This paper considers the problem of power allocation for cooperative communication with multicast in coded wireless sensor networks (WSNs). We formulate and solve the problem using a cross-layer optimization framework, in which a simplified cooperative communication scheme that does not require channel state information (CSI) is considered. When compared against conventional cooperative and non-cooperative communication schemes under the same packet error rate (PER) objectives, the performance analysis shows that the simplified cooperative communication scheme achieves the lowest power cost. We then combine the simplified cooperative communication scheme with multicast using a linear optimization model, and show that for a random network topology, up to 40% power saving is achieved under stringent PER objectives.

In this paper, a heuristic approach is proposed to solve the problem of supporting both energy efficiency and quality of service (QoS) in time division multiple access (TDMA) based wireless sensor networks (WSNs). The proposed approach consists of a linear cross-layer optimization model and a slot reuse based TDMA scheduling algorithm, which are jointly inter-connected through a hop distance/slot reuse control parameter. Compared to existing approaches, both the analysis and simulation results show that the proposed approach provides more choices in deriving the optimal solution, which achieves significant power savings and competitive QoS support.

In this paper, we propose a solution to the scheduling problem in clustered wireless sensor networks (WSNs). The objective is to provide network-wide optimized time division multiple access (TDMA) schedules that can achieve high power efficiency, zero conflict, and reduced end-to-end delay. To achieve this objective, we first build a nonlinear cross-layer optimization model involving the network, medium access control (MAC), and physical layers, which aims at reducing the overall energy consumption. We solve this problem by transforming the model into two simpler subproblems. Based on the network-wide flow distribution calculated from the optimization model and transmission power on every link, we then propose an algorithm for deriving the TDMA schedules, utilizing the slot reuse concept to achieve minimum TDMA frame length. Numerical results reveal that our proposed solution reduces the energy consumption and delay significantly, while simultaneously satisfying a specified reliability objective.

In this paper, we propose an algorithm which is capable of forming reuse sets of links in time division multiple access (TDMA) based wireless sensor networks (WSNs) to gain less frame length. For each reuse set, we use linear programming to achieve optimal energy consumption. We further show how to apply this algorithm with end-to-end packet loss rate constraint. The major contribution of this paper is twofold. First, the proposed scheme gives an energy efficient way to support quality of service (QoS) requests such as delay (by reduced frame length) and end-to-end packet loss rate. Secondly, the relationships amongst energy consumption, frame length (thus delay) and packet loss rate in WSNs revealed in this paper can be utilized in designing WSNs with delay and packet loss constraints.

This paper studies time division multiple access (TDMA) scheduling with both energy efficiency and optimized delay in clustered wireless sensor networks (WSNs). To achieve this goal, we first build a cross-layer optimization model for attaining network wide efficient energy consumption. We solve this model by transforming it into simpler sub-problems that can be solved using conventional methods. We then propose a TDMA scheduling algorithm based on the input derived from the cross-layer optimization model. The proposed algorithm utilizes the slot reuse concept, which significantly reduces the end-to-end latency in WSNs, while retaining the feature of energy efficiency. In addition, the proposed solution in this paper is applied to clustered WSNs. This feature facilitates the application of our approach in large size WSNs.

Quality of service (QoS) support for real-time applications (e.g., voice) in mobile ad hoc networks (MANETs) has drawn much attention from researchers nowadays. Currently, most of the efforts are only concentrated on the routing algorithms. This paper shows that the design of QoS routing algorithms should not be treated in isolation but must also consider the feature of medium access control (MAC) layer and QoS metric collection schemes. We investigate the feasibility and effectiveness of voice support in multi- hop IEEE802.11 MANETs using the QoS constrained ad hoc on demand distance vector (AODV) routing protocol. Three main findings are presented in this paper. First of all, we found that, using QoS constrained AODV routing in multi-hop IEEE802.11 MANETs, voice communication can only be supported in a very limited manner (i.e., in a network composed of around a hundred nodes with pedestrian speed or less). Secondly, our simulations in OPNET and analysis show that IEEE802.11 performs poorly in multi-hop MANETs due to its hidden node problem, and is the major obstacle of voice support. Thus, new MAC protocols or improvements at the physical layer are needed to support voice with QoS guarantee in MANETs. Thirdly, we found that QoS routing metrics play an important role in determining the performance of a QoS routing algorithm, which should be selected with caution.

Support of real-time applications in Mobile Ad Hoc Networks (MANETs) is very challenging due to the dynamic characteristics of such networks. This paper studies the problem of voice application support in multi-hop IEEE802.11 ad hoc networks. We propose reactive-based and non-intrusive methods for calculating the quality of service (QoS) metrics of bandwidth, delay and packet loss that are important for voice support. Results from OPNET based simulations show that voice application can be supported in IEEE802.11 MANETs only under light traffic. When the network traffic is heavy, the calculated delay and packet loss become significantly high due to the hidden node problem, thus making it difficult to satisfy the voice delay and packet loss objectives in multi- hop IEEE802.11 MANETs.

Periodic broadcast protocols enable efficient streaming of highly popular media files to large numbers of concurrent clients. Most previous periodic broadcast protocols, however, assume that all clients can receive at the same rate, and also assume that reception bandwidth is not time-varying. In this article, we first develop a new periodic broadcast protocol, Optimized Heterogeneous Periodic Broadcast (OHPB), that can be optimized for a given population of clients with heterogeneous reception bandwidths and quality-of-service requirements. The OHPB protocol utilizes an optimized segment size progression determined by solving a linear optimization model that takes as input the client population characteristics and an objective function such as mean client startup delay. We then develop a generalization of the OHPB linear optimization model that allows optimal server bandwidth allocation among multiple concurrent OHPB broadcasts, wherein each media file and its clients may have different characteristics. Finally, we propose complementary client protocols employing work-ahead buffering of data during playback, so as to enable more uniform playback quality when the reception bandwidth is time-varying.

Periodic broadcast protocols enable the efficient streaming of highly popular media files to large numbers of concurrent clients. Most previous periodic broadcast protocols, however, assume that all clients can receive at the same rate, and also assume that available bandwidth is not time-varying. In this paper, we first develop a new periodic broadcast protocol, Optimized Heterogeneous Periodic Broadcast (OHPB), that can be optimized for a given population of clients with heterogeneous reception bandwidths and quality-of-service requirements. The OHPB protocol utilizes an optimized segment size progression determined by solving a linear optimization model that takes as input the client population characteristics and an objective function such as mean client startup delay. We then propose complementary client protocols employing work-ahead buffering of data during playback, so as to enable more uniform playback quality when the available bandwidth is time-varying.