Several modifications of aggressive packet combining scheme for wireless networks

Power control in wireless networks is useful for minimizing channel congestion (hence increasing network capacity). In this work, we show how the distributed power control algorithm with active link protection (DCP-ALP) can be used as a channel probing tool that allows a new link trying to access a channel to quickly and autonomously determine whether it can be admitted to it (i.e. whether there is a feasible power configuration for the transmitters such that the link quality requirements on all links are met), which significantly improves the capacity and access time of the network.

We evaluate the performance of an adaptive error correction scheme for wireless ATM networks (WATM). This scheme attempts to minimize the system throughput in order to satisfy the user defined quality of service (QoS) constraints. Indeed, error control for high speed wireless ATM networks is an important research topic, even wireless communication channels are highly affected by unpredictable factors like co-channel interference, adjacent channel interference, propagation path loss and multipath fading. We propose an intelligent-agent architecture to implement our mechanism A-BCH-FEC (adaptive BCH FEC scheme) for a Rayleigh fading environment. Intelligent agents are distributed over all system entities. In the latter, base station agents cooperate with other agents to choose the appropriate BCH coding scheme related to a specific level of signal-to-noise-ratio (SNR). Finally, we illustrate our implementation by some simulation results from a cellular system. These results show that the adaptive scheme using BCH codes improves significantly the system performance.

In this paper, we study cross-layer design for rate control in multihop wireless networks. In our previous work, we have developed an optimal cross-layered rate control scheme that jointly computes both the rate allocation and the stabilizing schedule that controls the resources at the underlying layers. However, the scheduling component in this optimal cross-layered rate control scheme has to solve a complex global optimization problem at each time, and hence is too computationally expensive for online implementation. In this paper, we study how the performance of cross-layer rate control can be impacted if the network can only use an imperfect (and potentially distributed) scheduling component that is easier to implement. We study both the case when the number of users in the system is fixed and the case with dynamic arrivals and departures of the users, and we establish desirable results on the performance bounds of cross-layered rate control with imperfect scheduling. Compared with a layered approach that does not design rate control and scheduling together, our cross-layered approach has provably better performance bounds, and substantially outperforms the layered approach. The insights drawn from our analyses also enable us to design a fully distributed cross-layered rate control and scheduling algorithm for a restrictive interference model.

In recent years, with the development of wireless communication technique and urgent requirement of industry, wireless network technology has been widely applied to industry distributed control system. The existing standardized wireless network protocol which has been applied can’t meet the above requirements, so there is need to apply some mechanism and design method to establish new and practical wireless distributive real-time system for industry. The paper proposes a wireless control network based on flexible time trigger mechanism to meet the time requirement of real-time application. The paper introduces the concept of flexible time trigger mechanism, and describes wireless control network model based on flexible time trigger mechanism. The paper explains the concept of flexible time trigger mechanism, and expounds how to apply the mechanism to establish wireless control network.

Wireless control network require delay guarantees and low packet error rates. The reason for communication delay and error is packet loss, and TDMA is used by many wireless control network technologies to avoid packet loss. However, TDMA protocols are difficult to implement. Besides, TDMA cannot avoid communication failure points due to changes in the environment caused by human intervention. We propose NES-SOURCE as a CSMA/CA based control network protocol. NES-SOURCE uses a source routing protocol, and if the NES-SOURCE node fails to communicate using primary route, the node avoid the communication failure point by to use secondary bypass route. NES-SOURCE is a low delay protocol. The reason is that NES-SOURCE can change the communication route at high speed. In addition, NES-SOUCE is implemented using a protocol stack that is compatible with IEEE 802.15.4 g. We show that NES-SOURCE systems can be used for wireless control network systems, and in an environment where people moving are in and out, path change is more advantageous than retransmission from the point of view of the packet error rate.

