# US 12,009,961 B2 · System and method for preamble detection in MIMO narrowband power line communications > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,009,961 B2 - Document ID: US12009961B2 - Status: Granted - Kind: B2 - Application number: 17/142,607 - Filed: 2021-01-06 - Published: 2021-05-27 - Granted: 2024-06-11 - Earliest claimed: 2014-09-30 - Assignees: Texas Instruments Incorporated - Applicants: Texas Instruments Incorporated - Inventors: Mostafa Sayed Ibrahim; Il Han Kim; Tarkesh Pande; Anuj Batra - Web page: https://patentgrep.com/patent/US12009961B2 ## CPC - H04L 27/2656: {Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation} - H04B 3/54: Systems for transmission via power distribution lines - H04B 3/542: {the information being in digital form} - H04B 3/546: {Combination of signalling, telemetering, protection (circuits for remote indication of supply or distribution network condition H02J13/00)} - H04B 7/0413: MIMO systems - H04L 5/0023: {Time-frequency-space} - H04L 7/042: {Detectors therefor, e.g. correlators, state machines (digital correlators in general G06F17/15)} - H04L 27/26: Systems using multi-frequency codes (H04L27/32 takes precedence) - H04L 27/2602: {Signal structure} - H04L 27/2603: {Signal structure ensuring backward compatibility with legacy system} - H04L 27/2613: {Structure of the reference signals} - H04L 27/2655: {Synchronisation arrangements} - H04L 27/2663: {Coarse synchronisation, e.g. by correlation} - H04W 74/0816: with collision avoidance - H04L 1/188: {Time-out mechanisms} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract A PLC network system and method operative with OFDM for generating MIMO frames with suitable preamble portions configured to provide backward compatibility with legacy PLC devices and facilitate different receiver tasks such as frame detection and symbol timing, channel estimation and automatic gain control (AGC), including robust preamble detection in the presence of impulsive noise and frequency-selective channels of the PLC network. A PLC device may include a delayed correlation detector and a cross-correlation detector operating in concert to facilitate preamble detection in one implementation. ## Claims ### Claim 1 A device comprising: an input port configured to receive a PLC signal stream over a first pair of power lines of a power line communications (PLC) network, wherein the received PLC signal stream comprises a preamble, wherein the preamble has a known number K of symbols, and wherein K is an integer greater than or equal to 1; and a detector coupled to the input port and configured to: correlate the received PLC stream with a known preamble to generate a cross-correlation output profile; determine a first estimate of the preamble start by: placing a window of length equal to K symbols and divided into K symbol regions over the received PLC signal; and adding one sample in the PLC signal stream to an end of the window and remove one sample in the PLC signal stream from a beginning of the window; and determine a second estimate of the preamble start based on the cross-correlation output profile and further based on the first estimate of the preamble start. ### Claim 2 (depends on 1) The device of claim 1, wherein the known preamble is a legacy preamble according to a legacy PLC data transmission standard or a Multi-Input Multi-Output (MIMO) preamble. ### Claim 3 (depends on 1) The device of claim 1, wherein the input port is configured to receive a file control header (FCH). ### Claim 4 (depends on 1) The device of claim 1, wherein the received PLC signal stream comprises a Multi-Input Multi-Output (MIMO) frame received via an [NT×NR] MIMO channel in the PLC network, the MIMO frame including a legacy preamble portion, a Frame Control Header (FCH) portion including legacy FCH data and MIMO-compliant data, a MIMO-compliant preamble portion, and a payload data portion. ### Claim 5 A method comprising: receiving a power line communication (PLC) signal stream over a first pair of power lines of a PLC network, wherein the PLC signal stream comprises a preamble, wherein the preamble has a known number K of symbols, and wherein K is an integer greater than or equal to 1; determining a first estimate of the preamble start by: placing a window of length equal to K symbols and divided into K symbol regions over the received PLC signal stream; and adding one sample in the PLC signal stream to an end of the window and removing one sample