predetermined method is a Levin-Campello algorithm.