RF Interview Ques Answer 11-20

Q11. What is CINR?

Ans. CINR is Carrier to interference plus noise ratio, Basically it is the parameter used for check interference in signal. It is a measurement of signal effect which is expressed in Decibels. In order for a receiver to correctly process a received signal, the CINR of that signal must be at the correct CINR level.CINR range is 0 to 30 decibel. Means 30 is good, and 0 is bad.

Q12. What is Rank Indicator in MIMO?

Ans. In MIMO transmission we have CSI (Channel Status Indicator). CSI have 3 main indicators: 1. CQI (Chennel Quality Indicator), 2. PMI (Pre-coding Metrix Indicator), 3. RI (Rank Indicator).

RI have two values RI 1 means ue face bad radio condition, RI 2 means ue have good radio condition, behalf of RI1 & RI2 enodeB decide which transmission mode should apply to transmitt a signal in ue direction.

Q13. How many Types of Towers have in Radio Networks?

Ans. Tower types:

GBT-Ground based tower

GBM-Ground based monopole

MBTS-Mobility base transceiver system

RTT-Roof top tower

RTP-Roof top pole.

COW. Cells on wheel.

IBS-In-building solution

Femto cell

Home EnodeB

Q14. What is PCI? How to calculate PCI in LTE? Total PCI present in LTE?

Ans. PCI is the physical cell ID of a sectors on site or we can say pci is the name of a sector on a tower. LTE networks provide a unique value for identifying eNbs. The PCI value is generated from two signals – PSS and SSS. The PSS, Primary Synchronization Signal, has the value 0, 1, and 2. The SSS, Secondary Synchronization Signal, can have a value between [0--167]. The PCI value is [(3x SSS)+(PSS)], resulting in a value between 0 and 503. Total 504 PCI values.

Q15. What is PCI Collision?

Ans. PCI collision means when same number of PCI is broadcasting by two different antenna than it creates interference. This is called as PCI collision.

Q16. What do mean by RSRP, RSRQ and RSSI in LTE? And what kind of information they carry?

Ans. RSRP- Reference signal received power Its a most basic parameter in LTE used to show the power of a received signal, Range is =(-44 to -144)dBM . The formula of RSRP = (RSSI-10 log(12N)).

RSRQ-Refrence signal received quality its used to show the quality of signal, range is (-3 to 19.5)dBM. The formula is RSRQ=[RSRP/(RSSI/N)]

RSSI-Refrence signal strength indicator its used to show the strength of the received signal and for better strength used to less than -110. The formula is RSSI-RSRP*12N.

Q17. What is SWAP? And how many type of SWAP’s are in LTE?

Ans. Interchanging of feeder cable is called swap. There are three types of swap;

1. Sector swap; when feeder A cables connected in B, and B cable in A.
2. Cyclic Swap- when feeder A cable connected in B, B cable connected in C, C cable connected in A
3. Diversity Swap- When (-negative) feeder cable connected in (+positive) port and vice-versa then diversity port and diversity cable give diversity swap.

Q18. How many types of Antenna’s are using in network?

Ans. There are two types of antenna used in network (i) micro and (ii)Macro, micro used usually in indoor and macro used for outdoor serving. (iii) femto cells are using in highly dense area & offices.

Q19. What is Front lobe and Back lobe Coverage of Antenna’s?

Ans. Antenna main lobe having a more power than back lobe. The Front and Back lobe ratio=[forward power /backward power].

Q20. What is Antenna Gain? How it affect on Coverage?

Ans. Antenna gain tells us the power transmitted by an antenna in a specific direction as compared to an isotropic antenna. Antenna Gain is a more important specification than directivity, as it takes in account all the losses. Antenna gain indicates how strong a signal an antenna can send or receive in a specified direction. Gain is calculated by comparing the measured power transmitted or received by the antenna in a specific direction to the power transmitted or received by a hypothetical ideal antenna in the same situation

Antenna gain = Directivity x Efficiency.