Physically secure digital signal processing for wireless M2M networks

• US 9,648,444 B2
• Filed: 01/06/2014
• Issued: 05/09/2017
• Est. Priority Date: 01/06/2014
• Status: Active Grant

• Current Assignee: Brian G. Agee
• Original Assignee: Brian G. Agee
• Inventors: Agee, Brian G.
• Primary Examiner(s): TAYONG, HELENE E
• Application Number:
  US13/999,040
• Publication Number:
  US 20150195670A1
• Time in Patent Office: 1,219 Days
• Field of Search: 375133, 375144
• CPC Class Codes: H04B 1/692 Hybrid techniques using combinations of two or more spread spectrum techniques
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 1/7156 Arrangements for sequence synchronisation
• CPC Class Codes: H04B 2001/7154 with means for preventing interference
• CPC Class Codes: H04J 13/0007 Code type
• CPC Class Codes: H04W 4/70 Services for machine-to-machine communication [M2M] or machine type communication [MTC]

Abstract

A method and apparatus for physically secure communication over machine-to-machine (M2M) networks is claimed, through the use of frequency-hop and random access spread spectrum modulation formats employing using truly random spreading codes and time/frequency hopping and receiver selection strategies at the transmitters in the M2M network, blind signal detection and linear signal separation techniques at the receivers in the M2M network, completely eliminating the ability for an adversary to predict and override M2M transmissions. Additional physical security protocols are also introduced that allow the network to easily detect and identify spoofing transmissions on uplinks and downlinks, and to automatically excise those transmissions as part of the despreading procedure, even if those transmissions are received at a much higher power level than the intended transmissions. Extensions to weakly and strongly macrodiverse networks are also described, which provide additional efficiency and security improvements by exploiting the route diversity of the network.

Claims

1. A method for physically secure digital signal processing for intercommunication between members, of a wireless Machine-to-Machine (‘

M2M’

) network comprising at least one Signaling Machine (‘

SM’

) and one Data Aggregation Point (DAP), with each SM and DAP individually comprising at least one transceiver, at least one antenna, and digital signal processing means, by exchanging wireless transmissions between a first member and a second member, said method comprising;

first, for each intended intercommunication between any first member and second member,

selecting for each transmission of that intercommunication a Cyclic-Prefix Direct-Sequence (‘

CPDS’

) differentiator by any of randomly, pseudorandomly, or a varying selection method;

then,

modifying the intended intercommunication by said CPDS differentiator;

transmitting the intended intercommunication that has been modified to an intended second member;

receiving at the antenna of the second member the intended communication and;

identifying, through use of a blind, time-channelized despreading algorithm, the intended intercommunication from other non-intended signals;

identifying the selected CPDS differentiator modifying the intended intercommunication;

and, restoring the received intended intercommunication by removing the selected CPDS differentiator.

2. The method for physically secure digital signal processing for intercommunication between members of the wireless M2M network as in claim 1, wherein the selected CPDS differentiator further comprises a combination of a transformation of the intended communication by a receive mask, a source mask, and a cyclic prefix for any of a set of symbols comprising the intercommunication to be transmitted.

3. A method for wireless intercommunication between at least one Signaling Machine (‘

SM’

) and one Data Aggregation Point (DAP′

) each belonging to a set of like devices, all transmitting and receiving and belonging to the same network, of which each said device is a node, said method further comprising;

effecting within a selected frequency range a frequency-hop direct-sequence (FHDS), spread-spectrum modulation format further comprising time slots, frequency channels, at least one data burst and guard intervals;

providing through said FHDS modulation format, cyclic chip-level and symbol-level cyclic prefixes to control channel multipath and interference loading; and

,

employing transmission information that is randomly determined at any node in the network, not provisioned by the network nor known to receivers in the network;

incorporating a spreading code for every uplink and downlink;

including in said randomly determined transmission information on each uplink, and randomly varying over every time frame;

the time slots and frequency channels used for that specific uplink and by that specific node;

the spreading code used for that specific uplink and by that specific node; and

,

elements of a source symbol mask applied to the data bursts prior to spreading;

including in said randomly determined transmission information on each downlink;

the spreading code used for that specific downlink and by that specific node and randomly varied in every time slot of each time frame; and

,

elements of a source symbol mask applied to the data bursts prior to spreading also randomly varied over every time frame;

transmitting from each downlink transmit node, over a downlink frequency channel using an algorithm that is any of the set of providable, known to, and learnable by each downlink receiver allowed to communicate with that downlink transmit node, said algorithm being further locally and independently set at said downlink transmit node.

4. The method for wireless intercommunication as in claim 3, wherein the step of transmitting from each downlink transmit node, over the downlink frequency channel, varies the frequency channel pseudorandomly over each time slot of each time frame.

