adewijaya
2011-07-26, 01:05 PM
Cause Analysis of Signal Fluctuation
1. Cause of Signal Fluctuation when a MS is in Idle State
1) Propagation
I. Radio wave transmits in three forms: perpendicular incidence, diffraction, and scattering (reflection).
II. The received signal strength refers to the amplitude of the sector sum of all propagation paths.
III. The received signal strength is a random variable.
IV. Because the propagation environment is time-variant, the fading of the radio channel is time-variant. Therefore, the received signal strength is time-variant regardless of the state of a MS.
Conclusion:
I. Find the real cause of signal fluctuation. In most cases, signal fluctuation is caused by propagation.
II. When the median incoming level of a MS is strong, the signal indication on the MS does not change if the signal fluctuation is caused by propagation. But the change in signal strength displays on a dedicated test MS. In the circumstances, explain the cause to users in an appropriate way.
III. When the median incoming level of a MS is weak, the change in signal indication can be seen on the MS. If the signal is so weak as to influence the call, the coverage must be improved.
2) Antenna Selection
I. The antenna directional diagram comprises a main lobe section and a secondary lobe section.
II. The secondary lobe section has many interlaced zero points and peak points.
III. The vertical lobe of an omnidirectional high gain antenna is narrow (often less than 7 degrees).
IV. When an antenna shakes, the antenna gain changes looked at from the angle of the fixed point in the secondary lobe section. In extreme circumstances, zero points and peak points irradiate on the test point alternately, which causes signal fluctuation.
Solutions:
I. Replace with an omni antenna that has a tilt angle and null filling functions or use a wide-beam low gain antenna.
II. Change an omni BTS to a directional one.
1. Cause of Signal Fluctuation when a MS is in Idle State
1) Propagation
I. Radio wave transmits in three forms: perpendicular incidence, diffraction, and scattering (reflection).
II. The received signal strength refers to the amplitude of the sector sum of all propagation paths.
III. The received signal strength is a random variable.
IV. Because the propagation environment is time-variant, the fading of the radio channel is time-variant. Therefore, the received signal strength is time-variant regardless of the state of a MS.
Conclusion:
I. Find the real cause of signal fluctuation. In most cases, signal fluctuation is caused by propagation.
II. When the median incoming level of a MS is strong, the signal indication on the MS does not change if the signal fluctuation is caused by propagation. But the change in signal strength displays on a dedicated test MS. In the circumstances, explain the cause to users in an appropriate way.
III. When the median incoming level of a MS is weak, the change in signal indication can be seen on the MS. If the signal is so weak as to influence the call, the coverage must be improved.
2) Antenna Selection
I. The antenna directional diagram comprises a main lobe section and a secondary lobe section.
II. The secondary lobe section has many interlaced zero points and peak points.
III. The vertical lobe of an omnidirectional high gain antenna is narrow (often less than 7 degrees).
IV. When an antenna shakes, the antenna gain changes looked at from the angle of the fixed point in the secondary lobe section. In extreme circumstances, zero points and peak points irradiate on the test point alternately, which causes signal fluctuation.
Solutions:
I. Replace with an omni antenna that has a tilt angle and null filling functions or use a wide-beam low gain antenna.
II. Change an omni BTS to a directional one.