Orthogonal frequency division multiplex modem circuit

• US 20060209673A1
• Filed: 05/25/2006
• Published: 09/21/2006
• Est. Priority Date: 06/14/2000
• Status: Active Grant

• Current Assignee: Lenovo Innovations Ltd Hong Kong (Lenovo Group Ltd.)
• Original Assignee: NEC Corporation
• Inventors: Ichihara, Masaki, Furuya, Yukitsuna
• Granted Patent: US 7,843,803 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04L 27/183 Multiresolution systems
• CPC Class Codes: H04L 27/2604 Multiresolution systems by means of multiresolution subcarriers H04L27/183, H04L27/3488
• CPC Class Codes: H04L 27/3488 Multiresolution systems
• 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 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/0064 Rate requirement of the data, e.g. scalable bandwidth, data priority
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26

Abstract

To provide an orthogonal frequency division multiplex modem circuit which can multiplex signals, whose bit rates and QoS are different from one another, and can transmit the signals via one OFDM line. A serial/parallel converter converts input signals into a complex parallel signal respectively, and a sub carrier and a modulation system are assigned every communication channel. A randomizer changes the alignment sequence of the signal, a discrete inverse Fourier transformer processes the signal, a parallel/serial converter converts the signal into a serial signal, and a transmitter performs the orthogonal modulation of the signal to output the signal from an antenna. A receiver performs orthogonal demodulation of the signal received with an antenna, a serial/parallel converter converts the signal into a parallel signal, and a discrete Fourier transformer processes the parallel signal. In addition, a de-randomizer restores the alignment sequence of the subcarriers into the original condition, and a parallel/serial converter decodes and outputs the signal.

Claims

1. An orthogonal frequency division multiplex modem system which uses a plurality of subcarriers for communication and transmits and receives a plurality of communication channels, wherein one or more subcarriers are assigned to each of a plurality of communication channels, and a randomizer which randomly changes the order of the sequence of the alignment of subcarriers on a frequency axis is included in a transmission side, and a de-randomizer which restores the alignment of subcarriers to the order of sequence of the alignment before it is changed in the transmitting side is included in the receiving side.

2. The orthogonal frequency division multiplex modem system according to claim 1, wherein the number of subcarriers assigned to each of a plurality of the communication channels are adaptively changed.

3. The orthogonal frequency division multiplex modem system according to claim 1, wherein the number of the subcarriers assigned to each of a plurality of the communication channels are changed according to the QoS (Quality of Service).

4. The orthogonal frequency division multiplex modem system according to claim 3, wherein a modulation system applied to each group of subcarriers is changed according to the QoS which is necessary for the corresponding communication channel.

5. The orthogonal frequency division multiplex modem system according to claim 4, wherein the changeable modulation system is at least any one of the phase modulation of BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), and QAM (Quadrature Amplitude Modulation), and a symbol point on a phase plane is changed according to the QoS.

6. The orthogonal frequency division multiplex modem system according to any one of claims 1-5, wherein the processing for randomizing positions of the respective subcarriers is updated every symbol.

7. The orthogonal frequency division multiplex modem system according to claim 2, wherein all subcarriers are assigned to a single channel according to necessity, and the communication on other channels are stopped during the assigning.

8. The orthogonal frequency division multiplex modem system according to claim 4, wherein the peak values of symbols are determined to keep the transmission power of each subcarrier constant regardless of the modulation system.

9. An transmission system of an orthogonal frequency division multiplex modem system which uses a plurality of subcarriers for communication and transmits and receives a plurality of communication channels, wherein one or more subcarriers are assigned to each of a plurality of the communication channels, and a randomizer which randomly changes the order of the sequence of the alignment of subcarriers on a frequency axis is included.

10. The transmission system according to claim 9, wherein the number of the subcarriers assigned to each of a plurality of the communication channels are adaptively changed.

11. The transmission system according to claim 9, wherein the number of the subcarriers assigned to each of a plurality of the communication channels are changed according to QoS (Quality of Service).

