2020 is the year that most countries are ready to deploy 5G networks. This is also the dawn of a new decade where 5G is expected to be developed and evolved massively. Since the breakthrough of mobile communications several decades ago, evolution was the name of the game. Initially, it was the first generation of mobile analog telephony. Then digital mobile communications came, and GSM, the Global System for Mobile communications, was introduced with a common global framework for 2G voice calls and text messaging. Next, the 3rd generation of mobile telephony (3G) was developed, where the first mobile data was exchanged using HSPA technology and bringing the internet to our mobile devices. With Long Term Evolution (LTE), the 4th generation of mobile telephony (4G), broadband speeds were available to the end-user, bringing web browsing and live video streaming to the next level for enhanced user experience. LTE was further developed to LTE Advanced, using carrier aggregation techniques for higher speeds and better overall performance and user experience.
Taking into account the time frame that each of the above technologies was presented to the public until each technology reached maturity and a new technology appeared, it seems that it usually takes about ten years for a generation change. First-generation analog mobile telephony appeared in the 80s, GSM in the early 90s, mobile data communications with 3G in the early 00s, data broadband with 4G in 2010, and now 5G at the beginning of this new decade. This means that 5G will have a decade on which to evolve and be deployed to every corner of the earth.
5G services
5G networks are not only about higher speeds but also about high connectivity, high availability, and low latencies. According to ITU-R Rec M.2083 for International Mobile Telecommunications 2020 and beyond, 5G usage scenarios focus on 3 distinct areas, Enhanced Mobile Broadband (eMBB), Massive Machine Type Communications (mMTC), and Ultra-reliable, Low-latency Communications (URLLC).
Enhanced Mobile Broadband (eMBB) applications are the type of services that require super-fast multi-gigabit speeds to support fast downloading, high-quality UHD video streaming, 3D videos, etc. These high speeds can be achieved by the use of higher frequencies, especially in the millimeter-wave region. This way, large channel bandwidths can be used, and together with advanced spectrum efficient techniques such as carrier aggregation, MIMO, and high modulation schemes will support super-fast data rates.
Massive Machine Type Communications (mMTC) are the types of applications that do not really require super-fast speeds, but need connectivity to everything and everywhere. These applications include narrowband IoT, industrial automation, smart home, smart cities, smart farming, all of which require connectivity to various devices such as home appliances, sensors, and device-to-device communications.
From the above areas, Ultra-reliable, Low-latency Communications (URLLC) is the 5G area that will provide services with the most demanding requirements on latency and reliability. 5G systems should be able to provide end-to-end latency as low as 1 ms for applications that require ultra-low response times such as e-Health, remote Surgery, Tactile Internet, and Autonomous Driving.
5G Evolution considerations
One thing to consider about the expansion and evolution of 5G is the infrastructure. 5G non-standalone (NSA) mode is the initial 5G configuration that will be supported by most operators in every country. 5G non-standalone mode will take advantage of existing 4G infrastructure for the smooth integration of 5G technology to the networks of Mobile Operators. 5G networks will initially use the existing LTE Ethernet packer core. Gradually, the industry will move to 5G Standalone (SA) mode, where 5G gNodeBs will have their own RAN, Transport, and 5G Core.
Another factor that is expected to affect the evolution of 5G networks is the penetration of digital devices and their connectivity. To achieve human to device or device to device communication, you need connectivity to the internet and mostly via the newly established 5G networks. For this purpose, each device has to go digital or be formed by digital parts. Internet of Things (IoT) and industrial automation is an era of 5G that will mostly be covered by the Massive Machine Type Communications (mMTC). This means that wireless connectivity has to be established to cover a large number of newly deployed digital devices. These devices include digital embedded chipsets and an extensive multinational network of sensors to be deployed in major cities, in the case of smart-home and smart-cities and in the countryside, in case of smart agriculture.
Mobile devices and the support of 5G frequencies and capacities are also a significant factor for the expansion of 5G to the end-users. 5G supporting devices are currently starting to be introduced nowadays, and their market penetration is vital to the development of 5G.
Technical challenges for 5G deployment
The first 5G networks can achieve higher speeds by aggregating carriers between 4G and new 5G frequencies, for example, 3.5GHz, or using existing 3G or 4G carriers and re-farming them to 5G. The way most operators will take advantage of existing infrastructure and LTE architecture for 5G early deployment is utilizing NSA mode and Dynamic Spectrum Sharing (DSS). As the term implies, in dynamic spectrum sharing, the spectrum is shared between LTE and 5G NR. In existing 4G architecture, a 20 MHz carrier of the primary cell (LTE PCell) can be aggregated, for example, with a 5 MHz carrier for the secondary cell (LTE SCell). In early 5G deployments, the LTE carrier can be aggregated with an NR using adjacent channels in FDD mode, or a co-channel frequency can be shared between LTE and NR in TDD mode. However, carrier aggregation between LTE and NR may cause interference between the LTE reference signal and 5G channels. The challenge is for the LTE physical layer design, since sub-frames are not empty even if there is no PDSCH scheduled, and on the downlink when 5G is moved to the mid or low band spectrum, there will be a rather small increase on the speeds experienced by the end-user. This is because the shared LTE + NR channel requires 1 LTE control channel and 1 5G control channel, which means more overhead. Since one control channel requires about 15% of the overall channel capacity, adding NR to an existing LTE channel will reduce the user data accordingly.
Furthermore, most devices do not support the LTE Anchor and the 5F FDD carrier in the same spectrum area. For example, devices do not support NR on band n1 (2100 MHz re-farming) and LTE anchor on band 3 (1800 MHz). The way around is to use lower bands for anchor such as Band 20 (800MHz) or Band 8 (900MHz). Of course, the network will have to perform a handover from 1800 MHz to 800/900 MHz before 5G can be added. There is also no support for NR Band n28 (700 MHz) and LTE anchor on Band 20 (800MHz), which means that 1800 MHz can be used as an anchor, however, with inferior coverage.
Using Band 20 (10MHz) or Band 8 (5MHz) could also result in lower uplink speeds compared to the LTE-only devices than can camp on band 3 (20 MHz). Since LTE inter-band uplink CA is not possible due to device hardware limitation, the solution is to split the uplink LTE and NR bearer. So for the near future, most operators will start with one DSS channel, and due to LTE CA + 1 5G DSS channel, most data will still flow over the LTE part of the 4G/5G connection to the user equipment.
The 5G Evolution timeframe
The first 3GPP release for 5G NR, Release 15, was mainly focused on enhanced mobile broadband (eMBB) and only a small part on ultra-reliable and low latency communications (URLLC). This means that Enhanced Mobile Broadband (eMBB) communications are the main part of the first 5G services offered to the end customers.
Furthermore, the LTE core, although a relatively modern technology, still had a monolithic system approach, with big physical hardware, MMEs, and gateways. The 5G core, on the other hand, is expected to use a cloud-based, virtualized architecture to add scalability, flexibility, and fast expansion via software. Instead of interfaces, different instances will be used, and the idea is to move to open virtual interfaces and stop using old protocols.
The broad set of 5G applications including high-speed, connectivity, high-reliable, and low-latency networks will need an independent 5G core. The gradual transition of 5G networks from NSA to SA architecture is expected to take from 3 up to 5 years for most of the major Telecom Carriers. Considering the above, 5G will not be able to support all use cases from day 1, but will gradually evolve during the next years reaching its full potential by the second half of the decade. This will enable 5G networks to support a wide variety of 5G advanced services, and in turn, pave the path for the next generation of mobile communications, 6G, in the 2030s!
