Jia Shi-lou

Link reliability based hybrid routing for tactical mobile ad hoc network

Tactical mobile ad hoc network (MANET) is a collection of mobile nodes forming a temporary network, without the aid of pre-established network infrastructure. The routing protocol has a crucial impact on the network performance in battlefields. Link reliability based hybrid routing (LRHR) is proposed, which is a novel hybrid routing protocol, for tactical MANET. Contrary to the traditional single path routing strategy, multiple paths are established between a pair of source-destination nodes. In the hybrid routing strategy, the rate of topological change provides a natural mechanism for switching dynamically between table-driven and on-demand routing. The simulation results indicate that the performances of the protocol in packet delivery ratio, routing overhead, and average end-to-end delay are better than the conventional routing protocol.

AOHR: AODV and OLSR Hybrid Routing Protocol for Mobile Ad Hoc Networks

A hybrid routing protocol named AOHR (AODV and OLSR hybrid routing) for mobile ad hoc networks is proposed in this paper. In AOHR, each node maintains topology information of a zone with radius not larger than a set value. By the proactive property of OLSR, when a node wants to communicate with another node within its zone, packets can be transmitted directly. Otherwise, a routing request procedure will be invoked by the reactive property of AODV. In addition, AOHR utilizes MPRs (multipoint relays) to reduce overheads of route requests. This paper also proposes dynamic zone radius maintenance for AOHR to dynamically adapt to various scenarios. Analysis and simulation results show that AOHR combines the characters of high data delivery fraction, low overheads, and short delay in AODV with the characters of optimized routing length in OLSR, which means that AOHR is immune from topological structures

Utility function based fair data scheduling algorithm for OFDM wireless network

Abstract A system model is formulated as the maximization of a total utility function to achieve fair downlink data scheduling in multiuser orthogonal frequency division multiplexing (OFDM) wireless networks. A dynamic subcarrier allocation algorithm (DSAA) is proposed, to optimize the system model. The subcarrier allocation decision is made by the proposed DSAA according to the maximum value of total utility function with respect to the queue mean waiting time. Simulation results demonstrate that compared to the conventional algorithms, the proposed algorithm has better delay performance and can provide fairness under different loads by using different utility functions.

Efficiency-aware and fairness-aware joint-layer optimization for downlink data scheduling in OFDM

Efficiency and fairness are two crucial issues to be considered for resource allocation in multi-user wireless networks. Based on the joint optimization of physical layer and data link layer, an optimization model is derived to achieve efficient and fair downlink data scheduling in multi-user OFDM wireless networks by maximizing the total utility function with respect to the average waiting time of user queue. A dynamic sub-carrier allocation algorithm (DSAA) based on the optimization model is proposed in order to obtain the maximization of the total scheduling utility. Efficiency is improved by combining DSAA with time scale interference predictor (TSIP) which at large time scales predict ON/OFF period of user data with temporal correlation structure across multiple time scales in multi-user interference environment. Simulation results verify the efficiency and fairness of the scheme.

Analyses and compensation for radar target angular glint

Angular glint caused by a target of dual point sources is discussed in phase gradient method. Deterministic relation between phase gradient and RCS is deduced. On the basis of that, a RCS based compensation method of angular glint is presented. The validity is verified by simulation. For target of multi-point sources, compensation for angular glint error is similar if it is treated as a target of dual point sources.

Doubly-selective MIMO-OFDM channel identification using superimposed training

In order to estimate doubly-selective MIMO-OFDM channel meanwhile improve bandwidth efficiency, a superimposed training (ST) method is considered. The time-varying channel is assumed to be approximated by a complex exponential basis expansion model (CE-BEM). A periodic (non-random) training sequence is arithmetically superimposed at a low power to the information sequence at the transmitter, channel parameters could be obtained without loss of bandwidth. The unknown information sequence can be interference to the ST channel estimation method, in this paper an iterative ST (IST) channel estimation method is presented to improve channel estimation performance exploiting equalized information symbols. From the result of computer simulations, we show that the proposed method can achieve good MSE and BER performance.

Heuristic based data scheduling algorithm for OFDMA wireless network

Abstract A system model based on joint layer mechanism is formulated for optimal data scheduling over fixed point-to-point links in OFDMA ad-hoc wireless networks. A distributed scheduling algorithm (DSA) for system model optimization is proposed that combines the randomly chosen subcarrier according to the channel condition of local subcarriers with link power control to limit interference caused by the reuse of subcarrier among links. For the global fairness improvement of algorithms, a global power control scheduling algorithm (GPCSA) based on the proposed DSA is presented and dynamically allocates global power according to difference between average carrier-noise-ratio of selected local links and system link protection ratio. Simulation results demonstrate that the proposed algorithms achieve better efficiency and fairness compared with other existing algorithms.

PVPSU: Publicly Verifiable and Parallel Share Updates for Mobile Ad Hoc Networks

Based on RSA algorithm, this paper provides a publicly verifiable and parallel share update algorithm for mobile ad hoc networks. According to Diffie-Hellman assumption and public verifiability, this new algorithm improves security and robustness. In addition, communication rounds have been decreased from three to two. This paper also proposes a new multiplicative shuffle scheme for share updates. Our simulation and implementation evaluate and confirm that the solution is effective

Analysis on the Performance of Explosive Magnetic Generator of Frequency based on equivalent circuit

It was considered that the precondition of generating high frequency radiation was that the appended capacitor brought oscillating current signals in an explosive magnetic generator of frequency (EMGF). As a result, on the basis of equivalent circuit, by analyzing the energy losses, the variation of EMGFs current was studied, and the reason for the fish-shaped envelope of oscillating current was explained in this paper. Also, the principle of high frequency radiation was interpreted by studying the fish-shaped current energy spectrum. All the analyses were based on equivalent circuit and redounded to comprehend the operating principle of EMGF

High stable power control of a laser diode

In this paper, the low and the high frequency noises of a laser diode have been analyzed. Based on the analysis a novel scheme that adapts analog and digital hybrid techniques is proposed to stabilize the output power of a laser diode. With the hybrid controller, the low and the high frequency noises of a laser diode are conspicuously reduced. By accurate calculation, the short-term stability of the output power of laser diode reaches ±0.55‰, and the long-term stability is ±0.7‰.