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<3GPP 36.899>

Licensed spectrum needs for LAA

The amount of data traffic carried over cellular networks is expected to increase for many years to come. The number of users/devices is increasing and each user/device accesses an increasing number and variety of services, e.g. video delivery. This requires not only high capacity in the network, but also provisioning very high data rates to meet customers’ expectations on interactivity and responsiveness. More spectrum is therefore needed for cellular operators to meet the increasing demand. Considering user expectations of high data rates along with seamless mobility, it is important that more spectrum be made available for deploying macro cells as well as small cells for cellular systems.

The preferred type of spectrum to efficiently serve users is licensed spectrum. Licensed spectrum can deliver predictable high-quality services with the highest spectral efficiency. In addition, in order to deliver predictable services, mobile operators perform heavy network investments, through careful planning and deployment of high-quality network equipment and devices. The justifications for such extensive capital investments require the reliability and operational assurance enabled by licensed spectrum. It is therefore essential that the regulatory community keeps focusing on identifying and allocating new licensed spectrum that can be utilized specifically for mobile communications.

Striving to meet the market demands, there has been increasing interest from operators in deploying some complementary access utilizing unlicensed spectrum to meet the traffic growth. This is exemplified by the large number of operator-deployed Wi-Fi networks and the 3GPP standardization of LTE/WLAN interworking solutions. This interest indicates that unlicensed spectrum, when present, can be an effective complement to licensed spectrum for cellular operators to help addressing the traffic explosion in some scenarios, such as hotspot areas. LAA offers an alternative for operators to make use of unlicensed spectrum while managing one radio network, thus offering new possibilities for optimizing the network’s efficiency.

However, it is clear that unlicensed spectrum can never match the quality of the licensed spectrum regime. Unlicensed spectrum can never replace the need for more licensed spectrum due to its inability to be used in macro cells providing wide-area coverage and its general inability to provide highly robust quality-of-service due to the uncontrolled interference. Therefore, unlicensed spectrum is better used as “Licensed-Assisted Access” integrated into LTE, where it is considered as a secondary component carrier in a carrier aggregation scenario.

Since the primary component carrier in licensed spectrum will be used to carry some (or all) of the control signal (and possibly also data, e.g. retransmissions) of the traffic carried over the carrier in unlicensed spectrum, the use of unlicensed spectrum also increases the need for more licensed spectrum. Such need will be most obvious in deployment scenarios such as carrier aggregation between a macro cell operating in licensed spectrum and clusters of many small cells (remote radio heads) operating only in large chunks of unlicensed spectrum, i.e. deployment scenario 1 in Section 6. Furthermore, since a standalone access to unlicensed spectrum is not part of the study, the traffic increase will have to be supported by more network access capacity in licensed bands, e.g. using more licensed spectrum.

Thus, the use of LTE in unlicensed spectrum can serve as a useful additional tool by operators to maximize the value they can provide to users, while the core of the activity of the operators remains anchored to the licensed spectrum.

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