  Multi-connectivity (MCo) is considered to be a key strategy for enabling
reliable transmissions and enhanced data rates in fifth-generation mobile
networks, as it provides multiple links from source to destination. In this
work, we quantify the communication performance of MCo in terms of outage
probability and throughput. For doing so, we establish a simple, yet accurate
analytical framework at high signal-to-noise ratio (SNR), in which the number
of links, the spectral efficiency, the path loss, and the SNR are incorporated,
giving new insights into the potentials of MCo as compared with
single-connectivity (SCo). These are our main contributions: (1) finding the
exact coding gain of the outage probability for parallel block-fading channels;
(2) quantifying the performance improvement of MCo over SCo in terms of SNR
gain; and (3) comparing optimal and suboptimal combining algorithms for MCo at
the receiver side, namely joint decoding, selection combining, and
maximal-ratio combining, also in terms of SNR gain. Additionally, we apply our
analytical framework to real field channel measurements and thereby illustrate
the potential of MCo to achieve high reliability and high data rates in real
cellular networks.
