On October 13, Apple released its new 5G iPhone 12 Pro and iPhone 12 Pro Max. Considering that Samsung has already launched its Galaxy S20 5G model plus a few more options, carriers and other network operators are right to wonder how consumer interest in these new products could affect demand on existing and future 5G networks. Certainly, competition is heating up.
While many carriers have been leveraging existing 4G LTE infrastructure to provide the first iterations of 5G, T-Mobile announced in August 2020 that it was the first carrier in the world to power up a standalone nationwide 5G network in the U.S. As other carriers likely follow suit with standalone networks of their own, the question becomes one of how to deploy reliable 5G infrastructure in a timely manner while minimizing the expenditures that need to be made on new optical networking equipment, including transceivers.
Preparing a network to handle the exponential increase in Internet of Things (IoT) devices and data throughput that 5G will bring is a costly endeavor. However, dual-rate optical transceivers as well as tunable optics can help carriers and other network operators minimize costs while futureproofing their networks for the increasing requirements of 5G. While there is no shortage of literature on the backhaul side of 5G networks, in this article, we concentrate our discussion on small cell fronthaul, where service providers need agility and flexibility to meet fluctuating consumer demand immediately.
Small Cells Revisited
As the IEEE explains, small cells are portable base stations or cellular radio access nodes “that require minimal power to operate and can be placed every 250 meters or so throughout cities.” Using millimeter waves, beamforming, and MIMO, they can work in both licensed and unlicensed spectrum.
Small cells are a necessity for 5G since the lower frequencies of existing 4G LTE infrastructure cannot support the bandwidth 5G demands. On the other hand, 5G small cells do not have the range of their 4G counterparts. Price Waterhouse Cooper notes that, according to the FCC, over 800,000 small cells will be needed across the U.S. for 5G to work. This density is critical to overcome their shorter range. However, density means large capital expenditures on the part of carriers and other service providers, especially considering that the U.S.’s country-wide 4G network features only around 200,000 cell towers.
Further complicating small cell functionality is the fact that 5G will rely on different types of small cells, including femtocells, picocells, and microcells. Each offers different coverage lengths, power utilization, and number of users. Femtocells support the least number of users and are generally used for extremely short-range indoor applications. Picocells support larger groups of users up to a range of 250 m and are mainly used for indoor public areas like office buildings, hospitals, malls, or train stations. Microcells have the greatest range (up to 2.5 km) and can support up to 200 users for primarily outdoor applications. Many small cells reside in environments that engineering technicians refer to as “hardened,” meaning that it is more complicated to send someone onsite to fix a small cell than it is to address issues in a typical access network’s central office.
Once deployed, operating small cells reliably is critical to reduce the total cost of ownership (TCO) of a 5G architecture. As RCR Wireless points out, small cell equipment failures require replacements, which can delay site turn-ups and require technicians to go onsite to make repairs. Even a 2% failure rate could cost network operators nearly “$1 million per year in site visit costs.” What is missing from this conversation, however, is the idea that small cell performance is only as good as that of the fronthaul networks that connect them to the centralized base band units (BBUs) positioned before the core network.
Fronthaul Developments: Are Network Operators Really Ready for 25G?
As Communications Industry Researchers (CIR) note, “growing interest in fronthaul is…due in part to the use of the relatively new C-RAN architectures for 5G infrastructure, which has heavy and costly bandwidth requirements that are creating significant new opportunities for fiber optic deployments.” Additionally, the ITU recently formalized the International Mobile Telecommunications-2020 (IMT-2020) standard for 5G transport. Developed over the last few years, the standard makes 25G eCPRI the prime choice for the 5G fronthaul interface.
