Marwan Hadri Azmi

Statistical Modelling and Characterization of Experimental mm-Wave Indoor Channels for Future 5G Wireless Communication Networks.

This paper presents an experimental characterization of millimeter-wave (mm-wave) channels in the 6.5 GHz, 10.5 GHz, 15 GHz, 19 GHz, 28 GHz and 38 GHz frequency bands in an indoor corridor environment. More than 4,000 power delay profiles were measured across the bands using an omnidirectional transmitter antenna and a highly directional horn receiver antenna for both co- and cross-polarized antenna configurations. This paper develops a new path-loss model to account for the frequency attenuation with distance, which we term the frequency attenuation (FA) path-loss model and introduce a frequency-dependent attenuation factor. The large-scale path loss was characterized based on both new and well-known path-loss models. A general and less complex method is also proposed to estimate the cross-polarization discrimination (XPD) factor of close-in reference distance with the XPD (CIX) and ABG with the XPD (ABGX) path-loss models to avoid the computational complexity of minimum mean square error (MMSE) approach. Moreover, small-scale parameters such as root mean square (RMS) delay spread, mean excess (MN-EX) delay, dispersion factors and maximum excess (MAX-EX) delay parameters were used to characterize the multipath channel dispersion. Multiple statistical distributions for RMS delay spread were also investigated. The results show that our proposed models are simpler and more physically-based than other well-known models. The path-loss exponents for all studied models are smaller than that of the free-space model by values in the range of 0.1 to 1.4 for all measured frequencies. The RMS delay spread values varied between 0.2 ns and 13.8 ns, and the dispersion factor values were less than 1 for all measured frequencies. The exponential and Weibull probability distribution models best fit the RMS delay spread empirical distribution for all of the measured frequencies in all scenarios.

LDPC codes for soft decode-and-forward in half-duplex relay channels

We investigate the use of rate-compatible low-density parity-check (RC-LDPC) codes as part of a soft decode-and-forward (SDF) protocol over the half-duplex relay channel. We propose a new methodology to design the degree distribution of the RC-LDPC codes with a lower triangular parity-check matrix, enabling the additional parity bits to be linearly and systematically encoded at the relay. Our proposed methodology introduces the concept of a K-layer doping matrix to represent the structure of a lower triangular parity-check matrix. As a result of our methodology, the asymptotic performance of RC-LDPC codes can be analyzed and predicted using the multi-edge-type density evolution. Then, we derive the soft-re-encoding of the additional parity symbols at the relay using our designed RC-LDPC codes. Moreover, we propose a novel method, which we refer to as soft fading, to compute the log-likelihood ratio (LLR) of the received signal at the destination for the SDF protocol. We demonstrate that our proposed soft fading method outperforms the best known method in the literature by up to 0.7 dB in terms of BER performance. Finally, we derive a new bound for the power multiplication factor at the relay, which limits the amount of soft-errors forwarded by the relay to the destination. The BER performance of our new RC-LDPC codes improves significantly once the power multiplication factor at the relay satisfies this bound.

Window-based channel impulse response prediction for time-varying ultra-wideband channels

This work proposes channel impulse response (CIR) prediction for time-varying ultra-wideband (UWB) channels by exploiting the fast movement of channel taps within delay bins. Considering the sparsity of UWB channels, we introduce a window-based CIR (WB-CIR) to approximate the high temporal resolutions of UWB channels. A recursive least square (RLS) algorithm is adopted to predict the time evolution of the WB-CIR. For predicting the future WB-CIR tap of window wk, three RLS filter coefficients are computed from the observed WB-CIRs of the left wk−1, the current wk and the right wk+1 windows. The filter coefficient with the lowest RLS error is used to predict the future WB-CIR tap. To evaluate our proposed prediction method, UWB CIRs are collected through measurement campaigns in outdoor environments considering line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios. Under similar computational complexity, our proposed method provides an improvement in prediction errors of approximately 80% for LOS and 63% for NLOS scenarios compared with a conventional method.

