Abstract
We study the potential benefits of base-station (BS) cooperation for downlink transmission in multicell networks. Based on a modified Wyner-type model with users clustered at the cell-edges, we analyze the dirty-paper-coding (DPC) precoder and several linear precoding schemes, including cophasing, zero-forcing (ZF), and MMSE precoders. For the nonfading scenario with random phases, we obtain analytical performance expressions for each scheme. In particular, we characterize the high signal-to-noise ratio (SNR) performance gap between the DPC and ZF precoders in large networks, which indicates a singularity problem in certain network settings. Moreover, we demonstrate that the MMSE precoder does not completely resolve the singularity problem. However, by incorporating path gain fading, we numerically show that the singularity problem can be eased by linear precoding techniques aided with multiuser selection. By extending our network model to include cell-interior users, we determine the capacity regions of the two classes of users for various cooperative strategies. In addition to an outer bound and a baseline scheme, we also consider several locally cooperative transmission approaches. The resulting capacity regions show the tradeoff between the performance improvement and the requirement for BS cooperation, signal processing complexity, and channel state information at the transmitter (CSIT).
Highlights
The growing popularity of various high-speed wireless applications necessitates a fundamental characterization of wireless channels
We investigated the potential benefits of cooperative downlink transmission in multicell networks
In single-class networks where the users are clustered at the cell-edges, we have obtained analytical performance expressions for DPC, cophasing, ZF, and MMSE precoders
Summary
The growing popularity of various high-speed wireless applications necessitates a fundamental characterization of wireless channels. We have shown that if each user sees two strong paths, the sum rate performances of the ZF and MMSE precoders (combined with intra-cell TDM) deteriorate significantly in large networks, while the performance deterioration is less severe if the two paths to each user are of unequal strength To address this singularity problem, we induce the path gain asymmetry by incorporating path gain fading into our network model and combining multiuser scheduling with the linear precoders. For the nonfading scenario with random path phases, we have derived the analytical sum rate expressions for several cooperative downlink transmission schemes, identified a connection between the three linear precoders (cophasing, ZF, and MMSE) and a singularity problem with the linear precoding schemes in large networks. We will define both the downlink and the dual uplink channels, since we will frequently use the uplinkdownlinkduality [17,18,19] in our analysis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: EURASIP Journal on Wireless Communications and Networking
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
