Search

Unmanned aerial vehicles (UAVs) have attracted a lot of attention due to their enormous potentiality in civil and military applications over the past years. In order to allow accurate control action of UAV, a robust and real-time state estimation technique is required. In this paper, we propose a Kalman filter based UAV state estimation technique when the communication takes place over wireless links in an Internet of Things (IoT) network. We consider that a set of sensors observes the state of the UAV and transmits the observation to a control center (central server) over a distributed wireless IoT network. To deal with the communication impairments due to wireless communication links between the UAV's sensors and the IoT system components, e.g., IoT gateways, a Bose–Chaudhuri–Hocquenghem coded communication system is presented. Based on the received signals at the IoT gateways, a global state estimation technique is proposed. Performance of the proposed communication and estimation scheme is demonstrated through numerical results for different conditions. From the comparison with a conventional estimation scheme, it is observed that the proposed scheme significantly outperforms the conventional scheme in terms of state estimation and error performance. [ABSTRACT FROM AUTHOR]

An expression for the bit-error rate (BER) of noncoherent frequency-shift keying with a nonfaded desired signal in the presence of N Rayleigh-faded unsynchronized cochannel interferers (UCCIs) and additive white Gaussian noise is first derived. This result can be used to obtain the BER for a faded desired signal. For a large number of UCCIs, numerical evaluation of this expression can be quite time-consuming. An approximate method that yields fairly accurate results is thus described. Numerical results show that for a Rician-faded desired signal with a strong specular component in an interference-limited environment, the BER decreases slightly with N whereas for a Rayleigh-faded desired signal, the BER varies very little with N. A comparison to the BER performance with synchronized cochannel interferers is also provided. Index Terms--Bit-error rate, fading channels, frequency-shift keying, Gaussian noise, unsynchronized cochannel interference.

SUMMARY This paper proposes a cooperative quadrature physical layer network coding (CQPNC) scheme for a dual-hop cooperative relay network, which consists of two source nodes, one relay node and one destination node. All nodes in the network have one antenna, and the two source nodes transmit their signals modulated with quadrature carriers. In this paper, a cooperative quadrature physical layer network coded decode-and-forward (DF) relay protocol (CQPNC-DF) is proposed to transmit the composite information from the two source nodes via the relay node to the destination node simultaneously to reduce the number of time slots required for a transmission. The proposed CQPNC-DF relay protocol is compared with time-division multiple-access amplify-and-forward (TDMA-AF), TDMA-DF, cooperative network coded DF (CNC-DF) and cooperative analog network coded AF (CANC-AF) relay protocols to demonstrate its effectiveness in terms of bit error rate (BER) and system throughput under different propagation conditions. The simulation results reveal that the proposed CQPNC-DF relay protocol can significantly improve the network performance. Compared with two TDMA schemes and CNC-DF, the proposal can provide up to 100% and 50% throughput gains, respectively. Moreover, no matter what the scene, the proposed scheme always has the lowest BER in the low SNR region. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, we study the blocking and dropping probability of mobile users in the multi-service cellular systems with mobile users. Based on the idea that different services may require different signal-to-interference ratios and different reuse factors, we proposed a channel allocation scheme called channel partitioning to support different services using different reuse factors. Under channel partitioning scheme, the channels in each cell are divided into two or more sets of channels and each set of the channels supports certain service, depending on the required reuse factor of the service. We first apply this channel partitioning with fixed channel allocation scheme called fixed channel partitioning (FCP), where a three-dimensional Markov chain is developed to analyze the impact of the mobile user. After that a simpler model, which can estimate the numeric result from the closed-form solution, is presented to make the analysis easier. In order to cater for the traffic variation between services and between cells, a dynamic channel partitioning with flexible channel combination scheme, called FDCP, is proposed to support multiple services. This FDCP tries to minimize the effect of assigned channels on the availability of channels for use in the interfering cells. The analysis and the simulation results show that for equal arrival rate of two services, the proposed FCP and FDCP scheme can provide about 32% and 54% improvement, respectively, in terms of grade of service as compared with conventional FCA scheme using a single reuse factor to support two services for the mobile users. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The trend of the wireless communication system is to provide various types of services such as voice, data and video etc. Due to the limited radio resources with international agreement, how to achieve the optimum system capacity becomes a paramount issue. In this paper, we use the idea of channel partitioning (CP) employing different reuse factors to support multiple services that require different signal-to-interference ratios (SIRs) in cellular systems. Two types of services are considered in this paper. Thus, we use a large reuse factor to support high SIR required service while we use a small reuse factor to support low SIR required service. From the system point of view, the average reuse factor becomes smaller and the system capacity can be improved. The system performance of CP with fixed channel allocation (FCA) scheme, namely fixed channel partitioning (FCP), is first proposed and analysed using Markov chain in a single cell model. Then a dynamic channel allocation scheme with CP called dynamic channel partitioning with interference information (DCP-WI) is proposed and studied in the multiple-cell model by computer simulation. The analysis and simulation results show that our proposed schemes can improve the system capacity depending on the traffic load fraction for each service. For equal arrival rate for both services, FCP and DCP-WI provide about 33 and 60% capacity improvement respectively over a conventional FCA system using a single reuse factor to support two types of services. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]