TRUE/FALSE
1. There are three competing, and incompatible, PCS systems in North America.
ANS: T
2. The current PCS systems are "true" personal communications systems in their performance.
ANS: F
3. Europe has basically one PCS system based on GSM technology.
ANS: T
4. GSM is used in North America.
ANS: T
5. Current PCS systems are referred to as "third-generation", with AMPS and digital cell phones being the first and second generations.
ANS: F
6. One reason for developing PCS was that the 800-MHz band was too crowded.
ANS: T
7. The North American PCS band is 1.9 GHz.
ANS: T
8. PCS cells are typically smaller than AMPS cells.
ANS: T
9. All first generation cellular systems are analog.
ANS: T
10. Current digital technology is not as efficient as analog FM in its use of bandwidth.
ANS: F
11. Today, roaming is easier with PCS than it is with AMPS.
ANS: F
12. IS-136 PCS is usually just called TDMA PCS.
ANS: T
13. In TDMA PCS, control frames are mixed in with frames carrying voice.
ANS: T
14. GSM is a TDMA system.
ANS: T
15. GSM is not as sophisticated as IS-136.
ANS: F
16. In GSM PCS, control frames are mixed in with frames carrying voice.
ANS: T
17. GSM uses extensive frequency hopping for spread-spectrum.
ANS: F
18. Frequency hopping lessens the impact of multipath fading.
ANS: T
19. The SIM used in a GSM phone helps prevent unauthorized use.
ANS: T
20. GSM security is not as good as it is in IS-136.
ANS: F
21. IS-95 PCS uses CDMA technology.
ANS: T
22. IS-95 allows a "soft" handoff.
ANS: T
23. A "soft" handoff is done without interrupting service.
ANS: T
24. IS-95 can achieve space diversity by using antennas in separate cell-sites.
ANS: T
25. One drawback of IS-95 is its lack of frequency diversity.
ANS: F
26. Security with CDMA is not as good as it is in GSM.
ANS: F
27. Unlike AMPS, CDMA PCS does not require the cell phone to adjust its ERP.
ANS: F
28. Potentially, CDMA makes the best use of available bandwidth.
ANS: T
29. In CDMA it is common for the signal power in the receiver to be less than the noise power.
ANS: T
30. The Walsh code is used for error detection in CDMA systems.
ANS: F
MULTIPLE CHOICE
1. Current PCS systems are referred to as:
| a. | first-generation | c. | third-generation |
| b. | second-generation | d. | digital-generation |
ANS: B
2. The frequency band designated for PCS in North America is:
| a. | 800 MHz | c. | 1.9 GHz |
| b. | 900 MHz | d. | 12 GHz |
ANS: C
3. The "forward" PCS channel is:
| a. | from the base to the mobile | c. | from mobile to mobile |
| b. | from the mobile to the base | d. | same as the uplink |
ANS: A
4. Compared to AMPS, PCS cell sites are:
| a. | bigger | c. | distributed |
| b. | smaller | d. | higher-power |
ANS: B
5. AMPS was designed for:
| a. | POTS | c. | use built into an automobile |
| b. | voice | d. | all of the above |
ANS: D
6. The number of competing PCS systems in North America is:
| a. | 2 | c. | 4 |
| b. | 3 | d. | many |
ANS: B
7. CDMA technology was invented by:
| a. | AT&T | c. | Bell Labs |
| b. | Lucent | d. | Qualcomm |
ANS: D
8. GSM is used in:
| a. | Asia | c. | North America |
| b. | Europe | d. | all of the above |
ANS: D
9. In GSM, voice channels are called:
| a. | traffic channels | c. | bearer channels |
| b. | voice channels | d. | talking channels |
ANS: A
10. AMPS uses:
| a. | CDMA | c. | spread-spectrum |
| b. | TDMA | d. | none of the above |
ANS: D
11. Other things being equal, battery life in a GSM phone should be:
| a. | less than in a TDMA phone | c. | greater than in a TDMA phone |
| b. | no better than in an AMPS phone | d. | no better than a TDMA phone |
ANS: C
12. It is necessary to send control information on traffic channels in:
| a. | no PCS system | c. | TDMA only |
| b. | GSM only | d. | both GSM and TDMA |
ANS: D
13. GSM uses:
| a. | frequency hopping | c. | CDMA |
| b. | direct-sequence modulation | d. | all of the above |
ANS: A
14. In GSM, SIM stands for:
| a. | Short Inbound Message | c. | Subscriber ID Module |
| b. | Subscriber-Initiated Message | d. | Subscriber ID Method |
ANS: C
15. IMSI stands for:
| a. | Integrated Mobile Subscriber Identification |
