IIJ Vol. 2 / No. 1 (2010)

Title: Analysis Throughput Multi-code Multicarrier CDMA S-ALOHA

Authors: Hoga Saragih

Affiliation: Bina Nusantara University Jakarta, Indonesia

Abstract: This paper proposes an integrated system consisting of multi-code multicarrier code-division multiple accesses (MC-MC-CDMA) with random access scheme Slotted ALOHA (S-ALOHA), named multi-code multicarrier CDMA S-ALOHA, respectively. The performance analysis of both systems is stated as throughput. Multi-code multicarrier CDMA S-ALOHA is proposed to improve performance of multi-code CDMA or multicarrier CDMA. In multi-code multicarrier CDMA S-ALOHA, each user is allowed to transmit multiple orthogonal codes, so the proposed MC-MC-CDMA S-ALOHA system can support various data rates, as required by the next generation standard. In MC-MC-CDMA S-ALOHA the initial data is serial to parallel converted to a number of lower rate data streams. Each stream which consists of part of the initial data called sub-packet will be coded to a number of multiple orthogonal codes then modulated using specific spreading code for each user, and all sub stream signal are transmitted in parallel on different sub carrier. The combination of a multi-code scheme and a multi-carrier code division multiple access (MC-CDMA) and ALOHA, called MC-MC-CDMA S-ALOHA, with dual medium, is proposed and analyzed in an AWGN channel. Each medium has different characteristics in data rate transmission. The high-rate bit transmitted data user is serial to parallel converted into low-rate bit streams and assigned with multiple-orthogonal code. Each low-rate bit stream is transmitted over L orthogonal sub-carrier. In this paper we divide interference into different types depending on codes and sub-carriers in this system, and we carry out our analysis to obtain the BER and throughput taking into account all these types. The performance of the system is improved as the number of assigned codes and sub-carriers increases, and also the results show that the proposed MC-MC-CDMA S-ALOHA system outperforms both multi-carrier CDMA S-ALOHA and multi-code CDMA S-ALOHA in fixed bandwidth allocation. The results show that both systems have higher throughput for high bit rate signal transmission than multi-code CDMA S-ALOHA or multicarrier CDMA S-ALOHA. It is also shown that the throughput of both systems improve as the number of code and sub carriers, while the increase of sub packet length degrades the throughput of both systems.

Keywords: Multiple-access protocols, CDMA, S-ALOHA, Multicode Multicarrier CDMA S-ALOHA..

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