This thesis deals with the design of efficient transmission schemes forwireless interference networks, when certain channel state information(CSI) is available at the terminals.In wireless interference networks multiple source-destination pairsshare the same transmission medium for the communications. The signalreception at each destination is affected by the interference from unintendedsources. This may lead to a competitive situation that each sourcetries to compensate the negative effect of interference at its desired destinationby increasing its transmission power, while it in fact increasesthe interference to the other destinations. Ignoring this dependency maycause a significant waste of available radio resource. Since the transmissiondesign for each user is interrelated to the other users’ strategies, anefficient radio resource allocation should be jointly performed consideringall the source-destination pairs. This may require a certain amount ofCSI to be exchanged, e.g. through feedback channels, among differentterminals. In this thesis, we investigate such joint transmission designand resource allocation in wireless interference networks.We first consider the smallest interference network with two sourcedestinationpairs. Each source intends to communicate with its dedicateddestination with a fixed transmission rate. All terminals have the perfectglobal CSI. The power control seeks feasible solutions that properly assigntransmission power to each source in order to guarantee the successfulcommunications of both source-destination pairs. To avoid interference,the transmissions of the two sources can be orthogonalized. They canalso be activated non-orthogonally. In this case, each destination maydirectly decode its desired signals by treating the interference signals asnoise. It may also perform decoding of its desired signals after decodingand subtracting the interference signals sent from the unintendedsources. The non-orthogonal transmission can more efficiently utilize the  available channel such that the power control problem has solutions withsmaller transmission power in comparison with the orthogonal transmission.However, due to the randomness of fading effects, feasible powercontrol solutions may not always exist. We quantify the probability thatthe power control problem has feasible solutions, under a Rayleigh fadingenvironment. A hybrid transmission strategy that combines the orthogonaland non-orthogonal transmissions is then employed to use the smallesttransmission power to guarantee the communications in the consideredtwo-user interference network.The network model is further extended to the general K-user interferencenetwork, which is far more complicated than the two-user case. Thecommunication is conducted in a time-varying fading environment. Thefeedback channel’s capacity is limited so that each terminal can obtainonly quantized global CSI. Conventional interference management techniquestend to orthogonalize the transmissions of the sources. However,we permit them to transmit non-orthogonally and apply an interferencealignment scheme to tackle inter-user interference. Ideally, the interferencealignment concept coordinates the transmissions of the sources insuch a way that at each destination the interference signals from differentunintended sources are aligned together in the same sub-space which isdistinguishable from the sub-space for its desired signals. Hence, eachdestination can cancel the interference signals before performing decoding.Nevertheless, due to the imperfect channel knowledge, the interferencecannot be completely eliminated and thus causes difficulties to theinformation recovery process. We study efficient resource allocation intwo different classes of systems. In the first class, each source desires tosend information to its destination with a fixed data rate. The powercontrol problem tends to find the smallest transmission powers to guaranteesuccessful communications between all the source-destination pairs.In another class of systems where the transmission power of each sourceis fixed, a rate adaptation problem seeks the maximum sum throughputthat the network can support. In both cases, the combination of interferencealignment and efficient resource allocation provides substantialperformance enhancement over the conventional orthogonal transmissionscheme.When the fading environment is time-invariant, interference alignmentcan still be realized if each terminal is equipped with multiple antennas.With perfect global CSI at all terminals, the interference signalscan be aligned in the spatial dimension. If each terminal has only localCSI, which refers to the knowledge of channels directly related to  the terminal itself, an iterative algorithm can be applied to calculate thenecessary transmitter-side beamformers and receiver-side filters to properlyalign and cancel interference, respectively. Again, due to the lack ofperfect global CSI, it is difficult to completely eliminate the interferenceat each destination. We study the power control problem in this caseto calculate the minimum required power that guarantees each source tosuccessfully communicate with its destination with a fixed transmissionrate. In particular, since only local CSI is available at each terminal, wepropose an iterative algorithm that solves the joint power control andinterference alignment design in a distributed fashion. Our results showthat a substantial performance gain in terms of required transmissionpower over the orthogonalizing the transmissions of different sources canbe obtained. / <p>QC 20120912</p>

