TWI459779B - Node B used in ensuring wireless communication - Google Patents

Description

Node B used in ensuring wireless communication

The present invention relates generally to wireless communications. More specifically, the present invention relates to a method and system for securing such wireless communications by strategically locating the sources and/or recipients of such communications.

As wireless connectivity becomes increasingly popular and reliable, it is expected that all of the digital computing, data storage and media storage devices that are widely used today will become part of the Ad-hoc wireless communication network. However, these networks are vulnerable to data security vulnerabilities in many ways. For example, Ad-hoc networks where individual users communicate directly with each other without using intermediate network nodes create new and vulnerable features for users and the Internet.

To reduce the vulnerability of wireless networks, technologies such as Wired Equivalent Privacy (WEP), Wi-Fi Protected Access (WPA), Extensible Authentication Protocol (EAP), and GSM-type encryption have been developed. While these technologies provide some protection, they remain vulnerable to multiple trusts, rights, identities, privacy, and security issues. For example, although a particular wireless communication node may have the correct WEP key to communicate with a wireless user, the user may not know if the particular node is trusted.

In addition, authentication of users using such keys typically occurs at a higher level of the communication stack. Accordingly, a malicious wireless user or hacker may have some (limited) access to the communication stack even when these controls are located. This access creates weaknesses such as blocking service attacks and others.

The fact that the wireless signal degrades with distance triggers a natural security measure, because intercepting a signal requires close proximity to the source to detect the signal. This is especially significant for small networks where the transmission power is typically low and communication is typically done at the highest rate and in an Ad-hoc manner. In many cases, the physical proximity distance may be the most difficult attribute to achieve for a malicious attacker. In fact, communication that can only be detected within a very short proximity of one of the transmitters does not require very good protection.

Therefore, it would be desirable to implement a wireless network security system that would take advantage of the natural security provided by wireless signal degradation. In addition, it would be desirable to ensure that any information to be transmitted to a user is only accessible at the location of the user, such that an eavesdropper located near the user but not at the user's current location cannot receive it. The complete message transmitted to the user.

The present invention relates to a method and system for ensuring wireless communication. In one embodiment, different security measures are employed based on the distance between a receiver and a transmitter, whereby the data in the wireless communication can be demodulated only by the recipient within the particular trust zone. In another embodiment, a plurality of bit stream segments are transmitted by a plurality of transmitters to a receiver located in a region of the transmission pattern of the transmitters. Alternatively, the receiver performs a function on the Packet Data Units (PDUs) sent by the transmitter. In another embodiment, the primary modulation point of a modulated constellation is divided into clusters adjacent to the secondary modulation point, which can only be demodulated by a receiver within range of the transmitter. In another embodiment, a master waveform is transmitted that is superimposed on a QPSK signal with a hierarchical modulation (HM) having encoded descrambling information.

In this specification, the term wireless carrier/receiver unit (WTRU) non-limiting includes a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a station (STA) or Any other type of device that can operate in a wireless environment. In this specification, the term 〝 access point (AP) non-limiting includes a base station, a Node B, a network controller, or any other type of interface device in a wireless environment.

The present invention is based on the fact that most conventional channel codes (e.g., Turbo codes, low density parity codes (LDPC), or the like) operate close to the Shannon limit in most practical architectures. When applied to a wireless communication system, (ignoring the fading effect), the ability of the receiver to demodulate the variable data is almost a binary function of the effective SNR of the input at the receiver decoder.

Features of the invention may be incorporated into an integrated circuit (IC) or constructed in a circuit that includes numerous interconnect components.

Figure 1 is a graph showing the relationship between the effective decoder input SNR and a decoder output BER. There is a critical SNR such that when the actual effective SNR falls below the critical SNR, the decoder is completely disabled (i.e., the decoder output BER is 1) and data within a wireless communication cannot be read. Conversely, if the actual effective SNR at the decoder input is above the critical SNR, the error probability at the decoder output is extremely low and the data within the wireless communication has a very high probability of being read.

Since it is assumed that the channel code is approaching the Shannon limit, it can be assumed that the coding operation is performed at the Shannon capacity rate. In addition, it is best to actually consider spectral efficiency work because it makes the digital results independent of bandwidth. For a complex value plus Gaussian white noise (AWGN) channel, the Shannon capacity rate is: R = log ₂ (1 + SNR ) Equation (1)

Wherein SNR is used in the E _b /N ₀ orientation. It is generally accepted that for information rates above this rate, reliable information decoding is not possible, and for encoding rates below this rate, reliable information decoding is essentially guaranteed. In fact, this is a realistic assumption in the case of large block length codes such as LDPC and Turbo codes.

