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The link schedule of a wireless network must ensure links receive sufficient transmission opportunities or time slots to meet their offered load. To date, existing link schedulers assume fixed link load. In practice, link load is likely to vary, meaning the computed schedule or superframe will have unnecessary idle times. In this letter, we propose to use stochastic programming (SP) to generate a superframe comprising of a Time Division Multiple Access (TDMA) and a random access part. Advantageously, it sizes both parts according to traffic distribution. We show how it can be used to derive a superframe for multi transmit (Tx) or receive (Rx) wireless networks. We show via numerical results the efficacy of our approach in reducing idle times and collisions given random demands.

HTTP progressive video downloading is becoming increasingly relevant in wireless and mobile networks. Therefore, improving the quality of experience (QoE) for this service is important for customer satisfaction. In this letter we propose a QoE-aware scheduling solution for the HTTP progressive video downloading in OFDMA systems. Whereas most scheduling strategies consider QoS metrics such as delay, jitter or throughput, our proposal takes into account a metric that directly affects the end-users experience. In particular, we propose to use an estimation of the amount of video data stored in the player buffer as the main criterion for resource assignment. The ultimate goal of using this criterion is the avoidance of playback interruptions. In particular, we have evaluated this scheduler in an LTE network simulator for the YouTube service, which is the most visited HTTP video streaming site. Our results show a significant improvement compared to the Multicarrier Proportional Fair scheduler, e.g. the number of videos with pauses decrease from 16.1% to 0% for 12 Mbps of cell offered load.

In this letter, a reservation scheme with contention resolution diversity slotted ALOHA (CRDSA), called R-CRDSA, is proposed. Although CRDSA promises excellent performance compared to slotted ALOHA (SA), there are two barriers to be overcome for its use in satellite networks. The first is a low critical point of an offered load; i.e., at this point, as the offered load increases, the throughput will decrease. CRDSA has a lower critical point than that of SA. The second barrier is that CRDSA has a lower capacity efficiency compared to SA; i.e., on average, CRDSA requires more power or bandwidth than SA for transmission. R-CRDSA can overcome these barriers at the same cost as CRDSA, especially for multi-packet messages. The analytic performances are derived by the observation of the transition between two successive frames, and the average number of packets in a message. The simulation results show that the analytic derivations are valid, and they confirm that the barriers are resolved by R-CRDSA.

We provide an analytical proof that the departure rate of a CBR flow at an overloaded link with FIFO buffers is proportional to the flow's share of the total offered load at the link. This property of FIFO scheduling was recently validated in in a series of traffic measurement experiments. An extension of the analysis to a multi-node scenario shows that the output rate of a flow in a network with many overloaded FIFO switches approaches the pessimistic values given by blind multiplexing.

This letter presents an analytical model that can be used to evaluate the blocking probability of each service class in a multi-class optical burst-switching network. The model allows, for the first time, the evaluation of blocking probabilities in optical burst switching (OBS) systems with arbitrary burst-length distributions and arbitrary offsets. This includes OBS systems in which the mean burst length of each class is different. Such systems do not follow the conservation law and cannot, therefore, be analyzed using previously published OBS models. For an OBS system with two classes, an offered load of 10/sup -3/, and a 1:5 ratio of high-priority to low-priority traffic, we show that our model accurately predicts the blocking probability for each class, whereas predictions from previously published models that assume conservation disagree with the simulation results by as much as 75%.

In this letter, we propose a computational model for calculating blocking probabilities of multifiber wavelength division multiplexing (WDM) optical networks. We first derive the blocking probability of a fiber based on a Markov chain, from which the blocking probability of a link is derived by means of conditional probabilities. The blocking probability of a lightpath can be computed by a recursive formula. Finally, the network-wide blocking probability can be expressed as the ratio of the total blocked load versus the total offered load. Simulation results for different fiber-wavelength configurations conform closely to the numerical results based on our proposed model, thus demonstrating the feasibility of our proposed model for estimating the blocking performance of multifiber WDM optical networks.

This letter presents a mobility session redirection scheme for Proxy Mobile IPv6 networks (PMIPv6-MSR), facilitating LMA changes in the middle of a mobility session for, e.g. load-balancing purpose. Analytical results confirm that the proposed PMIPv6-MSR shows lower blocking and dropping probability than PMIPv6 without load control (PMIPv6-NLC), as offered load increases.

We derive the asymptotic behavior of the ratio between the blocking probabilities of burst segmentation (BS) and just-enough-time (JET) policies in an optical burst switch. It is shown that if the ratio between the offered load and the number of wavelengths, k, is fixed and equals c as the number of wavelengths approaches infinity, the ratio between the blocking probabilities of BS and JET approaches 1 if c > 1; 0.5 if c = 1; and is O(1/k) with a constant c/(1 - c)/sup 2/ if c < 1.

In previous studies, a criterion has been developed that guarantees stability of a slotted ALOHA system, provided the offered load is below a certain upper bound. This is done by selecting the control parameters through consideration of the estimated drift characteristics. A new joint drift analysis is presented that provides a sequential method for choosing control parameters so as to eliminate bistable operation and guarantee system stability not only below the upper bound referred to earlier, but also above the bound. In addition, the proposed strategy achieves maximum throughput for the system.

In a personal communications services (PCS) network, the network delay for a handoff request is limited by a timeout period. If the network fails to respond within the timeout period, the handoff call is forced terminated. We study the effect of the network response time on the performance (the call incompletion probability) of a PCS network. Our study indicates that at a small offered load, the network response time has a significant effect on the call incompletion probability. We also observe that the effect of the network response time is more significant if the mobile residence time distribution at a cell has a smaller variance.