Search

In future 5G systems, the millimeter wave (mmWave) band will be used to support a large capacity for current mobile broadband. Therefore, the radio access technology (RAT) should be made available for 5G devices to help in distinct situations, for example device-to-device communications (D2D) and multi-hops. This paper presents ultra-wideband channel measurements for millimeter wave bands at 19, 28, and 38 GHz. We used an ultra-wideband channel sounder (1 GHz bandwidth)in an indoor to outdoor (I2O) environment for non-line-of-sight (NLOS) scenarios. In an NLOS environment, there is no direct path (line of sight), and all of the contributed paths are received from different physical objects by refection propagation phenomena. Hence, in this work, a directional horn antenna (high gain) was used at the transmitter, while an omnidirectional antenna was used at the receiver to collect the radio signals from all directions. The path loss and temporal dispersion were examined based on the acquired measurement data-the 5G propagation characteristics. Two different path loss models were used, namely close-in (CI) free space reference distance and alpha-beta-gamma (ABG) models. The time dispersion parameters were provided based on a mean excess delay, a root mean square (RMS) delay spread, and a maximumexcess delay. The path loss exponent for this NLOS specific environment was found to be low for all of the proposed frequencies, and the RMS delay spread values were less than 30 ns for all of the measured frequencies, and the average RMS delay spread values were 19.2, 19.3, and 20.3 ns for 19, 28, and 38 GHz frequencies, respectively. Moreover, the mean excess delay values were found also at 26.1, 25.8, and 27.3 ns for 19, 28, and 38 GHz frequencies, respectively. The propagation signal through the NLOS channel at 19, 28, and 38 GHz was strong with a low delay; it is concluded that these bands are reliable for 5G systems in short-range applications.

This paper analyses the performances of the Infinite Impulse Response (IIR) and Finite Impulse Response (FIR) filters. By studying the relationship between filter responses with filter orders and delay, the goal is to choose feasible filters that can accommodate more carriers in a bandwidth thus, the spectral efficiency can be increased. For IIR filtering, we employ filters namely Butterworth, Chebyshev, and Elliptic, while the Equiripple, Bohman, and Hamming are studied for FIR filtering. We evaluate these filters in terms of magnitude response, phase response and group delay, and identify the minimum filter order that characterized nearly to an ideal filter response. The results show that the IIR filter has a steep transition region when compared to the FIR filters under the similar order. Our performance analysis showed that the IIR filters, with similar filter order of FIR filters, have also the fastest roll-off, small transition region, and low implementation cost. On the other hand, the FIR filters have linear phase response that related to group delay. Finally, our analysis concluded that Elliptic able to suppress the sidelobes with a minimum order of 10th  and Equiripple have the fastest roll-off and narrowest transition region compare to other tested FIR filter. Thus, make these two types of filter feasible candidates to be implemented in 5G wireless networks.

Recent breakthroughs in forward error correction, in the form of low-density parity-check (LDPC) and turbo codes, have seen near Shannon limit performances especially for pointto-point channels. The construction of capacity-achieving codes in relay channels, for LDPC codes in particular, is currently the subject of intense interest in the researchand development community. This thesis adds to this field, developing methods and supporting theory in designing capacity-achieving LDPC codes for decode-and-forward (DF) schemes in relay channels.In the first part of the thesis, new theoretical results toward optimizing the achievable rate of DF scheme in half-duplex relay channels under simplified and pragmatic conditions (equal power or equal time allocation) are developed. We derive the closed-form solutions for the optimum parameters (time or power) that maximize the achievable rates of theDF scheme in the half-duplex relay channel. We also derive the closed-form expressionfor the DF achievable rates under these simplified and pragmatic conditions.The second part of the thesis is dedicated to study the problem of designing several classesof capacity-achieving LDPC codes in relay channels. First, a new ensemble of LDPC codes,termed multi-edge-type bilayer-expurgated LDPC (MET-BE-LDPC) codes, is introducedto closely approach the theoretical limit of the DF scheme in the relay channel. We proposetwo design strategies for optimizing MET-BE-LDPC codes; the bilayer approach andthe bilayer approach with intermediate rates. Second, we address the issue of constructingcapacity-achieving distributed LDPC codes in the multiple-access and two-way relay channels,with broadcast transmissions and time-division multiple accesses. We propose a new methodology to asymptotically optimize the code’s degree distribution when different segmentswithin the distributed codeword have been transmitted through separate channelsand experienced distinct signal-to-noise ratio in the relay syste