The effect of chip waveform on the performance of CDMA systems in multipath, fading, noisy channels

Anjaria, Rashmin; Wyrwas, R.

doi:10.1109/vetec.1992.245483

Cited by 22 publications

(19 citation statements)

References 6 publications

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“…The resulting inphase and quadrature signals are (6) (7) where is the carrier phase angle and its angular frequency. The resulting transmitted signal from the th user is obtained by the sum (8) At the front end of the receiver, the signal present is the sum of delayed versions of the transmitted signals of all active users, with additive thermal noise (9) where is a white Gaussian process with power spectral density (PSD) modeling the thermal noise, is the received signal power in each inphase and quadrature component, assumed to be the same for all users. This "perfect power control" assumption is only used for simplicity and has no real impact on the validity of the subsequent results and conclusions.…”

Section: System Modelmentioning

confidence: 99%

“…To illustrate the above figures of merit, we use four examples of known modulations schemes, namely OQPSK, MSK, SFSK (as proposed in [7]), and time-domain raised-cosine shaped OQPSK [8], referred to as TDRC. 4 The first three modulations are examples of constant-envelope modulations whereas the last one is a varying envelope scheme as can be seen from Table I.…”

Section: Bit-error Performancementioning

confidence: 99%

“…Also, optimal pulse shaping 0090-6778/99$10.00 © 1999 IEEE was considered in [12] for a different system model based on orthogonal multicarrier quasi-synchronous CDMA. Additional results that highlight the differences in performance (mainly bit-error probability) between several known pulses can be found in [8] and [13], and the importance of chip waveform shaping in the mitigation of multipath effects in DS-CDMA was also addressed in [14].…”

Section: Introductionmentioning

confidence: 99%

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DS-CDMA chip waveform design for minimal interference under bandwidth, phase, and envelope constraints

Landolsi

Stark

1999

IEEE Trans. Commun.

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Abstract-This paper investigates the effect of chip waveform shaping on the error performance, bandwidth confinement, phase continuity, and envelope uniformity in direct-sequence codedivision multiple-access communication systems employing offset quadrature modulation formats. An optimal design methodology is developed for the problem of minimizing the multipleaccess interference power under various desirable signal constraints, including limited 99% and 99.9% power bandwidth occupancies, continuous signal phase, and near-constant envelope. The methodology is based on the use of prolate spheroidal wave functions to obtain a reduced-dimension discrete constrained optimization problem formulation. Numerous design examples are discussed to compare the performance achieved by the optimally-designed chip waveforms with other conventional schemes, such as offset quadrature phase-shift keying, minimumshift keying (MSK), sinusoidal frequency-shift keying (SFSK), and time-domain raised-cosine pulses. In general, it is found that while the optimized chip pulses achieved substantial gains when no envelope constraints were imposed, these gains vanish when a low envelope fluctuation constraint was introduced. In particular, it is also shown that MSK is quasi-optimal with regard to the 99% bandwidth measure, while the raised-cosine pulse is equally good with both the 99% and 99.9% measures, but at the expense of some envelope variation. On the other hand, SFSK is quasioptimal with regard to the 99.9% bandwidth occupancy, among the class of constant-to-low envelope variation pulses.Index Terms-Chip waveform optimization, direct-sequence CDMA, envelope uniformity, multiple-access interference, phase continuity.

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Section: System Modelmentioning

confidence: 99%

Section: Bit-error Performancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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DS-CDMA chip waveform design for minimal interference under bandwidth, phase, and envelope constraints

Landolsi

Stark

1999

IEEE Trans. Commun.

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“…In this paper, the following raised-cosine of time-limited chip waveform is considered [13][14][15]:…”

Section: Simulation Resultsmentioning

confidence: 99%

A low‐complexity adaptive receiver for DS‐CDMA systems in unknown code delay environment

Chen

Ueng

Lin

2011

Int J Communication

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In direct-sequence code division multiple access (DS/CDMA) multiuser communication systems in multipath channels, both intersymbol interference (ISI) and multiple-access interference (MAI) must be considered. The multipath channel characterizes the propagation effects including the timing offset and delays, etc. Traditionally, we use the delay-locked loop (DLL) code tracking loop to recover the timing delay. But DLL cannot work well in multipath environment. In this paper, we propose a low-complexity adaptive receiver to suppress ISI/MAI and solve the timing offset problems without using conventional DLL code tracking loop. The proposed receiver employs an adaptive filter whose weights are adapted using a block least-mean square error algorithm with fractional sampling. Simulations confirm the good performance, including learning curves and theoretical analysis of minimum mean-square error, of the proposed receiver. Copyright (C) 2010 John Wiley & Sons, Ltd

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“…It is well known that the proper design of chip waveforms can improve the spectral efficiency and performance of direct sequence code division multiple access (DS-CDMA) systems [1,5,6,[8][9][10][11][12][13]17]. DS-CDMA using an arbitrary full response chip waveform, which is time-limited to one chip interval, was studied in Refs.…”

Section: Introductionmentioning

confidence: 99%

Second order polynomial class of chip waveforms for band-limited DS-CDMA systems

Song

Leung

2007

Wireless Pers Commun

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The conventional frequency domain square-root raised cosine (Nyquist) chip waveform has much poorer anti-multiple-access-interference (anti-MAI) capability than the optimal bandlimited waveform in direct sequence code division multiple access (DS-CDMA) systems. However, the digital implementation of the optimal chip pulse is very costly due to the slow decaying rate of the time waveform. In addition, its eye diagram and envelope uniformity are worse than the Nyquist pulse for a wide range of roll-off factor, which will incur performance degradation due to timing jitters and post non-linear processing. In this paper, based on an elementary density function of a second-order polynomial, a class of second-order continuity pulses is proposed. From this class of pulses, we can find some members having faster decaying rate, bigger eye opening, more uniform envelope and stronger anti-MAI capability than the Nyquist waveform. The normalized-bandwidth-pulse-shape-factor product, the decaying rate of the tail of the time waveform, the opening of the eye diagram, and the envelope uniformity of the second-order continuity pulses are addressed in the paper that provide the basic information for the selection of the chip pulse for CDMA systems.

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The effect of chip waveform on the performance of CDMA systems in multipath, fading, noisy channels

Cited by 22 publications

References 6 publications

DS-CDMA chip waveform design for minimal interference under bandwidth, phase, and envelope constraints

DS-CDMA chip waveform design for minimal interference under bandwidth, phase, and envelope constraints

A low‐complexity adaptive receiver for DS‐CDMA systems in unknown code delay environment

Second order polynomial class of chip waveforms for band-limited DS-CDMA systems

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