The Experts below are selected from a list of 326787 Experts worldwide ranked by ideXlab platform
Vivek Ashok Bohara - One of the best experts on this subject based on the ideXlab platform.
-
Rate and outage trade offs for ofdma based device to device communication frameworks
IEEE Access, 2017Co-Authors: Naveen Gupta, Vivek Ashok BoharaAbstract:This paper presents the Rate and outage tradeoffs for orthogonal frequency division multiple access-based device-to-device (D2D) communication frameworks, wherein multiple D2D users coexist with the cellular users in the same cell. Analytical expressions for outage probability for three D2D frameworks, namely underlay, overlay, and cooperative D2D (C-D2D) have been derived. Specifically, for underlay framework, a minimum value of angle $\theta $ (an angle between a cellular link and D2D interference link) is derived, for which the Target Rate and outage probability constraint of both cellular and D2D users are satisfied. For overlay and C-D2D frameworks, an optimal subcarrier sharing scheme is proposed, which not only helps the cellular users to achieve the Target quality-of-service but also helps the D2D users to communicate with each other. In addition to above, benefits involved in employing one framework over other have also been investigated. Our results show that for a higher outage probability constraint of the cellular user, the C-D2D framework outperforms the underlay and overlay frameworks.
-
an adaptive subcarrier sharing scheme for ofdm based cooperative cognitive radios
IEEE Transactions on Cognitive Communications and Networking, 2016Co-Authors: Naveen Gupta, Vivek Ashok BoharaAbstract:Incorporation of orthogonal frequency division multiplexing (OFDM) in cooperative cognitive radio network facilitates subcarrier sharing to achieve spatial diversity with opportunistic spectrum access. In addition, adaptive modulation has been adopted widely in wireless communication to improve spectral efficiency. Use of adaptive modulation for cooperative cognitive relaying transmission to maximize throughput under bit error Rate (BER) constraint is an open issue. In this paper, we propose an adaptive subcarrier sharing scheme for OFDM-based cooperative cognitive radio system, wherein cognitive (secondary) system helps the primary system to achieve its Target Rate of communication in exchange for opportunistic spectrum sharing. Secondary transmitter uses adaptive mode of transmission to relay the primary signal with higher throughput while maintaining the BER constraint of primary system. At primary receiver, a BER-based selection combining scheme is employed to combine the signals received in two phases. Closed-form analytical expressions for BER and outage probability of primary and secondary system for a Rayleigh flat fading channel have been derived. Results show that the outage probability with the proposed scheme (for dissimilar modulation) outperforms direct transmission and conventional maximal ratio combining scheme (for similar modulation).
-
a cognitive subcarriers sharing scheme for ofdm based decode and forward relaying system
International Conference on Cognitive Radio Oriented Wireless Networks, 2015Co-Authors: Naveen Gupta, Vivek Ashok BoharaAbstract:This paper analyzes the performance of a proposed subcarriers sharing scheme. According to the scheme, secondary system helps the primary system via two phase Decode and Forward orthogonal frequency division multiplexing based relaying. If primary (licensed user) is unable to achieve its Target Rate then secondary transmitter (which is located within a critical distance from primary transmitter) will provide few subcarriers to primary receiver, to fulfill the requirement of the primary system and remaining subcarriers can be used by secondary (cognitive) system for its own data transmission. If secondary transmitter is located at or beyond the critical distance from primary transmitter then no spectrum sharing is possible. The analytic expression of outage probability of the primary and secondary system has been computed. Through theoretical and simulation results it has been shown that the primary outage probability with cooperation (while secondary transmitter acts a partial relay) is less than the outage probability for direct transmission. Therefore opportunistic spectrum sharing can be achieved by secondary system.
Subhabrata Roy - One of the best experts on this subject based on the ideXlab platform.
-
on residual energy maximization in energy harvesting cognitive radio network
Wireless Communications and Networking Conference, 2017Co-Authors: Avik Banerjee, Santi P. Maity, Subhabrata RoyAbstract:Recent advancement in wireless communications demands high data Rate transmission at low power consumption. To this aim, the present work proposes an energy harvesting based cognitive radio (CR) system operating in time slotted mode. Energy harvesting and spectrum sensing (SS) are done simultaneously by the CR user through power splitting mode. On the other hand, during the transmission time slot, the CR user either harvests energy or transmits its own data based on SS decision result. An optimization problem is developed to maximize the residual energy under the constraints of sensing reliability of the PU and spectrum efficiency (SE) Target Rate of the CR. The concavity of the objective function is shown which ensures a global solution to the problem. Closed form expressions for the sensing time and CR transmit power are found and the results are validated by simulations.
