System and method for robust OFDM synchronization

Patent metadata

Field	Value
Publication number	US-10623229-B2
Application number	US-201916557551-A
Country	US
Kind code	B2
Filing date	Aug 30, 2019
Priority date	Oct 2, 2017
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

Systems and methods are disclosed and include a method that includes adding a training symbol prefix to an OFDM symbol frame, the prefix including a plurality of training symbols, each including N sub-symbol fields. N/2 of the sub-symbol fields are zero valued, and N/2 of the sub-symbol fields carry corresponding symbols of a N/2 sub-symbol pseudo random training symbol. A first half of the pseudo random training symbol is symmetrical to a second half of the pseudo random training symbol. An OFDM N-sub-carrier transmission carries the prefix as signal power on a first N/2 of its N sub-carriers and suppresses signal power on a second N/2 of the sub-carriers. The first N/2 and second N/2 sub-carriers alternate in the frequency domain.

First claim

What is claimed is:

1. A system for synchronizing a receiving of an orthogonal frequency division multiplexing (OFDM), the system comprising:
an input data interface configured to receive a sequence of signal samples and associated indexes;
a processing unit; and
a memory configured to a store a plurality of instructions that when read and executed by the processing unit cause the processing unit to:
generate an OFDM symbol frame,
add a training symbol prefix to the OFDM symbol frame, the training symbol prefix including a plurality of training symbols, each of the training symbols including N sub-symbol fields, wherein
a first N/2 of the sub-symbol fields are set at a zero value,
a second N/2 of the sub-symbol fields carry corresponding symbols of a N/2 sub-symbol pseudo random training symbol, and
a first half of the N/2 sub-symbol pseudo random training symbol is symmetrical to a second half of the N/2 sub-symbol pseudo random training symbol, and

transmit the training symbol prefix as a multi-carrier transmission within an OFDM N-sub-carrier transmission, the transmit being configured such that:
the multi-carrier prefix transmission carries signal power on a first N/2 of the N sub-carriers and suppresses signal power on a second N/2 of the sub-carriers, and
the first N/2 sub-carriers and the second N/2 sub-carriers are respectively aligned at alternating positions in the frequency domain.

2. The system of claim 1 , wherein the adding of the training symbol prefix to the OFDM symbol frame is configured wherein:
the N sub-symbol fields include N/2 even sub-symbol fields interleaved with N/2 odd sub-symbol fields,
the N/2 even sub-symbol fields are the first N/2 of the sub-symbol fields, and
the N/2 odd sub-symbol fields are the second N/2 of the sub-symbol fields.

3. The system of claim 1 , wherein to add the training symbol prefix to the OFDM symbol frame is configured wherein:
the N sub-symbol fields include N/2 even sub-symbol fields interleaved with N/2 odd sub-symbol fields,
the N/2 odd sub-symbol fields are the first N/2 of the sub-symbol fields, and
the N/2 even sub-symbol fields are the second N/2 of the sub-symbol fields.

4. The system of claim 1 , wherein:
to add the training symbol prefix to the OFDM symbol frame is configured such that each of the N/2 sub-symbols of the pseudo random training symbol is a complex value, the complex value being a mapping of a corresponding information symbol to an X-Y position in a complex plane, “X” being an in-phase component and “Y” being a quadrature component; and
to transmit the training symbol prefix as the multi-carrier transmission within the OFDM is further configured such that the signal power of each of the first N/2 of the N sub-carriers is a modulation, in amplitude and phase, of the sub-carrier N/2 corresponding to the complex value of one of the N/2 sub-symbols of the pseudo random training symbol.

5. The system of claim 1 , such that for each of the training symbols:
a first half of the training symbol's N sub-symbol fields includes a first half of the N/2 sub-symbols of the pseudo random training symbol interleaved with a first half of the N/2 sub-symbol fields of the training symbol that are set at a zero value,
a second half of the training symbol's N sub-symbol fields includes a second half of the N/2 sub-symbols of the pseudo random training symbol interleaved with a second half of the N/2 sub-symbol fields of the training symbol that are set at a zero value,
the first half of the N/2 sub-symbols of the pseudo random training symbol that is included in first half of the training symbol's N sub-symbol fields is identical to the second half of the N/2 sub-symbols of the pseudo random training symbol that is included in second half of the training symbol's N sub-symbol fields.

