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Orthogonal frequency division multiplexing (OFDM) systems are sensitive to time and frequency offset errors. In this paper, a method of joint timing and frequency synchronization for OFDM systems has been proposed based on preamble structure defined in IEEE 802.16 standard. The proposed method in coarse frame detection has good robustness and anti-noise ability. The coarse and fine frequency offset...
This paper proposes a cooperative game theoretic resource allocation scheme for downlink OFDMA wireless networks. We define a user??s payoff as a function of his data throughput. Then the source allocation can be modeled as a cooperative game to maximize the aggregate payoff of the users. To achieve the Nash bargaining solution (NBS) of the game, a suboptimal subcarrier allocation is first performed...
In this paper, a novel resource allocation algorithm is proposed for multi-service OFDMA systems. The multi-objective optimization model is established for resource allocation, according to the different QoS requirements of different services. In order to achieve the suboptimal solution for the multi-objective optimization problem, this paper proposes a novel hierarchical algorithm, and adopting some...
This paper investigates the design of robust transmit beamforming for the secondary user (SU) when it co-exists with the primary user (PU) in a cognitive radio network, and the SU??s transmitter (SU-Tx) is equipped with multiple antennas. It is assumed that the channel knowledge for the link from SU-Tx to PU is partially known only. By formulating the problem as maximizing the transmission power to...
Prepaid services require the billing system to offer real-time billing and service control in streaming media applications. However, current billing approaches suffer from high risk of bad debts to operators or lack of the function of service termination during service consumption. On the basis of streaming media services?? features, a streaming media online charging system (SMOCS) is developed in...
A new method for amplitude-only optimization of circular planar slot array antennas is presented. In order to form a given three-dimensional antenna pattern for array antennas, variable metric algorithms, Davidon-Fletcher-Powell (DFP) and Broyden-Fletcher-Goldfarb-Shanno (BFGS) were jointly used to optimize the amplitude distribution of the current excitations. Thus, the optimized main lobe of the...
Cross-layer interaction is an indispensable part of cross-layer design, which has been proved to greatly improve the performance of wireless networks. In this paper, a scheme for cross-layer interaction management (CLIM) is proposed. It has the following distinct advantages. Firstly, CLIM achieves efficiency by considering the modularity of protocol stack. Secondly, in CLIM, implementing cross-layer...
In this paper, linear MIMO transceivers design for minimizing the combination of symbol estimation errors subject to lp-norm constraint is investigated. To simplify the optimization problem, we first derive the structure of optimal precoder and decoder matrices. Then, instead of considering each constraint in a separate way, we develop a unifying framework by employing the directional derivative method...
A joint source channel coding scheme has been proposed to optimize the mapping vector quantizer (VQ)-modulator symbols. The proposed two-step-algorithm optimizes first the mapping source codes-modulator symbols, and then optimizes VQ against the channel noise. To reach the target codebook size these steps are repeated iteratively. To show the proposed algorithm performance, it has been applied to...
Dynamic spectrum management (DSM) is an important technique for mitigating crosstalk noise in multi-user digital subscriber line (DSL) environments. Until now, most of the proposed algorithms for DSM have been designed solely for the purpose of bitrate maximization. These algorithms assume a fixed maximum total power and neglect the energy consumption in DSL modems. However, since recently there is...
PAPR problem is a major drawback of multicarrier transmission system, known as orthogonal frequency division multiplexing (OFDM) or discrete multitone (DMT). Tone reservation (TR) is one of the PAPR reduction methods. Minimum spanning circle method (MSCM) is a realization of TR with low computational complexity. In an OFDM system with multiple reserved tones, extended MSCM is used to get the reduction...
The capacity of multi-channel multi-hop network can be substantially increased by equipping each node with multi-radio which allow for simultaneous transmission, but there are still much interference between those transmission links without appropriate channel assignment due to limited non-overlapping channels, so further optimization is need to carefully assign channel for radios. This paper considers...
In this paper, we investigate the power allocation problem involving how to multiplex cooperative routes in multi-source ad hoc wireless networks. The aim is to provide a route-multiplexing scheme with minimal total power consumption given spectrum efficiency constraints. Three protocols: full combination with interference (FCI), full combination with time sharing (FCTS) and selection between interference...
Cooperative networks have been considered for their spatial diversity benefit in wireless communications. The signal in the cooperative networks can be transmitted by a repetitive manner or using space-time codes. For both transmission schemes, we consider the error performance and resource allocation employing differential modulation which bypasses the channel estimation at the transceiver. We derive...
In this work the authors show how the asymmetry characteristics of wireless network strongly affects the Web response time of user. It is found that uplink delay degrades Web performance because additional bytes overhead and time overhead are introduced. On the other hand, the study also shows that reduction of Web response time is possible through protocol optimization on different layer of protocol...
Previous works about spectrum sharing in licensed band are all based on a default assumption that the secondary users are equipped with cognitive radios, which enable them to accomplish the spectrum sensing and the ensuing spectrum access. Unfortunately, current wireless communication devices generally lack any functionality of cognition. It is rather challenging to enable such wireless devices to...
In cognitive radio cellular networks (CogCell), the secondary users (SUs) can be admitted to the base station (BS) provided that the interferences to the primary users (PUs) are no higher than the pre-defined thresholds. In addition, different SUs may make different payments and require different quality of service (QoS). In this paper, we investigate the maximally achievable revenue obtained from...
This work describes a novel approach to the base station deployment problem based on artificial immune systems. It is a multi-objective optimisation problem (MOP), since it involves a large number of variables and design constraints. The multi-objective optimisation algorithms based on artificial immune systems (MO-AIS) are a new class of evolutionary algorithms. The Binary-coded Multi-objective Optimisation...
In this paper, we develop a joint design method of network-channel low density parity check codes (LDPC) codes by constructing joint network-channel parity check matrix. Random network coding is performed to provide side information for both the source and relay??s transmission. This system matrix makes an easy way to collect all independent signal copies to provide a spatial diversity gain. And the...
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