Analysis of impersonation attacks on systems using RF fingerprinting and low-end receivers

Recently, physical layer security commonly known as Radio Frequency (RF) fingerprinting has been proposed to provide an additional layer of security for wireless devices. A unique RF fingerprint can be used to establish the identity of a specific wireless device in order to prevent masquerading/impersonation attacks. In the literature, the performance of RF fingerprinting techniques is typically assessed using high-end (expensive) receiver hardware. However, in most practical situations receivers will not be high-end and will suffer from device specific impairments which affect the RF fingerprinting process. This paper evaluates the accuracy of RF fingerprinting employing low-end receivers. The vulnerability to an impersonation attack is assessed for a modulation-based RF fingerprinting system employing low-end commodity hardware (by legitimate and malicious users alike). Our results suggest that receiver impairment effectively decreases the success rate of impersonation attack on RF fingerprinting. In addition, the success rate of impersonation attack is receiver dependent.     

Development of a Hybrid Algorithm for Efficient Optimisation of Base Station Placement for Indoor Wireless Communication Systems

A new hybrid algorithm termed Reduction Estimation—Combinatorial Optimisation—Reduction Approximation is proposed to identify an optimal base station placement as a subset of a known set of potential sites to provide wireless communication services to a given set of stationary users. Both forward and reverse link signal-to-interference ratios are considered, and the performance of the proposed algorithm is reported for several representative case studies and compared with Brute Force Search and existing optimisation algorithms (including Genetic, Ngadiman and Greedy algorithms). For the cases considered, the proposed algorithm is found to be superior to the existing algorithms in that it can yield an optimal deployment (equivalent to Brute Force Search) in an acceptable time.     

The determination of optimum blank shapes when deep drawing prismatic cups

The article discusses some techniques for the determination of ideal (or optimum) blank contours when deep drawing prismatic cups. The ideal contours are designed to produce essentially flat topped cups and thus trimming of excess material is minimized. The techniques lend themselves to such processes where the cups are drawn from initially flat blanks in the presence of a blank holder. Tooling which involves lock beads or draw beads is not considered. Attention is devoted to two techniques developed by the authors; each method is based on the solution of Laplace’s equation. One technique is experimental and uses an electrostatic analogue, the second is numerical and the solution procedure employs the boundary element method. Neither method attempts a rigorous analysis of the actual drawing operation. They are intended as a means of producing near-net shaped blanks with little computational effort. Since material costs usually represent a major portion of the overall cost of a sheet metal part, the theme of the paper has immediate practical significance.     

A computational paradigm for space-time multiuser detection

In a general wireless system, cells are loosely defined and user signals appear at multiple antennas with various powers and delays. Despite the enormous performance benefits of system-wide maximum-likelihood multiuser detection (ML MUD), its application to such systems is hampered by the lack of a regular structure. Prior work usually dismisses the possibility on computational grounds as exponential in the total number of users, at least. This paper is the first to address efficient computation of system-wide ML MUD. We present a computational organization that achieves dramatic reduction in complexity through exploitation of the partial overlap of user sets at different antennas. This algorithm, which applies to code-division multiple access or narrowband systems, can be viewed as a spatio-temporal extension of the well-known Viterbi algorithm (VA), and, like the VA, it is derived from dynamic programming principles.     

Variability of forming limit curves

The forming limit curve indicates the maximum uniform strain which can be achieved in an element of a sheet which is strained in a proportional biaxial straining process; it refers to the strain in a region adjacent to, but not within, any area of localized straining associated with rupture. In this work forming limit curves were determined for four different grades of mild steel; gridded test pieces were stretch formed to failure in elliptical and circular hydrostatic bulge dies. Each test was repeated twenty times for each material and each die, in order to provide data for statistical investigation of scatter in measured forming limits. It is shown that the variation in forming limits is much greater than that due to the experimental error and it is proposed that this scatter reflects an intrinsic property of the material which is important in determining material formability. A three-dimensional forming limit diagram is presented which can be used to determine the probability of failure of an element which is stretch formed to a particular strain level. The experimental data are also employed to determine the number of tests required to determine the mean forming limit curve within a specified accuracy.     