5. The method for wireless intercommunication between at least one Signaling Machine (‘

SM’

) and one Data Aggregation Point (‘

DAP’

) each belonging to a set of like devices as in claim 3, wherein the step of employing transmission information that is randomly determined at any node in the network, not provisioned by the network nor known to the receivers in the network, is provisioned at and by each transmitter with each intended receiver being blind to the choice of that randomly determined transmission information, and utilizing only rudimentary provisioning from any specific transmitter in the network to only its intended set of receivers in the network of a commonly-known and shared receive symbol mask for all signals intended for a given set of receivers so as to differentiate them from transmissions by that specific transmitter intended for other nodes in the network, as well as transmissions from other transmitters in the network intended for that particular set of receivers.

6. A method for physically secure digital signal processing for wireless Machine-to-Machine (‘

M2M’

) networks, said networks comprising at least one set of transceivers comprising at least one Signaling Machine (‘

SM’

) and one Data Aggregation Point (‘

DAP’

) with each SM and DAP comprising at least one antenna and one transceiver for exchanging wireless transmissions, said method comprising;

transforming each transmission by incorporating into each transmission at each transceiver a Cyclic-Prefix Direct-Sequence (‘

CPDS’

) differentiator for that transmission with time-channelized despreading;

fitting each transmission into a series of frames of Upload Transmissions (‘

UpLink’

) and Download Transmissions (‘

DownLink’

);

transmitting from the SM on any UpLink;

transmitting from the DAP on any DownLink; and

,

after receiving each transmission at an antenna, for each such transmission;

downconverting the transmission;

demultiplexing the downconverted transmission into physical dwells which are separated into time slots and frequency channels and accessible to the receiver, thus forming for each time slot, frequency channel, and frame a received signal; and

,

adaptively despreading the received signal to create an incoming and received digital symbol stream.

7. The method for physically secure digital signal processing for wireless M2M networks as in claim 6, where in the step of then fitting each transmission into the series of frames of Upload Transmissions (‘

UpLink’

) and Download Transmissions (‘

DownLink’

) further comprises;

for information intended for transmission in a single UpLink slot of each frame and thus passing through an UpLink transmitter;

first passing said information through baseband encoding utilizing any of a set of baseband encoding algorithms and adding Physical Layer (PHY) signatures including any of training preambles and Unique Words, to create a baseband source symbol stream output from any encoder, at each symbol index used by the UpLink transmitter;

passing the baseband source symbol stream to a cyclic-prefix direct-sequence (‘

CPDS’

) spreader;

segmenting the baseband source symbol stream into symbol-source data segments;

modulating each symbol-source data segment to generate the spread source data stream output from the CPDS spreader at each chip index;

then subsequently pulse-amplitude modulating the spread source data stream output;

converting this subsequently pulse-amplitude modulated spread source data stream output to an analog signal-in-space (‘

SiS’

);

upconverting this analog SiS to a desired source frequency selected by the uplink transmitter within each time-frame n_frame;

for information intended for transmission in a single DownLink slot of each frame, and thus passing through a DownLink transmitter;

first passing said information through baseband encoding to create a baseband source symbol stream;

then passing the baseband source symbol stream to a cyclic-prefix direct-sequence (‘

CPDS’

) spreader which modulates each data segment to generate the spread source data stream output from the CPDS spreader at each chip index;

then subsequently pulse-amplitude modulating the spread source data stream output;

converting this subsequently pulse-amplitude modulated spread source data stream output to an analog signal-in-space (‘

SiS’

); and

,

upconverting this analog SiS to a desired source frequency selected by the downlink transmitter over each time slot and transmitting this analog SiS over the desired source frequency over each time slot at a source power level that is held constant over every time slot.

8. The method for physically secure digital signal processing for wireless M2M networks as in claim 7, wherein the step of selecting a desired source frequency by the uplink transmitter within time-frame n_frame further comprises utilizing any of a set of fixed, provisioned, pseudo-randomly directed, and randomly-directed selection methods within each frame.

9. The method for physically secure digital signal processing for wireless M2M networks as in claim 7 wherein the step of upconverting this analog SiS to a desired source frequency selected by the uplink transmitter over time slot n_slot;

and transmitting this analog SiS over the desired source frequency over time slot n_slot further comprises;

selecting randomly a source transmit time t_S(n_frame) and transmit frequency f_S(n_frame) within each frame, by randomly selecting dwell index k_dwell(n_frame) for that frame, without any prior scheduling or coordination between the uplink transmitter and the uplink receivers in the network;

mapping k_dwell(n_frame) to time slot k_slot(n_frame) and frequency channel k_chan(n_frame); and

,

selecting t_S(n_frame) from k_slot(n_frame) and f_S(n_frame) from k_chan(n_frame) via a look-up table.

