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- Sandgren, Erik, 1992, et al.
(author)
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Asymptotic and Finite Frame Length Analysis of Frame Asynchronous Coded Slotted ALOHA
- 2016
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In: International Symposium on Turbo Codes and Iterative Information Processing, ISTC. - 2165-4700 .- 2165-4719. - 9781509034017 ; 2016-October, s. 81-85
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Conference paper (peer-reviewed)abstract
- We consider a frame-asynchronous coded slotted ALOHA (FA-CSA) system where users join according to a Pois- son random process. In contrast to standard frame-synchronous CSA (FS-CSA), when a user joins the system, it transmits a first replica of its message in the following slot and other replicas uniformly at random in a number of subsequent slots. We derive the (approximate) density evolution that characterizes the asymptotic performance of FA-CSA when the frame length goes to infinity. We show that, if the receiver can monitor the system before users start transmitting, a boundary effect similar to that of spatially-coupled codes occurs, which greatly improves the decoding threshold as compared to FS-CSA. We also derive analytical approximations of the error floor (EF) in the finite frame length regime. We show that FA-CSA yields in general lower EF, better performance in the waterfall region, and lower average delay, as compared to FS-CSA.
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| 2. |
- Sandgren, Erik, 1992, et al.
(author)
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On Frame Asynchronous Coded Slotted ALOHA: Asymptotic, Finite Length, and Delay Analysis
- 2017
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In: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 65:2, s. 691-704
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Journal article (peer-reviewed)abstract
- We consider a frame asynchronous coded slotted ALOHA (FA-CSA) system for uncoordinated multiple access, where users join the system on a slot-by-slot basis according to a Poisson random process and, in contrast to standard frame synchronous CSA (FS-CSA), users are not frame-synchronized. We analyze the performance of FA-CSA in terms of packet loss rate and delay. In particular, we derive the (approximate) density evolution that characterizes the asymptotic performance of FACSA when the frame length goes to infinity. We show that, if the receiver can monitor the system before anyone starts transmitting, a boundary effect similar to that of spatially-coupled codes occurs, which greatly improves the iterative decoding threshold. Furthermore, we derive tight approximations of the error floor (EF) for the finite frame length regime, based on the probability of occurrence of the most frequent stopping sets. We show that, in general, FA-CSA provides better performance in both the EF and waterfall regions as compared to FS-CSA. Moreover, FACSA exhibits better delay properties than FS-CSA.
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