to improve its signal-to-noise ratio (SNR). A flexible frequency division multiple access (FDMA) technique is utilized to achieve the inter-slice and intra-slice interference isolation [@tang2019service].

The system time is discretized and partitioned into time slots and minislots with a time slot consisting of $T$ minislots. On the one hand, at the beginning of each time slot, a RAN slicing coordinator [@How2019yang] will decide whether to accept or reject received network slice requests which will be defined in the following subsections. Once a slice request is accepted, a network slice management will be responsible for activating or creating a virtual slice that is well resource-configured to satisfied the QoS requirements of devices in the slice [@How2019yang]. The slice configuration process is time costly and will generally be conducted in a timescale of minutes to hours [@tang2019service]. On the other hand, at the beginning of each minislot, each active IoT device may try to connect to its associated RRH, and RRHs will generate cooperated beamformers based on sensed channel coefficients.

mIoT slice model
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By referring to the concept of a network slice [@rost2017network], especially from the viewpoint of the QoS requirement of a slice, we can define a mIoT slice request 