# US 2010/0166180 A1 · Cloaking of radio signals > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2010/0166180 A1 - Document ID: US20100166180A1 - Status: Published application - Kind: A1 - Application number: 12/346,231 - Filed: 2008-12-30 - Published: 2010-07-01 - Earliest claimed: 2008-12-30 - Assignees: Nortel Networks Limited - Inventors: David Steer; David Bevan; Simon Gale - Web page: https://patentgrep.com/patent/US20100166180A1 ## CPC - H04K 3/825: {by jamming} - H04K 3/41: {characterized by the control of the jamming activation or deactivation time (control of jamming activation and deactivation time only for the purpose of alternating between jamming mode and target monitoring mode H04K3/45)} - H04K 3/43: {characterized by the control of the jamming power, signal-to-noise ratio or geographic coverage area} - 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"} - H04K 3/42: {characterized by the control of the jamming frequency or wavelength} - H04K 3/44: {characterized by the control of the jamming waveform or modulation type} - H04K: SECRET COMMUNICATION; JAMMING OF COMMUNICATION ## Abstract The present invention comprises a device that, based upon signals transmitted by devices within a wireless network, causes masking signals to be selectively transmitted. For example, the device may not cause masking signals to be transmitted if the signal does not include confidential data, for example it is an acknowledgement message. Additionally, the strength, coding rate and modulation format of the masking signals may be varied to provide increased data security. ## Claims ### Claim 1 A method of masking a signal outside an intended coverage region of a wireless network, the signal being transmitted by a device within the wireless network, the method comprising the steps of, a) determining a property of the signal; b) determining, from the property, whether to transmit a masking signal; and c) upon determining to transmit a masking signal, transmitting a masking signal outside the intended coverage region. ### Claim 2 (depends on 1) The method as claimed in claim 1, wherein the step of determining a property of the signal comprises determining if the signal was transmitted by a device within the wireless network and the method comprises transmitting a masking signal if the device is in the wireless network. ### Claim 3 (depends on 2) The method as claimed in claim 2, wherein the step of determining if the signal was transmitted by a device in the wireless network comprises the step of determining the MAC address of a packet in the signal and comparing the determined MAC address to the MAC addresses of devices in the network. ### Claim 4 (depends on 1) The method as claimed in claim 1, wherein the step of determining a property of the signal comprises determining if the type of packet within the signal and the step of determining, from the property, whether to transmit a masking signal comprises determining whether the type of packet is to be masked. ### Claim 5 (depends on 1) The method as claimed in claim 1, wherein the step of determining a property of the signal comprises determining the strength of the signal and the step of determining if masking signal is to be transmitted comprises the step of comparing the strength of the signal to a threshold; the masking signal being transmitted if the strength of the signal is above the threshold. ### Claim 6 (depends on 1) The method as claimed in claim 1, further including the step of determining the strength of the signal and setting the strength of the masking signal to be greater than that of the signal. ### Claim 7 (depends on 1) The method as claimed in claim 1, wherein the masking signal is transmitted in a frequency range such that the frequency range of the masking signal substantially overlaps with the frequency range of the signal. ### Claim 8 (depends on 1) The method as claimed in claim 1, wherein the masking signal is transmitted for a time duration such that the time duration of the masking signal substantially overlaps with the time duration of the transmission of the signal. ### Claim 9 (depends on 8) The method as claimed in claim 8 further comprising the steps of detecting a header of a packet within the signal, determining the length of the packet from the header and causing a packet within the masking signal to have a corresponding length to the packet within the signal. ### Claim 10 (depends on 1) The method as claimed in claim 1, further including the steps of: determining the coding rate of a packet within the signal and setting the coding rate of a masking packet within the masking signal to be one of the group comprising: a lower coding rate than the coding rate of the packet; and a coding rate randomly selected from a set of coding rates. ### Claim 11 (depends on 10) The method as claimed in claim 10, further comprising the step of comparing the coding rate of the masking packet to the coding rate of the packet; and, if the coding rates of the packet and the masking packet are the same, causing the strength of the masking signal to be greater than the strength of the signal ### Claim 12 (depends on 1) The method as claimed in claim 1, further including the steps of: determining the modulation format of a packet within the signal and setting modulation format of a masking packet within the masking signal to be one of the group comprising: a lower order modulation format than the modulation format of the packet; and a modulation format randomly selected from a set of modulation formats. ### Claim 13 (depends on 12) The method as claimed in claim 12, further comprising the step of comparing the modulation format of the masking packet to the modulation format of the packet; and, if the modulation formats of the packet and the masking packet are the same, causing the strength of the masking signal to be greater than the strength of the signal. ### Claim 14 (depends on 1) The method as claimed in claim 1 further comprising causing a beacon signal advertising access to the wireless network to be transmitted. ### Claim 15 (depends on 14) The method as claimed in claim 14 further comprising the steps of receiving a response to the beacon signal and transmitting data to the sender of the response. ### Claim 16 (depends on 1) The method as claimed in claim 1 further including the steps of: determining the strength of a signal outside the intended coverage region, and setting the strength of the masking signal to be equal or greater to the determined strength of the signal. ### Claim 17 (depends on 16) The method as claimed in claim 16 further including the steps of transmitting a randomised signal as the signal and a masking signal consecutively, determining their relative strengths and, if the strength of the masking signal is less than the strength of the signal increasing the strength of the masking signal. ### Claim 18 (depends on 1) The method as claimed in claim 1 further including the steps of: determining the strength of an external signal transmitted by a device that is not in the wireless network, determining whether the strength of the external signal is above a threshold, transmitting a masking signal if the strength of the external signal is less than the threshold and not transmitting a masking signal if the strength of the masking signal is greater than the threshold. ### Claim 19 Apparatus comprising: an input to receive a representation of a signal transmitted by a device within a wireless network; a controller to determine a property of the signal and, from the property, determine whether to transmit a masking signal; and an output to cause a masking signal to be transmitted, wherein the masking signal is transmitted outside the intended coverage region of the wireless network. ### Claim 20 (depends on 19) Apparatus as claimed in claim 19 wherein the output is in communication with a directional antenna configured to transmit a masking signal outside the intended coverage region of the wireless network. ### Claim 21 A computer program embodied on a computer readable medium, the computer program configured to cause a controller to perform the steps of: a) determining a property of a signal transmitted by a device within a wireless network; b) determining, from the property, whether to transmit a masking signal; and c) upon determining to transmit a masking signal, transmitting a masking signal outside the intended coverage region of the wireless network. ### Claim 22 A calibration sensor comprising, a) an input in communication with an antenna, the antenna being configured to receive a signal transmitted by a device in a wireless network and a masking signal; and b) a controller to detect the relative strengths of the signal and the masking signal such that the strength of the masking signal is increased if the strength of the masking signal is less than the strength of the signal. ### Claim 23 (depends on 22) The calibration sensor as claimed in claim 22, wherein the controller further comprises means of decoding the data within the signal such that the strength of the masking signal is increased if the controller decodes the data within the signal. ### Claim 24 (depends on 22) The method as claimed in claim 22 wherein the calibration sensor is further configured to determine the strength of an external signal transmitted by a device that is not in the wireless network, determine whether the strength of the external signal is above a threshold such that a masking signal is transmitted if the strength of the external signal is less than the threshold and a masking signal is not transmitted if the strength of the masking signal is greater than the threshold.