A tight coupling of LTE and Wi-Fi interfaces can be achieved by integrating them at their radio protocol stacks. LTE and Wi-Fi radio level integration with IPSec tunnel (LWIP) was introduced by 3GPP as part of Rel-13. This tighter level of interworking replaces the traditional way of cellular-Wi-Fi interworking through a packet gateway and it can react to the dynamic changes in the wireless link quality. In this paper, we present a variant of LWIP prototype that works with commercial UE (Nexus 5). The developed LWIP prototype uses OpenAirInterface (OAI) for LTE network and Cisco Access Point (AP) as Wi-Fi AP. We also present the design and implementation of LWIP prototype and interesting results for tight interworking of LTE and Wi-Fi at IP level. We have evaluated the LWIP performance with different Link Aggregation Strategies (LAS) using both UDP and TCP. We have observed that, in a highly loaded Wi-Fi channel, when LWIP employs Wi-Fi only in Downlink (WoD) LAS, then sum of individual TCP flow throughput has improved by 28% as compared to LWIP operating with Flow Split (FS) LAS. We have enumerated the challenges which has to be addressed in LWIP to reap the maximum benefits. © 2017 IEEE.