10. The method for physically secure digital signal processing for wireless M2M networks as in claim 7, wherein the step of selecting a desired source frequency f_S(n_slot) by the downlink transmitter over time slot n_slot further comprises selecting a frequency channel k_chan(n_slot) and using the selected frequency channel to set a source frequency f_S(n_slot) using a pseudorandom selection algorithm based on the slot index n_slot and the source index l_S.

11. The method for physically secure digital signal processing for wireless M2M networks as in claim 6, further comprising, for any DownLink transmission, selecting a transmit frequency known to each intended DownLink receiver in the network over at least a subset of slots within each frame, without coordinating the selection with any other set of downlink transmitters in the network.

12. The method for physically secure digital signal processing for wireless M2M networks as in claim 6, further comprising, for any DownLink transmission, detecting the transmit frequency over any of each slot and a subset of monitored slots and frequency channels, without coordination with the DownLink transmitter.

13. The method for physically secure digital signal processing for wireless M2M networks as in claim 6, wherein the cyclic-prefix direct-sequence (‘

CPDS’

) spreader produces a CPDS uplink spreading structure using the following steps;

passing the baseband source symbols intended for transmission over time-frame n_frame through a 1;

M_sym serial-to-parallel (S/P) convertor to form a M_sym 1 source symbol vector

14. The method for physically secure digital signal processing for wireless M2M networks as in claim 13, wherein the source and receive masks each possess a constant modulus.

15. The method for physically secure digital signal processing for wireless M2M networks as in claim 13, wherein the source and receive masks are both designed to be circularly symmetric and cross-scrambling.

16. The method for physically secure digital signal processing for wireless M2M networks as in claim 13, wherein:

the source symbol mask is a complex sinusoid with a cyclic source frequency offset _S(n_frame) chosen randomly and communicated to the receiver, said source symbol mask given by m_S(n_sym;

n_frame)=exp{j2_S(n_frame)n_sym}.

17. The method for physically secure digital signal processing for wireless M2M networks as in claim 13, wherein at least one receive symbol mask has been made unique to each DAP in the network, and each DAP uses the receive symbol mask to identify those SM'"'"'s intending to communicate with it.

18. The method for physically secure digital signal processing for wireless M2M networks as in claim 11, wherein the receive symbol mask has been made common to every DAP in the network, allowing any DAP to despread any SM in that DAP'"'"'s field of view.

19. The method for physically secure digital signal processing for wireless M2M networks as in claim 18, wherein the network is macrodiverse and the symbol streams which are any of the set received and despread at multiple DAP'"'"'s, are further processed at deeper aggregation sites in the network.

20. The method for physically secure digital signal processing for wireless M2M networks as in claim 13, further comprising applying a modulation-on-symbol direct-sequence spread spectrum (‘

MOS-DSSS’

) operation, in which the spreading code is repeated over every baseband symbol within each hop and is used to spread the symbol vector d_S(n_frame) using a spreading code c_S(n_frame).

21. The method for physically secure digital signal processing for wireless M2M networks as in claim 13 wherein:

the step of performing an element-wise multiplication of this source symbol vector and an M_sym×

1 symbol mask vector is applied in the time domain if the cyclic symbol prefix duration=0; and

,

a cyclic chip prefix is added to the spreading code.

22. The method for physically secure digital signal processing for wireless M2M networks as in claim 13, wherein the step of performing an element-wise multiplication of the source symbol vector and an M_sym×

1 symbol mask vector

23. The method for physically secure digital signal processing for wireless M2M networks as in claim 13, wherein:

the source symbol mask is the complex sinusoid with the cyclic source frequency offset α

_S(n_frame) chosen pseudorandomly over frame n_frame and communicated to the receiver, said source symbol mask given by m_S(n_sym;

n_frame)=exp{j2π

α

_S(n_frame)n_sym}.

24. The method for physically secure digital signal processing for wireless M2M networks as in claim 13, wherein:

the source symbol mask is a complex sinusoid with a chosen cyclic source frequency offset _S(n_frame) communicated to the receiver, said source symbol mask given by m_S(n_sym;

n_frame)=exp{j2_S(n_frame)n_sym}; and

,

the receive symbol mask is tied to the specific time slot and hop channel used by the SM over each time frame.

25. The method for physically secure digital signal processing for wireless M2M networks as in claim 13;

wherein;

the step of performing an element-wise multiplication of this source symbol vector and an M_sym 1 symbol mask vector, is applied in the frequency domain using a discrete Fourier transform (‘

DFT’

) if the cyclic symbol prefix duration >

0; and

,

that resultant masked symbol vector is then converted back to the time domain utilizing an inverse DFT.