The SNR basically depends on the distance between the transmitter and the receiver. The dependence of SNR on the distance from the transmitter is given by the following power law:

Where is a nominal SNR at 1 unit distance. In open space, the exponent γ is 2, but in a practice wireless network, the exponent γ is between 3 and 4, depending on the topology of the channel.

Today, SNR _c is the critical SNR of the selected coding architecture. Then, the distance covered by this critical SNR is determined by: And it can be rewritten as follows in dBs:

The present invention makes d a function of one of the security measures. By dynamically selecting d, a receiver that is closer than d can operate with a looser security measure, and a receiver that is farther than d will require a stricter security measure.

In a traditional communication architecture, the channel coding architecture is fixed because it is quite expensive to have a programmable 〞 encoder for a completely different coding architecture. Therefore, the SNR _c is fixed. Then, from equations (3) and (4), d can be controlled by controlling E and γ in a communication system. In order to achieve this goal, at least one of these controls must be changed in accordance with external confidentiality related information that may or may not be present at the receiver.

E is defined as the nominal SNR at a unit distance. In reality, E is the transmission power of each information bit that is desired to be given to a particular receiver. The nominal SNR definition is necessary because the power law model of equation (2) collapses for small d values and derives infinite SNRs. Therefore, controlling E means controlling the output power per information bit. For example, control of the output power per information bit can be accomplished by any one or combination of the following: 1) by directly controlling the output power applied to a particular receiver data; 2) by adding a signal to the transmitted signal The addition of a noise-like signal reduces the output SNR and thus the receiver's received SNR. This has the benefit of maintaining a constant output power while adjusting the SNR for individual receivers.

3) by controlling a modulation architecture (such as selecting QPSK/M Quadrature Amplitude Modulation (QAM) / M Phase Shift Keying (PSK) / Frequency Shift Keying (FSK), or similar architecture); 4) by adjusting one Bit length (for example for UWB systems); 5) by controlling the jitter and timing of the transmission operation; 6) by controlling the effective coding rate of a data for delivery to the receiver, which is a preferred embodiment of the present invention Architecture. The method provides the ability to maintain a constant power level between APs and WTRUs in a WLAN system in a manner that maintains a consistent regular grid spacing between APs in a system without affecting the performance of the CSMA system due to fluctuating transmission power levels; 7) by changing the rate matching rule to induce breakdown or repetition of the symbol and effective bit energy; 8) by controlling a modulation index; and 9) by controlling the amount of interference that the receiver will experience.

Non-limiting interference control can be accomplished by one or a combination of the following: 1) by applying variable interference management techniques, such as pre-processing the desired receiver signal and/or interfering receiver signals and changing the cross-talk. The degree of removal or introduction; 2) by selecting power control (this power control can be a procedure that is optimized together with security measures); 3) controlling the number of potential interferers by time/frequency/code scheduling; 4) by dynamic interference control (e.g., on and off); and 5) by transmitting a message through a third party beacon, which then signals the additional interference pattern.

In addition, in the case where there are multiple receiving antennas, the value of E can be made according to the angular position (θ) of the receiver relative to the transmitter (ie, E=E(θ)), and thus d can also be made. A function of θ. This triggers another set of control possibilities, the non-limiting aspects of which include: 1) shaping the beam towards or away from the receiver with azimuth, elevation or both; 2) using smart antenna technology for interference management; 3) Import of transfer patterns.

Regarding the value of γ, γ depends on the Doppler spread of the received signal, which usually depends on the relative speed of the receiver relative to the transmitter and the geographical situation of its environment. However, the transmitter can artificially increase the Doppler effect range by internal signal processing. Since the value of gamma depends on the geographical situation of the environment, if the transmitter is equipped with multiple antennas, it can control gamma to some extent by aiming at transmitting signals in an appropriate manner.

The receiver can detect an active interference of the enemy by the wireless channel according to the present invention. If the receiver is informed through the auxiliary component that the receiver should be able to successfully demodulate the variable stream, in fact, after enough attempts, there is no way to do so, and because the receiver's security measures and communication control are When the data stream demodulation mode is set, the receiver can determine that the wireless channel is being violated.

The present invention preferably uses a coding rate as a parameter dependent on the receiver security measure. In general, the ability of a receiver to demodulate a signal depends on the geographic situation (effective distance), which is more complex than the straight-line distance. If necessary, the transmitter and receiver can slowly (or slowly reduce) one or more of the control parameters and detect that reliable data decoding becomes possible (or is no longer possible). Find the effective distance between the two.

