TR2021019472A2 - DISTRIBUTED CARRIER FREQUENCY OFFSET BALANCE FOR SECURE WIRELESS COMMUNICATION - Google Patents

Abstract

The present invention provides a method for protecting wireless communication signals from eavesdropping/interception by malicious eavesdroppers.

Description

DESCRIPTION DISTRIBUTED CARRIER FREQUENCY OFFSET BALANCEMENT FOR SECURE WIRELESS COMMUNICATION Technical Field In this invention, a method is presented to protect wireless communication signals against eavesdropping/interception by malicious eavesdroppers. Prior Art Today, the following approaches to physical layer security (PLS) are used in multi-carrier systems such as OFDM: Obtaining Secret Sequences from Wireless Channels The basic idea in such PLS techniques is to obtain a random sequence from the wireless channel. This sequence is used as a key to encrypt information that will later be exchanged between transceivers. However, the key generation approach is highly sensitive to incorrect channel estimation and channel reciprocity mismatch. Addition of Jamming (Noise/Distortion) Signals along with the Transmitted Signals In this approach, the legal node adds an intentional jamming signal by taking advantage of the free space of the legal user channel in a way that disrupts the performance of the illegitimate receiver without affecting the performance of the legal receiver. However, this may sacrifice some power and output. In these techniques, transmission parameters are specifically adjusted based on the channel between legal transceivers to meet quality of service (QoSl) requirements. Some examples are Adaptive Modulation and Coding with Automatic Repeat Request (ARQ), subcarrier activation technique based on fading, technique based on optimal power allocation. However, the problem with these approaches is that they fail if the listener has a better channel compared to the legitimate receiver. There has also been some work to take advantage of the CoMP concept for securing wireless systems. In the prior art, CoMP has been utilized to address the limitation of directional modulation since the listener cannot secure the communication if it is in the same direction as the legitimate receiver. Coordinating transmission points (TP). ,s) transmit copies of the same signal using directional modulation so that they are received accurately only at the receiver's location, providing location-based security. However, this approach also fails to provide the desired level of security if the attacker is near the legitimate recipient. CoMP is also used towards the sparse radio environment such that data can only be decoded at the intersection of information bundles while a distorted constellation is observed at other locations. This approach also does not guarantee secure communication if the attacker is close to the legitimate recipient. The prior art provides CoMP7-based transmissions from distributed antenna elements in an underwater scenario, where the strength and timing of transmissions are manipulated so that messages are obscured (and jammed) at the listening party while not at the legitimate receiver. The prior art introduces a dynamic CoMP scheme to increase secure coverage. The presented scheme is based on the received signal strength for legitimate users, where TP*s away from the legitimate user are blocked for security and energy consumption concerns. A CoMP scheme is also used in unmanned aerial vehicle (UAV) systems to provide confidentiality, where multiple reference nodes jointly detect legitimate information sent from the UAV to improve legitimate communication performance in the presence of an eavesdropper. Security Based on Carrier Frequency Offset (CFO) Compensation Prior Art A PLS technique based on CFO Pre-balancing is presented. The technique considers a point-to-point transmission in which only one CFO is present between the legitimate nodes in the communication, due to the uniqueness of the CF O resulting from any pair of nodes in the communication, regarding the legitimate receiver. However, due to the existence of many robust single CFO estimation techniques in the literature, the security provided by such approach can be easily compromised. For this purpose, the authors have complemented their approach with channel pre-balancing in order to improve the quality of security obtained. However, channel pre-equalization has an obvious disadvantage regarding the high peak-to-average power ratio (PAPR) of the signal. Purposes of the Invention and Brief Description The present invention relates to a method for protecting wireless communication signals against eavesdropping/interception by malicious eavesdroppers, in order to eliminate the disadvantages mentioned above and to bring new advantages to the relevant technique. The broadcast nature of wireless communication makes it prone to various security threats. One of these threats is the violation of communication confidentiality, also referred to as eavesdropping. In this case, a malicious node/device is trying to listen and interpret the ongoing Communication between two legitimate nodes. Classically, cryptography is used to secure communications, but with the increasing heterogeneity of future wireless networks, this approach faces challenges regarding key sharing and management. This encourages the use of physical layer security (PLS) approaches that leverage wireless channel and hardware features to secure wireless transmissions. With this in mind, PLS mechanisms such as the one discussed in this invention have become increasingly popular in recent years. The invention described in this document uses multiple transmitting nodes in the coordinated multipoint (CoMP) concept to provide orthogonal frequency division multiple