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OFDM (Orthogonal frequency division multiplexing) is one of the key techniques for 4th generation high data rate communications system. However OFDM suffers from high peak-to-average power ratio (PAPR) which substantially degrades the efficiency of a linear power amplifier. A new nonlinear companding transform using hyperbolic tangent sigmoid transfer function is proposed for PAPR reduction in this...
This paper proposes an adaptive modulation (AM) algorithm for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems with Vertical Bell Laboratories Layered Space-Time (V-BLAST) and orthogonal-triangular decomposition (QR) detection firstly. Then performance analysis is derived in closed form. Simulation results show that the theoretic bit error rate (BER) and...
This paper investigates the optimal bit and power allocation to minimize transmission power under system bit error rate (BER) and transmission rate requirements for multiple-input multiple-output (MIMO) systems with imperfect channel state information (CSI). A robust greedy algorithm is proposed and proved to be the optimal robust bit and power allocation by simulation. Simulation results also show...
This paper presents a new scheme for MIMO-OFDMA (multiple input multiple output-orthogonal frequency division multiple access) downlink resource allocation. This scheme intends to simultaneously enhance capacity and proportional rate fairness among users. A suboptimal power allocation method is also described in detail in this paper. The system objective is to maximize the total capacity subject to...
This paper puts forward two novel user-grouping algorithms for grouped MC-CDMA systems. The adaptive assignment for user-grouping plays an important role for link quality. We formulate the capacity-maximizing problem of user-grouping and analysis the optimal criterion for it. The derived optimal criterion has a similar form with signal to noise plus interference (SINR), with unassigned power included...
Typical ultra wide band (UWB) systems are built to meet quality of service (QoS) constraints under multiple access environment. We propose a UWB physical layer that adapts its number of time hops to efficiently meet QoS requirements. The proposed adaptive UWB uses side information to know the current QoS and adjusts its number of time hops accordingly. The system employs adaptive time hopping pulse...
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