Errors-and-erasures' decoding performance of RS coded DS-CDMA using M-ary orthogonal signalling (original) (raw)
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Second IFIP International Conference on Wireless and Optical Communications Networks, 2005. WOCN 2005., 2005
The system under study is a convolutionally coded and orthogonally modulated DS-CDMA system in time-varying frequency selective Rayleigh fading channels. In this paper, we investigate several iterative schemes based on soft demodulation and decoding algorithms. The performance of different strategies are evaluated numerically and proved to achieve substantial performance gain compared to the conventional hard decision based scheme, especially when the soft demodulator is assisted by decision directed channel estimation and interference cancellation techniques, and also when demodulation and decoding are performed jointly in an iterative manner.
IEEE Transactions on Vehicular Technology, 1998
The probability of error performance of a directsequence code-division multiple-access (DS/CDMA) system employing noncoherent M-ary orthogonal signaling in a Nakagami multipath fading channel is analyzed. A RAKE receiver structure with square-law demodulation is used at the receiver. The multiple-access interferences are modeled as Gaussian and expressions derived for the exact probability of error. The performance is also evaluated in terms of the number of users that can be supported by the system at a given probability of error. The effect of correlated fading on system performance is also investigated by considering two correlation models, which can be characterized by a single correlation coefficient. In the first model, the correlation coefficient between any two diversity branches is constant. In the second model, it is assumed that the correlation coefficient between any two diversity branches decreases exponentially as the separation between them increases. For both models, it is found that the presence of correlation deteriorates system performance. The use of larger signal alphabets than binary modulation in conjunction with diversity reception provides a considerable performance improvement even in the presence of correlated fading. Index Terms-Correlated Nakagami fading, DS-CDMA system, M-ary noncoherent orthogonal modulation. I. INTRODUCTION T HE ABILITY of direct-sequence code-division multipleaccess (DS/CDMA) systems to mitigate the effect of multipath and suppress interference has made them popular in recent years. Especially, CDMA has been shown to offer more system capacity than time-division multiple access (TDMA) or frequency-division multiple access (FDMA) in cellular networks [1]. In a multiuser DS/CDMA system, a pilot signal must usually be included in the forward/reverse link for each user so that coherent demodulation can be performed at the receiver. Such is the case, for example, in the wideband CDMA system authorized as the air interface of IS-665, which uses coherent detection and interference cancellation techniques to improve system capacity [2]. However, the reverse link is more vulnerable to interference and, therefore, has less capacity than the forward link. Also, on the reverse channel it may be difficult to recover the pilot signal from Manuscript
IEEE Journal on Selected Areas in Communications, 2000
The performance of Reed-Solomon (RS) coded direct-sequence code division multiple-access (DS-CDMA) systems using noncoherent-ary orthogonal modulation is investigated over multipath Rayleigh fading channels. Diversity reception techniques with equal gain combining (EGC) or selection combining (SC) are invoked and the related performance is evaluated for both uncoded and coded DS-CDMA systems. "Errors-and-erasures" decoding is considered, where the erasures are based on Viterbi's so-called ratio threshold test (RTT). The probability density functions (PDF) of the ratio associated with the RTT conditioned on both the correct detection and erroneous detection of the-ary signals are derived. These PDFs are then used for computing the codeword decoding error probability of the RS coded DS-CDMA system using "errors-and-erasures" decoding. Furthermore, the performance of the "errors-and-erasures" decoding technique employing the RTT is compared to that of "error-correction-only" decoding refraining from using side-information over multipath Rayleigh fading channels. As expected, the numerical results show that when using "errors-and-erasures" decoding, RS codes of a given code rate can achieve a higher coding gain than without erasure information.