access widely used in wireless communications standards such as Long Term Evolution (LTE), 5G New Radio (NR), and IEEE 802.11-based Wi-Fi networks. It provides a PLS mechanism that works together to provide secure communication for multi-carrier systems such as (OFDM). Multi-carrier Systems such as OFDM are popular because they reduce the problem of frequency selective fading by dividing the channel into many narrow sub-channels (or sub-carriers), each smaller than the coherence bandwidth, turning the channel into a flat fading one. However, in this case the System relies on orthogonality of subcarriers in the frequency domain to ensure reliable communication. Any loss of orthogonality can lead to intercarrier interference leading to serious performance degradation. This makes OFDM and other multi-carrier systems prone to any mismatch in frequency synchronization that can occur due to distortions such as Doppler and carrier frequency offset (CFO), resulting in inter-carrier interference (ICI). In this invention, this OFDM limitation is used to secure wireless transmissions. If the CFO is known at the transmitter, this can be pre-compensated before the transmission occurs. Due to the difference in CFO experienced by different user equipment (UE)-transmission point (TP) connections, the presented invention utilizes different CFOs between the desired user and the different TPs provided by the CoMP network to secure the signal. balancing does not result in any distortion for this, however, this balanced offset appears to be an undesirable interference for the illegitimate node, i.e., multiple pre-balanced CFOs provided by TPs working together, by the illegitimate node. It causes the received signal to spread across the frequency, thus causing an ICI problem that makes eavesdropping more difficult. The current PLS method, which utilizes interoperable networks, especially CoMP, can only provide region-based security. It is provided if it is near or along the direction of signal transmission. In addition, the CFO pre-equalization-based PLS approach presented in the prior art relies on the channel pre-equalization step to strengthen the security quality if the attacker can successfully predict and compensate for the single frequency shift applied. However, channel pre-equalization can potentially cause a PAPR issue that imposes stringent hardware requirements to maintain the desired performance. The presented invention solves both of the above problems by taking advantage of CFOs of geographically separate TPs in interoperable network topologies. Since the presented security method is based on CFO pre-balancing with respect to a specific legal UE, the quality of the attacker's signal is the same as the attacker's legal node. Even if it is located on the ground, it will be distorted.The fact that we have multiple separately pre-balanced CFOs in the considered system at this point means that the attacker will have a system with multiple independent frequency shifts, which is much more difficult to deal with compared to the single frequency shift observed in the case of point-to-point transmission presented in the prior art. Moreover, it is possible that the attacker can listen to the signal if he is not near the legitimate receiver but is within range of any of the coordinating TPs. In this case, the presented invention is in conjunction with channel Pre-equalization with some modification to avoid the mentioned PAPR problem. can be used. Again, we benefit from multiple geographically separate TP entities that experience independent channels with the legal node. In this case, subcarriers located in the deep fadings of a TP-label-UE link can be turned off for this particular TP and transmitted from the rest of the cooperating TPs. This eliminates the need to perform channel pre-equalization at the locations of deep fades for each TP, thus solving the PAPR problem. The found scheme forms a hybrid joint transmission (JT) and dynamic point selection (DPS) (H-JT-DPS) mechanism with channel pre-equalization and multi-CFO pre-equalization to facilitate PLS across the entire coverage area. Multiple CFO pre-equalization. While balancing ensures communication confidentiality even if the attacker is located in the same location as the legitimate node, channel pre-equalization provides security when the attacker is at any other location within the coverage area. Another possible approach that can be used in conjunction with multi-CFO pre-balancing to facilitate security against an attacker who is near one of the interoperating TPs or along the transmission direction of any TP is data splitting. With data splitting, each of the APIs working together transmits a different portion of the data to the legitimate node such that receiving signals from all of the TPs is required to properly decrypt it. In fact, the multiple CFO pre-balancing scheme found here can also be used by any other security scheme based on TPs working together to extend their zone-based security up to full security within range. To protect against eavesdroppers, use this invention over any wireless communication network. However, standards such as cellular networks based on 3GPP and Wi-Fi networks based on IEEE 802.11 are particularly relevant to the invention due to the support for multipoint coordination in both standards and the use of multi-carrier schemes such as OFDM. This provides a low-complexity method for future wireless networks that utilize the existence of multiple geographically distributed transmission points to provide secure and confidential communications through different connections between the cooperating TPs and the legitimate receiver, with each connection having an independent CFO. This is done by