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Joint transmission across the cluster of radio remote heads (RRHs) by exploiting the centralized processing of the cloud-radio access network (C-RAN) is a promising technique to overcome the severe interference problems in ultra-dense small cell networks. In practical considerations, local clustering of networks is preferred over global clustering as the number of RRHs that can be jointly transmitted on the network is finite. In this study, we attempt to revisit the principles of the well-known affinity propagation (AP) clustering algorithms, especially for the naive method of determining the exemplar with a fixed threshold. To further explain the decision method, we propose a method to easily determine the threshold using the network map of converged value of messages generated by AP algorithm, by combining Otsu’s threshold and density peak searching method with the existing AP clustering algorithm. The proposed algorithm provides higher spectral efficiency than the conventional AP algorithms as well as statically coordinated multi-point (CoMP) techniques, although it has similar execution time as the traditional AP algorithms.

In 2015, the international telecommunication union (ITU) proposed 11 candidate millimeter-wave bands between 24 and 86 GHz for the deployment of future fifth mobile generation (5G) broadband systems. Furthermore, the ITU called for spectrum-sharing studies in these bands. Since 5G specifications are not yet defined, the utilization of radio spectrum by 5G mobile systems will assist in identifying these specifications. This paper introduces Malaysia as a case study for the deployment of 5G systems. This includes a discussion of the current status of the Malaysian telecommunication market. Then, we investigate the current services that are already deployed in the proposed bands. Our investigation shows that the fixed (F) service is the most deployed as a primary service in the candidate bands. For this reason, a preliminary spectrum-sharing study is conducted on the basis of a modified 5G spectrum-sharing model to evaluate the feasibility of coexistence between 5G and F services in the 28-GHz band. Our modified methodology can be used for spectrum-sharing studies between 5G and any other services for an initial spectrum-sharing investigation. The results show that the F service will be severely affected by the 5G system transition in the 28-GHz band, especially in the base station (BS)-to-BS sharing scenario. The best band from the perspective of current spectrum allocation for 5G systems is the 45-GHz (i.e., 45.5–47 GHz) band, since it is already reserved for mobile service for primary allocation and not utilized. This paper is carried out concurrently with current worldwide efforts investigating spectrum sharing, as requested by the ITU in agenda item 1.13 for the next world radio conference 2019.

Earth station in motion (ESIM) is a technology that provides wireless communication to users at their locations and is considered to operate at 27.5-29.5 GHz. The next-generation mobile communication service, 5G, is expected to operate at 24.25-27.5 GHz. These systems can experience interference because both the frequency bands are contiguous. The possibility of the adjacent channel compatibility between an ESIM and 5G should be verified by an interference analysis. However, ESIMs are mounted on ships, aircraft, and land vehicles. Therefore, the analysis methods and scenarios should be applied differently. We propose orthogonal frequency division multiplexing (OFDM) waveforms of an ESIM for their coexistence. Because OFDM has a lower out-of-band emission (OOBE) than a single carrier signal, this proposed approach can save frequency resources. Minimum coupling loss (MCL) and Monte Carlo (MC) methods are used to obtain the minimum separation distance and guard band according to the frequency-dependent rejection for determining the adjacent channel compatibility.

We propose a modeling method to calculate the interference that existing satellite services receive from fifth-generation mobile communication systems (IMT-2020). This study is based on the modeling and parameter document proposed for spectrum sharing research provided in the ITU- recommendation for IMT-2020 services in the millimeter-wave band. To complement previous research, we expand the coverage area from the footprint area to entire area by considering side lobe of satellites. In addition, we obtain various results depending on the location and main lobe direction of the satellite by using terrain data. Furthermore, we use this modeling method to calculate the interference that the Fixed-Satellite Service (FSS) satellite and Earth Exploration- Satellite Service (EESS) passive sensor receive in the co-channel and adjacent channel and compare that with protection criteria to present the possibility of frequency coexistence.

The optimal number of clusters (K) differs depending on the radio remote head (RRH) density. This paper verifies that the K values cannot be met by the conventional affinity propagation (AP) clustering algorithm. In an ultra-dense network (UDN) environment, the density of RRH is a very important factor for the bender because it is directly related to the cost of configuring the wireless communication network. Likewise, in order to provide the optimal communication environment to the user in the UDN environment, it is necessary to enable flexible clustering according to changing channel environment by utilizing semi-dynamic clustering technology. As a result, we propose an AP algorithm that finds a better K value than the conventional method. To this end, the proposed algorithm additionally utilizes a non-coordinated multi-point (CoMP) interference power that varies depending on the RRH density, user position, and the variations in propagation channel. The simulation results show that the proposed algorithm shows a better average capacity than the conventional algorithm.

