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Mobile Communications Lecture Notes

Overview

Cool table

Wireless Telecommunication Systems

GSM

Description: First successful digital cellular standard achieving global interoperability. Used 8-slot TDMA frames with Gaussian Minimum Shift Keying (GMSK) modulation. Introduced SIM cards, international roaming, and established the foundation for all subsequent mobile generations.

IS-95

Description: First commercial CDMA system using spread spectrum technology with 1.25 MHz channels. Pioneered soft handoff, variable-rate vocoders, and power control. Provided better capacity and coverage than TDMA systems but had limited global adoption.

TETRA

Description: Professional mobile radio standard with 4-slot TDMA, group communications, and direct mode operation. Features end-to-end encryption, fast call setup (<150ms), and mission-critical reliability. Supports both trunked and direct mode communications.

GPRS

Description: Overlay packet-switched network on GSM infrastructure enabling "always-on" data connectivity. Introduced four coding schemes (CS-1 to CS-4) and dynamic timeslot allocation. Enabled mobile internet access and was crucial for early smartphone adoption.

EDGE

Description: Enhanced GSM/GPRS using 8-PSK modulation instead of GMSK, tripling spectral efficiency. Introduced link adaptation and incremental redundancy for improved error handling. Provided the data rates needed for early mobile multimedia services. EDGE was designed as a bridge between GSM (2G) and UMTS (3G), allowing higher data rates on existing GSM networks before full UMTS development.

3rd Generation

The 3rd Generation is defined by certain requirements, its not a certain technology, but technology that can fulfill these requirements when it comes to data rates:

Idea was: a single system covering the globe (didnt happen).
IMT-2000 (a global standard for 3rd gen defined by the ITU (International Telecommunication Union)) symbolizes: should start around the year 2000, but also should operate around 2000Mhz.
Before we've had the 3G systems, the ITU said "these are the goals, now please different standardization bodies, companies, propose systems for that". There were different ultrawideband systems, cdma2000, other CDMA systems, and, ETSI came up with UMTS. UMTS is an example for a 3G system, it is not the only system, but the most successful. UMTS consists of UTRA (Universal Terrestrial Radio Access), for the radio access. UMTS was an enhancement of GSM.
So: The ITU set some goals and requirements, but also came up with certain frequencies (Slide 4.72), but left implementation details and technology choices to regional and national bodies.

IMT-2000

Description: ITU framework defining requirements for 3G systems including 2 Mbps for stationary/indoor, 384 kbps for pedestrian, and 144 kbps for vehicular environments. Encompasses UMTS, CDMA2000, and other 3G technologies under unified specifications.

UMTS

Description: European 3G standard using 5 MHz W-CDMA channels with soft handover and variable spreading factors. Introduced packet-switched core network alongside circuit-switched domain. Enabled video calling, mobile internet, and multimedia services with QoS differentiation.

WCDMA

Description: Air interface for UMTS using 5 MHz channels with chip rate of 3.84 Mcps. Features variable spreading factors (4-512), fast power control (1500 Hz), and Rake receivers. Supports both FDD and TDD modes with advanced antenna techniques.

CDMA2000

Description: Evolution of IS-95 with backward compatibility, featuring 1.25 MHz channels and multi-carrier options. Includes 1xRTT for voice/data and 1xEV-DO for high-speed data. Used advanced techniques like HARQ, AMC, and multi-user diversity scheduling.

HSDPA

Description: UMTS enhancement using adaptive modulation (QPSK/16-QAM), fast scheduling, and HARQ with 2ms TTI. Introduced shared channel concept with up to 15 parallel codes. Significantly improved spectral efficiency and user experience for data services.

LTE/LTE Advanced

Description: All-IP flat architecture using OFDMA with flexible bandwidth (1.4-20 MHz). Features MIMO, carrier aggregation (LTE-A), and low latency (~10ms). Introduced eNodeB concept and VoLTE for voice services. Foundation for modern mobile broadband.

5G/6G

Description: 5G: Service-based architecture with network slicing, massive MIMO, and mmWave frequencies. Three service categories: eMBB, mMTC, and URLLC with <1ms latency. 6G: Vision includes AI-native networks, holographic communications, and integrated sensing/communication.

Misc

Near-far effect

In the UTRA-FDD of UMTS, MSs far away from the BS will have a weaker signal at the BS than MSs close to the BS. That means, the signal is "drowned" by the MS that is closer to the BS. Thats the near-far effect.
The solution in UTRA-FDD is power control, which tells MSs far away to transmit stronger, and MSs closer to transmit weaker. The goal is to have all signals from the MSs to arrive with the same strength at the BS. They are differentiated by CDMA.