sending data. The independence of these CFOs, as well as those experienced by the illegitimate receiver, ensures that pre-balancing ensures that no ICI is experienced by the illegitimate receiver, while this is not the case for the illegitimate receiver. The illegitimate receiver is in the frequency domain causing ICI and impairing the possibility of listening. Description of the Inventive Figures The figures are used to further illustrate a method for distributed carrier frequency offset compensation for secure wireless communications improved by the present invention as described below: Figure 1: A flowchart of basic processes for wireless communications according to certain aspects of the present disclosure. Figure 2: An alternative implementation option of the current specification. Figure 3: Another alternative implementation option of the current specification. Figure 4: CFO pre-balancing of the legal node and illustration of the effect of the legitimate and attacker on the signal received at the nodes. Figure 5: Confidentiality of the downlink transmission. Figure 6: Illustration of multiple CFO pre-balancing with an advanced channel pre-equalization technique to provide security across the entire coverage area. Explanation of Elements and Steps in Figures: TP: Transmission Point CFO: Carrier Frequency Offset UE: User Equipment Steps: 110, is the selection of coordinating TPs. 120, each TP estimates the CFO* between itself and the desired user. 130, In this step , in step (120) the required balancing is calculated based on the estimated CFO. 140 is the transmission of user data from coordinating TPs. 210 is the selection of coordinating TPs. 220 is the channel pre-equalization experienced on all connections between the TPs and the user, with each TP estimating the CFO between itself and the intended user. . 240 is the Pre-information of the estimated CFO obtained in step 220 250 is the transmission of user data from coordinating TPs 310 is the selection of coordinating TPs. 320, each TP estimates the CF0 between itself and the desired user. 330, the user data is divided into different partitions to which each coordinating TP sends a portion of the split data. 340, the estimated CFO° obtained in step 220 350 is the transmission of user data from the coordinating TPs 410 is the baseband signal spectrum before CFO Pre-equalization 430 is the baseband signal spectrum after CFO Pre-equalization. 450 is the legitimate receiving node, 470 is the correctly frequency synchronized baseband signal received by the legitimate node, 480 is the signal received by the attacker with error-free frequency synchronization. . 520 are geographically separate TPs serving the UE together. 540 is the frequency synchronized signal received by the legitimate receiving node. 550 is the attacker node that aims to listen in on the communication. 560 is the signal received with distortion (frequency spread) at the attacker's node. 610 represents a frequency domain single-drop channel Pre-equalization process at each of the co-operating TPs 620 is the CFO pre-equalization step at each of the co-operating TPs 630 is a geographically distinct 640 represents the independent frequency channel responses (CFR) experienced by each TP relative to the legitimate UE. 650 represents planned subcarriers based on deep fades that carry the data to be transmitted to the legitimate UE. 660, independently occurring deep damping. Detailed Description of the Invention. The novelty of the invention is explained with examples that do not limit the scope of the invention and are intended only to illuminate the subject of the invention. The present invention is explained in detail below. The invention is a method for protecting wireless communication signals against eavesdropping/interception by malicious eavesdroppers. Certain aspects of the present specification: One embodiment of the invention relates to a method of preventing eavesdropping of a wireless communications device by malicious eavesdroppers, wherein; The first step (110) of the presented invention consists of selecting the coordinating transmission points (TPs). This selection may depend on different criteria, such as the received signal strength indicator (RSSI), the received power relative to the serving TP, or a combination of both. Coordination team selection also includes capacity maximization, spectral efficiency, energy efficiency, etc. It can be carried out for different purposes/restrictions such as. In addition, according to the present invention, it is possible to consider the carrier frequency offset (CFO) between the TP and the legitimate receiver as a criterion for the selection of the coordinating TP. In the second step (120), each TP estimates the CFO between itself and the desired user. CFO estimation can be performed using preambles or blindly. is calculated. Then, step (140) initiates transmission from all or some of the selected TPs. Here, transmission from different TPs can carry the same data or different portions of data. Figure 2 is a flow chart illustrating an alternative embodiment of the present specification, thus another embodiment of the invention relates to a method for preventing a wireless communication device from being eavesdropped by malicious eavesdroppers, wherein: The first step 210 of the presented invention consists of selecting the coordinating TPs. This selection may also depend on different criteria such as the received signal strength indicator (RSSI), the received power according to the serving TP, or a combination of both. It can be realized for different purposes/constraints such as capacity maximization, spectral efficiency, energy efficiency, etc. In addition, according to this invention, it is