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1

OFDM for Cognitive Radio Systems : Novel Power Allocation and Bit Loading Algorithms

Razmi Shirin, Parhizgar Naser

International Journal of Electronics and Telecommunications

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2019

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Vol. 65, No. 1

139--145

EN

A novel method to improve the performance of the frequency band is cognitive radio that was introduced in 1999. Due to a lot of advantages of the OFDM, adaptive OFDM method, this technique is used in cognitive radio (CR) systems, widely. In adaptive OFDM, transmission rate and power of subcarriers are allocated based on the channel variations to improve the system performance. This paper investigates adaptive resource allocation in the CR systems that are used OFDM technique to transmit data. The aim of this paper is to maximize the achievable transmission rate for the CR system by considering the interference constraint. Although secondary users can be aware form channel information between each other, but in some wireless standards, it is impossible for secondary user to be aware from channel information between itself and a primary user. Therefore, due to practical limitation, statistical interference channel is considered in this paper. This paper introduces a novel suboptimal power allocation algorithm. Also, this paper introduces a novel bit loading algorithm. In the numerical results sections, the performance of our algorithm is compared by optimal and conventional algorithms. Numerical results indicate our algorithm has better performance than conventional algorithms while its complexity is less than optimal algorithm.

2

Resource allocation in LTE-unlicensed femtocell networks

Martyna J.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2018

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nr 8-9

839--843, CD

EN

In this paper, resource allocation technique for LTE femtocell network in licensed and unlicensed bands is proposed. Additionally, allocation of wireless resources to each mobile user in the Wi-Fi band occurs in parallel with the bandwidth allocation between competing users in LTE. To improve the performance of femtocells, a heuristic algorithm based on Kalai-Smorodinsky solution of bargaining problem is presented. The numerical simulation conf rms the correctness of the adopted mode.

PL

W artykule zaproponowano technike przydzielania zasobów dla sieci femtokomórkowej w licencjonowanych i nielicencjonowanych pasmach. Ponadto przydzielanie zasobów bezprzewodowych każdemu użzytkownikowi mobilnemu w paśmie Wi-Fi odbywa się równolegle z alokacją szerokości pasma pomiędzy konkurującymi użytkownikami w LTE. W artykule przedstawiono heurystyczny algorytm oparty na schemacie arbitrażowym Kalai-Smorodinsky'ego dla przetargu. Symulacja numeryczna potwierdza poprawność przyjętej metody alokacji zasobów.

3

Energy Efficiency Optimization by Spectral Efficiency Maximization in 5G Networks

Krasniqi B., Rexha B., Maloku B.

International Journal of Electronics and Telecommunications

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2018

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Vol. 64, No. 4

497--503

EN

Energy and spectral efficiency are the main challenges in 5th generation of mobile cellular networks. In this paper, we propose an optimization algorithm to optimize the energy efficiency by maximizing the spectral efficiency. Our simulation results show a significant increase in terms of spectral efficiency as well as energy efficiency whenever the mobile user is connected to a low power indoor base station. By applying the proposed algorithm, we show the network performance improvements up to 9 bit/s/Hz in spectral efficiency and 20 Gbit/Joule increase in energy efficiency for the mobile user served by the indoor base station rather than by the outdoor base station.

4

Optimal power allocation for cognitive LTE-femtocell networks based on game theory

Martyna J.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2017

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nr 8-9

1067--1071, CD

EN

In this paper, a new power control scheme for cognitive LTE-femtocell networks based on game theory is proposed. The problem is formulated as a coalition graph game problem to maximise throughput and system fairness. Then, a heuristic low-complexity algorithm to solving so presented problem is given. Simulation results have validated that the proposed scheme is effective in managing the cognitive femtocell network.

PL

W tym artykule proponuje się nowy schemat kontroli mocy dla sieci kognitywnych femtokomórek LTE oparty o teorię gier. Problem jest sformułowany jako gra koalicyjna, maksymalizująca przepustowość i sprawiedliwość systemu. Następnie, przedstawiono heurystyczny algorytm o małej złożoności dla rozwiązanie tego problemu. Wyniki symulacji potwierdziły, że proponowany schemat jest efektywny dla zarządzanie femtokomórką kognitywną LTE.

5

Power Allocation for Energy-Harvesting-based Fading Cognitive Multiple Access Channels : with or without Successive Interference Cancellation

Li Q., Xu D.

