Unlicensed spectrum eases small cell deployment dilemmas

Phil Marshall / Tolaga Research
02 Nov 2015

The advent of small cells and Wi-Fi challenges traditional network designs and operational models, which have been refined over several decades with a focus towards macro cellular environments and licensed spectrum technologies. In particular, small cells introduce highly distributed radio environments that require automated operations and innovative solutions to alleviate backhaul and site acquisition challenges.

This is complicated by conventional small cell designs, which are self-contained units with a relatively narrow technology focus. When deployed, many units are required for multi-operator/technology implementations, which can be challenging, particularly for outdoor deployments.

In some cases, outdoor “small cells” are deployed with distributed antenna systems (DAS) that enable multiple mobile operators to collate their base station infrastructure and share the connectivity and radio equipment using neutral host architectures. A neutral host architecture eases site acquisition requirements by consolidating the radio equipment of multiple operators, but requires high bandwidth and low latency connectivity that can be cost-prohibitive.

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LTE Insights October 2015


Consequently, mobile operators need a small cell solution that address both site-acquisition and backhaul challenges, with adequate service continuity to support heterogeneous network architectures.

In contrast to small cells that use licensed spectrum, Wi-Fi hotspots commonly provide shared radio resources to offload traffic from multiple mobile networks by using unlicensed radio spectrum. Although Wi-Fi is widely used for mobile offload, it has challenges in enabling adequate mobile service continuity. This has culminated in advancements in Wi-Fi, which include 802.11ac, ax and ah for improved coverage and capacity, 802.11ax and ah for improved outdoor performance, and 802.11ai and Hotspot 2.0 for improved public hotspot performance. It has also resulted in the development of LTE Unlicensed (LTE-U) to enable improved network performance and service integration.

Spectrum flavors

Proposed in 2013, LTE-U enjoys strong support from the mobile industry, and comes in several flavors, including LTE-U/LAA (which requires carrier aggregation with LTE-Advanced), and MuLTEFire, which was recently proposed by Qualcomm and enables LTE-U to operate independent of LTE-A.

With the ability to seamlessly combine licensed and unlicensed spectrum resources, LTE-U could provide a platform to enable enhanced neutral host architectures for small cells. To achieve this, however, it is necessary for mobile operators to share baseband and licensed spectrum resources in the local areas covered by the small cells. While the notion of baseband and radio spectrum-sharing might prove a challenging proposition for mobile operators, the impact of sharing can be mitigated by a variety of factors, which include the following:

  • Relying on unlicensed spectrum resources to reduce the bandwidth of shared licensed spectrum required
  • Capitalizing on the localized coverage requirements for small cells
  • Using MuLTEFire as a stepping stone towards licensed spectrum sharing arrangements
  • Leveraging dual connectivity, which enables a mobile device to simultaneously connect to macro and small cells for improved service performance
  • Advanced operational automation, such as ultra-SON, which improves the manageability of small cells
  • Emerging management techniques that normalize operations in network sharing environments.

These techniques essentially isolate network management functions to address challenges with traditional network sharing solutions that tend to subordinate one or more of the operators in the sharing arrangement.

It’s natural for mobile operators to resist new concepts that involve resource sharing with their competitors. However many of the objections towards resource sharing are similar to those raised in the past when network tower and infrastructure sharing concepts were initially proposed. Furthermore, we believe that the emerging dynamics of the mobile industry create a basis for operators to focus their attention beyond traditional operational tenets, particularly when they restrict the pace of network and service innovation.

Phil Marshall is chief research officer for Tolaga Research

This article was first published in Telecom Asia LTE Insights October edition

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