The convenience and flexibility of wireless networks to allow clients (user nodes) to be connected to the network at any place and any time have resulted in the growth and increased popularity of wireless networks. Access control in wireless networks is very important to prevent unauthorized users from accessing the network. Besides this, client anonymity and resistance to Denial-of-Service (DoS) attacks are also important and should be provided by access control protocols for wireless networks. Password-based authentication provide good solutions for access control protocols, however they usually do not provide client identity confidentiality and DoS resistance. In this paper, we review a DoS-resistant anonymous access control (AAC) protocol and point out that the protocol does not provide protection against three different DoS attacks. We then propose a new DoS-resistant AAC protocol that avoids the flaws of the previous protocol. Our proposed protocol also provides client anonymity and protection against DoS attacks. A security and complexity analysis shows that our proposed protocol is secure and efficient for access control in wireless networks.

The use of power control in wireless networks can lead to two conflicting effects. An increase in the transmission power on a link may (i) improve the quality and thus the throughput on that link but, (ii) increase the levels of interference on other links. A decrease in the transmission power can have the opposite effects. Our primary goal in this work is to understand the implications of power control on interference and contention. We conduct experiments on an indoor mesh network. Based on analysis of our experimental data, we identify three interference scenarios: a) the overlapping case, where the aggregate throughput achievable with two overlapping links cannot be improved via power control; b) the hidden terminal case, where proper power control can primarily improve fairness and, c) the potentially disjoint case, where proper power control can enable simultaneous transmissions and thus improve throughput dramatically. We find that power control can significantly improve overall throughput as well as fairness. However, to our surprise, we note that using virtual carrier sensing in conjunction with power control generally degrades performance, often to a large degree.

The rapid deployment of wireless mesh networks across universities and enterprises, and the pervasiveness of mobile devices equipped with Wi-Fi connectivity, has resulted in a scenario wherein end users have the option to choose from a multitude of access points at any given location. Moreover, with the increasing availability of rich online content, there has been a steady increase in mobile Internet traffic. Since the choice of access point that a user associates with will directly impact his performance, it is imperative that there exist an efficient association control mechanism, in order to enhance the end user's experience. As part of this work, we propose Seeker, a novel framework for association control in wireless networks that utilizes "available bandwidth" as the design metric. The goal of Seeker is to assist the mesh network in making an intelligent decision regarding which access point a client should associate with. As part of our scheme, we implement and evaluate a passive tool to estimate available bandwidth in wireless networks. We then describe how we use this tool to implement our association control scheme, and evaluate it via extensive experiments on an outdoor testbed. Seeker takes into consideration the performance of the mesh backhaul, in addition to the client-to-AP link quality, thereby achieving significant advantages over traditional association control schemes for wireless-LANs.

In wireless communications networks with multiple service classes (SCs) of calls, call admission control (CAC) schemes is an essential radio resource management (RRM) function for networks consistency. Apart from the calculation of the call blocking probability (CBP) appropriate criteria and metrics should be considered to evaluate the efficiency of various schemes. Fairness among different services is an important efficiency criterion for CAC in wireless networks with multimedia services while throughput is an efficiency criterion of general validity. In the present paper, four CAC schemes based on guard channel algorithms are proposed for multiclass services, offering priority to real time service class calls while ensuring a certain level of quality of service (QoS). The proposed schemes investigate the CAC problem in terms of ongoing users and occupied channels. Fairness among calls of different classes is evaluated and the network performance is compared with respect to input load.

From a theoretical standpoint, backpressure-based techniques present elegant cross-layer rate control solutions that use only local queue information. It is only recently that attempts are being made to design real world wireless protocols using these techniques. To aid this effort, we undertake a comprehensive experimental evaluation of backpressure mechanisms for multihop wireless networks, in particular, the first such study in the context of wireless sensor networks. Our evaluation yields two key insights into the design of such protocols. First, for wireless sensor networks, we show that a simple backpressure scheduling policy which allows nodes to transmit so long as they have a positive queue differential (irrespective of its size) gives performance comparable to more sophisticated heuristics. The advantage of this approach is that no changes are required to the underlying MAC. Second, we show that the performance of backpressure based protocols is highly sensitive to a parameter setting that depends upon current traffic conditions. Therefore, practical backpressure protocols must provide for automatic parameter adaptation.

