GMSK spread modulation

1. A method for transmitting a modulated signal comprising:

obtaining a sequence of data symbols;

obtaining a spread spectrum code comprising a sequence of spread spectrum chips;

generating a sequence of pre-modulation chips by combining the sequence of data symbols with the spread spectrum chips, wherein for each data symbol, at least one of the pre-modulation chips is generated by taking into account at least the data symbol and at least one of the spread spectrum chips;

performing Gaussian Minimum Shift Keying (GMSK) modulation using the sequence of pre-modulation chips to produce a spread spectrum GMSK signal;

transmitting the spread spectrum GMSK signal;

wherein the spread spectrum GMSK signal adopts antipodal signaling to represent each data symbol; and

wherein for each data symbol, if the data symbol takes on a first binary value, a corresponding portion of the spread spectrum GMSK signal exhibits a select waveform, and if the data symbol takes on a second binary value, the corresponding portion of the spread spectrum GMSK signal exhibits a phase-inverted version of the select waveform.

2. The method of claim 1 wherein the spread spectrum GMSK signal is capable of being approximated as a pulse amplitude modulation (PAM) signal.

3. The method of claim 2 wherein even ones and odd ones of the sequence of pre-modulation chips separately correspond to in-phase (I) and quadrature (Q) components of the PAM signal.

4. The method of claim 1 wherein the spread spectrum code is a pseudo-noise (PN) code.

5. The method of claim 1 wherein the GMSK modulation adopts a BT product within a range from 0.4 to 0.5.

6. A method for transmitting a modulated signal comprising:

obtaining a sequence of data symbols;

obtaining a spread spectrum code comprising a sequence of spread spectrum chips;

generating a sequence of pre-modulation chips by combining the sequence of data symbols with the spread spectrum chips, wherein for each data symbol, at least one of the pre-modulation chips is generated by taking into account at least the data symbol and at least one of the spread spectrum chips;

performing Gaussian Minimum Shift Keying (GMSK) modulation using the sequence of pre-modulation chips to produce a spread spectrum GMSK signal; and

transmitting the spread spectrum GMSK signal;

wherein each data symbol corresponds to K spread spectrum chips and K pre-modulation chips, wherein K is a positive integer;

wherein a leading one of the K pre-modulation symbols corresponding to a current data symbol is generated by taking into account

i. an immediately preceding data symbol;

ii. a final one of the K spread spectrum chips corresponding to the immediately preceding data symbol;

iii. the current data symbol; and

iv. a leading one of the K spread spectrum chips corresponding to the current data symbol; and

wherein remaining ones of the K pre-modulation symbols corresponding to the current data symbol are each generated by taking into account

i. an immediately preceding one of the K spread spectrum chips corresponding to the current data symbol; and

ii. a current one of the K spread spectrum chips corresponding to the current data symbol.

7. The method of claim 6 wherein even ones and odd ones of the remaining pre-modulation symbols corresponding to the current data symbol are generated using opposite signs.

8. An apparatus for transmitting a modulated signal comprising:

a data processing unit capable of receiving a sequence of data symbols and combining the sequence of data symbols with a spread spectrum code comprising a sequence of spread spectrum chips to produce a sequence of pre-modulation chips, wherein for each data symbol, at least one of the pre-modulation chips is generated by taking into account at least the data symbol and at least one of the spread spectrum chips;

a modulator coupled to the data processing unit and configured to perform Gaussian Minimum Shift Keying (GMSK) modulation on the sequence of pre-modulation chips to produce a spread spectrum GMSK signal;

wherein the spread spectrum GMSK signal adopts antipodal signaling to represent each data symbol; and

wherein for each data symbol, if the data symbol takes on a first binary value, a corresponding portion of the spread spectrum GMSK signal exhibits a select waveform, and if the data symbol takes on a second binary value, the corresponding portion of the spread spectrum GMSK signal exhibits a phase-inverted version of the select waveform.

9. The apparatus of claim 8 wherein the spread spectrum GMSK signal is capable of being approximated as a pulse amplitude modulation (PAM) signal.

10. The apparatus of claim 9 wherein even ones and odd ones of the sequence of pre-modulation chips separately correspond to in-phase (I) and quadrature (Q) components of the PAM signal.

11. The apparatus of claim 8 wherein the spread spectrum code is a pseudo-noise (PN) code.

12. The apparatus of claim 8 wherein the GMSK modulation adopts a BT product within a range from 0.4 to 0.5.

13. An apparatus for transmitting a modulated signal comprising:

a data processing unit capable of receiving a sequence of data symbols and combining the sequence of data symbols with a spread spectrum code comprising a sequence of spread spectrum chips to produce a sequence of pre-modulation chips, wherein for each data symbol, at least one of the pre-modulation chips is generated by taking into account at least the data symbol and at least one of the spread spectrum chips;

a modulator coupled to the data processing unit and configured to perform Gaussian Minimum Shift Keying (GMSK) modulation on the sequence of pre-modulation chips to produce a spread spectrum GMSK signal;

wherein each data symbol corresponds to K spread spectrum chips and K pre-modulation chips, wherein K is a positive integer;

wherein a leading one of the K pre-modulation chips corresponding to a current data symbol is generated by taking into account

i. an immediately preceding data symbol;

ii. a final one of the K spread spectrum chips corresponding to the immediately preceding data symbol;

iii. the current data symbol; and

iv. a leading one of the K spread spectrum chips corresponding to the current data symbol; and

wherein remaining ones of the K pre-modulation chips corresponding to the current data symbol are each generated by taking into account

i. an immediately preceding one of the K spread spectrum chips corresponding to the current data symbol; and

ii. a current one of the K spread spectrum chips corresponding to the current data symbol.

14. The apparatus of claim 13 wherein even ones and odd ones of the remaining pre-modulation chips corresponding to the current data symbol are generated using opposite signs.

15. A system for transmitting a modulated signal comprising:

means for obtaining a sequence of data symbols;

means for obtaining a spread spectrum code comprising a sequence of spread spectrum chips;

means for generating a sequence of pre-modulation chips by combining the sequence of data symbols with the spread spectrum chips, wherein for each data symbol, at least one of the pre-modulation chips is generated by taking into account at least the data symbol and at least one of the spread spectrum chips;

means for performing Gaussian Minimum Shift Keying (GMSK) modulation using the sequence of pre-modulation chips to produce a spread spectrum GMSK signal;

means for transmitting the spread spectrum GMSK signal;

wherein the spread spectrum GMSK signal adopts antipodal signaling to represent each data symbol; and

wherein for each data symbol, if the data symbol takes on a first binary value, a corresponding portion of the spread spectrum GMSK signal exhibits a select waveform, and if the data symbol takes on a second binary value, the corresponding portion of the spread spectrum GMSK signal exhibits a phase-inverted version of the select waveform.