Secure pilot allocation for integrated sensing and communication

Abstract

This invention relates to a method for allocation of the secure pilots for integrated sensing and communication against potential security threats.

Description

[0001] SECURE PILOT ALLOCATION FOR INTEGRATED SENSING AND COMMUNICATION

[0002] Technical Field

[0003] This invention relates to a method for allocation of the secure pilots for integrated sensing and communication against potential security threats.

[0004] Prior Art

[0005] In integrated sensing and communication, most of the sensing parameters are extracted from the channel state information (CSI). To make the CSI available for communication and sensing, known pilot symbols with known locations in the time-frequency plane are transmitted. However, if the malicious node knows the pilot location, it can either extract the sensing information or contaminate the pilots to disrupt the communication. To secure sensing and communication, the location of pilots must be secured in a way that can be only identified by the legitimate user.

[0006] At present, there are only a few approaches based on pilot manipulation to provide physical layer security. The work by Wei, H., et al, published in 2013 at 22ndWireless and Optical Communication Conference proposes a mechanism for the random pilot allocation based on codebook to hide the pilots’ locations from the malicious node. Initially, the random pilot codebook is generated from the measurement matrix of the compressive channel sensing (i.e., partial Fourier transform matrix). Additionally, the authors propose an instantaneous CSLbased key generation mechanism to encrypt the random pilot codebook. In a publication by Soltani, M., et al, published in 2015 the pilot symbols manipulation approach based on the CSI shared between the legitimate nodes is proposed to provide secure communication. Two approaches are followed for the pilot manipulation; phase-based and amplitude-based. In the phase-based approach, the phase of the instantaneous channel is compared with a selected threshold to manipulate the pilot symbols. On the other hand, the estimated amplitude of the channel is compared with the selected threshold for pilot manipulation.

[0007] The approach proposed in the work by Wei, H., et al, mentioned above requires, the random pilot codebook generation at the beginning for pilot allocation, which needs to be shared between both legitimate nodes. Besides, the random pilot codebook has a limited number of patterns that can be estimated through extensive simulations.

[0008] However, in the pilot symbol manipulation approach given in Soltani, M., et al, the illegitimate node can detect the pilots through correlation as the locations of the pilots are known to everyone. The current state of the art shows that there is a need for new methods for providing secure transmission for joint sensing and communication applications.

[0009] Aim of the Invention

[0010] For wireless communication, the signal in the environment can be utilized to detect the data and sensing information. For instance, the transmitted data can be decoded by an eavesdropper if not encrypted. Even encrypted, it can decode the data with high computational processing capabilities if some of the signal information is known e.g., pilots. Moreover, the signal in the environment can be used to detect range, velocity, angle of transmitter and receiver as sensing information.

[0011] Therefore, the purpose of the invention is to provide security for data and sensing information jointly by hiding the pilot subcarriers’ locations at the transmitter based on the channel state information between the transmitter and receiver.

[0012] Brief Description of the Invention

[0013] Present invention relates to a method for protecting integrated sensing and communication against potential security threats wherein said method comprises the steps of;

[0014] Allocation of the adaptive pilot based on the channel state information of the user whose communication is to be secured, Allocation of the adaptive power to reduce the pilot location identification error by increasing the gap between the signal power at the transmitter and the receiver of the aforementioned user, and

[0015] Identification of the pilot location from the average power of the received signal at the user.

[0016] In this invention, instead of generating a random pilot codebook or manipulation of pilot symbols as described in the prior art, we propose a method to secure pilot location with adaptive pilot allocation based on the instantaneous channel between the legitimate nodes to provide security. Through the method of the invention, only the legitimate nodes can identify the location of the pilots to perform sensing and communication. Furthermore, an adaptive power allocation mechanism is proposed to reduce the pilot location identification error rate at the receiving node. In another aspect, the invention provides secure transmission for joint sensing and communication information without a common knowledge between transmitter and receiver.

[0017] The main advantage of the invention is to provide secure transmission of pilots for integrated sensing and communication. For this purpose, the pilots are manipulated at the transmitter based on the channel state information between the transmitter and receiver. Different from the channel, the receiver does not know the pilot locations and the channel state information. At the receiver, firstly, the invention detects the pilot locations from the averaged signal power of the received signal. After the pilot subcarrier location is detected, the channel is estimated from the detected pilot subcarriers. Since the different links have different fading characteristics, the pilot subcarrier locations can not be detected.

