The fast increase of users in existing mobile networks requires more base stations (BSs) to bear more communication traffic. Future heterogeneous network is considered to be a promising candidate architecture to meet the demands of wireless networks under scarcity of radio frequency (RF) resources. In this paper. we present a multi-mode relay (MMR) model based on two-way relay technol... https://www.ossgroupltd.com/product-category/religious-art/