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5G millimeter wave tutorial | what is 5G millimeter wave

This 5G millimeter wave tutorial covers basic features of 5G millimeter wave technology, 5G mm wave advantages and disadvantages and 5G millimeter wave frame structure. It mentions links to 5G mm wave frequency band and 5G channel sounding.

About 5G: To achieve higher data rate requirement in the order of 10 Gbps, 5G technology has been developed. The specifications are published in the 3GPP Release 15 and beyond. 5G has different frequency ranges sub 6 GHz (5G macro optimized), 3-30 GHz (5G E small cells) and 30-100 GHz (5G Ultra Dense).

About millimeter wave: The frequency bands which lies between 30 GHz to 300 GHz is known as millimeter wave. This is due to the fact that wavelength of electro-magnetic wave will be in millimeter range at these frequencies. There are many advantages and disadvantages of mm wave.

Due to growth of large number of mobile data subscribers, need for larger bandwidth arises. The fact is bandwidth is limited in the available mobile frequency spectrum which is below the mm wave band. Due to this millimeter wave band has been explored as mobile frequency spectrum by operators due to its support for larger bandwidth. Though penetration loss is higher at these mm wave frequencies as these frequencies can not penetrate walls and certain objects in the buildings. Moreover mm wave frequencies get attenuated due to rain. After careful inclusion of all these factors in the RF link budget calculation, mm wave can be strong future for the mobile data broadband market.

About 5G millimeter wave: The millimeter wave frequencies which are used for 5G mobile technology is known as 5G millimeter wave.

5G millimeter wave technology features

Following table mentions features of 5G millimeter wave technology.


Features Description
Data rate 10 Gbps or higher
Frequency Bands The bands are split into <40 GHz and >40GHz upto 100 GHz frequency
Frequency Bands➤
Bandwidths • 10 subcarriers of 100 MHz each can provide 1GHz BW due to carrier aggregation at <40 GHz • 500 MHz to 2 GHz BW can be achieved without carrier aggregation at >40GHz
Distance coverage 2 meters (indoor) to 300 meters (outdoor)
Modulation types CP-OFDMA <40GHz
SC >40GHz
Frame topology TDD
latency About 1 ms
MIMO type Massive MIMO is supported. Antennas are physically small and hence there will be approx. 16 antenna array available in 1 square inch. Hence 5G mm wave compliant eNBs support 128 to 1000 antenna arrays. These are used to increase the capacity and coverage both. Refer Massive MIMO basics➤.

For frequencies above 40 GHz, Single carrier modulation is used to permit higher PA efficiency and efficient beamforming. It minimizes switching overhead too. In Null CP SC type, regular CPs are replaced with null CPs. This provides constant envelope in the modulated waveform.

5G millimeter wave frame structure | 5G mm wave frame

5G millimeter wave frame structure

The figure-1 depicts proposed 5G mm wave frame structure. As shown DL refers to downlink transmission from eNB to UEs and UL refers to uplink transmission from UEs to eNB. As shown control and data planes are separate, which helps in achieving lesser latency requirements. This is due to the fact that processing of control and data parts can run in parallel.
Refer 5G mm wave frame➤.

Symbol Table or numerology used in 5G

Following table mentions probable numerology for two FFT points used in 5G millimeter wave technology viz. 1024, 2048 and 4096.


FFT Size 1024 FFT Point (70 GHz) 2048 FFT Point (3 to 40GHz) 4096 FFT Point
Carrier Bandwidth 2000 MHz 200 MHz 200 MHz
Subcarrier spacing 1.5 MHz 120 KHz 60 KHz
Symbol Length 666.7 ns 8.335 µs 16.67 µs
Number of syms/frame 14 14 14
CP (Cyclic Prefix) duration 10.4 ns 0.6 µs 1 µs

Advantages of 5G millimeter wave

Following are the advantages/merits of the 5G millimeter wave. These benefits make 5G in millimeter wave as one of the strong contender for the future of mobile wireless communication domain.
• Provides larger bandwidth and hence more number of subscribers can be accommodated.
• Due to less bandwidth in millimeter range, it is more favourable for smaller cell deployment.
• Coverage is not limited to line of sight as first order scatter paths are viable.
• channel sounding feature is employed to take care of different types of losses at mm wave frequencies so that 5G network works satisfactorily. Channel sounding refers to measurement or estimation of channel characteristics which helps in successful design, development and deployment of 5G network with necessary quality requirements.
• Antenna size is physically small and hence large number of antennas are packed in small size. This leads to use of massive MIMO in eNB/AP to enhance the capacity.
• Dynamic beamforming is employed and hence it mitigates higher path loss at mm wave frequencies.
• 5G millimeter wave networks support multi-gigabit backhaul upto 400 meters and cellular access upto 200-300 meters.

Due to these benefits, 5G mm wave is suitable for mobile communication over sub-6GHz wireless technologies.

Disadvantages of 5G mm wave

Following are the disadvantages/demerits of the 5G millimeter wave.
• Millimeter wave goes through different losses such as penetration, rain attenuation etc. This limits distance coverage requirement of mm wave in 5G based cellular mobile deployment. Moreover path loss at mm is proportional to square of the frequency. It supports 2 meters in indoors and about 200-300 meters in outdoors based on channel conditions and AP/eNB height above the ground.
• Supports only LOS (Line of Sight) propagation. Hence coverage is limited to LOS.
• Foliage loss is significant at such mm wave frequencies.
• Power consumption is higher at millimeter wave due to more number of RF modules due to more number of antennas. To avoid this drawback, hybrid architecture which has fewer RF chains than number of antennas need to be used at the receiver. Moreover low power analog processing circuits are designed in mm wave hardware.
These disadvantages need to be considered during 5G millimeter wave link budget calculation. This is very much essential for successful 5G millimeter wave deployment.

REFERENCES

Note: As the 5G mm wave standards have been under development there might be changes to the numerology and frame structure mentioned on this page. We request to kindly refer latest updates on 5G specifications as available from 3GPP and related sites as mentioned below.
http://www.5gworkshops.com/5GCM.html
https://5g-ppp.eu/



5G millimeter wave related links

Following are the sub topics on the 5G technology:
5G basic tutorial
5G mm wave frame
5G millimeter wave channel sounding
Difference between 4G and 5G
5G testing and test equipments
5G network architecture

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