Impairment modeling for joint transmission CoMP

Base station coordination is envisioned as a key technology in future mobile networks. It reduces the interference between adjacent cells and promises enhancement of spectral efficiency. However, little is known about the penalties due to impairments. Channel errors may be caused by channel estimation, feedback delay as well as by synchronization errors among the base stations. Hence, the computation of the precoder relies on imprecise information and the orthogonality between the user data is disturbed. In this paper, we give an overview on potential impairment effects. We derive an accurate signal model capturing the effect of synchronization impairments depending on the feedback delay. The resulting interference levels must not be larger than the one obtained after cooperation of the base stations in the cluster being limited by interference of non-coordinated base stations surrounding the cluster. We introduce an equivalent mean square error for these impairment effects, propose a practical way to evaluate the corresponding performance degradation and discuss compensation mechanisms.