# A Comparative Analysis of Wi-Fi Offloading and Cooperation in Small-Cell Network
###### Abstract  
Small cells deliver cost-effective capacity and coverage enhancement in a cellular network. In this work, we present the interplay of two technologies, namely Wi-Fi offloading and small-cell cooperation that help in achieving this goal. Both these technologies are also being considered for 5G and B5G (Beyond 5G). We simultaneously consider Wi-Fi offloading and small-cell cooperation to maximize average user throughput in the small-cell network. We propose two heuristic methods, namely Sequential Cooperative Rate Enhancement (SCRE) and Sequential Offloading Rate Enhancement (SORE) to demonstrate cooperation and Wi-Fi offloading, respectively. SCRE is based on cooperative communication in which a user data rate requirement is satisfied through association with multiple small-cell base stations (SBSs). However, SORE is based on Wi-Fi offloading, in which users are offloaded to the nearest Wi-Fi Access Point and use its leftover capacity when they are unable to satisfy their rate constraint from a single SBS. Moreover, we propose an algorithm to switch between the two schemes (cooperation and Wi-Fi offloading) to ensure maximum average user throughput in the network. This is called the Switching between Cooperation and Offloading (SCO) algorithm and it switches depending upon the network conditions. We analyze these algorithms under varying requirements of rate threshold, number of resource blocks and user density in the network. The results indicate that SCRE is more beneficial for a sparse network where it also delivers relatively higher average data rates to cell-edge users. On the other hand, SORE is more advantageous in a dense network provided sufficient leftover Wi-Fi capacity is available and more users are present in the Wi-Fi coverage area. cooperative small-cell network; Wi-Fi offloading; LTE-U; heterogenous network Article  
A Comparative Analysis of Wi-Fi Offloading and Cooperation in Small-Cell Network  
[PERSON]  
Several technologies have emerged recently that involve cellular data traffic offloading to Wi-Fi; however, LTE-Unlicensed (LTE-U) and License-Assisted Access (LAA) are the most notable [1; 2]. LTE-U performs adaptive duty cycling with Carrier Sense Adaptive Transmission (CSAT), and adapts according to the Wi-Fi traffic load; however, it does not perform Listen Before Talk (LBT) [3]. LAA on the other hand does perform LBT, hence, it is considered to be better in maintaining fairness with Wi-Fi devices. Both LTE-U and LAA operate in 5 GHz band and have been standardized in 3 GPP Rel-12 and Rel-14 respectively [4]. Several studies have tried to analyze the fairness between LTE-U/LAA and Wi-Fi. The FCC report on the co-existence of LAA and Wi-Fi indicated that LAA could adversely affect throughput of Wi-Fi in an unfair manner [5]. In [6], the fairness between Wi-Fi and LTE-U/LAA was investigated and it was concluded that when configured optimally, LTE-U and LAA could provide the same level of fairness as other Wi-Fi devices. Coordinated Multipoint (CoMP) helps in improving coverage and cell-edge data rates and minimizes intercell interference through coordination between the base stations [7]. CoMP is also sometimes referred to as cooperative communication. While using CoMP, various transmission or reception points, such as SBS, relaying nodes or remote radio heads (RRH), can be coordinated to provide efficient service to the user equipment (UE). For example, data can be simultaneously transmitted in the same resource blocks from more than one SBS to a single UE, or data can be received by a UE from one SBS in one subframe and from another SBS in the next subframe [8]. Thus, CoMP enables the optimum paths for uplink and downlink traffic. CoMP has two main approaches; the first is based on interference mitigation and this includes coordinated scheduling (CS) and coordinated beamforming. The second approach is based on fusion, in which the base stations simultaneously transmit to an intended UE, and their streams are fused using joint transmission (JT) or joint processing (JP).