Outage Average Rate Research Articles

Fluid Antenna Multiple Access

Fluid antenna system represents an emerging technology that enables an antenna to switch its physical location in a predefined space. This paper explores the potential of using a single fluid antenna at each mobile user for multiple access, which we refer to it as fluid antenna multiple access (FAMA). FAMA exploits spatial moments of deep fade suffered by the interference to achieve a favourable channel condition for the desired signal, without requiring sophisticated signal processing. We analyze the FAMA network by first deriving the outage probability of the signal-to-interference ratio (SIR) in a double integral form. We then obtain an outage probability upper bound in closed form and an average outage rate lower bound for the FAMA system, with an arbitrary number of interferers, from which the multiplexing gain of FAMA is characterized. We also estimate how large the number of locations is required to achieve a given multiplexing gain using fluid antennas with a given size. Results show that it is possible for FAMA to support hundreds of users using only one fluid antenna of a few wavelengths of space at each user, giving rise to significant gain in the average network outage rate.

Impact of maximum transmit power limit on the first-order and second-order performance of cognitive opportunistic relaying

This paper focuses on the first-order and second-order performance of dual-hop underlay cognitive radio systems with opportunistic relaying (UCR-OR) over independent and non-identically distributed (i.ni.d) Rayleigh fading channels. For the UCR-OR systems, the tolerable maximum interference power (TMIP) Q at primary users (PUs) and the allowable maximum transmission power limit (AMTP) Pmax at secondary users (SUs) are considered, simultaneously. We first obtain the closed-form solutions to the first-order performance such as outage probability, average symbol error ratio (SER), and ergodic capacity (EC). Secondly, we investigate the second-order statistical performance, i.e., average outage rate (AOR) and average outage duration (AOD). With the consideration that in practice implementation the receiver performance is primarily influenced by the signal-to-noise ratio (SNR) (not the signal envelope), the second-order statistical performance is investigated based on the equivalent instantaneous end-to-end SNR. Finally, we present the detailed performance comparison analysis of UCR-OR systems by defining a random variable μ=Pmax/Q. The results show that the effect of μ on the first-order and second-order performances is different greatly. For the first-order performance, the performance gap is negligible when the value of μ is relatively large. However, for the second-order one, the gap is distinct.

Cognitive opportunistic relaying systems with mobile nodes: average outage rates and outage durations

In the existing literature about cognitive radio opportunistic relaying (CR-OR) systems, the first-order statistics such as outage probability are investigated widely. However, for the second-order statistics, such as average outage duration (AOD) and average outage rate (AOR), there is not open works, still. To obtain a comprehensive cognition on the behaviour of mobile communication systems, this study focuses on the second-order statistical properties of CR-OR systems. There are two CR-OR schemes considered, in which the canonical amplify-and-forward (AF) and reactive decode-and-forward (RDF) are employed, respectively. Since the equivalent end-to-end signal-to-noise ratio (SNR) of AF CR-OR is complicated such that it is very difficult to obtain the closed-form solution to AOR of AF CR-OR schemes, the high SNR approximation in AF CR-OR schemes is employed. For the two schemes, first the closed-form solutions to AORs and AODs are obtained by using appropriate mathematical proof. Based on the derivations, the comparison analyses about AORs and AODs of the two schemes are provided. The comparison results show that, under high SNR approximation, the AF CR-OR scheme achieves the same AOR and AOD as RDF CR-OR. Finally, the impact of system parameters on AORs and AODs is provided.

Study on the Statistical Performance of Relay Cooperation Over Non-Isotropic Mobile-to-Mobile Nakagami-<i>m</i> Fading Channels

This work focuses on the investigation of the second-order statistical descriptions for full mobile wireless networks over non-isotropic Nakagami-mfading environment. The system consists of a source, a relay, and K destination users, all of which are mobile. For the full mobile system model, we first extend the Akki and Habers mobile-to-mobile (M2M) model to non-isotropic scattering fading channels by adopting the von Mises PDF for both the angle of arrival (AnOA) and the angle of departure (AnOD). With appropriate mathematical proof, we obtain the approximate solution to the correlation function of M2M Nakagami-mfading channel envelop, and the variance of the first derivative. Secondly, using the obtained correlation, we study the average outage rate (AOR) and the average outage duration (AOD) of the multi-user single relay cooperation system in detail, and obtain the closed-form analytical expressions to AOR and AOD.

Outage rates and outage durations of opportunistic relaying systems

Opportunistic relaying is a simple yet efficient cooperation scheme that achieves full diversity and preserves the spectral efficiency among the spatially distributed stations. However, the stations' mobility causes temporal correlation of the system's capacity outage events, which gives rise to its important second-order outage statistical parameters, such as the average outage rate (AOR) and the average outage duration (AOD). This letter presents exact analytical expressions for the AOR and the AOD of an opportunistic relaying system, which employs a mobile source and a mobile destination (without a direct path), and an arbitrary number of (fixed-gain amplify-and-forward or decode-and-forward) mobile relays in Rayleigh fading environment.

On the Average Outage Rate and Average Outage Duration of Wireless Communication Systems With Multiple Cochannel Interferers

This paper studies the average outage rate [or average level crossing rate (LCR)] and average outage duration (AOD) of wireless communication systems subject to cochannel interference. In particular, it presents closed-form expressions for the LCR and AOD when a minimum desired signal power requirement is specified for satisfactory reception. The results are quite general and account for systems operating over independent identically distributed Rician and/or Nakagami fading environments. When applicable, these new expressions are compared to those previously reported in the literature dealing with the LCR and AOD of 1) interference-limited systems when both the desired and interfering signals are subject to Rayleigh type of fading and 2) power-limited systems operating over Rician or Nakagami fading channels. Corresponding numerical examples that illustrate applications of the results are also provided and discussed. These results show that specifying a certain minimum desired signal power requirement induces a floor on the AOD. They also show that the AOD is essentially affected by the the maximum Doppler frequencies (or equivalently the speed) of the desired users.

Outage Perforformance of Power Controlled DS-CDMA Wireless Systems with Heterogeneous Traffic Sources

This paper proposes a performance analysis of a Direct Sequence-Code Division Multiple Access (DS-CDMA) wireless system with heterogeneous traffic in terms of second order outage statistics. Imperfections in closed-loop power control are modelled in their first order distribution and autocorrelation function. System capacity and optimal power allocation has been previously derived [7] in the presence of requirements expressed only in terms of signal-to-(noise + interference) ratio and outage probability of every user in the system. Therefore, in this paper the effectiveness of power allocation is evaluated also in terms of average outage rate and average outage duration for the generic user link of each traffic class. This allows to gain insights on the effects of power allocation and feedback control on channel burstiness for each class of users, so that forward error correction and retransmission strategies can be properly tuned. With proper choice of system parameters, the proposed analysis can be applied to both the terrestrial and satellite segments of 3G systems, and integrated scenarios as well.