The Experts below are selected from a list of 4401 Experts worldwide ranked by ideXlab platform
Gianluigi Liva - One of the best experts on this subject based on the ideXlab platform.
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finite length analysis of irregular repetition Slotted Aloha in the waterfall region
IEEE Communications Letters, 2018Co-Authors: Alexandre Graell I Amat, Gianluigi LivaAbstract:A finite-length analysis is introduced for irregular repetition Slotted Aloha (IRSA) that enables to accurately estimate its performance in the moderate-to-high packet loss probability regime, i.e., in the so-called waterfall region. The analysis is tailored to the collision channel model, which enables mapping the description of the successive interference cancellation process onto the iterative erasure decoding of low-density parity-check codes. The analysis provides accurate estimates of the packet loss probability of IRSA in the waterfall region as demonstrated by Monte Carlo simulations.
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asymptotic performance of coded Slotted Aloha with multipacket reception
IEEE Communications Letters, 2018Co-Authors: Cedomir Stefanovic, Enrico Paolini, Gianluigi LivaAbstract:In this letter, we develop a converse bound on the asymptotic load threshold of coded Slotted Aloha (CSA) schemes with $K$ -multipacket reception capabilities at the receiver. Density evolution is used to track the average probability of packet segment loss and an area matching condition is applied to obtain the converse. For any given CSA rate, the converse normalized to $K$ increases with $K$ , which is in contrast with the results obtained so far for Slotted Aloha schemes based on successive interference cancellation. We show how the derived bound can be approached using spatially coupled CSA.
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coded Slotted Aloha a graph based method for uncoordinated multiple access
IEEE Transactions on Information Theory, 2015Co-Authors: Enrico Paolini, Gianluigi Liva, Marco ChianiAbstract:In this paper, a random access scheme is introduced, which relies on the combination of packet erasure correcting codes and successive interference cancellation (SIC). The scheme is named coded Slotted Aloha. A bipartite graph representation of the SIC process, resembling iterative decoding of generalized low-density parity-check codes over the erasure channel, is exploited to optimize the selection probabilities of the component erasure correcting codes through a density evolution analysis. The capacity (in packets per slot) of the scheme is then analyzed in the context of the collision channel without feedback. Moreover, a capacity bound is developed, and component code distributions tightly approaching the bound are derived.
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the throughput of Slotted Aloha with diversity
arXiv: Networking and Internet Architecture, 2014Co-Authors: Andrea Munari, Gianluigi Liva, Michael Heindlmaier, Matteo BerioliAbstract:In this paper, a simple variation of classical Slotted Aloha is introduced and analyzed. The enhancement relies on adding multiple receivers that gather different observations of the packets transmitted by a user population in one slot. For each observation, the packets transmitted in one slot are assumed to be subject to independent on-off fading, so that each of them is either completely faded, and then does not bring any power or interference at the receiver, or it arrives unfaded, and then may or may not, collide with other unfaded transmissions. With this model, a novel type of diversity is introduced to the conventional SA scheme, leading to relevant throughput gains already for moderate number of receivers. The analytical framework that we introduce allows to derive closed-form expression of both throughput and packet loss rate an arbitrary number of receivers, providing interesting hints on the key trade-offs that characterize the system. We then focus on the problem of having receivers forward the full set of collected packets to a final gateway using the minimum possible amount of resources, i.e., avoiding delivery of duplicate packets, without allowing any exchange of information among them. We derive what is the minimum amount of resources needed and propose a scheme based on random linear network coding that achieves asymptotically this bound without the need for the receivers to coordinate among them.
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high throughput random access via codes on graphs coded Slotted Aloha
arXiv: Information Theory, 2011Co-Authors: Enrico Paolini, Gianluigi Liva, Marco ChianiAbstract:In this paper, coded Slotted Aloha (CSA) is introduced as a powerful random access scheme to the MAC frame. In CSA, the burst a generic user wishes to transmit in the MAC frame is first split into segments, and these segments are then encoded through a local a packet-oriented code prior to transmission. On the receiver side, iterative interference cancellation combined with decoding of the local code is performed to recover from collisions. The new scheme generalizes the previously proposed irregular repetition Slotted Aloha (IRSA) technique, based on a simple repetition of the users' bursts. An interpretation of the CSA interference cancellation process as an iterative erasure decoding process over a sparse bipartite graph is identified, and the corresponding density evolution equations derived. Based on these equations, asymptotically optimal CSA schemes are designed for several rates and their performance for a finite number of users investigated through simulation and compared to IRSA competitors. Throughputs as high as 0.8 are demonstrated. The new scheme turns out to be a good candidate in contexts where power efficiency is required.
Akira Ogawa - One of the best experts on this subject based on the ideXlab platform.
