Transmitters and receiver of spectrum spread communication system, and modulation and demodulation methods thereof

• US 20040109419A1
• Filed: 04/24/2003
• Published: 06/10/2004
• Est. Priority Date: 10/24/2000
• Status: Active Grant

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Kubo, Hiroshi, Sano, Hiroyasu
• Granted Patent: US 7,272,162 B2
• Time in Patent Office: Days
• US Class Current: 370/320
• CPC Class Codes: H04B 1/7136 Arrangements for generation of hop frequencies, e.g. using a bank of frequency sources, using continuous tuning or using a transform
• CPC Class Codes: H04B 1/7143 Arrangements for generation of hop patterns
• CPC Class Codes: H04B 1/7156 Arrangements for sequence synchronisation
• CPC Class Codes: H04B 2001/71367 using a transform
• CPC Class Codes: H04B 2001/71563 Acquisition
• CPC Class Codes: H04L 27/2634 Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation
• CPC Class Codes: H04L 5/026 using code division

Abstract

Data hopping means is provided with a hopping generation unit 21 and a data selection unit 23, the hopping pattern generation unit 21 generating a predetermined hopping pattern, and the data selection unit 23 outputting a plurality of subcarrier transmission signals corresponding to respective subcarriers, by receiving transmission data and outputting only the data carried in the subcarrier designated by the hopping pattern as the subcarrier transmission signal, while maintaining the other subcarrier transmission signals at a zero output level. Inverse Fourier transform means subjects the entirety of subcarrier reception signals output from the data selection unit 23 to inverse Fourier transform and outputs frequency-hopped spread-spectrum transmission signals.

Claims

1. A transmitter for a spread-spectrum communication system in which transmission data is subject to spectrum spreading using a predetermined number of subcarriers, comprising:

frame generation means constructing a frame by inserting a predetermined pilot sequence in the transmission data;

data hopping means comprising;

1) a hopping pattern generating unit generating a hopping pattern switched at a predetermined hopping frequency, the hopping pattern designating a subcarrier for frequency hopping; and

2) a data selection unit outputting a plurality of subcarrier transmission signals corresponding to the plurality of subcarriers, respectively, by receiving the transmission data and outputting as a subcarrier transmission signal only the transmission data carried in a subcarrier designated by the hopping pattern, while maintaining the other subcarrier transmission signals at a zero output level,

said transmitter further comprising;

inverse Fourier transform means subjecting the entirety of subcarrier transmission signals output from said data selection unit to inverse Fourier transform so as to output frequency-hopped spread-spectrum transmission signals.

2. The transmitter for a spread-spectrum communication system according to claim 1, wherein said data hopping means further comprises:

a pseudo random sequence generator provided with a plurality of shift registers and barrel-shifting values held in the shift registers at the predetermined hopping rate;

a plurality of multipliers each assigning a predetermined weight to each of the values held in the shift registers; and

an adder calculating a sum of outputs from said multipliers so as to output a hopping pattern of a predetermined sequence length.

3. A transmitter for a spread-spectrum communication system comprising:

modulation control means determining the number of subchannels for the multiplexing of transmission data and the number of subcarriers for frequency-hopping in each of the subchannels;

serial-to-parallel converting means splitting the transmission data into subchannel transmission data for as many subchannels as determined by said modulation control means;

a plurality of subchannel modulation processing means each receiving the corresponding subchannel transmission data for independent modulation processing so as to output a plurality of subcarrier transmission signals, each of said subchannel modulation processing means comprising;

1) frame generation means constructing a frame by inserting a predetermined pilot sequence in the subchannel transmission data;

2) data modulation means subjecting the subchannel transmission data of a frame structure to a predetermined data modulation process so as to output a modulated signal;

3) time-spreading means subjecting the modulated signal to a time-spreading process by multiplying the modulated signal by a predetermined time-spreading code;

4) data hopping means outputting a plurality of subcarrier transmission signals corresponding to the respective subcarriers, by receiving the modulated signal subjected to the time-spreading process, generating a predetermined hopping pattern, and outputting as the subcarrier transmission signal only the modulated signal carried in a subcarrier designated by the hopping pattern, while maintaining the other subcarrier transmission signals at a zero output level,

said transmitter further comprising;

inverse Fourier transform means subjecting the entirety of subcarrier transmission signals output from said data hopping means of said plurality of subchannel modulation processing means to inverse Fourier transform so as to output transmission signals multiplexed using said plurality of subchannels in which frequency-hopping spectrum-spreading is effected.

