Koenraad Mouthaan

Robust Linear Transceiver Design in MIMO Ad Hoc Cognitive Radio Networks with Imperfect Channel State Information

The joint linear transceiver design for Multiple-Input Multiple-Output (MIMO) \adhoc cognitive radio networks when the channel state information (CSI) is uncertain is discussed in this paper. The uncertainty in CSI is modeled using Stochastic Error (SE) and Norm Bounded Error (NBE) models. The Sum-Mean Square Error (SMSE) performance is used to formulate the design problem. To optimize the network, the transmit power budget for secondary user transmitters and the maximum allowed interference at primary user receivers are constrained. In the design methodology, the network parameters are optimized to best serve the users when the worst possible channel realizations occur. It is shown that for the SE model of uncertainty, this problem can be cast as a Second Order Cone Problem (SOCP), while for the NBE model, the problem becomes a Semi-Definite Program (SDP). These two problems are solved efficiently using the numerical solver packages YALMIP and SDPT3. Finally simulation results are presented to evaluate the performance of the proposed methods.

180

Reflection-type phase shifters (RTPSs) of 180° and 90° using over-coupled Lange couplers to obtain multioctave bandwidth are presented. A thorough theoretical analysis of the effect of coupler parameters on the RTPS performance is provided. The impact of coupler parameters on the RTPS performance is further illustrated with vector plots. Each measured phase shifter is comprised of an over-coupled Lange coupler, two low-loss single-pole double-throw switches, and two pairs of LC reflection loads on a Rogers RO4003C substrate with a thickness of 0.8 mm (32 mil) and 1.5 mm (60 mil). By using the 1.5-mm substrate, the coupling can be increased. Phase shifts of 90° and 180° using Lange couplers with 2-3-dB coupling in steps of 0.2 dB are designed, fabricated, and measured. The experimental results show that an over-coupling of 2.2 dB is able to obtain a return loss larger than 10 dB over a 127% bandwidth from 550 to 2450 MHz for all states. Worst case measured insertion loss and phase error on the 0.8-mm substrate with an over-coupling of 2.8 dB is 2.0±0.8 dB and ±5.8°, respectively, for both 180° and 90°phase states. On the 1.5-mm substrate with an over-coupling of 2.4 dB, they are 1.8 ±1 dB and ±16°, respectively, for both phase states.

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In this paper the linear beamforming design of a point to point relay system having multiple antennas at the transmitter, the relay and the receive side is addressed. The Channel State Information (CSI) is assumed to be perfectly known for the link from the source to the relay station. However, it is assumed that CSI from the relay station to the destination is imperfectly known. This uncertainty is described using stochastic and deterministic models known as Stochastic Error (SE) and Norm Bounded Error (NBE) models. The problem formulation is based on the Mean Square Error (MSE) of the signal at both ends of the transmission channel. This problem is constrained to satisfy the transmit power limitation of the relay station. It is shown that both the MSE of the system and the transmit power have a Second Order Cone (SOC) structure. The design problem for the SE model, is recast as a Second Order Cone Program (SOCP) while for the NBE model, the same design problem is a Semidefinite Program (SDP). Using the SE model, the average performance and using the NBE model, the worst-case related performance measure is guaranteed. Both problems are solved numerically and simulation results are provided.

and 90

The problem of nonlinear transceiver optimization in a multi-tier Multiple-Input Multiple-Output (MIMO) network in Cognitive Radio Network (CR-Net) configuration is studied. The employed transmission schemes are based on the Matrix Decision Feedback Equalizer (DFE) and Tomlinson-Harashima Precoder (THP). It is assumed that the Channel State Information (CSI) is not known perfectly. % The former type of uncertainty is modeled using Stochastic Error (SE) model while the latter one is modeled using Norm Bounded Error (NBE) model. The performance measure used for optimizing the network is based on the sum Mean Square Error (MSE) of symbol estimation in the system. The design problem is constrained by the transmit power of the Secondary Users (SUs) as well as the maximum allowed interfering power to the Primary Users (PUs). The design problem is not jointly convex in its design variables and has infinitely many constraints. To overcome this, a suboptimal iterative procedure is proposed. Based on the chosen model for uncertainty, the two resultant problems are Semidefinite Programs (SDP). These two problems are solved numerically. Finally simulations results are provided to assess the performance of the system.

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This paper presents two novel modular ladder type surface acoustic wave (SAW) filters. The first topology realizes a shift of center frequency and bandwidth (BW) and the second topology a shift of band edge. In the designs, the acoustic resonators are reused and the need for passive elements is reduced. Experimental results are presented for the 700 MHz frequency band currently allocated to Long Term Evolution (LTE). Parasitics caused by the packaging, interconnect and non-ideal switches are incorporated in the design using a linear circuit solver and three dimensional electro-magnetic (3D EM) commercial simulator. The measured results agree well with the simulations. In the filter with shifted center frequency and BW, two filter states with a BW of 1.4% and 1.7% are realized with a center frequency shift of 3.1%. In the filter with shifted lower band edge, two filter states with a BW of 3% and 1.7% are obtained.

Reflection-Type Phase Shifters Using Over-Coupled Lange Couplers

The problem of robust linear transceiver design in Multiple-Input Multiple-Output (MIMO) ad hoc Cognitive Radio Networks (CR-Nets) is studied in this paper. In this problem multiple interfering MIMO links are active within the service range of a Primary Radio Network (PR-Net) for which, unlike in conventional design problems, the Channel State Information (CSI) is not known perfectly. The imperfection in CSI is modeled using norm-bounded uncertainty matrices. The design problem is formulated to provide the minimum Sum-Mean Square Error (SMSE) of all the links while the transmit power of Secondary Users (SUs) is limited and the amount of interfering power toward the Primary users (PUs) is controlled. This problem is not convex, because its objective function is non-convex in nature and it has semi-infinite robust constraints. To overcome these limitations an iterative solution, which is based on the relaxed version of this problem, is provided. The problem is then solved numerically. Finally simulation results are provided to demonstrate the performance of this method.

Robust linear beamforming for MIMO relay with imperfect Channel State Information

A new method for blind separation and bearing estimation of wavefronts in a smart antenna scheme, which is based on the usage of artificial neural networks (ANN) is presented here. Because of ldquothe curse of dimensionality,rdquo especially in the cases having many antenna elements, in uniform linear, circular or planar arrays, it is important to find a method which makes it feasible to use the ANNs. The proposed method, do not walk along the road of well-known method of correlation-coefficient training. In contrast this method uses the truncated version of their spectral representations. The fast Fourier transform (FFT) and discrete wavelet transform (DWT) are employed to provide the spectral representations. The simulation scenario is set up to demonstrate that the results is applicable to realistic cases such as urban, non-line of sight, and indoor environments. For the sake of this purpose, coherent signals are employed in simulations. In this case, most conventional methods are not applicable, because they are built on some statistical assumptions which implies that the received signals by array must be independent.

Collaborative Nonlinear Transceiver Optimization in Multi-Tier MIMO Cognitive Radio Networks with Deterministically Imperfect CSI

A dual band bandpass filter is presented with individual tuning of each bandpass center frequency. This feature offers a significant improvement over previous designs. The two center frequencies are 1.1 GHz and 2.3 GHz and the tuning ranges are 60 MHz and 90 MHz and the insertion loss of the lower and upper center frequencies are better than 2.1 dB and 3.5 dB respectively.