A CPCH access method for prioritized services in W-CDMA

Common packet channel (CPCH) access is an efficient approach to support packet data transmissions in a wideband code-division multiple-access (W-CDMA) system. This letter introduces a simple access control method for CPCH, which results in higher throughput. This method also provides prioritized services for different traffic classes. Each traffic class is assigned a distinct transmit permission probability that is determined at the new call initiation stage based on the status of CPCH channel occupancy. The differentiated service qualities, which correspond to different transmit permission probabilities, are evaluated in terms of packet blocking rates. The overall system performance is also evaluated in terms of normalized throughput.     

Joint interference coordination approach in femtocell networks for QoS performance optimization

Future heterogeneous networks with dense cell deployment may cause high intercell interference. A number of interference coordination (IC) approaches have been proposed to reduce intercell interference. For dense small‐cell deployment with high intercell interference between cells, traditional forward link IC approaches intended to improve edge user throughput for best effort traffic (ie, file transfer protocol download), may not necessarily improve quality of service performance for delay‐sensitive traffic such as voice over long‐term evolution traffic. This study proposes a dynamic, centralized joint IC approach to improve forward link performance for delay‐sensitive traffic on densely deployed enterprise‐wide long‐term evolution femtocell networks. This approach uses a 2‐level scheme: central and femtocell. At the central level, the algorithm aims to maximize network utility (the utility‐based approach) and minimize network outage (the graphic‐based approach) by partitioning the network into clusters and conducting an exhaustive search for optimized resource allocation solutions among femtocells (femto access points) within each cluster. At the femtocell level, in contrast, the algorithm uses existing static approaches, such as conventional frequency reuse (ReUse3) or soft frequency reuse (SFR) to further improve user equipment quality of service performance. This combined approach uses utility‐ and graphic‐based SFR and ReUse3 (USFR/GSFR and UReUse3/GReUse3, respectively). The cell and edge user throughput of best effort traffic and the packet loss rate of voice over long‐term evolution traffic have been characterized and compared using both the proposed and traditional IC approaches.     

Dynamic Resource Allocation of Random Access for MTC Devices

In a long term evolution‐advanced (LTE‐A) system, the traffic overload of machine type communication devices is a challenge because too many devices attempt to access a base station (BS) simultaneously in a short period of time. We discuss the challenge of the gap between the theoretical maximum throughput and the actual throughput. A gap occurs when the BS cannot change the number of preambles for a random access channel (RACH) until multiple numbers of RACHs are completed. In addition, a preamble partition approach is proposed in this paper that uses two groups of preambles to reduce this gap. A performance evaluation shows that the proposed approach increases the average throughput. For 100,000 devices in a cell, the throughput is increased by 29.7% to 114.4% and 23.0% to 91.3% with uniform and Beta‐distributed arrivals of devices, respectively.     

Proportional fairness in MAC layer channel access of IEEE 802.11s EDCA based wireless mesh networks

Fairness provisioning in IEEE 802.11s EDCA based Wireless Mesh Networks (WMNs) is a very challenging task due to relayed traffic and traffic load variation among mesh routers. Because of bursty traffic in general purpose community wireless mesh networks, proportional fairness is more suited than max–min fairness, where mesh routers and clients should get channel access proportional to their traffic load. However, proportional fairness is hard to achieve by solving optimization function because of non-linearity and non-concave property of the objective function. In this paper, a probabilistic approach is proposed to provide proportional fairness without solving global non-linear and non-concave optimization. Every mesh node use a load estimation strategy to estimate total traffic load that it needs to forward. The required channel share of a mesh node should be proportional to its traffic load, whereas, the total normalized channel share for all the contending mesh nodes should be kept less than unity to satisfy the clique constraint. The network architecture and contention property in WMN are explored to deduce the required channel share of mesh nodes. A probabilistic approach is used to tune the contention window based on the difference between actual channel share and required channel share, so that the node with more traffic load gets more channel share. A discrete time Markov Chain based modeling is used to deduce the overall network throughput for the proposed scheme. Simulation result shows that the proposed scheme works better than the standard IEEE 802.11s based EDCA MAC in terms of fairness and throughput.     