[0018] Explanation of Figures

[0019] Figure 1: A block diagram illustrating the wireless communication system according to an embodiment of the present invention

[0020] 110: a legitimate transmitter

[0021] 120: a legitimate receiver

[0022] 130: eavesdropper 140A: Wireless link from 120 to 110

[0023] 140B: Wireless link from 120 to 130

[0024] 150A: Wireless link from 110 to 120

[0025] 150B: Wireless link from 110 to 130

[0026] Figure 2: the flow diagram of the basic operations for secure integrated sensing and communication in accordance with certain aspects of the present invention

[0027] 210: Apply adaptive pilot allocation mechanism at 110 to allocate the pilots based on channel state information received from 120.

[0028] 220: Apply adaptive power allocation mechanism at 110 to reduce the pilot location identification error at 120.

[0029] 230: Apply pilot location identification mechanism at 120 to detect the locations of pilots.

[0030] Figure 3: flow chart illustrating the adaptive pilot allocation mechanism that is applied at 110 for securing pilots’ locations for pilot allocation.

[0031] 301: start of the flow chart.

[0032] 302: initialization of parameters including NPC, STNsc, NTS, NSG, NTP, LPG. NPCrepresents channel bandwidth, Nscrepresents the number of subchannels, NTSrepresents the total subcarriers in the transmit signal at 110, STrepresents a total number of subgroups, NSGdenotes the total subcarriers in a subgroup, NTPdenotes the possible positions for the pilot subcarriers in a subgroup, and LPGdenotes the location of pilot subcarrier within NTP.

[0033] 303: Defines the threshold value THbased on the average power of the channel

[0034] 304: divide NPCinto Nscsubchannels

[0035] 305: interleave subchannels to reduce the correlation between the neighboring subchannels so 130 may not estimate the channel through correlation. 306: Divide NTSinto subgroups each having NSGsubcarriers and multiplying with the power of the corresponding subchannel.

[0036] 307: Calculate average power of each subgroup PSG.

[0037] 308: check if i <= ST? is true 309 (i.e., pilots locations are not decided in all subgroups), go to step 311. Otherwise, if the statement is false 310 (i.e., pilot locations have been decided in all subgroups), go to step 315, where i denotes the ith subgroup of subcarriers in the transmit signal atl lO

[0038] 309: True

[0039] 310: False

[0040] 311: compare PSGwith TH, if PSG(i) < TH? is true 309 (i.e., PSGof ith subgroup is less than TH), go to step 312. Otherwise, if PsG(i) < TH? is false 310 (i.e., PSGof ith subgroup is greater than TH), go to step 313.

[0041] 312: allocate the subcarrier on the position a in subgroup to pilot symbol (i.e., LPG(i) = a)

[0042] 313: allocate the subcarrier on the position b in subgroup to pilot symbol (i.e., LPG(i) = b)

[0043] 314: i = i + 1, increment in i by 1 (i.e., count the subgroup for which the pilot location has been decided) and go to step 308 i: The variable to count the iteration for a loop

[0044] 315: place pilot and data symbols on the pilot and data subcarriers, respectively

[0045] 316: End the flow chart

[0046] Figure 4: a plot illustrating the signal generated at the transmitter.

[0047] Figure 5: Pictorial representation of the adaptive power algorithm at 110

[0048] 511: Power 512: Frequency

[0049] 513: Channel frequency response

[0050] 514: Subchannels

[0051] 515: channel bandwidth

[0052] 516: total number of subcarriers

[0053] 517: number of subcarriers in a subgroup

[0054] 518: average power of a subgroup

[0055] 519: threshold value TH

[0056] 520: possible pilotlocations

[0057] 521: pilot subcarrier carrying pilot symbol

[0058] 522: data subcarriers carrying data symbols

[0059] 530: channel frequency response 513 with channel bandwidth 515

[0060] 540: channel interleaving phenomenon to reduce the correlation between neighboring subchannels

[0061] 550: subgroups of the subcarriers in transmit signal

[0062] 560: subcarriers in a subgroup after multiplication with the channel

[0063] 570: NTSwith pilot symbols 521 and data symbols 522 in each subgroup

[0064] Figure 6: a plot illustrating the adaptive power allocation mechanism which is disclosed in the invention to maintain a power gap PGbetween THand the power of the transmit signal at 110 and power of the receive signal at 120.

