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This paper focuses on multirate IEEE 802.11 Wireless LAN employing the mandatory Distributed Coordination Function (DCF) option. Its aim is threefold. Upon starting from the multi-dimensional Markovian state transition model proposed by Malone \textit{et.al.} for characterizing the behavior of the IEEE 802.11 protocol at the Medium Access Control layer, it presents an extension accounting for packet transmission failures due to channel errors. Second, it establishes the conditions under which a network constituted by $N$ stations, each station transmitting with its own bit rate, $R^{(s)}_d$, and packet rate, $\lambda_s$, can be assumed loaded. Finally, it proposes a modified Proportional Fairness (PF) criterion, suitable for mitigating the \textit{rate anomaly} problem of multirate loaded IEEE 802.11 Wireless LANs, employing the mandatory DCF option. Compared to the widely adopted assumption of saturated network, the proposed fairness criterion can be applied to general loaded networks. The throughput allocation resulting from the proposed algorithm is able to greatly increase the aggregate throughput of the DCF, while ensuring fairness levels among the stations of the same order as the ones guaranteed by the classical PF criterion. Simulation results are presented for some sample scenarios, confirming the effectiveness of the proposed criterion for optimized throughput allocation., Comment: Submitted to IEEE Transaction on Wireless Communications, September 2008

This paper presents a modified proportional fairness (PF) criterion suitable for mitigating the \textit{rate anomaly} problem of multirate IEEE 802.11 Wireless LANs employing the mandatory Distributed Coordination Function (DCF) option. Compared to the widely adopted assumption of saturated network, the proposed criterion can be applied to general networks whereby the contending stations are characterized by specific packet arrival rates, $\lambda_s$, and transmission rates $R_d^{s}$. The throughput allocation resulting from the proposed algorithm is able to greatly increase the aggregate throughput of the DCF while ensuring fairness levels among the stations of the same order of the ones available with the classical PF criterion. Put simply, each station is allocated a throughput that depends on a suitable normalization of its packet rate, which, to some extent, measures the frequency by which the station tries to gain access to the channel. Simulation results are presented for some sample scenarios, confirming the effectiveness of the proposed criterion., Comment: Submitted to IEEE CCNC 2009

This paper presents a modified proportional fairness (PF) criterion suitable for mitigating the \textit{rate anomaly} problem of multirate IEEE 802.11 Wireless LANs employing the mandatory Distributed Coordination Function (DCF) option. Compared to the widely adopted assumption of saturated network, the proposed criterion can be applied to general networks whereby the contending stations are characterized by specific packet arrival rates, $\lambda_s$, and transmission rates $R_d^{s}$. The throughput allocation resulting from the proposed algorithm is able to greatly increase the aggregate throughput of the DCF while ensuring fairness levels among the stations of the same order of the ones available with the classical PF criterion. Put simply, each station is allocated a throughput that depends on a suitable normalization of its packet rate, which, to some extent, measures the frequency by which the station tries to gain access to the channel. Simulation results are presented for some sample scenarios, confirming the effectiveness of the proposed criterion., Comment: 5 pages, 2 figures, submitted to IEEE Globecom 2008, March 2008

The aim of this paper is twofold. On one hand, it presents a multi-dimensional Markovian state transition model characterizing the behavior at the Medium Access Control (MAC) layer by including transmission states that account for packet transmission failures due to errors caused by propagation through the channel, along with a state characterizing the system when there are no packets to be transmitted in the queue of a station (to model non-saturated traffic conditions). On the other hand, it provides a throughput analysis of the IEEE 802.11 protocol at the data link layer in both saturated and non-saturated traffic conditions taking into account the impact of both transmission channel and multirate transmission in Rayleigh fading environment. Simulation results closely match the theoretical derivations confirming the effectiveness of the proposed model., Comment: Accepted at IEEE WCNC 2008, Las Vegas

Plasma lipoprotein (a) [Lp (a)] levels, positively and independently associated with a risk for the development of atherosclerotic disorders, are under relatively strict genetic control. Consequently, the distribution of Lp (a) in general population shows characteristics that differ from those of others lipoproteins: wide variability among individuals (0->100 mg/dl), among populations. Therefore, population-based reference values, as well as the concentration at which Lp (a) is considered to be a risk factor, should be established for each population. This report analyzes Lp (a) distribution in a sample of general population of Bressana, Pavia, Italy (702 subjects; 339 males and 363 female; age 20-59 years). Lp (a) levels are measured with an enzyme-linked immunosorbent assay (TintElize Lp (a) -Menarini Diagnostics). The first hypothesis concerns the normality of the distribution of Lp (a). The analysis shows a statistically significant deviation from normality of the distribution of Lp (a) frequency (strong skewness toward the right: the curve is compressed in the values < 10 mg/dl, and leptokurtosis) .....................................................................................Lipoprotein (a) distribution in our examined general population sample shows a highly positive skewness according to litarure. Lp (a) distribution has been repeatedly examined, yet a few studies have included data of general populations, and, also in this case, not all the studies have provided appropriate measures to characterize the distribution of the Lp (a) when this distribution was not-normal. Conseguently, for epidemiological aims, we think it is advisable to show the values (mg/dl) of the 25th, 50th, 75th percentiles of the Lp (a) distribution: total sample (4,0; 9,5; 24,0) ; males (3,0; 8,7; 23,0) ; females (4,0; 10,0; 25,0).