5G represents the next generation of wireless communications. But while the promises of 5G networks with higher capacity, lower latency, and increased bandwidth are exciting prospects, the value of such technological advancements will only be realized when they are applied to real-world use cases that drive mutual benefit to the end user. This is why engineers globally are endeavoring to unleash the benefits of 5G into a broad range of applications including gaming, virtual reality, autonomous cars, and wireless surveillance, to name a few. In each case, 5G is expected to drive innovative new business models, as companies start to take advantage of enhanced connectivity.

However, getting to the point of applying 5G at scale has predictably taken longer than some expected. Indeed, a recent survey commissioned by Molex and conducted by Dimensional Research showed that almost half of mobile carriers’ deployment plans have lagged compared to their initial expectations. The much higher signaling frequencies used with 5G have resulted in some unique engineering design challenges in areas such as signal propagation, power and thermal management, and antenna module placement.

Now, though, the efforts of engineers are starting to come to fruition, with 5G being rolled out around the world. The Molex survey showed that 89% of carriers were excited by the prospect of 5G, with 92% expecting to achieve their 5G business goal within the next five years. Furthermore, 99% of carriers said they expected 5G to deliver substantial benefits to end users within that timeframe. So, here, Molex makes a timely assessment of 10 critical technology enablers that go a long way to making 5G a reality.

5G is being supported by significant investment in the underlying infrastructures of mobile networks, particularly the backhaul/transport layer that connects base stations together and into the public communications network. With densely populated traffic cells supporting massive data flows to the core network through backhaul, a flexible approach to systems integration has emerged as the best option to meet a broad range of requirements such as capacity and latency. Optical fiber X-haul provides high resiliency while eliminating concerns about weather conditions and multi-path propagation. But it is not always feasible to lay down fiber to connect cells, as the cost can be prohibitive. That brings wireless X-hauling using IAB (Integrated Access Backhaul) wave to the fore, driving big advantages in areas such as availability and deployment time. By using this flexible dual approach, providers can deliver the right type of backhauling technology for the right type of network. Microwave X-haul is also being studied, since it has a longer range than IAB.

As new 5G applications start to evolve, there is an increasing need for flexible fronthaul solutions that meet 5G’s latency, throughput, and reliability requirements. This demand is being met by next-generation Radio Access Network (RAN), providing the fiber-connected links between Radio Units (RUs), Distributed units (DUs) and Centralized Units (CUs) that can be deployed tens of kilometers away from the DU location since CU functions are not considered to be real-time. Because of this their interactions are not latency sensitive. In addition to new architectures, fronthaul transport will make use of enhanced CPRI (eCPRI) protocol, which decreases the bandwidth requirements from the RU to the far edge DUs. The 3GPP 5G standard employs a methodology that enables the splitting of some of the 4G LTE baseband functions between the DU and CU. This will result in varying levels of performance. The performance will range from moderate to significant improvement over 4G LTE depending on spectrum used and at a lower cost per bit.

The use of millimeter wavelength (mmWave) by 5G presents some challenges, most notably signal propagation because of much higher absorption loss associated with atmosphere, weather conditions, building materials and foliage, etc. The human body can also contribute to losses. mmWave propagates in very narrow beams. The process that allows this is called beamforming. Another process allows beams to be directed towards the desired User Equipment (UE) location. This is called beamsteering. Additionally, these directed beams must shift as user equipment such as mobile phones change positions as users move. This is called beamtracking.

The use of mmWave provides significantly higher customer throughput and provides other huge benefits. mmWave signals tend to reflect off certain building materials. This enables mmWave signals to be used in directions not initially anticipated. For example, an antenna array could be used to support rear facing traffic if reflection is calculated properly. mmWAVE propagation limitations allow the reuse of those frequencies in much shorter ranges than that of 5G sub-6GHz frequencies and 4G LTE 700MHz frequencies. Essentially this process frees up that mmWave spectrum for use in other areas making spectrum usage very efficient.

The 5G air interface between devices and cells relies heavily on multiple-input, multiple-output (MIMO) phased-array antenna architectures to maximize the data rate between endpoints at scale. However, tightly clustered antenna configurations needed for large MIMO architectures create performance challenges for electronic components. At the higher mmWave frequencies, the physical distance between antenna elements on and antenna array is extremely minimal. The smaller the wavelength, the smaller the antenna element needed to capture the wavelength. The smaller the antenna element, the more antenna elements can be placed on a given antenna array space. It is assumed that more 5G components and higher frequencies will translate into higher power requirements at the typical radio location. Handling mmWave RF power and dissipating the heat in this environment is a tricky proposition and requires innovation in system design and material selection. This is why engineers are increasingly moving toward fourth-generation gallium nitride-based field-effect transistors with higher power densities which will enable the smaller packages needed by larger MIMO architectures.

