Skip to main content

Options for in-building wireless deployments

More than 70% of wireless voice and data activity begins indoors, so improving in-building wireless coverage and capacity is a hot topic of conversation for wireless service providers and vendors.  Three main options are available to the industry:

  • Distributed antenna systems (DAS)
  • Distributed radio systems (DRS)
  • Small cells

With no two in-building environments exactly alike, is one option better than another? It is clear is that there is no one-size-fits-all solution to the indoor deployment challenge. DAS, DRS and small cell architectures each have strengths and weaknesses,  that must be assessed and balanced against network objectives, the limitations of the in-building environment, future capacity requirements, and cost.


Subscribers demand uninterrupted, ubiquitous connections for their bandwidth hungry applications. This demand creates a need to extend the reach of cellular networks indoors. And it raises one of the most urgent and challenging questions facing the wireless industry: How can service providers offer acceptable in-building cellular coverage for subscribers today, knowing that deployments must scale to support the growing demand for data?

Providing the required in-building coverage can be difficult. Today’s market penetration in indoor environments with basic coverage is estimated at less than 10 percent globally across all segments.

Not only can indoor environments be hard to reach with outdoor macro cells due to such issues as site availability and frequency, in-building environments are uniquely challenging due to “clutter”. This takes the form of cement walls, elevator shafts, metal and even the type of window glass used.  In addition, the actual deployments that service providers must support are varied and complex, ranging from small to large enterprises, sporting venues, public service spaces, convention centers, casinos, and outdoor environments.

Many proposals are being offered by macro vendors, enterprise vendors, small cell vendors, and DAS vendors. This is creating confusion over technology options among industry providers and is potentially holding back the in-building cellular market.  More than ever, the industry needs guidance on how to address this market, recently estimated to be worth $4.3 billion in 2014 growing to $8.5 billion by 2019[1].


Three possible basic architectures can be used indoors. Each is made up of a baseband unit, a radio and an antenna -- fundamental building blocks that mimic the architecture used in outdoor base stations.

These building blocks can be centralized, distributed, or integrated together into modules. They are then distributed throughout a building and connected with cabling between each element and back to the operator core.

1. Distributed Antenna Systems (DAS):  Centralized baseband, centralized radio, distributed antennas with analog or digital RF connecting radio head and antennas over dedicated cable

2. Distributed Radio Systems (DRS): Centralized baseband, radio and antenna integrated in one module and distributed throughout the building/venue; common public radio interface (CPRI) connecting the baseband and the radio head over dedicated cable

3. Small Cells (distributed baseband systems): Baseband, radio and antenna integrated in one module and distributed throughout the building/venue; Ethernet to the core using shared cable


DAS Today, the most common solution for providing in-building wireless coverage is DAS because it:

  • Supports all major cellular technologies
  • Supports most frequency bands
  • Is neutral host, meaning it can support multiple operator networks
  • Is radio access network vendor agnostic.

But in-building backhaul, DAS’s most critical asset, becomes a limiting factor with respect to scaling to higher capacities in the future, requiring investment in more backhaul.

And while DAS is a strong architecture for delivering superior indoor coverage, DAS systems are viewed today as being expensive to deploy and operate. As in-building demand for wireless capacity grows, it will become increasingly challenging for DAS systems to scale technically or economically to meet that demand.

Distributed radio systems are a relatively new innovation and are best suited:

  • For delivering high capacity in dense venues like stadiums or train stations where the availability of fiber is unconstrained and readily accessible.
  • As part of a future centralized BBU/ cloud RAN architecture to improve interference management and simplify the placement of antennas.

Like DAS, the cabling is expensive, yet DRS is not neutral host. It will be limited to where operator differentiation is allowed or in environments where parallel operator systems can be deployed.

Small Cells
What about small cells? Small cells are gaining momentum in the industry as a viable option for providing high capacity in-building wireless coverage at lower CAPEX and OPEX cost. Small cells also scale more easily in response to increased usage of both voice and data services.

However, small cell solutions are not neutral host and their ‘likeness’ to the macro network requires attainment of similar KPIs.  To achieve this, small cell deployments will either require high quality design guidelines and RF optimization, or leverage emerging self-organizing/self-optimizing network algorithms for in-building optimization – either of which will increase the complexity of the small cell deployment.


The race is on for wireless operators to provide excellent in-building wireless service to their customers, especially as the demand continues for ultra-broadband experiences.

Challenges lie in technology as well as in deployment. But many new innovations are emerging from the industry, ranging from improvements or customizations of traditional DAS architectures, all the way to the introduction of small cell networks.

There is no doubt the in-building market will grow significantly over the coming years. And the small cell share of that market will increase as a function of time as wireless capacity, in addition to providing basic coverage, becomes a key purchasing decision.

We predict DAS, DRS, and small cell architectures will coexist and be combined with today’s macro deployments to create heterogeneous networks (HetNets) that will deliver a total ultra-broadband experience for end users.

Related Material

Alcatel-Lucent offers a variety of solutions to meet specific requirements:DAS - Alcatel-Lucent and TE Connectivity have introduced a DAS solution that dramatically reduces the cost of delivering mobile, ultra-broadband access in large public venues.DRS - In association with a Tier 1 operator in the Asia Pacific region, Alcatel-Lucent has developed an approach that leverages a cloud RAN-based architecture on a smaller scale at stadium sites.Small cells - Alcatel-Lucent offers a complete portfolio of outdoor, in-building and residential small cell products, which address specific market requirements.
Webinar: Fact vs. Fiction, the Debate on In-Building Architecture Options


  1. [1] “In-building Wireless”, ABI Research, February 2014

To contact the author or request additional information, please send an email to

Meggen Rayla

About Meggen Rayla

Meggen has been a Product Marketing Manager with Alcatel-Lucent since 2012, focused predominantly on Small Cells. In this role, she deals with positioning the Alcatel-Lucent small cells product portfolio both internally and externally. Meggen joined Alcatel-Lucent in 1998 and began her career in Corporate Finance. From there, she has held various roles within the wireless product unit spanning market and competitive analysis, market research, internal communications and business strategy and planning. Meggen holds an MBA degree from the London Business School, a Master’s of Science degree in Accounting from Babson College and a Bachelor’s of Science degree in Finance and Economics from Boston College.

Article tags