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Wireless Communication Systems (ISWCS), 2010 7th International Symposium on

Date 19-22 Sept. 2010

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  • Broadband underwater source localization by solving basis pursuit de-noising using coordinate descent search

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (226 KB) |  | HTML iconHTML  

    Underwater localization of multiple acoustic sources is important for underwater communication networks. As the number of sources is much smaller than the number of potential source positions, sparse signal representation can be adopted. In this paper, we propose a new sparsity based matched field (MF) processing method to solve the underwater source localization problem. The proposed method is based on solving the basis pursuit de-noising (BPDN) problem for multi-frequency signals. An efficient algorithm based on homotopy approach and coordinate descent optimization is used to find the BPDN solution. The performance is evaluated by applying this technique to real data obtained in the underwater acoustic experiment SWellEx-96. It is shown that this method can accurately locate multiple sources. It outperforms other MF approaches in resolving sources positioned very closely to each other, tolerance to noise and capability of locating multiple sources. View full abstract»

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  • EXIT chart analysis of BICM-ID based receiver for shallow underwater acoustic communications

    Page(s): 6 - 10
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (309 KB) |  | HTML iconHTML  

    We present extrinsic information transfer (EXIT) chart analysis of iterative equalizer implemented using adaptive decision feedback equalizers (DFE) and bit-interleaved coded modulation with iterative decoding (BICM-ID) to analyse the performance. It is shown from the EXIT chart analysis that the performance of the BICM-ID based receiver strongly depends on the ability of the equalizer to remove the intersymbol interference (ISI) and the number of taps employed in the feedback filter of the DFE. It is demonstrated that error free communication can be achieved even though the DFE does not cover the entire span of the channel, which is typically the case for underwater communications (UWC). Furthermore, it is shown that the latency associated with the iterative processing can be avoided if the initial equalization is successful, leading the receiver to iterate for less iterations. View full abstract»

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  • Multi-carrier modulation for high-rate underwater acoustic communications

    Page(s): 11 - 15
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1369 KB) |  | HTML iconHTML  

    The current state-of-the-art in high-rate acoustic communications is represented by adaptive multi-channel equalization of single-carrier wideband signals, which is used in real-time acoustic modems and as a benchmark for coherent communications performance. An alternative technique with significant potential for achieving high bit rates over multipath-distorted (frequency selective) channels is multi-carrier modulation (MCM). MCM has many technical advantages for acoustic communications including an increased tolerance of time synchronization errors made possible by the use of a set of narrow-band channels. In addition, each frequency channel can be transmitted using relatively narrow-band high efficient transducer and low-power amplifier. Each of MCM frequency channels can have relatively low delay spread when measured in units of the baud period and can be equalized with low-complexity algorithms and simplified array processing. The reduction of the inter-symbol interference (ISI) ISI span in each sub-channel allows for the application of sophisticated soft decision decoders, such as maximum-likelihood sequence detectors (MLSD) and adaptive BCJR MAP algorithm. These algorithms are optimal for joint channel estimation and data recovery and are the principal part of the proposed MCM system and their properties are the general objective of the paper. The adaptive form of MAP algorithm has been considered. More practical MLSD algorithm with dual loop feedback and pre-survivor (PSP) processing was tested in SPACE08 and RACE08 shallow water acoustic communications experiments and yielded excellent results. View full abstract»

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  • A quantitative assessment of the compatibility of Ultra Wideband with radiolocation services

    Page(s): 16 - 20
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2062 KB) |  | HTML iconHTML  

    In this coexistence study, the effect of an Ultra Wideband (UWB) MB-OFDM signal, as defined in the ECMA-368 standard, on an S-band radar device working in the 3.1 GHz to 3.4 GHz range is investigated. An extensive series of 6460 measurements, done with 20 different radar waveforms and for various radar and UWB signal levels is analyzed, using a laboratory test bed specifically designed for this purpose. The interfered radar signal is acquired by a spectrum analyzer and then processed on a stand-alone PC. Different post-processing techniques are applied, depending on the type of the selected radar receiver structure. View full abstract»

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  • Experimental evaluation of avoid performance with various victim systems to enable DAA for UWB

    Page(s): 21 - 25
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (549 KB) |  | HTML iconHTML  

