LTE Interview Questions

LTE Interview Question

Question-1

Often it is asked to differentiate between single carrier and multiple carrier systems(i.e. OFDM, OFDMA)?

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Answer: SC (single carrier) system carry less information while multi carrier occupy multiple bits simultaneously. Hence data rate is higher for multicarrier compare to single carrier system.

Question-2

What is the difference between Erlang and GoS?

Answer-: Both Erlang and GoS are used in telephone exchange for measurement of calls such as calls dropped, calls passed etc.

Question-3

What is Bit Error Rate and how it is calculated?

Answer: Bit error rate (BER) is used to measure performance of the wireless or wired system in channel or impairment environment. BER is the ratio of received erroneous bits to the total number of bits transmitted.

Question-4

What is the difference between CAS and CCS?

Answer: CAS stands for Channel Associated Signaling and CCS stands for Common Channel Signaling. Both are associated with PCM used in telephony.

Question-5

Explain multipath fading. ?

Answer: The variation is received signal strength over time is referred as fading. When the signal traverse from transmit end to receive end, it will have many reflections from buildings and walls till it reaches receive end. This results into multipath fading.

Question-6

What is the relation between wavelength and frequency?

Answer: Wavelength and frequency are inversely proportional to each other.
λ = C/Frequency,
C = 3 X 10 ^8 m/sec

Question -7

What is type of modulation used in GSM?

Answer . GMSK stands for Gaussian Minimum Shift Keying.

Question 8

What is the difference between LTE FDD and LTE TDD? 

Answer:The difference lies in the LTE frame structure in both the FDD and TDD versions of the LTE.
In FDD there will be pair of frequencies assigned in the downlink and uplink directions and hence transmissions from multiple subscribes can happen at the same time but on different frequencies as mentioned.
In TDD, one single frequency will be used at different time instants by multiple subscriber terminals (UEs).
Both frame versions of LTE will have 1 ms sub-frame duration and 0.5 ms slot duration.

Question-9

What is the difference between LTE and LTE Advanced?

Answer-:
LTE is specified in 3GPP release 8 and release 9.
LTE advanced is specified in 3GPP release 10.
The main difference between them is carrier aggregation is introduced in LTE advanced.
Number of antennas supported by MIMO has been increased to 8 in LTE advanced.

Question10

What is the difference between WiMAX system and LTE system?

Answer: WiMAX and LTE both are used for providing broadband internet access services.
Voice services are also planned to provide over wimax and LTE networks using Voice over IP protocols.

WiMAX stands for World Wide Interoperability for Microwave Access and

LTE stands for Long Term Evolution.

WiMAX fall back to non-cellular technologies such as WLAN.

LTE fall back to cellular technologies such as GSM, UMTS etc.

In wimax both uplink and downlink use symmetric modulation schemes such as OFDM or OFDMA.

In LTE downlink uses OFDMA and uplink uses SC-FDMA....