In this paper, we propose a channel estimation method based on a complex valued regression of the neural network for the IEEE 802.11p standard. It consists of the complex weighted summation optimized by feedforward neural network with backpropagation algorithm using initial estimated channel of the pilot and the long preamble. It also exploits the shift matrix in order to mitigate the effect from a systemic problems in IEEE 802.11p standards. The major problems of IEEE 802.11p standard are wide bandwidth of 10 MHz consisting of 64 subcarriers and relatively insufficient four pilot subcarriers at single ODFM symbol, which are unsuitable for a channel of vehicular environment. Despite these problems, the proposed method performs better than the conventional channel estimation methods. The performance of proposed scheme is provided with the comparison between constructed data pilots (CDP), Spectral Temporal Averaging (STA), and proposed scheme. The proposed channel estimation scheme has low mean square error (MSE) and bit error rate (BER) throughout the whole SNR region. It is the result from properly trained weight. At the low SNR region, especially, the performance of proposed scheme is much better than CDP and STA scheme. It is because of the noise suppression effect caused by a weighted summation algorithm.

Earth station in motion (ESIM) service is an advanced satellite service and its demand is increasing around the world. 5G mobile service (IMT-2020) is also one of the most demanding systems in the world. As ESIM uplink will operate in 27.5-29.5 GHz band that is contiguous to a candidate band for 5G mobile service, both services should be confirmed for the possibility of adjacent channel compatibility. In this paper, we propose methods to analyze the adjacent channel interference from maritime ESIM to 5G mobile service. Minimum coupling loss (MCL) and Monte Carlo (MC) methods are used to obtain the minimum separation distance and the adjacent channel interference ratio (ACIR) required for the adjacent channel compatibility, and the throughput loss of 5G up and downlink for given separation distance and ACIRs. Various feasible solutions as well as the worst requirements are provided.

In this paper, we investigate the possibility of spectral coexistence of the two services through the analysis of interference potential between IMT-2020 and fixed-satellite service (FSS) uplink in the 27-27.5 GHz frequency band. We model and calculate the interference power at victim receivers referring to up-to-date ITU-R documents and compare them with the protection criteria of the victim receivers. Furthermore, three-dimensional (3D) topographic data with latitude/longitude/altitude coordinates are adopted to exactly model the interference power aggregated from a large number of terrestrial IMT-2020 systems in worldwide areas. The results show that the FSS space station is safe from the aggregated IMT-2020 interference, and the IMT-2020 service can be protected when base station (BS) and user equipment (UE) are located 3.3 and 0.9 km away from the FSS earth station.

Spectrum sharing is an elegant solution to the problem of spectrum scarcity. A novel advanced approach is developed in this study to enable power-controlled cellular networks coexist with primary rotating radars. A canonical scenario is considered where a single cellular BS interferes with single rotating radar. A new mathematical model is also developed using log-normal approximations to capture the aggregate interference from multiple power-controlled cellular systems. The cellular system transmits at high power for over 83.3% of time due to the slow radar antenna rotation and narrow main beam width. Our numerical results show that the power control drastically reduces the required separation distances between the two systems. The log-normal approximation gives results which virtually match the results of our simulation.

Polarization division multiple access (PDMA) is a method to simultaneously transmit two independent signals by using vertical and horizontal polarization in the same frequency band. In PDMA systems, the received signal can experience significant interference from cross-polarized signals if the transmit and receive antennas are misaligned in terms of polarization state. In this paper, a precoding technique to solve this problem is discussed and a channel model to disentangle vertical and horizontal components from the received signal and include the rotation of receive antenna is proposed. The precoding technique is designed and analyzed using a channel model assuming a line-of-sight environment. To measure the performance of the precoding technique, a testbed is implemented using a software-defined radio platform. Simulation and measurement show that enhanced channel gain is achieved even when the polarization state between the transmit and receive antennas is mismatched. Comparison between simulation and measurements proves a basic and crucial principle concerning the capability of controlling the polarization state of a transmitted signal.

The present study examined neural activations during the positive affective state by Functional magnetic resonance images (fMRI) as participants viewed pictures of “achievements” (positive arousal) and “connectedness” (positive valence). The theoretical model of affective structure is related to explain positive affective state. We hypothesized that positive affect on two different dimensions would engage participants in distinct happiness states. 22 undergrad/grad participants performed rating the subjective experience of happiness during positive affective state by the presented photos (i.e. connectedness, achievement and neutral). Across analyses, we found a set of neural regions that support an empathic state and positive affective state. A brain activity of cognitive-evaluative system is engaged when participants view “achievement” stimuli. In contrast, affective- perceptual form of empathy is engaged for “connectedness” stimuli. In addition, cognitive-evaluative neural activation was highly correlated with the strength of perceived happiness, whereas affective-perceptual related neural regions showed no correlation. Taken together, our results provide evidence to suggest that there are integrative neuro-cognitve networks supporting the processing of positive affect where activated in functionally and anatomically dissociable patterns.

