# Interference Avoidance Using TDMA-Beamforming in Location Aware Small Cell Systems
## 1 Introduction
TDMA techniques usually utilise time division multiplexing (TDM) training sequences to assist at the demodulating terminal. In that regard, the authors of [20] focused on achieving better synchronisation to realise the adaptive beamforming algorithms in real time co-channel communication systems. The small cell technology on the other hand have expanded the capacity of the current communication systems by allowing more users to utilise more network resources with enhanced signals quality. Given the fact that most of future data exchange will originate from indoor environments along with the fragility of higher frequency signals; small cells are the most attractive solution that will solve for all the highlighted issues. With regards to that, service areas are often divided into equal set of squares whereby each square is served by single small cell to suppress interference power [21]. This is achieved by forcing other small cells within the service area to switch off to save power. However, interference caused by edge users transmitting with the maximum power may lead to grave performance deterioration. In [22] adaptive power control mechanism was proposed to reduce the interference by adaptively adjusting the transmission power to enhance the signal to interference plus noise ratio (SINR) and minimise the outage probability. The adaptation was done by either increasing or reducing the transmission power by a certain value and concurrently measure the SINR to achieve an optimal value. Additional works on interference management using power suppression techniques can be found in [23; 24; 25]. The authors of [26] presented a smart virtual antenna array that is deployable in 5G-IOT systems to avoid the interference by precisely directing the beams towards specific users. While transmitter signals are assumed to be in the form of generalised frequency division multiplexing (GFDM), the user signals are assumed to be OFDM signals. However, the authors of this paper understand that current wireless systems should be investigated extensively especially in views of small cells, beamforming, and TDMA technologies due to the existence of limited realistic channel models for future 5G communication systems and applications. To the best of the authors knowledge, all works on beamforming techniques in long term evolutions (LTE) communication systems utilise location aware principles in approaching the objectivesof the work. Without loss of generality, the authors have found no works that consider exploiting beamforming and TDMA techniques together to suppress the interference in dense small cell systems. Therefore, this paper proposes an interference avoidance algorithm that exploits beamforming and TDMA techniques in location aware small cell communication systems. This is achieved by redirecting the beams towards the users at different times in which the locations of the users are assumed to be known. The main contributions of this paper are summarised below:  
1. Realistic interference estimation and avoidance based on line-of-sight conditions. Therefore, favourable settings for propagation conditions are noted. 2. Effective beamforming and TDMA algorithm for interference avoidance in dense indoor environments. 3. The proposed scheme improves the network data rate in broader bandwidth transmissions. 4. Realistic network model that is suitable for future communication systems. 5. Motivation for further research directions, such as: interference avoidance in ultra-high frequencies and beamsteering techniques. The remainder of this paper is divided as follows; Section 2 describes the system modelling and problem formulation, the proposed model is described in Section 3, Section 4 presents the evaluations of the numerical results, and Section 5 concludes the paper.