http://jwcn.eurasipjournals.com The latest research articles published by EURASIP Journal on Wireless Communications and Networking 2012-05-18T00:00:00Z High spectral efficiency can be achieved in the downlink of multi-antenna coordinated multi-point systems provided that the multiuser interference is appropriately managed at the transmitter side. For this sake, downlink channel information needs to be sent back by the users, thus reducing the rate available at the uplink channel. The amount and type of feedback information required has been extensively studied and many limited feedback schemes have been proposed lately. A common pattern to all of them is that achieving low rates of feedback information is possible at the cost of increasing complexity at the user side and, sometimes, assuming that some statistics of the channel are known. In this article, we propose a simple and versatile limited feedback scheme that exploits the spatial correlation at each multi-antenna base station (BS) without requiring any previous statistical information of the channel and without adding significant computational complexity. It is based on the separate quantization of the channel impulse response modulus and phase and it shows better mean square error performance than the standard scheme based on quantization of real and imaginary parts. In order to evaluate the performance of the downlink regarding multiuser interference management, different precoding techniques at the BSs, such as zero-forcing (ZF), Tomlinson-Harashima precoding (THP) and lattice reduction Tomlinson-Harashima precoding (LRTHP), have been evaluated. Simulations results show that LRTHP and THP present a higher robustness than ZF precoding against channel quantization errors but at the cost of a higher complexity at the BS. Regarding sum-capacity and bit error rate performances, our versatile scheme achieves better results than the standard one in the medium and high SNR regime, that is, in the region where quantization errors are dominant against noise, for the same feedback cost measured in bits per user. http://jwcn.eurasipjournals.com/content/2012/1/176 Fernando Domene Gema Pinero Carmen Botella Alberto Gonzalez EURASIP Journal on Wireless Communications and Networking 2012, null:176 2012-05-18T00:00:00Z doi:10.1186/1687-1499-2012-176 /content/figures/1687-1499-2012-176-toc.gif EURASIP Journal on Wireless Communications and Networking 1687-1499 ${item.volume} 176 2012-05-18T00:00:00Z PDF In this article, we address the resource allocation problem for the downlink of a large network MIMO OFDMA system with 3-sector base stations (BSs). The system is statically divided into a number of disjoint clusters of sectors. A two-step resource allocation scheme is proposed involving the inter-cluster and the intra-cluster levels. As a first step or inter-cluster level, two cooperative frequency reuse approaches are designed to mitigate the inter-cluster interference. A user partition method is proposed to divide the users of each cluster into cluster-edge and cluster-center users. To balance the cell-edge and the cell-average performance, a fairness jug function is introduced to determine the frequency partition of the cooperative frequency reuse approaches. Then, as a second step or intra-cluster level, a utility-based joint scheduling and power allocation algorithm is proposed for each cluster, to maximize the sum utility of all users in the cluster under per-sector power constraints. Zero-forcing joint transmission is used across multiple sectors within the same cluster. Simulation results show that the proposed scheme can efficiently reduce the inter-cluster interference and provide considerable performance improvement in terms of both the cell-edge and cell-average user data rate. The proposed two-step resource allocation scheme can be implemented independently in each cluster without inter-cluster information exchange, which is an attractive property for practical systems, since it reduces both the network signaling overhead and the computational complexity. http://jwcn.eurasipjournals.com/content/2012/1/175 Jingya Li Carmen Botella Tommy Svensson EURASIP Journal on Wireless Communications and Networking 2012, null:175 2012-05-18T00:00:00Z doi:10.1186/1687-1499-2012-175 /content/figures/1687-1499-2012-175-toc.gif EURASIP Journal on Wireless Communications and Networking 1687-1499 ${item.volume} 175 2012-05-18T00:00:00Z PDF With the development of satellite communications, on-board processing (OBP) obtains more and more attentions due to the increased efficiency and