The term 5G is not currently well-defined and it will take some time before we can see its usefulness in modern-day technologies. While the rules for 5G may not be finalized until around 2020, numerous companies and universities are evaluating their 5G equipment prior to the standardization.
5G technology needs development in various aspects of engineering. For example, before arriving at the final design, companies need to comprehensively investigate different radio architectures, antennas, and even signal processing techniques.
The quality of service is very different among users of cellular networks. Image courtesy of ITU.
The Pros and Cons of 5G Communication
Traditional cellular networks are based on sub-6-GHz bands, which are very crowded at this point. The scarce free spectrum in these frequencies does not allow for high data rates. To deliver data at considerably higher rates, 5G will utilize millimeter waves, which are officially defined as signals with frequencies between 30 and 300 gigahertz.
Although the communication at higher frequencies provides incredibly high data rates, there is a big challenge regarding the coverage range. Travelling through water and air molecules, the high-frequency signals experience much more attenuation compared to sub-6-GHz signals. As a result, for the same coverage range, a 5G network will need more power than a traditional network does. In addition, we will need more sophisticated signal processing techniques and/or a substantial increase in the number of utilized base stations.
In July 2016, the U.S. Federal Communications Commission allowed commercial usage of some high-frequency bands including the band around 28GHz. Verizon and AT&T have been testing their 5G equipment at 28GHz. While this frequency seems attractive for 5G, AT&T is also testing its 15GHz trial at a site in Austin, Texas. Its lab tests have exhibited data rates of 14 gigabits per second with a 15-GHz link.
In a recent experiment conducted by Keysight and UC San Diego, the viability for a 5G link has been apparently been proved.
Keysight Collaborating with UC San Diego
Keysight Technologies has cooperated with a research team at the University of California San Diego to build the world’s longest bidirectional phased-array 60-GHz link. The 32-element array has achieved data rates of 4 Gbps, 2 Gbps, and 500 Mbps at a link distance of 100 m, 300 m, and 800 m, respectively. At up to 300 meters, the link can deliver data to eight homes at a time.
According to Gabriel M. Rebeiz, a distinguished professor at the UC San Diego Jacobs School of Engineering, UC San Diego is a world leader in the design of affordable phased-array transmitters for 5G communications and has 64- and 256-element phased-arrays with operating frequencies from 6 to 100 GHz.
Photo courtesy of UC San Diego Jacobs School of Engineering
The high-performance silicon germanium BiCMOS process from TowerJazz has allowed the entire phased array to operate with power as low as 3 to 4 W in either the transmit mode or the receive mode. ToweJazz’s BiCMOS process, which provides 240-GHz low-noise SiGe bipolar transistors and CMOS analog devices, is suitable for 60-GHz 802.11ad and other high-frequency applications such as radar, optical wireless communication, and emerging wireless standards.
To prototype and characterize the phased-array 5G communication link, Keysight has provided the research team with M8195A arbitrary waveform generator, E8267D PSG vector signal generator, and DSOS804A high-definition oscilloscope. Moreover, the company’s software has enabled the team to generate the 60 GHz 802.11ad waveform, achieve digital pre-distortion and improve error vector magnitude (EVM) performance.
Such experiments prove the feasibility of 5G, especially for the fixed-broadband use cases similar to those that Verizon is focusing on.
Verizon’s Fixed Wireless 5G Networks
Verizon, which is already testing 5G at its headquarters in New Jersey, has brought forward its initial commercial deployment of 5G from 2017 to early 2017.
However, McAdam reiterates what the company means by 5G deployment in 2017. Verizon will install a 5G network for fixed wireless communications. A fixed wireless system allows communication between two stationary points. For example, the data is beamed from a base station to a rooftop antenna and the users within the antenna get access to broadband internet via Ethernet cables. Instead of going fiber all the way into the home, they will stop somewhere about 200 to 1,000 feet away from the home and build a wireless 5G connection to the home. According to some analysts this could be the proof point of the technology’s potential. However, since the true 5G must deliver high-speed data to mobile users rather than to some fixed points, Verizon’s fixed wireless networks have attracted some criticism.
Paul Struhsaker, chief technical officer for the investment group Carnegie Technologies, believes that fixed wireless networks are unfortunate distractions and will delay mobile 5G.
The company will utilize a number of techniques such as C-RAN, massive MIMO and carrier aggregation.
Small Cell: A Differentiator in 5G World
Companies like Verizon and Sprint are already using small cells to densify their network and improve its capacity in relatively busy areas such as stadiums, arenas, and near malls. In these cases, a large number of users are connecting to the same tower and the use of small cells can considerably improve their coverage and communication speed. However, Verizon further emphasizes that small cell densification and spectrum refarming could have a huge impact on the advent of 5G.
Small cells are low-power radio access nodes which can cover a range of 10 meters to 2 kilometers. In contrast, a macrocell has a range of a few tens of kilometers. Mobile operators are currently achieving more efficient spectrum management in LTE Advanced and data offloading in 3G through adding small cells to a preexisting network of macrocells.
Moreover, for small communities in rural areas, small cells could prove to be more economical than the macrocells. To provide rural coverage, Japan has installed more than 3,000 small cells which use the VSAT satellite backhaul to connect to the core network. It is worth mentioning that the backhaul provision is one of the main challenges in utilizing small cells.
Besides, analysts believe that a close relationship with the municipalities plays a major role in establishing a network of small cells.