N-channel stop-and-wait (SW) hybrid automatic repeat request (HARQ) protocol is widely used in wireless communication systems due to its simplicity and high efficiency. However, different HARQ processes are transmitted over sub-channels with individual encoding. We present a joint coding HARQ scheme in which erroneous codewords of N parallel channels are jointly encoded for retransmissions. Erroneous and retransmitted codewords form a linear concatenated block code which is jointly decoded with a low complexity iterative decoding algorithm. Simulation results show that the normalized throughput performance obtains a significant gain while complexity increasing is limited.
An embedded and equal-length two-section open-stub is employed to improve the roll-off rate of both low-pass and band-pass filters. The characteristic of the proposed two-section stub is which can extend pass-band, and it will not introduce the additional harmonic stop-band in the pass-band. Measured results are presented to illustrate the validity of the design method.
Large aperture and wideband phased array antennas use both phase shifters for each element and true time delay for each subarray to avoid squint. Thus both phase shifter calibration and true time delay calibration are required. In this paper, we focus on true time delay calibration, and propose a method that conducts measurements through space to estimate the delay difference between two subarrays. Our method is essential in systems for which wired measurements are impossible. Additionally, phase measurement is not required in our method because the delay difference is estimated from just the level variation. Experiments and their results are detailed. Delay difference could be estimated with error of 0.37λ or better.