Design and Implementation of a LTE-WiFi Aggregation System based on SDR

With explosive growth of the mobile Internet access and the popularization of wireless local area network (WLAN) access points (APs), wireless fidelity (WiFi) offloading is considered as an important supplementary technique to reduce the load of cellular infrastructure and enhance quality of network service. In this paper, we design and implement the framework of LTEWiFi aggregation (LWA) which is in line with the 3rd Generation Partnership Project (3GPP) released standard recently. In the LWA system, the process of data offloading is different from that of WiFi interworking on the cellular core network. WLAN APs directly connect to eNodeBs (eNBs), and the offloading is realized in Packet Data Convergence Protocol layer (PDCP). Thus, this architecture makes full use of existed WLAN APs to improve the performance of indoor cellular network. Besides, benefiting from the flow control between LTE and WiFi, eNB schedule can be more flexible and efficient. Next, it is implemented based on open source OpenAirInterface (OAI) software defined radio (SDR) platform, where a simple and practical reordering method is proposed and carried out. Experimental results demonstrate that our design works stably with the WiFi-offloading and reordering functions.