performance. However, the large amounts of digital circuits in the OBP transponders are sensitive to the high-energy particles in space radiation environments, which may cause various kinds of Single Event Effect (SEE). Among these effects, Single Event Upset (SEU) is the major potential reason for the instability of the satellite communication systems. Triple modular redundancy (TMR) is a classical and effective method for mitigating the SEU in digital circuits. However, since three identical logic modules and a voting circuit are needed in TMR, the overhead is so high that the scheme may not be applicable on the on-board digital processing platform with very limited area and power resources. Therefore, how to design a more cost-effective fault-tolerant method becomes a critical issue. Considering that FIR-like processing is frequently used on OBP platform, in this paper, a Dual Modules plus Checking module based on Residue Code(DM-CRC) architecture for SEU-tolerant FIR design is proposed. Although this architecture reduces the area overhead dramatically, we find that the fault missing rate is still high if Single-Sample Checking(SSC) is used. To solve this problem, a Multi-Sample Checking DM-CRC(MSC-DM-CRC) is further proposed. Our analysis shows that the MSC-DM-CRC scheme can make the fault missing rate small enough without reducing the actual throughput. By simulations it is shown that, when the modulus for CRC is 7 and the number of samples for MSC is 4, the reduction of area overhead relative to TMR is ver 20% and the fault missing rate is as low as 0:05%. http://jwcn.eurasipjournals.com/content/2012/1/174 Wenhui Yang Zhen Gao Xiang Chen Ming Zhao Jing Wang EURASIP Journal on Wireless Communications and Networking 2012, null:174 2012-05-18T00:00:00Z doi:10.1186/1687-1499-2012-174 /content/figures/1687-1499-2012-174-toc.gif EURASIP Journal on Wireless Communications and Networking 1687-1499 ${item.volume} 174 2012-05-18T00:00:00Z PDF The Sensor Proxy Mobile IPv6 (SPMIPv6) has been designed for IP-based wireless sensor networks mobility to potentially save energy consumption by relieving the sensor nodes from participating in the handoff process. However, SPMIPv6 is dependent on a single and central Local Mobility Anchor (LMA), and thus, it inherited most of the problems observed in the Proxy Mobile IPv6 (PMIPv6) protocol, including long handoff latency, non-optimized communication path, and bottleneck issues. In addition, SPMIPv6 extends the single point of failure to include both the authentication and network information. This study presents an enhanced architecture for SPMIPv6 called Clustered SPMIPv6 (CSPMIPv6) to overcome the problems above. In the proposed architecture, the Mobility Access Gateways (MAGs) are grouped into clusters, each with a distinguished cluster Head MAG (HMAG). The HMAG is mainly designed to reduce the load on LMA by performing intra-cluster handoff signaling and providing an optimized path for data communications. The proposed architecture is evaluated analytically, and the numerical results show that the proposed CSPMIPv6 outperforms both SPMIPv6 and PMIPv6 protocols in terms of LMA load, local handoff delay, and transmission cost performance metrics. http://jwcn.eurasipjournals.com/content/2012/1/173 Adnan Jabir Shamala Subramaniam Zuriati Ahmad Nor Asila Wati Hamid EURASIP Journal on Wireless Communications and Networking 2012, null:173 2012-05-17T00:00:00Z doi:10.1186/1687-1499-2012-173 /content/figures/1687-1499-2012-173-toc.gif EURASIP Journal on Wireless Communications and Networking 1687-1499 ${item.volume} 173 2012-05-17T00:00:00Z PDF In this article, efficient power saving scheme and corresponding algorithm must be developed and designed in order to provide reasonable energy consumption and to improve the network lifetime for wireless sensor network systems. The cluster-based technique is one of the approaches to reduce energy consumption in wireless sensor networks. In this article, we propose a saving energy clustering algorithm to provide efficient energy consumption in such networks. The main idea of this article is to reduce data transmission distance of sensor nodes in wireless sensor networks by using the uniform cluster concepts. In order to make an ideal distribution for sensor node clusters, we calculate the average distance between the sensor nodes and take into account the residual energy for selecting the appropriate cluster head nodes. The lifetime of wireless sensor networks is extended by using the uniform cluster location and balancing the network loading