  Ultra-dense network (UDN) is one of the enabling technologies to achieve
1000-fold capacity increase in 5G communication systems, and the application of
joint transmission (JT) is an effective method to deal with severe inter-cell
interferences in UDNs. However, most works done for performance analysis on JT
schemes in the literature were based largely on simulation results due to the
difficulties in quantitatively identifying the numbers of desired and
interfering transmitters. In this work, we are motivated to propose an
analytical approach to investigate the performance of JT schemes with a unified
approach based on stochastic geometry, which is in particular useful for
studying different JT methods and conventional transmission schemes without JT.
Using the proposed approach, we can unveil the statistic characteristics (i.e.,
expectation, moment generation function, variance) of desired signal and
interference powers of a given user equipment (UE), and thus system
performances, such as average signal-to-interference-plus-noise ratio (SINR),
and area spectral efficiency, can be evaluated analytically. The simulation
results are used to verify the effectiveness of the proposed unified approach.
