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As per 36.104 [6] , 4.2 Base station classes,
"... this specification apply to Wide Area Base Stations, Medium Range Base Stations, Local Area Base Stations and Home Base Stations
unless otherwise stated.
Wide Area Base Stations are characterised by requirements derived from Macro Cell scenarios
with a BS to UE minimum coupling loss equal to 70 dB.
The Wide Area Base Station class has the same requirements as the base station for General Purpose application in Release 8.
Medium Range Base Stations are characterised by requirements derived from Micro Cell scenarios
with a BS to UE minimum coupling loss equal to 53 dB.
Local Area Base Stations are characterised by requirements derived from Pico Cell scenarios
with a BS to UE minimum coupling loss equal to 45 dB.
Home Base Stations are characterised by requirements derived from Femto Cell scenarios. ..."
Based on above distinction, we may say, Macro cells are usually outdoor cells covering larger areas.
Micro and Pico cells would cover mostly combinations of indoor/outdoor/open/closed environments,
say stadiums, malls, business complexes, railway stations, and so on.
Femto cells are mostly indoor cells say offices, residential buildings, aircrafts, and so on.
Release 8 introduced LTE.
UMTS already had Home NB concept, same was applied to LTE, known as "Home eNB".
Home eNB was based on Closed Subscriber Group (EPC based functionality), meant for in door enviornments (office).
HeNB connects to EPC over fixed broadband.
Releases 8 [1] and 9 [2] also specified a RRM feature, ICIC (Inter-Cell Interference Coordination) to handle
interference between intra-frequency cells.
RRM sit between RRC and X2.
Under this feature, X2AP [8] message LOAD INFORMATION was used to exchange interference information between eNBs.
This message indicate PRBs where high UL interference is seen or where UL interference overload is seen.
Target eNB scheduler may then need to adjust till it is updated again (as OK) by Source eNB.
Refer X2AP CRs R3-080941 and
R3-080867 for more details.
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