SMOOTH MODULATION SWITCHING

• US 20100260290A1
• Filed: 04/13/2009
• Published: 10/14/2010
• Est. Priority Date: 04/13/2009
• Status: Active Grant

• Current Assignee: Altobridge Limited (Singapore Technologies Engineering Limited)
• Original Assignee: ADC Telecommunications Incorporated (TE Connectivity Limited)
• Inventors: Elyasi, Sattar
• Granted Patent: US 8,379,761 B2
• Time in Patent Office: Days
• US Class Current: 375/305
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/009 arrangements specific to transmitters

Abstract

A transmitter comprises a channel encoder to encode data bits; a modulator to modulate the encoded data bits, wherein the modulator selects one of a first modulation scheme and a second modulation scheme for each of a plurality of time slots; wherein, for each time slot, the channel encoder: includes a prefix and a suffix at the beginning and end, respectively, of the encoded data bits corresponding to the respective time slot, the prefix and the suffix being selected based on the selected modulation scheme for the respective time slot; and passes the prefix, the encoded data bits, and the suffix to the modulator; wherein, for each time slot, the modulator: modulates the prefix, the encoded data bits, and the suffix received from the channel encoder according to the selected modulation scheme for the respective time slot; and applies a window function to the prefix and the suffix.

Claims

1. A transmitter that transmits modulated signals over a communication link, the transmitter comprising:

a channel encoder to encode data bits;

a modulator to modulate the encoded data bits, wherein the modulator selects one of a first modulation scheme and a second modulation scheme for each of a plurality of time slots;

wherein, for each time slot, the channel encoder;

includes a prefix and a suffix at the beginning and end, respectively, of the encoded data bits corresponding to the respective time slot, the prefix and the suffix being selected based on the selected modulation scheme for the respective time slot; and

passes the prefix, the encoded data bits, and the suffix to the modulator;

wherein, for each time slot, the modulator;

modulates the prefix, the encoded data bits, and the suffix received from the channel encoder according to the selected modulation scheme for the respective time slot; and

applies a window function to the prefix and the suffix.

2. The transmitter of claim 1, wherein the first modulation scheme is Gaussian Minimum-Shift Keying (GMSK) and the second modulation scheme is 8-Phase Shift Keying (8-PSK).

3. The transmitter of claim 2, wherein the prefix and the suffix corresponding to the first modulation scheme each comprise a constant bit repeated a predefined number of times;

and

wherein the prefix and the suffix corresponding to the second modulation scheme each comprise a constant symbol repeated a predefined number of times.

4. The transmitter of claim 1, wherein the window function is a Hanning window function.

5. The transmitter of claim 1, wherein the modulator combines the prefix, the encoded data bits, and the suffix from consecutive time slots such that at least a portion of the prefix corresponding to each time slot is transmitted during a guard band prior to the respective time slot of the prefix.

6. The transmitter of claim 1, wherein the modulator combines the prefix, the encoded data bits, and the suffix from consecutive time slots such that at least a portion of the prefix corresponding to each time slot is transmitted during a period when power levels on the communication link are at a minimum level.

7. The transmitter of claim 1, wherein the communication link comprises a control channel, and wherein the modulator only applies the Hanning window to the prefix and the suffix of consecutive time slots on the control channel when the selected modulation scheme corresponding to the consecutive time slots is different from one time slot to another.

8. The transmitter of claim 1, wherein the transmitter further comprises a radio frequency (RF) module that up-converts the modulated prefix, encoded data bits, and suffix.

9. A communication system comprising:

at least one wireless communication unit to transmit to and receive wireless signals from at least one mobile device over a communication link; and

a controller coupled to the at least one wireless communication unit to

wherein the at least one wireless communication unit comprises;

a receiver to demodulate received signals and to decode data bits in the demodulated signals; and

a transmitter to encode data bits from a data source and to modulate data bits for transmission to the at least one mobile device;

wherein the transmitter selects one of a first modulation scheme and a second modulation scheme for each of a plurality of time slots;

wherein, for each time slot, the transmitter;

includes a prefix and a suffix at the beginning and end, respectively, of the encoded data bits corresponding to the respective time slot, the prefix and the suffix being selected based on the selected modulation scheme for the respective time slot;

modulates the prefix, the encoded data bits, and the suffix according to the selected modulation scheme for the respective time slot; and

applies a window function to the modulated prefix and the modulated suffix.

