To meet the requirements on data collection from wireless sensor network for healthcare application especially in hospital, the performance of wireless communication is an important issue. In particular, simultaneous transmissions from numerous sensors will cause serious collision which leads to transmission packets loss and delay. In this paper, a management scheme, multi-criteria decision making method using TOPSIS, for IEEE 802.15.4 is proposed for wireless sensor network. The performance of the network is determined by beacon order, superframe order, contention window, number of backoffs and backoff exponent. By analyzing slotted CSMA-CA mechanism, which is in the beacon-enabled mode, through OPNET, the proposed scheme can estimate the best combination of the parameters. The results show that the proposed scheme achieves the best combination of low end-to-end delay, high throughput and high successful probability.

In this paper, we consider an integrated service system, providing multirate guaranteed services and homogeneous best-effort services. The total system capacity is shared by both service types, while the guaranteed service customers are treated as high priority and are allocated fixed data rate bandwidth units. The best-effort service customers are supported by the remaining capacity leftover by the guaranteed services, in a processor-sharing manner. Admission control on the best-effort service customers is adopted to provide a certain level of quality of service (not guaranteed) to avoid the effect of repeated attempts. The best-effort customer blocking probability is an important metric for network dimensioning. In this integrated service system, we observe that the blocking probability of the best-effort customers is not insensitive to the shapes of their flow-size distributions and the guaranteed customers' holding-time distributions. We obtain here by light computation, for the best-effort customers, blocking probability bounds, and approximations, which possess the insensitivity property. Considering that the distributions for customers' holding times and flow sizes may be unknown, the proposed insensitive bounds and approximations will facilitate system design and network dimensioning with predictable and acceptable performance.

For integrated service systems supporting real-time (RT) and non-real-time (NRT) traffic, evaluating the performance of the NRT traffic is often challenging. An approximation based on a fluid model - the so-called Fluid Approximation (FA) - can be used when RT traffic has much larger successful call arrival rate than the NRT traffic, while otherwise it may introduce errors. In this paper, we propose a Generalized Fluid Approximation (GFA), extending the use and improving the accuracy of FA. It can also be used to trade off the computational complexity and the accuracy. Benefits achieved by GFA are demonstrated by extensive numerical examples.

This paper considers a two-tier femto-macro overlay network architecture, where groups of femtocells are overlaid by macrocells. The capacity of the femtocells is limited, thus redirection of blocked femto calls to the overlaid macrocell is used as a QoS assurance strategy. Similar overflow approaches have been used in telephony; however, extension of this approach to capacity-constrained femto-macro overlay networks poses significant challenges due to the wide variety of bandwidth requirement of Internet services, the large number of femtocells overlaid by a macrocell, and the need for fast computations imposed by practical requirements of dynamic real-time resource allocation. We propose a new computationally efficient numerical method for the loss probability approximation in such two-tier femto-macro overlay networks. The accuracy of the method is verified by exact Markov-chain solutions for small systems and by simulations for larger systems.

Performance modeling is important for the purpose of developing efficient dimensioning tools for large complicated networks. But it is difficult to achieve in heterogeneous wireless networks, where different networks have different statistical characteristics in service and traffic models. Multiservice loss analysis based on multi-dimensional Markov chain becomes intractable in these networks due to intensive computations required. This paper focuses on performance modeling for heterogeneous wireless networks based on a hierarchical overlay infrastructure. A method based on decomposition of the correlated traffic is used to achieve an approximate performance modeling for multiservice in hierarchical heterogeneous wireless networks with overflow traffic. The accuracy of the approximate performance obtained by our proposed modeling is verified by simulations.

By employing Bayesian neural network, a new QoS prediction algorithm for high speed packet access network has been developed. Network performances are evaluated based on a well developed call admission control scheme, namely the tri-threshold bandwidth reservation scheme. The algorithm helps to improve the resource management, thus saving the cost and bandwidth.

A total QoS solution including dynamic call admission control scheme and bandwidth allocation algorithm is proposed for IEEE 802.16e mobile WiMAX. In this paper, the relationship between the channel utilization, the dropping and blocking probability versus traffic loads are investigated. The proposed WiMAX scheme supports voice, data and multimedia services with differentiated QoS.

