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OFDM 2012, 17th International OFDM Workshop 2012 (InOWo'12); Proceedings of

Date 29-30 Aug. 2012

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Displaying Results 1 - 25 of 26
  • Peak-to-Average Power Ratio Reduction in OFDM via Sparse Signals: Transmitter-Side Tone Reservation vs. Receiver-Side Compressed Sensing

    Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (374 KB)  

    Two approaches, dual to each other, for peakto- average power ratio reduction based on the use of sparse signals are assessed and compared. In tone reservation a small number of carriers is adjusted. When performing clipping only a few samples are typically affected. We utilize the possibility to optimize the transmitter-side clipping and tailor it to the corresponding receiver-side signal recovery employing compressed sensing. Moreover, we show how tone reservation and clipping can be combined. Using only few tones for algorithmic optimization at the transmitter and combining this with clipping of residual peaks (to be recovered at the received), a very attractive PAR reduction scheme results. View full abstract»

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  • Performance Comparison of Adaptive Modulation and Coding in OFDM Systems Using Signalling and Automatic Modulation Classification

    Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (279 KB)  

    This paper compares the system performance of signalling and automatic modulation classification in adaptive orthogonal frequency division multiplexing (OFDM)- based systems in time-division duplex (TDD) mode. In previous theoretical contributions, transmitter-side joint adaptive modulation and coding (AM+C) techniques have been proposed which can be used to either increase the data rate or, alternatively, improve the link reliability. Since the receiver must be synchronized to the transmit parameters, the required signalling overhead reduces the benefit of adaptive modulation and coding when applied to practical systems. Numerical results in terms of the effective data bandwidth efficiency reveal the potential of recently developed automatic modulation classifiers as an alternative to conventional signalling schemes. Index Terms ?? OFDM, adaptive modulation and coding, automatic modulation classification, signalling View full abstract»

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  • Hybrid one-/two-way transmission scheme for bidirectional multi-user relaying under asymmetric rate requirements

    Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (238 KB)  

    A single cell scenario consisting of a multiantenna base station and several single antenna mobile stations is considered. An intermediate non-regenerative multi-antenna relay station is used to support the bidirectional communications. In such a scenario, the required data rates for up- and downlink are typically different which is considered by introducing asymmetric rate requirements. A transmission via multiple orthogonal subcarriers as used in OFDM is investigated and a hybrid one-/twoway transmission scheme per subcarrier is proposed to increase the achievable sum rates under the asymmetric rate requirements. To handle the asymmetric rate requirements at the relay station, a weighted self-interference aware relay transceive filter per subcarrier is applied. Furthermore, different transmit and receive filter strategies at the base station are investigated. Performance results show that higher sum rates can be achieved with the hybrid one-/two-way relaying scheme than via a pure two-way relaying scheme. View full abstract»

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  • FPGA Implementation of ZF-THP for MU-MISO-OFDM Systems

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    In wireless multi-user communication systems with multi-antenna base stations the application of precoding techniques is strongly recommended for accurate detection of the signals at the mobile stations if no cooperation between them is desired. The Tomlinson-Harashima Precoding (THP) for MIMO channels provides an excellent performance combined with low complexity at the receivers. In this contribution an efficient FPGA implementation of Zero- Forcing THP is presented. It is well suited for the modular architecture of base stations. A high throughput is achieved by parallelization and pipelining. The developed fixed-point design obtains the same bit error rate performance as an ideal floating-point precoding. View full abstract»

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  • A Game theoretical approach for spectrum sharing in cognitive radio systems with payoff perturbations

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (285 KB)  

    We study a spectrum allocation game where K cognitive radio systems compete for a number of free resource blocks in frequency domain. In particular, we concentrate on the impact of the perturbations in the payoff functions and the problem of equilibrium selection. Based on the simulated data throughput, we first address the problem of designing an appropriate spectrum allocation game. Our study shows that if we can persistently increase the accuracy of the simulation results, we are able to find the approximate Nash equilibria, which are arbitrarily close to the Nash equilibria of the real spectrum allocation game. Then, we study the problem of equilibrium selection, where we exploit the concepts of payoff dominance and the focal-point effect to select a unique Nash equilibrium. At last, we demonstrate the performance of the spectrum allocation game in an LTE system context. Index Terms ?? Cognitive radio, spectrum sharing, game theory, LTE. View full abstract»

