• 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.

• 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.

• 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.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.28 no.1
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• pp.129-133
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• 2005

Slotted ALOHA(S-ALOHA) is widely used in local wireless network. We analyze the performance of contention-based model in wireless LAN using S-ALOHA protocol. We analyze the performance of binary exponential backoff (BEB) algorithm under the slotted ALOHA protocol: whenever a node's message which tries to reserve a channel is involved in a collision for the ith time, it chooses one of the next $2^i$ frames with equal probability and attempts the reservation again. We derive the expected access delay and throughput which is defined as the expected number of messages that reserve a channel in a frame. A simulation study is performed to verify our method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.1
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• pp.155-162
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• 1999

In this paper, an R_ALOHA_CDMA protocol is proposed for voice and data integrated services in the hybrid TDMA/CDMA wireless networks. In the hybrid TDMA/CDMA systems, the backward logical channels are composed of time slots with multiple spreading codes per slot. In the proposed protocol, a voice terminal can reserve a spreading code to transmit voice packets during a talkspurt. On the other hand, whenever a data terminal generates a packet, it transmits the packet through one of the available spreading codes. Throughout the results, it is shown that the system capacity increases in proportion to the number of spreading codes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.687-708
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• 2017

The machine-to-machine (M2M) communication is featured by tremendous number of devices, small data transmission, and large uplink to downlink traffic ratio. The massive access requests generated by M2M devices would result in the current medium access control (MAC) protocol in LTE/LTE-A networks suffering from physical random access channel (PRACH) overload, high signaling overhead, and resource underutilization. As such, fairness should be carefully considered when M2M traffic coexists with human-to-human (H2H) traffic. To tackle these problems, we propose an adaptive Slotted ALOHA (S-ALOHA) and time division multiple access (TDMA) hybrid protocol. In particular, the proposed hybrid protocol divides the reserved uplink resource blocks (RBs) in a transmission cycle into the S-ALOHA part for M2M traffic with small-size packets and the TDMA part for H2H traffic with large-size packets. Adaptive resource allocation and access class barring (ACB) are exploited and optimized to maximize the channel utility with fairness constraint. Moreover, an upper performance bound for the proposed hybrid protocol is provided by performing the system equilibrium analysis. Simulation results demonstrate that, compared with pure S-ALOHA and pure TDMA protocol under a target fairness constraint of 0.9, our proposed hybrid protocol can improve the capacity by at least 9.44% when ${\lambda}_1:{\lambda}_2=1:1$and by at least 20.53% when ${\lambda}_1:{\lambda}_2=10:1$, where ${\lambda}_1,{\lambda}_2$ are traffic arrival rates of M2M and H2H traffic, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.7
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• pp.1272-1281
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• 1994

CDMA technique has been largely focused for Wireless Data Network and PCN. ALOHA protocol also has been proven to be effective for Packet Radio Network regardless of low throughput due to channel colisions. In this paper, we evaluate the performance of CDMA_ALOHA scheme, denoted as S_CDMA_ALOHA(Soltted_CDAM_ALOHA) and MS_CDMA_ALOHA(Minislotted_CDMA_ALOHA) system, by analytic and simulation method. The superiority of the CDMA_ALOHA systems over conventional Slotted ALOHA system are clearely demonstrated for throughput, delay and stability performances. The MS_CDMA_ALOHA scheme provides better delay and throughput performance than the S_CDMA_ALOHA scheme.

• 한국ITS학회:학술대회논문집
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• 2002.11a
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• pp.31-34
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• 2002

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1A
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• pp.50-57
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• 2009

Tag collection is one of the major functions in RFID systems. In this paper, we propose a multichannel slotted-aloha anticollision protocol to mitigate the tag collision problem and improve tag collection performance in active RFID systems. In the proposed anticollision protocol, while an RFID reader transmits commands to multiple RFID tags via a common channel, it receives multiple tag responses over multiple channels simultaneously. We also implemented an active RFID system supporting the proposed anticollision protocol. In experiments with the implemented reader and 60 tags, the proposed dual-channel slotted-aloha anticollision protocol showed a large improvement in tag collection performance compared with the single-channel slotted-aloha anticollision protocol. With 60 tags, the average time spent on tag collection using the dual-channel anticollision protocol was 600.543 ms, which was 46.3% of the 1289.721 ms required using the single-channel anticollision protocol.

• 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.