Enhanced Methods of Cellular Environment Detection When Interoperating with Timed Interfers

• US 20100302956A1
• Filed: 08/10/2009
• Published: 12/02/2010
• Est. Priority Date: 08/02/2005
• Status: Active Grant

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: ComHouse Wireless LP
• Inventors: Haverty, James D.
• Granted Patent: US 8,767,595 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04K 2203/16 for telephony
• CPC Class Codes: H04K 3/22 including jamming detection and monitoring
• CPC Class Codes: H04K 3/28 with jamming and anti-jamming mechanisms both included in a same device or system, e.g. wherein anti-jamming includes prevention of undesired self-jamming resulting from jamming
• CPC Class Codes: H04K 3/45 characterized by including monitoring of the target or target signal, e.g. in reactive jammers or follower jammers for example by means of an alternation of jamming phases and monitoring phases, called "look-through mode"
• CPC Class Codes: H04K 3/65 using deceptive jamming or spoofing, e.g. transmission of false signals for premature triggering of RCIED, for forced connection or disconnection to/from a network or for generation of dummy target signal

Abstract

Techniques for performing analysis of a cellular telephone signaling environment in the presence of interferers. The techniques do the analysis by employing a receiver to listen to the cellular environment during holes in the interference. The holes have a timing which differs from that used by the cellular telephone signaling environment and will thus over time overlap with structures of interest in the cellular telephone environment. The holes may be smaller than the structure of interest. The signals which the receiver hears in the holes are analyzed and combined to reproduce the structure. The combination may involve statistical methods and weighted decoding. The analysis obtains information which permits surgical attacks on individual wireless devices which are in the traffic state. Example applications of the techniques are given for the GSM and CDMA cellular telephone standards.

Claims

1. A method of obtaining information about a repeated structure in a signal which is generated according to a standard and which represents a sequence of symbols, the repeated structure having a first timing in the signal and the method being performed in apparatus including a receiver and a signal analyzer and comprising the steps performed in the apparatus of:

receiving the signal for a set of discrete periods in the receiver, the periods in the set having a second timing such that over a plurality of repetitions of the repeated structure in the signal, the entire repeated structure is received in the receiver;

converting the signal as received in each of the discrete periods in the set into symbols; and

analyzing the symbols in the analyzer to obtain the information about the repeated structure.

2. The method set forth in claim 1 wherein:

the set of discrete periods is made up of periods during which the signal is not being interfered with by an interferer.

3. The method set forth in claim 2 further comprising the step performed in the receiver of:

determining the set of discrete periods from the interferer'"'"'s behavior.

4. The method set forth in claim 2 wherein:

the apparatus is operating in cooperation with the interferer.

5. The method set forth in claim 4 wherein the method further comprises the step of:

providing the obtained information about the repeated structure to the interferer.

6. The method set forth in claim 4 wherein the method further comprises the step of

obtaining a specification of the set of discrete periods from the cooperating interferer.

7. The method set forth in claim 4 wherein:

the receiver determines the set of discrete periods during which the cooperating interferer does not interfere with the signal.

8. The method set forth in claim 7 wherein:

the receiver determines the set of discrete periods according to the kind of information to be obtained and/or the speed with which the information is to be obtained.

9. The method set forth in claim 1 wherein:

in the analyzing, the symbols from a plurality of the discrete periods are combined using a statistical method.

10. The method set forth in claim 1 wherein

the repeated structure is a frame which includes another repeated structure which contains timing information about the frame;

and the method includes the steps performed in the analyzer of

obtaining the timing information from the second repeated structure in the set of digital representations; and

using the timing information to determine a location of a further repeated structure in the frame.

11. The method set forth in claim 10 wherein the method includes the steps performed in the analyzer of:

using the determined location to locate a representation of the further structure in the set of digital representations; and

obtaining further information about the frame from the located representation.

12. The method set forth in claim 1 wherein:

the repeated structure is a frame which has a substructure;

a discrete period in the set thereof is too short to receive a portion of the signal that contains an entire substructure.

13. The method set forth in claim 12 wherein:

in the step of analyzing, a plurality of the discrete periods that contain portions of the substructure are combined using a statistical method.

14. The method set forth in claim 13 wherein:

in the step of analyzing, the symbols are further combined using soft decoding techniques which employ results of the statistical method.

15. The method set forth in claim 12 wherein

the substructure includes an error detection code;

and

the method further includes the step of;

using the substructure'"'"'s error detection code to determine whether a result of the combination is correct.

16. The method set forth in claim 15 wherein:

the error detection code includes error correction information; and

the method further includes the step of;

using the error correction information to reduce the number of possible combinations of the symbols.

17. A method of obtaining information from a GSM beacon using apparatus including a receiver and a signal analyzer, the receiver having access to a set of the beacon'"'"'s GSM bursts for discrete periods, the discrete periods having a timing relative to the GSM burst such that the discrete periods eventually include a subset thereof which together overlap an entire GSM burst and

the method comprising the steps performed in the apparatus of:

in the receiver,

accessing the forward cellular band during the discrete periods and in the analyzer,

identifying the beacon from the beacon'"'"'s GMSK modulation characteristics;

identifying a subset of the discrete periods that overlaps an SCH burst of the beacon'"'"'s GSM bursts;

using information from the subset that overlaps the beacon'"'"'s SCH burst to acquire a timing for another kind of GSM burst belonging to the beacon;

identifying a further subset of the discrete periods that overlaps the other kind of bursts; and

obtaining the information from the further subset which overlaps the other kind of bursts.

18. A method of obtaining information from a CDMA beacon belonging to a CDMA frequency channel using apparatus including a receiver and a signal analyzer, the receiver having access to a set of the beacon'"'"'s pilots for discrete periods, the discrete periods and the CDMA beacon both being locked to GPS and the discrete periods having a timing relative to the CDMA beacon such that the discrete periods eventually include a subset thereof which together overlap the pilot PN offset fields for the pilots and

the method comprising the steps performed in the apparatus of:

in the receiver,

accessing the forward cellular band during the discrete periods and

in the analyzer,

determining whether a particular pilot PN offset field overlapped by a subset of the discrete fields field is in use; and

if the particular pilot offset field does contain a pilot PN offset number, using correlation with other subsets of the discrete fields that overlap the pilot PN offset number to determine the pilot PN offset number.

19. A receiver which is employed to listen to a target signal which is hidden by another signal which is much stronger than the target signal, the target signal being hidden except during a discrete interval, timing of the discrete interval'"'"'s beginning being known to the receiver and the receiver having the improvement comprising:

an automatic gain control which has a rapid rise time and a decay time which is much longer than the rise time, the receiver resetting the automatic gain control according to the timing of the discrete interval'"'"'s beginning.

20. A method of using a baiting beacon to interrogate a wireless device in a cellular environment which is being interfered with by an interfering signal, the interfering signal ceasing during discrete intervals that are known to the baiting beacon, signals of the baiting beacon being subject to interference by a reactive interferer during the discrete intervals, and

the method comprising the steps performed by the baiting beacon of:

selecting a feature of the signal which will cause the wireless device to respond to the baiting beacon in spite of the interference and which does not require that the beacon signal during the discrete intervals; and

interacting with the wireless device at times other than during the discrete intervals using the feature.