The existing cognitive radio networks (CRNs) lack the ability to deal with the electronic attack of malicious users, which can destroy the normal communication of the cognitive users. To solve the problem, we propose a novel secure CRN by combining MIMO technique and low density parity check (LDPC) codes at the base-station (BS) and mobile stations (MSs), the electronic interference of the malicious users can be effectively weakened. The capacity and the outage probability of the proposed MIMO CRN are analyzed. The simulation results in quasi-static Rayleigh flat-fading channel show that the proposed secure MIMO CRN can effectively cancel electronic interference from the malicious users.

The existing cognitive network (CN) nodes do not support Differentiate-Serve (Diffserv) Quality of Service (QoS), and the existing Diffserv QoS scheme has not considered the link capacities between UDP subscribers and TCP subscribers of CN nodes. To solve these problems, a Diffserv CN node and Controlled-UDP (C-UDP) based fluid model are proposed for hybrid traffics' CN. The proposed C-UDP and CN node limit the data rates of UDP subscribers according to their priorities, and allocate the link capacities to different classes of TCP traffics and C-UDP traffics. The dynamic simulation results demonstrate the proposed CN node and C-UDP for the TCP/UDP hybrid traffics for CN to be valid.

This paper presents a new scheme for evaluating complex reciprocal and exponential functions in hardware. The proposed method utilizes a two-dimensional convolution algorithm to interpolate bivariate functions from tabulated function values in the complex domain. To reduce the memory requirements for lookup tables, the interpolation is decomposed into independent row and column computations, such that the same coefficient table can be shared. Three different interpolation kernels from degree-1 (linear) to degree-2 (quadratic Lagrange) and degree-3 (cubic Lagrange) are explored to find the optimal design parameters and the most acceptable trade-offs between performance and hardware resources. Moreover, a generic hardware architecture is designed to provide scalable implementation capabilities for computation precision and interpolation degree. To verify the proposed architecture, eight complex reciprocal and eight complex exponential design instances are implemented. The ASIC- and FPGA-based experimental results show that the proposed scheme can efficiently approximate the complex reciprocal and exponential functions with up to 16-bit precision, as well as achieve a considerable reduction of memory requirements compared with traditional bipartite and multipartite schemes. The proposed method is also applicable to other complex functions.

Classical network fluid model and RED algorithm are based on TCP flows in internet network, and they have not considered the UDP flows' effects in network. However, in real work of the network, the network link capacity is shared by the hybrid traffics: TCP flows and UDP flows, and UDP flows can occupy the original link capacity of TCP flow. Since there is no feedback control for UDP flows, the classical network fluid model and RED algorithm can not reflect and control the congestion of TCP/UDP networks. To solve the problem, we modify the classical AQM router into multiple queues AQM router with classifier. We express the proposed TCP/UDP AQM router by a linear time-delay system model. Then, by utilizing the 2-D Laplace-Z transform technique, we derive some explicit conditions that establish the relationship between the control parameter pmaxand the network stability. This paper first proposes parameter pmax's stability bounds for TCP/UDP routers for congestion control based on 2-D Hurwitz-Schur stability conditions. The simulation results verify that the proposed stability condition can gain the effective congestion control.

This paper provides parameter setting and 2-D local stability conditions for TCP/RED networks. In general, a network cannot avoid congestions due to the limit of network capacity. The RED scheme is one of the representative AQM that was proposed to avoid and alleviate network congestions. However, the issue of network stability with many TCP subscribers needs to be considered when setting the RED parameters, where the classical RED has not considered the problem. In this paper, we set up a linear time-delay system for the TCP dynamic behavior and derive some stability conditions with simple RED network parameters by utilizing the 2-D Laplace-Z transform technique. Simulation results show that the proposed stability conditions can gain the effective stability in regard to the router queue length.

Particle swarm optimization algorithm (PSO) has showed great advantage in solving multidimensional and non-linear problems, and it is easy to be applied. By improving binary particle swarm optimization (BPSO) algorithm and applying it in direct sequence code-division multiple-access (DS-CDMA) system as a multiuser detection algorithm, a BPSO multiuser detection (BPSO-MUD) is proposed in this paper and the relationship between the physical meaning of each variable in BPSO-MUD and DS-CDMA system is described clearly, followed by the discussion of highly efficient multiuser detection (MUD). Simulations show that these proposed detections are benefited greatly from the BPSO, they have significant performance improvements over conventional detection (CD), and they approach the performances without multiple access interference (MAI) in CDMA system; moreover they are easy to be applied in CDMA system.

This paper proposes a FIR-RAKE receiver algorithm that makes use of a pilot signal broadcast by the TD-SCDMA (time division-synchronous code division multiple access) base station to obtain channel parameter estimates in the downlink of TD-SCDMA wireless network. The algorithm can reduce multipath interference for the mobile units and with lower complexity of FIR implementation, where only one marching filter has been adopted. Performance analysis presented in the paper and computer simulations confirm that the proposed FIR-RAKE receiver algorithm achieves a better performance under typical multipath fading propagation conditions.