Since most ad hoc mobile devices today operate on batteries, energy-aware routings and power control techniques in
wireless networks have drawn considerable research interests recently. This paper presents a reliable energy-aware
routing algorithm (REARP) for unreliable ad hoc networks. The lifetime of the whole network and the energy cost for
each packet are considered simultaneously in the routing processes of the REARP. Different from the formers, the
energy cost of the link layer retransmission is also computed into the total energy consumption. Moreover, the REARP
appropriately adjusts the transmission power by systematically integrating the reliability and power control techniques.
We conducted extensive simulations to evaluate the performance of the new routing algorithms compared to a number of
existing routing algorithms.
Although IPv4 is still working, IPv6 is considered as the backbone and characteristic of the NGI. With the
development of Internet, new protocols and network equipments are required to develop. It is necessary to test the new
protocols and network equipments extensively before deployment. This paper proposes the design and implementation of
RENEW, a useable and accurate network emulator which supports both IPv4 and IPv6 protocols. Besides, it also works
on Windows platform. In our IPv6 testbed, we use RENEW to emulate various network characteristics and conditions
including bandwidth, delay packet loss and jitter. Compared with the expected values, results are acceptable. Through
implementation and experimentation study, we have shown that RENEW does provide the real-time control and change
on the parameters of IPv6 network conditions effectively and expediently on Windows. It also gives enough accuracy
and more satisfactory convenience to the development and test work for the new protocols.
We propose a congestion controller based on the Proportional-Integral-Differential Neuron Network (PIDNN). As
existing controllers, our controller employs the queue size in bottleneck link router as a congestion indicator to trigger
packet dropping. The target queue length and the feedback, actual queue length, act as the controller's two input signals.
The packet dropping probability is computed by PIDNN controller with its simple embedded algorithm in term of the
predefined state function and output function. Thus, the dropping probability decides to drop or to accept an incoming
packet so that the queue length is kept at (or near) the target level. This controller's performance is examined under
various network configurations, and compared to proposed congestion algorithms, including PI and RED. Our simulation
results show that, with comparable simple implementation, this scheme has short response time, better robustness, and
more adaptability, especially under highly dynamic network and heavy traffic load.
Load distribution across multiple parallel paths is an important consideration. In many practical contexts, the aggregate traffic from source to sink may be such that no single link can carry the load. In an MPLS domain, this problem can be addressed by instantiating multiple paths. The main objective of this paper balances traffic at the flow level among the parallel Label Switched Paths (LSPs) in MPLS networks. Different from other proposals, our new framework is based on the distributable traffic (DT), where cross-traffic in real networks is considered, and each LSP is modeled as an M/G/1 processor-sharing queue. We define a flow to be a sequence of packet having the same identifier, and dispatch packet belonging to one flow to the same path, so the packet disorder problem is avoided effectively. This mechanism only needs to be implemented in the ingress LSRs and the egress LSRs. A new defined cost function is being used to distribute traffic to path. We computer the cost function based on the delay and packet loss of each LSPs, and minimize the cost function. The minimized cost function is inverse ratio to DT. If the cost function of a certain LSP is smaller, it means that more traffic can be distributed on this LSP. Extensive simulations using NS2 are performed with MPLS modules. Simulation results show that our approach so effective that the throughput is increased significantly and reduces the end-to-end delay and the packet drop rate, and it can distribute the traffic onto parallel LSPs more evenly and fairly.
A robust PID controller for active queue management (AQM) based on modern H<sub>∞</sub> optimal control theory is presented in this paper. Taken both robustness and closed loop performance into consideration, most desirable parameters value can
be gotten through some straightforward analytical formulas. Our robust PID controller is determined only by one
parameter, other than traditional PID controller is by three or more. Additionally, this new parameters determining
method can not only be extended to other AQM controller based on classical control theory or optimal control theory, but
also be easily understood and implementation. We evaluate the performances of the controller extensively. The results
show that the robust PID congestion controller outperform the existing controller, such as PI, RED, on keeping the router
queue size at the target value. The most obvious property of the controller is that it takes on robustness such that it can
adapt the network dynamic.
