Co-existence of Wi-Fi and Cellular Networks

Due to the increasing number of more powerful user equipment (UE) and more appealing user applications, wireless networks have been witnessing and will continue to see an explosive traffic growth in the years to come. Indeed, recent forecasts indicate that mobile network operators will need to enhance their network capacity by a factor of 100x in order to meet their customer demands by 2020. In this context, the inter-working between Long Term Evolution (LTE) and Wireless Fidelity (Wi-Fi) networks has gained a lot of attention during the last years. LTE can leverage licensed carriers to realize

Motivation

In this context, the inter-working between Long Term Evolution (LTE) and Wireless Fidelity (Wi-Fi) networks has gained a lot of attention during the last years. LTE can leverage licensed carriers to realize quality of service and act as a mean of controlling ad-hoc Wi-Fi deployments, while Wi-Fi itself can allow operators to cost-effectively densify their networks and gain access to a large bandwidth in the unlicensed spectrum. The efficient integration of both technologies represents a good opportunity to improve the overall spectral efficiency of future wireless systems and realize effective traffic offloading/ aggregation between them both.

Standardization

In order to realize this efficient LTE and Wi-Fi integration, a Third Generation Partnership Project (3GPP) Release 13 standard, named LTE Wi-Fi Radio Level Integration with IPsec Tunnel (LWIP), is gaining much momentum within the industry. The foundation for LWIP R13 is Wi- Fi Boost which realized the first internet protocol (IP) layer LTE and Wi-Fi integration. For LTE and Wi- Fi anchored applications, Wi-Fi Boost allows uplink (UL) on cellular and downlink (DL) on Wi-Fi, so that UEs can seamlessly and simultaneously draw on the strengths of both networks.

Wi-Fi is already commonplace in enterprises today, but it is not enough and it is not perfect. Moreover, Wi-Fi is limited in scalability and quality, and security issues still persist. In particular, IT managers are concerned about UL interference problems, poor range and unfair service quality, which is granted simply on the proximity of one UE to the access point (AP) compared to another, the so-called capture effect. Looking more closely at Wi-Fi’s limitations, several problems can be traced to the sharing mechanism between the UL and the DL, i.e. Wi-Fi’s carrier sense multiple access/collision avoidance (CSMA/CA), as well as the contention between the UE uplinks. In contrast, an LTE-based system does not have this problem of UL conflicts because it uses centralized scheduled access mechanisms.

Our Approach

Wi-Fi Boost and now its standardized version LWIP R13, are game changers in the industry.

Traditional network architecture

Boost network architecture

• They open the door to position small cells into the enterprise market. They can also enable new partnerships between LTE operators and Wi-Fi providers, especially in environments such as large enterprises and outdoor public Wi-Fi, where hundreds of Wi-Fi APs are already deployed and where several additional years of service are expected.
• These solutions have been tested for LTE UL but are designed in principle to work on 3G as well. With 5G not far away in some markets, Wi-Fi Boost and LWIP R13 offers a path towards 4G-5G inter-working and in fact multi-technology inter-working.
• 3GPP standardization of LWIP R13 has been supported by major UE vendors, and will drive the UE ecosystem. The loose integration between LTE and Wi-Fi paths at the IP layer simplifies the device implementation and can potentially be delivered as a software upgrade in existing LTE small cell BSs, as mentioned before.
• Wi-Fi Boost and LWIP R13 technologies are thus the foundation for realizing the ‘all-wireless enterprise’ vision and represent a significant step forward towards the 5G.