2 is a block diagram of a communication system 100 including a transmitter 110 and a receiver 120 in accordance with the present invention. The transmitter 110 includes a protocol stacking unit 112, a channel encoder 114, a rate matching unit 115, a multi-layer security bit (MLSB) scrambler 116, and a physical channel processing unit 118. The receiver 120 includes a physical channel processing unit 128, an MLSB descrambler 126, a rate dematching unit 125, a channel decoder 124, and a protocol stacking unit 122. Protocol stacking units 112 and 122, channel encoder 114, rate matching unit 115, rate dematching unit 125, channel decoder 124, and physical channel processing units 118 and 128 are essentially the same components used by conventional transmitters and receivers. The protocol stacking unit 112 generates an information stream and the information stream is encoded by the channel encoder 114 to prevent errors, and then further processed by the physical channel processing unit 118 for transmission via a wireless channel 130 (i.e., a specific empty interfacing plane). . This program is reversed at the receiver 120.

Channel encoder 114 maps an input data sequence into an output channel symbol sequence. The MLSB scrambler 116 confuses the channel symbols. The channel symbols can be bit or higher order modulation symbols. Not all symbols must be hacked. The MLSB scrambler 116 may take a subset of the symbols and prioritize them. The receiver should know which symbols are partially disturbed.

Several privacy layers are defined in accordance with the present invention. The proportion of a disturbed symbol that a MLSB descrambler 126 can descramble depends on the privacy layer. For any symbol that the MLSB descrambler 126 can descramble, the MLSB descrambler 126 will process it. For any symbol that the MLSB descrambler 126 cannot descramble, the MLSB descrambler 126 inserts an erasure (i.e., channel observation of 0) for the symbol. Any conventional decoder has the ability to eliminate signal operation. Therefore, this will not cause problems for a system of today.

The utility of the security system in accordance with the present invention on receivers that are unable to descramble all symbols is an increase in coding efficiency and a simultaneous reduction in the effective SNR per information bit. The specific amount of increase in coding rate and effective SNR reduction depends on the level of confidentiality, which will be explained below.

The rate matching unit 115 within the transmitter 110 operates in accordance with a rate matching rule that can be changed to cause a breakdown or repetition of the symbol and effective bit energy. A channel having a coding rate R is used. R is greater than 1 bit per channel symbol and the efficiency of the privacy layer n is given by:

Where θ represents the proportion of the victim symbol and e _n is a descrambler having a privacy layer n (ie, the rate dematching unit 125 in the receiver 120) is capable of descrambling the symbol scale. In all cases, e _n [0,1], e _l =0, e _N =1. The initial per-bit bit SNR (more precisely E _b N ₀ ) is represented by E ₀ . The effective SNR of the privacy layer n is given by: E _n = E ₀ [1-θ(1- e _n )] Equation (6)

Both the ratio and the SNR are simply converted by the ratio of undisturbed known bits, which is given by: η _n =1 - θ(1- e _n ) Equation (7)

Therefore, it is sufficient to formulate an analytical formula for this quantity alone. The dependence of the SNR on the distance from the emitter is given by equation (2).

In accordance with the present invention, a transmitter-to-receiver distance capable of demodulating data can be determined by determining that a particular ratio of known un-erased symbols (i.e., symbols that the receiver can descramble) is determined. Equation (2) is substituted into equation (7) and solution d is obtained to obtain the following equation:

Next, assuming that one of the symbols η is not erased, equations (5) and (6) are substituted into equation (8) to obtain the following equation:

The percentage of distance that a particular level of privacy η can reach can be expressed as a percentage of the distance that can be reached by full privacy (η = 1). This is NSPR, which is defined as follows:

The NSPR is not dependent on E, but it is dependent on the nominal transmission rate. As an example, Figure 3-6 presents a plot of the percentage of known symbols on the NSPR pairs of four different architectures: R = 1, γ = 2; R = 1, γ = 4; = 1/2, γ = 2; R = 1/2, γ = 4. From the simulation results, it is observed that by only revealing 50% of the channel symbol, the receiver located at a distance farther than about 60% of the completely safe transmission radius may not be able to demodulate the information. Therefore, if a receiver exceeds the effective distance of its secret parameters, it is theoretically prohibited from decoding data with a BER well above 50%.