In this paper, we employ real wireless data that draw from well known archives of network traffic traces and discusses
the characteristic of the aggregate WLAN traffic. We test the nonstationary of aggregate WLAN traffic by using the
Augmented Dickey-Fuller (ADF) based unit root test. The results show that we cannot reject the unit root for either of all
downstream traffic. We also repeat the analysis for the first difference of these series. The findings show that we can
strongly reject the unit root. These test reveal that the downstream traffic is nonstationary and integrated of order one.
Likewise, the same testing procedure for upstream traffic concluded that some of aggregate upstream traffic series are
stationary at the 5% level of significance, and some traffic series are nonstationary at the each level of significance. Our
result also showed that aggregate upstream traffic series are also integrated of order one.
The energy-constrained nature of wireless ad hoc networks calls for the protocols that use the energy efficiency as its
primary design goal. In order to evaluate and compare the energy-aware protocols in terms of their energy efficiency, an
energy-consumption model which can accurately compute the energy consumed by the data communication activities is
crucial. In this paper, we firstly give a comprehensive summary of the existing energy-consumption models. All energyconsumption
models are categorized into three types, and the characteristics of each type are discussed in detail.
Secondly, we propose a new efficient energy-consumption model which is a collection of functions of the packet size
and the RF (Radio Frequency) power level. The main contribution of our model is that all nodes in the model can change
their RF power-rate and radio states (e.g. transmitting, receiving, idle and sleep) according to the communication
requirement, and their energy cost can be calculated correctly. Finally, by comparing DSDV against dPAMEEL, we
show that our energy model can effectively calculate the energy consumption for different energy-aware protocols.
As the use of streaming media applications increased dramatically in recent years, streaming media security
becomes an important presumption, protecting the privacy. This paper proposes a new encryption scheme in view of
characteristics of streaming media and the disadvantage of the living method: encrypt the control message in the
streaming media with the high security lever and permute and confuse the data which is non control message according
to the corresponding control message. Here the so-called control message refers to the key data of the streaming media,
including the streaming media header and the header of the video frame, and the seed key. We encrypt the control
message using the public key encryption algorithm which can provide high security lever, such as RSA. At the same time
we make use of the seed key to generate key stream, from which the permutation list P responding to GOP (group of
picture) is derived. The plain text of the non-control message XORs the key stream and gets the middle cipher text. And
then obtained one is permutated according to P. In contrast the decryption process is the inverse process of the above.
We have set up a testbed for the above scheme and found our scheme is six to eight times faster than the conventional
method. It can be applied not only between PCs but also between handheld devices.
In this paper, Extreme Value Theory (EVT) is presented to analyze wireless network traffic. The role of EVT is to allow the development of procedures that are scientifically and statistically rational to estimate the extreme behavior of random processes. There are two primary methods for studying extremes: the Block Maximum (BM) method and the Points Over Threshold (POT) method. By taking limited traffic data that is greater than the threshold value, our experiment and analysis show the wireless network traffic model obtained with the EVT fits well with that of empirical distribution of traffic, thus illustrating that EVT has a good application foreground in the analysis of wireless network traffic.
With the fast development of ad hoc networks, SIP has attracted more and more attention in multimedia service. This paper proposes a new architecture to provide SIP service for ad hoc users, although there is no centralized SIP server deployed. In this solution, we provide the SIP service by the introduction of two nodes: Designated SIP Server (DS) and its Backup Server (BDS). The nodes of ad hoc network designate DS and BDS when they join the session nodes set and when some pre-defined events occur. A new sip message type called REGISTRAR is presented so nodes can send others REGISTRAR message to declare they want to be DS. According to the IP information taken in the message, an algorithm works like the election of DR and BDR in OSPF protocol is used to vote DS and BDS SIP servers. Naturally, the DS will be replaced by BDS when the DS is down for predicable or unpredictable reasons. To facilitate this, the DS should register to the BDS and transfer a backup of the SIP users' database. Considering the possibility DS or BDS may abruptly go down, a special policy is given. When there is no DS and BDS, a new election procedure is triggered just like the startup phase. The paper also describes how SIP works normally in the decentralized model as well as the evaluation of its performance. All sessions based on SIP in ad hoc such as DS voting have been tested in the real experiments within a 500m*500m square area where about 30 random nodes are placed.