among the clusters. Simulation results indicate the superior performance of our proposed algorithm to strike the appropriate performance in the energy consumption and network lifetime for the wireless sensor networks. http://jwcn.eurasipjournals.com/content/2012/1/172 Jau-Yang Chang Pei-Hao Ju EURASIP Journal on Wireless Communications and Networking 2012, null:172 2012-05-16T00:00:00Z doi:10.1186/1687-1499-2012-172 /content/figures/1687-1499-2012-172-toc.gif EURASIP Journal on Wireless Communications and Networking 1687-1499 ${item.volume} 172 2012-05-16T00:00:00Z PDF The greedy perimeter stateless routing (GPSR) protocol is a well-known position-based routing protocol. Data packet routing in position-based routing protocols uses the neighbors' geographical position information, which is stored in the sender's neighbors list, and the destination's position information stored in the routing data packet header field to route the packet from source to destination. In the GPSR protocol, the sender routes the packets to a neighboring node, whose geographical position is the closest to the destination of all the sender's neighbors. However, the selected neighbor is closer to the edge of the maximum of the sender's transmission range and thus has a higher likelihood of leaving the transmission range of the sender. Thus, the wireless link between the sender node and its routing neighboring node may break down, which degrades the performance of the routing protocol. In this study, we identify and study the effects of network parameters (beacon packet interval-time, node speed, network density, transmission range, and network area size) on wireless link breakage, identified as the neighbor wireless link break (NWLB) problem, in the GPSR protocol. To overcome the NWLB problem, we propose a neighbor wireless link break prediction (NWLBP) model. The NWLBP model predicts the accurate position of a routing neighboring node in the sender's neighbors list before routing the data packet to that neighbor. The simulation results show the ability of the NWLBP model to overcome the observed problem and to improve the overall performance of the GPSR protocol. http://jwcn.eurasipjournals.com/content/2012/1/171 Raed Alsaqour Maha Abdelhaq Ola Alsukour EURASIP Journal on Wireless Communications and Networking 2012, null:171 2012-05-16T00:00:00Z doi:10.1186/1687-1499-2012-171 /content/figures/1687-1499-2012-171-toc.gif EURASIP Journal on Wireless Communications and Networking 1687-1499 ${item.volume} 171 2012-05-16T00:00:00Z PDF In mobile technologies two trends are competing. On the one hand, the mobile access network requires optimisation in energy consumption. On the other hand, data volumes and required bit rates are rapidly increasing. The latter trend requires the deployment of more dense mobile access networks as the higher bit rates are available at shorter distance from the base station. In order to improve the energy efficiency, the introduction of sleep modes is required. We derivea heuristic which allows establishing a baseline of active base station fractions in order to be able to evaluate mobile access network designs. We demonstrate that sleep modes can lead tosignificant improvements in energy efficiency and act as an enabler for femtocell deployments. http://jwcn.eurasipjournals.com/content/2012/1/170 Willem Vereecken Margot Deruyck Didier Colle Wout Joseph Mario Pickavet Luc Martens Piet Demeester EURASIP Journal on Wireless Communications and Networking 2012, null:170 2012-05-15T00:00:00Z doi:10.1186/1687-1499-2012-170 /content/figures/1687-1499-2012-170-toc.gif EURASIP Journal on Wireless Communications and Networking 1687-1499 ${item.volume} 170 2012-05-15T00:00:00Z PDF We propose a new approach for timing synchronization estimation with polarity comparison for multi-band orthogonal frequency division multiplexing (MB-OFDM)-based UWB systems. We attempt to locate the start sample of frame sequences by calculating difference of the two cross-correlation functions, between received symbols, the successive received symbols, and predefined preamble sequence. It makes sense to propose polarity comparison and identification ideas to the scenario, the cross-correlation difference exceeding predefined threshold is not unique. If polarities of selected symbols are not all the same, the estimator is put forward to find out a peak of correlation summation to figure out the unique timing point and promote synchronization accuracy. Uniqueness and accuracy of timing synchronization, therefore, could be guaranteed. The performance of the