Delay and loss control of an output buffered fast packet switch supporting integrated services

The performance of an ATM switch of a space division architecture with finite FIFO output buffer is considered. The input traffic is modeled by identical Bernoulli processes. The presented analytical approach is based on a queueing model which describes the finite queue occupancy distribution. The evaluation of the cell loss and cell mean delay is compared with previously presented analytical results. It is found that the presented simple model is suitable for determining the finite buffer effect on the ATM network performance in spite of its simplicity and its analytical tractability. An asymptotic relation is obtained between the offered load and the buffer size that gives a constant cell loss behavior. Moreover, the outstanding physical meaning of the presented procedure gives a deep insight into the ATM switch performance parameters as to the network offered load and the switch buffer capacity.

WiMAX is one of the broadband wireless access technologies, which provides the efficient QoS to the large number of users. The multimedia applications such as real time and non-real time services are gaining importance in the WiMAX network. To support such applications, there is a need to propose an efficient QoS traffic prediction routing protocol for the WiMAX networks. To address this, the authors are using Gene Expression Programming technique. They have generated datasets for CBR based traffic and file transfer applications. Here, they focus to develop the mathematical expressions for throughput of the network in terms of bandwidth, average end-to-end delay and average jitter for CBR based traffic and file transfer applications, so that they can analyze and predict the QoS traffic of the network. The simulation results show that the model values and the target values match with better approximation. Further, sensitivity analysis has been carried out for both CBR based traffic and file transfer applications.

IEEE 802.16 standard supports real time and non-real time services at each node. However, it has flexibility to develop customized scheduling algorithms according to different priority-based traffic's quality of service (QoS) requirements. Hence, it is imperative to obtain optimum scheduling schemes for different kinds of traffic (i.e., services). Earliest due date (EDD) is one of the highly referred scheduling algorithms for real time communication. In this presentation, our study shows that the proposed hybrid algorithms (EDD along with weighted fair queue (WFQ)) in a node gives better performance for real time services instead of EDD only. Moreover, the results reveal that, scheduling schemes from base station (BS) to subscriber station (SS) like grant per SS (GPSS) impacts less delay than grant per connection (GPC)

In this paper, we purpose a novel approach to analyze exact cell loss probability of Shared Buffer ATM switch. In a N X N ATM switch whose input ports and output ports share one buffer, the number of arriving cells from input ports at one time slot is less than or equal to N. If these cells were destined to n output ports, no cells will be destined to the remaining N-n output ports. In the extremism, all arriving cells were destined to one output port, no cell will be destined to the other N-1 output ports. So, the arriving cells at each time slot from the input ports are destined to the output ports correlatively, but not independently. For this reason, the analyzing result on the assumption that all output cell queues are independent one another is larger than actual result. We complete our analysis by three steps. First, considering the case that there are cells arriving from input ports but not cells remove from output ports, we can get one-step state transition probability matrix P<SUB>a</SUB>; Second, considering the case that there are cells removing from output ports but not cells arrive from input ports, we can get one-step state transition probability matrix Ps; Third, considering arrival process and service process are independent, the accurate one-step state transition probability matrix P of cell's number in the buffer is derived, and then cell queue length steady probability distribution can be found. We can compute the accurate buffer capacity below certain cell loss probability. Computer simulation proves that the approach is efficient and exact.

Quality of Service (QoS) and queue management are important issues for IEEE 802.11 systems. However, existing 2-dimensional (2-D) Markov chain models of 802.11 systems are unable to capture the complete QoS performance and queueing behavior due to the lack of an adequate finite buffer model. We present a 3-dimensional (3-D) Markov chain that integrates the 802.11 system contention resolution and queueing processes into one model. The 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> dimension, that models the queue length, allows us to accurately capture important QoS measures, delay and loss, plus throughput and queue length, for realistic 802.11 systems with finite buffer under finite load. We derive an efficient method for solving the steady state probabilities of the Markov chain. Our 3-D Markov chain is the first finite buffer model defined and solved for 802.11 systems. The solutions, validated by extensive simulations, capture the system dynamics over a wide range of traffic load, buffer capacity, and network size. Our 3-D model points to the existence of an effective maximum throughput and shows its relationship with buffer capacity. We demonstrate that our 3-D model can also be used in resource allocation to determine adequate buffer sizes under a particular QoS constraint.

