Midterm 1

Question 1

How many layers does IEEE802.11 cover?

Answer 1

IEEE802.11 covers two layers: mac and physical.

Question 2

Do voice applications need a complete absense of bit error rate?

Answer 2

No

Question 3

What applications dominated the 1980s?

Answer 3

Voice Applications

Question 4

What type of frequency requires a smaller number of cell stations for a given coverage area?

Answer 4

Lower Frequencies (C=lambda*f). Lower frequency, larger coverage.

Question 5

What uses common frequency band for uplink and downlink?

Answer 5

TDD

Question 6

What uses separated frequency bans for uplink and downlink?

Answer 6

FDD

Question 7

What is the maximum latency required for voice applications?

Answer 7

Less than 150ns. Otherwise, echo occurs.

Question 8

What application requires a complete absence of bit error rate?

Answer 8

Data applications. Voice applications would simply cut out.

Question 9

What is the critical measure of performance for data communication?

Answer 9

Bit error rate. Cannot afford packet errors resulting in a change in data sent.

Question 10

What is the dominate application of the future?

Answer 10

Machine Type Communication (MTC). IoT and the proliferation of sensor and actuator devices will be the dominant environment.

Question 11

List important multi access techniques

Answer 11

CMA

Question 12

List important modulation techniques

Answer 12

QAM

Question 13

What impact does low frequency have on propagation loss?

Answer 13

Lower propagation loss. Em waves have fewer losses based on conductivity and complex dielectric constants.

Question 14

Do control plane signaling and user traffic require the same bandwidth?

Answer 14

No. Control plane signaling requires smaller frequencies and packets compared to user traffic.

Question 15

Does peer-to-peer communication occur on the same layer in different nodes?

Answer 15

Yes. The package goes up and down the stack but communications interface is peer to peer.

Question 16

What is the unit of spectrum efficiency?

Answer 16

Mbps/Mhz. Determines the the data bandwidth for a given frequency spectrum and is determined primarily by modulation rate.

Question 17

Where is ARQ used?

Answer 17

In the RLC layer.

Question 18

Where is HARQ used?

Answer 18

In the MAC layer.

Question 19

What is the primary impact of reducing Transmission Time Interval (TTI)?

Answer 19

As TTI is in the time domain, it should improve time or latency

Question 20

Describe the beams in MIMO.

Answer 20

Narrow beams with a large number of antennas

Question 21

Is WiFi supported in 5G?

Answer 21

Yes. 5G core supports multiple RAN access technologies - 5G, 4G Cellular, and WiFi.

Question 22

In 5G, is there a seperation between control signaling and user plane traffic?

Answer 22

Yes, different base stations can provide control and user traffic interfaces.

Question 23

When is carrier aggregation supported in 5G networks?

Answer 23

Non-contiguous frequency bands.

Question 24

What codes are used for control traffic vs. user traffic?

Answer 24

Polar codes for traffic control and LDPC for user traffic. LDCP codes provide higher throughput and hence are used for user traffic.

Question 25

Does RAN have a role in the transmission between UE and Core?

Answer 25

RAN provides the underlaying physical connectivity both in air interface and connectivity to the core.

Question 26

What frequency does 4G LTE work in?

Answer 26

Only 6GHz.

Question 27

When are macrocells, microcells, and picocells used?

Answer 27

Macrocells are used in urban areas and pico cells in dense areas.

Question 28

Does 5G allow a 4G user to connect directly to its gNB?

Answer 28

No. 4G and WiFi RANS connect with the 5G core.

Question 29

Where do Network Functions (NFs) exist?

Answer 29

Both in the core and edge.

Question 30

When can data be transferred to the UE without requiring paging?

Answer 30

Paging is needed in the idle state, not the connected mode.