5G Core: Telecom Basics

5G Core Training Introduction

• The 5G core training assumes some familiarity with previous generations of mobile networks (2G, 3G, 4G).
• The course aims to bridge the gap for individuals without prior knowledge of wireless communication.

Circuit Switching

• Circuit switching reserves physical resources for a dedicated connection between two points.
• Analogy: A separate road is assigned for a trip from Delhi to Gurgaon, ensuring smooth travel.
• Historical context: In old movies, telephone exchanges manually switched calls.
• Landline connections and early 2G calls used circuit switching for high quality.
• Time division and frequency division were introduced to allow more users to utilize resources.

Packet Switching

• Packet switching is like a normal road where no resources are reserved.
• Call quality can be impacted due to shared resources (e.g., WhatsApp calls).
• Delay can occur as network elements use any possible route to send data packets.
• Packet switching allows efficient use of network resources and accommodates more users.
• Circuit switching establishes a physical path, while packet switching does not.
• In circuit switching, all messages use the same path, and bandwidth is reserved.
• In packet switching, paths can vary for each message, and bandwidth is not reserved.

Evolution of Mobile Networks in India

• In the 1990s, India had a single landline provider, and the government controlled telecommunications.
• GSM networks were introduced in 1995.
• BSNL was created, and new licenses were issued to companies like Bharti, Spice Mobile, and MTNL.
• Reliance introduced affordable mobile phones in 2002, reducing call costs and removing incoming call charges.
• The telecom 2G scam arose after more licenses were given to companies like Videocon, Aircel, and MTS in 2008.
• In 2010, the government auctioned licenses for 3G and 4G spectrum.
• 3G services started in 2011, and 4G services after 2015.
• India's spectrum auction had the highest license cost globally.
• The base price for 5G spectrum is high, impacting the auctioning process.
• The Indian market is now dominated by 2-3 players due to financial losses of companies like Airtel and Vodafone.

Wireless Communication Standards

• 3GPP (Third Generation Partnership Project) was established in the late 90s.
• 3GPP created a reference architecture for 3G networks to enhance data speeds.
• ITU (International Telecommunication Union), part of the United Nations, governs telecommunication standardization.
• IEEE standardizes interfaces, ensuring compatibility across devices and network elements.
• GSMA (Global System for Mobile Communication) is a global system for mobile communication.
• GSMA is an association of GSM telecom operators that organizes the Mobile World Congress in Barcelona.

Evolution of Wireless Generations

• Wireless technology started with 1G, using analog voice.
• 2G (GSM) introduced digital technology with parallel technologies like CDMA.
• CDMA (Code Division Multiple Access) was used by the American army for secure communication.
• The first generation of CDMA for voice was called IS95A.
• 2.5G added data to voice with GPRS, providing wireless data services at around 114 kbps.
• A parallel technology for CDMA was CDMA IS95B.
• 2.75G or EDGE improved data speeds to 384 kbps using modulation techniques.
• GSM and CDMA technologies evolved to 3G without a 2.75G version for CDMA.
• 3GPP proposed WCDMA (Wideband CDMA) for 3G GSM technology, using a wide band to achieve speeds of 2 Mbps.
• 3GPP later introduced HSPA (High Speed Packet Access) to increase 3G speeds from 2 to 8 Mbps.
• The third generation of CDMA was called CDMA 2000, leading to HSPA+.
• 3.5G included CDMA EVDO (Evolution-Data Optimized) for enhanced video data output.
• TATA Docomo dongles and MTS (Russian operator) used CDMA EVDO for data services.
• In 2008, 3GPP launched LTE (Long Term Evolution) or fourth generation networks.
• CDMA evolution stopped after 3.5G or EVDO.
• WiMAX (Worldwide Interoperability for Microwave Access) was promoted by Qualcomm.
• A debate occurred in 2010 whether Indian operators should adopt WiMAX or LTE.
• BSNL deployed WiMAX, but most operators chose LTE due to their existing GSM-based infrastructure.
• WiMAX operators faced development and interoperability issues with GSM.
• LTE evolved to LTE advanced with speeds around 300 Mbps, then LTE advanced pro with speeds around 1 Gbps.
• 5G is the fifth generation of internet cellular standards.

2G Identifiers

• MSISDN (Mobile Station International Subscriber Directory Number) is the technical term for mobile numbers.
• In India, it starts with a country code followed by a 10-digit number.
• China has 11-digit mobile numbers.
• IMSI (International Mobile Subscriber Identity) is a unique identifier for each customer.
• IMSI is used by network elements to identify a customer, unlike MSISDN, which is used by people to dial numbers.
• IMSI is 15 digits long, starting with a 3-digit mobile country code (e.g., 404 for India), followed by 2 digits of mobile network code and 10 digits of the subscriber's serial number.
• IMEI (International Mobile Equipment Identity) identifies mobile equipment such as handsets, Apple Watches, or tablets
• IMEI has 14-15 digits with the first 6 digits identifying the manufacturer, the next 2 digits identifying the model, and the last 6-7 digits as the serial number.

Wireless Cell Sites

• A cell site is the area covered by a tower in wireless telecommunication, represented in a hexagonal shape.
• In 2G systems, operators purchased frequencies from the government for use in cell sites.
• Each cell site was assigned a frequency, accommodating about 8 people at one time.
• Sectorization was implemented to increase capacity by dividing cells into sectors to service more clients
• Cell sites were divided into 3 sectors of 120 degrees, using 3 frequencies.
• Using 4 sectors allow usage of 4 frequencies on a tower.
• Adjacent cell sites in 2G could not have the same frequency to avoid interruption.
• The same frequency could be reused if cell sites were separated by another cell site.
• 2G communication was standardized by ITU on 900 MHz, later expanded to 1800 MHz.
• India uses 2.1 GHz (2100 MHz) for 3G and 2300 MHz for 4G LTE.
• Lower frequencies provide broader coverage such as 93.5 red FM.
• 900 MHz band frequencies are more expensive than 1800 MHz frequencies.

2G Architecture

• GSM technology was used for 2G, primarily for calls and low-speed internet.
• A mobile phone connects to a tower, which is a supporting element.
• The antenna sends signals and connects to the mobile phone.
• The antenna, tower, and generator form the BTS (Base Transceiver Station).
• BTS, BSC, and MSC are key terms in telecommunication.
• BTS is the antenna combined with the tower acts as a base station.
• The antenna both sends and receives signals, acting as a transceiver.
• BSC (Base Station Controller) controls multiple BTSs.
• BTS is a "dumb device" controlled by the BSC.
• Mobile phones are technically referred to as MS (Mobile Station) or UE (User Equipment).
• The BSC governs frequency and time slot allocation for calls, including setting up and aligning channels.