Sequences for Oversaturated CDMA Channels

Vanhaverbeke, F.; Moeneclaey, Marc

doi:10.1109/isssta.2008.143

Cited by 4 publications

(2 citation statements)

References 9 publications

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“…The concept of overloading in CDMA as a solution to the strict capacity limit of its conventional counterpart has drawn frequent interest of the researchers in the past and continuously evolved though several phases. The existing research in the field can be broadly classified into problems like the following: (i) designing of the signature matrices (uniquely decodable (UD) and non‐UD ); (ii) development of reusing techniques for the existing non‐overloaded matrices; (iii) designing of multi user detectors (MUD) ; (iv) adding system level improvisations for improved error performance ; and (v) study of capacity and performance under different channel and input conditions , for synchronous or asynchronous transmission. For matrix C being considered as UD over x , the inequality C x 1 ≠ C x 2 is true for x 1 and x 2 denoting two different input vectors, whereas its major applications in literature are recorded in the field of multiuser encoding for physical layer network coding , overloaded CDMA , and T‐user channels .…”

Section: Introductionmentioning

confidence: 99%

“…However, most of them are hardly accompanied by an efficient decoder (both in complexity and error performance) for noisy transmission. Where the recovery performance of a decoder in the multi‐user environment like CDMA is directly influenced by the level of total MAI, most of the proposed systems in literature deal with the type of MAI pattern, which is completely random in nature. Because of the unpredictability and non‐uniformity in its distribution among the signatures, it's accurate estimation (for each signature) for the purpose of cancellation is considered nearly impossible because of the demand of complex methods involving MLD or iterative decoders.…”

Section: Introductionmentioning

confidence: 99%

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Twin tree hierarchy: a regularized approach to construction of signature matrices for overloaded CDMA

Singh

Amini

et al. 2016

Wirel. Commun. Mob. Comput.

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Overloaded code division multiple access being the only means of the capacity extension for conventional code division multiple access accommodates more number of signatures than the spreading gain. Recently, ternary Signature Matrices with Orthogonal Subsets (SMOS) has been proposed, where the capacity maximization is 200%. The proposed multi-user detector using matched filter exploits the twin tree hierarchy of correlation among the subsets to guarantee the errorless recovery. In this paper, we feature the non-ternary version of SMOS (i.e., 2k-ary SMOS) of same capacity, where the binary alphabets in all the k constituent (orthogonal) subsets are unique. Unlike ternary, the tree hierarchy for 2k-ary SMOS is non-uniform. However, the errorless detection of the multi-user detector remains undeviated. For noisy transmission, simulation results show the error performance of the right child for each subset of 2k-ary to be significantly improved over the left. The optimality of the right child of the largest (Hadamard) subset is also discovered. At higher loading, for larger and smaller subsets the superiority is reported for the 2k-ary and ternary, respectively, and the counter-intuitive deviations observed for the lower loading scenarios are logically explained. For the overall capacity maximization being 150%, superiority is featured by the 2k-ary, but beyond, it becomes a conditional entity.where y and r D CAx are the noisy and noiseless received vector for C D OEc 1 , c 2 , c 3 , , c M being a N M matrix representing M signatures of length N, x D OEx 1 , x 2 , x 3 , , x M T represents the input data vector corresponding to all M users or signatures, A D I M M = Identity matrix with diagonal elements representing the amplitudes assuming the system to be perfectly power controlled, and n denotes zero mean Additive white Gaussian noise vector. While for conventional (underloaded) CDMA the maximum achievable value of M is N (i.e., M Ä N), this capacity limit can be maximized beyond N (i.e., M > N) using the feature of overloaded CDMA, which subsequently leads to the significant rise in the loading (overloading) factorˇD . M =N/.Over a decade, the popularity of CDMA besides the military applications can be well-speculated from its growing commercialization of the wireless communication systems like Third Generation cellular architecture using wideband CDMA (WCDMA). Although for the Fourth Generation architecture, the scope of participation of CDMA has been fully obliterated, its further advancement in terms of sparse coded multiple access [1] using low density signature [2] has regained its priority and been prospectively provisioned for the Fifth Generation [3] cellular architecture.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Twin tree hierarchy: a regularized approach to construction of signature matrices for overloaded CDMA

Singh

Amini

et al. 2016

Wirel. Commun. Mob. Comput.

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Set of uniquely decodable codes for overloaded synchronous CDMA

et al. 2016

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Overloaded Spread Spectrum OFDMA in Outdoor Environment in the Low Interleaving Scenario

Y Arun Kumar Reddy

2024

IJARSCT

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The development of mobile communication technology starts with creating or modifying a Radio Access Technique (RAT) to meet user needs and increase capacity. This paper focuses on enhancing spectral efficiency and average throughput using an OFDM-based multiple access method, specifically overloaded spread spectrum OFDMA. The study found that with 24% overloading for BPSK modulation, there is approximately a 30% increase in spectral efficiency in outdoor scenarios. There is a significant improvement using higher modulation as well. This improvement highlights the potential of Overloaded Spread Spectrum OFDMA to optimize mobile communication systems, ensuring better resource utilization and system performance to handle the growing demand for data and connectivity effectively

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Sequences for Oversaturated CDMA Channels

Cited by 4 publications

References 9 publications

Twin tree hierarchy: a regularized approach to construction of signature matrices for overloaded CDMA

Twin tree hierarchy: a regularized approach to construction of signature matrices for overloaded CDMA

Set of uniquely decodable codes for overloaded synchronous CDMA

Overloaded Spread Spectrum OFDMA in Outdoor Environment in the Low Interleaving Scenario

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