CCIE, CCDP (Cisco certified)
BS, Electrical Engineering and Computer Sciences, UC Berkeley, 2007
True or False
1. A channel in TDMA represented by frequency, while in CDMA it is not represented by frequency. A. true B. false
2. If the traffic intensity is < 1 Erlang, then it will result in queuing delay which will grow without bound (if the traffic intensity stays the same). A. true B. false
3. Antennas are always omnidirectional, as they transmit in all directions. A. true B. false
4. The cellular systems are architected as cells to provide frequency reuse and thus more capacity to be able to serve more users. A. true B. false
5. With TDMA each slot takes up the full bandwidth, as time is the resource that is divided, not frequency. A. true B. false
6. Broadcast requires each user to have a channel when receiving and not share it with others. A. true B. false
7. For vehicular services the bandwidth issue is not relevant, because the vehicle is moving most of the time. A. true B. false
8. Frequency allocations for commercial users and for Federal-Government sector are done by FCC and NTIA respectively. A. true B. false
9. Software-defined radios (SDRs) adapt intelligently to their RF environment and select the least used, most powerful RF signals for processing calls. A. true B. false
10. The signal to noise ratio (SNR) of a signal determines its spectral efficiency A. true B. false
11. 3G is totally packet switched, while 4G will be circuit switched with added a packet switched service. A. true B. false
12. Handoff in a cellular system has as its main purpose the ability for a cell phone to roam to other carrier’s networks. A. true B. false
13. Shannon’s capacity formula says that under certain conditions the maximum capacity of a channel is proportional to that channel’s bandwidth. A. true B. false
14. FDMA allows different users to use different physical channels, while TDMA and CDMA do not allow this. A. true B. false
15. There are four main types of signal fading: absorption, free-space loss, Rayleigh fading, and cross-channel equalization. A. true B. false
Multiple choice
1. Low battery level will cause a mobile device to:
a) Avoid competing for contention slots b) Shift to receive-only mode c) Use another cell d) Shut down altogether
2. Consider a PSTN which receives 240 calls/hr. Each call lasts an average of 5 minutes. What is the outgoing traffic intensity to the public network?
a) 5 dB b) 5 Erlangs c) 100 dBW d) 20 Erlangs
3. A single GSM service provider supports 10 digital speech channels. Assume the probability of blocking is 1.0%. From the Erlang B chart (in Lecture Notes) find the traffic intensity and determine how many 3 minute calls this represents:
a) 20 calls b) 100 calls c) 50 calls d) 240 calls
4. Assuming 1 MHz bandwith and 24 dB signal-to-noise ratio, determine the required signaling levels.
a) 4 b) 20 c) 8 d) 16
5. The multipath effect of cellular RF signals bouncing off of many objects resulting in signal arriving at a mobile antenna at different times, in or out of phase with the direct signal, is known as:
a) Fessenden fading b) Rayleigh fading c) Free-space fading d) Uplink fading
6. How much would be the attenuation of the power received, if transmission frequency is tripled or if the distance between transmitting antenna and receiving antenna is tripled?
a) 24 dB b) 20 dB c) 10 dB d) 16 dB
7. What is the free space loss in dB for a transmission at 1 GHz, at a distance of 2 km? Ignore any antenna gains.
a) 98.44 dB b) 50.44 dB c) 124.54 dB d) 54.56 dB
8. A cell phone has a 'SEND' or 'CALL' button because:
a) A regular wireline phone access is much more complicated and difficult than wireless access over the air b) An electromagnetic voice channel needs to be set up, as it is not there ahead of time c) The channels available from a cell phone to the base station are not shared by many users d) A cell phone has a permanent channel assigned to it for voice calls.
9. The grater the frequency of a radio signal, the greater the:
a) Absorption rate b) Free-space loss c) Antenna reverberation d) Co-channel interference
10. Assume that two antennas are half-wave dipoles and each has a directive gain of 3dB. If the transmitted power is 1W and the two antennas are separated by a distance of 10 km, what is the received power? Assume that the antennas are aligned so that the directive gain numbers are correct and that the frequency used is 100 MHz.
a) 4 x 10–17 W b) 20 W c) 2.27 x 10–9 W d) 16 W
11. Consider a direct sequence spread spectrum (DSSS) system attempting to transfer data. The DSSS system has a data rate of 2 Kbps (2 thousand bits/sec) which is spread to 2 Mcps (two million chips per second). How much would be the processing gain:
a) 30 dB b) 20 dB c) 100 dB d) 60 dB
12. The statistics that indicates how much revenue per customer a wireless customer obtains on a monthly (regular) basis is:
a) ARPU b) CPU c) CFS d) RAM
