6,925 research outputs found
Design guidelines for spatial modulation
A new class of low-complexity, yet energyefficient Multiple-Input Multiple-Output (MIMO) transmission techniques, namely the family of Spatial Modulation (SM) aided MIMOs (SM-MIMO) has emerged. These systems are capable of exploiting the spatial dimensions (i.e. the antenna indices) as an additional dimension invoked for transmitting information, apart from the traditional Amplitude and Phase Modulation (APM). SM is capable of efficiently operating in diverse MIMO configurations in the context of future communication systems. It constitutes a promising transmission candidate for large-scale MIMO design and for the indoor optical wireless communication whilst relying on a single-Radio Frequency (RF) chain. Moreover, SM may also be viewed as an entirely new hybrid modulation scheme, which is still in its infancy. This paper aims for providing a general survey of the SM design framework as well as of its intrinsic limits. In particular, we focus our attention on the associated transceiver design, on spatial constellation optimization, on link adaptation techniques, on distributed/ cooperative protocol design issues, and on their meritorious variants
Non-Orthogonal Contention-Based Access for URLLC Devices with Frequency Diversity
We study coded multichannel random access schemes for ultra-reliable
low-latency uplink transmissions. We concentrate on non-orthogonal access in
the frequency domain, where users transmit over multiple orthogonal subchannels
and inter-user collisions limit the available diversity. Two different models
for contention-based random access over Rayleigh fading resources are
investigated. First, a collision model is considered, in which the packet is
replicated onto available resources, of which are received
without collision, and treated as diversity branches by a maximum-ratio
combining (MRC) receiver. The resulting diversity degree depends on the
arrival process and coding strategy. In the second model, the slots subject to
collisions are also used for MRC, such that the number of diversity branches
is constant, but the resulting combined signal is affected by multiple
access interference. In both models, the performance of random and
deterministic repetition coding is compared. The results show that the
deterministic coding approach can lead to a significantly superior performance
when the arrival rate of the intermittent URLLC transmissions is low.Comment: 2019 IEEE 20th International Workshop on Signal Processing Advances
in Wireless Communications (SPAWC) - Special Session on Signal Processing for
NOMA Communication System
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