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  • Time and Frequency Resource Allocation in OFDMA Wireless Mesh Networks

    Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    A wireless network with a mesh topology works reliably and offers redundancy. In modern broadband wireless mesh networks that use MIMO and OFDMA techniques, the problems of time, frequency, and space resource allocations are different from a cellular system and more complicated due to system architecture and distributed control and management. This paper focuses on the resource allocation problem of the OFDMA system and we define the term of separability order. For simple topologies like the grid configuration, the allocations are simple and an optimal solution can be shown, but for an arbitrary architecture we need advanced tools and we use Graph Theory tools to present two different algorithmic solutions, to allow frequency reuse. Index Terms ?? Wireless mesh networks, OFDMA, resource allocation, graph colouring, graph theory. View full abstract»

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  • Partial Scrambling PAPR Reduction for Multi-Code Vector Coding in Adaptive Modulated MIMO Systems

    Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (305 KB)  

    Multi-Input Multi-Output (MIMO) Vector coding (VC) transmission with adaptive modulation is an effective technique to enhance transmission performance in frequency selective wireless channels. The VC is a kind of code-division multiplexing (CDM) by which eigenvectors of channel autocorrelation matrix are used as spreading code. A major disadvantage of the VC is that the transmit signal exhibits high peak-to average power ratio (PAPR), which causes nonlinear distortion and/or power efficiency degradation at a power amplifier, similarly to OFDM and CDM systems. As a solution to this problem, selected mapping (SLM) PAPR reduction techniques have been studied. This paper presents a partial scrambling SLM PAPR reduction method for multi-code VC transmission in adaptive modulated MIMO systems. In this method, PAPR of the transmit signal is reduced to scramble bit sequence mapped on limited number of code vectors in VC systems. In addition, the maximum amplitude of transmit signal in each transmission block is reduced only when the maximum peak amplitude exceeds a given threshold value. Simulation results clarify that the partial scrambling method achieves better average throughput performance than the conventional method, although almost identical PAPR reduction performance is obtained for MIMO VC systems in an attenuated six-path Rayleigh fading condition. Index Terms ?? Vector coding, Peak-to-average power ratio (PAPR), PAPR reduction, MIMO View full abstract»

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  • Clipping-Based Iterative PAPR-Reduction Techniques for FBMC

    Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (743 KB)  

    Orthogonal Frequency Division Multiplexing (OFDM) is the most favored modulation technique in multicarrier wireless communications. Recently, the Filter Bank Multicarrier (FBMC) modulation scheme has drawn attention due its low Adjacent Channel Leakage Ratio (ACLR), which makes it especially suitable for Cognitive Radio (CR) applications. In multicarrier schemes the large dynamic range of the signal is a common problem, both FBMC and OFDM signals have high Peak-to-Average Power Ratio (PAPR). If nonlinear distortions are present, this large PAPR can lead to spectral regrowth causing harmful interference in the neighboring frequency bands. In this paper clippingbased PAPR-reduction schemes aided to reduce the PAPR of FBMC signal are presented. A comparison is given for both transmitter and receiver oriented methods. Index Terms ?? FBMC, PAPR-reduction, Clipping, Iterative. View full abstract»

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  • An OFDM WLAN Multicast Hybrid Erasure Correction Prototype with Feedback Aggregation and Rate Adaptation

    Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    Aggregation of multicast feedback in time is evaluated herein with respect to physical layer rate adaptation in OFDM based WLANs. An opportunistic scheduler with perfect channel knowledge is used as an upper limit for multicast throughput. We find that feedback aggregation multicast performs close to this limit. In realistic fading scenarios, delay constrained audio-visual streaming performance of a hybrid overlay FEC prototype implementation ?? including feedback aggregation and rate adaptation ?? is evaluated by simulation. In this context, a popular unicast rate adaptation mechanism is extended to multicast streaming, and its residual error performance is improved significantly by simple means. Index Terms ?? OFDM; 802.11; MBMS; wireless multicast; feedback aggregation; rate adaptation View full abstract»

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  • Opportunistic forwarding in multi-hop OFDMA networks with local CSI

    Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    In multi-hop networks, conventional unipath routing approaches force the data transmission to follow a fixed sequence of nodes. In this paper, we widen this path to create a corridor of forwarding nodes. Within this corridor, data can be split and joined at different nodes as the data travels through the corridor towards the destination node. To split data, decode-and-forward OFDMA is used since with OFDMA, one can exploit the benefits of opportunistically allocating different subcarriers to different nodes according to their channel conditions. To avoid interference, each subcarrier is only allocated once per hop. It is assumed that only local channel state information (CSI) for the next hop towards the destination is available at the nodes, i.e. it can not be guaranteed that a certain node is able to forward its received data in the next hop. This leads to additional transmission phases decreasing the overall network throughput. In this paper, different opportunistic forwarding algorithms are presented which differ in the resource allocation strategy and in the amount of cooperation required between the nodes. Simulations show that in multihop networks, corridor-based routing using opportunistic forwarding with a proper resource allocation strategy outperforms conventional unipath routing approaches in terms of achievable throughput, especially in case of a node drop out. Index Terms ?? OFDMA, routing, local CSI. View full abstract»

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  • Improved Decentralized Fuzzy Q-learning for Interference Reduction in Heterogeneous LTE-Networks

    Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (265 KB)  

    Recently, the concept of Self Organizing Networks (SON) has received significant attention in the context of Heterogeneous Networks (HetNets) to overcome indoor coverage problems as well as to improve the efficiency of current macrocell systems. Nevertheless, the detrimental factor in such networks is the co-channel interference between macrocells and small cells (femto, pico, relay), as well as among neighboring small cells which can dramatically decrease the overall capacity of the network. In order to cope with network densification and heterogeneity, selfconfiguring and self-optimizing strategies are of utmost importance to boost network capacity and control interference among different tiers. In this paper, we focus on decentralized cross-layer interference mitigation techniques in a Orthogonal Frequency Division Multiple Access (OFDMA) based HetNet deployment, whereby small cells autonomously optimize their downlink transmissions. We propose a Reinforcement Learning (RL) framework, based on an improved decentralized Q-learning algorithm for small cells sharing the macrocell spectrum. Since the major drawback of Qlearning is its slow convergence, we propose an improved effective initialization procedure. The proposed algorithm will be compared with a basic Q-learning algorithm, with Fuzzy Q-learning and basic approaches from literature. Interestingly, our proposal protects especially the so-called 5-th% cell-edge macro User Equipments (UEs) and is very close to the case that no small cells are activated as interferers in the system by at the same time enhancing the small cell performance. Index Terms ?? LTE, Heterogeneous Networks, Decentralized Interference Management, Cross-layer Interference, Reinforcement Learning, Fuzzy Q-learning. View full abstract»

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  • OFDM-MFSK as a Special Case of Noncoherent Communication Based on Subspaces

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (125 KB)  

    The combination of OFDM and FSK leads to attractive wireless transmission methods for fast timevarying channels because no channel knowledge is required in the receiver. Their drawback is the moderate or bad bandwidth efficiency. We show in this paper that OFDMMFSK and its multitone variant are special cases of more general methods which use vector subspaces for transmission and which are commonly discussed in MIMO context. Beside a better theoretical understanding this opens a window for future work with the goal to increase the bandwidth efficiency of OFDM-MFSK while keeping its robustness with respect to fast time-varying wireless channels. Index Terms ?? noncoherent transmission, subspace based communication, OFDM-MFSK, fast fading. View full abstract»

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  • Channel Estimation for large Cooperation Clusters

    Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1910 KB)  

    A novel very advanced interference mitigation framework (IFM-A) for celluar mobile radio systems has been developed, including several means like enlarged and overlapping cooperation areas performing a joint precoding over e.g. 3 sites. Assuming 3 sectors per site and 4 Tx-antennas per sector cooperation areas will comprise 36 antenna ports (AP). IMF-A promises for cellular mobile radio systems and under ideal conditions large spectral efficencies of 6 or even more bit/s/Hz. The details can be found in the ARTIST4G delverable D1.4 [1]. For realistic channel estimation the user equipments (UE) will have to estimate few to more than 20 relevant channel components with high accuracy. The quality of the estimated channel state information (CSI) is very important as it defines how much of the performance gains of the IMF-A framework can be maintained in reality. Here we propose a suitable channel estimation concept for the IMF-A framework having a small to moderate overhead for reference signals of about 5 to 10%. It allows an accurate estimation of weak channel components (CC), being typically neglected in less advanced interference mitigation schemes. Index terms ?? channel estimation, JP CoMP, reference signals. View full abstract»

