t power is the use of basic principles discussed above apply also to a sce- additional antennas at the receiver side, also known as nario where interference is the main radio-link receive-antenna diversity. Multiple receive antennas impairment: can be applied at the base station (that is for the The maximum data rate that can be achieved in uplink) or at the mobile terminal (that is for the a given bandwidth is limited by the available signal- downlink). By proper combining of the signals received at the different antennas, the signal-to-noise ratio after power-to-interference-power ratio. the antenna combining can be increased in proportion Providing data rates larger than the available band- to the number of receive antennas, thereby allowing for width (high-bandwidth utilization) is costly in the higher data rates for a given transmitter/receiver sense that it requires an un-proportionally high distance. signal-to-interference ratio. Multiple antennas can also be applied at the trans- Also similar to a scenario where noise is the dominating mitter side, typically at the base station, and be used to radio-link impairment, reducing the cell size as well focus a given total transmit power in the direction of the as the use of multi-antenna techniques are key means receiver, i.e. toward the target mobile terminal. This will to increase the achievable data rates also in an increase the received signal power and thus, once again, interference-limited scenario: allow for higher data rates for a given transmitter/ Reducing the cell size will obviously reduce the receiver distance. number of users, and thus also the overall traffic, However, providing higher data rates by the use of per cell. This will reduce the relative interference multiple transmit or receive antennas is only efficient up level and thus allow for higher data rates. to a certain level, i.e. as long as the data rates are power Similar to the increase in signal-to-noise ratio, proper limited rather than bandwidth limited. Beyond this combining of the 