Evaluating a cross-layer approach for routing in Wireless Mesh Networks

Routing in Wireless Mesh Networks is challenging due to the unreliable characteristics of the wireless medium. Traditional routing paradigms are not able to propose an efficient solution to this problem. Further, Gupta et al. demonstrated that the average throughput capacity per node of a wireless multi-hop network decreases as 1/n, where n is the number of nodes in the network. Recent studies have shown that a cross-layer approach is a promising solution to get closer to the theoretic throughput capacity bound. Cross-layer solutions have been already proposed either for specific TDMA/CDMA networks or for power-efficient routing protocols. These proposals are strongly MAC dependent, or suffer from targeting a steady state offering the best trade-off performance. In this paper, the problem we tackle in a more general context, disregarding the specific MAC and Physical layers technologies, can be formulated as follows: How to design a routing algorithm able to increase the average throughput capacity experienced by Wireless Mesh Networks? Starting from a theoretic result, we analyze the gain that a cross-layer approach can deliver, the metrics suitable to improve throughput capacity, and the power control policy that reduces interference. We take a MAC independent approach, focusing on the general characteristics of wireless links, targeting the improvement of throughput capacity in Wireless Mesh Networks. Our proposal performs path selection and power optimization based on three metrics, namely physical transmission rate, interference, and packet error rate. Performances are thoroughly analyzed and evaluated by extensive simulations, with both TCP and UDP traffic, and compared to other multi-hop routing protocols. For both kind of traffic, the simple heuristic we propose here allows to double the average throughput the network is able to route.     

On Throughput Guarantee of Aloha-Like Multi-Hop Wireless Networks

Providing Quality of Service (QoS) is one of significant issues for multimedia traffic. One approach to achieve the requested QoS is to characterize the traffic flows and guarantee their committed throughput. In a typical multi-hop wireless ad hoc network, determining the feasibility for a given set of flow characteristics is challenging due to the multi-user interference problem. To that end, this paper presents the following contributions. First, we describe a simple Aloha-like Medium Access Control (MAC) protocol that enables each flow to maintain its requested bandwidth, and thus is suitable for multimedia traffic. Second, we propose a bandwidth feasibility algorithm based on the Variable Elimination (VE) technique. The bandwidth feasibility algorithm determines whether or not a given network can support a set of flows of certain bit rates. Simulations indicate that our solution can precisely control the bit rates over all hosts while providing the throughput guarantees.     

An energy‐efficient clustering approach for collaborative data forwarding in heterogeneous MANET

Mobile ad hoc network consists of a group of mobile nodes that can communicate with each other without any infrastructure. Clustering of the mobile nodes ensures efficient use of available bandwidth and high network throughput. Various clustering schemes are developed to improve the energy efficiency and lifetime of the network. However, there is an increase in the energy consumption with the increase in the number of clusters for forwarding data. This paper presents an energy‐efficient clustering approach for collaborative data forwarding in mobile ad hoc network. The cluster head (CH) is selected based on the processing capability of the nodes and link connection metrics. The CH receives the data from the server and forwards the data to the member nodes at a corresponding data rate of the nodes. Data offloading technique manages the data traffic in the network. The CH rejoining approach enables load balancing in the network. The proposed clustering approach achieves a significant reduction in the energy consumption and data traffic and improvement in the throughput rate through stable routing.     

Adaptive Counting Rule for Cooperative Spectrum Sensing Under Correlated Environments

We propose in this paper a dual-antenna-array (with transmitter antenna array and receiver antenna array) architecture, where the antenna elements are divided into several antenna element sets and each traffic channel is transmitted over an antenna element set, to realize the multiple traffic channels set up by a user. A SINR feedback based algorithm, which can regulate the transmission rate by iteratively adjusting the power on each traffic channel, is proposed to execute the rate control for the proposed dual-antenna-array architecture under cochannel interference. It is shown that the proposed algorithm can make the throughput meet the throughput requirement or achieve the weighted bandwidth sharing for certain fairness. In addition, we further propose a traffic channel configuration algorithm to help the SINR feedback based algorithm find the optimal traffic channel configuration that can meet the throughput requirement for each traffic channel or results in the maximal total throughput for each user.     

Selfish Traffic with Rational Nodes in WLANs

We use a game-theoretic approach to investigate the problem of selfish traffic with rational nodes in WLANs and propose a game-theoretic EDCA (G-EDCA) to improve QoS. Simulation results show that G-EDCA performs much better than EDCA in terms of throughput, bandwidth, delay, and bitdrop- rate.     