[0065] Figure7: a flowchart illustrating the flow chart of adaptive power allocation 220 at 110. 307: Step 307 in Figure 3

[0066] 308: Step 308 in Figure 3

[0067] 701: step that defines the the power gap PG, the average power of the received signal PRS= PTSX CSI at 120.

[0068] 702: check if TH— PG< PRS< TH?

[0069] 703: True

[0070] 704: decrease PRsby

[0071] 705: False

[0072] 706: check if TH< PRS< TH+ PG?

[0073] 707: increase PRsby

[0074] Figure 8: A flow chart illustrating the of pilot location identification mechanism at 120 from the received signal.

[0075] 801: start flow chart

[0076] 802: intializes parameters NTS, SR, NSG, NTP, LPG, where NTSrepresents the total subcarriers in the signal transmitted by 110, SRrepresents the total number of subgroups of the subcarriers in the received signal at 120, NSGdenots the total subcarriers in a subgroup, NTPdenotes the possible locations for pilot subcarriers in a subgroup, and LPGdenotes the location of pilot subcarrier within NTP.

[0077] 803: find the threshold THfrom the average power of the received signal at 120.

[0078] 804: divide NTSinto SR.

[0079] 805: calculate the average power of each subgroup PSG

[0080] 806: check if j <= SR? 807: True

[0081] 808: False

[0082] 809: compare PSGwith TH, if PSG(j) < TH7

[0083] 810: allocate the subcarrier on the position a in subgroup to pilot symbol (i.e., LpG(j) = a)

[0084] 811: allocate the subcarrier on the position b in subgroup to pilot symbol (i.e., LPG(j) = b)

[0085] 812: j = j + 1, increment in j by 1 (i.e., count the subgroup for which the pilot location has been detected)

[0086] 813: Detect the pilot and data symbols from the pilot and data subcarriers, respectively

[0087] 814: end flow chart

[0088] Detailed Description of the Invention

[0089] As mentioned above, present invention relates to a method for integrated sensing and communication against potential security threats wherein said method comprises the steps of;

[0090] Allocation of the adaptive pilot based on the channel state information (CSI) of the user whose communication is to be secured (210),

[0091] Allocation of the adaptive power to increase the gap between the signal power at the transmitter and the receiver of the aforementioned user (220), and

[0092] Identification of the pilot location from the received signal at the user (230).

[0093] In step 210, a legitimate receiver (120) transmits the pilots’ subcarriers to a legitimate transmitter (110) for the estimation of channel state information (CSI).

[0094] In step 220, legitimate transmitter (110) allocates pilot and data subcarriers in the transmission signal according to the adaptive pilot allocation mechanism 210 and performs the adaptive power allocation.

[0095] In step 230, The signal is transmitted to a legitimate receiver (120) on the wireless channel 150A. At the legitimate receiver (120), firstly the average power of the received signal is measured and then pilots are obtained using the pilot location identification mechanism 230 to perform the channel estimation.

[0096] In an aspect, step 210 wherein adaptive pilot allocation is applied at legitimate transmitter (110) for securing pilot location comprises;

[0097] • initialization of parameters including NPC, Nsc, NTS, NSG, NTP, LPG, NPCchannel bandwidth (302)

[0098] • defining the treshold value THbased on the average power of the channel (303),

[0099] • dividing NPCinto Nscsubchannels (304),

[0100] • interleaving of the subchannels to reduce the correlation between the neighboring subchannels so an eavesdropper (130) will not estimate the channel through correlation (305),

[0101] • Dividing NTSinto subgroups each having NSGsubcarriers and multiplying with the power of the corresponding subchannel (306),

[0102] • calculating average power of each subgroup (307),

[0103] • if i <= STis false (310), e.g. pilot locations are decided in all subgroups, place pilot and data symbols on the pilot and data subcarriers, respectively (315),

[0104] • if i <= STis true (309), e.g. pilots locations are not decided in all subgroups, compare PSGwith TH(311),

[0105] • if PSG(i) < TH? is true (309), e.g. PSGof ith subgroup is less than TH, allocate the subcarrier on the position a in subgroup to pilot symbol, e.g., LPG(i) = a (312)

