Design of Signature Sequences for Overloaded CDMA and Bounds on the Sum Capacity With Arbitrary Symbol Alphabets

Alishahi, Kasra; Dashmiz, S.; Pad, Pedram; Marvasti, Farokh

doi:10.1109/tit.2011.2172391

Cited by 22 publications

(33 citation statements)

References 37 publications

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“…Proof: From Theorem 3 and the upper bounds of corresponding CDMA in [8], the above inequality can be derived trivially. Example 6 (Noiseless Case): For the noiseless case, we assume that the pdf of the noise is an impulse, thereforẽ…”

Section: Theorem 4: For the Noisy Case We Havementioning

confidence: 99%

“…In [2], the authors have also developed uniquely detectable overloaded matrices for binary inputs independently. In the continuation of [2], the authors extended these matrices in [2] to non-binary finite real and complex signature codes [8].…”

Section: Introductionmentioning

confidence: 99%

“…For binary CDMA, only asymptotic results were known [11,12] prior to our recent papers [2,8,13]. For non-binary finite input and signature alphabets, asymptotic sum capacity results were developed in [3].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Generalisation of code division multiple access systems and derivation of new bounds for the sum capacity

Dashmiz¹,

Takapoui

Moazeni

et al. 2014

IET Communications

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In this study, the authors explore a generalised scheme for the synchronous code division multiple access (CDMA). In this scheme, unlike the standard CDMA systems, each user has different codewords for communicating different messages. Two main problems are investigated. The first problem concerns whether uniquely detectable overloaded matrices (an injective matrix, i.e. the inputs and outputs are in one-to-one correspondence depending on the input alphabets) exist in the absence of additive noise, and if so, whether there are any practical optimum detectors for such input codewords. The second problem is about finding tight bounds for the sum channel capacity. In response to the first problem, the authors have constructed uniquely detectable matrices for the generalised scheme and the authors have developed practical maximum likelihood detection algorithms for such codes. In response to the second problem, lower bounds and conjectured upper bounds are derived. The results of this study are superior to other standard overloaded CDMA codes since the generalisation can support more users than the previous schemes.

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Section: Theorem 4: For the Noisy Case We Havementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Generalisation of code division multiple access systems and derivation of new bounds for the sum capacity

Dashmiz¹,

Takapoui

Moazeni

et al. 2014

IET Communications

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show abstract

“…Recently, detecting matrices have been applied to wireless CDMA and optical CDMA (OCMDA) systems in [6]- [7]. The authors in [6] considered the Kronecker construction and introduced a maximum likelihood (ML) receiver which can be simple in some cases.…”

Section: Introductionmentioning

confidence: 99%

Detecting matrices for random CDMA systems

2013

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This paper studies detecting matrices in random dense and sparse Code Division Multiple Access (CDMA) systems. Detecting matrices were originally introduced in the coin weighing problem. Such matrices can be used in CDMA systems in over-loaded scheme where the number of users is greater than the number of chips. We drive some conditions in the large system limit for binary and bipolar random CDMA systems to ensure that any random matrix is a detecting matrix. Furthermore, we extend our results to sparse random ternary matrices that have been using in the sparse CDMA literature. Finally, a construction method for the sparse detecting matrices is introduced.Index Terms-detecting matrix, CDMA system, overloaded scheme, sparse CDMA, coin weighing.

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“…The fundamental limits of asymptotic synchronous CDMA systems have been studied in [1][2][3][4][5] by modeling the spreading sequences with random sequences. In our previous papers, we studied bounds on the sum capacity for finite synchronous CDMA systems together with the design of suboptimal codes that approach the sum capacity for highly overloaded CDMA systems at high Signal-to-Noise ratios (SNR) [6][7][8]. However, the assumption that users are synchronous is not valid for optical networks and the uplink wireless CDMA systems.…”

Section: Introductionmentioning

confidence: 99%

Sum capacity bounds and design of errorless codes for binary asynchronous CDMA systems

Dashmiz

Mansouri

Najafi

et al. 2012

2012 19th International Conference on Telecommunications (ICT)

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In this paper, some codes are designed for a binary chip-asynchronous CDMA system which guarantee errorless communication in the absence of noise. These codes also show good performance for noisy channels. In addition, lower and upper bounds for the sum channel capacity are derived for finite and asymptotic cases with the assumption of both noiseless and noisy channels. The results are derived assuming that user delays are known at the receiver end. The performance of proposed codes in the noisy case is also compared to both Gold sequences and a similar class of binary sequences with constrained amount of correlation.

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Design of Signature Sequences for Overloaded CDMA and Bounds on the Sum Capacity With Arbitrary Symbol Alphabets

Cited by 22 publications

References 37 publications

Generalisation of code division multiple access systems and derivation of new bounds for the sum capacity

Generalisation of code division multiple access systems and derivation of new bounds for the sum capacity

Detecting matrices for random CDMA systems

Sum capacity bounds and design of errorless codes for binary asynchronous CDMA systems

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