Cluster Base Station Research Articles

Joint Base Station Clustering and Beamformer Design for Partial Coordinated Transmission in Heterogeneous Networks

We consider the interference management problem in a multicell MIMO heterogeneous network. Within each cell there is a large number of distributed micro/pico base stations (BSs) that can be potentially coordinated for joint transmission. To reduce coordination overhead, we consider user-centric BS clustering so that each user is served by only a small number of (potentially overlapping) BSs. Thus, given the channel state information, our objective is to jointly design the BS clustering and the linear beamformers for all BSs in the network. In this paper, we formulate this problem from a {sparse optimization} perspective, and propose an efficient algorithm that is based on iteratively solving a sequence of group LASSO problems. A novel feature of the proposed algorithm is that it performs BS clustering and beamformer design jointly rather than separately as is done in the existing approaches for partial coordinated transmission. Moreover, the cluster size can be controlled by adjusting a single penalty parameter in the nonsmooth regularized utility function. The convergence of the proposed algorithm (to a stationary solution) is guaranteed, and its effectiveness is demonstrated via extensive simulation.

MED-BS Clustering Algorithm for the Small-Scale Wireless Sensor Networks

With the spectacular progress of technology, we have witnessed the appearance of wireless sensor networks (WSNs) in several fields. In a hospital for example, each patient will be provided with one or more wireless sensors that gather his physiological data and send them towards a base station to treat them on behalf of the clinicians. The WSNs can be integrated on a building surface to supervise the state of the structure at the time of a destroying event such as an earthquake or an explosion. In this paper, we presented a Mobility-Energy-Degree-Distance to the Base Station (MED-BS) Clustering Algorithm for the small-scale wireless Sensor Networks. A node with lower mobility, higher residual energy, higher degree and closer to the base station is more likely elected as a clusterhead. The members of each cluster communicate directly with their ClusterHeads (CHs) and each ClusterHead aggregates the received messages and transmits them directly to the base station. The principal goal of our algorithm is to reduce the energy consumption and to balance the energy load among all nodes. In order to ensure the reliability of MED-BS, we compared it with the LEACH (Low Energy Adaptive Clustering Hierarchy) clustering algorithm. Simulation results prove that MED-BS improves the energy consumption efficiency and constructs a stable structure which can support new sensors without returning to the clusters reconstruction phase.

Implementation of Cellular IP and Its Performance Analysis

In the current Cellular IP architecture, only one gateway serves the entire CIP network. So, the gateway is single point of failure for all the mobile hosts who rely on it to be connected to the Internet. Cellular IP requires that a mobile host be using exactly one gateway to the Internet backbone with Mobile IP at a time. When multiply gateways are used in a cellular IP network, the optimal design for the multiple domains is needed. The cellular IP protocol provides better performance for hand-off than other protocol using micro- mobility. A set of base station cluster together on the same cellular IP network. This kind of domain base network is superior to mobile IP in support of routing optimization and QoS. Experiment were conduct to explore load our protocol and survey the packet loss. This result so that the load of control packet is negligible for cellular IP and the number of lost packet can be successfully reduced. This thesis developed to design cellular IP architecture and fault detection mechanism and recover the protocol of cellular IP. Keywords; Protocol Overview, Network Model, Routing, Handoff, Paging, Security, Implement Cellular IP Network Model, Protocol Details, Simulation Results, Conclusions.

An Enhanced Link Adaptation Scheme Based on Cooperative Interference Prediction for MIMO-OFDM Systems

Dynamic inter-cell interference (ICI) causes channel quality indicator mismatch such that system throughput is reduced. In this paper, an enhanced link adaptation scheme based on cooperative interference prediction is proposed to reduce the mismatch. The scheme predicts the dynamic ICI within a cluster of base stations (BSs) for improving the link adaptation accuracy. With the dynamic ICI prediction, more accurate modulation and coding scheme can be selected without increasing the overhead over the air. System level simulations show that the proposed scheme significantly improves the system spectral efficiency (SE), especially the cell-edge SE.

Heterogeneous Dynamic Priority Scheduling in Time Critical Applications

In the unlicensed band, the notion of primary user and secondary user (To implement cognitive radio) is not explicit. By dynamic priority assignment the authors propose to implement cognitive radio in the unlicensed band. In time critical events, the data which is most important, has to be given the time slots. Wireless Sensor nodes in the authors’ case are considered to be mobile, and hence make it difficult to prioritize one over another. A node may be out of the reach of the cluster head or base station by the time it is allotted a time slot and hence mobility is a constraint. With the data changing dynamically and factors such as energy and mobility, which are major constraints, assigning priority to the nodes becomes difficult. In this paper, the authors have discussed about how Wireless Sensor Networks are able to allocate priorities to nodes in the unlicensed band with multiple parameters being posed. They have done simulations on NS-2 and have shown the implementation results.