12. The transmission system according to claim 11, wherein a modulation system applied to each group of subcarriers is changed according to the QoS which is necessary for the corresponding communication channel.

13. The transmission system according to claim 12, wherein the changeable modulation system is at least any one of the phase modulation of BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), and QAM (Quadrature Amplitude Modulation), and a symbol point on a phase plane is changed according to the QoS.

14. The transmission system according to any one of claims 9-13, wherein the processing for randomizing positions of the respective subcarriers is updated every symbol.

15. The transmission system according to claim 10, wherein all subcarriers are assigned to a single channel according to necessity, and the communication on other channels are stopped during the assigning.

16. The transmission system according to claim 12, wherein the peak values of symbols are determined to keep the transmission power of each subcarrier constant regardless of the modulation system.

17. A receiving system of an orthogonal frequency division multiplex modem system which uses a plurality of subcarriers for communication and transmits and receives a plurality of communication channels, the receiving system comprising:

a receiver for receiving a signal from an orthogonal frequency division multiplex modulator transmitting a plural of communication channels;

a demodulator for demodulating the signal; and

a de-randomizer which restores the alignment of subcarriers to the other of sequence of the alignment before it is randomly changed in a transmitting side.

18. An orthogonal frequency division multiplex communication method that uses a plurality of subcarriers for communication and transmits and receives a plurality of communication channels, the communication method comprising the steps of:

assigning one or more subscarriers to each of a plurality of communication channels;

changing randomly, the order of the sequence of the alignment of subcarriers on a frequency axis;

restoring the alignment of subcarriers to the order of sequence of the alignment before it is changed.

19. The orthogonal frequency division multiplex communication method according claim 18, wherein the number of subcarriers assigned to each of a plurality of the communication channels are adaptively changed.

20. The orthogonal frequency division multiplex communication method according to claim 18, wherein the number of the subcarriers assigned to each of a plurality of the communication channels are changed according to the QoS (Quality of Service).

21. The orthogonal frequency division multiplex communication method according to claim 20, wherein the method further comprises the step of modulating each group of subcarriers, said modulation is changed according to the QoS which is necessary for the corresponding communication channel.

22. The orthogonal frequency division multiplex communication method according to claim 21, wherein the changeable modulation is at least any one of the phase modulation of BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), and QAM (Quadrature Amplitude Modulation), and a symbol point on a phase plane is changed according to the QoS.

23. The orthogonal frequency division multiplex communication method according to any one of claims 18-22, wherein the step of changing randomly the order of the sequence of the respective subcarriers is updated every symbol.

24. An orthogonal frequency division multiplex transmission method which uses a plurality of subcarriers for communication and transmits and receives a plurality of communication channels, the transmission method comprises the steps of:

assigning one or more subcarriers to each of a plurality of the communication channels;

changing randomly the order of the sequence of the alignment of subcarriers on a frequency axis.

25. The transmission system according to claim 24, wherein the number of the subcarriers assigned to each of a plurality of the communication channels are adaptively changed.

26. The transmission system according to claim 24, wherein the number of the subcarriers assigned to each of a plurality of the communication channels are changed according to QoS (Quality of Service).

27. The transmission system according to claim 26, wherein the method further comprises the step of modulating each group of subcarriers, said modulation is changed according to the QoS which is necessary for the corresponding communication channel

28. The transmission system according to claim 27, wherein the changeable modulation is at least any one of the phase modulation of BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), and QAM (Quadrature Amplitude Modulation), and a symbol point on a phase plane is changed according to the QoS.

29. The transmission system according to anyone of claims 24-28, wherein the step of changing ramdomly the order of the sequence of the respective subcarriers is updated every symbol.

30. An orthogonal frequency division multiplex receiving method which uses a plurality of subcarriers for communication and transmits and receives a plurality of communication channels, the receiving method comprising the steps of:

receiving a signal from an orthogonal frequency division multiplex modulator transmitting a plural of communication channels;

demodulating the signal; and

restoring the alignment of subcarriers to the other of sequence of the alignment before it is randomly changed in a transmitting side.