MCA
ECC PT1
Meeting 22.-24.06.
Antenna
– Base station antenna down tilt
• Preconditions are defined in ECC Report 093 (2008/05) in chapter 6.4 Terrestrial
antennas assumed in the studies
– Chapter 6.4.1 describes the Down Tilt Angle = 0 degrees for MCL (Minimum Coupling Loss)
calculations for scenario 1 and 2
– Chapter 6.4.2 describes the Down Tilt Angle = 2 degrees for SEAMCAT calculations
– Base station horizontal antenna pattern
• Preconditions are defined in ECC Report 093 (2008/05) in chapter 6.4 Terrestrial
antennas assumed in the studies
– For MCL and SEAMCAT calculations a three sector cell with uniform gain in the horizontal
plane is used (equals omni-directional within opening angle of 120 degrees in horizontal
plane)
– Feeder Loss
• Defined in the ECC reports 187 as well
• Newer BTS/NodeB/eNodeB use more often “Remote Radio Heads” where the feeder loss
is ~0dB (especially at higher frequency bands)
– Body Loss
• Description of “Human body shielding effect“ is done in chapter 9.2.2 of ECC Report 093
with application on the interference scenarios
Antenna 2
•
Preconditions of antenna parameters
– ECC Report 093 (2008/05) based on ITU-R F.1336-1 (2000/05) antenna radiation pattern
– ECC Report 187 (2013/01) based on ITU-R F.1336-3 (2012/03) antenna radiation pattern
– Latest recommended antenna radiation pattern ITU-R F.1336-4 (2014/02) with refining more
real antenna pattern (especially side lobes)
► The 3dB beamwidth in the elevation plane is derived with the same formula (for ITU-R F.1336
– 1, -3 and -4) in case of involving sectoral antennas with a 3dB beamwidth less than about
120° in both the azimuth plane and the elevation plane!
► Application of three 120° sectoral antennas as in ECC report 093 is still valid but not the
absolut worst case!
► Typical antennas used in ITU BS have a 3dB beamwidth of 90° or 65° in azimuth plane => the
3dB beamwidth in elevation gets higher (main lobe is greater) and therefore the antenna gain
for the sidlobes increases too!
•
Worsening parameters NOT taken into account
•
•
•
Worst case angle calculation for MCL based on ITU-R F.1336-4 leads to higher antenna
gain at worst case angle and therefore to higher margin in the link budget calculation
Reflections on the ground plane are not takin into account anyway
Typical antennas with 3dB beamwidth of 90° or 65° in azimuth plane
Real Network Handover Statistics
Aircraft-based
Additional Topics
• User can use manual network search
– E.g. Users in border regions have manual mode
permanently switched on.
• User may disable roaming
Interference - 1
Differences between the onboard UE and UE at the ground
•Moves with very high speed
•Doppler Shift
•Network algorithms are designed for ground UE
-> Timing advance and equalization
•High above the surface -> LOS to cells in a big area
•Can receive cells in huge distances
Interference – 2
Additional load to the ground network
•Same signalling protocols as for UE at ground
•Handover
•Cell reselection / tracking area update
•Random Access Channel and MME affected
•Difference is the speed of the aircraft
•Every onboard UE will perform HO every 10s
-> or cell reselection for data users
•Frequent Tracking Area Updates for idle mode UE
Interference – 3
Additional load to the ground network
•Random Access Procedure
•Adjacent cells use different Acess
Preamble sets
•Onboard UE is received by distant
ground eNB
•Some of them would have the
same AP set
•RACH has no destination address,
only AP number
•Phantom RACH
•eNB answers all RACH in its AP set
range
•One RACH request is answered by
dozens of eNB
Interference – 4
Interference to the cell where the onboard UE is connected
•Inter Carrier Interference (ICI)
•Doppler Shift
•Frequency offset creates interference to adjacent
ressource blocks
•Inter SymbolInterference (ISI)
•Timing advance of the ground cell is designed for
ground UE
•Due to the high speed of the aircraft theTA of onboard
UE doesn‘t follow the rapid change in distance
Interference – 5
Interference to the other cells
•Interference avoidance by
•Different frequencies in adjacent cells (GSM)
•Different scrambling code in adjacent cells (UMTS)
•Far away cells
•Can have the same frequency / scrambling code
•Interference to other connections
Interference – 6
Interference canellation (IC) in uplink
•IC detects one or more strong interferers
•Known Reference Symbols (RS)
•Subtracts the detected interferer from the signal
•RS needs to be different in adjacent cells for IC
•Far away cells
•Could have the same RS
•IC can‘t detect these interferers
•Doppler shift
•Generates some noise to the RS
•IC detects wrong channel for the interferer
•IC subtracts wrong signal (could even make things
worse)
Timer HPPLMN
• Timer HPPLMN
– Re-Connect to Home Network
– Examples: O2-DE: 6min, Vodafone-DE: 30min
– Differentiated SIM/UE world
– Only configurable via HomeNetwork