Machine to machine (M2M) communication has raised significant interests. However, due to the massive number of machine type communication (MTC) devices that are anticipated to communicate using cellular networks, there is a major problem on efficient accommodation of the heavy Random Access (RA) loads from the MTC devices. Use of small cells has been specified to provide network densification by 3GPP. In this paper we investigate the use of small cells to support RA and the allocation of Zadoff-Chu sequences to the small cells, which are used to generate preambles for the RA procedure. Small cells can be deployed on demand to handle mainly RA loads from MTC devices, which may generate much less data traffic compared to human devices. It is demonstrated that, with small cell support, more random channel access opportunities are provided and this can effectively support a massive number of machine devices. Using both simulations and analytical model the proposed implementation is evaluated and compared to two existing random access schemes without small cell support (the basic random access scheme and the access class barring (ACB) scheme). It is observed that the capacity of the networks in terms of the number of supported machine devices with small cell support can be increased significantly. The proposed implementation shows large potential to handle random channel access for massive machine devices.
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