Granted Patent B2

US 7,869,409 · App. 11/691,349 · Granted Jan 11, 2011

Abstract

Claims (50)

1. A communications signal transmitter for wirelessly transmitting more than one type of data packet, comprising:

a media access controller for generating a structure of a data packet, for generating a serial data stream of bits representing contents of the data packet, and for generating a frame length start signal that indicates length of a frame of the data packet, wherein the media access controller simultaneously outputs the serial data stream of bits to a first portion of the transmitter and to a second portion of the transmitter,

wherein the first portion of the transmitter includes:

a pseudorandom (PN) code generator, coupled to the media access controller, for spreading symbols of the serial data stream of bits into PN chips, and

an encoding circuit, having an input coupled to the PN code generator, for encoding offset quadrature phase shift keying (O-QPSK) to minimum shift keying (MSK), and for outputting spread spectrum chips that represent the contents of the data packet, wherein the outputting of said spread spectrum chips occurs subsequent to inputting of the serial data stream of bits into the first portion of the transmitter by an amount of time equal to a total group delay without use of a tapped delay line in the first portion of the transmitter, and

wherein the second portion of the transmitter includes:

a first tapped delay line, coupled to the media access controller, for delaying the serial data stream of bits by an amount equal to the total group delay, and for outputting non-spread spectrum bits that represent the contents of the data packet;

a second tapped delay line, coupled to the media access controller, for delaying the frame length start signal by the amount equal to the total group delay; and

a multiplexer, coupled to the second tapped delay line, for receiving at one input the spread spectrum chips from the encoding circuit, and at another input the non-spread spectrum bits from the first tapped delay line, an output from the multiplexer being selected by a delayed frame length start signal, a value of the delayed frame length start signal being dependent upon the type of data packet.

2. The communications signal transmitter of claim 1 , in which the encoding circuit encodes offset quadrature phase shift keying (O-QPSK) to minimum shift keying (MSK) by binary differential decoding followed by alternate bit inversion.

3. The communications signal transmitter of claim 1 , in which the data packet comprises a packet header and a data payload, and in which the media access controller generates a value to a field within the packet header to indicate the type of data packet.

4. The communications signal transmitter of claim 3 , in which the packet header comprises a preamble and a start of frame delimiter (SFD), and in which the media access controller generates a value to a field within the SFD to indicate the type of data packet.

5. The communications signal transmitter of claim 3 , in which the media access controller generates a value for the frame length start signal, such that the frame length start signal momentarily changes its value with occurrence, at an input of the multiplexer, of a beginning edge of a first bit of the data payload.

6. The communications signal transmitter of claim 3 , in which the data payload comprises a payload data length portion and a payload portion.

7. The communications signal transmitter of claim 6 , in which the media access controller generates a value for the frame length start signal, such that the frame length start signal momentarily changes its value with occurrence, at an input of the multiplexer, of a beginning edge of a first bit of the payload data length portion.

8. The communications signal transmitter of claim 3 , in which the multiplexer receives at one input spread spectrum MSK chips from the encoding circuit that represent the contents of the data payload of the data packet, and at another input receives non-spread spectrum bits from the first tapped delay line which bits represent the contents of the data payload of the data packet, depending upon the type of data packet.

9. The communications signal transmitter of claim 1 , in which the media access controller generates the value of the frame length start signal to indicate the type of data packet.

10. A method for transmitting a wireless data packet, the wireless data packet comprising a packet header and a data payload, the method comprising the steps of:

generating a structure and contents of a wireless data packet to be transmitted;

generating contents of the data payload of the wireless data packet as bits of a serial bit stream;

determining a type of the wireless data packet to be transmitted;

performing symbol to pseudorandom (PN) code mapping on the contents of the packet header of the wireless data packet to be transmitted, wherein the symbol to PN code mapping is accomplished over a first interval of time;

performing O-QPSK to MSK encoding on the contents of the packet header of the wireless data packet to be transmitted by binary differential decoding followed by alternate bit inversion, thereby producing spread spectrum MSK chips that represent the contents of the packet header, wherein the O-QPSK to MSK encoding is accomplished over a second interval of time; and

in response to the type of wireless data packet to be transmitted, performing one of sub-steps a) and sub-steps b):

a) performing symbol to PN code mapping on the contents of the data payload,

performing O-QPSK to MSK encoding on the contents of the data payload by binary differential decoding followed by alternate bit inversion, and

modulating the wireless data packet using minimum shift keying;

b) delaying the serial bit stream of the contents of the data payload by an amount of delay equal to the sum of the first interval of time and the second interval of time such that timing between a last spread spectrum MSK chip of the packet header and a first bit of the data payload is aligned, and

modulating the wireless data packet using minimum shift keying such that the spread spectrum MSK chips that represent the contents of the packet header and non-spread spectrum bits that represent the contents of the data payload, are modulated without any loss of information.