[0106] • if PSG(i) < TH? is false (310), PSGof ith subgroup is greater than TH, allocate the subcarrier on the position b in subgroup to pilot symbol (i.e., LPG(i) = b) (313);

[0107] • i = i + 1, increment in i by 1 (i.e., count the subgroup for which the pilot location has been decided) (314)

[0108] • place pilot and data symbols on the pilot and data subcarriers, respectively (315)

[0109] Herein NPCrepresents channel bandwidth, Nscrepresents the total number of subchannels, NTSrepresents the total subcarriers in the transmit signal at 110, STrepresents the total number of a subgroups, NSGdenotes the total subcarriers in a subgroup, NTPdenotes the possible positions for the pilot subcarriers in a subgroup, and LPGdenotes the location of pilot subcarrier within NTP

[0110] In an aspect, step 220 wherein, adaptive power allocation is applied at legitimate transmitter (110) comprises;

[0111] • defining the the power gap PG, and the average power of the received signal PRS= PTSX CSI at (120), the legitimate receiver (701),

[0112] • Comparing if TH- PG< PRS< TH

[0113] • If true (703), decrease PRsby (704) and complete adaptive pilot allocation mechanism (210) steps from (308) to (315),

[0114] • If false (705), check if TH< PRS< TH+ PG(706) if true (703) then increase the PRsby (707) and complete adaptive pilot allocation mechanism (210) steps from (308) to (315),

[0115] • if TH< PRS< TH+ PG(706) do not change PRsthen complete adaptive pilot allocation mechanism (210) steps from (308) to (315).

[0116] The step 220 adaptive power allocation is applied at legitimate receiver (110) starts after calculating average power of each subgroup PSG(307).

[0117] In an aspect, step 230 wherein identification of the pilot location from the received signal at the user is carried out comprises;

[0118] • Intializing parameters NTS, SR, NSG, NTP, LPG(802)

[0119] • Determination of the threshold THby the legitimate transceiver (120) from the average power of the received signal (803)

[0120] • dividing the received signal’s subcarriers NTSinto SR(804),

[0121] • Calculating the average power of a subgroup PSG(805),

[0122] • Checking if j <= ST(806), if false (808) move to step (813) where j denotes the jth subgroup • if j <= ST(806) is true (807) then compare PSGwith TH, if PsG(j) < THif true (807), e.g. PSGof J th subgroup is less than TH, then allocate the subcarrier on the position a in subgroup to pilot symbol (i.e., LPG(j) = a) (810),

[0123] • if at comparison of PSGwith TH, PsG(j) < TH is false (808), e.g. PSGof jth subgroup is greater than TH, allocate the subcarrier on the position b in subgroup to pilot symbol (i.e., LPG(j) = b) (811),

[0124] • j = j + 1, increment in j by 1 (i.e., count the subgroup for which the pilot location has been detected) (812)

[0125] • Detect pilot and data symbols from the pilot and data subcarriers, respectively (813).

[0126] Herein, NTSrepresents the total subcarriers in the signal transmitted by 110, SRrepresents the total number of a subgroup of the subcarriers in the received signal at 120, NSGdenotes the total subcarriers in a subgroup, NTPdenotes the possible locations for pilot subcarriers in a subgroup, and LPGdenotes the location of the pilot subcarrier within NTP

[0127] Industrial Applicability of the Invention

[0128] With new wireless standards of 3GPP and IEEE organizations such as 5G and IEEE 802.11be, the sensing requirement becomes very critical, especially for newly emerged applications such as autonomous vehicles, virtual reality, mission-critical autonomous robots, etc.

[0129] The invention is a method to protect wireless communication and sensing signals from being overheard / intercepted by malicious eavesdroppers. As such, it is applicable to industry which is interested in security of the communication.

[0130] With the sensing requirement, the physical layer security of integrated sensing and communication for new applications can be met by the invention. The invention provides secure transmission by adjusting pilot subcarriers’ location based on the channel state information of the receiver. Around these basic concepts, it is possible to develop several embodiments regarding the subject matter of the invention; therefore, the invention cannot be limited to the examples disclosed herein, and the invention is essentially as defined in the claims.

