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  1. P. Osti, P. Lassila, S. Aalto, A. Larmo and T. Tirronen, Analysis of PDCCH performance for M2M traffic in LTE, IEEE Transactions on Vehicular Technology, vol. 63, no. 9, pp. 4357-4371, 2014 (pdf)(bib)
    Abstract: As LTE is starting to get widely deployed, the volume of M2M traffic is increasing very rapidly. From the M2M traffic point of view, one of the issues to be addressed is the overload of the random access channel. The limitation in the PDCCH resources may severely constrain the number of devices that an LTE eNB can serve. We develop a Markov model that describes the evolution of the Message 4 queue in the eNB formed by several users performing the random access procedure simultaneously and then study its stability and performance. By utilizing the model, we estimate the probability of failure of the random access procedure due to different causes. We observe that the sharing of the PDCCH resources between Message 2 and Message 4 with different priorities makes the performance of the whole random access procedure deteriorate very rapidly near the stability limit. We can extend the stability limit (capacity) and improve the overall performance by increasing the PDCCH resources. However, the very rapid deterioration of performance near the stability limit cannot be avoided. Furthermore, the stability limit can be explicitly determined from our model and we apply it to estimate the upper limit of the number of devices that can be served by an LTE eNB.