An approximate analysis for studying the deformation mechanics of rate sensitive materials

To provide reliable predictions about a forming process it is necessary to have access to a realistic constitutive equation, a good estimate of the boundary conditions pertaining to the problem and a proven computational technique. This present article deals with this latter aspect and a numerical scheme is proposed for analysing the deformation of strain rate sensitive materials. The method of solution is an approximate one and employs a rate of energy functional which is applicable to a certain class of strain rate sensitive materials. The functional is minimised with respect to a kinematically admissible velocity field and is used in a discretized form in a finite element analysis. The functional is similar to an energy functional proposed by Lee and Kobayashi for a rate insensitive, rigid-plastic material.To test the theoretical technique two simple deformation processes were considered namely, the expansion of a thin walled spherical shell under internal pressure and the uniaxial deformation of a prismatic bar under its own weight. Exact solutions to these problems can be obtained based on a material constitutive equation of the type: . The computational technique based on the minimization of the proposed functional gave excellent agreement. To provide a more practical application of the method the following problems were considered. The expansion of a circular hole in a square plate, the deformation in the flange when drawing circular cups from square and octagonal plates and the tube drawing (and sinking) process. The examples serve to illustrate the flexibility of the method and the results of the analysis appear promising. However, since little information exists about the behaviour of superplastic alloys in these processes then it is difficult to infer anything about the “accuracy” of the predictions.     

The Influence of the Zinc Phosphate Coating on the coefficient of friction when cold heading AISI 1018 steel wire

A Waterbury-Farrel cold heading machine was instrumented so that the total force and frictional force could be recorded during the first blow operation of AISI 1018 steel wire and the efficiency of various lubricants, including zinc phosphate, was evaluated. Zinc phosphate and other bonded lubricants did not offer any distinct advantage in reducing the coefficient of friction between the wire and the central bore of the first blow punch whereas a low cost liquid lubricant, SAE 30 oil, used either alone on bare wire or with bonded lubricants proved to be the most effective. It is suggested that a low cost liquid lubricant, such as SAE 30 oil, used on bare wire has both economic and operational advantages under conditions where no extrusion is carried out during the first blow.     

Outage probability calculations for mobile radio systems withmultiple interferers

Outage probability calculations are presented for the case when the transmission from a wanted base station is received by a mobile in the presence of multiple cochannel interfering signals for the case where the transmissions suffer both log-normal shadowing and Rayleigh fading. The calculations consider the need to achieve simultaneously both a sufficient SNR and SIR to obtain satisfactory radio reception     

Balancing energy efficiency and spectrum efficiency for lower error rate in bidirectional relay networks

A scheme for combining data rate, energy efficiency and relay location in bidirectional amplify-and-forward relay networks is proposed in this paper. The proposed scheme allows the energy consumption to be evaluated for all positions of a chosen relay along a line between the transmitter and the destination. Furthermore, the evaluated energy reduction is used to obtain the optimal balance between the energy efficiency (EE) and spectrum efficiency (SE). This balance enables the EE to increase significantly with the least loss of SE. Such a balance is then expressed with respect to the bit error rate. Numerical examples are provided to validate the analysis.

     

Interference Analysis of an in-Building Wireless Communication System Employing Vertical Frequency Reuse

The reception quality of an interference limited indoor wireless communication system employing vertical frequency reuse is analysed. Outage probability expressions are used to measure the level of cochannel interference. The received signals are assumed to suffer the effects of Rayleigh fading and log-normal shadowing and multiple cochannel interferers are included in the analysis. The expected reception qualities are studied in a range of buildings and the results show that typically a vertical reuse distance of 3 floors will not isolate cochannel floors sufficiently to allow reliable reception. For one building analysed, even a vertical reuse distance of five floors is not likely to result in sufficiently low levels of cochannel interference. When multiple interferers are considered, it is not a straight forward task to determine the number of cochannel interferers that contribute significant interference since this may depend on the propagation conditions in a particular building.