Full dimension multiple input multiple output (FD-MIMO) employs 2-dimensional (2D) active antenna array configurations at the transmitter along with advanced digital processing to improve capacity for next generation wireless networks and services. This technology can achieve multi user MIMO (MU-MIMO) of high magnitude via the provision of simultaneous data transmission to large number of user equipments (UEs) in the network. It is quite clear that shifting from the conventional MIMO to FD-MIMO would require a change in base station designs, but the question remains; which designs provide the optimal performance? In this paper, we present results from a study of the impact of angular spread on throughput for a planar array system. By means of simulations, evaluations are performed to aid the understanding of antenna configuration for optimal performance. In order to demonstrate the potential performance benefits of FD-MIMO, simulations were performed with a detailed dynamic simulator which includes a 3-Dimensional Spatial Channel Model (3D SCM). Our results show that a square grid planar array with higher elevation angular spread can provide vast improvements in terms of throughput gain over conventional horizontal linear configuration.

In this paper we develop a tractable framework for SINR analysis in downlink heterogeneous cellular networks (HCNs) with flexible cell association. The HCN is modeled as a multi-tier cellular network where each tier's base stations (BSs) are randomly located and have a unique transmit power, path loss exponent, spatial density, and bias towards admitting users. We implicitly assume every BS has full queues. From this model, we derive the outage probability of a typical user in the network, which can be viewed as a spatial average of SINR over all users in the network. We observe that deploying more or less BSs does not change the outage probability in interference-limited HCN with unbiased cell association, and observe how biasing affects the metric.

A fundamental choice in femtocell deployments is the set of users which are allowed to access each femtocell. Closed access restricts the set to specifically registered users, while open access allows any mobile subscriber to use any femtocell. The main results of the paper are lemmas which provide expressions for the SINR distribution for various zones within a cell as a function of this MBS-femto distance. The average sum throughput (or any other SINR-based metric) of home and cellular users under open and closed access can be readily determined from these expressions. We show that unlike in the uplink, the interests of home and cellular users are in conflict, with home users preferring closed access and cellular users preferring open access. The conflict is most pronounced for femtocells near the cell edge, when there are many cellular users and fewer femtocells.

This paper proposes two interference mitigation strategies that adjust the maximum transmit power of femtocell users to suppress the cross-tier interference at a macrocell base station (BS). The open-loop and the closed-loop control suppress the cross-tier interference less than a fixed threshold and an adaptive threshold based on the noise and interference (NI) level at the macrocell BS, respectively. Simulation results show that both schemes effectively compensate the uplink throughput degradation of the macrocell BS and that the closed-loop control provides better femtocell throughput than the open-loop control at a minimal cost of macrocell throughput.

In this paper, we propose an efficient and robust interference mitigation technique based on a nullsteering multiuser multiple-input multiple-output (MU-MIMO) spatial division multiple access (SDMA) scheme for frequency sharing between IMT-Advanced and fixed satellite service (FSS). In the proposed technique, the conventional precoding matrix for SDMA unitary preceded (UPC) MIMO proposed by the authors is modified to construct nulls in the spatial spectrum corresponding to the direction angles of the victim FSS earth station (ES). The frequency sharing results are given in terms of interference power and minimum separation distance in the co-channel. Simulation results shows that our mitigation technique reduces interfering power by about 60 dB and can meet the maximum permissible interference power condition in almost separation distances. Therefore it can be concluded that the proposed mitigation technique in this paper is highly efficient in terms of reducing the separation distance as well as robust against DOE estimation errors.

In this paper, the advanced general analytical method, namely advanced minimum coupling loss (A-MCL) method is proposed. The A-MCL method utilizes a power spectral density (PSD) analysis, and bears two advantages, compared to the conventional minimum coupling loss (MCL) method. First, it can calculate out of band emissions from the orthogonal frequency-division multiplexing (OFDM)-based systems beyond 3G (B3G) without a spectrum emission mask. Secondly, it can be applicable to coexistence analysis of OFDM-based systems using a dynamic power allocation scheme with other systems. Moreover, interference power is derived in a closed form, rendering easy and straightforward calculations.