This paper studies loss calculation in hierarchical networks with multiservice overflows which have different call arrival rates, mean holding times, bandwidth requirements and share a common link. The loss calculation involves two challenging problems: 1) the computation of the two moment characterizations of multiservice overflow traffic over the shared link, 2) the calculation of the loss probabilities for multiservice non-Poisson overflow traffic in hierarchical systems. An efficient approximation method, known as multiservice overflow approximation (MOA), is proposed to enable multiservice networks designs with hierarchical architecture. Two contributions are included in the MOA method. First, an approximation based on blocking probabilities matching is proposed to compute the variances of multiservice overflows over the shared link. Second, a modified Fredericks & Hayward's approximation is used to calculate the loss probabilities of multiservice non-Poisson over flow traffic. The performance of the MOA method is evaluated in a two-tier hierarchical cellular network and compared with an existing approximation method based on multi-dimensional Markov-modulated Poisson process (MMPP). Verified by simulations, the MOA method achieves better accuracy in the general heterogeneous cases at lower computational cost than the MMPP method.

The recent investigations on interleave-division multiple-access (IDMA) have demonstrated its advantage in supporting high-data-rate and multi-rate services over wireless fading channels. This paper focuses on quality of service (QoS) guarantee in IDMA-based multi-service wireless networks. We propose a QoS architecture which addresses the key issues of QoS guarantee for multi-service in IDMA, including medium access control (MAC), admission control, power control, and rate allocation. The proposed IDMA QoS architecture avoids complex packet scheduling at the MAC layer which is however required in other existing multiple access systems. Data packets can be transmitted in IDMA without scheduling delay. Additionally, to improve the efficiency of random access, an interleave- division slotted-ALOHA (IDSA) access method is proposed for the IDMA MAC protocol. We derive the relationship between the arrival rate of access requests and the number of access interleavers allocated to an IDMA system for a given access success probability. Based on this relationship, we can adaptively adjust the number of access interleavers according to the traffic load of access requests, so as to ensure a satisfactory probability of successful access as well as low complexity of request detection at the receiver.

Multipath routing is a key technique to support video transmission over wireless ad hoc networks (WANETs). In WANETs, the lifetime of a node is related to its residual energy, current traffic conditions and the required energy consumed for sending a packet to its next hop in the path. In this paper, we propose a new adaptive routing scheme termed lifetime-aware multipath optimal routing (LAMOR) for supporting high-speed real time video transmission in WANETs, which is optimized in terms of lifetime and analyze its characteristics. Both theoretical analysis and simulation results demonstrate that LAMOR indeed extends network lifetime and improves the transmission quality of video streams

From the control theory point of view, it is reasonable to regard the TCP congestion control mechanism as a feedback control system. The TCP congestion control is complemented by the active queue management (AQM) scheme implemented in the routers, which could improve the effectiveness. Recently, an effective proportional-differential (PD) control algorithm has been proposed as a new AQM scheme for TCP congestion control. But it is still difficult to assign the parameter values of the PD-controller. This paper proposes a method for the design of an effective and stable PD-control AQM for routers in the Internet. For this purpose, a first-order plus time-delay TCP model is constructed, and a relay feedback method is employed to determine a set of stable parameter values of the model. From this set of values, and the requirements of the gain and phase margin, the specified parameter values of the PD-controller can be easily obtained by scanning the stable parameter set.

Using a simple model of saturated, synchronized and homogeneous sources of TCP Reno with drop-tail queue management and a discrete-time framework, we derive formulae for stationary as well as transient queueing behavior that shed light on the relationship between large buffers and work conservation (queue never empties). Using simulations, the relevance of the results for the case of non-synchronized sources is demonstrated. In particular, we demonstrate that a certain simple lower bound for the stationary queue length applies also to the case where the sources are non-stationary.

This paper describes a proportional-differential (PD) control algorithm as a new active queue management (AQM) scheme for TCP/IP congestion control. From the viewpoint of the control theory, TCP congestion control system can be regarded as a feedback regulating system. In this paper, a robust AQM called PD-controller is proposed. The design principles of PD-controller are presented in details. Its performance is extensively evaluated by simulations. The results demonstrate that the PD-controller AQM is stable and robust against traffic load fluctuations, UDP and HTTP disturbances. Its superiority over other AQMs is also demonstrated.

