ATractableModeloftheLTE方案.PDFVIP

A Tractable Model of the LTE Access Reservation Procedure for Machine-Type Communications ´ ˜ Jimmy J. Nielsen, Dong Min Kim, German C. Madueno, Nuno K. Pratas, Petar Popovski APNET section, Department of Electronic Systems, Aalborg University, Denmark jjn,dmk,gco,nup,petarp @es.aau.dk Abstract—A canonical scenario in Machine-Type Communica- 1 MSG1 - Preamble tions (MTC) is the one featuring a large number of devices, each of them with sporadic traffic. Hence, the number of served devices MSG2 - Random Access Response 2 5 in a single LTE cell is not determined by the available aggregate 1 rate, but rather by the limitations of the LTE access reservation Device 3 MSG3 - Connection Request eNodeB protocol. Specifically, the limited number of contention preambles 0 MSG4 - Contention Resolution 4 2 and the limited amount of uplink grants per random access re- sponse are crucial to consider when dimensioning LTE networks Fig. 1. Message exchange between a device and the eNodeB during the LTE v for MTC. We propose a low-complexity model of LTE’s access random access procedure. o reservation protocol that encompasses these two limitations and N allows us to evaluate the outage probability at click-speed. The model is based chiefly on closed-form expressions, except for 0 the part with the feedback impact of retransmissions, which a bottleneck may be caused by the limite