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  • Efficiency Enhancement of RF-Pilot-Based Phase Noise Compensation for Coherent Optical OFDM Systems

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (415 KB)  

    Phase noise effects must be taken into account when studying the performance of coherent optical orthogonal frequency division multiplexing (CO-OFDM) transmission systems. One drawback of CO-OFDM is the high sensitivity to phase noise. In this paper, we explain different kinds of phase noise effects on the OFDM signals and analyze the phase noise effect induced by transmitter laser and receiver local oscillator. We review the pilot-aided and the standard RF-pilot (RFP) based phase noise compensation methods and explain its drawbacks. We provide two extended RFP schemes that overcome the drawbacks of the standard RFP scheme and enhance the performance of CO-OFDM systems. A simulation results of a CO-OFDM transmission system with 4-QAM is simulated. Furthermore, the phase noise effects for various laser linewidths on the system performance is presented. Index terms ?? CO-OFDM, phase noise, phase estimation, quadrature ampltiude modulation (QAM). View full abstract»

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  • Limited Feedback for MISO-OFDM Systems

    Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (106 KB)  

    A multiple input single output orthogonal frequency division multiplexing (MISO-OFDM) system with feedback-based transmit beamforming is investigated. Since existing algorithms do not take frequency and temporal correlation of the channel transfer function into account simultaneously, we propose to use a resource block (RB)-based feedback structure which utilizes both types of correlation on a RB basis. This method spends a few more bits on the first OFDM symbol in a RB and dramatically reduces the overall feedback overhead by exploiting temporal and frequency correlation. The RB-based algorithm is also shown to be able to restrain the SNR loss due to quantization of the optimal beamformer. Index Terms ?? Limited feedback, MISO-OFDM, transmit beamforming, RB-based encoding. View full abstract»

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  • Power and Subcarrier Allocation Scheme for Uplink OFDMA

    Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (129 KB)  

    In this contribution, we propose a power and subcarrier allocation scheme for uplink orthogonal frequency division multiple access (OFDMA) based on the capacity difference between different users. The scheme works iteratively and performs three major tasks. In the first step, the subcarrier with largest capacity difference of two active users is found. Then, the subcarrier selection of these two users is altered, with subsequent power allocation over their active carriers. During the last step, the subcarrier of the user which maximizes the sum-rate is kept active. As one user is deselected per subcarrier during each iteration, the algorithm will stop after M·(K–1) iterations. Furthermore, we will compare our scheme with some known schemes from the literature. View full abstract»

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  • Multicarrier systems: a comparison between Filter Bank based and Cyclic Prefix based OFDM

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (325 KB)  

    In this contribution we perform a review of some recent developments and important results on Filter Bank based Multicarrier (FBMC) systems and make a comparison with Cyclic Prefix (CP) based OFDM. We first give an overview of the system structure and show how the subcarriers are generated. Then the spectral and peakto- average power ratio (PAPR) behaviors are summarized. We review the subcarrier model used in the derivation of the per-subcarrier channel equalizers encountered in the recent literature and present a novel method of persubcarrier channel estimation based on this same model. We finally compare the performance of both FBMC and CP-OFDM by showing some BER simulation results, where both systems occupy the same bandwidth and provide the same throughput. Even with channel estimation we can see that FBMC still achieves more than 1 dB of advantage in Eb/N0 compared to CP-OFDM with a reasonable training sequence length. Index Terms ?? Multicarrier Systems, Filter Banks, OFDM, Filter Bank based Multicarrier. View full abstract»

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  • Experimental Investigation of Bit and Power Loading in 10 Gbit/s Next Generation Optical OFDM Access Networks

    Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (467 KB)  

    Orthogonal frequency division multiplexing (OFDM) based passive optical networks (PON) is a possible candidate for next generation optical access (NGOA) where due to cost constraints most likely intensity modulation (IM) and direct detection (DD) will be used. In combination with the dispersive optical channel it will result in a frequency selective system if double sideband (DSB) instead of the commonly employed single sideband (SSB) modulation is used. We will show experimentally that using bit loading (BL) and power loading (PL) can obviate the need for an optical single sideband filter (SSBF) therefore reducing the hardware expense in the cost sensitive access network. Index terms ?? OFDM, bit loading, power loading, EVM, DMT, SSB, DSB, PON. View full abstract»

