It is natural for us to take notice when a celebrity raises a topic of global interest and takes the matter to court. This is about Indian actress Juhi Chawla taking 5G deployment in India to Delhi High Court. As of publishing this article, the court has dismissed the petition and the actress is no longer against 5G deployment.

5G trials will start in India soon and it merits to look into the concerns highlighted in the petition and the advantages of 5G in Indian context. Many well-known online web portals have highlighted key points from the 5000-page petition.

I have spent considerable amount of my career in top wireless organizations like Qualcomm and Intel before founding DTRI, a wireless education company. I base this article from personal experience and the points that I picked up from this case.

Before I address key concerns from the petition, let us review a simplified cellular network as shown in Figure-1. It has 3 major components.

• Base station or what is also called as mobile tower or tower
• User Equipment (UE) or also called as handset or the mobile phone but could be any thing in IoT context
• The invisible wireless communication link which connects the tower and the UE

One of the major concerns raised by the petition is about excessive radiation by the tower and its negative impact on environment. Since the radiation is invisible there is a fear of unknown!

While the cellular network shown above is similar whether it is 5G, 4G, 3G or even 2G, it seems as a society we have accepted all ‘Gs’ except 5G. Today without 4G we have to give up smart phones and all the useful and entertaining applications like Amazon, Netflix, Tiktok and so on. Even a simple phone call with a basic mobile handset requires 2G network. Popular technologies like WIFI, Bluetooth, GPS, all use wireless communication. This implies that the two major components of the network – UE and the wireless communication link is not perceived as a problem by the society.

The concern is about the mobile tower, a 5G tower to be specific. The petition claims that 5G radiation levels are 100 times more than the current cellular radiation levels [1]. 3GPP, which is the specifications body for both 4G and 5G technologies shows no such difference in radiated power from the mobile tower [2]. But things could change with MIMO (multiple antenna technology). Compare the light coming out of an electric bulb and a torch light using two similar AA batteries as shown in Figure-2.

Imagine MIMO to the torch light which focuses energy in a particular direction vs. SISO (single antenna technology) system which is like the bulb emitting dispersed energy. MIMO is part of 4G but in 5G, the signal is much more focused on a particular UE due to massive MIMO. This focused beam energy can be 10 times higher than 4G. This is akin to comparing torch light with a laser pointer as shown in Figure-3.

Does it mean 5G radiations are more dangerous than 4G? This is where regulatory bodies have to step in. Consider the case of FCC, the regulatory agency in USA. FCC has specified ERP (maximum focused radiation in a direction) under Title 47 of CFR for radiating towers. The specifications are based on factors like frequency of operation, height of the tower and the population density in the region. Even though the torch light is more focused than the laser light both have an upper (maximum) limit on brightness. Whether it is 4G or 5G, MIMO or massive MIMO radiation upper limit is not violated as per the law.

The cellular network operators (Example: BSNL, JIO, Airtel) do not operate the base stations with maximum radiated power. Maximum power operation implies network inefficiency and a direct hit on the revenue. A typical 4G LTE network operates at 12% of maximum power for 90% of the time in a 24-hour duration [3]. Thus, a tower which is capable of radiating 100 watts of power is radiating only 12 watts for 90% of the time. Thus, the radiation is not intense and full blast 24/7.

So far, we looked into power radiation. Another concern is about the frequency of operation. 3GPP specifications define 5G deployments below 7GHz (currently <6GHz). This is frequency range-1 of the spectrum and same as 4G technology. Frequency range-2 is specific to 5G and not defined for 4G. In this range the network operation is >24GHz called the milli-meter wave (mmWave) communication as shown in Figure-4.

Milli-meter wave signals cannot travel farther (range <1km) in practical cases. The tower and mobile phone have to be in line of sight to overcome environment losses and for effective communication. Thus, mmWave in practical mobile phone communication can happen when the tower and UE are very close to each other. When closer, the tower (also called micro/pico base station) has to radiate power about 100 times lower than the regular huge towers (called macro base stations). MmWave is good for short-range applications like indoor communication. It can be an alternate to WIFI in commercial complexes, apartments, hostels and private networks.