A hybrid cycle bandwidth allocation scheme with differentiated services support in Ethernet passive optical networks

The Ethernet passive optical network (EPON) has emerged as one of the most promising solutions for next generation broadband access networks. Designing an efficient upstream bandwidth allocation scheme with differentiated services (DiffServ) support is a crucial issue for the successful deployment of EPON, carrying heterogeneous traffic with diverse quality of service (QoS) requirements. In this article, we propose a new hybrid cycle scheme (HCS) for bandwidth allocation with DiffServ support. In this scheme, the high-priority traffic is transmitted in fixed timeslots at fixed positions in a cycle while the medium- and low-priority traffic are transmitted in variable timeslots in an adaptive dynamic cycle. A suitable local buffer management scheme is also proposed to facilitate QoS implementation. We develop a novel feature providing potentially multiple transmission opportunities (M-opportunities) per-cycle for high-priority traffic. This feature is significant in improving delay and delay-variation performance. The HCS provides guaranteed services in a short-cycle scale for delay and jitter sensitive traffic while offering guaranteed throughput in a moderately long-time scale for bandwidth sensitive traffic and at the same time maximizing throughput for non-QoS demanding best-effort traffic. We develop analytical performance analysis on the deterministic delay bound for high-priority traffic and minimum throughput guarantees for both high- and medium-priority traffic. On the other hand, we also conduct detailed simulation experiments. The results show a close agreement between analytical approach and simulation. In addition, the simulation results show that the HCS scheme is able to provide excellent performance in terms of average delay, delay-variation, and throughput as compared with previous approaches.

Throughput study for admission control in IEEE 802.11 DCF with ARF

We propose an analytical approach to determining the admission of new stations to a WLAN operating in IEEE 802.11 Distributed Coordination Function (DCF) with Auto Rate Fallback (ARF). The proposed approach is based on a cross layer analytical model of how the throughput of existing stations in the WLAN is affected by admitting the new station in non-saturated as well as saturated traffic conditions. The effectiveness of the proposed approach is verified by simulations.     

Predictive QoS-based admission control for multiclass traffic incellular wireless networks

We develop the notion of quality of service (QoS) for multimedia traffic in terms of maximum call dropping probabilities independent of system load and a predefined call blocking probability profile for the different traffic classes for wireless networks of arbitrary shape and dimension. We describe two distributed predictive admission control algorithms, independent multiclass one-step prediction (IMOSP-CS and IMOSP-RES), which provide each traffic class with a given call dropping probability and a desired call blocking probability profile. Both algorithms may be seen as extensions of the multimedia one-step prediction (MMOSPRED) algorithm previously reported, which uses prediction of the overload probability in the home and neighbor cells in deciding whether to admit new users into a multiclass cellular system. The two algorithms differ in their approach to handoff call admission. The first algorithm completely shares the bandwidth among the entering handoff users while the second implements a partition-based reservation scheme. In this paper, we additionally impose a call blocking criterion that ensures a system-imposed call priority independent of the traffic in the system and which adapts to changes in the offered load. In comparing these algorithms to each other, we focus on system throughput and class independence. Both algorithms provide appropriate throughput under both homogeneous and heterogeneous traffic loading conditions while maintaining steady call dropping probabilities for each traffic class     

Distributed Switching for Data Transmission over Two-Way CATV

Most of tile present approaches to two-way interactive CATV focus on the centralized approach, in which all traffic must travel to the CATV head end. In this paper, we present a distributed approach, in which intelligent store-and-forward packet switches are to be installed at various locations on the cable. The analysis emphasizes three main criteria: the maximum traffic flow on the cable, the throughput of each switch, and the average message delay. Two possible schemes are compared. In one, the switches appear on the main trunk only. In the second, switches are used at branch locations as well.     

Performance analysis of voice/data cellular CDMA with SIR-based admission control

In this paper, we analyze the performance of a signal-to-interference ratio (SIR)-based admission control strategy on the uplink in cellular code-division multiple-access (CDMA) systems with voice and data traffic. Most studies in the current literature to estimate CDMA system capacity with both voice and data traffic do not take into account admission control based on SIR constraints. Here, we present an analytical approach to evaluate the outage probability for voice traffic, the average system throughput, and the mean delay for data traffic in a voice/data CDMA system, which employs an SIR-based admission control. We make two main approximations in the voice call outage analysis-one based on the central limit theorem (CLT) and the other based on the Fenton's method. We apply the Fenton's method approximation to compute the retransmission probability and the mean delay for data traffic, and the average system throughput. We show that for a voice-only system, a capacity improvement of about 30% is achieved with the SIR-based admission control as compared with the code availability-based admission control. For a mixed voice/data system with 10 Erlangs of voice traffic, an improvement of about 40% in the mean delay for data is shown to be achieved. Also, for a mean delay of 50 ms with 10 Erlangs of voice traffic, the data Erlang capacity improves by about 50%.     

