--- title: "3G versus 4G mobile communication" subject: "Wireless Communication" chapter: 1 key: "semester_7/wireless_communication:3g-vs-4g" source: https://www.bctengineer.com/q/semester_7/wireless_communication/3g-vs-4g site: BCT Engineering --- # 3G versus 4G mobile communication Wireless Communication · Chapter 1: Introduction - Asked in: 2080 Baisakh, 4 marks; 2077 Chaitra, 5 marks (asked 2 times) - Video: [1g 2g 3g 4g 5g technology | MC | Mobile Computing | Lec- 05 | Bhanu Priya](https://www.youtube.com/watch?v=kxOUCDjHg_Q) — Education 4u - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/wireless_communication/3g-vs-4g - Whole chapter: https://www.bctengineer.com/md/semester_7/wireless_communication/chapter-1 ## Question Compare and contrast third and fourth generation of mobile communication standards in terms of technology advancement. ## Short answer 3G uses wideband CDMA with fixed 5 MHz carriers and circuit plus packet core, while 4G uses OFDMA/SC-FDMA with scalable bandwidth, MIMO and all-IP core. 4G gives up to 100 Mbps mobile and 1 Gbps fixed, lower latency about 10 ms, and VoLTE instead of circuit voice. ## Answer 3G (IMT-2000) introduced mobile data and multimedia using wideband CDMA, while 4G (IMT-Advanced) provides high-speed all-IP broadband using OFDMA and MIMO. | Feature | 3G | 4G | |---|---|---| | ITU family | IMT-2000 | IMT-Advanced | | Standards | UMTS/W-CDMA, CDMA2000, TD-SCDMA, HSPA | LTE-Advanced, WiMAX 2 (802.16m) | | Multiple access | Wideband CDMA | OFDMA downlink, SC-FDMA uplink (LTE) | | Bandwidth | 5 MHz (fixed) | Scalable 1.4–20 MHz, carrier aggregation up to 100 MHz | | Peak data rate | 384 kbps–2 Mbps (HSPA+ up to 42 Mbps) | 100 Mbps mobile, 1 Gbps stationary | | Core network | Circuit (voice) + packet (data) | All-IP packet core (EPC) | | Voice | Circuit-switched | VoIP (VoLTE) | | Latency | ~100 ms | ~10 ms | | Antenna | Mainly single antenna | MIMO (2×2 to 8×8) | | Modulation | QPSK, 16-QAM | QPSK, 16/64/256-QAM, adaptive | | Handoff | Soft handoff | Hard handoff | | Spectral efficiency | Low | High (several bit/s/Hz) | #### Main technology advancements in 4G 1. **OFDM** splits the wide channel into many narrow orthogonal subcarriers, so each sees flat fading; a cyclic prefix removes ISI, avoiding complex equalisers. 2. **MIMO** gives spatial multiplexing (higher rate) and diversity (reliability). 3. **Flat architecture** – the eNodeB includes radio control functions previously done by the RNC, reducing latency. 4. **Link adaptation and fast scheduling** (adaptive modulation and coding, HARQ). 5. **Carrier aggregation** and support for both FDD and TDD. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How does channel bandwidth differ between 3G and 4G? A. 3G is a fixed 5 MHz; 4G is scalable from 1.4 to 20 MHz, aggregated up to 100 MHz B. 3G is scalable; 4G is fixed 5 MHz C. Both are fixed at 200 kHz D. 4G uses 25-30 kHz channels Answer: A. WCDMA uses a fixed 5 MHz carrier; LTE scales and uses carrier aggregation. (Key point: Bandwidth) 2. Why does OFDM help 4G? A. It spreads each user over 5 MHz with codes B. It splits the wide channel into narrow orthogonal subcarriers so each sees flat fading, and a cyclic prefix removes ISI C. It removes the need for any base station D. It makes the network circuit switched Answer: B. Narrow subcarriers avoid frequency-selective fading and complex equalisers. (Key point: OFDM benefit) 3. What makes the 4G architecture 'flat' and lower latency? A. An RNC sits above every NodeB B. Voice stays in a circuit core C. The eNodeB includes radio control functions previously done by the RNC D. Every call goes through a circuit MSC Answer: C. Removing the RNC lowers latency to ~10 ms versus ~100 ms in 3G. (Key point: Flat architecture) 4. Which pair is correct for 3G versus 4G? A. 3G: soft handoff, circuit voice; 4G: hard handoff, VoLTE B. 3G: hard handoff; 4G: soft handoff C. Both use circuit voice D. 3G: VoLTE; 4G: circuit voice Answer: A. As in the table, 3G uses soft handoff and circuit voice, 4G hard handoff and VoIP. (Key point: Handoff and voice) ## Close variants set in other exams - [Comparison of 1G to 4G mobile standards](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Agenerations-1g-to-4g-comparison) — Wireless Communication, chapter 1, asked 6× ## Related in Wireless Communication - [Evolution of mobile communication up to 3G](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Aevolution-up-to-3g) — Wireless Communication, chapter 1, asked 3× - [Forward/reverse channel and 5G versus 4G](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Aforward-reverse-5g-vs-4g) — Wireless Communication, chapter 1, asked 2× - [Benefits of wireless communication and 4G](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Awireless-benefits-4g) — Wireless Communication, chapter 1 - [Trends in wireless communication beyond 3G](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Atrends-beyond-3g) — Wireless Communication, chapter 1 ## Related in other subjects - [Compare software models; propose a fourth model](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Asw-models-compare-fourth) — Instrumentation II, chapter 9 - [Report on advancement in science and technology](https://www.bctengineer.com/question.md?key=semester_5%2Fcommunication_english%3Areport-advancement-science-technology-nepal) — Communication English, chapter 9 - [Compare and contrast pollution in a city](https://www.bctengineer.com/question.md?key=semester_5%2Fcommunication_english%3Acompare-contrast-pollution-city-nepal) — Communication English, chapter 1