proposed estimator is evaluated by mean square error (MSE) and synchronization probability. The proposed estimator could carry out timing synchronization for MB-OFDM-based UWB systems and make the uniqueness of timing index for sure. The MSEs of the proposed estimator are evidently lower than the reference method for a great deal. Total and exact synchronization probability could get as much as 100 and 96%. http://jwcn.eurasipjournals.com/content/2012/1/169 Xue Wang Zhihong Qian Yijun Wang EURASIP Journal on Wireless Communications and Networking 2012, null:169 2012-05-14T00:00:00Z doi:10.1186/1687-1499-2012-169 /content/figures/1687-1499-2012-169-toc.gif EURASIP Journal on Wireless Communications and Networking 1687-1499 ${item.volume} 169 2012-05-14T00:00:00Z PDF IEEE 802.11p is an approved amendment to the IEEE 802.11 standard to facilitate wireless access in vehicular environments (WAVE). In this article, we present an analytical model to evaluate the impact of vehicle mobility on the saturation throughput of IEEE 802.11p-based vehicle-to-infrastructure (V2I) networks. The throughput model is then used to investigate an unfairness problem that exists in such networks among vehicles with different mobility characteristics. Assuming a saturated network, if all the vehicles in the network use the same MAC parameters, IEEE 802.11p MAC protocol provides equal transmission opportunity for all of them, provided they have equal residence time in the coverage area of a road side unit (RSU). When vehicles have different mobility characteristics (e.g., extremely high and low speeds), they do not have similar chances of channel access. A vehicle moving with higher velocity has less chance to communicate with its RSU, as compared to a slow moving vehicle, due to its short residence time in the coverage area of RSU. Accordingly, the data transfer of a higher velocity vehicle gets degraded significantly, as compared to that of the vehicle with lower velocity, resulting in unfairness among them. In this article, our aim is to address this unfairness problem that exists among vehicles of different velocities in V2I networks. Analytical expressions are derived for optimal minimum CW (CWmin) required to ensure fairness, in the sense of equal chance of communicating with RSU, among competing vehicles of different mean velocities in the network. Analytical results are validated using extensive simulations. http://jwcn.eurasipjournals.com/content/2012/1/168 Vettath Pathayapurayil Harigovindan Anchare Babu Lillykutty Jacob EURASIP Journal on Wireless Communications and Networking 2012, null:168 2012-05-14T00:00:00Z doi:10.1186/1687-1499-2012-168 /content/figures/1687-1499-2012-168-toc.gif EURASIP Journal on Wireless Communications and Networking 1687-1499 ${item.volume} 168 2012-05-14T00:00:00Z PDF Developing energy efficient MAC protocols for lightweight wireless systems has been a challenging task for decades because of the specific requirements of various applications and the varying environments in which wireless systems are deployed. Many MAC protocols for wireless networks have been proposed, often custom-made for a specific application. It is clear that one MAC does not fit all the requirements. So how should a MAC layer deal with an application that has several modes (each with different requirements) or with the deployment of another application during the lifetime of the system? Especially in a mobile wireless system, like Smart Monitoring of Containers, we cannot know in advance the application state (empty container vs. stuffed container). Dynamic switching between different energy efficient MAC strategies is needed. Our architecture, called PluralisMAC, contains a generic multi-MAC framework and a generic neighbour monitoring and filtering framework. To validate the real-world feasibility of our architecture, we have implemented it in TinyOS and we have done experiments on the TMote Sky nodes in the iLab.t testbed. Experimental results show that dynamic switching between MAC strategies is possible with minimal receive chain overhead, while meeting the various application requirements (reliability and low energy consumption). http://jwcn.eurasipjournals.com/content/2012/1/166 Pieter De Mil Peter Ruckebusch Jeroen Hoebeke Ingrid Moerman Piet Demeester EURASIP Journal on Wireless Communications and Networking 2012, null:166 2012-05-10T00:00:00Z doi:10.1186/1687-1499-2012-166 /content/figures/1687-1499-2012-166-toc.gif EURASIP Journal on Wireless Communications and Networking 1687-1499 ${item.volume} 166 2012-05-10T00:00:00Z PDF