带输入缓冲的ATM交换机的吞吐量分析

在ＦＣＦＳ（先来先服务）准则下,ＡＴＭ（异步传递模式）交换机的吞吐量为０．５９。文章提出了三种提高ＡＴＭ交换机的吞吐量的方案：方案Ａ（输入扩展方案）、方案Ｂ（窗口选择方案）和方案Ｃ（信元舍充方案）。笔者认为,对于方案Ｃ,所有信元都属于一个猝发的相关业务,被分配到同一个输出端口,而且每一个业务源都是ＩＢＰ（中断贝努利业务进程）模型,方案Ｃ的结果表明：目标的相关性不影响吞吐量,当所有的输入业务平衡时,     

Worst-case fraction of CBR teletraffic unpunctual due tostatistical multiplexing

This paper quantitatively analyzes the queueing delay of the constant-bit-rate (CBR) traffic in a multiplexer, where the CBR traffic is mixed with the traffic of another session (interfering traffic) that has throughput and burstiness constraints. This paper focuses as a quality-of-service (QoS) measure on the fraction of the CBR traffic that fails to meet a certain delay requirement. Results include the worst-case QoS of CBR traffic as a function of the throughput and burstiness parameters imposed on the interfering traffic. Results of this paper can be applied to traffic management and call processing of asynchronous transfer mode (ATM) networks     

On throughput capacity of large-scale ad hoc networks with realistic buffer constraint

The problem of determining the throughput capacity of an ad hoc network is addressed. Previous studies mainly focused on the infinite buffer scenario, however, in this paper we consider a large-scale ad hoc network with a scalable traffic model, where each node has a buffer of size B packets, and explore its corresponding per node throughput performance. We first model each node as a G/G/1/B queuing system which incorporates the important wireless interference and medium access contention. With the help of this queuing model, we then explore the properties of the throughput upper bound for all scheduling schemes. Based on these properties, we further develop an analytical approach to derive the expressions of per node throughput capacity for the concerned buffer-limited ad hoc network. The results show that the cumulative effect of packet loss due to the per hop buffer overflowing will degrade the throughput performance, and the degradation is inversely proportional to the buffer size. Finally, we provide the specific scheduling schemes which enable the per node throughput to approach its upper bound, under both symmetrical and unsymmetrical network topologies.     

Dynamic Virtual Topology Reconfiguration Algorithms for Groomed WDM Networks

In a Wavelength Division Multiplexing (WDM) optical network, in which the traffic changes dynamically, the virtual topology designed for an old traffic set needs to be reconfigured for a new demand set in order to route more connections. Though reconfiguration increases the throughput, the resulting disruption in traffic is a cause for concern. We present a simple and flexible framework to evaluate the gain achieved by reconfiguration, based on the two conflicting objectives of increasing throughput and reducing disruption. We present adaptive reconfiguration algorithms which determine the change in the virtual topology with a corresponding change in the demand set. These algorithms incrementally add lightpaths to a given virtual topology and delete a minimum number of lightpaths to facilitate their addition. One of the algorithms improves throughput by making changes to the existing virtual topology and another one reduces disruption by making changes to the virtual topology suited for the new demand set. However, in order to reduce the gap in bandwidths between what a wavelength channel can provide and what an individual connection requires, several low-speed connections need to be groomed onto a single wavelength. As our algorithms aim at increasing the throughput with as few lightpath changes as possible, more connections will be accepted without considerable increase in number of lightpaths. This means, more connections are groomed onto the lightpaths. One nice feature of our approach is that it fits not only for groomed networks where traffic demands are at the sub wavelength level, but also for networks where connection demands are at the wavelength level. The extensive simulation studies, wherein we compared the performance of our algorithms with that of two other possible schemes, demonstrated their flexibility and robustness. This work was supported by the Department of Science and Technology, New Delhi, India.     

Versatile Analytical Model for Delay and Energy Evaluation in WPANs: A Case Study for IEEE 802.15.4 CSMA-CA

This paper proposes a versatile analytical model to predict the medium access control (MAC) layer performance metrics (throughput, average MAC service time, successful transmission probability) as well as the energy consumption of wireless personal area networks (WPANs) under all possible transmission modes (unacknowledged, limited and unlimited acknowledged modes) with both saturated and unsaturated traffic patterns. This rigorous analytical approach produces straightforward equations that are used to predict the operational parameters required to optimise the throughput of networks. This paper uses the state-of-the-art IEEE 802.15.4 CSMA-CA protocol to demonstrate the use of the modelling approach. The numerical results obtained from the analytical model are verified through comparison with simulation.     

Packet triplet: a novel approach to estimate path capacity

Packet Pair is an end-to-end approach to estimate the capacity of an Internet path. Many studies have shown that such estimation exhibits a lot of bias due to the dynamic cross traffic. In this paper, we propose a novel approach, called Packet Triplet, which uses three back-to-back probing packets - different from two back-to-back probing packets in Packet Pair - to estimate the capacity of a network path. A new filtering technique is also introduced into Packet Triplet to further refine the path capacity estimation approach. The experiments demonstrate that such probing approach is effective under different cross traffic.