Behnam Banitalebi

Self-optimized collaborative data communication in wireless sensor networks

Collaborative data communication is one of the efficient approaches in wireless sensor networks (WSN) in terms of life-time, reliability and quality of service (QoS) enhancement. In this paper, we propose a new self-optimized collaborative algorithm which minimizes the energy consumption by decreasing the number of collaborative nodes and at the same time guarantees the demanded quality. To do this, we focus on the fact that during the collaboration, a receiver node aggregates the signals of the collaborative nodes separately. The major task of this node is the time adjustment of the collaborative nodes to receive their signals synchroneously. The proposed algorithm performs an extra process to sort the aggregated signals based on their bit error rate (BER) as the quality and select the minimum number of the nodes with higher rank for collaboration. It is because the low quality signals have negative effect on the collaboration performance, as confirmed experimentally. The new algorithm gains higher level of energy storage balance without increasing of the inter-node communications or computational load by modification of the node selection metric. It also guarantees the demanded QoS through modification of the collaboration based on the signal quality at the destination which results in higher reliability. Based on the proposed algorithm, sensor nodes can gain the optimum efficiency during collaborative data communication without external management resources. The algorithm is applicable in various scenarios and network structures.

On the feasibility of receive collaboration in wireless sensor networks

In this paper, a new type of collaboration in wireless sensor networks (WSN) is suggested that exploits array processing algorithms to improve the reception of a signal. For receive collaboration, the transmission power during intra-cluster transmissions decreases at the expense of increasing the inter-cluster communications. It is shown that, as a result of using receive collaboration, the destination nodes power consumption and the network interference level decrease which considerably improve the data transmission performance and network life time. This method is applicable both for cluster based and non-cluster based WSNs. In order to show the feasibility of receive collaboration and also to evaluate its performance, an LS-CMA based channel equalization scheme is also simulated which is performed during cooperation between cluster nodes. The comparison of the output BER between random distributed and uniform linear distributed cases shows a good performance of receive collaboration.

Effects of the transmission channel on the LS-CMA based beamformer in mobile communications

In mobile communications, transmission channel causes significant effects on the signal of mobile users received by the BTS. These changes can degrade the performance of the beamformer. In this paper, undesired effects of the transmission channel on the performance of the LS-CMA based beamformer are investigated both theoretically and through simulations. Investigations of this paper show that the effect of transmission channel on the beamformer performance depends on some parameters such as modulation technique used in the transmitter, mobile environment, and etc. But in general, phase error and angular spread have the worst effect on the beamformer performance.

Energy-efficient collaborative data collection in mobile wireless sensor networks

Mobile Wireless Sensor Networks (WSN) provide sensing coverage of huge areas by deploying mobile entities to collect sensing data from the static sensors and aggregate to the access points. Comparing with static WSN, such network can provide low cost, high throughput, large scale sensing coverage. However, data collection in mobile WSN strongly relies on the movement of the mobiles. Sensing data may not be collected effectively due to the limitation of the mobiles. In this paper, we introduce an energy efficient Collaborative Communication (CC) in WSN to ensure effective data collection in mobile WSN. Experiments on real taxi trajectories of 27; 000 taxis in the Beijing city show that energy efficient CC decrease the energy consumption of the urban sensing network in Beijing comparing with individual communication, with an ensurance of data collection ratio larger than 80%.

An improved channel access approach for emergency situations in IEEE 802.11 DCF

One important application scenario of ad-hoc wireless sensor networks is fire alarming which is considered in this paper. Although the speed of the network to report and monitor the situation has key role to decrease the damages, resource restricted and limited accessible bandwidth limit the packet delivery speed severely. In this paper, we applied the special packet generation pattern in such scenarios to optimize channel access schedule. We modified the back-off algorithm as a part of IEEE 802.11 Distributed Coordination Function (DCF). In the special case of Binary Exponential Back-off Algorithm (BEBA), we showed numerically how the performance of the network degrades due to the dramatically high increase in the packet generation rate. Our proposed modifications spanning static and dynamic situations outperforms the standard algorithm.