4. The transmitter for a spread-spectrum communication system according to claim 3, wherein said subchannel modulation processing means comprising:

1) frame generation means constructing a frame by inserting a predetermined pilot sequence in the subchannel transmission data;

2) data modulation means subjecting the subchannel transmission data of a frame structure to a predetermined data modulation process so as to output a modulated signal;

3) data hopping means outputting a plurality of subcarrier transmission signals corresponding to the respective subcarriers, by receiving the modulated signal, generating a predetermined hopping pattern, and outputting as the subcarrier transmission signal only the modulated signal carried in a subcarrier designated by the hopping pattern, while maintaining the other subcarrier transmission signals at a zero output level, said transmitter further comprising;

guard interval (GI) inserting means inserting

a predetermine guard interval to the transmission signal output from said inverse Fourier transform means.

5. The transmitter for a spread-spectrum communication system according to claim 3, wherein said data hopping means comprises:

a pseudo random sequence generator provided with a plurality of shift registers and barrel-shifting values held in the shift registers at the predetermined hopping rate;

a plurality of multipliers each assigning a predetermined weight to each of the values held in the shift registers; and

an adder calculating a sum of outputs from said multipliers so as to output a hopping pattern of a predetermined sequence length.

6. The transmitter for a spread-spectrum communication system according to claim 3, wherein said modulation control means determines subcarrier assignment such that the subcarriers for frequency hopping are spaced apart at predetermined frequency intervals,

said transmitter further comprising:

subcarrier assignment means receiving a plurality of subcarrier transmission signals output from each of said subchannel modulation processing means, rearranging the entire subcarrier transmission signals in accordance with the subcarrier assignment, and outputting the rearranged subcarrier transmission signals to said inverse Fourier transform means.

7. The transmitter for a spread-spectrum communication system according to claim 3, further comprising:

convolution coding means subjecting the transmission data to convolution coding for error correction; and

an interleaver subjecting the transmission data subjected to error correction to a predetermined interleaving process, wherein

the transmission data subjected to the interleaving process is output to said serial-to-parallel converting means.

18. The transmitter for a spread-spectrum communication system according to claim 3, further comprising:

communication quality monitoring means receiving information related to the quality of communication from a receiver with which said transmitter is communicating and determining the quality of communication based on the information,

wherein

said modulation control means modifies a subcarrier assignment defined by the number of subchannels for multiplexing and the number of subcarriers per subchannel, in accordance with a result of determination on the quality of communication.

8. A receiver for a spread-spectrum communication system comprising:

Fourier transform means subjecting a spread-spectrum received signal frequency-hopped to a predetermined number of subcarriers to a Fourier transform process and outputting a predetermined number of subcarrier reception signals;

hopping reception means comprising;

1) a slot synchronization unit detecting a known pilot sequence included in the subcarrier reception signal so as to establish synchronization between a transmitter with which said receiver is communicating;

2) a hopping pattern generating unit generating a hopping pattern switched at a predetermined hopping frequency, the hopping pattern designating a subcarrier for frequency hopping; and

3) a hopping data selection unit receiving the plurality of subcarrier reception signals, selecting only the subcarrier reception signal designated by the hopping pattern and outputting the selected signal as reception data.

9. The receiver for a spread-spectrum communication system according to claim 8, wherein said hopping data reception means further comprises:

a pseudo random sequence generator provided with a plurality of shift registers and barrel-shifting values held in the shift registers at the predetermined hopping rate;

a plurality of multipliers each assigning a predetermined weight to each of the values held in the shift registers; and

an adder calculating a sum of outputs from said multipliers so as to output a hopping pattern of a predetermined sequence length.

10. A receiver for a spread-spectrum communication system comprising:

Fourier transform means subjecting reception signals multiplexed using said plurality of subchannels in which frequency-hopping spectrum-spreading is effected so as to output a plurality of subcarrier reception signals;

a plurality of subchannel demodulation processing means receiving for demodulation the plurality of subcarrier reception signals belonging to a corresponding subchannel and outputting subchannel reception data in the corresponding subchannel, each of said plurality of subchannel demodulation processing means comprising;

1) hopping data reception means detecting a known pilot sequence included in the subcarrier reception signal so as to establish synchronization with a transmitter with which said receiver is communicating, generating a predetermined hopping pattern and selecting only the subcarrier reception signal designated by the hopping pattern and outputting the selected signal as the reception data;

2) time-despreading means subjecting the subchannel reception data to time despreading by multiplying the subchannel reception data by a predetermined time-spreading code;

3) RAKE combination means effecting channel estimation using the pilot sequence included in the subchannel reception data subjected to time despreading, subjecting the subchannel reception data subjected to time despreading to RAKE combination and outputting the resultant subchannel reception data, said receiver further comprising;

serial-to-parallel converting means receiving the subchannel reception data subjected to RAKE combination output from each of said subchannel demodulation processing means, combining a plurality of sets of the subchannel reception data and outputting the combined reception data.