International Journal of Electronics and Telecommunications

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2017

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Vol. 63, No. 1

65--72

EN

This paper considers a fading cognitive multiple access channel (CMAC), where multiple secondary users (SUs), who share the spectrum with a primary user (PU), transmit to a cognitive base station (CBS). A power station is assumed to harvest energy from the nature and then provide power to the SUs. We investigate the power allocation problems for such a CMAC to maximize the SU sum rate under the interference power constraint, the sum transmit power constraint and the peak transmit power constraint of each individual SU. In particular, two scenarios are considered: with successive interference cancellation (SIC) and without SIC. For the first scenario, the optimal power allocation algorithm is derived. For the second scenario, a heuristic algorithm is proposed. We show that the proposed algorithm with SIC outperforms the algorithm without SIC in terms of the SU sum rate, while the algorithm without SIC outperforms the algorithm with SIC in terms of the number of admitted SUs for a high sum transmit power limit and a low peak transmit power limit of each individual SU.

6

Improved Water-Filling Power Allocation for Energy-Efficient Massive MIMO Downlink Transmissions

Noor Shahida M. K., Nordin R., Insmail M.

International Journal of Electronics and Telecommunications

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2017

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Vol. 63, No. 1

79--84

EN

Energy Efficiency (EE) is becoming increasingly important for wireless communications and has caught more attention due to steadily rising energy costs and environmental concerns. Recently, a new network architecture known as Massive Multiple-Input Multiple-Output (MIMO) has been proposed with the remarkable potential to achieve huge gains in EE with simple linear processing. In this paper, a power allocation algorithm is proposed for EE to achieve the optimal EE in Massive MIMO. Based on the simplified expression, we develop a new algorithm to compute the optimal power allocation algorithm and it has been compared with the existing scheme from the previous literature. An improved water filling algorithm is proposed and embedded in the power allocation algorithm to maximize EE and Spectral Efficiency (SE). The numerical analysis of the simulation results indicates an improvement of 40% in EE and 50% in SE at the downlink transmission, compared to the other existing schemes. Furthermore, the results revealed that SE does not influence the EE enhancement after using the proposed algorithm as the number of Massive MIMO antenna at the Base Station (BS) increases.

7

Modulation-Mode Assignment for SVD-assisted Downlink Multiuser MIMO Transmission Schemes with Iterative Detection

Ahrens A., Benavente-Peces C.

International Journal of Electronics and Telecommunications

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2011

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Vol. 57, No. 1

127-134

EN

Since the capacity of multiple-input multiple-output (MIMO) systems increases linearly with the minimum number of antennas at both, the transmitter as well as the receiver side, MIMO systems have attracted a lot of attention for both frequency and non-frequency selective channels and reached a state of maturity. By contrast, MIMO-aided multiple-user systems require substantial further research. In comparison to zero-forcing (ZF) multiuser transmission techniques, where all users are treated jointly, the investigated singular value decomposition (SVD) assisted DL multiuser MIMO solution takes the individual user's channel characteristics into account. In analogy to bit-interleaved coded irregular modulation, we introduce a MIMO-BICM scheme, where different user-specific signal constellations and mapping arrangement were used within a single codeword. Extrinsic information transfer (EXIT) charts are used for analyzing and optimizing the convergence behaviour of the iterative demapping and decoding. Our results show that in order to achieve the best bit-error rate, not necessarily all user-specific MIMO layers have to be activated.

8

Effect of unequal power allocation in turbo coded multi-route multi-hop networks

Wada T., Jamalipour A., Ohuchi K., Okada H., Saito M.

Journal of Telecommunications and Information Technology

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2006

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nr 1

46-53

EN

Multi-hop ad hoc networks are promising candidates for next generation mobile communications. They have sufficient channel capacity to achieve high data rate transmission for large number of users. One advantage of multi-hop networks is to realize multi-route transmissions. Since information bit streams can be transmitted over multiple routes, we can obtain route diversity effect. In order to enhance the route diversity effect, we usually introduce forward error correction schemes. Turbo coding is one of suitable coding methods for multi-hop networks. The turbo encoder generates one message stream and two parity streams whilst the message stream is more important than the parity streams for achieving reliable communications. Thus an unequal power allocation to the message and parity streams could be effective in improving the performance. In this paper, the effect of unequal power allocation for turbo coded multi-hop networks is investigated. Assuming the channel as additive white Gaussian and binary symmetric, we will show considerable performance improvement by unequal power allocation in terms of the bit error rate performance in multi-route multi-hop networks.