Channel Capacity of Near-Field Multiuser Communications
<|reference_start|>Channel Capacity of Near-Field Multiuser Communications: The channel capacity of near-field (NF) communications is characterized by considering three types of multiuser channels: i) multiple access channel (MAC), ii) broadcast channel (BC), and iii) multicast channel (MC). For NF MAC and BC, closed-form expressions are derived for the sum-rate capacity as well as the capacity region under a two-user scenario. These results are further extended to scenarios with an arbitrary number of users. For NF MC, closed-form expressions are derived for the two-user channel capacity and the capacity upper bound with more users. Further insights are gleaned by exploring special cases, including scenarios with infinitely large array apertures, co-directional users, and linear arrays. Theoretical and numerical results are presented and compared with far-field communications to demonstrate that: i) the NF capacity of these three channels converges to finite values rather than growing unboundedly as the number of array elements increases; ii) the capacity of the MAC and BC with co-directional users can be improved by using the additional range dimensions in NF channels to reduce inter-user interference (IUI); and iii) the MC capacity benefits less from the NF effect compared to the MAC and BC, as multicasting is less sensitive to IUI.<|reference_end|>
@article{zhao2024channel,
    title={Channel Capacity of Near-Field Line-of-Sight Multiuser Communications},
    author={Boqun Zhao, Chongjun Ouyang, Xingqi Zhang, Yuanwei Liu},
    journal={arXiv preprint arXiv:2405.05387},
    year={2024},
    archivePrefix={arXiv},
    eprint={2405.05387},
    primaryClass={cs.IT math.IT}
}