Midterm 1 Flashcards
How many layers does IEEE802.11 cover?
IEEE802.11 covers two layers: mac and physical.
Do voice applications need a complete absense of bit error rate?
No
What applications dominated the 1980s?
Voice Applications
What type of frequency requires a smaller number of cell stations for a given coverage area?
Lower Frequencies (C=lambda*f). Lower frequency, larger coverage.
What uses common frequency band for uplink and downlink?
TDD
What uses separated frequency bans for uplink and downlink?
FDD
What is the maximum latency required for voice applications?
Less than 150ns. Otherwise, echo occurs.
What application requires a complete absence of bit error rate?
Data applications. Voice applications would simply cut out.
What is the critical measure of performance for data communication?
Bit error rate. Cannot afford packet errors resulting in a change in data sent.
What is the dominate application of the future?
Machine Type Communication (MTC). IoT and the proliferation of sensor and actuator devices will be the dominant environment.
List important multi access techniques
CMA
List important modulation techniques
QAM
What impact does low frequency have on propagation loss?
Lower propagation loss. Em waves have fewer losses based on conductivity and complex dielectric constants.
Do control plane signaling and user traffic require the same bandwidth?
No. Control plane signaling requires smaller frequencies and packets compared to user traffic.
Does peer-to-peer communication occur on the same layer in different nodes?
Yes. The package goes up and down the stack but communications interface is peer to peer.
What is the unit of spectrum efficiency?
Mbps/Mhz. Determines the the data bandwidth for a given frequency spectrum and is determined primarily by modulation rate.
Where is ARQ used?
In the RLC layer.
Where is HARQ used?
In the MAC layer.
What is the primary impact of reducing Transmission Time Interval (TTI)?
As TTI is in the time domain, it should improve time or latency
Describe the beams in MIMO.
Narrow beams with a large number of antennas
Is WiFi supported in 5G?
Yes. 5G core supports multiple RAN access technologies - 5G, 4G Cellular, and WiFi.
In 5G, is there a seperation between control signaling and user plane traffic?
Yes, different base stations can provide control and user traffic interfaces.
When is carrier aggregation supported in 5G networks?
Non-contiguous frequency bands.
What codes are used for control traffic vs. user traffic?
Polar codes for traffic control and LDPC for user traffic. LDCP codes provide higher throughput and hence are used for user traffic.
Does RAN have a role in the transmission between UE and Core?
RAN provides the underlaying physical connectivity both in air interface and connectivity to the core.
What frequency does 4G LTE work in?
Only 6GHz.
When are macrocells, microcells, and picocells used?
Macrocells are used in urban areas and pico cells in dense areas.
Does 5G allow a 4G user to connect directly to its gNB?
No. 4G and WiFi RANS connect with the 5G core.
Where do Network Functions (NFs) exist?
Both in the core and edge.
When can data be transferred to the UE without requiring paging?
Paging is needed in the idle state, not the connected mode.
