Complex Block Floating-Point Format with Box Encoding For Wordlength Reduction in Communication Systems

We propose a new complex block floating-point format to reduce implementation complexity. The new format achieves wordlength reduction by sharing an exponent across the block of samples, and uses box encoding for the shared exponent to reduce quantization error. Arithmetic operations are performed on blocks of samples at time, which can also reduce implementation complexity. For a case study of a baseband quadrature amplitude modulation (QAM) transmitter and receiver, we quantify the tradeoffs in signal quality vs. implementation complexity using the new approach to represent IQ samples. Signal quality is measured using error vector magnitude (EVM) in the receiver, and implementation complexity is measured in terms of arithmetic complexity as well as memory allocation and memory input/output rates. The primary contributions of this paper are (1) a complex block floating-point format with box encoding of the shared exponent to reduce quantization error, (2) arithmetic operations using the new complex block floating-point format, and (3) a QAM transceiver case study to quantify signal quality vs. implementation complexity tradeoffs using the new format and arithmetic operations.Comment: 6 pages, 9 figures, submitted to Asilomar Conference on Signals, Systems, and Computers 201

Interactive solution-adaptive grid generation

TURBO-AD is an interactive solution-adaptive grid generation program under development. The program combines an interactive algebraic grid generation technique and a solution-adaptive grid generation technique into a single interactive solution-adaptive grid generation package. The control point form uses a sparse collection of control points to algebraically generate a field grid. This technique provides local grid control capability and is well suited to interactive work due to its speed and efficiency. A mapping from the physical domain to a parametric domain was used to improve difficulties that had been encountered near outwardly concave boundaries in the control point technique. Therefore, all grid modifications are performed on a unit square in the parametric domain, and the new adapted grid in the parametric domain is then mapped back to the physical domain. The grid adaptation is achieved by first adapting the control points to a numerical solution in the parametric domain using control sources obtained from flow properties. Then a new modified grid is generated from the adapted control net. This solution-adaptive grid generation process is efficient because the number of control points is much less than the number of grid points and the generation of a new grid from the adapted control net is an efficient algebraic process. TURBO-AD provides the user with both local and global grid controls

MAG3D and its application to internal flowfield analysis

MAG3D (multiblock adaptive grid, 3D) is a 3D solution-adaptive grid generation code which redistributes grid points to improve the accuracy of a flow solution without increasing the number of grid points. The code is applicable to structured grids with a multiblock topology. It is independent of the original grid generator and the flow solver. The code uses the coordinates of an initial grid and the flow solution interpolated onto the new grid. MAG3D uses a numerical mapping and potential theory to modify the grid distribution based on properties of the flow solution on the initial grid. The adaptation technique is discussed, and the capability of MAG3D is demonstrated with several internal flow examples. Advantages of using solution-adaptive grids are also shown by comparing flow solutions on adaptive grids with those on initial grids

Interactive solution-adaptive grid generation procedure

TURBO-AD is an interactive solution adaptive grid generation program under development. The program combines an interactive algebraic grid generation technique and a solution adaptive grid generation technique into a single interactive package. The control point form uses a sparse collection of control points to algebraically generate a field grid. This technique provides local grid control capability and is well suited to interactive work due to its speed and efficiency. A mapping from the physical domain to a parametric domain was used to improve difficulties encountered near outwardly concave boundaries in the control point technique. Therefore, all grid modifications are performed on the unit square in the parametric domain, and the new adapted grid is then mapped back to the physical domain. The grid adaption is achieved by adapting the control points to a numerical solution in the parametric domain using control sources obtained from the flow properties. Then a new modified grid is generated from the adapted control net. This process is efficient because the number of control points is much less than the number of grid points and the generation of the grid is an efficient algebraic process. TURBO-AD provides the user with both local and global controls

A Question of ‘Desirability’: Balancing and Improperly Obtained Evidence in Comparative Perspective

Debates about improperly obtained evidence continue to arise in common law appellate courts on a surprisingly regular basis. In 2015, the Irish Supreme Court handed down a decision on the topic which ran to over 155,000 words. Among the major common law jurisdictions outside the United States, Australia can be regarded as something of a pioneer in its approach to the admissibility of illegally or otherwise improperly obtained evidence. In 1978 the High Court of Australia in Bunning v Cross, building on its earlier decision in R v Ireland, established the existence of a discretion to exclude such evidence that was distinct from the discretion to exclude evidence to ensure fairness to a defendant at trial. Section 138 of the UEL, the focus of this chapter, was closely modelled on this common law jurisprudence. At the time of Bunning, the law in England and Wales was characterised by little judicial analysis of the issue of improperly obtained evidence, and Canada was still some years away from introducing the Canadian Charter of Rights and Freedoms with its well-known provision on evidence obtained in consequence of Charter violations. In the light of major continuing developments in the common law world in this area of evidence law, this chapter seeks to provide a searching and timely analysis of selected aspects of section 138, as viewed from the perspective of an evidence scholar working in England and Wales, with the aim of asking what lessons may be learnt from a contemporary comparison of section 138 with the approaches taken to improperly obtained evidence in other common law jurisdictions. The chief focus will be on the particular species of evidence that can be considered to highlight most clearly the relevant theoretical and practical issues raised by improperly obtained evidence—evidence that was not brought into fruition by any interaction between a member, or agent, of the executive and a suspect. In other words, the improprieties that will be the primary concern of this chapter are those that do not contribute in some way to the generation of the evidence in question; the situations are such that there is no suspicion that evidence of doubtful reliability or veracity has been produced by the impropriety. So, for example, within the primary scope of the chapter will be evidence obtained as a result of an illegal search, or evidence obtained by improper means of ‘spontaneous’ conversations that were not in some way induced by the conduct of the executive. Outside the primary scope of the chapter will be evidence obtained improperly during formal police interrogations, or ‘informal’ interrogations involving the covert questioning of a suspect by a police agent