We consider a distributed antenna system where $L$ antenna terminals (ATs)
are connected to a Central Processor (CP) via digital error-free links of
finite capacity $R_0$, and serve $L$ user terminals (UTs). This system model
has been widely investigated both for the uplink and the downlink, which are
instances of the general multiple-access relay and broadcast relay networks. In
this work we focus on the downlink, and propose a novel downlink precoding
scheme nicknamed "Reverse Quantized Compute and Forward" (RQCoF).

We suggest a novel approach to handle the ongoing explosive increase in the
demand for video content in wireless/mobile devices. We envision femtocell-like
base stations, which we call helpers, with weak backhaul links but large
storage capacity. These helpers form a wireless distributed caching network
that assists the macro base station by handling requests of popular files that
have been cached. Due to the short distances between helpers and requesting
devices, the transmission of cached files can be done very efficiently.

We revisit a recent result by Etkin, Tse, and Wang on achieving the capacity
of the Gaussian interference channel to within one bit using a fixed
Han-Kobayashi message splitting strategy. In particular, we show that the one
bit gap is not always attainable, specifically on the corners of the rate
region, by using a fixed power splitting scheme. The one-bit gap result is
proved by comparing an achievable rate region due to Chong et al. (also known
as the CMG region) with new upper bounds for the capacity region derived by
Etkin, Tse, and Wang.

We consider the problem of designing low latency and low complexity schemes
for channel state feedback over the MIMO-MAC (multiple-input multiple-output
multiple access channel). We develop a framework for analyzing this problem in
terms of minimizing the MSE distortion, and come up with separated
source-channel schemes and joint source-channel schemes that perform better
than analog feedback.

User scheduling and multiuser multi-antenna (MU-MIMO) transmission are at the
core of high rate data-oriented downlink schemes of the next-generation of
cellular systems (e.g., LTE-Advanced). Scheduling selects groups of users
according to their channels vector directions and SINR levels. However, when
scheduling is applied independently in each cell, the inter-cell interference
(ICI) power at each user receiver is not known in advance since it changes at
each new scheduling slot depending on the scheduling decisions of all
interfering base stations.

We consider a MIMO fading broadcast channel where the fading channel
coefficients are constant over time-frequency blocks that span a coherent time
$\times$ a coherence bandwidth. In closed-loop systems, channel state
information at transmitter (CSIT) is acquired by the downlink training sent by
the base station and an explicit feedback from each user terminal. In open-loop
systems, CSIT is obtained by exploiting uplink training and channel
reciprocity.