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In this paper, we propose an analytical model for dimensioning of Orthogonal Frequency Division Multiple Access (OFDMA) systems in 5G networks by considering Internet of Thing (IoT) application using stochastic geometry. In these systems, some communication is lost when the number of required subcarriers is greater than the number of available subcarriers. We compute the upper bound of the lost communication probability for downlink. In such a system, the position of receiving users is modeled by the Poisson point process. The number of subcarriers dedicated to each user depends on its Signal to Noise Ratio (SNR), position and the shadowing, hence for calculating the number of subcarriers, it is needed to use stochastic geometry. Multigroup user system with each group of users having its own application and throughput requirement is considered. For having dimensioning in terms of subcarriers, we present concentration inequality for functions defined on the Poisson point processes to calculate the upper bound of loss probability. The performance of the upper bound in different ranae of user intensity is investiaated.

A Low complex interference cancellation via modified suboptimum search algorithm in conjunction with a primary stage of reduced rank linear (RRL) multiuser detector for the mobile uplink is proposed. Initial stage is improved through mathematical analysis via Gershgorin algorithm in linear algebra and RRLG detector is introduced. The complexity of the initial stage is evaluated and compared to the recently reported low-complex Fourier interference cancellation method. Depending on the value of the spreading factor of the active users in system, RRLG outperforms the Fourier algorithm, in terms of complexity. The structure of the RRLG method and the suboptimum search algorithm are well suited together and makes them collaboratively work without encountering a high level of complexity. Considering the power profile of the users in the suboptimum search algorithm leaded to even less complexity, yet keeping the performance almost the same. The performance of the structure is obtained via simulations and has been compared to partial parallel interference cancellation (PPIC) method. A good improvement in performance in the low SNR regions, which is difficult to achieve by conventional multiuser detectors and also important as the actual systems are likely to operate in these regions, has been achieved. All the techniques and their modifications introduced in this work consider the complexity as an important issue that enables them suitable for industry and implementation purposes. Another important feature is that the techniques perform on canonical matrix formulations of the system so they can be applied to MC-CDMA and MIMO systems, as well.

A suboptimum search algorithm to suppress the interference level in conjunction with a primary stage of iterative linear multiuser detector for the mobile uplink is proposed. The initial stage is improved through analytical analysis. The structure of the iterative method and the suboptimum search algorithm are well suited together and makes them collaboratively work without encountering a high level of complexity. Considering the power profile of the users in the suboptimum search algorithm leaded to even less complexity, yet keeping the performance almost the same. The performance of the structure is obtained by simulations and has been compared to parallel interference cancellation method.