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a novel spread Slotted Aloha system with channel load sensing protocol
IEEE Journal on Selected Areas in Communications, 1994Co-Authors: K Toshimitsu, Takaya Yamazato, Masaaki Katayama, Akira OgawaAbstract:This paper presents a novel spread Slotted Aloha system with channel load sensing protocol (CLSP). CLSP is an effective scheme to improve the throughput performance in spread unSlotted Aloha systems. In spread Slotted Aloha systems, however, it does not make sense to utilize CLSP because the slot size is usually the same as the packet size. The slot size of the proposed system is set less than the packet size, thereby enabling the authors to apply CLSP and improving the throughput performance. Another feature of the proposed system is that the system is not likely affected by the time difference between channel load sensing and timing of packet access, which they call the access timing delay. Throughput performance of the proposed system is evaluated in the presence of the access timing delay and a significant increase of the throughput is shown compared with that of spread unSlotted Aloha with CLSP. >
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a novel spread Slotted Aloha system with channel load sensing protocol
MILCOM '93, 1994Co-Authors: K Toshimitsu, Takaya Yamazato, Masaaki Katayama, Akira OgawaAbstract:This paper presents a noval spread Slotted Aloha system with channel load sensing protocol (CLSP). CLSP is an effective scheme to improve the throughput performance in spread unSlotted Aloha systems. In spread Slotted Aloha systems, however, it does not make sense to utilize CLSP because the slot size is usually the same as the packet size. The slot size of the proposed system is set less than the packet size, thereby enabling us to apply CLSP and improving the throughput performance. Another feature of the proposed system is that the system is not likely affected by the time difference between channel load sensing and timing of packet access, which we call the access timing delay. Throughput performance of the proposed system is evaluated in the presence of the access timing delay and a significant increase of the throughput is shown compared with that of spread inSlotted Aloha with CLSP
R T Compton - One of the best experts on this subject based on the ideXlab platform.
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high throughput Slotted Aloha packet radio networks with adaptive arrays
IEEE Transactions on Communications, 1993Co-Authors: J Ward, R T ComptonAbstract:The authors consider the use of a multiple-beam adaptive array (MBAA) in a packet radio system. In an MBAA, a given set of antenna elements is used to form several antenna patterns simultaneously. When it is used in a packet radio system, an MBAA can successfully receive two or more overlapping packets at the same time. Each beam captures a different packet by automatically pointing its pattern toward one packet while nulling other, contending packets. It is shown how an MBAA can be integrated into a single-hop Slotted Aloha packet radio system, and the resulting throughput is analyzed for both finite- and infinite-user populations. >
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improving the performance of a Slotted Aloha packet radio network with an adaptive array
IEEE Transactions on Communications, 1992Co-Authors: J Ward, R T ComptonAbstract:The use of an adaptive antenna array as a means of improving the performance of a Slotted Aloha packet radio network is presented. An adaptive array creates a strong capture effect at a packet radio terminal by automatically steering the receiver antenna pattern toward one packet and nulling other contending packets in a slot. A special code preamble and randomized arrival times within each slot allow the adaptive array to lock onto one packet in each slot. The throughput and delay performance of a network with an adaptive array are computed by applying the standard Markov chain analysis of Slotted Aloha. It is shown that throughput levels comparable to carrier sense multiple access (CSMA) are attainable with an adaptive array without the need for stations to be able to hear each other. The performance depends primarily on the number of adaptive array nulls, the array resolution, and the length of the randomization interval within each slot. >
Pantelisdaniel Arapoglou - One of the best experts on this subject based on the ideXlab platform.
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enhancing the physical layer of contention resolution diversity Slotted Aloha
IEEE Transactions on Communications, 2017Co-Authors: Alberto Mengali, Riccardo De Gaudenzi, Pantelisdaniel ArapoglouAbstract:There is an urgent need for substantially enhancing random access schemes to be able to support native massive machine-to-machine communications in the next generation wireless systems. Lately, contention resolution diversity Slotted Aloha (CRDSA) and its variants have contributed to a drastic improvement in throughput compared with the traditional Slotted Aloha protocols. In this paper, we further enhance the CRDSA flexibility and performance along different physical layer dimensions. Based on simulation results, we show that there is still room for improvement in terms of throughput and, using heuristic methods, we find an optimized distribution of the packets power that is entering the demodulator for an additive white Gaussian noise channel. Applying this power distribution, which is easy to implement at the terminal in open loop and in a decentralized manner, is shown to achieve significantly enhanced performance. By introducing multi-frequency CRDSA, a drastic reduction in the terminal’s peak power requirement is attained. Furthermore, we investigate spread spectrum CRDSA, which improves the robustness of the scheme against irresolvable packet collisions allowing for enhanced energy efficiency. To support the work presented herein, we have developed a computationally efficient yet accurate methodology for estimating CRDSA performance, a novel approximate centrally coordinated CRDSA achievable sum rate analysis accounting for modulation and forward error correction constraints, as well as a more accurate loop probability analysis.
Wuyi Yue - One of the best experts on this subject based on the ideXlab platform.
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the effect of capture on performance of multichannel Slotted Aloha systems
IEEE Transactions on Communications, 1991Co-Authors: Wuyi YueAbstract:The author presents an exact analysis to evaluate the effect of capture on the multichannel Slotted Aloha protocol. The author derives the probabilities of the successful transmission. These probabilities are used to calculate the throughputs, average packet delays for both IFT (immediate-first-transmission) and delayed-first-transmission protocols and numerically compare the performance of the systems with and without capture. Numerical results show that when a quantitative capture restriction u is considered, in a multichannel system having a fixed total bandwidth, depending on parameter u and channel number M, an improved system performance such as the average channel utilization and average packet delay can be obtained. >
