  Recently, semantic communication (SemCom) has shown great potential in
significant resource savings and efficient information exchanges, thus
naturally introducing a novel and practical cellular network paradigm where two
modes of SemCom and conventional bit communication (BitCom) coexist.
Nevertheless, the involved wireless resource management becomes rather
complicated and challenging, given the unique background knowledge matching and
time-consuming semantic coding requirements in SemCom. To this end, this paper
jointly investigates user association (UA), mode selection (MS), and bandwidth
allocation (BA) problems in a hybrid semantic/bit communication network
(HSB-Net). Concretely, we first identify a unified performance metric of
message throughput for both SemCom and BitCom links. Next, we specially develop
a knowledge matching-aware two-stage tandem packet queuing model and
theoretically derive the average packet loss ratio and queuing latency.
Combined with practical constraints, we then formulate a joint optimization
problem for UA, MS, and BA to maximize the overall message throughput of
HSB-Net. Afterward, we propose an optimal resource management strategy by
utilizing a Lagrange primal-dual transformation method and a preference
list-based heuristic algorithm with polynomial-time complexity. Numerical
results not only demonstrate the accuracy of our analytical queuing model, but
also validate the performance superiority of our proposed strategy compared
with different benchmarks.
