Multi-user spatial diversity in a shadow-fading environment

Emamian, Vahid; Anghel, P.A.; Kaveh, M.

doi:10.1109/vetecf.2002.1040409

Cited by 75 publications

(47 citation statements)

References 5 publications

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“…If the relay has instantaneous knowledge of the fading channel, h1, it can apply variable gain relaying with G v P2/Es 1 ,ν 1 {|y1| 2 } [14]. Otherwise, fixed gain relaying with G f P2/E s 1 ,ν 1 ,h 1 {|y1| 2 } can be applied using only statistical information [2].…”

Section: Ideal Hardwarementioning

confidence: 99%

On the impact of transceiver impairments on af relaying

Björnson¹,

Papadogiannis

Matthaiou

et al. 2013

2013 IEEE International Conference on Acoustics, Speech and Signal Processing

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Recently, it was shown that transceiver hardware impairments have a detrimental impact on the performance of communication systems, especially for high-rate systems. The vast majority of technical contributions in the area of relaying assume ideal transceiver hardware. This paper quantifies the impact of transceiver hardware impairments in dual-hop Amplify-and-Forward (AF) relaying, both for fixed and variable gain relays. The outage probability (OP) in this practical scenario is a function of the instantaneous end-toend signal-to-noise-and-distortion ratio (SNDR). This paper derives closed-form expressions for the exact and asymptotic OPs under Rayleigh fading, accounting for hardware impairments at both the transmitter and the relay. The performance loss is small at low spectral efficiency, but can otherwise be very substantial. In particular, it turns out that for high signal-to-noise ratio (SNR), the instantaneous end-to-end SNDR converges to a deterministic constant, called the SNDR ceiling, which is inversely proportional to the level of impairments. This stands in stark contrast to the ideal hardware case for which the end-to-end SNDR grows without bound in the high SNR regime.

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Section: Ideal Hardwarementioning

confidence: 99%

On the impact of transceiver impairments on af relaying

Björnson¹,

Papadogiannis

Matthaiou

et al. 2013

2013 IEEE International Conference on Acoustics, Speech and Signal Processing

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“…On the other hand, the average number of active relays in the COT system is calculated using (12). The outage probability of both systems is obtained from (4). In the DOT system, SR g and SR…”

Section: ⅴ Numerical Examplesmentioning

confidence: 99%

Double Opportunistic Transmit Cooperative Relaying System with GSC in Rayleigh Fading Channels

Kim¹,

Lee²

2010

Journal of electromagnetic engineering and science

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In a conventional opportunistic transmit (COT) cooperative relaying system, only the relays that receive signal-to-noise ratio (SNR) from the source and that exceed the threshold transmit to the destination. The COT system, however, only considers the SNR of the source-relay (S-R) path regardless that the SNR of the relay-destination (R-D) path is the opportunistic transmission condition. For that reason, it is not guaranteed that all the transmitted signals from relays exceed the threshold at the destination. Therefore we propose a double opportunistic transmit (DOT) cooperative relaying system -when both of the received SNR from a source and from a destination exceed the threshold, the relay transmits to the destination. It is shown that the proposed DOT system reduces power consumption by 6.9, 20.9, 32.4, and 41.4 % for K =3, 5, 7, and 9, respectively under the given condition of Pout=1×10 Ⅰ. IntroductionAd-hoc networks have focused on key technology for next generation wireless systems. However, the power consumption of wireless ad-hoc networks is critical to maintain network lifetime and communication reliability [1]. Recently, cooperative diversity has been applied to wireless ad-hoc networks to reduce power consumption and improve system performance by mitigating the fading effects of wireless channels [2～5].Most cooperative diversity systems adapt opportunistic transmission with decode-and-forward (DF) relays [6,7]. In this conventional opportunistic transmit (COT) relaying system, when the received signal-to-noise ratio (SNR) exceeds the threshold, the relay transmits. The COT system, however, only considers the SNR of the sourcerelay (S-R) path regardless of the SNR of the relay-destination (R-D) path.For that reason, it cannot be guaranteed that all the transmitted signals from the opportunistic relays will satisfy the target threshold of a destination.Moreover, the number of diversity branches (i.e., rake receiver fingers) of a receiver at a destination is usually limited. The excess number of transmit relays compared to the number of rake receiver fingers causes undue power consumption and interferes with other systems. On the other hand, fewer transmit relays cause performance degradation.To improve system performance in fading channels, generalized selection combining (GSC) was introduced [8～10]. GSC adaptively combines Lc strong signals among L signals. If we apply GSC to the COT, the strong L c signals received from relays are selected up to the limited number of branches and combines, which has better performance than maximal ratio combining (MRC) with arbitrary selection among L signals. However GSC requires additional power consumption to order the received signals.In this paper, we propose a double opportunistic transmit (DOT) relaying system that considers both SNRs from S-R and R-D paths. By monitoring the received SNRs from a source and from a destination, the DOT system has the following functions by adjusting the threshold at a relay: (a) it controls the average number of trans...

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“…When terminal R has available CSI from the first hop, one kind of gain relay proposed and studied in previously published works [8,9], is given by…”

Section: Mode Of Operationmentioning

confidence: 99%

“…If 7 t h is a certain specified threshold ratio, then for non-regenerative multihop transmissions the outage probability is defined as the probability that the instantaneous SNR at the final destination falls below yth and is expressed as Following the same method as in [9], the above integral yields to where K1 (.) is the first order modified Bessel function of the second kind defined in [ l 1, eq.…”

Section: Outage Probabilitymentioning

confidence: 99%

Wireless Transmissions with Combined Gain Relays over Fading Channels

Tsiftsis

Karagiannidis

Kotsopoulos

2006

Challenges in Ad Hoc Networking

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We present a dual-hop relayed wireless communication system where the gain of the relay, called combined gain relay (CGR), is produced after combining the channel state information from both hops, depending on the mean hop's signal-to-noise ratio (SNR). The proposed scheme can be efficiently applied in dual-hop transmissions with unbalanced mean SNRs due to the long-term fading effects produced by the movement of the user in the area served by the wireless network. The overall system performance is studied in Rayleigh fading channels. Closed-form expressions are derived for important system performance metrics, such as average end-to-end SNR, average error probability and outage probability. Furthermore, we investigate the CGR's average power consumption which in certain cases is lower compared to existed relays. Numerical results and simulations show an improvement in the end-to-end system performance.

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Multi-user spatial diversity in a shadow-fading environment

Cited by 75 publications

References 5 publications

On the impact of transceiver impairments on af relaying

On the impact of transceiver impairments on af relaying

Double Opportunistic Transmit Cooperative Relaying System with GSC in Rayleigh Fading Channels

Wireless Transmissions with Combined Gain Relays over Fading Channels

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