Abstract
The concept of cooperative communications for wireless ad hoc and sensor networks (WAHSNs) has recently attracted considerable attention. Being different from conventional point-to-point communications, cooperative communications allow different users or nodes in a WAHSN to share resources to create collaboration through distributed transmission. It realizes a new form of spatial diversity to combat the effects of severe fading; thus, it can be used widely in WAHSNs for the sake of resource minimization. However, the impact and challenges of cooperative communication in WAHSNs are not well understood yet. Some fundamental aspects requiring immediate studies include theoretical tools for cooperative networks, effective incentive mechanisms for cooperation, and new protocol design for cooperative networks. This issue tries to collect cutting-edge research achievements in this special area.
The paper entitled “Improved message diffusion model for node coverage problem of ad hoc network based on node visit times,” by Z. Yang et al., analyzes the causes of the inaccuracy problems of random sampling model and solves the problems by specially introducing the factors such as node degree and visit times. As for the E-R random network topology, it validates the effectiveness of the model proposed herein in contrast to the simulation experiment results.
In the paper entitled “Distributed testbed for coded cooperation with software-defined radios,” by C. Han and S. Li, the authors design and implement a distributed hardware testbed using software-defined radios for cooperative communication, and the performance of two coded cooperation schemes with turbo codes is evaluated in the physical layer. Furthermore, a distributed node synchronization scheme is implemented and the source node and relay node work in the time division protocol without any centralized controlling.
The paper entitled “Energy efficient power allocation for bidirectional relaying with imperfect channel estimation,” by S. Li et al., investigates the power allocation problem to minimize the total transmit power subject to constraints on two source nodes’ received signal-to-noise-ratios (SNRs). The best relay that minimizes the total transmit power is selected in a multiple relay network. They also present outage analysis when the proposed power allocation is adopted and a close-form approximation of outage probability is obtained by shrinking the integral interval.
The paper entitled “Hierarchical spatial clustering in multihop wireless sensor networks,” by Z. Liu et al., considers the problem of spatial clustering for approximate data collection that is feasible and energy efficient for environment monitoring applications. They propose a clustering algorithm named HSC to group the most similar sensor nodes in a distributed way. HSC runs on a prebuilt data collection tree and thus gets rid of some extra requirements such as global network topology information and rigorous time synchronization.
The paper entitled “Joint relay ordering and linear finite field network coding for multiple-source multiple-relay wireless sensor networks,” by Y. Cheng and L. Yang, proposes a relay ordering algorithm based on finite field NC (FFNC). In the scheme, the relays who initially fail to decode from sources are kept listening and searching for the opportunity to decode the signals from other relays, so as to recover the failure links. Moreover, the scheme is proved to own the merit of diffusion effect, which makes the diversity improvement more efficient by simply increasing the relay number in the network.
The paper entitled “Application of baro-altimeter sensor in emergency positioning and navigation based on compass GEO satellites,” by J. Zhan et al., presents a low-cost high-resolution MS5534B barometric (baro-) module which applies to BDS. Firstly, the principle of emergency positioning based on a baro-altimeter sensor and its performance such as the accuracy are elaborated. Then the effects of baro-altimeter sensor measurement error on positioning are analyzed. Finally, after analyzing the limitation of the conventional algorithms, a new high-accuracy emergency positioning algorithm with baro-altimeter sensor aiding is proposed, which is not limited by the integration and user's altitude.
The paper entitled “Throughput-optimal scheduling for cooperative communications in wireless ad hoc networks,” by T. Huynh et al., introduces the relay selection schemes that can control the interference at the relay to prevent the relay that may harm other pairs. Then, they propose the throughput-optimal scheduling that takes into account error probability in decision and maximizes throughput, that is, the amount of packets transmitted without error in network.
The paper entitled “A service model for 6LoWPAN wireless sensor networks,” by X. Wang and H. Huang, proposes a 6LoWPAN service model based on the IPv6-based k-Anycast communication model. This model is extended into 6LoWPAN service model so that the data-centric services of WSN can be achieved efficiently in the address-centric 6LoWPAN.