In space communications, the signal suffers a long-distance transmission and a high dynamic movement. The long-distance transmission causes a very low signal-to-noise ratio (SNR) and the high dynamic movement causes a high-accelerating Doppler-shift. To address the low SNR, the conventional strategy is long-time accumulation. However, during the long-time accumulation period, the high-accelerating Doppler-shift brings about the serious energy dispersion problem. In this paper, we propose one joint-comb-acquisition (JCA) scheme to address the energy dispersion problem. The proposed JCA scheme, which uses multiple accumulation periods to jointly construct a narrower comb-search-range, excludes most noise elements. Also, the theoretical analysis derives the closed-form expression for acquisition probability. Moreover, the simulation results demonstrate the significant increase of acquisition probability varies from 4.6 to 47.2 percents, as compared with the existing schemes.

As current develop trends in network architecture and key technologies are enabling the vision of the heterogeneous sharing network, the necessity intensifies for addressing real-life aspects in massive scales. Effectively control the network topology remains a key design requirement for heterogeneous resource sharing network. In this work, we exploit previous theoretical results on the network topology control and the decentralized nature of the blockchain, proposing a network topology control algorithm based on a positive evaluation method for resource sharing network, and was demonstrated for controlling a dynamic network topology. Furthermore, we established the positive evaluation method to evaluate the node's reliability by virtual credit values and behavior of the nodes. The simulation results and performance analysis showed that the proposed algorithm can effectively delay the expansion speed of network topology, thereby increase the feasibility and effectiveness of topology control.

Abstract A system called WiSDP, which is based on Wi‐Fi signals, to detect whether a Seated Dumbbell Press action is standard by using inexpensive consumer Wi‐Fi devices is proposed. Compared with the scheme based on high speed cameras and wearable sensors, Wi‐Fi devices are insensitive to light and colour, do not need wear any device, and decrease the risk of disclosing privacy. WiSDP senses environment changes through the Channel State Information which is fine‐grained physical layer information comparing to frequently used Received Signal Strength Indicator. Compared to the action recognition, action quality recognition depends on slight differences between a non‐standard action and standard actions, which makes it challenging. The authors propose an improved sliding window algorithm calculating action energy to extract Seated Dumbbell Press actions from the Channel State Information streams, estimate action quality by choosing an appropriate classifier and use Principal Component Analysis and Butterworth low‐pass filter to remove noise. The authors conduct experiments in two different scenarios and the average true positive rate of WiSDP are 94.66% and 95.11%, respectively.

In this paper, we propose an AHP‐WKNN method for indoor localization which combines the Analytic Hierarchy Process (AHP) technique and the Weighted K‐nearest Neighbor (WKNN) algorithm. AHP serves to assign weights when WKNN is employed to select fingerprints for indoor positioning. The AHP technique can reasonably enlarge the influence that the received signal strength (RSS) gap between reference points has on the weights, achieving better performance in positioning. This paper also modifies the adaptive Kalman filter (AKF) noise reduction method by correcting the output based on the error between the RSS measurement and the expected output. The modified AKF can track the changes of RSS more effectively and achieve better performance of noise reduction. The simulation result shows that the proposed AHP‐WKNN method and the modified AKF can improve positioning accuracy effectively.

The energy-saving problem in mobile cloud computing (MCC) environment has always been the research hotspot in the field of wireless communications. In this paper, we investigate the energy-optimal transmission rate scheduling scheme for mobile cloud computing. Instead of adopting the widely-used dynamic programming (DP) algorithm which is in need of the statistical information of the stochastic wireless channels, we propose a modified Lyapunov optimization method. The method is obtained by modifying the Lyapunov optimization method to adapt it for MCC scenario. The method can obtain a closed-form expression for transmission rate only according to the actual measurement of the channel gain in each time slot and thereby can avoid the deviation from prediction of the channel gain in future time slots. The numerical results demonstrate that the proposed algorithm can save a noticeable amount of energy.

This study proposes a finely quality of service (QoS)‐guaranteed algorithm to jointly optimise the throughput and energy efficiency in MU‐multiple‐input multiple‐output systems. The latency requirements of real‐time services are guaranteed by user scheduling in the first stage. The energy efficiency and system throughput are jointly optimised while the required transmission rate is finely guaranteed in the second stage. Simulation results show that the algorithm can achieve a good balance between the energy efficiency and throughput, and is superior to the existing schemes in terms of QoS guarantee.

This paper conducts outage analysis for cooperative hybrid automatic repeat request with incremental redundancy (C-HARQ-IR). A general time-correlated Nakagami fading channel including fast fading and Rayleigh fading as special cases is considered. An efficient truncated inverse moment matching method is developed to derive the outage probability in closed- form. The accuracy of the analytical results is verified by Monte Carlo simulations and the results reveal that C-HARQ-IR protocol can benefit from high fading order and low channel time correlation.

In this paper, an opportunistic cooperative HARQ system is analyzed. Different from prior analyses, time correlated fading channels are considered. Based on moment generation function and Laplace transform, the outage probability and throughput in terms of long-term average transmission rate (LATR) of this opportunistic cooperative HARQ system are derived in closed-forms. The accuracy of the analytical results is verified by computer simulations. From the analytical results, the impacts of the time correlation and other system parameters on the performance are investigated and the optimal packet rate selection to maximize the LATR is discussed.