Opportunistic Multichannel Aloha: Distributed Multiaccess Control Scheme for OFDMA Wireless Networks

Kai, Bai; Zhang, Junshan

doi:10.1109/tvt.2006.874119

Cited by 44 publications

(34 citation statements)

References 13 publications

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“…This value is determined by the binary exponential backoff algorithm after each unsuccessful transmission until it reaches (3) where is the number of transmission attempts. The initial value of the backoff counter is set as for all STAs in order to demonstrate the advantage of the proposed opportunistic scheme.…”

Section: System Modelmentioning

confidence: 99%

“…An opportunistic Aloha for the uplink transmissions in OFDMA wireless networks is presented in [3]. Therein, a set of subchannels is allocated to a contending user under the condition that its obtained subchannel gains derived from the instantaneous channel-state information (CSI) are greater than the defined threshold.…”

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confidence: 99%

“…This work gives the subchannel assignment solution from the opportunistic viewpoint, but collision resolution is not taken into account. Chang et al [4] put forward a collision resolution policy for the opportunistic Aloha scheme of [3], where collided good subchannels are set with a random backoff time for future retrial, rather than discarded. Furthermore, a backoff mechanism is shown in [5], where all users estimate their channel power gains and compare them with a predefined 0885-8977/$31.00 © 2012 IEEE backoff threshold.…”

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confidence: 99%

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Opportunistic Random-Access Scheme Design for OFDMA-Based Indoor PLC Networks

Ouzzif¹,

Saoudi²

2012

IEEE Trans. Power Delivery

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Abstract-Multiuser systems can benefit from multiuser diversity by assigning channels to users with better channel conditions at different time instants. In this paper, we present an opportunistic random-access scheme for orthogonal frequency-division multiple-access-based indoor power-line communication systems, based on time-and frequency-varying channel conditions, to exploit multiuser diversity. The proposed scheme dynamically adjusts the backoff time of each user according to its own channel-state variations in time and frequency domains during the contention procedure and, thus, "better" users have a higher priority to contend over their favorable subchannels. Moreover, subchannels are assigned to users with better channel conditions in order to further enhance the system throughput. In addition, an analytical throughput model for such a multiuser and multichannel system is derived to obtain the optimal parameter settings of the proposed access scheme. Simulation results show that the proposed scheme provides significant improvement in system throughput even in the case where the number of users highly exceeds that of subchannels.Index Terms-Crosslayer optimization, multiuser diversity, opportunistic communications, orthogonal frequency-division multiple access (OFDMA), power-line communication (PLC).

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Section: System Modelmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Opportunistic Random-Access Scheme Design for OFDMA-Based Indoor PLC Networks

Ouzzif¹,

Saoudi²

2012

IEEE Trans. Power Delivery

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“…Several random access protocols have been proposed for OFDMA networks, see for example [1]- [3]. In [1], the authors proposed an opportunistic multi-channel Aloha in which the transmission probability is adapted based on the channel state information in each sub-channel.…”

mentioning

confidence: 99%

“…In [1], the authors proposed an opportunistic multi-channel Aloha in which the transmission probability is adapted based on the channel state information in each sub-channel. The objective here is to exploit the multi-user diversity in a distributed manner and compare it to the centralized sub-channel allocation.…”

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confidence: 99%

Delay Analysis of OFDMA-Aloha

Mutairi

Roy

Hwang

2013

IEEE Trans. Wireless Commun.

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Abstract-OFDMA is the basis of future broadband access, due to its many inherent advantages such as scalability and fine granularity for multi-user access. OFDMA-Aloha combines the flexibility of OFDMA with basic Aloha's collision resolution mechanism over sub-carriers, in an attempt to reduce packet collisions and achieve faster retransmission. However, this comes at the expense of a larger slot size, due to lower channel rates per subcarrier. The above gives rise to a fundamental question: whether to use a single wide-band Aloha channel and retransmit via random back-off in next K time slots, or to retransmit immediately in one of K narrow-band sub-channels which are each 1/K slower (OFDMA-Aloha)? We answer this question, by analyzing the two protocols: Aloha and OFDMA-Aloha under the same total bandwidth and load conditions. We first derive the exact distribution of the packet access delay of OFDMAAloha in the saturated case. Then, we extend the analysis to the unsaturated case and derive the mean queue length and packet delay by decomposing the system of interfering queues into multiple independent queues utilizing the symmetry in our system. Our results show that if the network is already saturated, channelization does not bring substantial reduction in the collision rate to the point where it outweighs the effect of expanded slot size. In this case the single channel Aloha performs better than OFDMA-Aloha especially when the gap between the number of channels and the number users is large. On other hand, when the network is lightly loaded, OFDMA-Aloha enjoys smaller packet delays, but not for long as it saturates faster than the single channel Aloha.

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Machine Learning for Spectrum Access and Sharing

Cohen

2019

Machine Learning for Future Wireless Communications

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Opportunistic Multichannel Aloha: Distributed Multiaccess Control Scheme for OFDMA Wireless Networks

Cited by 44 publications

References 13 publications

Opportunistic Random-Access Scheme Design for OFDMA-Based Indoor PLC Networks

Opportunistic Random-Access Scheme Design for OFDMA-Based Indoor PLC Networks

Delay Analysis of OFDMA-Aloha

Machine Learning for Spectrum Access and Sharing

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