This set of Wireless & Mobile Communications Interview Questions and Answers focuses on “Second Generation (2G) Cellular Networks”.
1. Which of the following multiple access techniques are used by second generation cellular systems?
a) FDMA/FDD and TDMA/FDD
b) TDMA/FDD and CDMA/FDD
c) FDMA/FDD and CDMA/FDD
d) FDMA/FDD only
Explanation: First generation cellular system used FDMA/FDD techniques. Second generation standards uses TDMA/FDD and CDMA/FDD multiple access techniques. 2G networks are digital.
2. Which one is not a TDMA standard of second generation networks?
Explanation: GSM (Global System Mobile), IS-136 (Interim Standard 136) and PDC (Pacific Digital Cellular) are the three most popular TDMA standards of second generation. AMPS is a first generation standard.
3. Which of the following is a CDMA standard of second generation network?
Explanation: Interim Standard 95 (IS-95) is the most popular CDMA standard of second generation networks. IS-136 is a TDMA standard of 2G. EDGE is a standard of 2.5G and ETACS is a 1G standard.
4. Popular 2G CDMA standard IS-95 is also known as ______
Explanation: The popular 2G CDMA standard, Interim Standard (IS-95) is also known as CdmaOne. The 2.5G CDMA standard, IS-95B is called CdmaTwo. And IS-136 is a TDMA standard for 2G.
5. How many users or voice channels are supported for each 200 KHz channel in GSM?
c) Sixty four
Explanation: GSM is a circuit switched system that divides each 200 KHz channel into eight 25 KHz time slots, i.e. each radio channel is divided into eight voice channels.
6. How many voice channels are supported for each 30 KHz radio channel in IS-136?
Explanation: Interim Standard 136 (IS-136) was popularly known as North American Digital Cellular (NADC) system. It divides each 30 KHz radio channel into three time slots, each of 10 KHz.
7. How many users are supported in IS-95 for each 1.25 MHz?
b) Sixty four
d) Twenty five
Explanation: IS-95 supports upto 64 users which are orthogonally coded and simultaneously transmitted on each 1.25 MHz. The services of IS-95 standard are short messaging service, slotted paging, over-the-air activation, enhanced mobile station identities etc.
8. Which modulation technique is used by GSM?
Explanation: GSM uses a form of modulation known as GMSK (Gaussian Minimum Shift Keying). It is a form of modulation with no phase discontinuities and provides data transmission with efficient spectrum usage.
9: IS-95 uses which modulation technique?
Explanation: IS- 95 uses BPSK (Binary Phase Shift Keying) with quadrature spreading. It is regarded as one of the most robust digital modulation technique and is used for long distance wireless communication.
10. IS-136 uses which modulation technique?
a) π/4 DQPSK
Explanation: IS-136 uses π/4 DQPSK modulation technique. This technique allows a bit rate of 48.6 Kbit/s with 30 KHz channel spacing which gives a bandwidth efficiency of 1.62 bit/s/Hz.
11. Which is one of the disadvantages of 2G standards?
a) Short Messaging Service (SMS)
b) Digital modulation
c) Limited capacity
d) Limited Internet Browsing
Explanation: 2G technologies use circuit switched data modems that limits data users to a single circuit switched voice channel. The advantages of 2G network are that they are digital in nature and supports SMS service.
12. GSM (Global System for Mobile) was earlier also known as _______
a) Group System Mobile
b) Global Special Meaning
c) Group Special Mobile
d) Global Special Mobile
Explanation: GSM was earlier known as Group Special Mobile. As it became more global, the meaning of acronym was changed to Global System for Mobile.
13. 2G CDMA standard, IS-95, was proposed by which company?
a) Nippon Telephone and Telegraph (NTT)
c) Bellcore and Motorola
d) AT&T Bell Laboratories
Explanation: IS-95 was proposed by Qualcomm in early 1990s. Later it was adopted as a standard by Telecommunications Industry Association in TIA/EIA/IS-95 release published in 1995.
14. Which one of the following 2G standard is used in Japan?
Explanation: PDC (Personal Digital Cellular) was standardized by Japanese Ministry of Posts and Telecommunication in 1991. It is similar to IS- 136, but with 25 KHz voice channels to be compatible with the Japanese analog channels.
15. The 2G GSM technology uses a carrier separation of _______
a) 1.25 MHz
b) 200 KHz
c) 30 KHz
d) 300 KHz
Explanation: The Global System for Mobile (GSM) uses a carrier separation of 200 KHz, each channel supporting upto eight users.
Sanfoundry Global Education & Learning Series – Wireless & Mobile Communications.
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