In this work, Call Admission Control Schemes which is one of the efficient resource management techniques are analyzed and proposed a new call admission scheme by using the structure of data allowing available bandwidth allocation over Complete-Partitioning Sharing technique. Voice calls are real-time services and needs fixed bandwidth, on the other hand, data calls are non-real time services and adaptable to work in available bandwidth without a concession made for Quest. It is obtained state-dependent service rates by means of this structure of data and modeled two-dimensional(2-D) Markov Chain to be able to measure performance of the proposed scheme and calculated mathematically performance measurements that is voice/data blocking/dropping probabilities for each state over this model Numerical results show that proposed scheme guaranteed the targeted QoS parameters levels in resource utilization.

In broadband networks with guaranteed Quality of Service (QoS), dimensioning becomes an even harder task than in traditional data or circuit networks. The network operator has two resources to manage — the trunk capacity and the switch memory (buffers) — and multiple QoS constraints to respect — call blocking, cell loss ratio and cell delays. We investigate how this new context can affect the design, cost and dimensioning of networks. In particular, we study how much can be gained if we do not restrict ourselves to the two limit cases of a bufferless or an infinite buffer system. We deal first with the single-service case for a single link. We then investigate the multi-service case on a single link. We study the cost of integration when service classes have very different delay constraints. The main results obtained are that finite buffers can have a very significant effect on the optimal cost whenever buffer costs are high, as in satellite systems, especially when a delay constraint is imposed on the problem and that services integration can be very costly when different delay requirements are involved.

The demand for real-time e-commerce data services has been increasing recently. In many e-commerce applications, it is essential to process user requests within their deadlines, i.e., before the market status changes, using fresh data reflecting the current market status. However, current data services are poor at processing user requests in a timely manner using fresh data. To address this problem, we present a differentiated real-time data service framework for e-commerce applications. User requests are classified into several service classes according to their importance, and they receive differentiated real-time performance guarantees in terms of deadline miss ratio. At the same time, a certain data freshness is guaranteed for all transactions that commit within their deadlines. A feedback-based approach is applied to differentiate the deadline miss ratio among service classes. Admission control and adaptable update schemes are applied to manage potential overload. A simulation study, which reflects the e-commerce data semantics, shows that our approach can achieve a significant performance improvement compared to baseline approaches. Our approach can support the specified per-class deadline miss ratios maintaining the required data freshness even in the presence of unpredictable workloads and data access patterns, whereas baseline approaches fail.

In this paper, we propose and analyze two different handoff schemes in integrated wireless mobile networks. The channels in each cell are divided into two parts and pre-allocated for real-time and nonreal-time services. To increase the channel utilization while keeping the quality of service (QoS) of each type for traffic, one type of service is allowed to borrow channels from the other under certain constraints. Depending on whether or not nonreal-time service calls can be interrupted, we have two channel borrowing schemes: nonpreemptive and preemptive. We use a system model defined by a multidimensional Markov chain and compute the performance in terms of blocking probability of originating calls, forced termination probability of real-time service calls, and average transmission delay of nonreal-time service calls. The simulation results are observed to match closely with the analytical model. The preemptive borrowing scheme is observed to perform better than the nonpreemptive scheme at the cost of increased handoff for nonreal-time service calls. The impact of the long-term dependence of data traffic on system performance is also discussed.

This paper presents properties of a mobile ad hoc network (MANET) with dynamic spectrum management (DSM) and is devoted to the concept and implementation of the new traffic engine that is used in a High-Fidelity simulator of MANET with cognitive nodes for special applications. The communication traffic generated by each node is defined according to its role in the hierarchical structure of the operational scenario, determining its priorities, permission to use particular real time and non-real time services. The service usage is a source based model, defined in the user’s profile containing its statistical properties, describing periodicity, duration and randomness of traffic generation. The overall traffic generated by the node is a combination of traffics related to specific services. Their statistical parameters are based on real exercises results. The model was defined in the Matlab environment and next verified using the MAENA simulator for complex, operational scenarios. The achieved results show that use of both central and distributed DSM provides a better performance of the MANET network with complex traffic.