possible to consider the CFO between the TP and the legal buyer as a criterion for the coordinating TP Selection. In the second step 220, each TP estimates the CFO between itself and the desired user. CFO estimation can be performed using preambles or blindly. is being carried out. Step 240 performs channel pre-equalization for each TP-UE connection. Then step (250) initiates transmission from all or some of the selected TPi. To avoid problems such as high PAPR, dynamic point selection (DPS) can be used so that deeply damped subcarriers are not used for this particular connection. Figure 3 is a flow chart illustrating an alternative embodiment of the present disclosure, whereby another embodiment of the invention relates to a method of preventing eavesdropping of a wireless communications device by malicious eavesdroppers, wherein: The first step 310 of the present invention is the coordinating TP" This selection may depend on different criteria such as the received signal strength indicator (RSSI), the received power according to the serving TP7, or a combination of both. In addition, according to this invention, it is possible to consider the CFO between the TP and the legitimate recipient as a criterion for the selection of the coordinating TP, in the second step 320, each TP estimates the CFO between itself and the desired user. .CFO estimation can be performed using preambles or blindly. Step 330 involves splitting the data to be transmitted from different TPi. This division can occur at an intrasymbol level (for example, a TP may transmit the real part of the symbol, while the imaginary part of the same symbol is transmitted by the same signal) or at a subcarrier level (where different TPs transmit different subcarriers). is being carried out. 0 Then step 350 initiates transmission from all or some of the selected TPs. Here, Figures 2 and 3 (and the steps therein) are not mutually exclusive, in other words, different applications can use different paths to create more alternative applications. It should be noted that the method described in Figure 4 deals with the CFO pre-balancing of the legitimate node and an illustration of its effect on the signal received at the legitimate node and the Attacker's node. Explanation of FIG. The frequency shift on the signal (430) on which the frequency shift has been applied is reset at the attacker's node by the CFO between the legitimate transmitter (440) and the legitimate receiver (450), resulting in a smoothly received signal (460). (470), the frequency shift on the frequency-shifted signal (430) is not reset by the CFO between the legitimate transmitter (440) and the attacker node (470), but rather the received signal, which is the signal received by the attacker with error-free frequency synchronization (480). A compound undergoes random frequency shifting. Explanation of Figure 5: Extension of Figure 4 to multiple transmitter TPs (520). The frequency shifting step is performed at each TP in step 510, which is the CFO pre-balancing step. The frequency shift applied to the baseband signal at each TP (520) is determined by the CFO between the relevant TP and the legal receiver node (530). Since this is the case in Figure 4, each of the frequency shifts applied in the CFO pre-equalization step (510) is reset by the relevant CFO upon reaching the legitimate receiving node (530), resulting in the received signal (540) with seamless frequency10 synchronization applied. This type Resets do not occur at the attacker's node 550, giving rise to a frequency spread signal 560 that is filled with Cl and thus difficult to decrypt. The method described in Figure 53 is an example of a collaborating network implementing the presented invention to facilitate the confidentiality of downlink transmission. Figure 6 shows the application of co-channel pre-equalization and multi-CFO pre-equalization, a hybrid co-transmission and dynamic point-selection (H-JT-DPS) to facilitate security across the entire coverage area. ] technique prevents pre-equalization at deep fading positions. In Figure 6, (660) represents planned subcarriers based on deep fadings that carry the data to be transmitted to the legitimate UE. Based on the CFR of each TP, some subcarriers for that particular TP are turned off and transmitted by the other TP with relatively better CFR at that position (i.e., DPS based on the subcarrier). Thus, each TP channels the channel at deep damping positions. It does not have to be pre-equalized, thus avoiding the problem of high PAPR. Explanation of Figure 67: This figure shows the application of the H-JT-DPS concept, each of the TPs working together, at deep damping positions (660). prevents transmission and thus can ignore pre-equalizing the channel response at these locations in step 610. It should be understood that while some subcarriers are turned off for some TPs due to deep fading at their respective positions, other subcarriers experiencing relatively good channel condition across all of the TPs are transmitted through all of them. This is equivalent to applying DPS to some subcarriers and JT to others. Step (620) is legal The UE (not shown) applies a frequency shift to the signal based on the expected CFO of a particular TP 630. Process steps; While the prior art has different mechanisms for coordinating TP selection (as explained in the previous section), the invention also discloses a new alternative, namely the selection of coordinating TPs based on the CFO between the TP and the legitimate buyer. In general, CFO forecasting and balancing is well studied. However, utilizing multiple TPs and CFOS in a CoMP environment to ensure secure Communication is a new recommendation. A. CFO pre-equalization can be applied in conjunction