5G In-Building Deployment Trend: Roll-Out Options and Challenges


23 November 2018

Real estate companies, building owners, landlords and others are beginning to see wireless as a “fourth utility” after water, power, heating and cooling. This takes on further emphasis when the trend towards “buildings-as-a-service” is being exemplified by some co-working organizations. This new class of facility often incorporates wireless connectivity as both a billable service element, but also to enable their owners to manage energy-efficiency and security in properties.


With further developments in technology in the coming years, 5G networks will enable enhanced mobile broadband (eMBB) services, and create huge potential for new value-added wireless services through a wide range of new use cases. Monetisation and data-analytics around wireless location-sensing or tracking are also becoming a more important factor. These may be extremely demanding on in-building coverage solutions, especially as some networks may use frequencies above 6GHz, or even as high as 80GHz. Also, huge growth in narrowband wireless connecting low-powered networks of sensors or other endpoints, which may use 3GPP technologies such as NB-IoT, or other options such as LoRa and SigFox. For these reasons, the 5G business opportunity will be overwhelmingly indoors.


Challenges facing building owners and operators

Convergence or divergence of mobile networks to 5G

The unknown here is the convergence of different network types. On one hand, cellular networks are embracing Wi-Fi for offload, or for multi-network aggregation, especially when returning flat-rate data plans may stress these networks. On the other hand, some networks are looking at running 4G or 5G in unlicensed spectrum instead of, or in addition to Wi-Fi. Yet more service providers are adopting a “Wi-Fi first” approach, reverting to MVNO (mobile virtual network operator) models for cellular where needed. Future permutations may be more complex, but it all needs to be well-supported by indoor wireless infrastructure.


The migration of mobile networks to 5G will happen gradually. Operators will need to continue their LTE buildouts, and simultaneously ensuring their LTE systems are 5G ready. This requires the ability to be upgraded to 5G, in an easy and economical way, while supporting mixed LTE and 5G operation. Making it difficult is the uncertainty regarding final 5G radio standards and the frequency bands each operator will use for 5G.


Building materials and costs

Modern building materials such as treated glass, steel frames, and metalized insulation make it hard enough for some of today’s licensed spectrum to get through building walls, which will be further complicated by 5G’s high-frequency transmission.


Other than this, the deployment of multiple infrastructures not only increases total capital expenditure, but also raises maintenance and operational costs, as well as equipment space requirements.


Roll-out Options

The key to effective indoor mobile cellular coverage and capacity is a far-traveling, uninterrupted radio signal. There are a number of alternative approaches to bring 5G services indoors. Most of them involve adapting the outside macro network for use indoors.


Upgrade existing DAS

For those small and medium-sized buildings less than 100,000 sq ft, they are still seeking a cost-effective solution. Traditionally, a DAS solution can support multiple carriers over one antenna network distributed throughout the building. For signal deterioration occurring in these buildings, cell signal boosters may be effective and cost less than a passive DAS. They are good solutions for many buildings but not for venues like stadiums or hotels, which may need active DAS that gets an extra boost from fiber, antenna amplifiers, remote access hubs and expansion hubs.


A signal booster system set up in a building of whatever type is a passive DAS system in itself, it is the cable, antennas, amplifier without any need for a fiber connection to a tower or carrier-specific connectivity of any type, or backhaul. Thus, a single operator DAS will boost network performance for that service provider, while a multi-operator or neutral host DAS will improve service for several service providers.


Overlay solution

Buildings from 100,000 - 500,000 sq ft can be served by multi-carrier small cells. They are corporate and multitenant high-rise buildings, hotels, retail, smaller hospitals and educational institutions giving a large and rapidly growing market opportunity for in-building wireless solutions, with increasing revenue to compete for each year.


DAS and small cells are two technologies designed to supplement the macro network with indoor coverage. Instead of doing one of those big macro base station cabinets as a signal source, small cells which go with a low power output to feed into that DAS system and support one sector of the DAS can be a good option for medium to large sized buildings. Around seven small cells might fit into the same space previously occupied by a rack of DAS head-end equipment.


A small cell solution includes the base station, making it fully part of the operator’s radio access network (RAN). LTE small cells use the standard S1 interface* to the operator’s evolved packet core (EPC) network which carries user and session information, for better support of location services, and more granular visibility for performance optimization and troubleshooting. The main cost of this approach is its more complex one-time integration with the MNO core network systems.


Although small cells can augment DAS networks with targeted coverage and capacity, when multi-carrier coverage is needed, typically it is required to have a set of small cells for each carrier, adding cost and complexity of installation and management.


All-in-one solution

Passive DAS consists of power splitters, couplers, feeders, ceiling antennas, and other components. The existing passive distributed antenna systems support only the Sub-3 GHz (698 to 2700 MHz) frequency band, but they do not support 5G frequency bands 3.5 GHz, 4.9 GHz, nor mmWave. Despite the current feeders being able to transmit 3.5 GHz signals, the resulting loss is higher than transmitting Sub-3 GHz signals, which makes 5G-oriented evolution infeasible due to technical issues and high cost.


5G radio access deployments are characterized by their highly dense, throughput focused and software-driven nature. Combined with evolution towards a 5G-based multi-radio access technology core network, LTE will still play a critical role in providing connectivity for certain classes of IoT traffic that are less dependent upon capacity, low latency or ultra-reliability.


The 5G radio access network (RAN) will not replace the existing LTE networks. LTE is to provide a foundational general connectivity layer, covering some of the important traditional functions of mobile networks: voice service (VoLTE) and messaging. While existing frequency bands below 6 GHz will still play an important role in next-generation networks, the adoption of centimeter and millimeter wave bands (3-30 GHz and 30-300 GHz, respectively) will be critical to the delivery of consistent, multi-Gbps throughputs.


The differences between 5G and LTE will be the logical separation of each component of the 5G fNB (future NodeB). There is a baseband split with the lower layers of the 5G protocol stack merging with the radio unit to form a new element called the Access Unit. A core design principle of 5G networks is the assurance of seamless interworking between the two radio access technologies (RATs). By using multi-band RAN small cells as an alternative to legacy macro base stations for a DAS signal source, advantages of preserving the investment and scalability of the DAS can be achieved.


When planning for indoor connectivity or its enhancement, design engineers can specify a full-spectrum distributed antenna system network, which best supports carrier aggregation features of today’s 4G and will be in the best position to support indoor 5G moving forward.


* S1 is a digital, data- and control-plane interface that can operate over standard broadband connections such as fiber, cable, DSL and metro Ethernet.

About Marie Ma

Marie Ma is currently the general manager of Comba Telecom Network Systems Limited. Ms. Ma is responsible for overseeing the strategies and development of the new solutions and product marketing. She graduated from Tsinghua University with a master degree in Information & Communications Engineering in 2007 and a bachelor’s degree in Electrical Engineering &Automation in 2004. Ms. Ma has wide experience in product management, technical marketing and business development. She joined the Group in 2007.

More Articles