CoMP clustering and backhaul limitations in cooperative cellular mobile access networks

Coordinated Multi-Point (CoMP) transmission and reception is a promising solution for managing interference and increasing performance in future wireless cellular systems. Due to its strict requirements in terms of capacity, latency, and synchronization among cooperating Base Stations (BSs), its successful deployment depends on the capability of the mobile backhaul network infrastructure.We deal with the feasibility of CoMP transmission/reception, in particular of Joint Transmission (JT). For this, we first evaluate which cluster sizes are reasonable from the wireless point-of-view to achieve the desired performance gains. Thereafter, we analyze how different backhaul topologies (e.g., mesh and tree structures) and backhaul network technologies (e.g., layer-2 switching and single-copy multicast capabilities) can support these desired clusters. We study for different traffic scenarios and backhaul connectivity levels, which part of the desired BS clusters are actually feasible according to the backhaul characteristics. We found out that a significant mismatch exists between the desired and feasible clusters. Neglecting this mismatch causes overheads in real JT implementations, which complicates or even prevents their deployment.Based on our findings, we propose a clustering system architecture that not only includes wireless information, as done in the state of the art, but also combines wireless and backhaul network feasibility information in a smart way. This avoids unnecessary signaling and User Equipment (UE) data exchange among BSs which are not eligible to take part in the cooperative cluster. Evaluations show that our scheme reduces the signaling and UE data exchange overhead by up to 85% compared to conventional clustering approaches, which do not take into account the backhaul network’s status.

Clustering Algorithm to Reduce Power Consumptions for Wireless Sensor Networks

A sensor network has many sensor nodes with limited energy. One of the important issues in these networks is the increase of the life time of the network. In this article, a clustering algorithm is introduced for wireless sensor networks that considering the parameters of distance and remaining energy of each node in the process of cluster head selection. The introduced algorithm is able to reduce the amount of consumed energy in the network. In this algorithm, the nodes that have more energy and less distance from the base station more probably will become cluster heads. Also, we use algorithm for finding the shortest path between cluster heads and base station. The results of simulation with the help of Matlab software show that the proposed algorithm increase the life time of the network compared with LEACH algorithm.

Maximizing Network Lifetime through VaryingTransmission Radii with Energy Efficient Cluster RoutingAlgorithm in Wireless Sensor Networks

One of the major issues in wireless sensor network is developing an energy-efficient routing protocol. LEACH is very effective in enhancing lifetime of the nodes from routing aspect. This paper proposes the scheduling of energy efficient cluster nodes close to the base station called EECL algorithm. Both LEACH and EECL algorithms have been varied with different transmission radii and compared for the improvement of network lifetime. Simulation results show that there has been significant improvement in energy conservation of wireless sensor networks with EECL. randomized rotation of local cluster base stations evenly distribute the energy load among the sensors in the network. It uses localized coordination to enable scalability and robustness for dynamic networks and incorporates data fusion into the routing protocol to reduce the amount of information that must be transmitted to the base station. In this paper, an improved LEACH protocol for data gathering and aggregation is proposed. Such innovation can extend the lifetime of the whole network due to much less energy dissipation for data transmission to base station (2).

A Novel Quality of Service Routing Algorithm for Wireless Sensor Networks

A new routing algorithm, RABA, is proposed in this paper. It seeks the shortest path between cluster head and Base Station by Ant Colony Optimization (ACO). The cluster head far away from Base Station transmits message along the shortest path, therefore reducing the transmission path length and lowering the node energy consumption. The simulation compared with LEACH shows that this algorithm can reduce routing length effectively and prolong network lifetime, providing more high quality of service.

Mortality by neoplasia and cellular telephone base stations in the Belo Horizonte municipality, Minas Gerais state, Brazil

