Methods and apparatus for the intelligent scrambling of control symbols

• US 9,838,226 B2
• Filed: 01/22/2013
• Issued: 12/05/2017
• 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:
  US13/747,264
• Publication Number:
  US 20130195218A1
• Time in Patent Office: 1,778 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 method of transmitting data so as to reduce electromagnetic interference associated therewith, the method comprising:

receiving a plurality of un-encoded control symbols and a plurality of data symbols;

generating one or more pseudo-random values based on a transmitting linear feedback shift register (LFSR); and

scrambling only the plurality of un-encoded control symbols, the plurality of un-encoded control symbols being scrambled with the generated one or more pseudo-random values in order to produce a plurality of corresponding pseudo-random values, where a plurality of scrambled corresponding control symbols are retrieved from a lookup table based on the plurality of corresponding pseudo-random values generated using the scrambling;

wherein;

transmitting of the plurality of scrambled corresponding control symbols minimizes undesirable electromagnetic radiation and interference;

the receiving LFSR comprises a self-synchronizing LFSR; and

the receiving LFSR is forced to a known value to self-synchronize, the known value comprising a channel number selected from a plurality of channel numbers.

2. The method of transmitting data of claim 1, wherein the plurality of un-encoded control symbols is associated with a High-Definition Multimedia Interface (HDMI) interface.

3. The method of claim 1, further comprising using a sub-set of bits generated by the transmitting LFSR, the sub-set of bits being used to generate the one or more pseudo-random values.

4. The method of claim 3, wherein the using of the sub-set of bits comprises using a set of least significant bits to generate the plurality of pseudo-random values.

5. The method of claim 3, wherein the using of the sub-set of bits comprises using a set of most significant bits to generate the plurality of pseudo-random values.

6. The method of claim 1, wherein the transmitting of the plurality of scrambled corresponding control symbols further comprises transmitting the plurality of scrambled corresponding control symbols when the transmitting LFSR and the receiving LFSR are synchronized.

7. The method of claim 1, further comprising updating a running disparity count after each one of the plurality of scrambled corresponding control symbols is transmitted.

8. The method of claim 7, further comprising using the running disparity count for the retrieving of the plurality of scrambled corresponding control symbols.

9. The method of claim 1, further comprising padding the generated one or more pseudo-random values with one or more additional bits.

10. The method of claim 9, further comprising generating an index value for use with the lookup table by exclusive OR′

ing the padded one or more pseudo-random values with the generated one or more pseudo-random values.

11. An apparatus, the apparatus comprising:

a transmitting linear feedback shift register (LFSR); and

an electronic circuit configured to;

receive a plurality of un-encoded control symbols and a plurality of data symbols;

generate one or more pseudo-random values based on the transmitting LFSR; and

scramble only the plurality of un-encoded control symbols, the plurality of un-encoded control symbols being scrambled with the generated one or more pseudo-random values in order to produce a plurality of corresponding pseudo-random values, where a plurality of scrambled corresponding control symbols are retrieved from a lookup table based on the plurality of corresponding pseudo-random values generated using the scrambling;

wherein;

transmission of the plurality of scrambled corresponding control symbols minimizes undesirable electromagnetic radiation and interference;

the receiving LFSR comprises a self-synchronizing LFSR; and

the receiving LFSR is forced to a known value to self-synchronize, the known value comprising a channel number selected from a plurality of channel numbers.

12. The apparatus of claim 11, wherein the plurality of un-encoded control symbols are associated with a High-Definition Multimedia Interface (HDMI) interface.

13. The apparatus of claim 12, wherein the electronic circuit is further configured to use a sub-set of bits generated by the transmitting LFSR, the sub-set of bits being used to generate the one or more pseudo-random values.

14. The apparatus of claim 13, wherein the use of the sub-set of bits further comprises use of a set of least significant bits to generate the plurality of pseudo-random values.

15. The apparatus of claim 13, wherein the use of the sub-set of bits further comprises use of a set of most significant bits to generate the plurality of pseudo-random values.

16. The apparatus of claim 11, wherein the transmission of the plurality of scrambled corresponding control symbols further comprises transmission of the plurality of scrambled corresponding control symbols when the transmitting LFSR and the receiving LFSR are synchronized.

17. The apparatus of claim 11, wherein the electronic circuit is further configured to update a running disparity count after each one of the plurality of scrambled corresponding control symbols is transmitted.

18. The apparatus of claim 17, wherein the running disparity count is utilized for the retrieval of the plurality of scrambled corresponding control symbols.

19. The apparatus of claim 11, wherein the electronic circuit is further configured to pad the generated one or more pseudo-random values with one or more additional bits.

20. The apparatus of claim 19, wherein the electronic circuit is further configured to generate an index value for use with the lookup table via an exclusive OR operation of the padded one or more pseudo-random values with the generated one or more pseudo-random values.