The Experts below are selected from a list of 14352 Experts worldwide ranked by ideXlab platform

C R Nassar - One of the best experts on this subject based on the ideXlab platform.

  • high throughput high performance ofdm via pseudo Orthogonal Carrier interferometry spreading codes
    IEEE Transactions on Communications, 2003
    Co-Authors: D A Wiegandt, C R Nassar
    Abstract:

    The paper introduces to Orthogonal frequency-division multiplexing (OFDM) systems a novel pseudo-Orthogonal Carrier interferometry spreading code which spreads each parallel data stream over all the OFDM Carriers. Pseudo-Orthogonal Carrier interferometry (PO-CI) spreading codes are carefully selected to introduce the following benefits to OFDM: up to 2N parallel data streams can be coded onto N Carriers, with little degradation in performance; when rate 1/2 channel coding is applied in addition to PO-CI spreading codes, the resulting binary phase-shift keying OFDM systems demonstrate the performance of coded OFDM and the throughput of uncoded OFDM; PO-CI codes are carefully selected to spread in a manner which eliminates the peak-to-average power ratio problems characteristic of traditional OFDM.

  • high throughput high performance ofdm via pseudo Orthogonal Carrier interferometry coding
    Personal Indoor and Mobile Radio Communications, 2001
    Co-Authors: D A Wiegandt, C R Nassar
    Abstract:

    OFDM (Orthogonal frequency division multiplexing) is susceptible to poor probability of error performance in fading channels. To enhance OFDM's performance, many architectures utilize channel coding. The addition of coding, adds both redundancy and frequency diversity, but comes at a cost of reduced overall throughput (typically by a factor of 2). This paper introduces a novel Carrier interferometry phase coding to enhance the performance in OFDM systems without bandwidth expansion or decreased throughput. It is shown that at a bit error rate of 10/sup 3/, this method gains 14 dB over OFDM, equaling the performance of COFDM. A system is now available demonstrating the benefits of coded OFDM, which maintains the throughput of OFDM. The cost is one of increased receiver complexity.

D A Wiegandt - One of the best experts on this subject based on the ideXlab platform.

  • high throughput high performance ofdm via pseudo Orthogonal Carrier interferometry spreading codes
    IEEE Transactions on Communications, 2003
    Co-Authors: D A Wiegandt, C R Nassar
    Abstract:

    The paper introduces to Orthogonal frequency-division multiplexing (OFDM) systems a novel pseudo-Orthogonal Carrier interferometry spreading code which spreads each parallel data stream over all the OFDM Carriers. Pseudo-Orthogonal Carrier interferometry (PO-CI) spreading codes are carefully selected to introduce the following benefits to OFDM: up to 2N parallel data streams can be coded onto N Carriers, with little degradation in performance; when rate 1/2 channel coding is applied in addition to PO-CI spreading codes, the resulting binary phase-shift keying OFDM systems demonstrate the performance of coded OFDM and the throughput of uncoded OFDM; PO-CI codes are carefully selected to spread in a manner which eliminates the peak-to-average power ratio problems characteristic of traditional OFDM.

  • high throughput high performance ofdm via pseudo Orthogonal Carrier interferometry coding
    Personal Indoor and Mobile Radio Communications, 2001
    Co-Authors: D A Wiegandt, C R Nassar
    Abstract:

    OFDM (Orthogonal frequency division multiplexing) is susceptible to poor probability of error performance in fading channels. To enhance OFDM's performance, many architectures utilize channel coding. The addition of coding, adds both redundancy and frequency diversity, but comes at a cost of reduced overall throughput (typically by a factor of 2). This paper introduces a novel Carrier interferometry phase coding to enhance the performance in OFDM systems without bandwidth expansion or decreased throughput. It is shown that at a bit error rate of 10/sup 3/, this method gains 14 dB over OFDM, equaling the performance of COFDM. A system is now available demonstrating the benefits of coded OFDM, which maintains the throughput of OFDM. The cost is one of increased receiver complexity.

Bin Wang - One of the best experts on this subject based on the ideXlab platform.

  • spreading code design of adaptive non contiguous sofdm for dynamic spectrum access
    IEEE Journal of Selected Topics in Signal Processing, 2011
    Co-Authors: Vasu Chakravarthy, Bin Wang
    Abstract:

