Interference-aware Resource Allocation in High-density WLANs - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Interference-aware Resource Allocation in High-density WLANs write by Xiaowei Wang. This book was released on 2016. Interference-aware Resource Allocation in High-density WLANs available in PDF, EPUB and Kindle. "IEEE 802.11 wireless local area networks (WLANs) become more and more popular and widely deployed in public hotspots, enterprise environments, and residential areas to provide seamless coverage and improve user connectivity. However, the high density of Access Points (APs) and the stations (STAs) associated to each AP results in increased intra-cell and inter-cell interference, which can cause high collision rates, long backoff intervals, and degraded received signal-to-interference-plus-noise ratio (SINR). To manage such interference, it is required to explore medium access control (MAC) enhancement, efficient channel assignment, and load balancing techniques, which can improve the performance experienced by users. In this work, we develop and evaluate interference-aware enhanced MAC and radio resource allocation algorithms in 802.11 WLANs, aiming to increase the network throughput. To improve the achievable throughput in a single-cell WLAN, a channel-aware adaptive carrier sensing multiple access with collision avoidance (CSMA/CA) scheme is developed to take advantage of multi-user diversity, while supporting distributed and asynchronous operation. By dynamically adjusting the contention window of each STA according to its channel state, this approach prioritizes STAs who gain most from using a channel and enhances channel utilization. A three-dimensional Markov chain is developed to model and evaluate the proposed adaptive CSMA/CA, which significantly improves throughput, especially in a large network.To manage the inter-cell interference in a multi-cell WLAN, the channel assignment and AP-STA association are investigated. Applying difference-of-convex-functions (DC) programming, two different optimization problems are solved aiming to minimize interference sum utility and maximize STA throughput. Distributed schemes are also developed in which APs and STAs can self-configure channel selection and association to mitigate the interference and thereby improve the network throughput. It is shown that the proposed approaches are highly efficient and robust with fast convergence and low complexity.To balance the load and provide service customization in a multi-cell WLAN, AP-STA association and airtime control are studied in a virtualized network, where physical APs are shared by multiple Internet service providers (ISPs). More specifically, an optimization problem is formulated on the STAs' transmission probabilities to maximize the overall network throughput, while providing airtime usage guarantees for the ISPs. The algorithm to reach the optimal transmission probability and detailed implementation are also discussed. Illustrative results confirm the superior and robust performance of the developed association and airtime control scheme." --
Interference-aware Resource Management in Multihop Wireless Networks
Interference-aware Resource Management in Multihop Wireless Networks - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Interference-aware Resource Management in Multihop Wireless Networks write by Azin Neishaboori. This book was released on 2008. Interference-aware Resource Management in Multihop Wireless Networks available in PDF, EPUB and Kindle.
Source and Channel Aware Resource Allocation for Wireless Networks
Source and Channel Aware Resource Allocation for Wireless Networks - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Source and Channel Aware Resource Allocation for Wireless Networks write by Jubin Jose. This book was released on 2011. Source and Channel Aware Resource Allocation for Wireless Networks available in PDF, EPUB and Kindle. Wireless networks promise ubiquitous communication, and thus facilitate an array of applications that positively impact human life. At a fundamental level, these networks deal with compression and transmission of sources over channels. Thus, accomplishing this task efficiently is the primary challenge shared by these applications. In practice, sources include data and video while channels include interference and relay networks. Hence, effective source and channel aware resource allocation for these scenarios would result in a comprehensive solution applicable to real-world networks. This dissertation studies the problem of source and channel aware resource allocation in certain scenarios. A framework for network resource allocation that stems from rate-distortion theory is presented. Then, an optimal decomposition into an application-layer compression control, a transport-layer congestion control and a network-layer scheduling is obtained. After deducing insights into compression and congestion control, the scheduling problem is explored in two cross-layer scenarios. First, appropriate queue architecture for cooperative relay networks is presented, and throughput-optimality of network algorithms that do not assume channel-fading and input-queue distributions are established. Second, decentralized algorithms that perform rate allocation, which achieve the same overall throughput region as optimal centralized algorithms, are derived. In network optimization, an underlying throughput region is assumed. Hence, improving this throughput region is the next logical step. This dissertation addresses this problem in the context of three significant classes of interference networks. First, degraded networks that capture highly correlated channels are explored, and the exact sum capacity of these networks is established. Next, multiple antenna networks in the presence of channel uncertainty are considered. For these networks, robust optimization problems that result from linear precoding are investigated, and efficient iterative algorithms are derived. Last, multi-cell time-division-duplex systems are studied in the context of corrupted channel estimates, and an efficient linear precoding to manage interference is developed.