[0131] It is obvious that a person skilled in the art can convey the novelty of the invention using similar embodiments and / or that such embodiments can be applied to other fields similar to those used in the related art. Therefore, it is also obvious that these kinds of embodiments are void of the novelty criteria and the criteria of exceeding the known state of the art.

[0132] Detailed explanation of the figures:

[0133] Figure 1 is a block diagram illustrating the wireless communication system according to the embodiment of the present invention, which includes three nodes 110, 120, and 130. 110 may be a legitimate transmitter and / or a legitimate receiver that may receive pilot subcarriers from the legitimate receiver 120 through the wireless channel 140A, and may transmit the data and / or pilot subcarriers through the wireless channel 150A. 130 is an eavesdropper that may want to detect the sensing information and / or may want to listen to the communication between 110 and 120 through wireless links 140B and / or 150B. The wireless channels 140A and 150A follow the reciprocity property, which means they may have similar channel gains. Besides, the wireless channels 140B and 150B are different from 140A and 150A, respectively.

[0134] Figure 2 shows the flow diagram of the basic operations for secure integrated sensing and communication in accordance with certain aspects of the present disclosure. Firstly, 120 transmits the pilots’ subcarriers to 110 for the estimation of channel state information (CSI). After obtaining CSI, 110 allocates pilot and data subcarriers in the transmission signal according to the adaptive pilot allocation mechanism 210 and performs the adaptive power allocation 220. The signal is transmitted to 120 on the wireless channel 150 A. At 120, firstly the average power of the received signal is measured and then pilots are obtained using the pilot location identification mechanism 230 to perform the channel estimation.

[0135] Figure 3 is a flow chart illustrating the adaptive pilot allocation mechanism that is applied at 110 for securing pilot location. Step 301 presents the start of the adaptive pilot allocation mechanism flow chart to secure the pilot locations 110.

[0136] Step 302 presents the initialization of parameters including NPC, ST, Nsc, NTS, NSG, NTP, LPG. NPCchannel bandwidth, Nscrepresents the total number of subchannels, NTSrepresents the total subcarriers in the transmit signal at 110, STrepresents the total number of a subgroups, NSGdenotes the total subcarriers in a subgroup, NTPdenotes the possible positions for the pilot subcarriers in a subgroup, and LPGdenotes the location of pilot subcarrier within NTP.

[0137] Step 303, Define the threshold value THbased on the average power of the channel

[0138] Step 304, NPGis divided into Nscsubchannels.

[0139] Step 305 presents the interleaving of the subchannels to reduce the correlation between the neighboring subchannels so 130 may not estimate the channel through correlation.

[0140] Step 306, Divide NTSinto subgroups each having NSGsubcarriers and multiplying with the power of the corresponding subchannel.

[0141] Step 307, calculates average power of each subgroup PSG.

[0142] Step 308 check if i <= ST? if the statement is true 309 (i. e. , pilots locations are not decided in all subgroups), go to step 311. Otherwise, if the statement is false 310 (i.e., pilot locations are decided in all subgroups), move to step 315, where i denotes the ith subgroup of subcarriers in the transmit signal of 110.

[0143] 309: True

[0144] 310: False

[0145] Step 311, compare PSGwith TH, if Psc(i) < TH? is true 309 (i.e., PSGof ith subgroup is less than TH), allocate the subcarrier on the position a in subgroup to pilot symbol (i.e., LPG(i) = a) at step 312. Otherwise, if PsG (i) < TH? is false 310 (i.e., PSGof ith subgroup is greater than TH), allocate the subcarrier on the position b in subgroup to pilot symbol (i.e., LPG(i) = b) at step 313. 312: allocate the subcarrier on the position a in subgroup to pilot symbol (i.e., LPG(i) = a)

[0146] 313: allocate the subcarrier on the position b in subgroup to pilot symbol (i.e., LPG(i) = b)

[0147] Step 314, i = i + 1, increment in i by 1 (i.e., count the subgroup for which the pilot location has been decided)

[0148] Step 315, place pilot and data symbols on the pilot and data subcarriers, respectively.

[0149] Step 316, End the flow chart.

[0150] Figure 4 is a plot illustrating the power of the time domain signal generated at 110. The THrepresents the threshold values calculated by taking the average power of the signal.

[0151] Figure 5 is a pictorial representation of the adaptive power algorithm at 110.

