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Number of results: 6
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Abstract

The 802.11ax standard final specification is expected in 2019, however first parameters are just released. The target of the new standard is four times improvement of the average throughput within the given area. This standard is dedicated for usage in dense environment such as stadiums, means of municipal communication, conference halls and others. The main target is to support many users at the same time with the single access point. The question arises if the new standard will have higher throughput then previous ones in the single user mode. The author calculated the maximal theoretical throughput of the 802.11ax standard and compared the results with the throughput of older 802.11 standards such as 802.11n and 802.11ac. The new he-wifi-network example included in the ns-3.27 release of the NS-3 simulator was used to simulate the throughput between the access point and the user terminal. The results indicate that in some conditions the 802.11ac standard has higher throughput than the new 802.11ax standard.
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Abstract

The main idea of all Active Queue Management algorithms, is to notify the TCP sender about incoming congestion by dropping packets, to prevent from the buffer overflow, and its negative consequences. However, most AQM algorithms proposed so far, neglect the impact of the high speed and long delay links. As a result, the algorithms’ efficiency, in terms of throughput and/or queue stability, is usually significantly decreased. The contribution of this paper is twofold. First of all, the performance of the well known AQM algorithms in high speed and long delay scenarios is evaluated and compared. Secondly, a new AQM algorithm is proposed, to improve the throughput in the large delay scenarios and to exclude the usage of random number generator.
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Abstract

Cloud radio access network (C-RAN) has been proposed as a solution to reducing the huge cost of network upgrade while providing the spectral and energy efficiency needed for the new generation cellular networks. In order to reduce the interference that occur in C-RAN and maximize throughput, this paper proposes a sequentially distributed coalition formation (SDCF) game in which players, in this case the remote radio heads (RRHs), can sequentially join multiple coalitions to maximize their throughput. Contrary to overlapping coalition formation (OCF) game where players contribute fractions of their limited resources to different coalitions, the SDCF game offers better stability by allowing sequential coalition formation depending on the availability of resources and therefore providing a balance between efficient spectrum use and interference management. An algorithm for the proposed model is developed based on the merge-only method. The performance of the proposed algorithm in terms of stability, complexity and convergence to final coalition structure is also investigated. Simulation results show that the proposed SDCF game did not only maximize the throughput in the C-RAN, but it also shows better performances and larger capabilities to manage interference with increasing number of RRHs compared to existing methods.
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Abstract

A significant part of hard coal production (15–19% in the years 2010–2017, i.e. 1.0–1.3 billion tons per year) is traded on the international market. The majority of coal trade takes place by sea, accounting for 91–94% of the total coal trade. The article discusses the share of coal in international seaborne trade and the largest coal ports. Coal is one the five major bulk commodities (in addition to iron ore, grain, bauxite, alumina, and phosphate rock). In the years 2010–2016, the share of coal in international seaborne trade and major bulk commodities was 36–41% and 11–12%, respectively. Based on the analysis of coal throughput in different ports worldwide, the ports with the largest throughput include the ports of Qinhuangdao (China), Newcastle (Australia), and Richards Bay (South Africa). For 2013–2017, their throughput amounted to a total of 411–476 million tons of coal. The largest coal exporting countries were: Australia, Indonesia, Russia, Colombia, South Africa, and the US (a total of 85% share in global coal exports), while the largest importers are Asian countries: China, India, Japan, South Korea and Taiwan (a 64% share in global imports). In Europe, Germany is the largest importer of coal (54 million tons imported in 2016). The article also discusses the freight costs and the bulk carrier fleet. Taking the price of coal at the recipient’s (i.e. at the importer’s port) into account, the share of freight costs in the CIF price of steam coal (the price of a good delivered at the frontier of the importing country) was at the level of 10–14%. In the years 2010–2016, the share of bulk carriers in the world fleet was in the range of 11–15%. In terms of tonnage, bulk carriers accounted for 31–35% of the total tonnage of all types of ships in the world. The share of new (1–4 years) bulk carriers in the total number of ships on a global scale in the years 2010–2016 was 29–46%.
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Abstract

A novel non-orthogonal multiple access (NOMA) scheme is proposed to improve the throughput and the outage probability of the cognitive radio (CR) inspired system which has been implemented to adapt multiple services in the nextgeneration network (5G). In the proposed scheme, the primary source (PS) had sent a superposition code symbol with a predefined power allocation to relays, it decoded and forwarded (DF) a new superposition coded symbol to the destination with the other power allocation. By using a dual antenna at relays, it will be improved the bandwidth efficiency in such CR NOMA scheme. The performance of the system is evaluated based on the outage probability and the throughput with the assumption of the Rayleigh fading channels. According to the results obtained, it is shown that the outage probability and throughput of the proposed full-duplex (FD) in CR-NOMA with reasonable parameters can be able deploy in practical design as illustration in numerical results section.
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Abstract

The dual core bit-byte CPU must be equipped with properly designed circuits, providing interface between the two processor units, and making it possible to exploit all its advantages like versatility of the byte unit and speed of the bit unit. First of all, the interface circuits should be designed in such a way, that they don’t disturb maximally parallel operation of the units, and that the CPU as a whole works in the same manner as in a standard PLC. The paper presents hardware solutions supporting effective operation of PLC CPU-s. Possibilities of solving problems concerning data exchange between a CPU and peripheral circuits were presented, with a special stress on timers and counters, and also on data exchange between the bit unit and the byte unit. The objective of the proposed solutions is to decrease the time necessary for a CPU to access its peripheries.
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