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This paper presents noncooperative and cooperative security transmission schemes for multiple-input multiple-output (MIMO) Gaussian wiretap channel with one helper for antenna configuration with arbitrary number. In these two schemes, the transmitter performs beamforming based on generalized singular value decomposition (GSVD), where an appropriate power allocation algorithm is utilized. Meanwhile,...
In order to solve the problem the existing vertical handoff algorithms of vehicle heterogeneous wireless network do not consider the diversification of network’s status, an optimized vertical handoff algorithm based on markov process is proposed and discussed in this paper. This algorithm takes into account that the status transformation of available network will affect the quality of service (QoS)...
The previous Decentralised Cognitive Medium Access Control (DC-MAC) protocol allows Secondary Users (SUs) to independently search for spectrum access opportunities without the need for a central coordinator. DC-MAC assumes that the detection scheme is ideal at the Physical (PHY) layer. In fact, a more complex detection algorithm is impractical in distributed spectrum sharing scenarios. Energy Detection...
This paper designs a new precoding for an OFDM system without cyclic prefix (CP), to achieve the same function with CP used in CP-OFDM system. After the analysis of CP-OFDM system, this paper constructs a modulation matrix; on this basis, introduces memory characteristics, as well as symbols feedback, and designs a time domain precoding (TDP) module. By adding the TDP module into TD-LTE link, its...
Motivated by the demand for alternative ways to enhance wireless security, this paper proposes a technique to enhance wireless security at physical layer. It takes advantage of rich multipath environment to focus radio energy on some desired spatial spot, while achieving nulling at other spots. This can be viewed as a physical-layer security enhancement. What makes spatial focusing and nulling possible...
Focusing on the problem that the co-frequency interference of the downlink channels in multi-cell of multi-out multi-input (MIMO) systems, this paper used the adaptive network precoding based on the SJNR to reduce the inter-cell interference. First of all, the adaptive precoding design based on the SJNR criteria is given. In this design, each base station use independent precoding approach to suppress...
The sensing performance of local detection in cognitive radio systems will be degraded when the channel experience fading and shadowing, and hidden terminal problem is inevitable for the primary transmitter-sensing. To overcome this problem, cooperative spectrum sensing has been proposed. We propose a twice-cooperative sensing algorithm to improve the sensing performance. By comparing to the single-cooperative,...
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