    In most Asian and European countries, detect-and-avoid (DAA) is required at UWB low band (3.1-4.8 GHz). In Japan, we conducted evaluation experiments on the performance of DAA until March of 2010, which was a part of a three-year campaign to provide results of literature review and technical evaluation for the purpose of accomplishing Japanese UWB regulation. In this paper, experiment results on the avoid performance are presented. Three types of victim systems, 3GPP LTE, Mobile WiMAX, and an experimental IMT Advanced Test-bed, were used in the experiments. The UWB system was built based on WiMedia specifications at the UWB low band. A notch was created in the UWB spectrum where a victim signal was going to appear. The notch was created by nullifying the related subcarriers in combination with the use of a filter or applying a window function. The interference effects of UWB to victim systems were evaluated by examining the bit error rate (BER) or packet error rate (PER) performance. Our results show that when the width and depth of the notch satisfy certain conditions, the interference level introduced by UWB can be below the permitted level in regulations. View full abstract»

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  • Implementation of a wireless test bed for the functional verification of the ultra-wideband Detect-and-Avoid mechanism

    Page(s): 26 - 30
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (262 KB) |  | HTML iconHTML  

    Detect-and-Avoid (DAA) is a mechanism to be employed in Ultra Wideband (UWB) systems that enables them to coexist with other, typically licensed radio services in the same part of the radio spectrum. To protect these licensed services from interference, regulatory authorities defined detailed DAA models and parameters. For chip and equipment manufacturers, the ability to verify the compliance of their UWB products with regulatory and standards requirements through measurements will be essential. Owing to the novelty of the DAA mechanism, the nature of the devices to be tested, and the very low power levels to be detected, such RF compliance tests constitute a major challenge. In this paper we describe a setup and procedure for UWB DAA test and measurement that was developed in the frame of FP7 project WALTER; furthermore we highlight a number of difficulties encountered in this process due to physical constraints, and provide solution proposals. Although WALTER focused on the MB-OFDM variant of UWB, as defined by the Wimedia Alliance, its findings and conclusions are not limited to this particular UWB technology. View full abstract»

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  • Introduction of MAP estimation to UWB-IR TOA localization

    Page(s): 31 - 35
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (189 KB) |  | HTML iconHTML  

    This paper proposes a new method based on the combination of a soft-decision ranging and Maximum A Posteriori (MAP) estimation for Impulse Radio type Ultra Wide Band (UWB-IR) Time of Arrival (TOA) localization. The soft-decision ranging assigns the probability of being generated by a signal to each component in the observed instantaneous power delay profile (the probability density function (pdf) of the first arrival signal) and the MAP estimation calculates the location of a target node which maximizes the product of the pdfs obtained for different anchor nodes. Computer simulation results show that, as compared with a conventional localization method, the proposed method is advantageous in typical mixed Line-Of-Sight (LOS)/Non Line-Of-Sight (NLOS) indoor environments. View full abstract»

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  • System implementation study on RSSI based positioning in UWB networks

    Page(s): 36 - 40
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1017 KB) |  | HTML iconHTML  

    The Ultra-Wideband Radio Technology (UWB-RT) enables accurate Location and Tracking (LT) applications. However, the required and sophisticated time of arrival (ToA) ranging procedure relies on accurate synchronizations and time measurements. Non-cooperative nodes, not supporting the ToA feature, cannot be localized with this LT approach. Other LT approaches exploit the received signal strength (RSS) or received signal strength difference (RSSD). Simulations of RSS based localization in UWB networks showed promising performance results. In this paper, the authors introduce a RSS based LT demonstrator, build up with conventional Certified Wireless USB (CWUSB) sticks, using multiband UWB-RT. Different LT algorithms are tested. In a small UWB network, measurements of the localization accuracy show a root mean square error (RMSE) of about 0.33 meters. View full abstract»

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  • Evaluation on detection capability of down-link signals of mobile WiMAX and 3GPP LTE for detect-and-avoid in UWB systems

    Page(s): 41 - 45
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (313 KB) |  | HTML iconHTML  

    The present article describes the experimental result of victim system detection by UWB wireless system to contribute for Japanese UWB regulatory discussion, in which a mitigation, including detect-and-avoid (DAA), technology implementation in the frequency range of 3.4 to 4.8 GHz is a major technical topic. A FPGA based MB-OFDM UWB receiver with 528 MHz sampling rate and 128 points FFT capability was prepared for this purpose and mobile WiMAX and 3GPP LTE were selected as victim systems to be detected. Various baseband victim signals generated by a vector signal generator were detected at various detect conditions and signal-to-noise ratios and time to detection was measured. In this experiment, 99% probability detection was achieved within 2.4 seconds. View full abstract»

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  • Resource saving approach on Logical Link Control and Device Management Entity Layer for ECMA-368 based devices

    Page(s): 46 - 50
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB) |  | HTML iconHTML  

