Unwrapping 5G - vol.2

Technical Knowledge Required: Basic

Note: If you're a 5G nerd or in the technology domain where you work on 5G related products/solutions, I'll save your time by asking you to skip this article. This article is focused on technology enthusiast who do not work on 5G but have heard so much about it and want to understand without reading all white-papers and lengthy documents already published. 

Disclaimer: All the views, thoughts, and opinions expressed in this article belong solely to the author, and not necessarily to the author's employer, organization, committee, or other group or individual.

If you’re jumping directly on this article, it will be worth to check the basics of 5G. Before we dive into solution components that constitute 5G, let’s understand the elements part of 4G/LTE architecture that we currently use.

1.    What are the solution components that constitutes 4G/LTE? 

The below image provides a good visualization of elements that make the current architecture for the 4G/LTE network.

There are a few key elements to understand:

• User Equipment: Our mobile phones support 4G/LTE connectivity.
• Cell Site: All of us have seen these cell towers at various locations either standalone with Radio antennas or these mounted on electrical towers. Every cell site includes few elements like Remote Radio Head (RRH), Base-Band unit (BBU), and this helps to connect your mobile phone with the service. Radios used in LTE are referred to as evolved Node B. The word Macro is used to showcase coverage area which can be in the range of 10's of kilometers.

• Back-haul Network: Transport network that connects cell site to 4G/LTE Core. Usually, this network runs on Optical Fiber.
• Core: 4G/LTE network uses Evolved Packet Core. All the different functions from authentication of the user, user information, billing details, connectivity to user and data-plane, supporting user in roaming scenario across multiple macrocells, or even with other service providers. Access through core network to rest of the internet including clouds.
• Cellular Network Management layer: Network Management system, siloed orchestration systems, and billing systems are part of this layer.
• Centralized Cloud: As the word suggests, central clouds used to host applications. These can be private, public, or community. For example: if a company ABC is headquartered in California and has its private cloud hosting business applications there, access to a user in the Philippines over the phone will require traversing multiple continents and sub-sea network to access it. Now you can understand why some applications in your office take much time to load the page or process the outputs. Tip: It's because of latency, go read the volume-1 article to understand more about it.
• Regional Cloud: These are in-region from a user's perspective. In-region can refer to an individual country or geographic region from a cloud perspective. Using the same example as earlier for company ABC, if there is a requirement to stream videos on their private cloud, it will not be feasible to get a good user experience from a central location. The company might decide to build its regional cloud in the Philippines itself or in Singapore to cover it. Companies also use CDN cache servers at another cloud-providers location in the region to improve user experience.                 

2.    The difference in 4G vs 5G solution components?

The below table summarizes the difference in solution components that are required for 5G comparing to 4G. It’s a simplified view, each of these elements can be a detailed topic of discussion in itself.

• User Equipment: Mobile phones needs to be updated with the latest 5G chips for communication. Samsung, LG, Motorola & Huawei have launched few phones but most of these phones are in the high-end price range. Apple is supposed to launch it in Sep'20.
• Radio: 5G requires new radio and these are termed as Next Generation Node-B (gNB). Radios have got new features like Massive MIMO (Multiple Input and Multiple Output), 3D Beamforming, Spectrum sharing, and optimized OFDM. In simple terms, new radios will support massive bandwidth and ultra-reliable low latency communication. The new radio will keep on using the defined standard of NB-IoT from LTE era for Massive connectivity
• Spectrum: As you can review from the table, the overall spectrum has changed, and it can be simplified in three-band structures. Millimeter waves (mm-waves), low-band, and mid-band. MM-waves offer blazingly fast speed crossing 1Gbps marker over wireless connectivity, but it has a downside of less coverage area which can face interference indoors, structures, buildings. For coverage with mm-waves, dense radios have to be deployed in picocells. Low-band is better than 4G in speed and provides larger area coverage similar to 4G/LTE, while mid-band is a good trade-off between speed and coverage area. Carriers will be using a mix of each band to provide continued coverage with patches of a blazingly fast speed in dense areas.

