Multichannel random access in OFDMA wireless networks

Young-June,; Park, Suho; Bahk, Saewoong

doi:10.1109/jsac.2005.862422

Cited by 158 publications

(112 citation statements)

References 15 publications

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“…In all cases, the mean service time beyond Aloha's saturation line converges to a constant which equals the mean access delay that was derived in the saturated case, see (2) for Aloha and (4) for OFDMA-Aloha as shown by the solid horizontal lines in Fig 11. Therefore, the behavior of the two MAC protocols in the unsaturated case is exactly opposite to that of the saturated case. This confirms our earlier reasoning that the reduction in the collision rate in OFDMA-Aloha has to be significant enough to overcome the effect of the expanded time scale.…”

Section: E Numerical and Simulation Resultsmentioning

confidence: 53%

“…The objective here is to exploit the multi-user diversity in a distributed manner and compare it to the centralized sub-channel allocation. OFDMAAloha was proposed in [2] as a direct extension of the singlechannel Aloha, where instead of waiting for a random backoff period when a collision occurs in one sub-channel, the node tries another (randomly selected) sub-channel immediately subject to a maximum retry limit. Recently [3] extended the basic idea of [2] to CSMA/CA systems.…”

mentioning

confidence: 99%

“…OFDMAAloha was proposed in [2] as a direct extension of the singlechannel Aloha, where instead of waiting for a random backoff period when a collision occurs in one sub-channel, the node tries another (randomly selected) sub-channel immediately subject to a maximum retry limit. Recently [3] extended the basic idea of [2] to CSMA/CA systems. In OFDMA CSMA/CA, a node first senses all sub-channels, randomly selects one sub-channel from the set of idle sub-channels and then backoffs for a random Collision Avoidance (CA) period in a way similar to the standard procedure in IEEE 802.11.…”

mentioning

confidence: 99%

“…The idea of OFDMA-Aloha was originally proposed in [2] as a fast-retrial algorithm which is explained in detail in Section I-A. The authors assumed a finite network with N users and approximated all new arrivals plus fast-retransmissions from frequency-and time-domain retransmissions by an aggregate Poisson model.…”

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confidence: 99%

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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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Section: E Numerical and Simulation Resultsmentioning

confidence: 53%

mentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Delay Analysis of OFDMA-Aloha

Mutairi

Roy

Hwang

2013

IEEE Trans. Wireless Commun.

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“…In [4], a new random access algorithm was proposed and analyzed, where a fast retrial algorithm is imposed upon the MSs to choose a random OFDMA sub-channel immediately for data retransmission instead of adopting time back-off for the first few collisions. Thereafter, if the retransmission number increases beyond some predefined threshold (retransmission threshold M) the MS starts backing of in time.…”

Section: B Related Workmentioning

confidence: 99%

Improved random channel access for OFDMA wireless networks

Das

Lannoo

Colle

et al. 2011

2011 IEEE Wireless Communications and Networking Conference

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Abstract-In this paper we propose a new random channel access protocol to reduce the channel access delay in a multichannel orthogonal frequency division multiple access (OFDMA) wireless networks. In particular, we propose a two dimensional random walk through time and frequency domain slots simultaneously to reduce the random channel access delay for the IEEE 802.16e-2005 based WiMAX media access control (MAC) protocol. We prove through simulation that our proposed scheme improves upon the existing random channel access mechanism with truncated binary back-off, currently implemented in WiMAX. We demonstrated that with our proposed channel access mechanism, a mobile node with real time traffic requirements will have minimum service disruption due to the reduced delay in the initial ranging and the bandwidth request phase while changing rooms.

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Multichannel random access in OFDMA wireless networks

Cited by 158 publications

References 15 publications

Delay Analysis of OFDMA-Aloha

Delay Analysis of OFDMA-Aloha

Improved random channel access for OFDMA wireless networks

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