An Efficient FPGA-Based Frequency Shifter for LTE/LTE-A Systems

The Physical Random Access Channel plays an important role in LTE and LTE-A systems. Through this channel, the user equipment aligns its uplink transmissions to the eNodeB’s uplink and gains access to the network. One of the initial operations executed by the receiver at eNodeB side is the translation of the channel’s signal back to base-band. This operation is a necessary step for preamble detection and can be executed through a time-domain frequency-shift operation. Therefore, in this paper, we present the hardware architecture and design details of an optimised and configurable FPGA-based time-domain frequency shifter. The proposed architecture is based on a customised Numerically Controlled Oscillator that is employed for creating complex exponential samples using only plain logical resources. The main advantage of the proposed architecture is that it completely removes the necessity of saving in memory a huge number of long complex exponentials by making use of a Look-Up Table and exploiting the quarter-wave symmetry of the basis waveform. The results demonstrate that the proposed architecture provides high Spurious Free Dynamic Range signals employing only a minimal number of FPGA resources. Additionally, the proposed architecture presents spur-suppression ranging from 62.13 to 153.58 dB without employing any correction

Multiresolution Model For Image Interpolation With Adaptive Filtering

This paper proposes an image interpolation model based on a multiresolution scheme. The method uses two different known image resolutions to establish a mapping between them. The mapping is then used to extrapolate the unknown resolution to produce an expanded image with increased definition and with a mean square reconstruction error lower than for the conventional methods. In other words, details in a high resolution image are implicitly predicted based only on its low-frequency resolutions. A high subjective quality is obtained due to the similar nature of the mappings, which are constructed by means of an adaptive bidimensional FIR filter.42203220