6. The system of claim 5 , such that for each of the training symbols the first half of the training symbol's N sub-symbol fields is symmetrical to the second half of the training symbol's N sub-symbol fields.

7. A method for communicating a robust synchronization orthogonal frequency division multiplexing (OFDM) frame, comprising:
generating an OFDM symbol frame;
adding a training symbol prefix to the OFDM symbol frame, the training symbol prefix including a plurality of training symbols, each of the training symbols including N sub-symbol fields, wherein
a first N/2 of the sub-symbol fields are set at a zero value,
a second of the N/2 sub-symbol fields carry corresponding symbols of a N/2 sub-symbol pseudo random training symbol, and
a first half of the pseudo random training symbol is symmetrical to a second half of the pseudo random training symbol; and

transmitting the training symbol prefix as a multi-carrier transmission within an OFDM N-sub-carrier transmission, wherein
the multi-carrier prefix transmission carries signal power on a first N/2 of the N sub-carriers and suppresses signal power on a second N/2 of the sub-carriers, and
the first N/2 sub-carriers and the second N/2 sub-carriers are respectively aligned at alternating positions in the frequency domain.

8. The method of claim 7 , wherein the adding of the training symbol prefix to the OFDM symbol frame is configured such that:
the N sub-symbol fields include N/2 even sub-symbol fields interleaved with N/2 odd sub-symbol fields,
the N/2 even sub-symbol fields are the first N/2 of the sub-symbol fields, and
the N/2 odd sub-symbol fields are the second N/2 of the sub-symbol fields.

9. The method of claim 7 , wherein adding the training symbol prefix to the OFDM symbol frame is configured wherein:
the N sub-symbol fields include N/2 even sub-symbol fields interleaved with N/2 odd sub-symbol fields,
the N/2 odd sub-symbol fields are the first N/2 of the sub-symbol fields, and
the N/2 even sub-symbol fields are the second N/2 of the sub-symbol fields.

10. The method of claim 7 , wherein:
adding the training symbol prefix to the OFDM symbol frame is configured such that each of the N/2 sub-symbols of the pseudo random training symbol is a complex value, the complex value being a mapping of a corresponding information symbol to an X-Y position in a complex plane, “X” being an in-phase component and “Y” being a quadrature component; and
transmitting the training symbol prefix as the multi-carrier transmission within the OFDM is further configured such that the signal power of each of the first N/2 of the N sub-carriers is a modulation, in amplitude and phase, of the sub-carrier N/2 corresponding to the complex value of one of the N/2 sub-symbols of the pseudo random training symbol.

11. The method of claim 7 , wherein adding the training symbol prefix to the OFDM symbol frame is configured wherein, for each of the training symbols:
a first half of the training symbol's N sub-symbol fields includes a first half of the N/2 sub-symbols of the pseudo random training symbol interleaved with a first half of the N/2 sub-symbol fields of the training symbol that are set at a zero value,
a second half of the training symbol's N sub-symbol fields includes a second half of the N/2 sub-symbols of the pseudo random training symbol interleaved with a second half of the N/2 sub-symbol fields of the training symbol that are set at a zero value,
the first half of the N/2 sub-symbols of the pseudo random training symbol that is included in first half of the training symbol's N sub-symbol fields is identical to the second half of the N/2 sub-symbols of the pseudo random training symbol that is included in second half of the training symbol's N sub-symbol fields.

12. The method of claim 11 , wherein adding the training symbol prefix to th

Assignees

• Hughes Network Systems Llc

Inventors

• Fan Donglei
• Beidas Bassel

Classifications

• H04L27/2682

  Precision · CPC title

• H04L27/2671

  Time domain · CPC title

• H04L27/2678

  using cyclostationarities, e.g. cyclic prefix or postfix · CPC title

• H04L27/2663 Primary

  Coarse synchronisation, e.g. by correlation · CPC title

• H04L27/2675

  Pilot or known symbols · CPC title