UMTS: Alive and Well - 4G Americas

Whether the performance improvements by this type of receiver can be assumed is implementationspecific.INTERFERENCE COORDINATION / AVOIDANCEThis section discusses the concept of interference coordination and avoidance.In contrast to previous WCDMA modulation, OFDM and SC-FDMA are both frequency divisionmultiplexing access methods. (The complex exponentials used for the modulation are the eigenfunctionsof the quasi LTI channel).Thus, almost independent of the channel transmission, interference created on certain frequencies suchas in a Physical Resource Block (PRB) only affects those frequencies such as the same PRB in aneighbor cell. Interference in these schemes is predictable and avoidable. This property can be used forspecific interference avoidance methods in UL and in DL.INTER-CELL INTERFERENCE COORDINATION (ICIC) SCHEMESICIC schemes basically involve the intelligent coordination of resources between various neighboringcells to reduce interference from one cell to another. Each cell gives up use of some resource in acoordinated fashion to improve performance especially for cell edge users which are impacted the mostby inter-cell interference. The cells typically coordinate the transmission powers across various frequencyresource blocks. Coordination of spatial beams can also be done. This coordination and configuration ofwhich resources to use and how, can be done in either a static or dynamic fashion.DOWNLINK STATIC INTER-CELL INTERFERENCE COORDINATION SCHEMESIn Downlink, the common theme of inter-cell-interference coordination is to apply restrictions to thedownlink resource management in a coordinated way between cells. These restrictions can be in the formof restrictions as to what time/frequency resources are available to the resource manager or restrictionson the transmit power that can be applied to certain time/frequency resources. Such restrictions in a cellwill provide improved SIR and cell-edge data-rates/coverage on the corresponding time/frequencyresources in a neighbor cell.In static schemes, these restrictions are distributed to the different cells and are constant on a time scalecorresponding to days. Different types of restriction distributions can be used which involve frequency orcell planning in an area (e.g. an inverted reuse 7 scheme [FFR=6/7] as shown in Figure C.44).www.3GAmericas.org February 2010 Page 193