Significant TCP unfairness in Ad Hoc wireless networks has been reported during the past several years.
proposed a network layer solution called Neighborhood Random Early Detection (NRED) scheme to enhance TCP
fairness in Ad Hoc wireless networks. In NRED, the concept of neighborhood is introduced. So the RED mechanism is
extended to the distributed neighborhood queue, which is the aggregation of local queue in one's neighborhood. NRED
adopt a passive measurement technique to detect the early congestion of a neighborhood. However, NRED by measuring
channel utilization rate is an over-layer solution and hardly to implement in practice. As it is known, packet delay
increases when the wireless channel is very busy and the overall traffic load exceeds the capacity of the channel. Thus
the packet delay can reflect whether or not the channel is busy. For each packet's transmission, the more delay, the more
severe congestion and competition. We believed that the delay of data could reflect the congestion of shared link
promptly. This paper proposes a scheme based on MAC delay to detect congestion and to notify the nodes which use too
much channel dropping their packets and give the expressed node chance to transmit. We analyze the average packet
delay on IEEE 802.11 DCF which is represented by a Markov model. Based on the relationship between the MAC delay
and number of competitors, whether there exist severe competition can be found.
This paper investigates saturation and nonsaturation load throughputs of node based on IEEE 802.11 wireless ad hoc network protocol in presence of selfish node. To analyze the throughput of nodes, an extended two-dimension Markov model was used and a general analytical solution was derived for DCF that may be used to find throughput under various traffic loads. Meanwhile, we have done extensive simulation using Qualnet to validate our analytic results. The analytic and simulation results matched well, which revealed three interesting insights: 1) The selfish node can maximize its throughput by adopting selfish behavior. And with the increase of selfish node, the throughput of selfish node decreases. 2) With the increase of initialized contention window size of selfish node, the throughput obtained by selfish node decreases. 3) The effect taken by the selfish behavior increases with the increase of the traffic load of node. When the traffic load is saturation, the throughput that the well-behaved node can get nearly approaches to zero, which is a very undesirable results.
Real-time video transmission over ad hoc networks faces many challenges including low bandwidth, long end-to-end
delay, high packet loss rate, frequently changing topology and limited-powered mobile nodes. This paper presents an
effective real-time video transmission scheme and improves implementation of DSR (Dynamic Source Routing)
protocol. We set up a test-bed by using DSR routing in the IP layer, and an application transmitting video stream over
UDP protocol. We get a continuous JPEG image stream from a ZC0301p web camera and split each image into small
blocks according to the MCU (Minimum Coding Unit) borderline. The strong point of splitting JPEG image is that IP
layer fragmentation can be avoided so we can determine which part of data in the frame gets lost to do loss recovery at
the receiver. By using JPEG image stream, the video encoding complexity is reduced, which can save computing power
of mobile nodes compared with MPEG and other Multiple Description Coding (MDC) methods. We also improve
implementation of DSR to make it suitable to transfer real-time multimedia data. First different priorities are given to
different traffic classes in DSR routing. Second the route maintenance scheme is modified to decrease overhead and link
failure misjudgments. We carry out two experiments both indoors and outdoors using six mobile nodes. The first is to
transmit continuous JPEG images using our former DSR implementation according to DSR draft. The second is that we
split JPEG images into blocks and then transmit them using improved DSR implementation. Results show the latter
gives better video stream fluency and higher image quality.
With the rapid development of computer and wireless communication technologies, the wireless ad hoc networks are receiving an increasing amount of attention due to its deployment and administration flexibilities. Thus various routing protocols have been developed for wireless ad hoc networks in recent years. This paper presents the results of simulation comparing three multi-hop wireless ad hoc network routing protocols that cover a range of single-path and multi-path source routing design choices: DSR, MSR and BSR. Simulation results demonstrate the performances of DSR, MSR and BSR revealed four interesting insights: (1) In lower mobility situations, multi-path routing MSR and BSR have similar performance as DSR, and three routing protocols being considered all have good performances. (2) In moderate situations of load and mobility, the performances of MSR and BSR are much more superior when compared to that of single-path DSR. And MSR has similar performance as BSR. (3) In heavy load and high mobility situations, BSR performs better than DSR and MSR. (4) In more challenging situations of high mobility, none of the routing protocols considered in this paper can respond to the dynamics in the network topology. The performances of DSR, MSR and BSR are all less than satisfactory.
