Multi-subband frequency hopping communication system and method

• US 20050249266A1
• Filed: 05/03/2005
• Published: 11/10/2005
• Est. Priority Date: 05/04/2004
• Status: Abandoned Application

• Current Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Original Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Inventors: Brown, Colin, Vigneron, Philip
• Application Number:
  US11/119,780
• Publication Number:
  US 20050249266A1
• Time in Patent Office: Days
• US Class Current: 375/133
• CPC Class Codes: H04B 1/713 using frequency hopping
• CPC Class Codes: H04K 3/224 with countermeasures at transmission and/or reception of the jammed signal, e.g. stopping operation of transmitter or receiver, nulling or enhancing transmitted power in direction of or at frequency of jammer
• CPC Class Codes: H04K 3/25 based on characteristics of target signal or of transmission as countermeasure against surveillance H04K3/827, e.g. using direct sequence spread spectrum or fast frequency hopping spread spectrum techniques H04B1/69
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems

Abstract

The invention provides an adaptive frequency hopping spread-spectrum (FHSS) transmission system and method, which efficiently utilizes available transmission bandwidth, whilst providing robustness to jamming techniques in wireless communication systems. The proposed technique operates by transmitting a wide-band signal over multiple, single-carrier, parallel transmission subbands, which may occupy non-contiguous frequency regions. The proposed scheme exhibits significant gain in error rate performance, as compared to a data rate equivalent single-subband system in the presence of signal jamming and/or interference without a reduction in the transmission data rate nor an increase in transmitter power. In addition, the proposed system and method are adaptive and enable more efficient use of the available bandwidth for communicating, thus increasing the overall bandwidth utilization of the system.

Claims

1. ) A method of transmitting an input data stream via a radio link, the input data stream having an input data rate, the method comprising the steps of:

a) converting the input data stream into a plurality of parallel data sub-streams using serial-to-parallel conversion, wherein each of the parallel data sub-streams carries a different portion of the input data stream, each portion defining a sub-stream data rate;

b) generating a carrier waveform having a hopping frequency for each parallel data sub-stream;

c) modulating each carrier waveform using the respective data sub-stream according to a modulation format to produce a frequency-hopping subband signal, said sub-band signal having a subband bandwidth related to the corresponding sub-stream data rate; and

,

d) forming a multi-subband frequency-hopping RF signal from the frequency-hopping subband signals for transmitting thereof via the radio link using an RF transmitting unit;

wherein each of the frequency-hopping subband signals has a different frequency hopping sequence and a frequency hopping range, the frequency hopping ranges being such that at least two of the frequency hopping ranges have at least one common frequency.

2. ) A method according to claim 1, wherein the frequency hopping sequences form a plurality of pseudo-random orthogonal hopping sequences.

3. ) A method according to claim 2, wherein step (a) comprises the step of encoding the input data stream using one of:

forward error correction coding, cyclic redundancy check coding, and data symbol interleaving.

4. ) A method according to claim 2, wherein each data sub-stream comprises a plurality of symbols, each symbol having a size, and,

wherein each of the sub-stream of symbols is formed from a different portion of the input stream of data.

5. ) A method according to claim 2, further comprising adding a pilot sequence of symbols to at least one of the data sub-streams.

6. ) A method according to claim 4, wherein at least one selected from the group consisting of:

a number of the data sub-streams,

the frequency hopping range of at least one of the data sub-streams,

the sub-stream data rate of at least one of the data sub-streams,

the symbol size for symbols in at least one of the data sub-streams, and

the modulation format for at least one of the data sub-streams, is adjustable in dependence to one of;

the input data rate, frequency bands available for the RF transmission, and external signal interference in the radio link.

7. ) A method according to claim 1, wherein at least two of the parallel data sub-streams from the Q parallel data sub-streams have substantially a same frequency-hopping range.

8. ) A method according to claim 1 wherein at least one of the frequency-hopping ranges is non-contiguous.

9. ) A method according to claim 1 wherein there are 2 to 8 parallel data sub-streams.

10. ) A method of receiving a stream of data transmitted by a transmitter using the method of claim 1, the method of receiving comprising the steps of:

A) receiving the multi-subband frequency-hopping RF signal with an RF receiving unit, the multi-subband frequency-hopping RF signal comprising the plurality of frequency-hopping subband signals, each centered at a different hopping frequency known to the receiver;

B) converting the multi-subband frequency-hopping RF signal into a plurality of baseband signals corresponding to the plurality of frequency-hopping subband signals;

C) extracting a plurality of parallel sub-streams of received data symbols from the plurality of baseband signals, wherein each of the parallel sub-streams is extracted from a baseband signal corresponding to a different frequency-hopping subband signal; and

,

D) combining the extracted plurality of parallel sub-streams of received data symbols into a sequential stream of data symbols using a parallel-to-serial conversion.

