Multi-band Wireless Communication Networks: Fundamentals, Challenges,
and Resource Allocation
Abstract
The sub-6 GHz spectrum and the millimeter wave frequency band, with its
huge spectrum, have been exploited in the past years to meet the traffic
demands of wireless communication networks. However, the limited and
licensed spectrum of these bands cannot support the massive connectivity
requirements, the exponential growth of data traffic, and the strict
quality-of-service requirements for 6G and beyond wireless systems.
Extremely high frequencies, such as optical and terahertz, which offer
much wider transmission bandwidths with extreme data rate capabilities,
are expected to play key roles in the 6G and beyond era. As a result,
future-generation wireless networks will transition from single-band and
heterogeneous networks to multi-band networks (MBNs), where various
frequency bands coexist. Despite the great potential of MBNs, they face
novel challenges from channel modeling, transceiver and antenna design,
programmable simulation platforms, standardization activities, and
resource allocation. This paper provides a tutorial overview from the
communication design perspective of the various frequency bands,
elaborating on the above issues. Then, we introduce and examine typical
MBN architectures for future networks and provide a detailed overview of
state-of-the-art resource allocation problems for existing MBNs that
typically operate on two frequency bands. The considered resource
allocation optimization problems and solution techniques are discussed
comprehensively. We then identify key performance metrics and constraint
sets that should be considered for resource allocation optimization in
future MBNs and provide numerical results to depict how various system
parameters and user behaviors can influence their performance. Finally,
we present several potential research issues as future work for the
design and performance optimization of MBNs.