Effective Capacity Based Wi-Fi Delayed Offloading and Resource Re-Allocation in Heterogeneous Networks

In order to support the booming capacity requirements of the fifth generation mobile system (5G), worldwide mobile operators are increasingly interested in offloading the cellular network traffics to Wi-Fi Access Points (APs) or small cells. Addressing on the offloading problem for delay-tolerant traffic, this paper proposes Wi-Fi delayed offloading strategy and resource re-allocation in Heterogeneous Networks to improve the system energy efficiency. We introduce the effective capacity as a metric to convert the delay that the users can tolerate into the metric of data rate. Then we model the user Quality of Service (QoS) requirements as the data arrival rate and delay factor. Based on above modeling, we divide the delayed offloading process into two steps. Firstly, we adopt the k-means algorithm to cluster the user with relatively lower service quality in cellular network as Wi-Fi user, whom will be offloaded to Wi-Fi to improve the system energy efficiency. Secondly, since some resource in the cellular network will become unoccupied after Wi-Fi offloading, the resource re-allocation procedure is necessary. We model the re-allocation after Wi-Fi offloading in the cellular network as the 0-1 knapsack problem and adopt the Dynamic Programming to solve the problem for further improving the system energy efficiency. Simulation results evaluate the twos-tep improvements of system energy efficiency achieved by Wi-Fi offloading and resource re-allocation, which proves the benefits of delayed offloading in heterogeneous networks.