Mathematical Description
In a multiple antenna downlink system which comprises a transmit antenna access point (AP) and single receive antenna users, the received signal of user is described as
where is the vector of transmitted symbols, is the noise signal, is the channel vector and is the linear precoding vector. From the fact that each beam generated by ZF-precoding is orthogonal to all the other user channel vectors, one can rewrite the received signal as
For comparison purpose, we describe the received signal model for multiple antenna uplink systems. In the uplink system with a receiver antenna AP and K single transmit antenna user, the received signal at the AP is described as
where is the transmitted signal of user, is the noise vector, is the channel vector.
Read more about this topic: Zero-forcing Precoding
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