7,184 research outputs found
Uplink and Downlink Performance Bounds for Full Duplex Cellular Networks
With Full Duplex (FD), wireless terminal is capable of transmitting and
receiving data simultaneously in the same frequency resources, however, it
introduces self interference and co-channel interference. Even though various
signal processing techniques are emerged to cancel the self interference, the
bottleneck for FD performance in cellular systems is the co-channel
interference from the other uplink and downlink signals. In this work we have
studied both the uplink and downlink performances of a FD cellular network,
where users employ fractional power control in uplink. We use Matern Cluster
Process to model the network, which provides a tractable and realistic model to
characterize the user-base station distances which are needed for uplink power
control. Based on the obtained coverage probabilities, rates and their robust
approximations, we show that while FD improves downlink performance, it
severely hurts the uplink performance. Also, we provide a trade-off between
uplink and downlink performances. Our study suggests dense deployment of low
power base stations can improve the performance of FD system
Beamforming Techniques for Non-Orthogonal Multiple Access in 5G Cellular Networks
In this paper, we develop various beamforming techniques for downlink
transmission for multiple-input single-output (MISO) non-orthogonal multiple
access (NOMA) systems. First, a beamforming approach with perfect channel state
information (CSI) is investigated to provide the required quality of service
(QoS) for all users. Taylor series approximation and semidefinite relaxation
(SDR) techniques are employed to reformulate the original non-convex power
minimization problem to a tractable one. Further, a fairness-based beamforming
approach is proposed through a max-min formulation to maintain fairness between
users. Next, we consider a robust scheme by incorporating channel
uncertainties, where the transmit power is minimized while satisfying the
outage probability requirement at each user. Through exploiting the SDR
approach, the original non-convex problem is reformulated in a linear matrix
inequality (LMI) form to obtain the optimal solution. Numerical results
demonstrate that the robust scheme can achieve better performance compared to
the non-robust scheme in terms of the rate satisfaction ratio. Further,
simulation results confirm that NOMA consumes a little over half transmit power
needed by OMA for the same data rate requirements. Hence, NOMA has the
potential to significantly improve the system performance in terms of transmit
power consumption in future 5G networks and beyond.Comment: accepted to publish in IEEE Transactions on Vehicular Technolog
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