with channel Pre-equalization to increase the safe coverage area. The optional channel pre-equalization step is specified at step 610 in Figure 63. D. Hybrid DPS and JT to avoid deep damping subcarriers for different TP-user connections. This facilitates smooth channel front blocking at each TP7 without increasing the PAPR problem (610). E. Before transmission, data splitting in conjunction with multiple CFOs can also be implemented instead of channel pre-equalization. Other techniques such as directional modulations based on COM P° can also be used (330 l. The invention is a method for protecting wireless communication signals against eavesdropping/interception by malicious eavesdroppers. Thus, it can be applied to the industry related to communication security. Based on all the above information As a rule, a distributed carrier frequency offset balancing method for secure wireless communication includes the following steps: o Selecting the coordinating transmission points, 0 Estimating the carrier frequency offset between each coordinating transmission point and the desired user, o Balancing the estimated carrier frequency offset, o Coordinating Initiating transmission from coordinating transmission points. A distributed carrier frequency offset balancing method for secure wireless Communication includes the following steps: o Selecting the coordinating transmission points, 0 Estimating the carrier frequency offset between each coordinating transmission point and the desired user, 0 Each coordinating pre-equalizing the channel between the transmission point and the user, 0 balancing the estimated carrier frequency offset at each transmission point, o starting the transmission from the coordinating transmission points. A distributed carrier frequency offset balancing method for secure wireless communication includes the following steps; o Selecting the coordinating transmission points, 0 Estimating the carrier frequency offset between each coordinating transmission point and the desired user, o Dividing the data to be transmitted between the coordinating transmission point 0 Pre-equalizing the channel between each coordinating transmission point and the user, 0 Each balancing the estimated carrier frequency offset at the transmission point, o Initiating transmission from coordinating transmission points. Among these basic concepts, it is possible to develop several configurations of the subject of ICT; Therefore, the invention cannot be limited to the examples described herein and the invention is essentially as defined in the claims. It is understood that a person skilled in the art may convey the novelty of the invention using similar embodiments and/or that such embodiments may be applied to other fields similar to those used in the relevant art. Therefore, it is also understandable that such configurations lack the criteria of innovation and the criterion of transcending the state of the art. Industrial Applicability of the Invention The invention increases the confidentiality of communication links against eavesdropping attacks. Unlike most of the existing physical layer security techniques, which cannot provide communication confidentiality when the eavesdropper is very close to the legitimate user due to channel correlation, the found method provides communication confidentiality even against such eavesdroppers (in other words, eavesdroppers who are located together with the legitimate user).TR

Claims (1)

1.CLAIMS. It is a distributed carrier frequency offset balancing method for secure wireless communication and includes the following steps; o Selecting the coordinating transmission points, 0 Estimating the carrier frequency offset between each coordinating transmission point and the desired user, o Optionally, dividing the data to be transmitted between the coordinating transmission point and/or splitting the data to be transmitted between each coordinating transmission point and the user. pre-equalization of the channel. Pre-compensation of the estimated carrier frequency offset, o Initiation of transmission from coordinating transmission points. . A method according to claim 1, characterized in that the selection of coordinating transmission points may depend on the received signal strength indicator (RSSI), the received power relative to the serving TP, or a combination thereof. . It is a method according to claim 1 or 2, characterized in that the selection of the coordination team is carried out based on capacity maximization, spectral efficiency or energy efficiency. . A method according to claim 1 or Z, characterized in that the selection of the coordinating transmission points may depend on the carrier frequency offset (CFO) between the TP and the legal receiver. . A method according to any one of claims 1 to 4, characterized in that the estimation of the carrier frequency offset between each coordinating transmission point and the desired user is carried out using preambles or blindly. . A method according to any one of claims 1-5, characterized in that dynamic point selection (DPS), in which subcarriers in deep damping are not used for this particular connection, is used to avoid problems such as noise increases in case of deep damping during transmission from all or selected TP°s is done. 7. A method according to any one of claims 1-6, characterized in that the division of data to be transmitted from different TPs is as follows at an intra-symbol level, where one TP transmits the real part of the symbol, while a different TP transmits the imaginary part of the same symbol or at a sample level, where different TP71s transmit different samples of the same signal, or at a subcarrier level, where different TP71s transmit different subcarriers. TR