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  • 10 Gbps 8??8 MIMO-OFDM Broadband Experimental System for 11 GHz Band Super High Bit-Rate Mobile Communications

    Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (351 KB)  

    Super high bit-rate mobile communications have been investigated to achieve more than 10 Gbps bitrate, and 5 Gbps 4 ?? 4 MIMO-OFDM experimental system has been developed. This paper presents a 10 Gbps 8 ?? 8 MIMO-OFDM experimental system that consists of baseband (BB) circuits supporting 400 MHz bandwidth and 11 GHz band radio frequency (RF) circuits. The BB circuits employ newly developed 800 MHz-sampling ADC circuits, and a BB calibration method compensates for different phases of clock signals provided into ADCs by using an interpolation filter. In addition, the RF circuits are expanded to eight channels, and a RF calibration method copes with IQ imbalance. Transmission performances are evaluated by the 10 Gbps 8 ?? 8 MIMO-OFDM experimental system employing turbo detection. It is shown that SNR degradation of the experimental results can be limited to 0.4 dB compared to the simulation results, and that the experimental system can achieve 10 Gbps throughput at SNR = 15.9 dB by three iterations of the turbo detection. Index Terms ?? Mobile communication, super high bit-rate, MIMO-OFDM, experiment, calibration, turbo detection. View full abstract»

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  • Improved Interference Alignment Performance for MIMO OFDM Systems by Multimode MIMO Antennas

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (673 KB)  

    This contribution presents an improved Interference Alignment (IA) method for arbitrary MIMOOFDM communication systems by exploiting spatial degrees of freedom of sophisticated multimode MIMO antennas. It is widely known that IA needs sufficient orthogonality between all the multi-user channels which is in typical indoor environments often not given due to insufficient spatial diversity. A significant improvement of the IA system performance has been achieved by using multimode MIMO antennas instead of classical and idealized omni-directional antennas. Such multimode MIMO antennas are capable to switch between different modes of the radiation patterns which significantly reduces the relevant channel coherence. Simulations of an indoor multi-user environment are carried out by a deterministic MIMO-OFDM channel model based on hybrid Electro Magnetic (EM) ray-tracing for being as close as possible to reality. Moreover, hardware implementation aspects are discussed as well demonstrating the feasibility of the overall IA based MIMO OFDM system. Index Terms ?? OFDM, Interference Alignment, MIMO, Multimode Antennas, Ray-tracing, Deterministic Channels. View full abstract»

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  • Experimental PDM-OFDM Signal Transmission with Shaped Signal Constellations Achieving a Net Spectral Efficiency of 11.15 b/s/Hz over a Distance of

    Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3261 KB)  

    In this contribution we present a coded coherent optical orthogonal frequency-division multiplex (COOFDM) transmission scheme with reduced guard interval (RGI) and our latest results on achieving highest information spectral densities. In our scheme, a RGI is used to accommodate the intersymbol interference (ISI) with short memory, such as induced by transmitter bandwidth limitations or fiber polarization mode dispersion(PMD), while fiber chromatic dispersion (CD) with long memory and well-defined characteristics is mostly compensated within the receiver by a discrete Fourier transform (DFT)-based electronic dispersion compensation (EDC). We apply strong forward error correction (FEC) coding as an enhancement of bit interleaved coded modulation with iterative decoding (BICM-ID) by using low-density parity-check (LDPC) codes and shaped signal constellations (256-iterative polar modulation (IPM)) on the subcarriers of the OFDM system. We then present our latest experimental results on the generation and FEC-decoding of a polarization-division multiplexed (PDM)- OFDM signal with a net channel data rate of 231.5 Gb/s, occupying a bandwidth of 20.75 GHz. In an experiment on the performance of the developed system, transmission was performed over 800 km of ultra-large-area fiber (ULAF), achieving an intrachannel spectral efficiency (ISE) of 11.15 b/s/Hz with a coding gain of 15.1 dB compared to uncoded 256-QAM at a post-FEC BER of 10-15. Index Terms ?? Coded Optical Orthogonal Frequency- Division Multiplexing (CO-OFDM), Bit Interleaved Coded Modulation with Iterative Decoding (BICM-ID), Iterative- Polar-Modulation (IPM), Polarization-Division Multiplexing (PDM). View full abstract»