| b. | International Mobile Subscriber Identification |
| c. | Interim Mobile Subscriber Identification |
| d. | Intermodulation System Interference |
ANS: B
16. IS-95 uses:
| a. | frequency hopping | c. | CDMA |
| b. | TDMA | d. | all of the above |
ANS: C
17. IS-136 uses:
| a. | frequency hopping | c. | CDMA |
| b. | TDMA | d. | all of the above |
ANS: B
18. In CDMA:
| a. | all frequencies are used in all cells |
| b. | each cell uses half the available frequencies |
| c. | each cell is assigned a frequency by the base |
| d. | the frequency is selected by the mobile phone |
ANS: A
19. CDMA uses a set of PN sequences that are:
| a. | common | c. | rotating |
| b. | unique | d. | orthogonal |
ANS: D
20. The next generation of PCS is expected to have:
| a. | faster data rates | c. | wider roaming area |
| b. | Internet access | d. | all of the above |
ANS: D
COMPLETION
1. PCS stands for ____________________ Communications System.
ANS: Personal
2. Current PCS systems are called ____________________-generation systems.
ANS: second
3. In North America, PCS is assigned the ____________________-MHz band.
ANS: 1900
4. Compared to AMPS, PCS cells are ____________________ in size.
ANS: smaller
5. Besides TDMA and CDMA, ____________________ is also used in North America for PCS.
ANS: GSM
6. The spread-spectrum technique used in IS-95 PCS is ____________________.
ANS:
CDMA
direct sequence
7. The spread-spectrum technique used in GSM is _________________________.
ANS: frequency hopping
8. Unlike AMPS, CDMA allows for a ____________________ handoff.
ANS: soft
9. The orthogonal PN sequences used in CDMA are called a ____________________ code.
ANS: Walsh
10. Unlike other systems, in CDMA ____________________ frequencies are used in all cells.
ANS: all
11. PN stands for Pseudo-____________________ Noise.
ANS: random
12. ____________________ diversity is inherent in any spread-spectrum system.
ANS: Frequency
13. RF channel S/N ratios ____________________ than zero are typical in CDMA systems.
ANS: less
14. CDMA uses a ____________________-rate vocoder.
ANS: variable
15. A phone user typically talks less than ____________________% of the time during a conversation.
ANS: 50
16. CDMA requires ____________________-loop power control to work properly.
ANS: closed
17. GPRS stands for General ____________________ Radio Service.
ANS: Packet
18. IMT stands for International ____________________ Telecommunications.
ANS: Mobile
19. UPT stands for ____________________ Personal Telecommunications.
ANS: Universal
20. UWT stands for Universal ____________________ Telecommunications.
ANS: Wireless
21. W-CDMA stands for ____________________ CDMA.
ANS: Wideband
SHORT ANSWER
1. What is the advantage of a "soft" handoff?
ANS:
No calls are dropped.
2. If CDMA receivers hear all frequencies all the time, how do they pick a specific frequency?
ANS:
Each frequency is modulated using a separate orthogonal PN sequence. To demodulate, the receiver uses the PN sequence specific to the channel it wants.
3. What is the effect of cochannel interference in CDMA?
ANS:
It increases the background noise level, but CDMA can tolerate a lot of such noise.
4. How does GSM achieve frequency diversity?
ANS:
It uses limited frequency hopping.
5. Why was PCS assigned to 1.9 GHz instead of the 800-MHz band used for AMPS?
ANS:
The 800 MHz band was already overcrowded.
6. Why would a battery in a GSM phone be expected to last longer than a battery in a TDMA phone?
ANS:
A TDMA phone is active during one out of every three time slots. A GSM phone is active during one out of every eight.
7. What is the advantage of using offset QPSK over standard QPSK?
ANS:
With standard QPSK, the transmitted power repeatedly goes to zero. With offset QPSK, it never goes to zero. Linearity requirements are less strict for offset QPSK transmitters.
8. What is the "near/far" effect in CDMA, and what causes it?
ANS:
A stronger station farther away can "drown out" a weaker station that is near. This happens when the power transmitted by mobile units is not well controlled by the base.
0 comments:
Post a Comment