What is India’s 5Gi Standard And How Does It Address Rural 5G Needs?

The Indian standard on 5G (5Gi) has been accepted as one of the candidate technologies of 5G (IMT-2020) by ITU in Rec ITU-R (International Telecommunication Union- Radiocommunication Sector) M.2150. 3GPP (3rd Generation Partnership Project) is the other technology approved by ITU.

The 5Gi technology has been conceived to address India's specific need to cover remote and rural areas with less number of BTSs (Base Transmitting Stations), thus reducing the investment requirement and BTSs maintenance costs. It provides robust coverage for IOT (Internet of Things) in dense urban and large rural areas.

Indian companies, startups and academia made contributions to 5Gi technology. It is developed in collaboration between IITM, IIT Hyderabad, TSDSI (Telecommunications Standards Development Society, India) and CEWiT (Centre of Excellence in Wireless Technology). Technically this technology is called LMLC (Low Mobility Large Cell).

TSDSI

5G standards should incorporate India specific requirements and special use cases pertaining to our country. At the same time, we don’t want to become an island, creating exclusive technology standards. We want to work with global standards development organizations to help create global technology standards that incorporate India specific requirements. This will ensure that the equipment conforming to such global standards gets deployed, not only in India but in the large developing world. With this national mandate, TSDSI was founded on 07.01.2014 as National Telecom Standards Development Organisation (SDO).

The Indian Telecom Industry, comprising Telecom Service Providers (TSPs) and manufacturers, academia and R&D organisations came together to form TSDSI. This is in pursuance of government’s resolve, expressed in National Telecom Policy 2012, to create an Indian Telecom Standards Development Organisation, for contributing to next generation telecom standards and drive the ecosystem of IP (Intellectual Property) creation in India.

TSDSI started participating in ITU-R WP (Working Party) 5D meetings on 5G technology standards. 3GPP 5 G technology mainly focuses on eMBB (enhanced Mobile Broadband) and massive IOT. TSDSI members noted that test specifications proposed for eMBB service of 5G, didn't address Indian scenarios of usage and were dictated by dominant global needs. The rural eMBB test case was vehicular access at 120 kmph and ISD (Inter Site Distance) of 1.732 km. These conditions may be suitable for the developed world but not for India and other developing countries.

The Indian villages are population clusters of a few hundred or thousand people for every few km. Hence large cells are a must for serving rural users. Further, the high speed vehicular access is not that important in the Indian context. Hence TSDSI decided to propose LMLC test configuration with pedestrian mobility of 10 kmph.

ISD vis-a-vis per cent of villages covered

Base Station will be located at Gram Panchayat (GP), which has Bharatnet fiber connectivity for backhaul. This Base Station should serve nearby villages of GP. An ISD of 6 km, corresponds to a Cell radius of 3.46 km. With the BTS at the centre of the hexagonal Cell and with 3.46 km of distance from the centre, about 68 per cent of villages will be covered. An ISD of 8 Km corresponds to a Cell radius of 4.6 km. 4.6 km of distance from the centre, covers about 85 per cent of villages. Higher ISD corresponds to higher Cell radius, covering more area and more villages.

A decision on ISD was taken in the meeting of WP5D held in Canada in June 2017, where the value of ISD was agreed to as 6 km. 5Gi wass designed on top of 3GPP release 15 for LMLC, offering 6 km ISD.

5Gi- technology details

1. Modulation: π/2 BPSK (Binary Phase Shift Keying) with spectrum shaping: This leads to reduced PARR (Peak to Average Ratio) to the extent of 3 db and enhanced uplink (User Equipment (UE) to Base Station) coverage. For the same data rate and ISD, QPSK (Quadrature Phase Shift Keying) modulation requires twice the number of receiver antennas to maintain the same cell edge performance as π/2 BPSK, resulting in higher BTS costs. For the same data rate requirement, π/2 BPSK offers higher cell range (twice) and QPSK modulation results in very low data rates for some cell edge UEs.

2. Intelligent BWP (Bandwidth Part) configuration for Resource Block Group (RBG) based scheduling: This results in reduced Physical Downlink Control Channel (PDCCH) overhead and efficient signalling mechanism to improve spectral utilisation. This also provides additional granularity in the UE frequency scheduling.

3. Low latency precoded Sounding Reference Signal (SRS) transmission: Resulting in Improved performance in varying mobility scenarios, especially at higher speeds.

4. Optimizing PTRS (Phase Tracking Reference Signal) density through intelligent threshold parameters: leading to near optimal overhead and better performance, particularly in mmWave frequency band (24- 29 GHz).

Benefits of 5Gi

5Gi supports developing countries in deploying cost effective 5G networks, with large coverage, enabling affordable 5G services. It improves spectral efficiency. The average spectral efficiency is 3.3 bits/Hz/TRxP (Transmission Reception Point) for down link (Base Station to UE) and 1.6 for uplink. Handles higher traffic at no extra cost. Improved performance just with software changes. Globally inter- operable and compatible. Improved building penetration for NB (Narrow Band)-IOT, which is Important for Smart Cities mission, at no extra cost.

Challenges in implementation of 5Gi in India

The Indian Telecom industry is dependent on global suppliers for supply of telecom equipment. The suppliers were showing reluctance in implementing 5Gi technology because of additional efforts required, cost involved, economy of scale and complexity in maintaining two 5G technologies. Our constant pursuance paved the way to include 5Gi technology in 3GPP specification and make it a global standard.

Merging of 5Gi and 3GPP 5 G standards

The global stakeholders agreed for merger of 5Gi technology requirements with 3GPP 5G standards to enable enhanced coverage to benefit rural and remote areas globally. TSDSI’s 5Gi standard has now been formally merged with the 3GPP 5G standard and implemented into the 3GPP Rel-17 NR (New Radio) specifications. 3GPP RAN (Radio Access Network) approved two Rel-17 Change Requests (CRs), that enables the π/2 BPSK waveform with filtering to be implemented in the 5G Networks.

Way forward

‘India lives in its villages’ as 70 per cent of the country's population resides in villages. Meeting the requirements of the village population is the bedrock of our country's development. So, the technology (pertaining to any sector), introduced in our country, should be tailored to meet the rural population requirements. The indigenous technology will definitely take into account the rural India requirements and that is one of the benefits of Atma Nirbharta. 5Gi is an exciting opportunity to endorse and support technologies for rural cell coverage. Fundamentally it focuses on rural connectivity. It looks at the design of pilots and control channels. Now 5Gi is part of the global standard and a pride for India. It is for the first time in the history of telecommunications that the Indian standard has been accepted by ITU!

(The author is Former Advisor, DOT, Government of India, Bangalore.)