Small-Cell Traffic Balancing Over Licensed and Unlicensed Bands

The Third-Generation Partnership Project (3GPP) has recently started standardizing the "licensed-assisted access using LTE" for small cells, which is referred to as dual-band femtocell (DBF) in this paper, which uses the Long-Term-Evolution (LTE) air interface in both the licensed and unlicensed bands based on the LTE carrier aggregation feature. Alternatively, the Small Cell Forum introduced the integrated femto-WiFi (IFW) small cell, which simultaneously accesses both the licensed band (via cellular interface) and the unlicensed band (via WiFi interface). In this paper, a practical algorithm for IFW and DBF to automatically balance their traffic in licensed and unlicensed bands, based on the real-time channel, interference, and traffic conditions of both bands, is described. The algorithm considers the fact that some "smart" devices (sDevices) have both cellular and WiFi radios, while some WiFi-only devices (wDevices) may only have WiFi radio. In addition, the algorithm considers a realistic scenario where a single small-cell user may simultaneously use multiple sDevices and wDevices via either the IFW or the DBF in conjunction with a wireless local area network. The goal is to maximize the total user satisfaction/utility of the small-cell user, while keeping the interference from small cells to macrocells below predefined thresholds. The algorithm can be implemented at the radio link control or the network layer of the IFW and DBF small-cell base stations. Results demonstrate that the proposed traffic-balancing algorithm applied to either IFW or DBF significantly increases the sum utility of all macrocell and small-cell users, compared with the current practices. Finally, various implementation issues of IFW and DBF are addressed.