Pollution caused by the electromagnetic fields (EMFs) of radio frequencies (RF) generated by the telecommunication system is one of the greatest environmental problems of the twentieth century. The purpose of this research was to verify the existence of a spatial correlation between base station (BS) clusters and cases of deaths by neoplasia in the Belo Horizonte municipality, Minas Gerais state, Brazil, from 1996 to 2006 and to measure the human exposure levels to EMF where there is a major concentration of cellular telephone transmitter antennas. A descriptive spatial analysis of the BSs and the cases of death by neoplasia identified in the municipality was performed through an ecological–epidemiological approach, using georeferencing. The database employed in the survey was composed of three data banks: 1. death by neoplasia documented by the Health Municipal Department; 2. BSs documented in ANATEL (“Agência Nacional de Telecomunicações”: ‘Telecommunications National Agency’); and 3. census and demographic city population data obtained from official archives provided by IBGE (“Instituto Brasileiro de Geografia e Estatística”: ‘Brazilian Institute of Geography and Statistics’). The results show that approximately 856 BSs were installed through December 2006. Most (39.60%) of the BSs were located in the “Centro-Sul” (‘Central-Southern’) region of the municipality. Between 1996 and 2006, 7191 deaths by neoplasia occurred and within an area of 500 m from the BS, the mortality rate was 34.76 per 10,000 inhabitants. Outside of this area, a decrease in the number of deaths by neoplasia occurred . The greatest accumulated incidence was 5.83 per 1000 in the Central-Southern region and the lowest incidence was 2.05 per 1000 in the Barreiro region. During the environmental monitoring, the largest accumulated electric field measured was 12.4 V/m and the smallest was 0.4 V/m. The largest density power was 40.78 μW/cm 2, and the smallest was 0.04 μW/cm 2.

Free probability based capacity calculation of multiantenna Gaussian fading channels with cochannel interference

During the last decade, it has been well understood that communication over multiple antennas can increase linearly the multiplexing capacity gain and provide large spectral efficiency improvements. However, the majority of studies in this area were carried out ignoring cochannel interference. Only a small number of investigations have considered cochannel interference, but even therein simple channel models were employed, assuming identically distributed fading coefficients. In this paper, a generic model for a multiantenna channel is presented incorporating four impairments, namely additive white Gaussian noise, flat fading, path loss and cochannel interference. Both point-to-point and multiple-access MIMO channels are considered, including the case of cooperating Base Station clusters. The asymptotic capacity limit of this channel is calculated based on an asymptotic free probability approach which exploits the additive and multiplicative free convolution in the R - and S -transform domains, respectively, as well as properties of the η and Stieltjes transform. Numerical results are utilized to verify the accuracy of the derived closed-form expressions and evaluate the effect of the cochannel interference.

An Multi-hop Cluster Based Routing Protocol for Wireless Sensor Networks

Clustering routing protocol provides an effective method for prolonging the lifetime of a wireless sensor network. But most of the researches care less about the communication between Cluster Head (CH) nodes and Base Station (BS). This paper proposed a Multi-hop Cluster based Routing Protocol for long range transmission in wireless sensor network. The protocol consists of two parts, one is with respect to cluster management in sensor area, and the other is about the data transmission between base station and the sensor area. Simulation results show that the protocol offers a better performance than single-hop clustering routing protocols in terms of network lifetime and energy consumption when the base station is located far away from the sensing area.

Session details: Special issue on the 2010 GreenMetrics workshop

Session details: Special issue on the 2010 GreenMetrics workshop

Optimal Base Station Clustering for a Mobile Communication Network Design

This paper considers an optimal base station clustering problem for designing a mobile (wireless) communication network. For a given network with a set of nodes (base stations), the problem is to optimally partition the set of nodes into subsets (each called a cluster) such that the associated inter-cluster traffic is minimized under certain topological constraints and cluster capacity constraints. In the problem analysis, the problem is formulated as an integer programming problem. The integer programming problem is then transformed into a binary integer programming problem, for which the associated linear programming relaxation is solved in a column generation approach assisted by a branch-and-bound procedure. For the column generation, both a heuristic algorithm and a valid inequality approach are exploited. Various numerical examples are solved to evaluate the effectiveness of the LP (Linear Programming) based branch-and-bound algorithm.

A Decentralized Clustering Scheme for Dynamic Downlink Base Station Cooperation

Base station (BS) cooperation is a promising technique to suppress co-channel interference for cellular networks. However, practical limitations constrain the scale of cooperation, thus the network is divided into small disjoint BS cooperation groups, namely clusters. A decentralized scheme for BS cluster formation is proposed based on efficient BS negotiations, of which the feedback overhead per user is nearly irrelevant to the network size, and the number of iteration rounds scales very slowly with the network size. Simulations show that our decentralized scheme provides significant sum-rate gain over static clustering and performs almost the same as the existing centralized approach. The proposed scheme is well suited for large-scale cellular networks due to its low overhead and complexity.

Wireless network capacity management: A real options approach

This paper applies financial option valuation methods to new wireless network capacity investment decision timing. In particular, we consider the case of network capacity for cellular telephone service. Given a cluster of base stations (with a certain traffic capacity per base station), we determine when it is optimal to increase capacity for each of the base stations contained in the cluster. We express this in terms of the fraction of total cluster capacity in use, i.e. we calculate the optimal time to upgrade in terms of the ratio of observed usage to existing capacity. We study the optimal decision problem of adding new capacity in the presence of stochastic wireless demand for services. A four factor algorithm is developed, based on a real options formulation. Numerical examples are provided to illustrate various aspects of the model.