Liansheng Tan

Stability of TCP/RED systems in AQM routers

By applying the time-delay control theory to a TCP/RED dynamic model, this note establishes some explicit conditions under which the TCP/RED system is stable in terms of the average queue length. Then, the stability region is discussed. Finally, the results are illustrated by using ns2 simulations, which demonstrates that it is able to choose an appropriate control parameter maxp of RED based on the stability conditions derived in this note, to achieve satisfactory network performance. It is found, by comparison, that this improved performance is better than that of three other typical active queue management (AQM) schemes-the random exponential marking (REM), proportional-integral (PI) controller, and adaptive virtual queue (AVQ) schemes

Data prediction, compression, and recovery in clustered wireless sensor networks for environmental monitoring applications

Environmental monitoring is one of the most important applications of wireless sensor networks (WSNs), which usually requires a lifetime of several months, or even years. However, the inherent restriction of energy carried within the battery of sensor nodes brings an extreme difficulty to obtain a satisfactory network lifetime, which becomes a bottleneck in scale of such applications in WSNs. In this paper, we propose a novel framework with dedicated combination of data prediction, compression, and recovery to simultaneously achieve accuracy and efficiency of the data processing in clustered WSNs. The main aim of the framework is to reduce the communication cost while guaranteeing the data processing and data prediction accuracy. In this framework, data prediction is achieved by implementing the Least Mean Square (LMS) dual prediction algorithm with optimal step size by minimizing the mean-square derivation (MSD), in a way that the cluster heads (CHs) can obtain a good approximation of the real data from the sensor nodes. On this basis, a centralized Principal Component Analysis (PCA) technique is utilized to perform the compression and recovery for the predicted data on the CHs and the sink, separately in order to save the communication cost and to eliminate the spatial redundancy of the sensed data about environment. All errors generated in these processes are finally evaluated theoretically, which come out to be controllable. Based on the theoretical analysis, we design a number of algorithms for implementation. Simulation results by using the real world data demonstrate that our framework provides a cost-effective solution to such as environmental monitoring applications in cluster based WSNs.

Time delay and data loss compensation for Internet-based process control systems:

Introducing the Internet into process control systems has brought a lot of benefits and some difficulties to control engineers as well. The major challenge of Internet-based process control systems is how to deal with Internet time delay and data loss. This paper analyses Internet communication features and proposes a control structure with a variable sampling time to overcome the Internet transmission delay. In order to take advantage of the structure fully and attack the major difficulties, two compensation elements have been designed and implemented in the system. These two compensators are located in the feedback and feedforward channels in the architecture respectively. Our simulation and experimental results illustrate that the control structure and two compensation elements can efficiently deal with the Internet time delay and data loss. Our simulation results also show that the time delay and data loss in the feedforward channel seem to cause more serious influence on the control performance and is more difficult to be compensated for.

FAST TCP: fairness and queuing issues

This letter considers problems of unfairness and excessive variations of the router queue associated with FAST TCP operations due to inaccurate estimation of the round-trip propagation delay. Using a simple example, we explain unfairness in FAST TCP caused by this inaccurate estimation. We also present analytical and simulation performance studies and show that improving this estimation by giving the first packet in every flow priority can improve fairness and reduce queuing variations.

Price-based max-min fair rate allocation in wireless multi-hop networks

When allocating rates in wireless multi-hop networks, one difficulty comes from the so-called MAC (media access control) constraint. To overcome this difficulty, this paper proposes a price-based max-min fair rate allocation scheme. Unlike existing schemes, our scheme is based on the MaxNet principle using the maximum price of all nodes along a transmission path to control the flows rate. Through theoretical analyses and simulation results, we show that the algorithm is able to meet the MAC constraint and to achieve max-min fairness among multi-hop flows in wireless networks even if the topology varies, as is the case in a mobile environment.

On Parameter Tuning for FAST TCP

This paper studies the stability of FAST TCP using a continuous time model of a single-link single-source network. A sufficient condition on asymptotical stability of FAST TCP congestion window is obtained, which relates all the relevant parameters in FAST TCP and decouples the key parameter a from others. A guideline on FAST TCP parameter setting is thus provided. The ns2 simulations validate the theoretical results

A Balanced Parallel Clustering Protocol for Wireless Sensor Networks Using K-Means Techniques

For wireless sensor networks (WSNs), it is a challenging task how to schedule the energy resource to extend the network lifetime due to the fact that WSNs are usually powered by limited and non-rechargeable battery. A clustering scheme is helpful in reducing the energy consumption by aggregating data at intermediate sensor nodes. In this paper, we propose a balanced parallel k-means based clustering protocol; we term it BPK-means protocol. In this new protocol, we use k-means algorithm to cluster the sensor nodes, the cluster-heads are then selected in terms of two factors, they are a) the distance from node to cluster-center, and b) the residual energy. BPK-means only requires local communications: each tentative cluster-head only communicates with their topologically neighboring nodes and other tentative cluster-heads when achieving a distributed clustering scheme. The algorithm thus has the attractive feature of parallel computations. Moreover, BPK-means further balances the clusters to improve intra-cluster communication consumptions. We present the algorithm of this new protocol, analyze its computing properties, and validate the algorithm by simulations. Both theoretical analyses and simulation results demonstrate that BPK-means can achieve better load-balance and less energy consumptions when compared with LEACH. In addition, the BPK-means protocol is able to distribute energy dissipation evenly among the sensor nodes, which then prolong the system lifetime for the networks significantly.

Rate-based congestion control in ATM switching networks using a recursive digital filter

Abstract The present paper proposes a control-theoretic approach to design rate-based controllers in order to flow-regulate the best-effort service in asynchronous transfer mode (ATM) switching networks. The proposed control uses a recursive digital filtering controller, where the control parameters can be designed to ensure the stability of the control loop in a control-theoretic sense. The stability of closed-loop congestion-controlled systems is analyzed by using Schur–Cohn stability criterion, which leads to certain necessary and sufficient stability condition under which the controlled ATM switching network is asymptotically stable in terms of buffer occupancy. Such proposed stability condition is then shown to be a key tool in designing a wide scope of adaptive controllers. Further, we demonstrate that a fair share of the available bandwidth at the bottleneck node can be achieved according to the proposed control policy. Simulations are performed that show good performance of both local area networks and wide area networks if implemented by the proposed control schemes.

To be fair or efficient or a bit of both

Introducing a new concept of (@a,@b)-fairness, which allows for a bounded fairness compromise, so that a source is allocated a rate neither less than 0= =1, times its fair share, this paper provides a framework to optimize efficiency (utilization, throughput or revenue) subject to fairness constraints in a general telecommunications network for an arbitrary fairness criterion and cost functions. We formulate a non-linear program (NLP) that finds the optimal bandwidth allocation by maximizing efficiency subject to (@a,@b)-fairness constraints. This leads to what we call an efficiency-fairness function, which shows the benefit in efficiency as a function of the extent to which fairness is compromised. To solve the NLP we use two algorithms. The first is a well-known branch-and-bound-based algorithm called Lipschitz Global Optimization and the second is a recently developed algorithm called Algorithm for Global Optimization Problems (AGOP). We demonstrate the applicability of the framework to a range of examples from sharing a single link to efficiency fairness issues associated with serving customers in remote communities.

LAMOR: Lifetime-Aware Multipath Optimized Routing Algorithm for Video Transmission over Ad Hoc Networks

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