Peng Tan - One of the best experts on this subject based on the ideXlab platform.
-
optimal cooperative stRategy in energy harvesting cognitive radio networks
Vehicular Technology Conference, 2017Co-Authors: Hai Jiang, Rongfei Fan, Peng TanAbstract:We consider a cognitive radio system, in which a secondary transmitter harvests energy from a primary transmitter's wireless signals. If the achievable Rate of the primary transmitter's direct link to the primary receiver is smaller than a Target Rate, the secondary transmitter can provide decode-and-forward relaying service for the primary system and transmit its own data as well, in which the secondary transmitter uses a time-switching protocol to harvest energy and decode primary transmitter's information. Our Target is to achieve maximal secondary throughput by selecting the time portion used for energy harvesting and the percentage of the secondary transmitter's power used for relaying. The formulated problem is nonconvex. To solve the problem, we show that, after some math manipulations, the initial problem can be converted to a problem with the objective function being theoretically proved to be quasiconcave. Then we propose a two-level bisection search algorithm to find the maximal objective function. The efficiency of our proposed method is demonstRated by computer simulation.
Nai Tong Zhang - One of the best experts on this subject based on the ideXlab platform.
-
cooperative ofdm relaying for opportunistic spectrum sharing protocol design and resource allocation
IEEE Transactions on Wireless Communications, 2012Co-Authors: Wei Dang Lu, Yi Gong, See Ho Ting, Xuan Li Wu, Nai Tong ZhangAbstract:In this paper, we propose an opportunistic spectrum sharing protocol that exploits the situation when the primary system is incapable of supporting its Target transmission Rate. Specifically, the secondary system tries to help the primary system to achieve its Target Rate via two-phase cooperative OFDM relaying, where the secondary system acts as an amplify-and-forward relay for the primary system by allocating a fraction of its subcarriers to forward the primary signal. At the same time, the secondary system uses the remaining subcarriers to transmit its own signal, and thus gaining opportunistic spectrum access. As a part of the protocol, if the primary system finds that outage will occur even when the secondary system serves as a pure relay, the primary system will cease transmission and the secondary system will be granted access to the primary spectrum. We study the joint optimization of the set of subcarriers used for cooperation, subcarrier pairing, and subcarrier power allocation such that the transmission Rate of the secondary system is maximized, while helping the primary system, as a higher priority, to achieve its Target Rate. Simulation results demonstRate the performance of the proposed spectrum sharing protocol as well as the win-win solution for the primary and secondary systems.
Robert W Heath - One of the best experts on this subject based on the ideXlab platform.
-
low complexity antenna selection for low Target Rate users in dense cloud radio access networks
IEEE Transactions on Wireless Communications, 2016Co-Authors: Jeonghun Park, Robert W HeathAbstract:We propose a low complexity antenna selection algorithm for low Target Rate users in cloud radio access networks. The algorithm consists of two phases. In the first phase, each remote radio head (RRH) determines whether to be included in a candidate set by using a predefined selection threshold. In the second phase, RRHs are randomly selected within the candidate set made in the first phase. To analyze the performance of the proposed algorithm, we model RRHs’ and users’ locations by a homogeneous Poisson point process, whereby the signal-to-interference ratio (SIR) complementary cumulative distribution function is derived. By approximating the derived expression, an approximate optimum selection threshold that maximizes the SIR coverage probability is obtained. Using the obtained threshold, we characterize the performance of the algorithm in an asymptotic regime, where the RRH density goes to infinity. The obtained threshold is then modified depending on various algorithm options. A distinguishable feature of the proposed algorithm is that the algorithm complexity keeps constant independent to the RRH density, so that a user is able to connect to a network without heavy computation at baseband units.
-
can operators simply share millimeter wave spectrum licenses
Information Theory and Applications, 2016Co-Authors: Abhishek K Gupta, Jeffrey G Andrews, Robert W HeathAbstract:Because of their often noise-limited behavior, millimeter wave systems may be able to share spectrum licenses without any coordination. We establish the theoretical feasibility of uncoordinated sharing by considering a downlink system containing multiple mmWave cellular providers. We compute the downlink Rate distribution, and compare that against systems with exclusive licenses. We show that shared licenses can use a smaller bandwidth to achieve the same per-user median Rate as providers with an exclusive spectrum license. We also show that both total interference and available bandwidth increase with the size of the spectrum sharing coalition, which implies that the optimal amount of spectrum sharing depends on the Target Rate.