11. ) A method according to claim 10, wherein step (C) includes producing a plurality of parallel sub-sequences of received data symbols by performing, for at least one of the baseband signals, the steps of:

sampling the at least one of the baseband signals to obtain a sequence of received waveform samples;

identifying a pilot sequence in the sequence of received waveform samples;

performing subband-level channel estimation using the identified pilot sequence; and

,

performing subband-level channel equalizing upon the sequence of received waveform samples to obtain one of the plurality of parallel sub-streams of received data symbols.

12. ) A method according to claim 10, wherein step (D) comprises the steps of:

combining the plurality of parallel sub-streams of the received data symbols into a combined sequence of data symbols using the parallel-to-serial conversion; and

,

de-coding the combined sequence of received data symbols to form the sequential stream of data symbols.

13. ) A method according to claim 10, further comprising the steps of:

estimating a transmission quality characteristic for each of the received frequency-hopping subband signals, and

forming a feedback signal for communicating to the transmitter for adaptively changing a characteristic of the multi-subband frequency-hopping RF signal at the transmitter.

14. ) A method according to claim 13, wherein the characteristic of the multi-subband frequency-hopping RF signal is one of:

a number of the frequency-hopping subband signals in the multi-subband frequency-hopping RF signal,

the frequency bandwidth of one of the frequency-hopping subband signals,

the frequency hopping range of one of the frequency-hopping subband signal,

the frequency hopping sequence of one of the frequency-hopping subband signal, and

the modulation format for one of the frequency-hopping subband signal.

15. ) A multi-subband frequency-hopping transmitter for transmitting an input stream of data, comprising:

input data conversion means for converting the input data stream into a plurality of parallel data sub-streams using serial-to-parallel conversion, each of the parallel data sub-streams carrying a different portion of the input data stream;

waveform generating means for generating a frequency-hopping carrier waveform for each of the parallel data sub-streams, each of the frequency-hopping carrier waveforms having a different hopping frequency;

modulating means for modulating each of the frequency-hopping carrier waveforms with a corresponding data sub-stream using a modulation format to produce the frequency-hopping subband signals;

an RF transmitting unit outputting the frequency-hopping subband signals for transmitting via a radio link to a receiver;

wherein each of the frequency-hopping carrier waveforms has a distinct frequency hopping sequence and a frequency hopping range, the frequency hopping ranges being such that at least two of the frequency hopping ranges have at least one common frequency.

16. ) A transmitter according to claim 15, further comprising means for inserting a pilot sequence of symbols in at least one of the plurality of parallel data sub-streams.

17. ) A transmitter according to claim 15, wherein the data conversion means comprises an encoder and a serial-to-parallel conversion unit.

18. ) A transmitter according to claim 15, capable of adaptively changing at least one selected from the group consisting of:

a number of subband signals;

the portion of the input data stream carried by one of the parallel data sub-streams, the portion defining a data rate of said data sub-stream;

the frequency-hopping range and the frequency-hopping sequence of one of the frequency-hopping subband signals; and

,

the modulation format of one of the frequency-hopping subband signals.

19. ) A multi-subband receiver for receiving a stream of data symbols transmitted using the transmitter of claim 15, comprising:

an RF receiving unit for receiving a multi-subband RF signal comprising a plurality of frequency-hopping subband signals and for converting each of the plurality of frequency-hopping subband signals into a baseband signal;

data extracting means for extracting a plurality of parallel sub-streams of received symbols from the plurality of baseband signals; and

,

output data conversion means for converting the plurality of parallel sub-streams of received symbols into a sequential stream of data symbols using a parallel-to-serial conversion.

20. ) A receiver according to claim 19, wherein the data extracting means comprises:

an A/D converter for obtaining a sequence of received waveform samples from each of the baseband signals by sampling thereof;

channel estimating means for identifying a pilot sequence in at least one of the sequences of received waveform samples, and for providing subband-level channel estimation based on the identified pilot sequence;

channel equalizing means for performing subband-level channel equalization upon each of the sequences of received waveform samples based on the subband-level channel estimation provided by the channel estimating means to form the plurality of parallel sub-streams of received symbols.

21. ) A receiver according to claim 19, wherein the output data conversion means comprises:

a parallel to serial converter for combining the plurality of parallel sub-streams of received symbols into the sequential stream of received data symbols; and

,

a decoder for de-coding the sequential stream of data symbols.