  This paper presents a tractable model for analyzing non-coherent joint
transmission base station (BS) cooperation, taking into account the irregular
BS deployment typically encountered in practice. Besides cellular-network
specific aspects such as BS density, channel fading, average path loss and
interference, the model also captures relevant cooperation mechanisms including
user-centric BS clustering and channel-dependent cooperation activation. The
locations of all BSs are modeled by a Poisson point process. Using tools from
stochastic geometry, the signal-to-interference-plus-noise ratio
($\mathtt{SINR}$) distribution with cooperation is precisely characterized in a
generality-preserving form. The result is then applied to practical design
problems of recent interest. We find that increasing the network-wide BS
density improves the $\mathtt{SINR}$, while the gains increase with the path
loss exponent. For pilot-based channel estimation, the average spectral
efficiency saturates at cluster sizes of around $7$ BSs for typical values,
irrespective of backhaul quality. Finally, it is shown that intra-cluster
frequency reuse is favorable in moderately loaded cells with generous
cooperation activation, while intra-cluster coordinated scheduling may be
better in lightly loaded cells with conservative cooperation activation.
