394 research outputs found
Green Cellular Networks: A Survey, Some Research Issues and Challenges
Energy efficiency in cellular networks is a growing concern for cellular
operators to not only maintain profitability, but also to reduce the overall
environment effects. This emerging trend of achieving energy efficiency in
cellular networks is motivating the standardization authorities and network
operators to continuously explore future technologies in order to bring
improvements in the entire network infrastructure. In this article, we present
a brief survey of methods to improve the power efficiency of cellular networks,
explore some research issues and challenges and suggest some techniques to
enable an energy efficient or "green" cellular network. Since base stations
consume a maximum portion of the total energy used in a cellular system, we
will first provide a comprehensive survey on techniques to obtain energy
savings in base stations. Next, we discuss how heterogeneous network deployment
based on micro, pico and femto-cells can be used to achieve this goal. Since
cognitive radio and cooperative relaying are undisputed future technologies in
this regard, we propose a research vision to make these technologies more
energy efficient. Lastly, we explore some broader perspectives in realizing a
"green" cellular network technologyComment: 16 pages, 5 figures, 2 table
Impact of User Distribution on Optical Wireless Systems
In this paper, we investigate the impact of user distribution on resource allocation in visible light communication (VLC) systems, using a wavelength division multiple access (WDMA) scheme. Two different room layouts are examined in this study. Three 10-user scenarios are considered, while an optical angle diversity receiver (ADR) with four faces is used. A mixed-integer linear programming (MILP) model is utilized to identify the optimum wavelengths and access point (AP) allocation in each scenario. The results show that a change in user distribution can affect the level of channel bandwidth and SINR. However, a uniform distribution of users in the room can provide a higher channel bandwidth as well as high SINR above the threshold (15.6 dB) for all users compared to clustered users, which is a scenario that has the lowest SINR with supported data rate above 3.2 Gbps
Cooperative Communications with Partial Channel State Information in Mobile Radio Systems
Future 4G mobile radio cellular networks are considered OFDM-MIMO systems. Cooperative communication based on coordinated base stations is a very promising concept to perform inter-cell interference management. This thesis deals with the concept of cooperative communication from its information-theoretic background to its practical system design. The main focus is a practical design of the joint detection scheme in the uplink and the joint transmission scheme in the downlink with partial channel-state information (CSI), i.e., significant CSI and imperfect CSI.Zukünftige zellulare 4G-Mobilfunksysteme können als OFDM-MIMO-Systeme betrachtet werden. In solchen zukünftigen Mobilfunksystemen ist kooperative Kommunikation, basierend auf koordinierten Basisstationen, ein sehr vielversprechendes Konzept zum Interzellinterferenzmanagement. Die vorliegende Arbeit behandelt das Konzept der kooperativen Kommunikation vom informationstheoretischen Hintergrund bis hin zum praktischen Systemdesign. Der Schwerpunkt der vorliegenden Arbeit liegt auf dem praktischen Design kooperativer Kommunikationssysteme mit partieller Kanalkenntnis
Topology and interference analysis in macrocellular environment
In the present day, mobile based data services have become increasingly popular among end users and businesses and thus considered as one of the important issues in the telecommunication network, because of its high demand. The telecommunication industry is continuously striving to fulfil this demand in a cost-efficient manner. Fundamentally, the performance of a mobile communication network is constrained by the propagation environment and technical capabilities of the network equipment. The target of radio network engineers is to design and deploy a mobile network that provides effective coverage and capacity solution with a profitable implementation cost. In order to reach this target, careful examination of radio network planning and choosing the right tools are the key methods. Network densification is considered as a feasible evolutionary pathway to fulfil the exponentially increasing data capacity demand in mobile networks.
The objective of this thesis work is to study and analyse the densification of classical macrocellular network, which is still the dominant form of deployment worldwide. The analysis is based on deep ray-tracing based propagation simulations in the outdoor and indoor environment, and considers two key performance metrics; cell spectral efficiency and area spectral efficiency. For analysing the impact of network densification, different cell densities, obtained from varying the inter-site distances are considered. Furthermore, the network is assumed to be operating in a full load condition; an extreme condition in which the base stations are transmitting at full power. From the simulations, it has been illustrated that as a result of densifying the network, the inter-cell interference increases, which reduce the achievable cell spectral efficiency. The system capacity, on the other hand, is shown to improve due to the increase in the area spectral efficiency, as a result of high-frequency re-use, in the outdoor settings. Nevertheless, it is observed that the densification of macrocellular network experience inefficiency in the indoor environment; mainly arising from coverage limitation due to extreme antenna tilt angles. This calls for sophisticated methods such as base station coordination or inter-cell interference cancellation technique to be employed for future cellular network. For fulfilling the indoor capacity demand in a cost-efficient manner, the operators will be required to deploy dedicated indoor small cells based solutions
Aspects of capacity enhancement techniques in cellular networks
Frequency spectrum is the scarce resource. From mobile operator’s point of view, efficient utilization of the radio resources is needed while providing maximum coverage, and ensuring good quality of service with minimal infrastructure. In high capacity demanding areas, multilayer networks with multiband and multi radio access technologies are deployed, in order to meet the capacity requirements. In his doctoral thesis, Usman Sheikh has proposed a “Smart Traffic Handling” strategy, which is based on user’s required service type and location. Smart traffic handling scheme efficiently utilizes the different layers of the network, balances the load among them, and improves the system capacity. Power resources at base station are also limited. Usman Sheikh’s proposed “Power Control Scheme for High Speed Downlink Packet Access (HSDPA) network” improves the cell edge user experience, while maintaining the fairness among the other users in a cell. With the help of a proposed power control scheme, a user far from the base station can also enjoy the better quality of service.
