Use Of Channel Capacity Research Articles

Delay performance of priority-queue equipped UAV-based mobile relay networks: Exploring the impact of trajectories

UAV-based mobile relay communication systems have an important position in future wireless networks, such as Beyond 5G and 6G, which provide ubiquitous network services. Along this line, UAV-based single-hop relay systems have numerous applications in emergency situations, such as data ferry and assisting post-disaster areas. Although there have been numerous works on optimizing trajectories and other communication resources on such systems, there are few studies on delay performance at the granular packet level. In addition to having homogeneous traffic, such a system can be equipped with diverse traffic with different QoS requirements, owing to the emergence of various applications in today’s communication networks. Based on the traffic requirements, packets with high-priority traffic should be served ahead of those with low-priority ones. To this end, we aim to analytically study the average end-to-end packet delay and buffer overflow performance of such a system at the granular packet level. However, packet-level queuing analysis of heterogeneous traffic is not as straightforward as that of homogeneous traffic. While considering different traffic requirements, we establish a priority queuing model for the source and the UAV nodes based on the stochastic process. Then, on the basis of the established queuing model, the average end-to-end packet delay and buffer overflow probability of the system under different trajectories are studied. Through extensive numerical simulations, we verified the accuracy and effectiveness of the proposed analytical model. The results show that the average packet delay and packet drop probability of high-priority packets under all trajectories are significantly better compared to low-priority packets. UAV trajectory has a great impact on network performance, and an appropriate mobile trajectory that takes full use of channel capacity is superior to a static one.

Implanted Cardiac Pacemaker Mathematical Modeling and Research based on the Volume Conduction

The research of the communication between implanted Cardiac Pacemaker and external devices is a focus. In this paper, a data communications model based Volume Conduction is creatively presented, in this way the human body conductive ability will been utilized to transmit current, which is more effective and decrease for harm of the human body than the other ways, such as: RF, Optical Transcutaneous, etc. As the frequency increases the KHz level, the effect of background biological noise is considered negligible, the channel is thus modeled as AWGN channel in these frequencies. From Shannon information theory, in two-dimensional modulation, the volume conduction channel capacity formula was derived, further derivation: with extremely low SNR using in the two-level modulation can be very effective use of channel capacity, with high SNR a multi-level modulation is used in order to make full use of the channel capacity. Matlab software is used to the channel simulation, the input and output signal waveforms and eye diagram comparison, the curves of the BER and SNR.

Adaptive coding/modulation for shallow-water UWA communications

We consider adaptive modulation and coding techniques for Phase Shift Keying (PSK) transmission schemes over underwater acoustic (UWA) channels. Adaptive modulation and coding can be an effective means of obtaining higher data rates while retaining acceptable error levels by exploiting knowledge of the channel state. This is particularly significant in the UWA scenario, where attained spectral efficiencies are critical since usable bandwidth is a severe limitation. We examine the use of channel capacity and post-equalization signal to noise ratio (SNR) as adaptation metrics. We illustrate the ideas both through simulations and using the results of a recent experiment (AUVfest 2007). In the experiment, in order to evaluate effectiveness of adaptive coding/modulation for UWA communications, we have transmitted a bank of signals with varying spectral efficiencies (obtained by changing the number of transmit elements, modulation scheme, and code rate) back to back. Using the received signals, we illustrate the relevance of the channel condition metrics under consideration, that is, we evaluate the proposed metrics for various scenarios, and provide indications of the transmission rates that could have been achieved reliably.

Stream Channels and Flow Relations

This paper considers the use of channel capacity as a reconnaissance technique for estimating mean flow and the magnitude of floods at various expected frequencies. Channel capacity is shown to be a valuable tool in estimating mean flow and flood values. Low flows are examined briefly and are shown to have diminishing relationships to channel capacity with increasing severity of low flow. Derived equations to estimate flood magnitudes provided good results when tested within the same environment. The coefficients of the derived equations are shown to lack transferability to different physical environments.