11. The receiver for a spread-spectrum communication system according to claim 10, wherein each of said subchannel demodulation processing means further comprises:

interference level estimation means performing a predetermined calculation process based on the pilot sequence included in the subchannel reception data subjected to time despreading so as to determine a power of interference affecting the subchannel reception data; and

normalizing means normalizing the subchannel reception data subjected to RAKE combination with the power of interference,

wherein

the subchannel reception data subjected to normalization is output to said parallel-to-serial converting means.

12. The receiver for a spread-spectrum communication system according to claim 10, further comprising:

guard interval elimination unit removing a predetermined guard interval inserted in the reception signal,

each of said subchannel demodulation processing means further comprising;

1) hopping data reception means receiving a plurality of subcarrier reception signals for the corresponding subchannel, detecting the pilot sequence included in the subcarrier reception signals so as to establish synchronization with the transmitter with which said receiver is communicating, generating a predetermined hopping pattern, selecting only the subcarrier reception signal designated by the hopping pattern and outputting the selected subcarrier signal as subchannel reception data; and

2) synchronous detection means performing channel estimation based on the pilot sequence included in the subchannel reception data, subjecting the subchannel reception data to synchronous detection and outputting the subchannel reception data subjected to synchronous detection.

13. The receiver for a spread-spectrum communication system according to claim 12, wherein said each of said subchannel demodulation processing means further comprising:

interference level estimation means performing a predetermined calculation process based on the pilot sequence included in the subchannel reception data subjected to synchronous detection so as to determine a power of interference affecting the subchannel reception data; and

normalizing means normalizing the subchannel reception data subjected to synchronous detection with the power of interference,

wherein

the subchannel reception data subjected to normalization is output to said parallel-to-serial converting means.

14. The transmitter for a spread spectrum communication system according to claim 12, wherein said synchronous detection means comprises:

1) a channel estimation unit performing channel estimation based on the pilot sequence included in the subchannel reception data;

2) a complex conjugate calculating unit calculating a complex conjugate of the subchannel reception data based on a result of estimation by said channel estimation unit;

3) weight assigning unit assigning a weight to the subchannel reception data by multiplying the subchannel reception data by the complex conjugate and outputting the weighted subchannel reception data.

15. The receiver for a spread-spectrum communication system according to claim 10, wherein said hopping data reception means comprises:

a pseudo random sequence generator provided with a plurality of shift registers and barrel-shifting values held in the shift registers at the predetermined hopping rate;

a plurality of multipliers each assigning a predetermined weight to each of the values held in the shift registers; and

an adder calculating a sum of outputs from said multipliers so as to output a hopping pattern of a predetermined sequence length.

16. The receiver for a spread-spectrum communication system according to claim 10, further comprising:

subcarrier reception signal distribution means receiving a plurality of subcarrier reception signals from said Fourier transform means and outputting the subcarrier reception signals to the corresponding subchannel demodulation processing means in accordance with a predetermined subcarrier assignment.

17. The receiver for a spread-spectrum communication system according to claim 10, further comprising:

a deinterleaver rearranging the order of the reception data output from said parallel-to-serial converting means in accordance with a predetermined scheme; and

error correcting means for subjecting the rearranged reception data to error correction so as to output user data.

19. The receiver for a spread-spectrum communication system according to claim 10, further comprising:

communication quality reporting means reporting information related to the quality of communication to the transmitter with which said receiver is communicating.

20. A spread-spectrum modulation and demodulation method in which transmission data is subject to spectrum spreading using a predetermined number of subcarriers, comprising the steps of:

generating a hopping pattern switched at a predetermined hopping frequency, the hopping pattern designating a subcarrier for frequency hopping;

outputting a plurality of subcarrier transmission signals corresponding to the plurality of subcarriers, respectively, by receiving the transmission data and outputting as a subcarrier transmission signal only the transmission data carried in a subcarrier designated by the hopping pattern, while maintaining the other subcarrier transmission signals at a zero output level; and

subjecting the entirety of subcarrier transmission signals to inverse Fourier transform so as to output frequency-hopped spread-spectrum transmission signals.

21. A spread-spectrum modulation and demodulation method comprising the steps of:

subjecting a spread-spectrum received signal frequency-hopped to a predetermined number of subcarriers to a Fourier transform process and outputting a predetermined number of subcarrier reception signals;

generating a hopping pattern switched at a predetermined hopping frequency, the hopping pattern designating a subcarrier for frequency hopping; and

receiving the plurality of subcarrier reception signals, selecting only the subcarrier reception signal designated by the hopping pattern and outputting the selected signal as reception data.