Resource-demanding services such as multimedia-on-demand (MOD) become possible as broadband Internet is getting more popular. However, as the size of multimedia files grows rapidly, storage of such large files becomes a problem. Since multimedia contents will generally become less popular with time, it is desirable to design a prediction algorithm so that the multimedia content can be unloaded from the server when it becomes unpopular. In this paper, we have two objectives: 1) analyse the MOD viewing trend in order to understand the viewing behaviour of users; 2) predict the viewing trend based on the knowledge obtained from the trend analysis. For trend analysis, we study three traditional regression models, including linear regression, exponential regression, and power regression, and propose two additive regression models, exponential-exponential-sum (EES) and exponential-power-sum (EPS), to improve the goodness of fit. Then, the most fitted models are used in trend prediction. Four prediction approaches, fixed regression selecting (FRS), continuous regression updating (CRU), historical updating (HU), and continuous regression with historical updating (CRHU) are proposed. From the numerical results, we find that CRHU, which is constructed by considering historical trends and new incoming viewing request data, is in general the best method in forecasting MOD trend.

As broadband networks keep increasing in transmission speed, multimedia-on-demand (MOD) is expected to be one of the most popular broadband services in the near future. MOD systems can provide two types of services: interactive service and batch service. The interactive service provides each user with one dedicated stream. With it, the user can use the VCR function controls such as pause, forward and rewind. However, the service is expensive and not scalable to the system size. With the batch service, the users who request the same multimedia content within a batch period will be grouped together and served by one dedicated stream. Hence, the system can either use fewer resources or serve more customers. However, batch users must wait for programs to begin and are unable to perform VCR function control. We take advantage of both services by considering an MOD system that provides both services. Also, we propose two methods to optimize their coexistence. In addition, an analytical model is derived for performance evaluation. Numerical results show that the proposed hybrid system really outperforms both individual systems. The hybrid system provides a superior solution to both the service providers and the users. Specifically, given a limited storage resource, the service provider receives more revenue by serving more users concurrently, while the users have a satisfactory viewing experience due to higher availability of programs and the low average waiting time.

Fair packet discarding (FPD) is a mechanism which provides incentives to users for participation in congestion control, such that ATM networks can operate in a more efficient manner. In this paper, we propose a simple congestion control framework consisting of FPD and ATM Forum's explicit-rate flow control scheme. By simulations, we show that this framework enables the packet-level throughput of each connection converging to the max-min fair apportionment in a distributed manner. With the built-in policing capability of FPD, this framework also eliminates the need of usage parameter control for ABR service.

The asynchronous transfer mode (ATM) Forum has chosen rate-based control as the flow control scheme for the available bit-rate (ABR) service. However, rate-based schemes can achieve congestion control only if all users act in a cooperative manner. Even a limited number of uncooperative users can cause congestion collapse. We propose a mechanism called fair packet discarding to provide incentives to users to participate in network congestion control so that the network can operate in a more efficient manner.

An analysis of the exact delay of a TDMA or a loop communication system with a contiguous output and a Poisson message arrival process is presented. The nonlinear relationship of a contiguous output with arbitrary arrival process can be expressed by an infinite series. In the case of a Poisson message arrival process, the series can be summed to a closed form. The derived result, which is validated by simulation, is a vast improvement over the previously used approximate model of multiple frames with single output.

This paper identifies the characteristics of a point-topoint demand-assignment satellite-switched spot-beam antenna communication network for integrated data voice traffic. The described protocol is known as space-division multiple-access (SDMA) which uses an on-board central traffic controller, a fixed-assignment timedivision multiple-access (TDMA) protocol for reservations, and a rigid frame structure with separate data and voice subframes. Message and circuit switching are utilized for data and voice traffic, respectively. Synchronization is maintained by a looped-back reservation burst. A detailed delay analysis of data and voice traffic is presented for an arbitrary compound arrival process. A new method for the calculation of the data reservation and scheduling delays is derived. A comparison of the performance of the SDMA protocol to other protocols is shown. This paper demonstrates the feasibility and illustrates the design of the SDMA protocol.