Capacity Analysis of Interference Alignment With Bounded CSI Uncertainty

Interference alignment (IA) has been demonstrated to achieve the degree-of-freedom (DoF) of an interference channel given perfect global channel state information (CSI). In this letter, we consider the case of imperfect CSI with bounded errors and derive a capacity lower bound of the channel using IA. We show that this lower bound is within 1 bps/Hz of the capacity of the perfect CSI case up to a certain signal-to-noise ratio (SNR) which we refer to it as the saturating SNR. Further, we introduce a new metric called modified DoF (mDoF) in order to characterize the multiplexing performance of IA with imperfect CSI at finite SNR. Simulation results for the 3-user case are provided to illustrate the region within which the actual capacity of IA falls

Capacity Distribution for Interference Alignment With CSI Errors and Its Applications

Interference alignment (IA) is known to achieve the degree-of-freedom (DoF) capacity of the interference channel, if full channel state information (CSI) is available at the transmitters perfectly. Challenges, however, arise when CSI is not perfect, and the achievable capacity of IA is not well understood. In this paper, we study the achievable performance of the interference channel using perfect IA techniques based on imperfect CSI. In particular, we obtain the statistical distribution of the maximum achievable rate per stream of the channel. Utilizing our analytical results, we derive new nonasymptotic performance metrics that are then used to 1) optimize the number of streams per user for maximizing the network sum-rate and 2) assess the performance of IA in the time-varying block fading channel. Numerical results are provided to reveal the accuracy of our analytical results

Quantum secrecy in thermal states II

In this paper we consider a scheme for cryptographic key distribution based on a variation of continuous variable quantum key distribution called central broadcast. In the continuous variable central broadcast scheme, security arises from discord present in the Hanbury Brown and Twiss effect from a thermal source. The benefit of this scheme is that it expands the range of frequencies into the microwave regime. Longer wavelengths—where the thermal photon number is higher and correlations remain robust over long distances—may even be preferable to optical wavelengths. Assuming that Alice controls the source but not the distribution of the light (e.g. satellite broadcasts), then we demonstrate that the central broadcast scheme is robust to an entangling cloner attack. We establish the security of the protocol both experimentally and theoretically

Quantum Secrecy in Thermal States II

In this paper we consider a scheme for cryptographic key distribution based on a variation of continuous variable quantum key distribution called central broadcast. In the continuous variable central broadcast scheme, security arises from discord present in the Hanbury Brown and Twiss effect from a thermal source. The bene t of this scheme is that it expands the range of frequencies into the microwave regime. Longer wavelengths—where the thermal photon number is higher and correlations remain robust over long distances—may even be preferable to optical wavelengths. Assuming that Alice controls the source but not the distribution of the light (e.g. satellite broadcasts), then we demonstrate that the central broadcast scheme is robust to an entangling cloner attack. We establish the security of the protocol both experimentally and theoretically