Generally, mobile operators use macro cells with wide beam antennas for wider coverage in the cell, but future capacity demands cannot be achieved by using only them. “Higher Order Sectorization” is one possible way to increase the system capacity. Usman Sheikh proposed new network layouts called “Snowflake” and “Flower” tessellations, for 6-sector and 12-sector sites, respectively. These tessellations can be used as a basis for making a nominal network plan for sites with higher order sectorization. These tessellations would be helpful for simulation purposes. Through his work, he has also tried to highlight the importance of deploying “Adaptive MIMO Switching” in Long Term Evolution (LTE) system, the fourth generation of wireless networks.
In future, the fifth generation of wireless networks is expected to offer thousand times more capacity compared to LTE. The novel concept of “Single Path Multiple Access (SPMA)” given by Usman Sheikh is a revolutionary idea, and gives a possibility to increase the system capacity by a giant margin. SPMA can be considered as a right step towards 5G technology.
Usman Sheikh’s work is of high importance not only from mobile operator’s point of view; rather his contributions to the scientific community will also lead to better user (customer) experience. His work will definitely benefit the mankind in utilizing the limited resources in an optimum and efficient way
An intelligent-agent approach for managing congestion in W-CDMA networks
PhDResource Management is a crucial aspect in the next generation cellular networks
since the use of W-CDMA technology gives an inherent flexibility in managing the
system capacity. The concept of a “Service Level Agreement” (SLA) also plays a
very important role as it is the means to guarantee the quality of service provided to
the customers in response to the level of service to which they have subscribed.
Hence there is a need to introduce effective SLA-based policies as part of the radio
resource management.
This work proposes the application of intelligent agents in SLA-based control in
resource management, especially when congestion occurs. The work demonstrates the
ability of intelligent agents in improving and maintaining the quality of service to
meet the required SLA as the congestion occurs.
A particularly novel aspect of this work is the use of learning (here Case Based
Reasoning) to predict the control strategies to be imposed. As the system environment
changes, the most suitable policy will be implemented. When congestion occurs, the
system either proposes the solution by recalling from experience (if the event is
similar to what has been previously solved) or recalculates the solution from its
knowledge (if the event is new). With this approach, the system performance will be
monitored at all times and a suitable policy can be immediately applied as the system
environment changes, resulting in maintaining the system quality of service
Adaptive code division multiple access protocol for wireless network-on-chip architectures
Massive levels of integration following Moore\u27s Law ushered in a paradigm shift in the way on-chip interconnections were designed. With higher and higher number of cores on the same die traditional bus based interconnections are no longer a scalable communication infrastructure. On-chip networks were proposed enabled a scalable plug-and-play mechanism for interconnecting hundreds of cores on the same chip. Wired interconnects between the cores in a traditional Network-on-Chip (NoC) system, becomes a bottleneck with increase in the number of cores thereby increasing the latency and energy to transmit signals over them. Hence, there has been many alternative emerging interconnect technologies proposed, namely, 3D, photonic and multi-band RF interconnects. Although they provide better connectivity, higher speed and higher bandwidth compared to wired interconnects; they also face challenges with heat dissipation and manufacturing difficulties. On-chip wireless interconnects is one other alternative proposed which doesn\u27t need physical interconnection layout as data travels over the wireless medium. They are integrated into a hybrid NOC architecture consisting of both wired and wireless links, which provides higher bandwidth, lower latency, lesser area overhead and reduced energy dissipation in communication. However, as the bandwidth of the wireless channels is limited, an efficient media access control (MAC) scheme is required to enhance the utilization of the available bandwidth. This thesis proposes using a multiple access mechanism such as Code Division Multiple Access (CDMA) to enable multiple transmitter-receiver pairs to send data over the wireless channel simultaneously. It will be shown that such a hybrid wireless NoC with an efficient CDMA based MAC protocol can significantly increase the performance of the system while lowering the energy dissipation in data transfer. In this work it is shown that the wireless NoC with the proposed CDMA based MAC protocol outperformed the wired counterparts and several other wireless architectures proposed in literature in terms of bandwidth and packet energy dissipation. Significant gains were observed in packet energy dissipation and bandwidth even with scaling the system to higher number of cores. Non-uniform traffic simulations showed that the proposed CDMA-WiNoC was consistent in bandwidth across all traffic patterns. It is also shown that the CDMA based MAC scheme does not introduce additional reliability concerns in data transfer over the on-chip wireless interconnects
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