  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.