Figure 7 shows a secure network 700 comprising a plurality of WTRUs 705, 710, 715, 720 and 725, which are in a plurality of non-overlapping trusted areas 730, 740, 750 or one outside of the trusted areas. I don't trust the operation in the 760 area. The trust zones 730, 740, 750 and the untrusted zone 760 are established in such a manner that selection of transmission parameters such as a code rate architecture, a breakdown architecture, a power architecture or the like results in a trust zone 750 and a do not trust zone. A receiver outside the boundary of 760 (i.e., a WTRU) cannot decode the transmission signal, even if the receiver is fully aware of all transmission parameters. In addition, selecting a bit disturbing architecture (to be implemented by the MLSB subsystem) causes the receivers inside the trust zone 730 to demodulate the data, even if the receivers do not know any of the disturbed bits. . The received power will be high enough for a successful demodulation operation to occur, even if the victim bit is simply used to be broken down.

The receiver within the trust zone 740 is no longer capable of demodulating the transmitted data unless it knows some portions of the scrambled pattern applied by the MLSB. Accordingly, the receiver located within the trust zone 740 is forced to pass the transmitter with some type of authentication procedure to expose some necessary portions of the scrambling sequence to it.

The receiver within trust zone 750 does not have the ability to demodulate even if it knows the portion of the scrambling sequence that is exposed to the receiver within trust zone 740 (e.g., by eavesdropping side communications thereby allowing these receivers to access the sequence) Data transmitter. In fact, these receivers are required to request additional information about the scrambling sequence (eg, they may have to know the complete sequence), and therefore they must go through a receiver that is independent of the trust zone 740 (most likely more demanding) Certification process. As previously mentioned, the receiver in region 760 is unable to demodulate the transmitted data under any circumstances.

In accordance with an embodiment of the invention described above, the distance from a transmitting WTRU 705 to a receiving WTRU is a function of privacy measures. By dynamically selecting the distance d (e.g., 50 meters), a receiving WTRU 710 that is closer than d can operate with a looser security measure, while receiving WTRUs 715, 720, and 725 that are more than d would require a stricter security measure. .

FIG. 8 shows a conventional network 800 including an AP 805 and a WTRU 810. When the AP 805 transmits a one-bit stream 815 to the WTRU 810, an eavesdropper 820 within range of the AP 805 can receive a full bit stream, such as 111000101.

FIG. 9 illustrates a network 900 including a plurality of access points (APs) 905, 910, 915 and a WTRU 920 and an eavesdropper 820 of FIG. 8 in accordance with an embodiment of the present invention. By using multiple APs 905, 910, 915 instead of the traditional network 800 of Figure 8, using only a single AP 805, the bit stream 815 is guaranteed not to be decrypted by the eavesdropper 820. The WTRU 920 is located at the intersection 935 of the transmission pattern of the APs 905, 910, and 915, whereby the WTRU 920 receives a first segment 930 _A 〝 111 之一 of the bit stream 815 from the AP 905, and receives a bit from the AP 910. The second segment 930 _B 〝000 之一 of one of the meta-streams 815 receives a third segment 930 _C 〝 101 之一 of the bit stream 815 from the AP 915. Each segment 930 _A , 930 _B , 930 _C is referred to as a PDU, and the original bit stream 〝 111000101 〞 is referred to as a Service Data Unit (SDU). The WTRU 920 then reassembles the entire encrypted SDU from the three PDUs 930 _A , 930 _B , 930 _C. Since the eavesdropper 820 is not physically located in the intersection 935 of the transmission pattern of the APs 905, 910, and 915, causing all segments 930 _A , 930 _B , and 930 _C to be received at an error rate compared to the WTRU 920, the eavesdropper 820 cannot interpret the entire bitstream 815 (even if one knows a key).

In the network 900 of FIG. 9, the SDU interpreted by the WTRU 920 is 111000101, where PDU _A = 111, PDU _B = 000, and PDU _C = 101. If the eavesdropper 820 barely interprets two of the three PDUs (eg, 000 and 101), the eavesdropper 820 will barely get incomplete but correct partial information.

