LPI/LPD communication systems

• US 8,929,550 B2
• Filed: 02/01/2013
• Issued: 01/06/2015
• Est. Priority Date: 02/01/2013
• Status: Active Grant

• Current Assignee: Department 13, Inc. (Department 13 International Ltd.)
• Original Assignee: Department 13 LLC (Department 13 International Ltd.)
• Inventors: Shattil, Steve J, Sen, Robi
• Primary Examiner(s): Reza, Mohammad W
• Application Number:
  US13/757,032
• Publication Number:
  US 20140219449A1
• Time in Patent Office: 704 Days
• Field of Search: 380/33, 380/204, 380/206
• US Class Current: 380/270
• CPC Class Codes: H04B 7/0456 Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0055 Physical resource allocation for ACK/NACK for physical mapping arrangements in ARQ protocols H04L1/1861
• CPC Class Codes: H04L 63/0435 wherein the sending and receiving network entities apply symmetric encryption, i.e. same key used for encryption and decryption cryptographic mechanisms or cryptographic arrangements for symmetric key encryption H04L9/06
• CPC Class Codes: H04L 63/061 for key exchange, e.g. in peer-to-peer networks cryptographic mechanisms or cryptographic arrangements for key agreement H04L9/0838
• CPC Class Codes: H04L 9/0875 based on channel impulse response [CIR]
• CPC Class Codes: H04W 12/041 Key generation or derivation
• CPC Class Codes: H04W 12/08 Access security
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 72/541 using the level of interference

Abstract

A node in a first network requests a communication channel from a second network. Upon receiving a channel assignment, nodes in the first network employ the assigned channel for communicating in a manner that is transparent to the second network. A transmitting node selects a decoy data signal as a carrier signal, synthesizes data-bearing channel distortions; and distorts the carrier signal with the channel distortions prior to transmission. An undistorted version of the decoy data may be transmitted to an intended receiver. The receiver distinguishes between the synthesized data-bearing channel distortions and natural channel distortions to decrypt the data. In a MIMO system, the transmitter generates a MIMO precoding matrix from a message to be sent to the receiver and multiplies the decoy data signal vector with the MIMO precoding matrix.

Claims

1. A communication method, comprising:

selecting a decoy data vector as a carrier signal;

synthesizing a precoding matrix comprising data-bearing synthesized multipath distortions;

precoding the decoy data vector with the precoding matrix to produce a precoded data vector; and

transmitting the precoded data vector to an intended receiver such that the intended receiver can filter out natural multipath distortions from the data-bearing synthesized multipath distortions in a received signal.

2. The method of claim 1, further comprising providing an undistorted version of the decoy data vector to the intended receiver.

3. The method of claim 1, wherein the synthesized multipath distortions are a function of channel measurements.

4. The method of claim 1, wherein the decoy data vector comprises at least one of a retransmitted broadcast signal, a predetermined data sequence that can be locally reproduced by the intended receiver, a data sequence stored in memory at the intended receiver, and a clean replica supplied to the intended receiver via an alternative channel.

5. A communication method, comprising:

receiving from a multipath channel, a distorted signal comprising a decoy data vector precoded with a precoding matrix having synthesized data-bearing multipath distortions;

receiving a clean decoy data vector;

filtering out natural multipath distortions and the decoy data vector from the distorted signal for estimating data from the synthesized data-bearing multipath distortions.

6. The method of claim 5, wherein the clean decoy data vector comprises at least one of a decoy data signal received from a third-party network, a decoy data signal received from a different channel in a network from which the distorted signal is received, a known training sequence, a locally stored data sequence, and a locally generated data sequence.