1. What is the meaning of RX quality? What is Meaning of RX qual 0 to 7? → Rx Quality means received signal quality. RXQUAL is a logarithmic measure of the bit error probability, quantized in 8 levels (3GPP specification).
RxQual Bit Error Rate (BER) 0 1 2 3 4 5 6 7
BER < 0.2% 0.2% < BER < 0.4% 0.4% < BER < 0.8% 0.8% < BER < 1.6% 1.6% < BER < 3.2% 3.2% < BER < 6.4% 6.4% < BER < 12.8% 12.8% < BER
2. Why RX lavel is negative? Why it measured in dBm? → Rx level becomes negative because signal propagation loss or path loss is higher than the transmit power of BTS. Normally, Received signal power = Transmit power + Antenna Gain – Path loss As Path loss > (Transmit power + Antenna Gain) Rx‐level becomes negative. → dBm is used in radio signal strength measurement because it convenient to express the very small value of power in short forms. 3. What is the acceptable range of RX quality & RX label? Why? It depends on clutter type and service you want to provide. MS sensitivity around ‐102 dbm. So Rx‐ level should be higher than that. In cities it can be ‐80dbm. Rx‐qual above 5 (means 6 and 7) is not acceptable. 4. Why two feeder cables are used in GSM antenna? What is RX DIVERSITY? → I did not understand the first question. For 2 ports GSM‐Antenna, you need two feeders, if you want to use the two antennas inside the antenna housing. → Diversity means using two or multiple channel with different characteristics to improve the reliability of signals. We you use this method to maintain received signal’s reliability; it is called Rx‐ Diversity. In GSM network, we often use two antennas for receiving the signal and thus use RX‐ Diversity. 5. How you identify cable mismatch by drive test?
By analyzing DT log, you can see coverage area of different cells. So, if you know the serving cell’s antenna direction is to one direction, but you get the coverage in other direction, then you can find it. 6. Why different types of antennas are used at different sites? For example we use 739491,742215 etc 7.for 1800 & 739686,739685,739684 etc for 900 → Different antennas have different specifications (gain, band, H/V beamwidth, length, wight etc). For different scenario (traffic distribution, clutter, service etc) you need to use different antennas. 8. What is the relation between M. & E. tilting? Why we use 0,up or down M. tilting at sites? No relation. E tilt mean electrical tilt (internally change the radiation pattern) and M.tilt means mechanical tilt (physically tilting antenna). Both are used to tilt the antenna radiation pattern. By increasing and decreasing M.tilt, you can manage the coverage area of serving cells. 9. Why we increase or decrease E. tilting? → By increasing and decreasing E.tilt, you can manage the coverage area of serving cells. 10. During PAT what physical parameters are important for checking (For radio quality)? What is the effect of wrong orientation, height, tilting etc? From RP point of view, you can check GSM plan (antennas, height, azimuth, cable connections, vswr etc) If the GSM plan is not correctly implemented then performance of service may be degraded or you don’t get service in your designed area. 11. Is 1.5 VSWR means 50% signal is reflect back that means only 50% signal is used? Please explain No. VSWR 1.5 means only 4% signal will reflect back. Please see the VSWR equations. You can find it. 12. Which one is much sensitive, MS or BTS? Why? BTS is more sensitive. Because mobile phone uses less power (max 2W) to transmit signal. This signal fades away due to path loss and BTS have to be more sensitive to receive the low signal. 13. What is the meaning of polarization at GSM plan (Cross polarization found at GSM plan?) Polarization is one type of Antenna diversity. This is an antenna specification, what you see in GSM plan. Cross polarization mean pair of antennas are arranged with an angle of +45⁰ and ‐45⁰ inside antenna housing.