In an alternate embodiment, any PDUs that the eavesdropper 820 does receive become meaningless as long as they are incomplete. For example, the SDU that needs to be sent to the WTRU 920 within the network 900 is 111000101. However, three PDUs (e.g., PDU1, PDU2, PDU3) issued by three different APs 905, 910, and 915 are not fragmented as shown in Figure 9, but instead result in SDU = PDU1 XOR PDU2 XOR PDU3, Where PDU1=100110011, PDU2=110000111 and PDU3=101110001, causing SDU=100110011 XOR 110000111 XOR 101110001=111000101, where XOR is a mutually exclusive or function. Thus, assuming that the WTRU 920 is at the intersection 935 of the transmission pattern of APs 905, 910, and 915, the WTRU 920 can receive all three PDUs and XOR these PDUs to interpret the SDU 111000101. If the eavesdropper 820 captures either of these three PDUs, this is completely meaningless for interpreting the SDU. Alternative mechanisms other than XOR are also possible, such as scrambling the sealed packets and issuing different bits from different transmitters unless the transmission is successfully received.

In another embodiment, a location type authentication mechanism can be incorporated into network 900 of FIG. The WTRU 920 receives transmissions from APs 905, 910, and 915 and reports its location to each of APs 905, 910, and 915. Based on the reporting locations of the WTRU 920 and the APs 905, 910, and 915, each of the APs 905, 910, and 915 can initiate an agreement to be higher or lower than the nominal between each respective AP 905, 910, and 915 and the WTRU 920. The variable effective coding rate of the proposed coding rate is either high or low, and a message sequence is sent requesting a positive acknowledgement (ACK) or a negative acknowledgement (NACK) from the WTRU 920. Accordingly, the agreement establishes a criterion that specifies whether the WTRU can decode transmissions received from APs 905, 910, and 915 based on the location of the WTRU 920 relative to the locations of APs 905, 910, and 915. If the location reported by the WTRU 920 is determined to be correct, the agreement will verify the confidence of the location of the WTRU 920 by processing the ACK/NACK message received by the WTRU 920 in response to the sequence of messages.

The verification of the WTRU 920's confidence may also be made to cause the WTRU 920 (or the user of the WTRU 920) to share a common secret with the APs 905, 910, and 915. For example, if APs 905, 910, and 915 require the location indicated by WTRU 920 to be authenticated, APs 905, 910, and 915 send a challenge issue via multiple PDUs (which may be segmented or encrypted as previously described). That is, the challenge issue can only be interpreted by the WTRU 920 when the WTRU 920 is in its location. Therefore, the WTRU 920 cannot answer the challenge question unless it is located at a location where the challenge problem can be interpreted.

Figure 10 shows an example of a hierarchical modulation (HM) architecture defined by a combination of primary and secondary modulation architectures (QPSK and BPSK, respectively in this example). It is well known that a QPSK modulation architecture is defined by four modulation points, which together construct a QPSK modulation constellation. The modulation points exhibit carrier phases of π/2, 3π/2, -π/2, and -3π/2, respectively, and represent two bits 00, 01, 10, and 11, respectively. Similarly, it is well known that a BPSK modulation architecture is defined by two modulation points that together construct a BPSK modulation constellation. The modulation points exhibit carrier phases of +δ and -δ弪, respectively, and represent one bit 0 or 1, respectively. The HM architecture is then defined by eight modulation points, constructed from primary and secondary modulation constellations.

The HM modulation points are (π/2-δ), (π/2+δ), (3π/2-δ), (3π/2+δ), (-π/2-δ), (-π The carrier phases of /2+δ), (-3π/2-δ), (-3π/2+δ) and represent three bits 000, 001, 010, 011, 100, 101, 110, and 111, respectively. These eight modulation points form four clusters, each cluster containing two small interval modulation points. For example, the modulation represented by the carrier phase (π/2-δ) and (π/2+δ) constitutes a cluster. The transmitter transmits a sequence of symbols obtained from the HM constellation through a wireless channel that attenuates and contaminates the signal as the signal travels farther away from the transmitter. In general, a receiver closer to the transmitter will receive a signal with better signal strength and signal quality, so that it can accurately detect the carrier phase and its associated three bits. However, a receiver remote from the transmitter typically receives a signal with a lower signal strength and signal quality, so that even if it can determine the cluster to which the transmitted symbol belongs, it may not be able to distinguish the small interval modulation points in each cluster. Therefore, this receiver can detect the main modulation but cannot detect the secondary modulation. Accordingly, the receiver can detect two bits of data but cannot detect the third bit.