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  • Ultra High Speed Digital Down Converter Design for Virtex-6 FPGAs

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (417 KB)  

    This paper describes the design and optimization of an ultra- high speed Digital Down Converter (DDC) for a realization by FPGAs. After explaining the general structure of the Digital Down converter we describe in detail how to implement such a design in order to process a digital, massively parallelized signal. The necessary optimizations to achieve an efficient implementation in state of the art FPGAs are explained and a case study for an FPGA optimized Digital Down Converter design suitable for OFDMA systems is presented. The key components of this DDC are highly parallelized half-band filters which are optimized for Virtex- 6 FPGAs and enable the design to decimate a 6 bit wide input signal with a sample rate of 25 GS/s into a 16 bit 1.5625 GS/s signal while achieving an attenuation of around 35 dB. The results include the resource consumption of the DDC for a Virtex-6 XC6VHX380T FPGA as well as the filter response to a chirp test signal. Index Terms ?? FPGA; DDC; OFDMA; FIR; Decimator. View full abstract»

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  • CoMP in Heterogeneous Networks: Low-Complexity Joint Cooperative Resource Allocation with SDMA

    Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (242 KB)  

    Coordinated multipoint transmission (CoMP) is considered for a heterogeneous network where different kinds of base stations (BS) are located. We focus on joint cooperative resource allocation including linear transceiver design and user scheduling with the goal of maximizing the weighted sum rate in the downlink of a multipleinput multiple-output orthogonal frequency division multiple access (MIMO-OFDMA) system, where each frequency resource can be allocated to multiple users at a given time instance, i.e., space division multiple access (SDMA) is enabled. Furthermore, we consider the case where multiple streams are allocated per user. Since the optimal solutions are extremely computationally complex to obtain, we introduce some scheduling metrics for selecting the most suitable subsets of users on each subchannel and propose a suboptimal joint resource allocation algorithm using these metrics. The proposed algorithm is able to take linear per-BS power constraints into account, and simulation results indicate that using the proposed algorithm achieves near-optimal solutions regardless of the scheduling metric chosen. Index Terms ?? Weighted sum rate maximization, linear transceiver design, user scheduling, signal-to-leakege-noise ratio. View full abstract»

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  • CoMP in Heterogeneous Networks: Linear Transceiver Design Using the Minimum Weighted Arithmetic-MSE Criterion

    Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (175 KB)  

    Coordinated multipoint transmission (CoMP) is considered for a heterogeneous network (HetNet) where different kinds of base stations (BS) are located. We focus on linear transceiver design with the goal of maximizing the weighted sum-rate in the downlink of a multipleinput multiple-output orthogonal frequency division multiple access (MIMO-OFDMA) system, where each subchannel is allocated to a single user (termed as single-user MIMOOFDMA). We address this in the context of minimizing the weighted arithmetic mean of the mean-square-errors (MSEs), i.e., weighted arithmetic-MSE minimization. The problem is shown to be non-convex for a given rank constraint on the number of streams at a subchannel. Therefore, the solutions to the rank-constrained problem are suboptimal in general. We show that iterative approaches provide more efficient suboptimal solutions compared to the rank-relaxed approach, especially in a heterogeneous network where highly imbalanced base stations are located. Index Terms ?? Weighted sum-rate maximization, linear transceiver design, second-order cone programming, semidefinite programming. View full abstract»

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  • Implementation of a Real-Time Adaptive Modulation OFDM Transceiver System

    Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (91 KB)  

    The performance analysis of new transmission schemes in wireless communication is usually based on simulations and many new methods do not run on real systems because of the limited real-time performance. In this paper the implementation of an adaptively modulated orthogonal frequency division multiplexing (OFDM) transceiver for realtime applications is presented. Especially the calculation time for the bit allocation table (BAT) must fulfill critical time requirements. It is shown that all processing steps can be carried out by personal computers with an Intel Core i7 CPU 920 for a radio signal bandwidth of 12.5 MHz. Index Terms ?? OFDM testbed, adaptive modulation, realtime. View full abstract»

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