in the PLC signal stream from a beginning of the window; correlating the received PLC signal stream with a known preamble to generate a cross-correlation output profile; and determining a second estimate of the preamble start based on the cross-correlation output profile and further based on the first estimate of the preamble start. ### Claim 6 (depends on 5) The method of claim 5, wherein the preamble is a first Multi-Input Multi-Output (MIMO) preamble. ### Claim 7 (depends on 5) The method of claim 5, wherein the received PLC signal stream comprises a Multi-Input Multi-Output (MIMO) frame received via an [NT×NR] MIMO channel in the PLC network, the MIMO frame including a legacy preamble portion, a Frame Control Header (FCH) portion including legacy FCH data and MIMO-compliant data, a MIMO-compliant preamble portion, and a payload data portion. ### Claim 8 (depends on 5) The method of claim 5, wherein the preamble is used to provide channel estimation for decoding a file control header. ### Claim 9 A device, comprising: a detector configured to: select a sliding window that spans a known number of SYNCP and SYNCM symbols; move the sliding window over a power line communications (PLC) signal stream one sample at a time, the PLC signal stream received over a first pair of power lines of a PLC network; calculate, for each window placement, a set of delayed correlations based on a select correlation order; add absolute values of delayed correlations together to obtain a total correlation value for each window placement over the PLC signal stream; apply a threshold against the total correlation values; and select a sample index having maximum correlation as an initial estimate of a preamble start based on a maximization length parameter. ### Claim 10 (depends on 9) The detector of claim 9, wherein each of the SYNCP and SYNCM symbols is 256 samples long. ### Claim 11 (depends on 9) The detector of claim 9, wherein the PLC signal stream includes a preamble operative according to a legacy PLC data transmission standard. ### Claim 12 (depends on 9) The detector of claim 9, wherein the PLC signal stream comprises a preamble having 8 SYNCP symbols followed by a full SYNCM symbol and a half SYNCM symbol, each symbol including a plurality of OFDM samples. ### Claim 13 (depends on 9) The detector of claim 9, wherein the PLC signal stream comprises a Multi-Input Multi-Output (MIMO) frame received via an [NT×NR] MIMO channel in the PLC network, the MIMO frame including a legacy preamble portion, a Frame Control Header (FCH) portion including legacy FCH data and MIMO-compliant data, a MIMO-compliant preamble portion, and a payload data portion. ### Claim 14 A method, comprising: correlating a power line communications (PLC) signal stream with a preamble to generate a cross-correlation output profile, wherein the preamble has a known number K of symbols, K is an integer greater than or equal to 1, the PLC signal stream received over a first pair of power lines of a PLC network; receiving a first estimate of the preamble start; performing a correlation between the PLC signal stream with a delayed version of the PLC signal stream by: placing a window of length equal to K symbols and divided into K symbol regions over the PLC signal stream, and adding one sample in the PLC signal stream to an end of the window and removing one sample in the PLC signal stream from a beginning of the window; and determining a second estimate of the preamble start based on the cross-correlation output profile and further based on the first estimate of the preamble start, wherein the first estimate of the preamble start is based on the correlation between the PLC signal stream with the delayed version of the PLC signal stream. ### Claim 15 (depends on 14) The method of claim 14, wherein the preamble is operative according to a legacy PLC data transmission standard. ### Claim 16 (depends on 14) The method of claim 14, wherein the preamble comprises 8 SYNCP symbols followed by a full SYNCM symbol and a half SYNCM symbol, each symbol including a plurality of OFDM samples. ### Claim 17 (depends on 14) The method of claim 14, wherein the PLC signal stream comprises a Multi-Input Multi-Output (MIMO) frame received via an [NT×NR] MIMO channel in the PLC network, the MIMO frame including a legacy preamble portion, a Frame Control Header (FCH) portion including legacy FCH data and MIMO-compliant data, a MIMO-compliant preamble portion, and a payload data portion.