For seamless communication in millimeter-wave (mm-wave) transmission systems, the robustness against link blockage and user mobility should be guaranteed. Cooperative joint network design over conventional microwave bands and mm-wave bands is essential in future mm-wave WLANs (e.g., IEEE 802.11ay) and 5G cellular networks, and hence understanding the discrepancy between the propagation properties at those frequency bands is crucial. In this letter, the angle-of-arrival characteristics at mm-wave band (60 GHz) and microwave band (2.4 GHz) in indoor environments are presented. From the measurement results, it was seen that the line-of-sight and first-order reflected paths agree well each other, but diffraction and scattering are observed only at microwave band. It was also shown that the angular spreads at mm-wave band was about 25 degrees smaller than those at microwave band.
This paper considers a multi-machine control system using power line communication (PLC). The signal-to-noise ratio (SNR) of PLC channels has cyclostationary features synchronous to the mains voltage. As a promising candidate of the multiple access scheme for the system, this paper proposes a synchronous code division multiple access (SCDMA) scheme that uses mains voltage as its system clock. By using orthogonal codes, the communication performance of each code-channel is equalized, and the worst-case performance is improved.
This letter proposes a neural network based channel identification and compensation methods for an OFDM system. Under the fast fading environment, pilot-aided channel estimation suffers from channel state fluctuation particularly in the last part of the packet. The proposed approach can estimate the whole transition of channel states and efficiently compensate the channel variation using the generalization capability of a neural network. The computer simulation results clarify its effectiveness via improved BER performance even under the stringent Doppler shift.
In a full-digital massive multi-user MIMO system, maximal-ratio combining (MRC) can obtain more considerable diversity gain while inter-stream interference (ISI) and multi-user interference (MUI) can be canceled using minimum mean square error (MMSE) algorithm. This letter evaluates the throughputs of detection schemes for different antenna numbers in the massive MIMO system with low-resolution analog-to-digital converters (ADCs). The letter makes a comparison between MRC and MMSE under quantization range limit. Numerical results show that MRC achieves better system performance with lower implementation complexity as the number of antennas increases.