Exact Analysis for Downlink MC-CDMA in Rayleigh Fading Channels

Hou, Zhihua; Dubey, V.K.

doi:10.1109/lcomm.2004.823394

Cited by 20 publications

(13 citation statements)

References 4 publications

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“…Such kind of TDL models were originally introduced by Kailath [17] and Bello [1] as canonical channel models -which essentially are channel SMs -for band-limited time-variant linear (TVL) systems. SSTDL models are nowadays widely in use for evaluating the performance of modern wireless communication systems, e.g., [18]- [20].…”

Section: Several Sms Basing On the Time-variant Tapped-delay-line (Tdmentioning

confidence: 99%

“…Most of the literature on this topic concentrates only on describing the structure of the SSTDL model [6], [7], and even though a statistical analysis can be found in [1], [4] and [16], no information concerning the channel frequency correlation function (FCF) is provided there. The information about the FCF is very important because this function influences the performance of many wide-band and frequency diversity wireless communication systems, such as multicarrier code division multiple access (MC-CDMA) systems [18]- [20], [22], [23].…”

Section: Several Sms Basing On the Time-variant Tapped-delay-line (Tdmentioning

confidence: 99%

“…Despite the SSTDL model proves to be incompatible with WSSUS channels from the perspective of band-limited systems, SMs of this kind are widely being used in connection with the WSSUS model to evaluate the performance of up-to-date wireless communication systems, e.g., [18]- [20]. In defense of such a system performance investigation approach, we can argue that the SSTDL model might coexist with WSSUS channels if the bandwidth constraint imposed on the CIR h(t, τ ) is relaxed 5 .…”

Section: Statistical Behavior Of Sstdl Modelsmentioning

confidence: 99%

“…When we use a T -spaced TDL model (or a ∆τ -spaced TDL model in general) for simulating the system described by (20), then the channel matrix C is equivalent toĈ = diag{Ĥ}, where Ĥ = fft{ĥ} τ →∆f , andĥ ∈ C M ×1 with M ≥ N is the vector representation 7 ofĥ(τ ; t). The notation fft{·} τ →∆f indicates the column-wise fast Fourier transform (FFT) of a matrix with respect to ∆f .…”

Section: The Influence Of the Fcf On The System Performancementioning

confidence: 99%

“…From (25), and since the eigenvalues of R andR are not exactly the same because of (23) and (24), the BEP of the reference system described by (20) will differ from that of the simulation system described byŶ =ĈX + N, whereĈ = diag{Ĥ}. (25), which is given by…”

Section: The Influence Of the Fcf On The System Performancementioning

confidence: 99%

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On the problems of symbol‐spaced tapped‐delay‐line models for WSSUS channels

Guti

Cabrera-Bean

Pätzold

2008

Wireless Communications

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This paper analyzes the pertinence and statistical behavior of symbol-spaced tappeddelay-line (SSTDL) models for wide-sense stationary uncorrelated scattering (WSSUS) mobile radio channels. SSTDL models are obtained by sampling the channel impulse response (CIR) in delay domain at a rate equal to the reciprocal of the symbol duration. They were proposed more than four decades ago as canonical channel models for band-limited time-variant linear systems, and are nowadays widely in use for assessing the performance of several wireless communication systems. The applicability of these tapped-delay-line (TDL) models seems to be unquestionable, as they were developed in the framework of the sampling theorem. Nonetheless, we show here that SSTDL models should be used with care to model WSSUS channels, because the channel's uncorrelated scattering (US) condition might easily be violated. Furthermore, we show that SSTDL models suffer from strong limitations in emulating the channel frequency correlation function (FCF). This drawback leads to an inaccurate performance evaluation of wireless communication systems sensitive to the FCF. To cope with this problem, we present a simple solution by doubling the channel's sampling rate. The benefits of this solution are demonstrated with some exemplary simulation results.

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Section: Several Sms Basing On the Time-variant Tapped-delay-line (Tdmentioning

confidence: 99%

Section: Several Sms Basing On the Time-variant Tapped-delay-line (Tdmentioning

confidence: 99%

Section: Statistical Behavior Of Sstdl Modelsmentioning

confidence: 99%

Section: The Influence Of the Fcf On The System Performancementioning

confidence: 99%

Section: The Influence Of the Fcf On The System Performancementioning

confidence: 99%

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On the problems of symbol‐spaced tapped‐delay‐line models for WSSUS channels

Guti

Cabrera-Bean

Pätzold

2008

Wireless Communications

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Pre‐filtering technique for MAI cancellation in MC‐CDMA systems

Chang¹,

Yen²,

Yang³

et al. 2011

Wireless Communications

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Multicarrier code division multiple access (MC-CDMA), is a promising multiplexing technique for future communication systems. In this study, we employ the well-known Walsh-Hadamard spreading codes for synchronous downlink transmission of MC-CDMA systems. The spreading codes allow that the frequency diversity to be efficiently exploited. However, multipath propagation may cause orthogonality among users is distorted, and this distortion produces multiple access interference (MAI). To eliminate this effect, we propose a pre-filtering-based MC-CDMA system which uses a pre-filtering technique at the transmitter and an equal gain combining (EGC) scheme at the receivers, respectively. Our proposed prefiltering technique transforms the transmitted signals so that the MAI can be eliminated, and the EGC scheme weights the signals received from all subcarriers so that channel distortions can be compensated. Furthermore, the proposed technique can calculate the transmitted power over all subcarriers to satisfy the required quality of service of each user and archive MAI-free. In this paper, performance in terms of bit error rate is analyzed; in comparison with the EGC, orthogonal restoring combining, and maximal ratio combining schemes at receiver, respectively.Recently, the demand for wireless communication services has expanded to encompass new applications. Now, wireless communication service includes not only traditional services, such as e-mail, ftp, and web applications, but also multimedia services, such as audio, video, and images. Therefore, the ability to provide users with a high data transmission rate is becoming increasingly important in wireless communication systems. The multicarrier code division multiple access (MC-CDMA), also known as OFDM-CDMA [1,2], is an attractive technique for achieving high data rate wireless data transmission in frequency-selective fading channels. While transferring data, the MC-CDMA system splits a high-rate data stream into several lowrate data streams, and duplicates each of these low-rate streams into multi-copies; each of these low-rate streams are multiplied by a specific spreading code. Because a transmission signal is spread in a frequency domain, the MC-CDMA system can efficiently make use of frequency diversity techniques to improve the system performance. The techniques have been shown to counteract the effect of multipath propagation. Several researchers have studied the exact performance of the bit error rate (BER) of MC-CDMA systems over a multipath channel [3--5]. Generally, MC-CDMA signals transmitted over a fading channel will be influenced by delay spread which leads to multiple access interference (MAI) for which the orthogonality of the spreading code among users is distorted [6].MAI is the major interference that limits the performance of CDMA-based systems [3--5]. To mitigate MAI, signal detection techniques for MC-CDMA systems are discussed and compared in Ref. [1]. Several researchers have studied multiuser detection (MUD) techniques [1,7--10] for MC-CDMA sy...

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