10. The communication system of claim 9, wherein the communication system is a Global System for Mobile communications (GSM) network.

11. The communication system of claim 9, wherein the first modulation scheme is Gaussian Minimum-Shift Keying (GMSK) and the second modulation scheme is 8-Phase Shift Keying (8-PSK).

12. The communication system of claim 11, wherein the prefix and the suffix corresponding to the first modulation scheme each comprise a constant bit repeated a predefined number of times;

and

wherein the prefix and the suffix corresponding to the second modulation scheme each comprise a constant symbol repeated a predefined number of times.

13. The communication system of claim 9, wherein the window function is a Hanning window function.

14. The communication system of claim 9, wherein the transmitter transmits the prefix, the encoded data bits, and the suffix from consecutive time slots such that at least a portion of the prefix corresponding to each time slot is transmitted during a guard band prior to the respective time slot of the prefix.

15. The communication system of claim 9, wherein the transmitter transmits the prefix, the encoded data bits, and the suffix from consecutive time slots such that at least a portion of the prefix corresponding to each time slot is transmitted during a period when power levels on the communication link are at a minimum level.

16. The communication system of claim 9, wherein the communication link comprises a control channel, and wherein the transmitter only applies the Hanning window to the prefix and the suffix of consecutive time slots on the control channel when the selected modulation scheme corresponding to the consecutive time slots is different from one time slot to another.

17. A method of communicating data in a system utilizing time slots, the method comprising:

selecting one of a first modulation scheme and a second modulation scheme for each time slot;

prepending data corresponding to each respective time slot with a prefix based on the selected modulation scheme for each respective time slot;

appending the data corresponding to each respective time slot with a suffix based on the selected modulation scheme for each respective time slot;

modulating the prefix, the data, and the suffix according to the selected modulation scheme for each respective time slot;

applying a window function to the modulated prefix, the data, and the suffix for each time slot; and

transmitting the prefix, the data, and the suffix over a communication link for each respective time slot such that at least a portion of the prefix is transmitted during a period when power levels on the communication link are at a minimum level.

18. The method of claim 17, wherein the period when power levels on the communication link are at a minimum level occurs during a guard band prior to the respective time slot of the prefix.

19. The method of claim 17, wherein the window function is a Hanning window function.

20. The method of claim 17, wherein the prefix and the suffix corresponding to the first modulation scheme each comprise a constant bit repeated a predefined number of times;

and

wherein the prefix and the suffix corresponding to the second modulation scheme each comprise a constant symbol repeated a predefined number of times.

21. The method of claim 17, wherein the first modulation scheme is Gaussian Minimum-Shift Keying (GMSK) and the second modulation scheme is 8-Phase Shift Keying (8-PSK).

22. A program product comprising a processor-readable medium on which program instructions are embodied, wherein the program instructions are operable, when executed by at least one programmable processor included in a device that modulates and transmits communication signals, to cause the device to:

pre-pend a prefix to received data in each of a plurality of time slots based on a selected modulation scheme for each respective time slot;

append a suffix to the received data in each respective time slot based on the selected modulation scheme for each respective time slot;

modulate the prefix, the data, and the suffix according to the selected modulation scheme for each respective time slot;

apply a window function to the modulated prefix, the data, and the suffix for each time slot; and

transmit the prefix, the data, and the suffix over a communication link for each respective time slot such that at least a portion of the prefix is transmitted during a period when power levels on the communication link are at a minimum level.

23. The program product of claim 22, wherein the program instructions are further operable to cause the device to transmit the prefix, the data, and the suffix over the communication link for each respective time slot such that at least a portion of the prefix is transmitted during a guard band prior to the scheduled transmission time of the respective time slot.

24. The program product of claim 22, wherein the program instructions are further operable to cause the device to apply a Hanning window function.

25. The program product of claim 22, wherein the program instructions are further operable to:

pre-pend a prefix comprising a constant bit repeated a predefined number of times and append a suffix comprising a constant bit repeated a predefined number of times when a first modulation scheme is selected; and

pre-pend a prefix comprising a constant symbol repeated a predefined number of times and append a suffix comprising a constant symbol repeated a predefined number of times when a second modulation scheme is selected.

26. The method of claim 25, wherein the first modulation scheme is Gaussian Minimum-Shift Keying (GMSK) and the second modulation scheme is 8-Phase Shift Keying (8-PSK).