Nonetheless, the fronthaul network represents “significant costs for 5G services providers,” according to CIR. In many cases, network operators may wish to use 10G transceivers due to their lower cost until the demand for 5G services is such that 25G data rates become a necessity. However, the time to switch is coming – Frost & Sullivan has found that the global 5G testing equipment market will grow at a CAGR of 11.5% to reach a total value of $2 billion by 2024. The key for network operators right now is to invest in solutions that are cost-effective in both the short and long term, enabling them to take incremental steps to higher data rates in the fronthaul network while keeping procurement and operating expenditures as low as possible.
Dual-Rate Optics and Tunable Transceivers: The Key to Cost-Effectiveness
Though dual-rate optics and tunable transceiver technologies have been available for some time, they have not saturated the 5G market for optical networking equipment. This, of course, is because the 5G landscape is still fairly new and network operators are still on the way to embracing the 25G data rate standard. SDxCentral editor Matt Kapko put it this way: “It will be many years before 5G deployments and the experience of users meets [the IMT-2020] standards…there’s a lot that has to happen before 5G delivers…many companies rely on fixed broadband or WiFi for connectivity and those that shift completely to 5G are going to be standouts, not the norm.” Because 5G has not yet widely proliferated among global consumers, many network operators are still relying on the 10G SFP+ CPRI optics prevalent in existing 4G fronthaul networks.
Times are changing for 5G fronthaul, however. According to P&S Intelligence, the 5G transceiver market is set to grow at a rate of 30.4% between 2020 and 2030. As individuals purchase more mobile devices and increasingly leverage data-intensive applications, greater demands will also be placed upon 5G fronthaul networks. As network operators besides T-Mobile move to deploy their own standalone 5G networks, subscriber consumption of high-bandwidth, ultra-low-latency-dependent applications will fuel a move toward 25G modules. After all, per the ITU, the network granularity of the IMT-2020 5G standard spans from 25G to 100G. Based on this, demand for 25G transceivers will increase over time. The move to 25G optics also supports adoption of 400G transceivers in 5G backhaul networks. As one can see, 25G transceivers support the holistic network upgrades that operators need to fully deliver on the promises of 5G.
Migrating to 25G presents logistical challenges to operators using 10G optics. Dual-rate transceivers bridge this gap by providing one piece of optical networking equipment that can be configured to support either 25G or 10G data rates. They offer significant savings to network operators. Whereas one would normally have to procure 10G or 25G transceivers depending on current fronthaul needs, dual-rate technology now reduces that expenditure to only one type of optic. This also means less money spent on establishing an inventory of spare equipment. As 25G gradually becomes the norm for 5G fronthaul networks, dual-rate optics will make it simpler and more cost-effective for network operators to make necessary upgrades.
In the same vein, tunable transceivers can further diminish the 5G cost curve. Tunable transceivers enable on-site wavelength adjustment, transcending the fixed-wave limitation of static models. With static transceivers, multiple backups are required to mitigate the risk of network downtime either due to an equipment issue or the need to shift to a different wavelength. Tunable optics minimize cost and maximize flexibility. From a 5G perspective, they give network operators easy and virtually instantaneous access to any of the C-Band channels that are fast becoming central to the new cellular standard. Coupled with tuning software and specialized tuning boxes, tunable transceivers eliminate the need for network operators to procure multiple fixed-channel optics along with their spares.
Conclusion
In the drive to make 5G rollouts feasible, network operators need all the help they can get from an optical equipment perspective. Fronthaul networks are critical in supporting the reliable operation of vital small cells. While the IMT-2020 standard promotes the use of 25G eCPRI as a fronthaul protocol, not all network operators, especially those leveraging existing 4G LTE infrastructure for their 5G rollouts, are ready to implement this. However, there is a growing body of evidence to suggest that the move from 10G to 25G fronthaul bandwidth will eventually become a necessity. As a result, utilizing dual-rate optics in combination with tunable transceivers can create a cost-effective formula, enabling network operators to implement 5G architectures both with speed and without breaking the bank. In turn, this will help accelerate the proliferation of 5G so that end-users, including consumers and enterprises, can benefit from all 5G has to offer.
Chris Page is CTO of Precision OT.