So far, we addressed the power and spectrum perspectives of 5G. If current 5G implementation is almost comparable to 4G then it is the right time to question why 5G?

The fundamental assumption is that 5G is the next version of 4G and that we will switch from 4G phones to 5G phones. For want of faster download speed the cellular communication generations progressed from 2G to 4G. This is not the only reason to move to 5G. Further, mobile phone communication is not the only 5G use case but one of the many use cases. Recent 5G progress is very visible due to new 5G phone release advertisements that we see in media.

Mobile phone as an early 5G use case is due to following major factors:

• Mobile phone is a huge market and easy to convince B2C customers to move to 5G than B2B customers. B2C customers in the past progressed from 2G to 3G to 4G with attractive new phones and low-cost data.
• Mobile phone market also provides enormous and valuable data to operators to improve 5G network efficiency in general. This data is critical for the 5G stakeholders to move the market towards 5G.
• Use cases in 5G are plenty but revenue generation is a challenge. Example: IoT is a big market but fragmented with various vendors and pieces to fit a large puzzle. Entire IoT ecosystem of hardware and software is not standardized. Industrial IoT is a big space to enter but not until B2B customers see RoI for million+ $ investment in 5G.

Above points do not undermine recent advances in autonomous driving, industrial IoT and private networks which in fact are practical use cases of 5G.

Coming back to why 5G it is important to note that 5G is not only about high-speed internet but has 3 focus areas for communication:

• Highly-reliable and low delay network (URLLC) for mission critical services
• A massive network of low-powered, low-data rate devices (mMTC)
• A network offering high speed internet (eMBB)

These 3 focus areas together form the Trimurti of 5G communication as shown in Figure-6.

URLLC (Ultra-Reliable Low Latency Communication)

A URLLC network transfers information with acceptable QoS (>99.9999% reliability) and lowest delay (<1milli-second). The specifications are defined by organizations like 3GPP. An adequate and functional healthcare infrastructure is evident during this pandemic. Government aims to spend crores of rupees in setting up good clinics in remote areas. But recruiting and placing well qualified doctors in those places is a challenge. As per WHO report there are only about 40% of healthcare professionals in rural India which has about 70% of the population. When it comes to specialists this %age drops further [4]. Pre-pandemic, tele-medicine was not preferred both by doctors and patients alike due to obvious reasons. During this pandemic life changed. Both parties are now open to tele-medicine. This can be a boon for patients who are not living in cities and yet can consult with best doctors located anywhere in India [5]. Today’s tele-consultation is limited to audio/video calls. This opens up more possibilities for entrepreneurs in creating new products in advanced medical procedures like robotic surgery [6],[7]. Some hospitals like Apollo are already into robotic surgery. Robotic surgery requires high precision. This mandates that the network is ultra-reliable (lowest errors) and offers least delay, features which are part of 5G technology.

mMTC (massive Machine Type Communication)

Interconnecting a massive number of low power consuming (Example: battery operated devices) in a IoT system is another focus area of 5G. In this scenario the devices do not demand high speed internet or need large data upload/downloads. Consider the case of smart meters for recording home power consumption and billing [8]. Smart meters improve efficiency for power supply companies (Example: BESCOM in Bengaluru). It also reduces bill amount for consumers. Current smart meters use GSM technology. Indian government is on a mission to convert existing analog/ digital meters to smart meters across India. The push is to move from GSM to 4G NB-IoT technology. These meters can finally adopt robust and secure communication technology like 5G. At present there are 10+ Indian states where smart metering is either implemented or in pilot stages [9].

eMBB (enhanced Mobile Broad Band)

High-speed internet is a need for entertainment, gaming and shopping applications. During pandemic online education became a necessity. Educational gap is noticed due to digital divide and the resulting disadvantage to rural schools. There are various for-profit organizations who have built a fortune over online education. To overcome the educational gaps there are many not-for-profit organizations. Example: eVidyaloka (www.evidyaloka.org) a NPO offers live teaching to students in rural schools. This requires a good and stable internet connection. From past few years, service providers like BSNL, JIO and Airtel provide high-speed connectivity to remote areas. I hope education takes precedence over digital and geographical divide.