11. The method of claim 10 , in which the step of generating a structure and contents of a wireless data packet to be transmitted includes

generating a packet header, the packet header including a preamble and a start of frame delimiter (SFD), and

generating a data payload, the data payload including a payload data length portion and a payload portion, and

wherein the serial bit stream of the contents of the data payload is delayed such that timing between a last chip of the SFD and a first bit of payload data length portion is aligned.

12. The method of claim 11 , in which the step of generating a structure and contents of a wireless data packet to be transmitted includes generating one of

a first pre-defined value for the SFD, the first pre-defined value corresponding to a value of the SFD defined by the IEEE 802.15.4 standard, and

a second pre-defined value for the SFD, the second pre-defined value corresponding to a value not defined by the IEEE 802.15.4 standard.

13. The method of claim 11 , in which the step of determining includes determining whether the data payload of the wireless data packet is to be transmitted as a spread spectrum signal.

14. The method of claim 13 , in which the step of determining includes determining whether the data payload of the wireless data packet is to be transmitted as a spread spectrum signal based upon the value of the SFD.

15. The method of claim 14 , in which the data payload of the wireless data packet is modulated in a phase coherent, offset quadrature phase shift keying technique defined for spreading chips pursuant to the IEEE 802.15.4 standard.

16. The method of claim 11 , in which the step of determining includes determining whether the data payload of the wireless data packet is to be transmitted as a non-spread spectrum signal.

17. The method of claim 16 , in which the step of determining includes determining whether the data payload of the wireless data packet is to be transmitted as a non-spread spectrum signal based upon the value of the SFD.

18. The method of claim 17 , in which the data payload of the wireless data packet is modulated in a phase coherent, offset quadrature phase shift keying technique defined for spreading chips pursuant to the IEEE 802.15.4 standard.

19. The method of claim 10 , in which the serial bit stream of the contents of the data payload is delayed by an amount equal to the first interval of time used by the step of performing symbol PN code mapping plus the second interval of time used by the step of performing O-QPSK to MSK encoding.

20. A transmitter for transmitting data packets modulated in a phase coherent, offset quadrature phase shift keying technique defined for spreading chips pursuant to the IEEE 802.15.4 standard, each data packet including a preamble, a start of frame delimiter, a payload data length portion and a payload portion, the transmitter comprising:

a media access controller for generating a structure of a data packet, for generating a serial data stream of bits representing contents of the data packet, and for generating a frame length start signal that indicates length of a frame of the data packet;

a pseudorandom (PN) code generator, coupled to the media access controller, for spreading symbols of the contents of the data packet into PN chips, wherein the PN code accomplishes spreading symbols of the contents of the data packet into PN chips over a first interval of time;

an encoding circuit, coupled to the PN code generator, wherein the encoding circuit accomplishes O-QPSK to MSK encoding over a second interval of time;

a first tapped delay line, coupled to the media access controller, for delaying the contents of the data packet by an amount of time equal to the first interval of time plus the second interval of time;

a second tapped delay line, coupled to the media access controller, for delaying the frame length start signal by an amount of time equal to the first interval of time plus the second interval of time; and

a multiplexer, having inputs coupled to the encoding circuit and to the first tapped delay line, for receiving, at one input, spread spectrum chips from the encoding circuit that represent the contents of the preamble and start of frame delimiter, and for receiving, at another input, bits from the first tapped delay line that represent the contents of the payload data length portion and the payload portion, the output from the multiplexer being selected by a delayed frame length start signal, the frame length start signal momentarily changing its value with occurrence, at an input of the multiplexer, of a beginning edge of a first bit of the payload data length portion.

Assignments (26)