An Introduction to the 5G Frequency Spectrum

Posted by Peter Matthews on Sep 19, 2018 3:32:01 PM
Peter Matthews

Fifth Generation (5G) communication systems are being planned to enable a hundred-fold increase in user data-rates – and with this increase comes a need for significant increases in bandwidth over what is currently available.

Shannon Hartley

Why does bandwidth follow when we ask for an increase in data-rates? In 1948 Claude Shannon and Ralph Hartley, both researchers at Bell Labs, developed what has become known as the Shannon-Hartley Theorem. It tells us the maximum amount of error-free digital data that can be transmitted over a channel of a given bandwidth in the presence of noise:

shannon1

Where:

C = Channel Capacity in bits/second

M = Number of channels (e.g. the MIMO order)

B = Bandwidth in Hertz

S = transmit power, in Watts

N = noise on channel, in Watts

S/N = Signal to noise ratio

To increase Channel Capacity (data rates) we can Increase Bandwidth, Increase the number of channels, Increase transmit power (S) and Decrease the noise on the channel (N).

In order to achieve the data rates targeted by 5G systems, innovation is taking place on all of these fronts, but the factor in the equation we will discuss in this article is B, the Channel Bandwidth.

Questions of Bandwidth come naturally to looking at available spectrum – both because of questions of how much bandwidth is available in a given part of the spectrum, and because as frequency increases a given percent bandwidth gives us a greater share of spectrum.

LTE Spectrum

The 3GPP document TS 36.101 defines the LTE FDD and TDD bands. Version 14.5 defines 52 bands for 4G LTE spectrum, ranging in frequency from 450MHz (Band 31) to 5900MHz (Band 47).

The spectrum outlined in the standard is intended to support six channel bandwidths: 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz. To reach higher bandwidths (and thus higher data rates) a technique called Channel Aggregation (CA) is used to stitch together non-contiguous bands. TS 36.101 defines the bands available for CA.

Globally there are over 1000 band combinations supported. An overview of common frequency ranges in operation today can be seen below.

lte_map

In the US the major carriers have centered their activity around 11 bands:

Table 1, Key LTE bands in the U.S.

Band AT&T Verizon Wireless T-Mobile Sprint
Band 2, FDD UL, 1850 – 1910MHz  
Band 2, FDD DL, 1930 – 1990MHz  
Band 4, FDD UL, 1710 – 1755MHz  
Band 4, FDD DL, 2110 – 2155MHz  
Band 5, FDD UL, 824 – 849MHz      
Band 5, FDD DL, 869 – 894MHz      
Band 12, FDD UL, 699 – 716MHz    
Band 12, FDD DL, 729 – 746MHz    
Band 13, FDD DL, 746 – 756MHz      
Band 13, FDD UL, 777 – 787MHz      
Band 17, FDD UL, 704 – 716MHz      
Band 17, FDD DL, 734 – 746MHz      
Band 25, FDD UL, 1850 – 1915MHz      
Band 25, FDD DL, 1930 – 1995MHz      
Band 26, FDD UL, 814 – 849MHz      
Band 26, FDD DL, 859 – 894MHz      
Band 41, TDD, 2496 – 2690MHz      
Band 66, FDD UL, 1710 – 1780MHz      
Band 66, FDD DL, 2110 – 2200MHz      
Band 71, FDD DL, 617 – 652MHz      
Band 71, FDD UL, 663 – 698MHz      

Contiguous bandwidth of 100MHz is hard to find in the LTE spectrum landscape. Given that the peak data rate goal for 5G is 20Gbps (and the goal for LTE was 1Gbps) that 20x increase in channel capacity has to come from somewhere. Now as we mentioned above innovation is happening to address all of the variables in the Shannon Hartley model to get us there. A key innovation at the heart of 5G is utilizing new spectrum where increases in bandwidth are easier to come by.

5G spectrum

3GPP has been working on 5G for some time, and a major differentiator is the maximum bandwidths allocated to each channel. Where in 4G we had 20MHz maximum (and CA to stitch together more), in 5G we will have caps of 100MHz below 6GHz and 400MHz above 6GHz. Below 6GHz 400MHz will be achieved through CA (e.g. 4x 100MHz). In moving from 20MHz to 400MHz max, 3GPP have built the potential for a 20x increase in channel capacity right into the spectrum planning.

Here are some of the candidate 5G bands:

Table 2, Candidate 5G Bands.

Region Flow Fhigh Band
Korea 3400 MHz 3700 MHz  
26.5 GHz 29.5 GHz  
EU 2570 MHz 2620 MHz 38
3400 MHz 3800 MHz 42+43
24.25 GHz 27.35 GHz  
31.8 GHz 33.4 GHz  
40.5 GHz 43.5 GHz  
Japan 2496 2690 41
3400 3600 42
3600 4200  
4400 4900  
27.5 GHz 29.5 GHz  
US 2496 2690 41
3550 3700 48
27.5 GHz 28.35 GHz  
37 GHz 38.6 GHz  
38.6 GHz 40 GHz  
64 GHz 71 GHz  
China 2300 2400 40
2555 2655 41B
3300 3600  
3400 3600 42
4400 4500  
4800 4990  

With these new bands come groups of use-cases based on frequency. We can look at use cases that fall into frequencies below 1GHz, between 1GHz and 6GHz and those at the cm-wave and mm-wave frequencies.

Frequencies below 1GHz in the UHF perform well in applications that require long range and high data rates – these are the frequencies we are used to seeing in Macro base station applications. Moving forward to 5G they will be leveraged for lower data rate and narrow band applications (such as already used in 4G IoT applications) and are looked at for the ‘massive Machine to Machine Type Communications’ (mMTC).

From 1GHz to 6GHz we encounter the familiar LTE bands. This region is being looked at for use cases that need of the order of 100MHz of bandwidth, with the 2.5GHz Band 41 and 3.5GHz (42+43) regarded as candidates for 5G enhanced Mobile Broadband (eMBB) applications.

Starting at 28GHz we find the cm-wave and mmWave frequencies that are being utilized in Fixed Wireless Access (FWA) applications. It is these frequencies that are being deployed first, with demonstrations already having happened at the Winter Olympics in Korea in 2018.

The high end of the spectrum offers the most dramatic increase in available bandwidths, allowing designers to push Shannon-Hartley to incredible speeds.

You can learn more about 5G in general and what that means for filter technology on our 5G filter solutions page. Next take a look at our post on spectral efficiency in the context of wwWave microstrip filters.

Topics: Filter, 5G, mmWave

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