210 research outputs found
Outage Capacity of Bursty Amplify-and-Forward with Incremental Relaying
We derive the outage capacity of a bursty version of the amplify-and-forward
(BAF) protocol for small signal-to-noise ratios when incremental relaying is
used. We show that the ratio between the outage capacities of BAF and the
cut-set bound is independent of the relay position and that BAF is outage
optimal for certain conditions on the target rate R. This is in contrast to
decode-and-forward with incremental relaying, where the relay location strongly
determines the performance of the cooperative protocol. We further derive the
outage capacity for a network consisting of an arbitrary number of relay nodes.
In this case the relays transmit in subsequent partitions of the overall
transmission block and the destination accumulates signal-to-noise ratio until
it is able to decode.Comment: 5 pages, 3 figures, submitted to IEEE International Symposium on
Information Theory, Austin, TX, June 13-18, 201
Energy and Spectral Efficient Inter Base Station Relaying in Cellular Systems
This paper considers a classic relay channel which consists of a source, a relay and a destination node and investigates the energy-spectral efficiency tradeoff under three different relay protocols: amplify-and-forward; decode-and-forward; and compress-and-forward. We focus on a cellular scenario where a neighbour base station can potentially act as the relay node to help on the transmissions of the source base station to its assigned mobile device. We employ a realistic power model and introduce a framework to evaluate the performance of different communication schemes for various deployments in a practical macrocell scenario. The results of this paper demonstrate that the proposed framework can be applied flexibly in practical scenarios to identify the pragmatic energy-spectral efficiency tradeoffs and choose the most appropriate scheme optimising the overall performance of inter base station relaying communications
Link-State Based Decode-Forward Schemes for Two-way Relaying
In this paper, we analyze a composite decode-and-forward scheme for the
two-way relay channel with a direct link. During transmission, our scheme
combines both block Markov coding and an independent coding scheme similar to
network coding at the relay. The main contribution of this work is to examine
how link state impacts the allocation of power between these two distinct
techniques, which in turn governs the necessity of each technique in achieving
the largest transmission rate region. We analytically determine the link-state
regimes and associated relaying techniques. Our results illustrate an
interesting trend: when the user-to-relay link is marginally stronger than the
direct link, it is optimal to use only independent coding. In this case, the
relay need not use full power. However, for larger user-to-relay link gains,
the relay must supplement independent coding with block Markov coding to
achieve the largest rate region. These link-state regimes are important for the
application of two-way relaying in 5G networks, such as in D2D mode or
relay-aided transmission.Comment: To be presented at Globecom 2014, Emerging Technologies for 5G
Wireless Cellular Networks (Wi5G
Multipair Full-Duplex Relaying with Massive Arrays and Linear Processing
We consider a multipair decode-and-forward relay channel, where multiple
sources transmit simultaneously their signals to multiple destinations with the
help of a full-duplex relay station. We assume that the relay station is
equipped with massive arrays, while all sources and destinations have a single
antenna. The relay station uses channel estimates obtained from received pilots
and zero-forcing (ZF) or maximum-ratio combining/maximum-ratio transmission
(MRC/MRT) to process the signals. To reduce significantly the loop interference
effect, we propose two techniques: i) using a massive receive antenna array; or
ii) using a massive transmit antenna array together with very low transmit
power at the relay station. We derive an exact achievable rate in closed-form
for MRC/MRT processing and an analytical approximation of the achievable rate
for ZF processing. This approximation is very tight, especially for large
number of relay station antennas. These closed-form expressions enable us to
determine the regions where the full-duplex mode outperforms the half-duplex
mode, as well as, to design an optimal power allocation scheme. This optimal
power allocation scheme aims to maximize the energy efficiency for a given sum
spectral efficiency and under peak power constraints at the relay station and
sources. Numerical results verify the effectiveness of the optimal power
allocation scheme. Furthermore, we show that, by doubling the number of
transmit/receive antennas at the relay station, the transmit power of each
source and of the relay station can be reduced by 1.5dB if the pilot power is
equal to the signal power, and by 3dB if the pilot power is kept fixed, while
maintaining a given quality-of-service
Multi-antenna aspects of wireless fixed relays
Abstract — Multiple antenna schemes can provide performance enhancement but the small size and cost constraints of wireless terminals preclude their use at these terminals. This paper investigates distributed fixed relays (infrastructure-based relaying) which are engaged in cooperation in a two-hop wireless network as a means of removing the burden of multiple antennas on wireless terminals. In contrast to mobile terminals, a small number of antennas can be deployed on infrastructure-based fixed relays. Hence, the paper investigates performance of the distributed cooperative multi-antenna fixed relays. Threshold maximal ratio combining and threshold selection combining of these multiple antenna signals are studied and analyzed. The following results are derived. For a given performance requirement, the multiple antennas at relays can significantly reduce the number of relays required in a network area, ultimately, reducing system deployment cost. In addition, threshold selection combining at the relays represents an excellent compromise between performance and system cost. Finally, the analysis performed in this paper uses the versatile Nakagami fading channel model. I
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