This embodiment of the invention can be used to implement a privacy or trust zone. The data associated with the primary modulation point (i.e., the first 2 bits) is encoded or encrypted or scrambled with a key, and the key itself is transmitted via a third bit of a sequence of symbols. Thus, a receiver within a trust zone can detect the key and use it to decode or decrypt or descramble the primary data. A receiver outside a trusted zone can detect the primary data but cannot detect the key, and thus cannot decode or decrypt or descramble the primary data. Any modulation architecture can be used as the primary and secondary modulation architecture of the present invention. Examples include M-ary PSK, M-ary FSK, M-ary QAM, or the like. In addition, only selected modulation points within the main modulation constellation can be superimposed by the secondary cluster. Finally, more than two layers of grading can be applied. For example, QPSK plus BPSK plus BPSK presents a three-layer HM.

In another embodiment, a layered HM architecture can be implemented. Figure 10 shows a simple two-layer architecture in which the main waveform is a QPSK signal that is stacked with a double phase shift keying (BPSK) HM. When the SNR of a receiver is high, it is possible to distinguish all constellation points. As the SNR decreases, it becomes difficult to distinguish between the BPSK level and the nominal QPSK constellation point and thus lose the HM data.

According to the present invention, the scrambled data is modulated by the main waveform, and the descrambling information is encoded in HM. The descrambling information facilitates successful reception when the receiver is located in an area in which the HM can be recognized. When the receiver is too far away and therefore cannot extract HM data, the descrambling information must be explicitly requested through other channels. By varying the power assigned to the HM waveform, the range can be area controlled.

Although the features and elements of the present invention have been described in terms of a particular combination of the preferred embodiments, each of the features or elements may be used without or without other features and elements of the preferred embodiments. Used under a variety of combinations.

BER‧‧‧ decoder output

SNR‧‧‧Efficient decoder input

100‧‧‧Communication system

AP‧‧‧ access point

WTRU‧‧‧Wireless Transmission/Reception Unit

The invention will now be described in more detail by way of example with reference to the accompanying drawings in which: FIG. 1 is a graph showing a relationship between the effective input SNR of a receiver decoder and the output BER of the decoder. Figure 2 is a block diagram of a wireless communication system including one of the transmitters and a receiver for ensuring wireless communication in accordance with the present invention; and Figure 3 is a diagram showing the normalized safety proximity radius (NSPR) and A graph showing the relationship of the symbol under the condition of R=1 and γ=2; FIG. 4 is a graph showing the relationship between the NSPR and the known symbol under the condition of R=1 and γ=4; Figure 5 is a graph showing the relationship between NSPR and known symbols under the conditions of R = 1/2 and γ = 2; Figure 6 is a graph showing NSPR and known symbols at R = 1/2, γ. A graph representation of the relationship under the condition of =4; FIG. 7 is a simplified diagram of a secure network having a plurality of trusted areas for ensuring wireless communication in accordance with an embodiment of the present invention; and FIG. 8 is a conventional network. One of the eavesdroppers may intercept a bit stream transmitted from an AP to a WTRU; FIG. 9 is a network according to another embodiment of the present invention, Each of the plurality of APs transmits PDUs to a WTRU within one of the trusted areas of the transmission pattern of each of the APs to ensure wireless communication; and FIG. 10 shows a QPSK modulation constellation, which illustrates how Wireless communication is secured in accordance with another embodiment of the present invention.

WTRU. . . Wireless transmission/reception unit

Claims (8)

A Node B for use in securing wireless communications, the Node B comprising: a transmitter configured to transmit an encrypted signal to a WTRU to cause decryption of the encrypted signal depending on the WTRU Corresponding a geographic trust zone, wherein the encrypted signal allows decryption of the encrypted signal under the condition that the trusted zone is a first trusted zone, and the encrypted zone is encrypted if the trusted zone is a second trusted zone The signal prevents decryption of the encrypted signal. For example, the B node described in claim 1 of the patent scope, wherein the trust zone is one of a plurality of geographic trust zones. The Node B of claim 1, wherein the transmitter is further configured to modulate a message to generate the encrypted signal by using a hierarchical modulation point selected from a hierarchical modulation constellation. The Node B of claim 3, wherein the modulating a message comprises: encrypting the message by using a first encryption code; and modulating using a first modulation level of the hierarchical modulation point Encrypting the message; and modulating the first encryption code using a second modulation level of the hierarchical modulation point. The Node B of claim 1, wherein the encrypted signal comprises a scrambling symbol in a message, the message being a message that is scrambled using a scrambling sequence. The Node B of claim 1, further comprising: a processor configured to adjust a size of the trust zone by adjusting a transmission parameter. For example, the B node described in claim 6 of the patent scope, wherein the transmission parameter is a A rate architecture, a breakdown architecture, or a power architecture. The Node B of claim 1, further comprising: a processor configured to verify the location of the WTRU.