A two-dimensional(2D)optical true-time delay(TTD)beam-forming system using a compact fiber grating prism(FGP)for a planar phased array antenna(PAA)is proposed.The optical beam-forming system mainly consists of a TTD unit based on the same compact FGP,one tunable laser for elevation beam steering,and a controlled wavelength converter for azimuth beam steering.A planar PAA using such2D optical TTD unit has advantages such as compactness,low bandwidth requirement for tunable laser sources,and potential for large-scale system implementations.The proof-of-concept experiment results demonstrate the feasibility of the proposed scheme.
We demonstrate the theory of chromatic dispersion(CD)-induced constellation rotation(CR) in a radio-over-fiber(ROF) link and a method for compensation. We also propose a 60 GHz full-duplex ROF system with vector signal transmission including no CD effect. The evaluation of 5 Gb/s 16 quadrature amplitude modulation signal transmission shows that the CD-induced CR can be entirely overcome due to the proposed method which is simply implemented through an optical phase shifter. The proposed ROF schedule is not only applicable for V-band(57–64 GHz) but also fits for W-band(75–110 GHz), or any other bandwidth.
This paper first introduces the performance analysis of two classical channel quality indicator (CQI) feedback schemes which are best-n feedback and the threshold based feedback and derives the mathematical expressions of average capacity which is described by Theorem 1 and 2.Then, a reduced feedback scheme is designed for multiple traffics and multi-channel.The novel scheme combines the best-n feedback and the threshold based feedback together to reduce the feedback overhead.The proposed scheme can not only guarantee the quality of service (QoS) requirement of real time (RT) traffic but also reduce feedback overhead at the cost of a marginal increased downlink overhead.Simulation results demonstrated the good performance of the proposed feedback scheme.
SUN Qiao-yunCHAI Wen-yanYANG Xiu-yunSUN KaiWU Cui-ting