Ubiquitous national and international 5G coverage will not happen overnight – it will arrive incrementally as carriers deploy their networks using alternative spectrums, with varying reach, latency, and data-carrying capabilities. Indeed, some parts of the world – mainly rural regions – might never enjoy the benefits of higher frequency mmWave-supported data rates as they will only be supported by sub-6 GHz frequencies. The Molex survey reveals that 26% of carriers feel that mmWave propagation issues are creating challenges in delivering 5G, whilst conversely, 53% felt that rural home access to 5G will be a primary use case to enable significant new business revenue. (Please note that these results are in dispute as the cost to deploy a rural network will be higher than comparable urban and suburban networks – and cost-prohibitive in many cases.) This is a challenge for mobile device designers releasing new user equipment (UE), such as phones during the 4G-to-5G transition. The solution is to incorporate multiple tuned antennas in new devices to handle 4G LTE waveforms in addition to 5G – with the choice between mmWave and sub-6 GHz antenna design no longer an either/or option. 3G waveform inclusion is anticipated at a smaller degree.

At 5G’s relatively lower frequency sub-6 GHz bands, the placement of the antennas is only part of the performance equation. There is a strong relationship between the antenna and the mobile device’s internal configuration in determining the overall resonance performance of that device’s wireless communications. Given user preference for thin mobile devices, antenna engineers have needed to consider the physical design, material selections, and internal component configurations when tuning the antenna design. At mmWave frequencies, though, the interaction between the antenna and the phone body is not as much of a concern. Instead, the challenge is that the covering over the antenna, be it metal, glass, or even plastic that is no longer electrically thin and can have negative impacts on the radiating performance of the underlying antenna. Also, the placement of the antenna with respect to the device user’s hand will have effects on mmWave transmission and reception. Here design engineers are looking at how to couple tailored antenna design and unique antenna placement along with slot-based design or frequency selective surface design principles which can be employed successfully to optimize the radiation patterns of mobile devices antennas. Additionally, the use of multiple antennas on a UE is required to overcome beam propagation loss in non-ideal directions.

The quality of RF performance with 5G antennas placed on or near the printed circuit board of a device depends on the antenna’s effective integration in the product. Device manufacturers have increasingly turned to the skills and experience of radio frequency engineers, seeking out best RF design practices for optimally tuning the antenna to each device to enhance wireless performance. Antenna-tuning techniques include aperture tuning – where the electrical length of the antenna is calibrated to more closely match its resonance to the required frequency band, and impedance tuning – where the impedance of the antenna is correlated with the RF frontend. Both techniques can improve gain over a wider bandwidth and improve battery life, as a tuned antenna draws less current than an untuned antenna to deliver the same amount of transmitted power. This is a crucial factor when it comes to meeting consumer expectations around the performance of next-generation 5G mobile phones.

High frequency 5G signals also introduce further considerations around interconnections, board traces, cable assemblies, and connectors. Sending millions of bits across a series of components at speeds dictated by 5G standards inside consumer-grade products presents significant challenges. Connectors must be carefully designed and manufactured to minimize any impedance variations along the transmission line. External signals can also pose a threat. Therefore, connectors must sufficiently protect the system from external signals from electromagnetic interference and capacitive pickup, which becomes increasingly difficult at higher speeds. 5G connectors must also fit into the tiny spaces afforded by modern mobile devices. Stacked connectors allow for densely populated flexible and rigid circuit boards. Despite the stringent physical constraints, 5G electronics must still meet demanding requirements for scattering parameters, such as voltage standing wave ratio and insertion loss. Well-designed connectors can minimize reflections, degradation, and distortion of the signal while reducing its physical footprint, and can be adequate shielded to be effective at cutting down on EMI.

Designing and building 5G prototypes is just one step on the journey toward new product development. Rigorous new testing regimes are also required to ensure that hardware meets stringent specifications. This has required the development of new equipment and facilities such as 5G anechoic chambers which are capable of testing low-band, mid-band, and mmWave 5G frequency bands. Adequate testing gives OEMs confidence that their products and associated components are fully fit for purpose – reducing the risk of late-stage delays in product release to market, or poor performance at the point of use.

Packing maximum performance in the smallest spaces is another challenge for 5G design engineers. The latest Moulded Interconnect Device/Laser Direct Structuring techniques allow for the tight integration of complex 3D electrical and mechanical structures which existing 2D technologies cannot accomplish. This results in high-capability devices that are compact and lightweight. This capability combines the versatility of the two-shot molding process for MID, with the precision of Laser Direct Structuring technology to create compact, high-density applications that meet 5G device guidelines. These technologies provide solutions for 5G device manufacturers looking to address miniaturization without compromising performance.

Investment and innovation are clearly in play to ensure that 5G networks live up to the hype. The challenge for design engineers is to create new 5G products which are suitable for mass production and also meet customer expectations. This means selecting the most appropriate 5G components and properly incorporating them into highly sensitive environments, while also ensuring accurate testing.

With a predicted timeline of 2-5 years before widely deployed 5G will bring substantial end-user benefits across a full range of applications, and an immediate demand in consumer and fixed wireless access, it is critical that OEMs and communication service providers work with partners who are ahead of the technical demand.

Molex is highly invested in 5G research and development, providing a broad range of optical, copper, RF connectivity, antenna, networking, testing, and computing solutions. Through investment in state-of-the-art manufacturing equipment and new higher frequency RF test chambers, Molex enables the development of cost-effective, best-in-class products that help our customers bring 5G ideas and technology to market, faster.