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LTE Evolution To 5G

(San Francisco - Alvin Wei-Cheng Wong)



5G - Powering the New Digital Economy



- Mobile Phone Standards for 2G, 3G, and 4G LTE

Global System for Mobile Communications (GSM) and IS-95 were the two most prevalent 2G mobile communication technologies in 2007. In 3G, the most prevalent technology was UMTS with CDMA-2000 in close contention. 

All radio access technologies have to solve the same problems: to divide the finite RF spectrum among multiple users as efficiently as possible. GSM uses TDMA and FDMA for user and cell separation. UMTS, IS-95 and CDMA-2000 use CDMA. WiMAX and LTE use OFDM.

5G uses 5G NR air interface alongside OFDM principles. 5G also uses wider bandwidth technologies such as sub-6 GHz and mmWave. Like 4G LTE, 5G OFDM operates based on the same mobile networking principles.

3GPP is the industry organization that defines the global specifications for 3G UMTS (including HSPA), 4G LTE, and 5G technologies. 3GPP is driving many essential inventions across all aspects of 5G design, from the air interface to the service layer. Other 3GPP 5G members range from infrastructure vendors and component/device manufacturers to mobile network operators and vertical service providers.

- 3GPP System Standards Heading Into The 5G Era

The 3rd Generation Partnership Project (3GPP) covers telecommunication technologies including radio access, core transport networks and service capabilities.

LTE (Long Term Evolution) is initiated by 3GPP to improve the mobile phone standard to cope with future technology evolution and needs. LTE has evolved quite consistently along its standards adding, release after release, new features that complete and enhance the telecommunication ecosystem broadly and in so many business ramifications as no other technologies ever before. Starting from its initial definition and architectural basis, LTE has become a more and more complete solution with LTE-Advanced, first, and then with LTE-Advanced-Pro, before ending up in the 5G era. 

From 3GPP Release 15 onwards, the community has been defining 5G networks, starting with Non-Standalone 5G systems that integrate with existing LTE networks and then moving on to Standalone 5G systems with substantially different network configurations. The primary goal of LTE and previous generations of mobile networks has been to simply offer fast, reliable mobile data services to network users. 

The enhancements in the 3GPP releases 16 and 17 of 5G New Radio include both extensions to existing features as well as features that address new verticals and deployment scenarios. 3GPP has provided complete system specifications for 5G network architecture which is much more service oriented than previous generations. Services are provided via a common framework to network functions that are permitted to make use of these services. Modularity, reusability and self-containment of network functions are additional design considerations for a 5G network architecture described by the 3GPP specifications. Operation in unlicensed spectrum, intelligent transportation systems, Industrial Internet of Things, and non-terrestrial networks are just a few of the highlights.

(Cellular Base Station Antennas - Ericsson)

- 5G NR Standalone (SA) and 5G Non-standalone (NSA) Modes

Current 5G wireless devices also have 4G LTE capability, as the new networks use 4G for initially establishing the connection with the cell, as well as in locations where 5G access is not available. The current 5G networks use NSA mode which requires simultaneous connection of 4G and 5G-NR radios to the user device. Future 5G networks will use 5G-SA mode, which allows operation without a 4G network in the area.

Some 5G NR deployments are working as 5G NSA, which means it relies on the existence of a 4G network to function properly. This 4G network can be used for certain information that's necessary for establishing a connection to a tower. The early stages of 5G deployment had phones falling back on 4G for uploads mainly but have started to move towards a standalone 5G network. 5G SA is the future of 5G NR deployment since it will be able to operate on its own. This will make deployments simpler and cheaper. It can also lead to an overall stronger network since the entire infrastructure

The first 5G devices will still rely on LTE. 5G NR phase one will eventually feature both SA and NSA modes of operation. In NSA mode, the mobile device uses 4G and 5G networks simultaneously, maintaining a connection with both a LTE eNB and a 5G gNB. In the meantime, radios will use both LTE and NR transceivers simultaneously, placing considerable attention on improving power efficiency and reducing interference. 

The eNB (Evolved Node B) is the element in E-UTRA of LTE that is the evolution of the element Node B in UTRA of UMTS. It is the hardware that is connected to the mobile phone network that communicates directly wirelessly with mobile handsets (UEs), like a base transceiver station (BTS) in GSM networks. The gNB (Next Generation Node B) is a 3GPP 5G Next Generation base station which supports the 5G New Radio.


- 5G Spectrum and Frequency

Multiple frequency ranges are now being dedicated to 5G new radio (NR). The portion of the radio spectrum with frequencies between 30 GHz and 300 GHz is known as the millimeter wave, since wavelengths range from 1-10 mm. Frequencies between 24 GHz and 100 GHz are now being allocated to 5G in multiple regions worldwide. 

In addition to the millimeter wave, underutilized UHF frequencies between 300 MHz and 3 GHz are also being repurposed for 5G. The diversity of frequencies employed can be tailored to the unique applications considering the higher frequencies are characterized by higher bandwidth, albeit shorter range. The millimeter wave frequencies are ideal for densely populated areas, but ineffective for long distance communication. Within these high and lower frequency bands dedicated to 5G, each carrier has begun to carve out their own discrete individual portions of the 5G spectrum.


- Dynamic Spectrum Sharing (DSS)

Dynamic Spectrum Sharing (DSS) is a technology that allows the deployment of both 4G LTE and 5G NR in the same frequency band and dynamically allocates spectrum resources between the two technologies based on user demand. When a carrier wants to use its 4G spectrum for 5G, it has to decide whether to discontinue 4G service or share it with 5G. The best way to get this done right now is DSS. With DSS, equipment on the tower changes how much of the available spectrum should be available for each connection type on the fly. Within milliseconds, the network can be adjusted to fit different types of loads. 

This can be easily understood with the help of an example. Suppose, without DSS, a Mobile Network Operator (MNO) that has 20 MHz of mid-band spectrum would have to split that spectrum in two. In other words, they would have to allocate 10 MHz of spectrum to 4G LTE and cram all their LTE users into that 10 MHz of spectrum. Then the remaining 10 MHz of AWS (Advanced Wireless Services) spectrum could be used for 5G, even though initially there will only be a minimal number of 5G users. 

With DSS, a MNO doesn’t have to split that mid-band spectrum or have a dedicated spectrum for either 4G LTE or 5G. Instead, they can share that 20 MHz of spectrum between the two technologies.


- Core Network Migration

As Evolved Packet Core (EPC) played a key role in 4G LTE, 5GC is the new 5G core network (5GC) defined by 3GPP. Unlike previous generations, 5G deployment can use either the existing EPC or the 5GC. In addition, 5G introduced either in StandAlone mode (SA) using 5GC or in Non-StandAlone mode (NSA) with EPC/5GC, which adds complexity to find the best migration path to 5G.


[More to come ...]

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