Methods and apparatus for the intelligent scrambling of control symbols

• US 10,326,624 B2
• Filed: 12/04/2017
• Issued: 06/18/2019
• Est. Priority Date: 01/27/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Whitby-Strevens, Colin
• Primary Examiner(s): Yu, Lihong
• Application Number:
  US15/831,260
• Publication Number:
  US 20180139079A1
• Time in Patent Office: 561 Days
• Field of Search: 375296
• CPC Class Codes: H03K 19/17728 Reconfigurable logic blocks, e.g. lookup tables
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 15/00 Suppression or limitation of noise or interference by means associated with receiver H04B1/10
• CPC Class Codes: H04B 2215/061 Reduction of burst noise, e.g. in TDMA systems
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 9/003 for power analysis, e.g. differential power analysis [DPA] or simple power analysis [SPA]
• CPC Class Codes: H04L 9/0656 Pseudorandom key sequence combined element-for-element with data sequence, e.g. one-time-pad [OTP] or Vernam's cipher

Abstract

Methods and apparatus for the scrambling of control symbols. In one embodiment, the control symbols are associated with an HDMI interface, and the methods and apparatus are configured to scramble the symbols to as to mitigate the effects of electromagnetic interference (EMI) created by the transmission of otherwise unscrambled sequences of symbols which may contain significant “clock pattern” or other undesirable artifact.

Claims

1. A non-transitory computer-readable medium containing a computer program which is configured to, when executed by a processor, cause the processor to:

generate a pseudo-random value;

scramble a plurality of un-encoded control symbols using the pseudo-random value; and

for each scrambled un-encoded control symbol;

select, from a data structure having a set of a plurality of scrambled control symbols each associated with the scrambled plurality of un-encoded control symbols, a scrambled control symbol configured to indicate data to be transmitted over an interface, the selection based on the scrambled un-encoded control symbol, where each scrambled control symbol of the data structure is characterized by desirable electromagnetic interference (EMI) properties; and

transmit the selected scrambled control symbol.

2. The non-transitory computer-readable medium of claim 1, where the pseudo-random value is generated via a linear feedback shift register (LFSR).

3. The non-transitory computer-readable medium of claim 2, where the pseudo-random value comprises a subset of a plurality of bits of the LFSR.

4. The non-transitory computer-readable medium of claim 3, where the subset comprises four (4) least significant bits of the LFSR output.

5. The non-transitory computer-readable medium of claim 1, where the plurality of un-encoded control symbols are further subdivided into a plurality of channels.

6. The non-transitory computer-readable medium of claim 5, where the plurality of un-encoded control symbols are further scrambled based at least in part on a channel associated with each un-encoded control symbol.

7. The non-transitory computer-readable medium of claim 1, where the processor is further configured to alternate transmissions between scrambled control symbols and non-scrambled un-encoded control symbols.

8. The non-transitory computer-readable medium of claim 1, where the data structure comprises a lookup table.

9. A method of transmitting data so as to reduce electromagnetic interference associated therewith, the method comprising:

generating a pseudo-random value;

scrambling a plurality of un-encoded control symbols using the pseudo-random value; and

for each scrambled un-encoded control symbol;

selecting, based on the scrambled un-encoded control symbol, a scrambled control symbol from a data structure, each scrambled control symbol of the data structure being characterized by desirable electromagnetic interference (EMI) properties; and

transmitting the selected scrambled control symbol.

10. The method of claim 9, wherein the generating of the pseudo-random value comprises generating the pseudo-random value via a linear feedback shift register (LFSR).

11. The method of claim 10, wherein the generating of the pseudo-random value further comprises using a subset of a plurality of bits generated by the LFSR.

12. The method of claim 11, wherein the using of the subset of the plurality of bits generated by the LFSR comprising using four (4) least significant bits of the LFSR output.

13. The method of claim 9, further comprising alternating between the transmitting of the selected scrambled control symbol and non-scrambled un-encoded control symbols.

14. The method of claim 9, wherein the selecting of the scrambled control symbol from the data structure comprises selecting the scrambled control symbol from a lookup table.

15. A user device, comprising:

a processing subsystem;

one or more ports that are in communication with the processing subsystem; and

encoding circuitry configured to;

generate a pseudo-random value;

scramble a plurality of un-encoded control symbols using the pseudo-random value; and

for each scrambled un-encoded control symbol;

select a scrambled control symbol from a data structure, the selection based on the scrambled un-encoded control symbol, where each scrambled control symbol of the data structure is characterized by desirable electromagnetic interference (EMI) properties; and

transmit the selected scrambled control symbol via the one or more ports.

16. The user device of claim 15, further comprising a linear feedback shift register (LFSR), where the pseudo-random value is generated via the LFSR.

17. The user device of claim 16, where the pseudo-random value comprises a subset of a plurality of bits of the LFSR.

18. The user device of claim 15, where the plurality of un-encoded control symbols are further subdivided into a plurality of channels.

19. The user device of claim 18, where the plurality of un-encoded control symbols are further scrambled based at least in part on a channel associated with each un-encoded control symbol.

20. The user device of claim 15, where the processing subsystem is further configured to alternate transmissions between scrambled control symbols and non-scrambled un-encoded control symbols over the one or more ports.