Unlicensed LTE: good luck with that

22 Apr 2014

Unlicensed LTE (uLTE) has been put under the spotlight since it was proposed by Qualcomm in November 2013. The uLTE solution uses the radio carrier aggregation of LTE-Advanced to allow licensed radio spectrum technologies to aggregate carriers that operate in unlicensed bands. From a technical perspective, the solution is elegant in its simplicity. However, uLTE needs more than technical elegance for mass market success and depends on a variety of factors including support by the 3GPP, equipment vendors and service providers.

Since it is still in its infancy, most industry players are adopting a “wait and see” approach to the efficacy of uLTE, while others are using it to rekindle the age-old battleground between licensed and unlicensed radio spectrum technologies. While this battleground has seen both sides aggressively defend their territories with elaborate technical dissertations, the insurgence of unlicensed Wi-Fi into the licensed spectrum world is a clear indication of how market forces always win.

Although it is impossible to reliably forecast uLTE adoption, there are a variety of clear market drivers and interdependencies that will impact its success. At Tolaga Research we use system modelling techniques to evaluate the market drivers and interdependencies for new technologies like uLTE. These system models are used to simulate and assess the impact of different scenarios. A high-level schematic of the modelling approach for uLTE is illustrated in Figure 1 and accounts for the dynamics and interdependencies between the small-cell, carrier grade Wi-Fi and u-LTE markets. In particular:

  • Since uLTE is a local area wireless technology, it will be deployed solely in small-cells. The mobile industry has made tremendous progress in developing small-cell technology, but its adoption is still constrained by the need for low-cost automated operational processes and procedures. (See Outlook 2014: the big case for small-cells.) These automated processes span facets of network planning, design, implementation, optimization and ongoing operations, and are necessary for small-cell deployments to scale economically. Furthermore, automation might present opportunities for uLTE to be incorporated as a standard optimization feature that is enabled automatically.
  • Since Wi-Fi is pervasive among smartphone devices and in enterprise, residential and public environments, it has been widely used as a traffic offload technology by mobile service providers. Some service providers are deploying their own carrier-grade Wi-Fi equipment, while others are relying on aggregators like Boingo and DeviceScape. Service providers that are embracing carrier-grade Wi-Fi are encouraging their vendor suppliers to embed Wi-Fi in their small-cell solutions and are provisioning device functionality to improve overall service functionality. Standards such as ANDSF (Access Network Discovery and Selection Function), Hotspot 2.0 and other proprietary solutions aim to increase the continuity of Wi-Fi services, when integrated in mobile environments. Service providers that have embraced carrier grade Wi-Fi are less likely to support uLTE. However, their efforts to enable unlicensed spectrum ecosystems for Wi-Fi are likely to have the effect of reducing incremental integration costs for uLTE.
  • LTE-Advanced based carrier aggregation is required for uLTE. Carrier aggregation has already been adopted by some service providers and will gain market momentum over the next 24 months, particularly among those service providers with fragmented radio spectrum allocations.
  • Since the LTE has been developed for licensed spectrum allocations, it does not conform to the regulatory requirements for unlicensed services in markets outside of the US, Korea and China. In particular, uLTE requires that “Listen-before-Talk” functionality be included as part of the 3GPP standards. Qualcomm and other advocates for u-LTE are lobbying for the incorporation of the “Listen-before-Talk” functionality in 3GPP Release 13. Until this functionality is included in the standards, uLTE will be nothing more than an interesting concept.

It will take many years before the prospects for uLTE can be reliably evaluated and its success depends on several key factors to align its favor. Of particular importance is the support of device and small-cell equipment vendors, wide-scale small-cell adoption and the appropriate positioning with Wi-Fi and other systems that operate in unlicensed spectrum.

Figure 1: Market interdependencies impact uLTE adoption

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