• The Transactions of the Korea Information Processing Society
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• v.1 no.4
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• pp.502-510
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• 1994

CDMA technique has been largely focused for Wireless Data Communication and Personal Communication Network. ALOHA protocol also has been proven to be effective for Packet Radio Radio Network regardless of low throughput due to channel collisions. In this paper, we evaluate the performance of MS-CDMA-ALOHA (Mini-Slotted-CDMA-ALOHA) system, by analytic and simulation method. The superiority of the MS-CDMA-ALOHA system over conventional Slotted ALOHA and Slotted-CDMA-ALOHA systems are clearly demonstrated for throughput, delay and stability performances.

• International journal of advanced smart convergence
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• v.12 no.4
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• pp.55-62
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• 2023

Slotted-Aloha (S-Aloha) has been widely employed in random access networks owing to its simple implementation in a distributed manner. To enhance the throughput performance of the S-Aloha, connection-based slotted-Aloha (CS-Aloha) has been proposed in recent years. The fundamental principle of the CS-Aloha is to establish a connection with a short-sized request packet before transmitting data packets. Subsequently, the connected node transmits long-sized data packets in a batch of size M. This approach efficiently reduces collisions, resulting in improved throughput compared to the S-Aloha, particularly for a large M. In this paper, we address the short-term fairness of the CS-Aloha, as quantified by Jain's fairness index. Specifically, we evaluate how equitably the CS-Aloha allocatestime slots to all nodes in the network within a finite time interval. Through simulation studies, we identify the impact of system parameters on the short-term fairness of the CS-Aloha and propose an optimal transmission probability to support short-term fairness.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.814-821
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• 2005

When there are many tags using the same frequency around the reader in RFID system, they disturb each other and in the end their response cannot be received by the reader. To solve this disturbance and fast identify the tags, the anti-collision algorithm, which is the core technology in RFID system, is needed. We propose two ALOHA-type Dynamic Framed Slotted ALOHA(DFS-ALOHA) algorithms using Dynamic Slot Allocation(DSA), which dynamically allocates the frame size in accordance with the number of tags and Tag Estimation Method(TEM), which estimates the number of tags around the reader. We also compare the performance of the proposed DFS-ALOHA algorithms with that of the conventional Framed Slotted ALOHA (FS-ALOHA) algorithms and the algorithms proposed by Vogt using OPNET simulation. According to the analysis, the two proposed DFS-ALOHA algorithms(DFS-ALOHA I and DFS-ALOHA II) show better performance than the conventional ALOHA-based algorithms regardless of the number of tags. Although the two proposed DFS-ALOHA algorithms show the similar performance, BFS-ALOHA ll is better because it is easier to be implemented in the system and the complexity is lower.

• Proceedings of the IEEK Conference
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• summer
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• pp.5-9
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• 2004

This paper proposed a systematic analysis for slotted ALOHA with capture effect. This is a generalization for slotted ALOHA system. Based on this model, we can increase the maximum through-put of slotted ALOHA system with two power levels. Lee's algorithm is consider to be an extension of ALOHA system with capture effect. In this paper, we showed that, the choice of Lee's algorithm is not an optimum one. Based on the previous experimental results, we proposed here a more practical analysis for slotted ALOHA system. The result is very accurate and can be applied to other wireless systems which also employed capture effect.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.594-599
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• 2003

This paper proposed to compare and analyze the data throughput of ALOHA and Slotted-ALOHA method which were used to the communication of satellites in an early stage and apply to the data throughput of a transponder in an RFID system. The ALOHA method is the operation priority to a transponder but the Slotted ALOHA method is the operation priority to an reader in an RFID system. Because ALOHA method transmits the data to an reader as a authority of a transponder at random time when generating collisions, therefore, it seems reasonable to conclude that ALOHA method is inefficient for the data throughput and the efficiency of collision interval than Slotted-ALOHA method that synchronizes and controls the transponder in an reader.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.603-606
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• 2019

In this paper, we propose a slotted-ALOHA-based random access protocol and derive the optimal number of random slots that maximize channel throughput when multiple energy harvesting sensor devices perform random access in wireless-powered sensor networks (WPSN). Throughput numerical analysis, we prove that the throughput has a concavity with respect to the number of random slots and obtain the optimal number of slots. Simulation results show that the throughput of the proposed slotted ALOHA-based random access protocol is maximize when the derived optimal number of slots is employed in the considered WPSN.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.3
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• pp.713-720
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• 1996