ÓËÀÀÍÁÀÀÒÀÐ ÕÎÒÛÍ ÍÃÍ ÕÐÑÍÈÉ ÕÍÄ ÝËÅÌÅÍÒÄÈÉÍ ÝËÅÌÅÍÒ ÕÎÎÐÎÍÄÛÍ ÕÀÐÈËÖÀÍ ÕÀÌÀÀÐÀËÛÃ ÒÎÎÖÎÕ ÍÜ
Óäèðòãàë Óëààíáààòàð õîòûí °íã°í õ°ðñí°°ñ íèéò 200 ãàðóé äýýaeèä àòîìûí øèíãýýëòèéí ñïåêòðîñêîïûí àðãààð õèéñýí 8 ýëåìåíòèéí àíàëèçûí ³ð ä³íä ñòàòèñòèê áîëîí ãåîñòàòèñòèê áîëîâñðóóëàëòûã ñòàòèñòèê áî-ëîâñðóóëàëòûí R áîëîí áîëîí ã³éöýòãýâ. Ñòàòèñòèê áîëîí ãåîñòàòèñ-òèê áîëîâñðóóëàëò õèéõèéí °ìí° °ã°ãäëèéí òàðõàëòûã õýâèéí áîëãîõ çîðèëãîîð Áîêñ-êîêñûí áîëîí Ò³êèéí õóâèðãàëòûí àðãóóäûã àøèãëàñàí. Óëìààð Óëààíáààòàð õîòûí °íã°í õ°ðñíèé õ³íä ýëåìåíò³³äèéí òàð-õàëòûí çóðãèéã ãàçàðç³éí ìýäýýëëèéí ñèñòåìèéí çóðàãëàëûí ArcGIS ïðîãðàìì àøèãëàí ³éëäýâ. Ò³ëõ³³ð ³ãñ: °íã°í õ°ðñ, õ³íä ýëåìåíò,ñòàòèñòèê àíàëèç, ãåîñòàòèñòèê àíàëèç, °ã°ãä°ë õóâèðãàëò Îðøèë Óëñ ³íäýñíèé õýìaeýýíä áîëîí Õîò ñóóðèí, Àae ³éëäâýðèéí ãàçðóóäàä õ°ðñ-íèé Pb áîëîí áóñàä õ³íä ìåòàëëûí ñóäàëãàà ìàø îëíîîð õèéãäýae áàéíà. Ýä-ãýýð ñóäàëãàà íü èõýâ÷ëýí õ°ðñíèé õ³íä ìåòàëëûí ñóóðü àãóóëãà áîëîí áî-õèðäñîí àãóóëãûã ÿëãàae îéëãîõ çîðèëãîòîé áàéäàã [1]. Òèéìýýñ îð÷èí ³åèéí øèíaeëýõ óõààíä ñòàòèñòèê °ã°ãäë³³äèéã ³íýí ç°â áîëîâñðóóëàõ áîäèò ìýäýý-ëýë °ã°õ çîðèëãîîð °ã°ãä°ë õóâèðãàõ áîëîí ãåîñòàòèñòèê àíàëèçûí àðãóóäûã °ðã°í àøèãëàõ áîëñîí. Ãåîñòàòèñòèê àíàëèçûí àðãà íü áàéãàëü îð÷íû ìîíè-òîðèíã õèéõ ò°äèéã³é áîõèðäîëòîé öýã á³ðä õ³ð÷ áîõèðäëûã áóóðóóëàõ àðãà õýìaeýý öàã àëäàëã³é àâàõàä ÷óõàë à÷ õîëáîãäîëòîé. Óëààíáààòàð õîòûí õ°ðñ-íèé ñóäàëãààíä ãåîñòàòèñòèê àíàëèçûí àðãóóäààñ Êðèãèíãèéí àðãûã ñîíãîí àâ÷ àøèãëàñàí. Óëààíáààòàð õîòûí °íã°í õ°ðñíèé õ³íä ýëåìåíò³³äèéí òàð-õàëòûí áîõèðäëûí ³íýëãýýíä ãåîñòàòèñòèê àíàëèçûí àðãà àøèãëàñíààð ³íýí *