Robust transmission design for multicell D2D underlaid cellular networks

This paper investigates the robust transmission design (RTD) of a multicell device-to-device (D2D) underlaid cellular network with imperfect channel state information (CSI). The bounded model is adopted to characterize the CSI impairment and the aim is to maximize the worst-case sum rate of the system. To protect cellular communications, it is assumed that the interference from all D2D transmitters to each base station (BS) is power-limited. It is first shown that the worst-case signal-to-interference-plus-noise ratio (SINR) of each D2D link can be obtained directly, while that of cellular links cannot be similarly found since the channel estimation error vectors of cellular links are coupled in the SINR expressions. To solve the nonconvex problem, the objective function of the original problem is replaced with its lower bound, and the resulted problem is decomposed into multiple semidefinite programming (SDP) subproblems, which are convex and have computationally efficient solutions. An iterative RTD algorithm is then proposed to obtain a suboptimal solution. Simulation results show that D2D communication can significantly increase the performance of the conventional cellular systems while causing tolerable interference to cellular users. In addition, the proposed RTD algorithm outperforms the conventional nonrobust transmission design greatly in terms of network spectral efficiency

Deployment of wireless regional area network and its impact on DTV service coverage

Prediction of digital TV (DTV) coverage has not considered the potential interference originating in the IEEE 802.22 Wireless Regional Area Network (WRAN), which operates in the same TV bands. WRAN interference could affect DTV reception, resulting in DTV service outage in some areas. Spectrum sensing is a means of minimizing the interference by not operating WRAN in the TV band where DTV signal is detected to be present. However, limited sensing accuracy could lead to erroneous decision. This paper investigates the extent of which DTV service quality is affected by the operation of WRAN with limited sensing accuracy. One of the main factors that limit sensing accuracy is the variability in radio propagation channel. Depending on the characteristics of the statistical variation, radio channels are modeled as Gaussian, Rayleigh, Nakagami, and Rician channels in this paper. The probability of DTV service outage is analyzed and expressed as a function of sensing accuracy. The theoretical results presented here have been validated by the Monte Carlo simulations