5G Technology Components: Spectrum (1/5)

In our last post "5G Technology Components", we had discussed about the 5G Technology Components. This blog series will cover the main changes brought in the Spectrum aspect and how it helps 5G deliver high speed data throughput.

5G radio is designed for flexible spectrum utilization to take advantage of all available spectrum options from 400MHz to 90 GHz including licensed, shared access and unlicensed, Frequency Division Duplex (FDD) and Time Division Duplex (TDD) bands, and narrowband and wideband allocations. 

Following are the Spectrum options which 5G can utilize, along with the use cases it will be used to serve.

• Millimeter wave spectrum above 20 GHz can provide bandwidth even above 1 GHz, which allows a very high data rate up to 20 Gbps and extreme mobile broadband capacity. Millimeter waves are mainly suited for local usage like mass events, outdoor and indoor hotspots and fixed wireless use case.

• Spectrum at 2.5–5.0 GHz will be used for 5G coverage and capacity in urban areas by reusing the existing base station sites.The spectrum around 3.5 GHz is attractive for 5G because it is available globally, and the amount of spectrum is high. The bandwidth is typically up to 100MHz per operator at that frequency. 5G coverage at 3.5 GHz can be comparable to LTE1800 coverage if massive Multiple Input Multiple Output (MIMO) beamforming is used. 

• Low FDD bands are needed for wide area rural coverage, ultra-high reliability, and deep indoor penetration. Extensive coverage is important for the new uses cases like IoT and critical communication.

In the next blog, we will discuss about the changes related to Bandwidth and how it helps 5G in delivering high data rates.

5G Spectrum

5G radio is designed for flexible utilization of all available spectrum options from 400MHz to 90 GHz including licensed, shared, and unlicensed; FDD and TDD duplexing; and narrowband and wideband allocations. 

Following are the three main spectrum options:

The millimeter wave spectrum above 20 GHz can provide wide bandwidth up to 1–2 GHz, which ramps up the data rate to a very high 5–20 Gbps for extreme mobile broadband capacity. Millimeter wave is mainly suited for local usage like mass events, outdoor and indoor hotspots, and fixed wireless use case. Millimeter wave can also be used for offloading traffic from the low band in the busy hotspot areas. One use case for millimeter wave is providing very high capacity to public transport systems like trains or trams.

 

The mid-band spectrum at 2.5–5.0 GHz will be used for 5G coverage and capacity in urban areas by reusing existing base station sites. The spectrum around 3.5 GHz is attractive for 5Gbecause it is available almost globally, and the amount of bandwidth can go up to 100MHz or more per operator at that frequency. The peak data rate is 2Gbps with 100MHz bandwidth and 4×4 MIMO. 5G coverage at 3.5 GHz can be similar to LTE1800 coverage if massive MIMO beamforming is used.

Low bands below 3 GHz, for FDD, are needed for wide area rural coverage, low latency and high reliability, and for deep indoor penetration. Extensive coverage is important for the new use cases like IoT and critical communication. The low band could be 700MHz, which was made available in many countries at the same time as 5G. Another option is 900MHz, which is mostly occupied by 2G and 3G today, or 600MHz in the United States. Any other FDD bands can also be refarmed to 5G. LTE and 5G can be deployed on the same band using a dynamic spectrum sharing solution, which makes the refarming a smooth process.

Following are the Global 5G spectrum options.

The mid-band spectrum between 2.5 and 5.0 GHz can be found in most countries as well as the millimeter wave spectrum in a growing number of countries. The first 3GPP phase for 5G provides support up to the 52.6 GHz frequency range, and higher frequency bands will be addressed in later 5G releases. At low bands, 5G can utilize new 600 or 700MHz allocations, or do refarming of the existing bands. 5G can combine multiple bands together to boost the performance beyond what is achieved with just a single band. The solution can be carrier aggregation or dual connectivity.

5G Technology Components

The targets of 5G networks are beyond the capabilities of existing mobile networks.

Several new technologies are needed to fulfill all those targets. The main new technology components of 5G are:

1. New spectrum. 5G is the first mobile radio technology that is designed to operate on any frequency band between 400MHz and 90 GHz. The low bands are needed for coverage and the high bands for high data rates and capacity. The initial 5G deployments use Time Division Duplex (TDD) between 2.5 and 5.0 GHz, Frequency Division Duplex (FDD) below 2.7 GHz, and TDD at millimeter wave at 24–39 GHz.

 

2. Massive Multiple Input Multiple Output (MIMO) beamforming can increase spectral efficiency and network coverage substantially. Beamforming is more practical at higher frequencies because the antenna size is comparable to the wavelength, and the antenna size becomes smaller at higher frequencies. In practice, massive MIMO can be utilized at frequencies above 1 GHz in the base stations and at millimeter wave even in the devices. Massive MIMO will be part of 5G specifications and deployments from day 1.

 

3. Network slicing. Physical and protocol layers in 5G need flexible design to support different use cases, different frequency bands, and to maximize the energy and spectral efficiency. Network slicing will create virtual network segments for the different services within the same 5G network. This slicing capability allows operators to support different use cases and enterprise customers without having to build dedicated networks.

 

4. Dual connectivity and LTE coexistence. 5G can be deployed as a stand-alone system, but more typically 5G will be deployed together with LTE in the early phase. A 5G device can have simultaneous radio connections to 5G and to LTE. Dual connectivity can make the introduction of 5G simpler, can increase the user data rate and improve reliability. 5G is also designed for LTE coexistence, which makes spectrum sharing feasible and simplifies spectrum re-farming.

    

5. Cloud Optimized Architecture. The current architecture in LTE networks is fully distributed in the radio and fully centralized in the core network. The low latency requires the content to be brought close to the radio, which leads to local breakout and edge computing. Scalability requires the cloud benefits to be brought to the radio networks with edge cloud architecture. 5G radio and core networks are specified for native cloud implementation, including new interfaces inside the radio network.