  Wireless mesh networks play a critical role in enabling key networking
scenarios in beyond-5G (B5G) and 6G networks, including integrated access and
backhaul (IAB), multi-hop sidelinks, and V2X. However, it still poses a
challenge to deliver scalable per-node throughput via mesh networking, which
significantly limits the potential of large-scale deployment of wireless mesh
networks. Existing research has achieved $O(1)$ per-node throughput in a dense
network, but how to achieve scalability remains an unresolved issue for an
extended wireless network where the network size increases with a constant node
density. This issue prevents a wireless mesh network from large-scale
deployment. To this end, this paper aims to develop a theoretical approach to
achieving scalable per-node throughput in wireless mesh networks. First, the
key factors that limit the per-node throughput of wireless mesh networks are
analyzed, through which two major ones are identified, i.e., link sharing and
interference. Next, a multi-tier hierarchical architecture is proposed to
overcome the link-sharing issue. The inter-tier interference under this
architecture is then mitigated by utilizing orthogonal frequency allocation
between adjacent tiers, while the intra-tier interference is reduced by
considering two specific transmission schemes, one is MIMO spatial multiplexing
with time-division, the other is MIMO beamforming. Theoretical analysis shows
that the multi-tier mesh networking architecture can achieve a per-node
throughput of $\Theta(1)$ in both schemes, as long as certain conditions on
network parameters including bandwidth, antenna numbers, and node numbers of
each tier are satisfied. A case study on a realistic deployment of 10,000 nodes
is then carried out, which demonstrates that a scalable throughput of
$\Theta(1)$ is achievable with a reasonable assumption on bandwidth and antenna
numbers.