An improved multi-metric hop-cost model for wireless ad-hoc and sensor networks

Multi-metric hop cost model is an efficient way to improve the performance of routing protocols. Depending on the network objectives and characteristics various parameters like hop count, energy consumption, relay load affect the overall hop and path cost. In this paper, we propose other metrics reflecting transmission channel effects to make paths costs more realistic. Analyses confirm the outperformance of the new hop cost model when compared with the other models.

Transmission channel sensitive multi-metric routing for Wireless Sensor Networks

Multi-metric hop cost model is an efficient way to improve the performance of routing protocols and provide more flexibility. Depending on the network objectives and characteristics, various parameters like hop count, energy consumption, and relay load affect the overall hop and path cost. In this paper, after presentation of the situations which degrades the routing performance in WSNs, we propose a more realistic hop cost model including transmission loss, and energy storage and relay traffic of the nodes. Two methods to achieve metrics and apply the new model to the DV-based routing protocols are then presented. Numerical analyses approve the effectiveness of the new hop cost model to regulate the energy storage in the network and improve the energy efficiency by selection of the paths which have better quality in terms of transmission channel and node state. The cost of these improvements is an increase in the length of the path as the best path is not necessarily the shortest one. It is also shown that the effectiveness of the new model is controllable as the overall cost is a weighted summation of the old and new path cost metric.

Collaborative Channel Equalization: Analysis and Performance Evaluation of Distributed Aggregation Algorithms in WSNs

In wireless sensor networks (WSN), collaboration is a way to improve the quality of data communication between sensor nodes with restricted resources in terms of memory, processing and energy storage. For receive collaboration, various array processing schemes such as receive beamforming and collaborative channel equalization (CCE) can be used for aggregating data received by each node in the network. The key challenge is the limitation on the number of nodes which can collaborate because of the increased computational load and memory demand when the multiple signals are aggregated. This problem arises when sensor nodes in a CDMA based WSN collaborate, although the low power property of CDMA technique makes it suitable for WSN applications. Here receive collaboration is investigated in CDMA networks using CCE as the collaboration algorithm. We present two novel distributed signal aggregation algorithms: partial and hierarchical aggregation, which distribute computational load and memory demands on collaborative nodes. The positive impacts of receive collaboration on the signal quality and reliability are confirmed experimentally in a WSN scenario using software radios. Then the requirements of collaborative reception using CCE combined with the novel aggregation methods in terms of computational and memory load, as well as energy consumption are evaluated. The results indicate that the distributed signal aggregation algorithms, especially hierarchical aggregation, have computational and memory requirements less than that of centralized CCE, providing greater flexibility and scalability which enables collaboration in WSNs on a larger scale than previously possible.

Performance comparison of different STBC codes in the presence of IQ imbalances in mobile communications

In receivers, IQ imbalances have significant effects on the performance of data transmission. Comparison of the performance of different types of orthogonal space-time block codes (OSTBC) in the presence of IQ imbalances show that different codes donpsilat have a same behavior. Although most codes have an acceptable performance in low imbalances, they canpsilat work properly in the presence of intensive non-idealities. Despite this general similarity, there are some differences in the behavior of the codes against non-idealities. Such differences make them suitable for different situations.

Effect of Modifying Signal Parameters on the Beamforming Performance in CDMA Mobile Communications

In mobile communications, beamforming is one of the most efficient techniques to suppress undesired effects of the transmission channel. In a CDMA mobile communications system, there are some parameters such as PN code length of the CDMA signals and modulation type and order that usually are changed to increase the capacity and data bit rate. Variation of these parameters can change the beamformer performance. In this paper, effect of changing these parameters on the beamformer performance is investigated both theoretically and by using simulations. These investigations show that the above parameters have different effects on the beamformer performance