Proc. SPIE. 6011, Performance, Quality of Service, and Control of Next-Generation Communication and Sensor Networks III
KEYWORDS: Signal attenuation, Microchannel plates, Reliability, Receivers, Local area networks, Wireless communications, Forward error correction, Standards development, Mobile communications, Algorithms
Reliable transport protocols such as TCP are tuned to perform well in traditional networks where packet losses occur mostly because of congestion. However, networks with wireless and other lossy links also suffer from significant non-congestion-related losses due to reasons such as bit errors and handoffs. TCP responds to all losses by invoking congestion control and avoidance algorithms, resulting in degraded end-to-end performance in wireless and lossy networks. In case of wired-wireless interaction (WLANs), the wireless link is assumed to be the last hop where most of the loss and delay occurs. Since the mobile host is adjacent to the wireless hops, it is obviously better equipped to obtain first-hand knowledge of the wireless links. In the paper, we proposed a mobile-host-centric transport protocol called MCP (Mobile-host Control Protocol) that is like TCP in its general behavior, but allows for better congestion control and loss recovery in mobile wireless networks. The MCP shifts most transport layer control policies to the mobile host side under all cases (mobile host is a sender or receiver, fixed or mobile, and so on). Therefore, mobile stations can make better transport layer control in time based on the condition of wireless link.
An understanding of the traffic characteristics and accurate traffic models are necessary for the improvement of the capability of wireless networks. In this paper we have analyzed the non-linear dynamical behavour of several real traffic traces collected from wireless testbeds. We have found strong evidence that the wireless traffic is chaotic from our observations. That is we found from the traffic correlation dimension, largest Lyapunov exponent and the principal components analysis, which are typical indicators of chaotic traffic. This gives us the good theoretical basis for the analysis and modeling of wireless traffic using Chaos Theory.
We study the dynamic allocation of bandwidth for video traffic in wireless networks. Our approach consists of two stages. In the first stage, we apply the FARIMA (Fractional Autoregressive Integrated Moving Average) models to forecast traffic based on online traffic measurements. In the second stage, we use the forecast results to allocate bandwidth dynamically. We evaluate our FARIMA-based scheme by comparing it with the ARIMA-based and the static schemes in terms of packet loss probability, queue length and bandwidth utilization. Through the experiments with real traffic traces, we demonstrate our approach works well for highly fluctuating traffic in WiFi.
This paper introduced the Extreme Value Theory (EVT) for analysis of network traffic. The role of EVT is to allow the development of procedures that are scientifically and statistically rational to estimate the extreme behavior of random processes. In this paper, we propose an EVT_based procedure to fit a model to the traffic trace. We have performed some simulation experiments on real-traffic traces such as video data to study the feasibility of our proposed method. Our experiments showed that the EVT method can be applied to statistical analysis of real traffic. Furthermore, since only the data greater than the threshold are processed, the computation overhead is reduced greatly. It indicates that EVT method could be applied to real time network control.
KEYWORDS: Internet, Atrial fibrillation, Control systems, Linear filtering, Computer simulations, Computer science, Process control, Information technology, Electronics engineering, Network architectures
In this paper, we propose a new active queue management mechanism called the RIO-SD (RED IN and OUT with Selective Dropping) to control ill-behaved flows in DiffServ networks. Under this scheme, core routers are not required to maintain per-flow state, and the ill-behaved flows can be identified based on the drop history of the "OUT-profile" virtual queue. Control is effected by placing two pre-filters in front of the "IN-profile" and "OUT-profile" virtual queues respectively. Simulation results indicate that our approach can also improve the performance of other normal flows. Our work demonstrates that our algorithm is robust and simple to use.