Just for US users, this concept is interlinked with the naming schema that AT&T, Verizon, and T-Mobile have been using. AT&T calls their evolved LTE network as 5GE (technically it's not 5G) and AT&T ran into issues with naming. AT&T will offer low-band and mid-band based offerings with name 5G and mm-wave offerings with name 5G+. Verizon will be using name 5G-UWB and T-Mobile will be using 5G for offerings across all the spectrums.

• RAN: 5G uses the concept of Cloud RAN/centralized RAN to provide more cost-efficiency with increase in number of cell sites. As we saw the requirement of more radios with mm-wave, it'll be difficult to build out a complete cell site at each location, hence there is a requirement to have radios deployed in smaller cells aggregated at macrocell level. To make it cost effective for service providers, functionality of BBU has been split across two functions Distributed Unit (DU), and Control Unit (CU). RRH is commonly referred as Radio Unit (RU) in the solution as well. Another key concept that lot of vendors are working with RAN is Open RAN, which means that as a Service provider I can have flexibility to use these three logical functions by multiple vendor. It helps to break the model for incumbents with closed RAN and provides option for cost-efficiency. There are various models of how RAN could be deployed in the 5G scenario expanding the use cases for mobile backhaul networks to be split among Front-haul, mid-haul, and back-haul.

• Network Connectivity: Traditionally for 4G/LTE architecture, connectivity between Radio towers (cell sites) to Core or datacenters is referred to as Mobile Backhaul. The most common connectivity methods based on use cases and cost were Fiber Optics, Microwave, and Satellite backhaul. With 5G the concept of common mobile backhaul has been expanded to Front-haul, Mid-haul, and Back-haul using standard transport methods with IP over the optical network. The key intent of splitting the mobile back-haul is to provide cost-efficiency and aggregation of small radio cells with centralized RAN.
• Core: 4G/LTE used evolved packet core and 5G will require a new core that is built on services-based architecture supported in cloud-native format. 5G core will enable end to end slicing, flow-based QoS, and act as a converged core for multi-access. It'll be able to support cellular, WLAN, and fixed access for the users.
• Network Slicing: Network slicing refers to the concept of providing guaranteed SLA across the cellular network end to end for specific service. These SLAs could be latency, availability, or other quality of service parameters. It will enable service providers to offer differentiated services based on customer or application requirements, thus offering another revenue stream.
• Cloud: There is a new concept of Multi-Access Edge compute (Far Edge) and Edge Cloud has been introduced to support low latency requirements. The below image showcases a good comparison between various options and latency for applications from the access user equipment. The concept of Edge & Far Edge Cloud provides an option for service providers to expand in the application hosting domain which has been primarily dominated by public cloud companies like AWS, Azure, and GCP. That's one of the reasons that you are hearing multiple collaboration between large CSPs and public cloud providers in each country.

3. 5G Architecture

We touched upon all the basic concepts of elements that build 5G solution, below chart summarizes it in pictorial format:

4.    What are the challenges with the adoption of 5G?

Since we went through so many benefits of 5G, the obvious question to ask will be what we are waiting for. We have been hearing about 5G from 2016-2017, why things are moving so slow? Let's look at various challenges with the adoption of 5G:

• It requires massive investment to build new infrastructure for 5G which requires more radios, expansion of transport network, and automation capabilities.
• Spectrum has to be auctioned by governments for 5G and it has accelerated in the past 5 months with CV-19, but still rolling slowly.
• Building out new infrastructure will take time; expansion of the network and build out will require collaboration between city authorities and service providers.
• Use cases that can enable service providers to monetize the differentiated services are still limited. Innovation has been point focused rather an industry-wide, so, it's a chicken and egg situation.

5.    What is the upgrade path to 5G for service providers?

Before jumping to upgrade the path for service providers, let's look at two common deployment models for 5G, NSA (Non-Standalone), and SA (Standalone). As below image showcases NSA model of deployment includes using existing LTE eNB radios while core could be EPC or new 5G core. While using 5G core, evolved LTE can be offered using the spectrum sharing. One of the proposed paths for service providers to move to 5G is showcased below:

Hope this article was able to connect majority of dots from 5G solution architecture perspective. Next focus will be 5G Security itself and change in the landscape.