Indoor Corridor Wideband Radio Propagation Measurements and Channel Models for 5G Millimeter Wave Wireless Communications at 19 GHz, 28 GHz, and 38 GHz Bands

This paper presents millimeter wave (mmWave) measurements in an indoor environment. The high demands for the future applications in the 5G system require more capacity. In the microwave band below 6u2009GHz, most of the available bands are occupied; hence, the microwave band above 6u2009GHz and mmWave band can be used for the 5G system to cover the bandwidth required for all 5G applications. In this paper, the propagation characteristics at three different bands above 6u2009GHz (19, 28, and 38u2009GHz) are investigated in an indoor corridor environment for line of sight (LOS) and non-LOS (NLOS) scenarios. Five different path loss models are studied for this environment, namely, close-in (CI) free space path loss, floating-intercept (FI), frequency attenuation (FA) path loss, alpha-beta-gamma (ABG), and close-in free space reference distance with frequency weighting (CIF) models. Important statistical properties, such as power delay profile (PDP), root mean square (RMS) delay spread, and azimuth angle spread, are obtained and compared for different bands. The results for the path loss model found that the path loss exponent (PLE) and line slope values for all models are less than the free space path loss exponent of 2. The RMS delay spread for all bands is low for the LOS scenario, and only the directed path is contributed in some spatial locations. For the NLOS scenario, the angle of arrival (AOA) is extensively investigated, and the results indicated that the channel propagation for 5G using high directional antenna should be used in the beamforming technique to receive the signal and collect all multipath components from different angles in a particular mobile location.

Path loss model for outdoor environment at 17 GHz mm-wave band

This paper presents the path loss model for 17 GHz mm-Wave frequency spectrum. The millimeter-wave spectrum has been proposed for future high speed 5G cellular systems with large bandwidth requirement. Since this proposal, propagation studies characterizing and investigating the potential of mm-Wave spectrum have been aggressively performed. This work conducts measurement campaign to derive a path loss models for outdoor environment in line-of-sight (LOS) scenarios at 17 GHz mm-Wave frequency spectrum. The derived models are based on the log-normal shadowing model. The path loss exponent for the derived path loss models is 2.3, which indicates that the chosen outdoor environment is an open environment like free space. Comparison between the values of path loss provided by the measured data, the derived path loss model and the free space model is made. The differences between the path loss value from the measured data and the derived path loss model is 7dB, while 13 dB differences is found when comparing the measured data and the free space loss model.

Channel characterization for indoor environment at 17 GHz for 5G communications

The increasing demand for the extremely-high capacity and connectivity in wireless communication systems has motivated the researchers to explore the fifth-generation (5G) mobile communication. Owing to the wide bandwidth demand to increase the capacity, current spectrum bands below 6 GHz allocated for cellular mobile communication are congested and insufficient to support the services envisioned for 5G. Therefore, extensive on-going studies are investigating the feasibility to implement 5G systems at frequency above 6 GHz. In this paper, the propagation path loss at 17 GHz in indoor environment is characterized through series of continuous-wave channel measurements. Measurement results in typical Malaysian indoor propagation environment for both line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios are presented.

A Survey of Millimeter Wave (mm-Wave) Communications for 5G: Channel Measurement Below and Above 6 GHz

As the demand for higher speed data transmissions continues to increase exponentially beyond the speed-limit of the fourth generation (4G) wireless networks due to the rapid spectrum depletion of the microwave frequency bands below 6 GHz, it has become quite evident that the existing wireless communication systems will eventually be constrained from meeting the huge throughput requirements for various emerging applications beyond 4G wireless networks. In order to sustain the future market dominance of wireless communications, the narrowness of wireless bandwidths in the existing systems, which has become a key issue for the upcoming wireless systems, needs to be addressed by looking beyond the traditional microwave spectrum domain through the exploitation of the huge bandwidths available in the millimeter wave bands. In this work, we have conducted the review for a series of measurements at various microwave bands, below 6 GHz and above, to study the behavior of ultra-wideband (UWB) channels, typically in different indoor and outdoor environments. These measurements have been used to gain a useful insight into the path loss and time dispersion parametric behaviors of the 5G channel and to investigate the channel characterization of the UWB signals within spatially restricted locations. Moreover, these measurements have been used to evaluate the newest channel model and channel prediction which have proposed for 5G.