[0152] 530 presents channel frequency response 513 with NPCchannel bandwidth in power 511 and frequency 512. The channel is divided into subchannels 514, where the subcarriers in each subchannel have a flat frequency response.

[0153] 540 presents the channel interleaving phenomenon to reduce the correlation between neighboring subchannels. Firstly, the subchannels are divided into groups of four for example and then the subcannels of each group are interleaved starting from the first subchannel in a sequence.

[0154] 550 presents transmit signal in frequency. There signal consists of NTS516 subcarriers divided into subgroups with each having NSG517 subcarriers.

[0155] 560 presents the pilot and data subcarriers in each subgroup aftert multiplication with the channel, the average power of the subcarriers in a subgroup 518 and the threshold value TH519. Out of NSGsubcarriers, there are NTPpossible pilot positions 520 and the pilot symbol is placed on the subcarrier 521.

[0156] 570 presents NTSwith pilot subcarriers carrying pilot symbols 521 and data subcarriers carrying data symbols 522 in each subgroup. Figure 6 is a plot illustrating the transmit and receive signal with the adaptive power allocation mechanism, which is disclosed in the invention to maintain a power gap PGbetween THand the power of the transmit signal at 110 and power of the receive signal at 120. This power gap PGis necessary for successful pilot location identification at 120. When the gap between THand powers of transmit signal by 110 and received signal by 120 is less than the defined power gap PG, the pilot location identification results in an error. Thus, leading to the wrong estimation of the channel at 120.

[0157] Figure 7 is a flowchart illustrating the algorithm of adaptive power allocation 220 at 110. This method starts after step 307 of adaptive pilot allocation mechanism 210.

[0158] Step 701 defines the the power gap PG, and the average power of the received signal PRS= PTSX CSI at 120.

[0159] Step 702 compares if TH— PG< PRS< TH? if the statement is true 703, then decrease PRsby 704 and complete adaptive pilot allocation mechanism 210 from Step 308 to end. Otherwise, if the statement is false 705, check if TH< PRS< TH+ PG? 706 is true 703, then increase the PRsby 707 and complete adaptive pilot allocation mechanism 210 from Step 308 to end. Otherwise, if TH< PRS< TH+ PG? do not change PRsthe complete adaptive pilot allocation mechanism 210 from Step 308 to end.

[0160] Figure 8 is a flow chart illustrating the of pilot location identification mechanism at 120 from the received signal.

[0161] Step 801 presents the start of the flow chart

[0162] Step 802 intializes parameters NTS, SR, NSG, NTP, LPG, where NTSrepresents the total subcarriers in the signal transmitted by 110, SRrepresents the total number of a subgroup of the subcarriers in the received signal at 120, NSGdenotes the total subcarriers in a subgroup, NTPdenotes the possible locations for pilot subcarriers in a subgroup, and LPGdenotes the location of the pilot subcarrier within NTP.

[0163] Step 803, 120 finds the threshold THfrom the average power of the received signal. Step 804, divide the received signal’s subcarriers NTSinto SR.

[0164] Step 805, calculate the average power of a subgroup PSG.

[0165] Step 806, check if j <= SR? If the statement is true 807 move to step 809. Otherwise if statement is false 808 move to step 814, where j denotes the jth subgroup.

[0166] Step 809, compare PSGwith TH, if Psc;(j) < TH? is ture 807 (i.e., PSGof jth subgroup is less than TH), allocate the subcarrier on the position a in subgroup to pilot symbol (i.e., LPG(j) = a) at step 810. Otherwise, if Psc, (j) < TH? is false 808 (i.e., PSGof jth subgroup is greater than Tn), allocate the subcarrier on the position b in subgroup to pilot symbol (i.e., LPG(J) = b) at Step 811.

[0167] Step 812, j = j + 1, increment in j by 1 (i.e., count the subgroup for which the pilot location has been detected)

[0168] Step 813, Detect pilot and data symbols from the pilot and data subcarriers, respectively

[0169] Step 814, End.

Claims

CLAIMS1. A method for protecting integrated sensing and communication against potential security threats wherein said method comprises the steps of;• Allocation of the adaptive pilot based on the channel state information (CSI) of the user whose communication is to be secured (210),• Allocation of the adaptive power to reduce the pilot location identification error by increasing the gap between the signal power at the transmitter and the receiver of the aforementioned user (220),• Identification of the pilot location from the average power of received signal at the user (230)2. A method according to claim 1 characterized in that in step 210 a legitimate receiver (120) transmits the pilots’ subcarriers to a legitimate transmitter (110) for the estimation of channel state information (CSI).

