Evolution to in-Building 5G

The in-Building 5G Market Opportunity 

5G promises a feast of technical capabilities: multi-gigabit user data rates, millisecond latency, ultra-reliability on a massive scale and more. For mobile network operators, delivering on this promise will require a massive investment in infrastructure, as much as $250 billion in the U.S. alone . 

Quantifying the return on that investment is difficult at best, although, typically, operator subscription pricing is not speed or performance-based. On the operations side, 5G offers potential cost savings through network functions virtualization and increased spectrum efficiency. However, these savings will take time to become significant, as will the penetration of 5G devices. Until these benefits reach critical mass, operators must continue to support their LTE, legacy 3G, and even 2G services for years to come. 

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Alternative Approaches

There are a number of alternative approaches to bringing 5G services indoors. Most of them involve adapting the outside macro network for use indoors. Outside-in As discussed earlier, this approach uses the outdoor macro network to serve the in-building space. 

Solutions range from simply using nearby macro sites to cover as much of the indoor space as possible, to adding outdoor small cells in high-density areas, a process known as “densification.” Likewise, the effort and cost associated with the outside-in approach varies as well, from zero cost and effort involved in the macro-only solution, to multiple issues,site access, municipal zoning restrictions, availability of back haul and power ,that must be considered in cell densification. Regardless of the approach, outdoor signal generation for indoor use has fundamental shortcomings that will increase as we move toward 5G: 

1.High-frequency path loss: 

5G signals tend to reside in higher frequency bands that lose signal strength rapidly when attempting to penetrate exterior building materials. Additional losses occur as the signal moves deeper into the interior of large buildings.

2.Energy-efficient building design: 

Low-e window materials, increasingly in use, block RF signals more than traditional glass—further limiting RF signal strength. 

3.Macro capacity impact: 

Serving indoor spaces from the outdoor network drains capacity from the macro cells. As in-building signals weaken, indoor users require more network resources to maintain connections. Under heavy traffic loads, this disproportionate demand from indoor users can impair the performance of the outdoor macro network

These challenges have existed for 3G and LTE but, in many cases, have been tolerated in order to deliver best-effort voice and data service. With 5G running mission-critical and revenue-generating services which require demanding latency and reliability requirements the performance degradation all but rules out outside-in as an in-building approach.

Standalone small cells In a standalone small cell solution, each access point is a unique physical cell. Since most operators have a limited number of channels to use indoors, standalone small cells operate on a common channel, creating interference among neighboring cells. For dense deployments in larger buildings, inter-cell interference limits performance, making standalone small cells unsuitable for 5G. With no coordination between cells, each small cell sees the user independently from the others, the antithesis of a user-centric network. Similarly, since each access point acts on its own, there is little opportunity for edge intelligence, apart from handover control.

While many other in-building wireless solutions require coaxial cabling and proprietary switching nodes, standalone small cells are deployed over Ethernet, a big advantage in terms of deployment simplicity. 

These systems also could, in theory, offer programmable radios. But, in order to keep the price affordable, individual radio access points which contain the entire baseband processing stack are built on cost-optimized consumer-class chipsets whose functions are static. The lack of programmability almost ensures they will need to be replaced or fully overlaid in the migration from LTE to 5G.

This article was extracted from  "Evolution to in-building 5G"  by  CommScope 

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