Concluding…

Killing someone with a kitchen knife is a real possibility but that does not mean government bans selling and using knives. If 5G or any electromagnetic radiation is found to be detrimental to flora, fauna and humans then we researchers, engineers and the government have further work to do. Let us put a sign work in progress and get back to our drawing board.

References

[1] https://gadgets.ndtv.com/telecom/news/juhi-chawla-5g-case-lawsuit-dismissed-fine-penalty-rs-20-lakh-delhi-high-court-2456540

[2] www.3gpp.org, Specification #: 37.145-2

[3] Measurements of downlink power level distributions in LTE networks, IEEE Xplore

[4] https://www.who.int/hrh/resources/16058health_workforce_India.pdf

[5] https://www.news18.com/news/india/telemedicine-services-become-boon-in-chhattisgarhs-naxal-affected-dantewada-3831668.html

[6] https://gadgets.ndtv.com/science/features/robot-assisted-surgeries-important-india-covid-19-pandemic-5g-surgeon-2268786

[7] https://www.businesstoday.in/sectors/pharma/indias-first-general-robotic-surgery-system-to-hit-markets-in-4-6-months/story/432488.html

[8] https://energy.economictimes.indiatimes.com/news/power/eesl-announces-installation-of-10-lakh-smart-meters-across-india/74288317

[9] https://www.smart-energy.com/industry-sectors/smart-meters/2-34-million-smart-prepaid-electricity-meters-for-indias-bihar-state/

The I and Q paths in a quadrature system has its own mixers, filters for processing the signal. An LTE signal of BW 20MHz refers to this quadrature or complex signal bandwidth where individual I and Q paths carry signal within a bandwidth of 10MHz and when combined provide the total 20MHz bandwidth. For each of the paths with 10MHz bandwidth the sampling rate of 30.72MHz very well exceeds (3x) the Nyquist sampling rate.

The second question can be addressed by recalling the LTE transmitter and receiver design which is based on OFDM and how the sub-carriers are generated. Consider the case of OFDM transmitter. The inverse discrete fourier transform (IDFT) or the efficient form of DFT, the inverse fast fourier transform (IFFT) is used to generate multiple sub-carriers. Consider the IDFT equation shown in Equation-1.

f_spacing in Equation-2 gives the spacing between 2 neighboring frequencies in a N frequency system. m is an integer which goes from 1 to N which gives the index of each frequency point.

Consider an LTE signal with BW="20MHz" and sub-carrier spacing (SCS) of 15kHz. The number of sub-carriers within 20MHz BW spaced at 15kHz is calculated by dividing the BW by SCS which gives 1333.33 sub-carriers. This value is higher than the actual number of sub carriers specified by 3GPP specifications for LTE (1200 sub-carriers) and 5G-NR (1272 sub carriers). Equation-1 is used to generate these sub-carriers but the actual implementation uses radix-2 FFT where the number of frequency points in FFT should be a power of 2. Thus, to generate 1200 sub-carriers, 2¹¹ FFT is used. This gives the value of N as 2¹¹ or 2048 sub-carriers.

Rearranging Equation-2 as below:

In OFDM transceiver, identifying f_spacing as SCS which is 15kHz, N="2048" and m="1" (always use 1 since there is no indexing in this context) the sampling rate is calculated to be f_s=30.72MHz which answers the second question.

Equation-3 can be applied to calculate sampling rates for other LTE and 5G-NR BW and SCS cases as shown in Table-1.