Cellular Vehicle-to-Everything communication is an important scenario of 5G technologies. Modes 3 and 4 of the wireless systems introduced in Release 14 of 3GPP standards are intended to support vehicular communication with and without cellular infrastructure. In the case of Mode 3, dynamic resource selection and semi-persistent resource scheduling algorithms result in a signalling cost problem between vehicles and infrastructure, therefore, we propose a means to decrease it. This paper employs Re-selection Counter in centralized resource allocation as a decremental counter of new resource requests. Furthermore, two new spectrum re-partitioning and frequency reuse techniques in Roadside Units (RSUs) are considered to avoid resource collisions and diminish high interference impact via increasing the frequency reuse distance. The two techniques, full and partial frequency reuse, partition the bandwidth into two sub-bands. Two adjacent RSUs apply these sub-bands with the Full Frequency Reuse (FFR) technique. In the Partial Frequency Reuse (PFR) technique, the sub-bands are further re-partitioned among vehicles located in the central and edge parts of the RSU coverage. The sub-bands assignment in the nearest RSUs using the same sub-bands is inverted concerning the current RSU to increase the frequency reuse distance. The PFR technique shows promising results compared with the FFR technique. Both techniques are compared with the single band system for different vehicle densities.
The growing demands for mobile broadband application services along with the scarcity of the spectrum have triggered the dense utilization of frequency resources in cellular networks. The capacity demands are coped accordingly, however at the detriment of added inter-cell interference (ICI). Fractional Frequency Reuse (FFR) is an effective ICI mitigation approach when adopted in realistic irregular geometry cellular networks. However, in the literature optimized spectrum resources for the individual users are not considered. In this paper Hungarian Mechanism based Sectored Fractional Frequency Reuse (HMS-FFR) scheme is proposed, where the sub-carriers present in the dynamically partitioned spectrum are optimally allocated to each user. Simulation results revealed that the proposed HMS-FFR scheme enhances the system performance in terms of achievable throughput, average sum rate, and achievable throughput with respect to load while considering full traffic.
This work explores interference coordination techniques (inter-cell interference coordination, ICIC) based on fractional frequency reuse (FFR) as a solution for a multi-cellular scenario with user concentration varying over time. Initially, we present the problem of high user concentration along with their consequences. Next, the use of multiple-input multiple-output (MIMO) and small cells are discussed as classic solutions to the problem, leading to the introduction of fractional frequency reuse and existing ICIC techniques that use FFR. An exploratory analysis is presented in order to demonstrate the effectiveness of ICIC techniques in reducing co-channel interference, as well as to compare different techniques. A statistical study was conducted using one of the techniques from the first analysis in order to identify which of its parameters are relevant to the system performance. Additionally, another study is presented to highlight the impact of high user concentration in the proposed scenario. Because of the dynamic aspect of the system, this work proposes a solution based on machine learning. It consists of changing the ICIC parameters automatically to maintain the best possible signal-to-interference-plus-noise ratio (SINR) in a scenario with hotspots appearing over time. All investigations are based on ns-3 simulator prototyping. The results show that the proposed Q-Learning algorithm increases the average SINR from all users and hotspot users when compared with a scenario without Q-Learning. The SINR from hotspot users is increased by 11.2% in the worst case scenario and by 180% in the best case.
Предлагается к реализации спутник Ku-диапазона с многолучевой структурой и повторным использованием частот, обладающий высокой пропускной способностью, в несколько раз превышающей аналогичный параметр традиционных космических аппаратов (КА). Рассматриваются технические аспекты построения полезной нагрузки и особенности использования КА в сетях связи.
We propose for implementation of a Ku-band communication satellite with a multi-beam configuration and frequency reuse technology, having a data throughput, which is several times higher than that of traditional Ku-band satellites. The technical aspects of constructing the payload and specific features of these satellites' application in communication networks are considered.
For the upcoming 4G systems, network multiple-input multiple-output (MIMO) and inter-cell interference coordination (ICIC) are two of key techniques adopted in 4G systems to mitigate the serious inter-cell interference (ICI) and improve coverage and cell-edge throughput. Network MIMO is referred to as coordinated multi-point (CoMP) in LTE-A. In this paper, we propose a simulation platform to analyze the handover issue for downlink CoMP transmissions in LTE-A cellular systems. Among the variety of ICIC strategies, we apply the widely adopted soft frequency reuse (SFR) and the fractional frequency reuse (FFR) schemes. Both schemes are based on the idea of applying a frequency reuse factor of one in cell-center areas, and a higher reuse factor in cell-edge areas. Therefore, the ICI is reduced at the expense of the available frequency resources for each cell.
The concept of cognitive radio can be described as a radio with the study of capabilities, i.e. as a radio that is able to gain knowledge about the radio environment and adjust its operating parameters and protocols accordingly.
The task of minimizing the frequency band is relevant at the stage of the cognitive radio network functioning when distributing the frequency resource between subscriber stations. With the ever-growing demand for frequency bands, this challenge is driven by the need to improve the efficient use of the radio frequency spectrum through frequency reuse methods.
This paper proposes a method for ensuring the reuse of frequencies based on obtaining estimates of mutual distances between subscriber stations in real time. An algorithm is proposed for solving the problem of frequency resource allocation optimization for a cognitive radio network with frequency reuse. The algorithm is based on the method of local optimization, one of the approximate methods of discrete programming. In this case, the condition of local optimality is that the operating frequency assigned to the next subscriber station must be the closest to the frequency assigned in the previous step.
The efficiency of the frequency resource optimization algorithm for the LTE network was analyzed using simulation modeling. The dependences of the bandwidth on the number of subscriber stations served are obtained. The analysis showed that the use of this algorithm allows to reduce the frequency band by 2 -3 times. The analysis also showed that the efficiency of the algorithm increases with the growth of the number of subscriber stations served simultaneously.