# Radio Resource Dimensioning for Low Delay Access in Licensed OFDMA IoT Networks +
## 1 Introduction  
Cellular licensed IoT technology has been an emerging and evolving Low Power Wide Area (LPWA) technology which provides long range, low power and low cost connectivity for IoT devices [1]. It can be deployed in existing cellular networks from which it inherits many of the features that determine its behavior [2], such as Long Term Evolution (LTE) networks. With the booming development of Fifth Generation (5G) technology, evolutions of cellular IoT standards have been proposed and put into practice by 3 rd Generation Partnership Project (3 GPP) [3]. It will further promote the development of IoT technology. 5G technologies primarily include non-standalone and standalone technologies. The former is the early-drop technology that operators plan to connect new radio 5G base stations to the Fourth Generation (4G) core network until 5G connectivity migratesto the native 5G Core network mode which means shifts to standalone mode [4]. For the 4G and nonstandalone 5G connections, Orthogonal Frequency Division Multiple Access (OFDMA) technology can be employed to enable multi-carrier transmission and network access. OFDMA can take advantage of multiuser diversity and robustness to multipath fading for the uplink communications. Moreover, it provides more degrees of freedom for resource allocation and facilitates multiplexing and diversity gains [5; 6]. Due to the limited spectrum of licensed IoT, as the network gradually scales up, one of the key issues we face is how to effectively use these resources to support large-scale IoT devices. In addition, the cost of IoT has been a major concern, and the improvement of spectrum efficiency can help reduce the cost of cellular IoT networks. In this paper, we focus on the uplink of OFDMA-based cellular IoT networks with multiple antennas receiver. The average statistical behavior of the network is considered where the active sensors and collectors are randomly distributed in a given area according to a random Poisson Point Process (PPP). The randomness of the wireless channel is considered as a mark of the Poisson position and results from stochastic geometry using marked PPP as in [7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19] will be invoked. These tools were investigated in [20; 21; 22; 23] to compute an upper-bound on the resource outage probability in a cellular network considering random PPP marked by the random fading. Unlike the previous contributions in [20; 21; 22; 23] where the network is considered as noise limited, this study is more general as it takes into account the impact of interference on the statistical dimensioning. In [24], our dimensioning model is restricted to the single user case with multiple antennas receivers, in which only the receiver diversity, namely, the antenna selection technique, is performed without exploiting the spatial multiplexing gain. This paper generalizes our previous contribution in [24] by considering MU-MIMO schemes where multiple users can be scheduled over one RR. It introduces indeed a new criterion for performing dimensioning based upon low delay access. We also provide a comparison between the energy consumption of the different considered transmission modes. We consider first single-user (SU) communication with receiver diversity transmission modes such as antenna selection considered in [24] and the Maximum Ratio Combining (MRC). Next, we consider multiuser (MU) transmission where a distance-based scheduling algorithm is proposed with neighboring sensors nodes that are scheduled on the same RR. The interuser interferences are canceled using a Zero-Forcing decoder. The remaining diversity when not all the degrees of freedom are consumed is extracted using a MRC. The number of RR required by a single node in the SU case of by a group of nodes in the MU case is limited by the lowest Modulation and Coding Scheme (MCS). We define the network outage as the event that occurs when the number of request RRs exceed the number of the available ones.