Wireless Local Area Networks (WLANs) and Wireless Metropolitan Area Networks (WMANs) are two of the main technologies in wireless data networks. WLANs have a short range and aim at providing connectivity to end users. On the other hand, WMANs have a long range and aim at serving as a backbone network and also at serving end users. In this dissertation, we consider the problem of Medium Access Control (MAC) in WLANs and the placement of Relay Stations (RSs) in WMANs. We propose a MAC scheme for WLANs in which stations contend by using jams on the channel. We present analytic and simulation results to find the optimal parameters of the scheme and measure its performance. Our scheme has a low collision rate and delay and a high throughput and fairness performance. Secondly, we present a MAC scheme for the latest generation of WLANs which have very high data rates. In this scheme, we divide the stations into groups and only one station from each group contends to the channel. We also use frame aggregation to reduce the overhead. We present analytic and simulation results which show that our scheme provides a small collision rate and, hence, achieves a high throughput. The results also show that our scheme provides a delay performance that is suitable for real-time applications and also has a high level of fairness. Finally, we consider the problem of placing Relay Stations (RSs) in WMANs. We consider the Worldwide Interoperability for Microwave Access (WIMAX) technology. The RSs are used to increase the capacity of the network and to extend its range. We present an optimization formulation that places RSs in the WiMAX network to serve a number of customers with a pre-defined bit rate. Our solution also provides fault-tolerance by allowing one RS to fail at a given time so that the performance to the users remains at a predictable level. The goal of our solution is to meet the demands of the users, provide fault-tolerance and minimize the number of RSs used.

Wireless networks are defined as that the network nodes which are connected by wireless data connections. The devices are connected via wireless link to communicate with each other. Measuring the delay performance of end-to-end nodes is the one of the most convoluted issues in wireless networks. In wireless networks, it is very difficult to maintain the substitution between throughput and delay. This paper proposes a new joint scheduling and congestion control algorithm for multihop wireless networks with dynamic route flows. The proposed algorithm achieves a provable throughput guarantee and provable end-to-end delay of every flow. The new joint scheduling and congestion control algorithm improves throughput and delay for dynamic wireless network by shifting scheduling scheme with virtual adaptation model. The proposed algorithm combines window-based flow control with a new rate based distributed scheduling algorithm to survive the quality of the system. This approach adaptively selects a set of routes according to the traffic load. Furthermore this dynamic adaptation mechanism achieves better concert in terms of throughput, end-to-end delay and packet delivery ratio.

This work develops a novel power control framework for energy-efficient power control in wireless networks. The proposed method is a new branch-and-bound procedure based on problem-specific bounds for energy-efficiency maximization that allow for faster convergence. This enables to find the global solution for all of the most common energy-efficient power control problems with a complexity that, although still exponential in the number of variables, is much lower than other available global optimization frameworks. Moreover, the reduced complexity of the proposed framework allows its practical implementation through the use of deep neural networks. Specifically, thanks to its reduced complexity, the proposed method can be used to train an artificial neural network to predict the optimal resource allocation. This is in contrast with other power control methods based on deep learning, which train the neural network based on suboptimal power allocations due to the large complexity that generating large training sets of optimal power allocations would have with available global optimization methods. As a benchmark, we also develop a novel first-order optimal power allocation algorithm. Numerical results show that a neural network can be trained to predict the optimal power allocation policy.

To increase the processing capabilities of mobile devices, mobile edge computing (MEC), has garnered a lot of attention. Computation offloading is a significant challenge in the MEC paradigm. This paper proposes an all-encompassing framework for MEC-based computation offloading and interference control in wireless networks. The allocation of physical resource blocks (PRBs), MEC computation resource allocation, and computation offloading decisions are all formulated as optimization issues within this integrated framework. Depending on each UE’s estimated local computational load and the MEC server’s estimated offloading cost, the MEC server chooses whether or not to offload work. Following this, the MEC server runs the PRB allotment graph colouring procedure. Computational resources on the MEC server are divided up among UEs results on basis of offloading choice and PRB distribution. Simulated results are shown to illustrate the effectiveness of the proposed technique using a range of system parameters.

Resource allocation and admission control algorithm based on non-cooperation game in wireless mesh networks