  Towards the upcoming 6G wireless networks, integrated sensing and
communication (ISAC) has been identified as one of the typical usage scenarios.
To further enhance the performance of ISAC, increasing the number of antennas
as well as array aperture is one of the effective approaches. However, simply
increasing the number of antennas will increase the cost of radio frequency
chains and power consumption. To address this issue, in this paper, we consider
an uplink ISAC system with nested array deployed at the base station. Nested
array is a classic sparse array architecture that is able to enlarge the array
aperture without increasing the number of physical antennas. While nested array
for wireless sensing has been extensively studied, its potential for ISAC
system has not been fully exploited. To fill this gap, in this paper, we
provide the beam pattern analysis of nested arrays, and derive the closed-form
expressions for the three beam pattern metrics, namely, the main lobe beam
width, peak-to-local-minimum ratio, and prominent side lobes height. Extensive
simulation results are provided to show that compared with conventional uniform
arrays, nested arrays can achieve higher communication performance for densely
located users while maintaining its advantage of sensing.