3. A method according to claim 1 or 2 characterized in that, in step 220 legitimate transmitter (110) allocates pilot and data subcarriers in the transmission signal according to the adaptive pilot allocation mechanism 210 and performs the adaptive power allocation.

4. A method according to any one of claims 1-3 characterized in that, in step 230 the signal is transmitted to a legitimate receiver (120) on the wireless channel 150 A and at the legitimate receiver firstly the average power of the received signal is measured and then pilots are obtained using the pilot location identification mechanism to perform the channel estimation.

5. A method according to any one of the preceding claims characterized in that step 210 wherein adaptive pilot allocation is applied at legitimate transmitter (110) for securing pilot location comprises; o initialization of parameters including NPC, ST,NSC, NTS, NSG, NTP, LPG, NPCchannel bandwidth (302) o defining the treshold value THbased on the average power of the channel (303), o dividing NPCinto Nscsubchannels (304),o interleaving of the subchannels to reduce the correlation between the neighboring subchannels so an eavesdropper (130) will not estimate the channel through correlation (305), o Dividing NTSinto subgroups each having NSGsubcarriers and multiplying with the power of the corresponding subchannel (306), o calculating average power of each subgroup (307), o if i <= STis false (310), i.e., pilot locations have been decided in all subgroups, place pilot and data symbols on the pilot and data subcarriers, respectively (315), o if i <= STis true (309), i.e., pilots locations are not decided in all subgroups, compare PSGwith TH(311), o if PSG(i) < TH? is true (309), e.g. PSGof ith subgroup is less than TH, allocate the subcarrier on the position a in subgroup to pilot symbol, e.g., LPG(i) = a (312) o if PSG(i) < TH? is false (310), PSGof ith subgroup is greater than TH, allocate the subcarrier on the position b in subgroup to pilot symbol (i.e., LPG(i) = b) (313); o i = i + 1, increment in i by 1 for example count the subgroup for which the pilot location has been decided (314) o place pilot and data symbols on the pilot and data subcarriers, respectively (315). A method according to any one of the preceeding claims characterized in that step 220 wherein, adaptive power allocation is applied at legitimate transmitter (110) comprises;• defining the the power gap PG, and the average power of the received signal PRS= PTSX CSI at (120), the legitimate receiver (701),• Comparing if TH- PG< PRS< TH(702)• If true (703), decrease PRsby (704) and complete adaptive pilot allocationmechanism (210) steps from (308) to (315),• If false (705), check if TH< PRS< TH+ PG(706) if true (703) then increase the PRsby (707) and complete adaptive pilot allocation mechanism (210) steps from(308) to (315),• If TH< PRS< TH+ PG(706) does not change PRsthen complete adaptive pilot allocation mechanism (210) steps from (308) to (315).A method according to claim 6 wherein step 220 is applied at legitimate receiver (110) and it starts after calculating average power of each subgroup (307). A method according to any one of the preceeding claims characterized in that step 230 wherein identification of the pilot location from the received signal at the user is carried out comprises; o Intializing parameters NTS, SR, NSG, NTP, LPG(802) o Determination of the threshold THby the legitimate transceiver (120) from the average power of the received signal (803) o dividing the received signal’s subcarriers NTSinto SR(804), o Calculating the average power of a subgroup PSG(805), o Checking if j <= SR(806), if false (808), i.e., pilot locations have been detected in all subgroups, move to step (813) where j denotes the jth subgroup o if j <= SR(806) is true (807) then compare PSGwith TH, if PSG(J) < THif true (807), i.e., PSGof jth subgroup is less than TH, then allocate the subcarrier on the position a in subgroup to pilot symbol (i.e., LRG(J)= a) (810), o if at comparison of PSGwith TH, PSG(J) < THis false (808), i.e., PSGof jth subgroup is greater than TH, allocate the subcarrier on the position b in subgroup to pilot symbol (i.e., LPG(f) = b) (811), o j = j + 1 increment in j by 1 (i.e., count the subgroup for which the pilot location has been detected) (812) o Detect the pilot and data symbols from the pilot and data subcarriers, respectively (813).19

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