As an effectual simple wireless equivalent created in the telecommunications (telephone) industry, Wireless Asynchronous Transfer Mode (WATM) is utilized to stream unified traffics like video, data, and voice data. In the asynchronous data transfer mode, voice data transfer a packet with the same medium, and data share the networks and burst data. Effective WATM data transmission requires an extensive array of designs, techniques used for control, and simulation methodologies. The congestion of the network is among the key challenges that lower the entire WATM performance during this procedure, in addition to the delay in cell and the overload of traffic. The congestions cause cell loss, and it requires expensive switches compared to the LAN. Consequently, in this current study, the application of an effectual switching model together with a control mechanism that possesses multiple accesses is employed. The multiple access process and switching model are utilized to establish an effective data sharing process with minimum complexity. The switching model uses the synchronous inputs and output ports with buffering to ensure the data sharing process. The traffic in the network is decreased, and the loss of packets in the cells is efficiently kept to a minimum by the proposed technique. The system being discussed is employed through the utilization of software employed using OPNET 10.5 simulation, with the valuation of the WATM along with the investigational outcomes accordingly. The system's efficiency is assessed by throughput, latency, cell loss probability value (CLP), overhead network, and packet loss. Thus, the system ensures the minimum packet loss (0.1 %) and high data transmission rate (96.6 %)

Intuition suggests that a finite buffer limits the effect of traffic auto-correlations on the queue length. We investigate the extent to which finite buffers can, therefore, be expected to mitigate the effects of long-range dependence (LRD). With traffic sequences generated by the fractional autoregressive integrated moving average (f-ARIMA) models for LRD, and by AR models for short range dependence (SRD), we investigate the traffic performance for a range of finite buffers, both for single and multiplexed streams. For design, the aim is to 'match' a given LRD auto-correlation function with a suitable SRD function whose performance provides, for a wide range of traffic intensities and buffer sizes, a conservative bound on the performance associated with the LRD function. The results suggest that by suitably 'dominating' an LRD auto-correlation function by an SRD function, one can obtain conservative performance bounds for a realistic range of traffic intensities and buffer sizes (delays). Also, in several cases, a 'cross-over' phenomenon is observed for cell-loss probabilities as the buffer size increases, i.e., the loss probabilities are smaller for LRD than for SRD for small buffers, with the converse true for large buffers. This suggests that finite buffers, can in some cases, counteract the effects of LRD in traffic arrivals, and thus enable conservative designs to be based on Markovian traffic models.

Wireless all-IP multimedia communications systems promise a wide range of services with different quality of service (QoS) requirements and diverse ranges of supported bit rates. This implies that the nature of input traffic load at the base station is expected to vary significantly in time. When radio channels are shared by the existing mixed services (say for example real-time and non-real time services), packet scheduler and channel assignment faces a number of parallel input data pipes which are varied in terms of bit rate. The weights, assigned to different involved aspects in the packet scheduling process, outlines the strategy in terms of importance given to different aspects of packet scheduling. Schedulers with fixed weighting parameters are unable to cope with variable traffic load and radio channel conditions efficiently. The weights assigned to specific traffic or radio channel conditions, might not be suitable for others. In this paper, we propose an optimization and automation algorithm for selection and adaptation of packet scheduling weights. It is shown that the proposed algorithm is capable of improving different aspects involved in a successful QoS provisioning, such as fairness, stability, delivered delay, bit rate and throughput, simultaneously.

The automobile industries are undergoing a technological revolution, which has facilitated the emergence of multiple Vehicle-to-Everything (V2X) applications with diverse Quality of Service (QoS) requirements. The conventional resource allocation methods are no longer applicable in V2X due to the diverse vehicular services with different QoS requirements in various practical scenarios. Therefore, this paper proposes a multi-service resource allocation strategy for V2X. Specifically, the problem of allocating resources for multiple V2X services is decoupled into two sub-problems, i.e., resource allocation between slices, and resource scheduling within slice. Then, a heuristic resource allocation algorithm is adopted to solve the resource allocation between slices sub-problem. For Real-Time (RT) and Non-Real Time (NRT) services in the vehicular network, specialized scheduling has been designed for the near-real-time Radio Access Network (RAN) Intelligent Controller and non-real-time RAN Intelligent Controller in the Open Radio Access Network (O-RAN) architecture, to meet the heterogeneous QoS service requirements of vehicles. Simulation results demonstrate that compared to the modified largest weighted delay first (M-LWDF) algorithm, the proposed resource allocation strategy can enhance the AoI of the proportional fairness (PF) services by 15%, and provide 7.39% transmission rate gain for NRT services.

Two analytical models for evaluating performance of Gigabit Ethernet hosts with finite buffer