In recent, the demand of mobile communication system is increasing rapidly. However, since wireless resources is limitted, the protocol to utilize wireless resource efficiently is needed. Up to now, Slotted CDMA_ALOHA(S_CDMA_ALOHA) and Mini-Slotted CDMA_ALOHA(MS_CDMA_ALOHA) methods are proposed as a CDMA_ALOHA mechanism, and it is turned out that MS_CDMA_ALOHA offers betterperformance than S_CDMA_ALOHA mechanism. Also, IS-95 multiple access mechanism has been proposed as common air interface(CAI) protocol of CDMA digital cellular system. However, in former study, the performance evaluations were made without considertion of chnnel characteristics of wireless communication environment. In this paper, a new access mechanism for improring the performance in the DS/CDMA digital cellular environment is suggested. This mechanism is adaptive to the channel condition and based on the conventional MS_CDMA_ALOHA mechanism. Also, the performance of new access mechanism is compared with that of conventional mechanisms, through computer simulation. According tot h simulation results, it is shown that the proposed NA_CDMA_ALOHA(Noise-Adaptation CDMA_ALOHA) mechanism offers better performance than conventional three CDMA_ALOHA mechanisms in view of mean delay time and system throughput characteristics. This phenomenon is due to the fast that NA_CDMA_ALOHA mechanism controls the access attempts efficiently based on the channel condition in heavy traffic environments.

• International Journal of Internet, Broadcasting and Communication
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• v.15 no.3
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• pp.43-51
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• 2023

Slotted ALOHA (S-ALOHA) is a classical medium access control protocol widely used in multiple access communication networks, supporting distributed random access without the need for a central controller. Although stability and delay have been extensively studied in existing works, most of these studies have assumed ideal channel conditions or independent fading, and the impact of time-correlated wireless channels has been less addressed. In this paper, we investigate the queueing delay performance in S-ALOHA networks under time-correlated channel conditions by utilizing a Gilbert-Elliott model. Through simulation studies, we demonstrate how temporal correlation in the wireless channel affects the queueing delay performance. We find that stronger temporal correlation leads to increased variability in queue length, a larger probability of having queue overflows, and higher congestion levels in the S-ALOHA network. Consequently, there is an increase in the average queueing delay, even under a light traffic load. With these findings, we provide valuable insights into the queueing delay performance of S-ALOHA networks, supplementing the existing understanding of delay in S-ALOHA networks.

• The Journal of the Acoustical Society of Korea
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• v.33 no.2
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• pp.126-132
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• 2014

In this paper, a DFSA (Dynamic Framed Slotted ALOHA) based anti-collision algorithm is described and a performance improved algorithm of DFSA and FSA is proposed. The proposed method makes use of expected values and has merits in operation speed by estimating closest value of the number of tags on a single operation. The algorithm compares and analyses number of empty slots and collide slots in accordance with the number of tags, which enables estimation of actual number of tags. we simulated the proposed algorithm and compared it with conventional methods. Results show that our method needs average 18.8 rounds to identify all tags. In case of less than 1000 tags, an average of 18.2 rounds is necessary and an average of 19.2 rounds is needed to identify all tags for more than 1000 tags. The proposed algorithm improves processing speed by 3.1 % comparing to DFSA with cancellation strategy, 10.1 % comparing to DFSA, 37.5 % comparing to FSA(Framed Slotted ALOHA).

• Journal of information and communication convergence engineering
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• v.5 no.3
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• pp.194-199
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• 2007

In this paper, a slotted CDMA_ALOHA protocol with hybrid ARQ is proposed for the wireless CDMA communication networks. The proposed protocol combines the characteristics of the slotted ALOHA, CDMA, and the hybrid ARQ, in order to increase the throughput by reducing the number of retransmissions when the channel experiences heavy traffic. The main feature of the proposed protocol is the utilization of the forward error correction capability to correct errors that appear after the CDMA dispreading of the packets. The base station does not need to ask so often for retransmission of erroneous packets. It will request for retransmission only when the FEC capability is exceeded. The performance of the proposed protocol is analyzed by considering the packet collision probability as well as the bit error probability. The numerical results show that the system throughput is closely related to the bit error rate of the wireless link and the FEC coding rate.