Virtual Antenna Mapping (VAM) is used in wireless telecom

network Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

s. Typically when

MIMO In radio, multiple-input and multiple-output (MIMO) () is a method for multiplying the capacity of a radio link using multiple transmission and receiving antennas to exploit multipath propagation. MIMO has become an essential element of wirel ...

is deployed using two

power Amplifier An audio power amplifier (or power amp) amplifies low-power electronic audio signals, such as the signal from a radio receiver or an electric guitar pickup, to a level that is high enough for driving loudspeakers or headphones. Audio power a ...

for two transmit antennae, there is a risk that both power amplifiers are not optimally used. Non-MIMO traffic would be using up to half of the available power whereas MIMO traffic could use the full power. This could potentially have an adverse impact on the overall cell throughput. VAM is used to achieve the goal of power balancing the physical channels across the multiple physical antennas especially when MIMO is deployed in the downlink. VAM gives an illusion to the UE that there are actually fewer antennas at the base station than it actually has. The unbalanced balanced power across two transmits paths are transformed into balanced power at physical antenna ports by VAM. This is achieved using phase and amplitude coefficients (V₁₁, V₁₂, V₂₁, V₂₂) as depicted in the figure. Thus both the power amplifiers are optimally used even for signals transmitted on the first antenna.

See also