This set of Wireless & Mobile Communications Multiple Choice Questions & Answers (MCQs) focuses on “United States Digital Cellular (IS-54 and IS-136)”.
1. The dual mode USDC/AMPS system was standardized as ____________
a) IS-54
b) IS-136
c) PSTN
d) GSM
View Answer
Explanation: The dual mode USDC/AMPS system was standardized as Interim Standard 54 (IS 54). It was standardized by Electron Industries Association and Telecommunication Industry Association (EIA/TIA) in 1990. It was later upgraded to IS-136.
2. USDC is also known as ___________
a) SADC
b) NADC
c) PADC
d) N-AMPS
View Answer
Explanation: USDC is also known as North American Digital Cellular (NADC). It has been installed in North America in the countries like Canada and Mexico.
3. USDC was designed to share different frequencies as compared to AMPS.
a) True
b) False
View Answer
Explanation: The USDC system was designed to share the same frequencies, frequency reuse plan, and base stations as AMPS, so that base stations and subscriber units could be equipped with both AMPS and USDC channels within the same piece of equipment.
4. Because of the compatibility with AMPS, USDC is also known as ___________
a) SADC
b) PADC
c) D-AMPS
d) K-AMPS
View Answer
Explanation: USDC (United States Digital Cellular System) maintains compatibility with AMPS in a number of ways. Therefore, USDC is also known as D-AMPS (digital AMPS).
5. USDC forward and reverse control channels use exactly the same signalling techniques as AMPS.
a) True
b) False
View Answer
Explanation: To maintain compatibility with AMPS phones, USDC forward and reverse control channels use exactly the same signalling techniques as AMPS. USDC voice channels use 4-ary π/4 DQPSK modulation with a channel rate of 48.6 kbps.
6. USDC has ___________ as many control channels as AMPS.
a) Same
b) Three times
c) Twice
d) Four times
View Answer
Explanation: USDC has twice as many control channels as AMPS. In addition to the forty two primary AMPS control channels, USDC specifies forty two additional control channels called the secondary control channels.
7. Which of the following data channels of USDC carries the user information?
a) DTC
b) CVDCC
c) SACCH
d) FACCH
View Answer
Explanation: DTC (data traffic channel) is the most important data channel as far as the end user is concerned. It carries user information (i.e. speech or user data).
8. Which of the following channel is similar in functionality to the SAT used in AMPS?
a) DTC
b) CDVCC
c) SACCH
d) FACCH
View Answer
Explanation: CDVCC (Code Digital Verification Color Code) is a 12 bit message sent in every time slot and is similar in functionality to the SAT used in AMPS. The CDVCC is an 8 bit number ranging between 1 and 255, which is protected with four additional channel coding bits from a shortened Hamming code.
9. Which of the following channel in USDC provides a signalling channel?
a) DTC
b) CVDCC
c) SACCH
d) FACCH
View Answer
Explanation: The SACCH (slow associated control channel) is sent in every time slot and provides a signalling channel in parallel with the digital speech. The SACCH carries various control and supervisory messages between the subscriber unit and the base station.
10. Which of the following channel in USDC is used to send important control or specialized traffic data between the base station and mobile units?
a) DTC
b) CVDCC
c) SACCH
d) FACCH
View Answer
Explanation: FACCH (fast associated control channel) is used to send important control or specialized traffic data between the base station and mobile units. The FACCH data, when transmitted, takes the place of user information data within a frame.
11. Which of the following speech coder is used in USDC?
a) Vector Sum Excited Linear Predictive coder
b) Formant Vocoder
c) Multipulse Excited Linear Predictive coder
d) Residual Excited Linear Predictive coder
View Answer
Explanation: The USDC speech coder is called the Vector Sum Excited Linear Predictive coder (VSELP). This belongs to the class of Code Excited Linear Predictive coders (CELP) or Stochastically Excited Linear Predictive coders.
Sanfoundry Global Education & Learning Series – Wireless & Mobile Communications.
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