Cooperative transmission involves the simultaneous transmission by a group of devices, alldevices sending the same data. The devices may use sidelink (SL) to share data prior to thejoint transmission. Cooperative transmission helps improve network coverage since it can usethe combined transmission power of all devices in a group, whereas single-hop transmissionby one device is limited to its own maximum uplink power. Cooperative transmission aim is toimprove the network coverage of devices involved. The cooperative transmission solutioncomprisestwo steps. The first step is when a device (source device) in the group wants to senddata in the UL and then transmits data via SL to the devices in a created group. In the secondstep, all users simultaneously transmit the data in the UL to the base station the group isassigned to.This master thesis studies both the performance in the uplink (UL), comparing cooperativewith direct transmission, and how to reduce the power consumption of the devices involvedin the cooperative transmission.A power consumption model was developed to analyze the energy consumption, both viaanalytical and simulations methods. The analytical results show that cooperative transmissioncan reduce energy consumption by 7% compared to direct transmission. An algorithm wasproposed for cooperative transmission, which helps reduce energy consumption by 31%.Furthermore, the performance of cooperative transmissions was also studied using a systemsimulator. The results shows that the UL total bit rate increases with cooperative transmissionand is proportional to the number of users in the group. The total bit rate increased by 57%for a group with five users and for a group of 10 the increase was 107% (with a carrierfrequency of 3GHz). Different scenarios were simulated, and the increase in total bit ratevaries from 50-150%. Cooperative transmission involves the simultaneous transmission by a group of devices, alldevices sending the same data. The devices may use sidelink (SL) to share data prior to thejoint transmission. Cooperative transmission helps improve network coverage since it can usethe combined transmission power of all devices in a group, whereas single-hop transmissionby one device is limited to its own maximum uplink power. Cooperative transmission aim is toimprove the network coverage of devices involved. The cooperative transmission solutioncomprisestwo steps. The first step is when a device (source device) in the group wants to senddata in the UL and then transmits data via SL to the devices in a created group. In the secondstep, all users simultaneously transmit the data in the UL to the base station the group isassigned to.This master thesis studies both the performance in the uplink (UL), comparing cooperativewith direct transmission, and how to reduce the power consumption of the devices involvedin the cooperative transmission.A power consumption model was developed to analyze the energy consumption, both viaanalytical and simulations methods. The analytical results show that cooperative transmissioncan reduce energy consumption by 7% compared to direct transmission. An algorithm wasproposed for cooperative transmission, which helps reduce energy consumption by 31%.Furthermore, the performance of cooperative transmissions was also studied using a systemsimulator. The results shows that the UL total bit rate increases with cooperative transmissionand is proportional to the number of users in the group. The total bit rate increased by 57%for a group with five users and for a group of 10 the increase was 107% (with a carrierfrequency of 3GHz). Different scenarios were simulated, and the increase in total bit ratevaries from 50-150%.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

The rapid growth in demand for cellular mobile communications and emerging fixed wireless access has created the need to increase system capacity through more efficient utilization of the frequency spectrum, and the need for better grade of service. In cellular systems, capacity improvement can be achieved by reducing co-channel interference. Several techniques have been proposed in literature for mitigating co-channel interference, such as adaptive antennas and power control. Also, by allocating transmitter power and communication channels efficiently (resource allocation), overall co-channel interference can be maintained below a desired maximum tolerable level, while maximizing the carried traffic of the system. This dissertation presents investigation results on the performance of base station adaptive antennas, power control and channel allocation, as techniques for capacity improvement. Several approaches are analyzed. Firstly, we study the combined use of adaptive antennas and fractional loading factor, in order to estimate the potential capacity improvement achieved by adaptive antennas. Next, an extensive simulation analysis of a cellular network is carried out aiming to investigate the complex interrelationship between power control, channel allocation and adaptive antennas. In the first part of this simulation analysis, the combined use of adaptive antennas, power control and reduced cluster size is analyzed in a cellular system using fixed channel allocation. In the second part, we analyze the benefits of combining adaptive antennas, dynamic channel allocation and power control. Two representative channel allocation algorithms are considered and analyzed regarding how efficiently they transform reduced co-channel interference into higher carried traffic. Finally, the spatial filtering capability of adaptive antennas is used to allow several users to share the same channel within the same cell. Several allocation algorithms combined with power control are analyzed. / Ph. D.

Wireless ad-hoc networks are easily deployed, untethered to infrastructure, and have virtually an unlimited number of applications. However, this flexibility comes at the cost of finite and often unreplenishable power supplies. Once a node has consumed all of its power, it can no longer receive, transmit, gather information, or otherwise participate in the network. Therefore, reducing the amount of energy necessary for node communication has been an area of intense research. Previous work has investigated the use of directional antennas as a method to reduce inter-node power requirements. However, most proposed methods ignore inter-session interference, propose heuristic solution methods, and ignore the use of directional antennas for signal reception. We develop a flexible mixed-integer linear program (MILP) designed to optimize max-min multicast path lifetime for directional antenna equipped networks in the presence of interference. The MILP is utilized to perform a comparison directional antenna use for signal transmission and reception. Results indicate that directional reception is slightly superior to transmission for the defined max-min lifetime metric, and vastly superior when considering cumulative power use. We further analyze the performance of interference-ignorant link-based heuristics designed for both directional transmission and directional reception as they perform in our more realistic model. Our results show that interference-ignorant methods cannot find feasible solutions unless all nodes are equipped with high gain, high efficiency directional antennas. Even in these cases, directional reception outperforms directional transmission. Because of the superiority of directional reception, we focus our attention on this method. A heterogeneity study is performed, and two heuristic methods for approximating the MILP optima are developed. We find that even under heterogeneous conditions, directional reception can increase network lifetime. Finally, a genetic algorithm (GA) and semi-distributed heuristic method are developed as alternatives to the MILP. Results show that the GA often can find solutions with lifetimes 85% as long as the optimal. Our semi-distributed heuristic, designed to be even more computationally simple than the GA, and to serve as a basis for a distributed protocol, is almost as effective as the GA as approximating optimal solutions. We conclude that directional reception is the superior method of antenna use for extending max-min multicast tree lifetime, that it works well in heterogeneous conditions, and lends itself well to heuristic design. / Ph. D.