Code Division MultipleAccess Techniques in Optical Fiber Networks—Part I: Fundamental Principles
ABSTRACT An examination is made of fiberoptic codedivision
multipleaccess (FOCDMA), a technique in which low information data
rates are mapped into veryhighrate address codes (signature sequences)
for the purpose of achieving random, asynchronous communications free of
network control, among many users. The need for a special class of
signature sequences to achieve the multipleaccess capability using
fiberoptic signal processing techniques is discussed. A class of
signature sequences called optical orthogonal codes (OOCs) that provide
the auto and crosscorrelation properties required for FOCDMA is
introduced and used in an experiment to show the principles of FOCDMA.
The experiment demonstrates the auto and crosscorrelation properties
of the codes. The concept of optical disk patterns, an equivalent way of
representing the OOCs, is introduced. The patterns are used to derive
the probability density functions associated with any two interfering
OOCs. A detailed study of different interference patterns is presented,
and the strongest and the weakest interference patterns are determined

 "There has been a growing interest in deploying the optical code division multiple access (OCDMA) technique for the next generation highspeed optical fiber networks [1] [2] [3] [4]. OCDMA is a promising technology since it offers several advantages in local area networks such as, high speed, huge bandwidth, bursty traffic, and simultaneous and asynchronous access with no waiting time through the assignment of unique signature sequences [3]. "

 "A mapping matrix maps the nonzero dimensions to the dimensional complex domain. Similar to optical orthogonal codes (OOC) [9], this can be also represented by a binary vector of length indicating the positions of nonzero entries of the codebook. An SCMA encoder contains separate layers. "
Article: SCMA Codebook Design
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ABSTRACT: Multicarrier CDMA is a multiple access scheme in which modulated QAM symbols are spread over OFDMA tones by using a generally complex spreading sequence. Effectively, a QAM symbol is repeated over multiple tones. Low density signature (LDS) is a version of CDMA with low density spreading sequences allowing us to take advantage of a near optimal message passing algorithm (MPA) receiver with practically feasible complexity. Sparse code multiple access (SCMA) is a multidimensional codebookbased nonorthogonal spreading technique. In SCMA, the procedure of bit to QAM symbol mapping and spreading are combined together and incoming bits are directly mapped to multidimensional codewords of SCMA codebook sets. Each layer has its dedicated codebook. Shaping gain of a multidimensional constellation is one of the main sources of the performance improvement in comparison to the simple repetition of QAM symbols in LDS. Meanwhile, like LDS, SCMA enjoys the low complexity reception techniques due to the sparsity of SCMA codewords. In this paper a systematic approach is proposed to design SCMA codebooks mainly based on the design principles of lattice constellations. Simulation results are presented to show the performance gain of SCMA compared to LDS and OFDMA. 
 "A (v, k, λ)OOC is a (v, k, λ a , λ c )OOC with the property that λ a = λ c = λ. A (v, k, λ a , λ c )OOC was first introduced by Salehi, as signature sequences to facilitate multiple access in optical fibre networks [24] [25]. Since then many optimal (v, k, 1)OOCs are constructed, see [1,4–6,9,10,12,16,29] for some of the examples . "
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ABSTRACT: In 1996, Yang introduced variableweight optical orthogonal code for multimedia optical CDMA systems with multiple quality of service (QoS) requirements. Let W={w1,…,wr}W={w1,…,wr} be an ordering of a set of rr integers greater than 11, λλ be a positive integer (auto and crosscorrelation parameter ), and Q=(q1,…,qr)Q=(q1,…,qr) be an rrtuple (weight distribution sequence ) of positive rational numbers whose sum is 11. A (v,W,λ,Q)(v,W,λ,Q) variableweight optical orthogonal code ((v,W,λ,Q)(v,W,λ,Q)OOC) is a collection of (0,1)(0,1) sequences with weights in WW, auto and crosscorrelation parameter λλ. Some work has been done on the construction of optimal (v,W,1,Q)(v,W,1,Q)OOCs, while little is known on the construction of (v,W,λ,Q)(v,W,λ,Q)OOCs with λ≥2λ≥2. It is well known that (v,W,λ,Q)(v,W,λ,Q)OOCs with λ≥2λ≥2 have much bigger cardinality than those of (v,W,1,Q)(v,W,1,Q)OOCs for the same v,W,Qv,W,Q. In this paper, a new upper bound on the number of codewords of (v,W,λ,Q)(v,W,λ,Q)OOCs is given, and infinite classes of optimal (v,{3,4},2,Q)(v,{3,4},2,Q)OOCs are constructed.Discrete Mathematics 08/2014; 328:16–22. DOI:10.1016/j.disc.2014.03.028 · 0.57 Impact Factor