26. The method for physically secure digital signal processing for wireless M2M networks as in claim 6, wherein the step of adaptively despreading the received signal to create an incoming and received digital symbol stream further comprises:

passing the received signal, for each physical dwell the demultiplexed and downconverted transmission, through an UpLink CPDS despreader;

adaptively despreading the received signal by applying to it an adaptation algorithm using the received signal'"'"'s weighting WR observed by the receiver; and

,

passing the adaptively despread digital stream to a symbol demodulator which also uses the adaptation algorithm using for any combination of environmental delay and degradation effects, frequency offset estimates from the observed weighting by the receiver, to create a resulting symbol stream.

27. The method for physically secure digital signal processing for wireless M2M networks as in claim 6, wherein the step of transforming each transmission further comprises:

utilizing input from a real-world, random-number, sourcing-sensor element that provides a truly random kernel from real-world chance events to randomly generate a spreading code over every transmit opportunity which is every frame on the uplink, and every time slot on the downlink;

and then providing that spreading code to a CPDS spreader that generates the CPDS differentiator.

28. The method for physically secure digital signal processing for wireless M2M networks as in claim 6, wherein the step of transforming each transmission further comprises:

utilizing input from a real-world, random-number, sourcing-sensor element that provides a truly random kernel from real-world chance events to randomly generate a physical dwell index which is time slot and frequency channel over every time frame;

and then providing that physical dwell index to a CPDS spreader that generates the CPDS differentiator for the uplink transmission.

29. The method for physically secure digital signal processing for wireless M2M networks as in claim 6, wherein the step of transforming each transmission further comprises:

utilizing input from a real-world, random-number, sourcing-sensor element that provides a truly random kernel from real-world chance events to randomly generate at least one element of the source symbol mask over every time frame; and

then providing said randomly generated at least one element to a CPDS spreader that generates the CPDS differentiator for the uplink transmission.

30. The method for physically secure digital signal processing for wireless M2M networks as in claim 6, wherein the step of transforming each transmission further comprises:

utilizing input from a real-world, random-number, sourcing-sensor element that provides a truly random kernel from real-world chance events to randomly select an intended uplink receiver from a set of candidate uplink receivers over every time frame;

and then providing that selection of uplink receiver to a CPDS spreader that generates the CPDS differentiator for the uplink transmission.

31. The method for physically secure digital signal processing for wireless M2M networks as in claim 6, wherein the step of transforming each transmission further comprises:

using utilizing input from a real-world, random-number, sourcing-sensor element that provides a truly random kernel from real-world chance events to select any combination of the set of spreading code, physical dwell index, source signal mask, cyclic frequency offset, and intended receiver; and

then providing that selected combination to a CPDS spreader that generates the CPDS differentiator for that transmission.

32. The method for physically secure digital signal processing for wireless M2M networks as in claim 6, whereby

whenever a node is duplicated an original source and intended recipient can, each independently or together, compare any of the Physical Layer (‘

PHY’

) data bits in the received transmissions and use any discrepancy from previously observed values to identify an adversarial node;

and then ignore that now-identified adversarial node, alert other nodes in the network to both the presence, and the PHY observable characteristics, of that now-identified adversarial node, and otherwise respond.

33. The method for physically secure digital signal processing for wireless M2M networks as in claim 6, wherein the cyclic-prefix direct-sequence (‘

CLAUS’

) spreader produces a CPDS uplink spreading structure using the following steps;

passing the baseband source symbols intended for transmission over time-frame n_frame through a 1;

M_sym serial-to-parallel (SIP) convertor to form a M_sym×

1 source symbol vector

34. A device for adaptively despreading a received signal to create an incoming and received digital symbol stream comprising:

at least one antenna which receives an incoming analog signal-in-space, and passes it to;

a downconverter connected to at least one lowpass filter (‘

LPF’

) and then at least one analog-to-digital converter (‘

ADC’

);

a clock connected and signaling for a time slot to a channel identifying element which provides a frame for receipt for the time slot to a Local Oscillator (‘

LO’

) that also is connected to and receives a timing signal from the clock, with the LO also connected to and passing that combination to the downconverter;

said at least one ADC connected to and passing the received signal to;

a Cyclic-Prefix Direct-Sequence (‘

CPDS’

) despreader which is further connected to and passing a despread series to a symbol demodulator, said despread series being modified with a feedback loop through an adaptation algorithm element which uses the received signal'"'"'s weighting observed by the receiver, said adaptation algorithm element being connected to both the CPDS despreader and the symbol demodulator;

said symbol demodulator then incorporating frequency offset estimates also provided by the adaptation algorithm for environmental delay/degradation effects actually observed by the receiving device, to produce a series of symbols.