    This specification defines a sophisticated Logical Link Control Protocol for the WiMedia radio platform based on the standard ECMA 368 [1] and the draft WiMedia Logical Link Control Protocol Specification: Draft 1.08.4 [2]. Our proposal for the Logical Link Control, referred to as WLP - (W)ireless (L)ogical Link Control (P)rotocol, allows a very easy and smooth implementation for an IEEE 802.2 and ECMA 368 to IPv6 connectivity. In contrast to [1] and [2] there are a lot of improvements like a more efficient association and disassociation procedure and simplified information structures. Furthermore a fundamental new specification for a Device Management Entity (DME) (announced in [1] but not specified there) will be introduced, which provides several management and maintenance functions to connect WLP, the Medium Access Control (MAC) and the Application. View full abstract»

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  • Efficient subcarrier allocation in downlink multiuser MIMO-OFDM systems

    Page(s): 51 - 55
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (601 KB) |  | HTML iconHTML  

    This paper proposes a unit power based subcarrier allocation algorithm with the aim of minimizing the total transmit power in the downlink multiuser MIMO-OFDM systems, and compares its performance and complexity with Zhang's algorithm and extended Correlation-based algorithm (ECBA). By applying Singular Value Decomposition (SVD), the inter-antenna interference (IAI) and multiple user interference (MUI) can be minimized. Our proposal is combined with the single user optimal bit allocation (OBA) algorithm to achieve the aim. We verify the proposal by simulation of the performance of total transmit power and calculating the computation complexity. The simulation results show our modification has significant improvement compared with Zhang's algorithm and the ECBA. View full abstract»

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  • Performance of multiuser MIMO-OFDM precoding techniques with quantized channel information

    Page(s): 56 - 60
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (145 KB) |  | HTML iconHTML  

    It is well known that precoding techniques in multiuser multiple-input multiple-output (MU-MIMO) communication systems improve the whole data throughput since they allow for spatial multiplexing of different users. However, these techniques require a precise knowledge of the channel information at the transmitter. In most of the current systems, transmitter can not estimate the channel so feedback information has to be provided by the receiver. In this paper, we propose a new limited feedback approach where Vector Quantization (VQ) is applied over the channel frequency response. Different configurations of feedback bits per subcarrier in a multiuser MIMO-OFDM system have been simulated. Additionally, different precoding schemes based on the estimated channel information have been tested and BER performance has been evaluated. Results show that, for a similar cost of feedback information (bits/subcarrier), better channel estimates are achieved using longer vectors in the VQ codebook, whereas optimal non-linear precoding schemes perform well even for large channel estimation errors. View full abstract»

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  • Sub-band pre-channel compensation-at RS for MC-CDMA downlink relay system

    Page(s): 61 - 65
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB) |  | HTML iconHTML  

    In this paper, we consider a relay system for a downlink communication of multi carrier code division multiple access (MC-CDMA) to improve the performance of cell-edge. However since different signals from the base station and the relay station affect different frequency-selective fading channels, the use of frequency-domain equalization at a receiver cannot restore the orthogonality of these signals. Therefore, bit error rate (BER) performance severely degrades due to large multiaccess interference (MAI). We have proposed a channel compensation method at the relay station for MC-CDMA to improve the performance of the downlink relay system. In this method, the channel response from the relay station to the terminal is compensated to be the same channel response from the base station to the terminal at the receiver terminal. Therefore, MAI can be reduced and BER performance is improved. However, the compensation causes the problem of reducing the effect of frequency domain diversity gain by using relay station. Therefore, in this paper, we also propose a sub-band pre-channel compensation at the relay station for MC-CDMA downlink relay system to obtain the diversity gain. View full abstract»

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  • Switched interleaving techniques with limited feedback for interference mitigation in Uplink Multi-antenna MC-CDMA Systems

    Page(s): 66 - 70
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (182 KB) |  | HTML iconHTML  

    In this work a novel switched-interleaving algorithm based on limited feedback is proposed to suppress interference for uplink multi-carrier code-division multiple-access (MC-CDMA) multiple antenna systems. A codebook of chip-interleavers is constructed and prestored at both the base station (BS) and mobile stations (MSs). The transmit chip-interleaver is chosen by the BS from the codebook, and the index of the interleaver is fed back using a limited number of bits. The optimum interleaving pattern is chosen by the selection function of the sum received signal to interference plus noise ratio (SINR). We describe three methods to design the codebook of interleavers. Simulation results show that the performance of the proposed techniques is significantly better than prior art. View full abstract»

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