    In a dynamic spectrum access (DSA) network, multi-Carrier-based cognitive radio transceivers need to deactivate some of their subCarriers to avoid interference to primary users. In a mobile environment, the spread Orthogonal frequency-division multiplexing (SOFDM) system has demonstrated excellent performance in multipath fading channels, outperforming the traditional OFDM system due to the diversity gain. The traditional SOFDM uses Hadamard-Walsh code as the spreading code set, in which case, when deactivating subCarriers, Orthogonality among different spreading codes will be lost, leading to poor bit error ratio (BER) performance. The performance of the SOFDM system can be improved by using adaptive spreading code adjustment to compensate for the loss of Orthogonality. Because Hadamard-Walsh codes only exist for certain code length, in many cases, the SOFDM system based on Hadamard-Walsh code set needs to deactivate more subCarriers. Otherwise, loss of Orthogonality cannot be eliminated. Instead, it can only be minimized. Moreover, deactivating more subCarriers will force the system to reduce the data rate. By treating the system as subsystems, we can generate binary Orthogonal code set based on Hadamard-Walsh code to maintain the data rate. On the other hand, if the spreading code is not limited to be binary, Orthogonal Carrier interferometry (CI) codes exist for code length of any integer. Hence, by applying non-contiguous SOFDM (NC-SOFDM) with CI code to DSA, the loss of Orthogonality among spreading codes caused by deactivating subCarriers can be eliminated. In this paper, we propose two novel spread coding schemes for NC-SOFDM for cognitive radio in a DSA network. The new spreading code sets help the system to maintain the same data rate as that of the traditional OFDM and improve the performance by exploiting the diversity gain and eliminating the Orthogonality loss. The NC-SOFDM with the proposed spreading code outperforms the traditional NC-OFDM and the adaptive NC-SOFDM with Hadamard-Walsh code.

Vasu Chakravarthy - One of the best experts on this subject based on the ideXlab platform.

  • spreading code design of adaptive non contiguous sofdm for dynamic spectrum access
    IEEE Journal of Selected Topics in Signal Processing, 2011
    Co-Authors: Vasu Chakravarthy, Bin Wang
    Abstract:

    In a dynamic spectrum access (DSA) network, multi-Carrier-based cognitive radio transceivers need to deactivate some of their subCarriers to avoid interference to primary users. In a mobile environment, the spread Orthogonal frequency-division multiplexing (SOFDM) system has demonstrated excellent performance in multipath fading channels, outperforming the traditional OFDM system due to the diversity gain. The traditional SOFDM uses Hadamard-Walsh code as the spreading code set, in which case, when deactivating subCarriers, Orthogonality among different spreading codes will be lost, leading to poor bit error ratio (BER) performance. The performance of the SOFDM system can be improved by using adaptive spreading code adjustment to compensate for the loss of Orthogonality. Because Hadamard-Walsh codes only exist for certain code length, in many cases, the SOFDM system based on Hadamard-Walsh code set needs to deactivate more subCarriers. Otherwise, loss of Orthogonality cannot be eliminated. Instead, it can only be minimized. Moreover, deactivating more subCarriers will force the system to reduce the data rate. By treating the system as subsystems, we can generate binary Orthogonal code set based on Hadamard-Walsh code to maintain the data rate. On the other hand, if the spreading code is not limited to be binary, Orthogonal Carrier interferometry (CI) codes exist for code length of any integer. Hence, by applying non-contiguous SOFDM (NC-SOFDM) with CI code to DSA, the loss of Orthogonality among spreading codes caused by deactivating subCarriers can be eliminated. In this paper, we propose two novel spread coding schemes for NC-SOFDM for cognitive radio in a DSA network. The new spreading code sets help the system to maintain the same data rate as that of the traditional OFDM and improve the performance by exploiting the diversity gain and eliminating the Orthogonality loss. The NC-SOFDM with the proposed spreading code outperforms the traditional NC-OFDM and the adaptive NC-SOFDM with Hadamard-Walsh code.

Lang Hong - One of the best experts on this subject based on the ideXlab platform.

  • Performance Evaluation of Adaptive Non-contiguous MC-CDMA and Non-contiguous CI/MC-CDMA for Dynamic Spectrum Access
    2008 3rd International Conference on Cognitive Radio Oriented Wireless Networks and Communications (CrownCom 2008), 2008
    Co-Authors: Paul Ratazzi, Vasu D. Chakravarthy, Lang Hong
    Abstract:

    In this paper, we present a quantitative performance evaluation of non-contiguous multi-Carrier code vision multiple access (NC-MC-CDMA) for cognitive radio in a dynamic spectrum access (DSA) network. In a DSA network, multi-Carrier based cognitive radio transceivers need to deactivate some of its subCarriers to avoid interference to primary users. However, by deactivating subCarriers, Orthogonality among different spreading codes are lost, leading to poor BER performance. The performance of the NC-MC-CDMA can be improved by adaptive spreading code adjustment to compensate for the loss of Orthogonality. However, since Hadamard-Walsh codes only exist for certain code length, loss of Orthogonality can only be minimized instead of eliminated for many cases. On the other hand, Orthogonal Carrier Interferometry codes exist for code length of any integer. Hence, by applying non-contiguous CI/MC-CDMA into DSA, the loss of Orthogonality among spreading codes caused by deactivating subCarriers can be eliminated. As a direct result, adaptive NC-CI/MC-CDMA significantly outperforms adaptive NC-MC-CDMA using Hadamard-Walsh codes.