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Cognitive Radio
The International Telecommunications Unit – Radiocommunications Sector (ITU-R) defines a Cognitive Radio System (CRS) as:
“A radio system employing technology that allows the system to obtain knowledge of its operational and geographical environment, established policies and its internal state; to dynamically and autonomously ad-just its operational parameters and protocols according to its obtained knowledge in order to achieve predefined objectives; and to learn from the results obtained [15]. »
CRS have many uses in mobile broadband networks. A MNO may use a CRS to improve the management of its assigned spectrum resources. It also can be used as an enabler of opportunistic spectrum access. A CRS is used for TV White Spaces (TVWS). TVWS makes use of parts of the spectrum allocated to TV Broadcast, available at a given time in a given geographical area. However, the implementa-tion of CRS implies the need of new high-end equipment able to support it, which translates into a bigger investment from the MNOs.
LSA
LSA is a complementary way of authorizing and accessing spectrum. It is based on CRS techniques to determine spectrum availability. The LSA framework enables the sharing of spectrum between a limited number of users. In this novel access model a primary license holder, called the incumbent, would grant spectrum access rights to one or more other users, called LSA licensees, following specific service conditions established in a LSA agreement. The conditions on the LSA Agreement may be static or dynamic. Static conditions establish a fixed use of the shared spectrum on a frequency, location or time basis, while dynamic conditions could establish a use of the shared spectrum on frequency, location and time basis (e.g. Geographic-time sharing, on-demand authorization/restrictions). A key feature of LSA is to ensure a predictable Quality of Service for all spectrum rights of use holders, the incumbent and the LSA licensee whenever each has exclusive access to the spectrum.
The Radio Spectrum Policy Group defines LSA as:
“A regulatory approach aiming to facilitate the introduction of radio communication systems operated by a limited number of licensees un-der an individual licensing regime in a frequency band already assigned or expected to be assigned to one or more incumbent users. Under the Licensed Shared Access (LSA) approach, the additional users are autho-rized to use the spectrum (or part of the spectrum) in accordance with sharing rules included in their rights of use of spectrum, thereby allow-ing all the authorized users, including incumbents, to provide a certain Quality of Service (QoS) [16] ».
The following table (3.1) shows a comparison between different spectrum access schemes. It shows how LSA is a promising solution that can provide MNOs flexibility to expand their network.
LSA Stakeholders
There are three key stakeholders in the LSA Architecture: the incumbent, the LSA licensee, and the regulatory body. They all interact via a LSA Agreement that estab-lishes the way the spectrum is going to be shared. Figure 3.2 shows the stakeholders in a LSA scheme.
Incumbent
The incumbent could be the holder of an individual license, or a governmental orga-nization (e.g. Defense, Civil Aviation) with allocated frequency bands. It provides spectrum to be shared with the LSA Licensees (e.g. mobile industry and MNOs). In the case of an individual license holder, it can be a player of any radio commu-nication service. The incumbent could offer its low used spectrum to one or several LSA licensees. The LSA spectrum usage is negotiated with the LSA Licensee in accordance to the NRA’s LSA spectrum award rules. The LSA framework ensures primary spectrum usage rights to the incumbent.
LSA Licensee
A LSA Licensee (e.g. MNO) makes use of the incumbent’s shared spectrum in a dedicated way where, and when, the spectrum is not used by the incumbent following the pre-defined LSA agreement. LSA Licensee needs to comply as a prerequisite, to the LSA Spectrum usage license granted by the NRA. The LSA Agreement will define how, when and where can the LSA Licensee use the LSA spectrum.
NRA
In the LSA framework the National Regulatory Agencies will be in charge of issuing licenses to MNOs that allow them to use a band as a LSA licensee. These licenses can be issued on individual or general basis. Other NRAs roles such as defining the sharing conditions and usage requirements, and coordinating the sharing partners in adjacent frequency bands and borders, remain the same.
LSA Agreement
The LSA Agreement must have clear conditions for proper spectrum usage by both parts: the incumbent, and the LSA licensee. The incumbent is the primary license holder, thus LSA should ensure full certainty, without operational restrictions, for the incumbent. The LSA has the requirement to not cause harmful interference to the incumbent. The LSA Agreement must also include detailed conditions under which the incumbent can take back access to the spectrum in use by the LSA licensee.
LSA Architecture
Despite the minimum modifications to the existing infrastructure, the implementa-tion of LSA requires the inclusion of two new components, a LSA Repository and a LSA Controller. Figure 3.3 shows an overview to the LSA Architecture.
