Dual-threshold sequential detection code synchronization for an optical CDMA network in the presence of multi-user interference

Mustapha, M.M.; Ormondroyd, R.F.

doi:10.1109/50.908711

Cited by 24 publications

(25 citation statements)

References 16 publications

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“…In the conventional parallel search method [9], when the first preamble bit is received, the LLR values for all synchronization candidates l {l = 0, 1, . .…”

Section: Conventional Methodsmentioning

confidence: 99%

“…As the spreading code, we use optical orthogonal code (OOC), for which the maxima of the autocorrelation and the off-peak cross correlation are both 1. The code length and the number of weights are F and K. It is assumed that the chip synchronization is established [9]. The correct synchronization point is determined from F types of synchronization candidates equal to the code sequence length.…”

Section: Synchronization Search Methodsmentioning

confidence: 99%

“…Serial search, in which synchronization candidate positions are searched one by one [7,8] and parallel search, which simultaneously searches all synchronization candidate positions [9], are known. Although serial search is simpler, the number of preamble bits until synchronization capture is larger than in parallel search.…”

Section: Introductionmentioning

confidence: 99%

“…In the synchronization method by parallel search [9], the bit "1" is continuously sent as preamble bits. On the receiver side, the synchronization points are captured by means of the logarithmic likelihood ratio (LLR) for signal decision.…”

Section: Introductionmentioning

confidence: 99%

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A synchronization method deselecting candidate positions with chip level detection for optical CDMA

Iwata

Kamakura

Sasase

2004

Electron. Comm. Jpn. Pt. I

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SUMMARYIn order to reduce the number of preamble bits required for synchronization at correct positions, a method of synchronization by deselecting the candidate positions for synchronization is proposed. As decision methods for each preamble bit, a method using the threshold detection and a method using chip level detection are discussed. Both methods make use of the fact that the preamble bit is the bit "1": any synchronization position judged not to be a "1" bit even once is deselected as a candidate. In this way, the only position eventually remaining without being deselected is judged to be the synchronization position. As a result, it is possible to carry out synchronization with fewer preamble bits than the conventional method in which bit decision is based on the logarithmic likelihood ratio of the continuously transmitted preamble bits. A theoretical analysis is made under the assumption that the output of the photodetector follows a Poisson distribution. It is found that the proposed method can perform synchronization within a shorter time than the conventional synchronization method. Further, in the method using chip level detection, it is shown that synchronization is achieved in a shorter time even if the bit decision threshold is fixed.

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“…In the conventional parallel search method [9], when the first preamble bit is received, the LLR values for all synchronization candidates l {l = 0, 1, . .…”

Section: Conventional Methodsmentioning

confidence: 99%

Section: Synchronization Search Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A synchronization method deselecting candidate positions with chip level detection for optical CDMA

Iwata

Kamakura

Sasase

2004

Electron. Comm. Jpn. Pt. I

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“…However, due to complex system requirements, full asynchronism is very difficult to implement in practice while real-time simultaneous MAI suppression, due to imperfect spreading codes, is still a hot research topic and under investigation [70,72,75,79,86,[92][93][94][95][96]. On the other hand, the synchronous scheme takes advantage of accommodating higher numbers of subscribers due to the time-shift property of the codes, and although the synchronization is difficult some methods have been proposed and are in use [97][98][99].…”

Section: Motivations For Optical Cdma Communicationsmentioning

confidence: 99%

Introduction to Optical Communications

Ghafouri‐Shiraz

Karbassian

2012

Optical CDMA Networks

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The invention of the solid state ruby laser (acronym for light amplification by stimulated emission of radiation) in May 1960 [1] and the He-Ne gas laser [2] in December 1960 has led to some wide-ranging and very significant scientific and technological progress. This so-called 'discovery of the century', followed by the first use of semiconductor lasers [3][4][5] in communications, heralded the start of optical communications. The laser provided a powerful coherent light source together with the possibility of modulation at high frequency, and this opened up a new portion of the electromagnetic spectrum with frequencies many times higher than those commonly available in radio communication systems. In addition the narrow beam divergence of the laser made enhanced free-space optical transmission a practical possibility.Since optical frequencies are of the order of 100 THz, and information capacity increases directly with frequency bandwidth, the laser potentially offers a few order of magnitude increase in available bandwidth compared with microwave systems. Thus, by using only a small portion of the available frequency spectrum, a single laser could, in principle, carry millions of telephone conversations or TV channels.With the potential of such wideband transmission capabilities in mind, a number of experiments [6] using atmospheric optical channels were carried out in the early 1960s. These experiments showed the feasibility of modulating a coherent optical carrier wave at very high frequencies. However, the high cost of development for all the necessary components, and the limitations imposed on the atmospheric channel by rain, fog, snow and dust make such high-speed systems economically unattractive. However, numerous developments of free-space optical channel systems operating at baseband frequencies were in progress for earth-to-space communications [7,8].It soon became apparent that some form of optical waveguide was required. By 1963, bundles of several hundred glass fibres were already being used for small-scale Optical CDMA Networks: Principles, Analysis and Applications, First Edition. Hooshang Ghafouri-Shiraz and M. Massoud Karbassian.

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Use of optical orthogonal codes with 2‐PPM and BCH codes for time‐hopping optical CDMA system

Iwata

Sawagashira

Sonoda

et al. 2003

Electron. Comm. Jpn. Pt. I

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SUMMARYIn this paper, we propose the use of 2-PPM for time-hopping optical code division multiple access (CDMA) where the transmission bits are embedded in the weighted positions of signature sequences. To use 2-PPM, each chip is composed of two slots, and an optical pulse is transmitted in either slot, according to a bit transmitted in the corresponding weighted position. In the receiver, threshold detection is used, which makes bits that have suffered multiple access interference (MAI) erasure bits. By using codeword bits of the BCH codes for the transmitted bits, the effect of MAI is removed in the decoding of BCH codes. Since the effect of MAI is treated as erasure bits, the proposed method reduces the effect of MAI more than the decoding procedures treating them as error bits. In addition, the use of extended BCH (eBCH) codes allows us to reduce the effect of MAI more efficiently. We analyze the bit error rate (BER) of the proposed system, assuming that the photodetector outputs follow the Poisson distribution. The numerical results show that the proposed system achieves better BER performance than the system without Manchester signaling.

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Dual-threshold sequential detection code synchronization for an optical CDMA network in the presence of multi-user interference

Cited by 24 publications

References 16 publications

A synchronization method deselecting candidate positions with chip level detection for optical CDMA

A synchronization method deselecting candidate positions with chip level detection for optical CDMA

Introduction to Optical Communications

Use of optical orthogonal codes with 2‐PPM and BCH codes for time‐hopping optical CDMA system

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