Spectrum Allocation in the Region
In order to serve the growing demand, more internationally harmonized spectrum throughout the region is required; harmonized spectrum would bring benefits from the economies of scale. Currently the 850 MHz and 1.9 GHz spectrum bands are common along the region. North America and some Latin American countries have auctioned parts of the AWS 1.7/2.1 GHz bands, while other countries have gone with the 2.5 GHz band. Regarding the 700 MHz band, Latin America decided to take the Asia Pacific Telecommunity (APT) 700 band.
Two trends in the Latin American markets are having an impact on spectrum allocation. Firstly, state-own operators are getting spectrum directly allocated, without any kind of auction process. And secondly, there are operators with unused allocated spectrum.
Bringing more spectrum to the market will help to deploy new technology faster, increase the network’s performance and throughput speeds overcoming the low ARPU and limited Capital Expenditure (CAPEX) in the Latin American region.
LSA in the Region
In order to fulfill the increasing demand, more spectrum has to be freed up. Exclusive licensed spectrum is preferred by the industry, however it needs to be cleared and this can take some time and bring high costs. MNOs will have to face the problem soon. Schemes such as LSA enhance spectrum harmonization, bring economies of scale and improve roaming capabilities.
The first steps in the region towards LSA were made by the United States. On June, 2014 President Obama issued a memorandum to “facilitate the relinquishment or sharing of spectrum allocated to US government agencies to make it available for commercial wireless broadband technologies and create new avenues for wireless innovation” [23].
Traditionally, in the region 2, countries from North America with higher GDP, i.e. USA, pioneer on making standards and band allocation policies. Most of the times, these standards and spectrum allocation policies are then adopted by southern countries.
LSA targets globally harmonized mobile bands, thus it can take advantage of economies of scale. Because LSA is a technology-neutral approach it can be used in Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD) deploy-ments. The 3.5 GHz Band has been defined as the candidate frequency band for the LSA implementation in the region. The band’s hamronization is very feasible around the world, and it can be used on both FDD and TDD approaches. LSA is a promising solution to overcome the problems from a re-farming process, such as time, cost and political issues.
The 3.5 GHz Band
On December 2013 the FCC proposed to allocate the 3.5GHz band for small cell deployment with the LSA scheme. They pointed out that LSA can incorporate the necessary “geographic restrictions to protect existing Department of Defense (DoD) radar and Fixed Satelite Services (FSS) operations and to protect new commercial systems from co-channel interference from high-powered military in-band shipborne and adjacent band DoD ground-based radar systems [24].” According to the Asian operators China Mobile and Softbank [25], the advan-tages and challenges of the 3.5 GHz band are:
• High throughput for outdoor/indoor hot zone.
• 200 MHz of available spectrum.
• Well suited for handling the severe unbalance and fluctuation of Downlink (DL)/Uplink (UL) traffic.
• Great isolation to avoid interference, ensure QoS and enable frequency reuse in the high frequency band Challenges.
• Low coverage range (0.3 kilometers).
• Chipset Availability.
• Not globally harmonized yet.
The most important challenge to be solved is the band’s global harmonization issue. However, the band is very likely to become a globally harmonized spectrum band. LSA can not only unlock some IMT bands occupied by incumbents but also bring economies of scale from other regions. In some countries of the region the 3.5 GHz band has been already assigned for fixed data services, WiMax or Fixed Satellite Services. The following picture depicts the situation of the 3.5 GHz band around the world. A worldwide view on the band can be seen in fig 4.3.
Table of contents :
1 Introduction
1.1 Background
1.2 Motivation
1.3 Research Questions
1.4 Related Work
1.5 Scope
2 Research Approach
2.1 Research Approach
2.2 Methodology
2.3 Qualitative Method
2.4 Quantitative Method
3 Licensed Shared Access
3.1 Spectrum Access Schemes
3.2 Cognitive Radio
3.3 LSA
3.4 LSA Stakeholders
3.5 LSA Agreement
3.6 LSA Architecture
4 The Americas
4.1 The Region
4.2 Mobile Growth
4.3 Wireless Revenues
4.4 Spectrum Allocation in the Region
4.5 LSA in the Region
4.6 The 3.5 GHz Band
4.7 Region’s Overview
5 The Countries
5.1 Chile
5.2 USA
5.3 Mexico
6 Analysis
6.1 Comparative Analysis
6.2 Cost Analysis
6.3 SWOT Analysis
7 Conclusions
7.1 Research questions
7.2 Comparison with other spectrum schemes
7.3 Limitations and Future Work
A Interviews
A.1 Interview: Gerardo Muñoz (América Móvil, Claro Chile)
A.2 Interview: Ken Corcoran (AT&T, USA)
A.3 Interview: Gerardo Aguirre (América Móvil, Telcel Mexico)
B MNOs in the Selected Countries
B.1 Chile
B.2 USA
B.3 Mexico