Resource Allocation in Relay Enhanced Broadband Wireless Access Networks
Resource Allocation in Relay Enhanced Broadband Wireless Access Networks - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Resource Allocation in Relay Enhanced Broadband Wireless Access Networks write by Preetha Thulasiraman. This book was released on 2010. Resource Allocation in Relay Enhanced Broadband Wireless Access Networks available in PDF, EPUB and Kindle. The use of relay nodes to improve the performance of broadband wireless access (BWA) networks has been the subject of intense research activities in recent years. Relay enhanced BWA networks are anticipated to support multimedia traffic (i.e., voice, video, and data traffic). In order to guarantee service to network users, efficient resource distribution is imperative. Wireless multihop networks are characterized by two inherent dynamic characteristics: 1) the existence of wireless interference and 2) mobility of user nodes. Both mobility and interference greatly influence the ability of users to obtain the necessary resources for service. In this dissertation we conduct a comprehensive research study on the topic of resource allocation in the presence of interference and mobility. Specifically, this dissertation investigates the impact interference and mobility have on various aspects of resource allocation, ranging from fairness to spectrum utilization. We study four important resource allocation algorithms for relay enhanced BWA networks. The problems and our research achievements are briefly outlined as follows. First, we propose an interference aware rate adaptive subcarrier and power allocation algorithm using maximum multicommodity flow optimization. We consider the impact of the wireless interference constraints using Signal to Interference Noise Ratio (SINR). We exploit spatial reuse to allocate subcarriers in the network and show that an intelligent reuse of resources can improve throughput while mitigating the impact of interference. We provide a sub-optimal heuristic to solve the rate adaptive resource allocation problem. We demonstrate that aggressive spatial reuse and fine tuned-interference modeling garner advantages in terms of throughput, end-to-end delay and power distribution. Second, we investigate the benefits of decoupled optimization of interference aware routing and scheduling using SINR and spatial reuse to improve the overall achievable throughput. We model the routing optimization problem as a linear program using maximum concurrent flows. We develop an optimization formulation to schedule the link traffic such that interference is mitigated and time slots are reused appropriately based on spatial TDMA (STDMA). The scheduling problem is shown to be NP-hard and is solved using the column generation technique. We compare our formulations to conventional counterparts in the literature and show that our approach guarantees higher throughput by mitigating the effect of interference effectively. Third, we investigate the problem of multipath flow routing and fair bandwidth allocation under interference constraints for multihop wireless networks. We first develop a novel isotonic routing metric, RI3M, considering the influence of interflow and intraflow interference. Second, in order to ensure QoS, an interference-aware max-min fair bandwidth allocation algorithm, LMX:M3F, is proposed where the lexicographically largest bandwidth allocation vector is found among all optimal allocation vectors while considering constraints of interference on the flows. We compare with various interference based routing metrics and interference aware bandwidth allocation algorithms established in the literature to show that RI3M and LMX:M3F succeed in improving network performance in terms of delay, packet loss ratio and bandwidth usage. Lastly, we develop a user mobility prediction model using the Hidden Markov Model(HMM) in which prediction control is transferred to the various fixed relay nodes in the network. Given the HMM prediction model, we develop a routing protocol which uses the location information of the mobile user to determine the interference level on links in its surrounding neighborhood. We use SINR as the routing metric to calculate the interference on a specific link (link cost). We minimize the total cost of routing as a cost function of SINR while guaranteeing that the load on each link does not exceed its capacity. The routing protocol is formulated and solved as a minimum cost flow optimization problem. We compare our SINR based routing algorithm with conventional counterparts in the literature and show that our algorithm reinforces routing paths with high link quality and low latency, therefore improving overall system throughput. The research solutions obtained in this dissertation improve the service reliability and QoS assurance of emerging BWA networks.
Channel Aware Scheduling and Resource Allocation with Cross Layer Optimization in Wireless Networks
Channel Aware Scheduling and Resource Allocation with Cross Layer Optimization in Wireless Networks - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Channel Aware Scheduling and Resource Allocation with Cross Layer Optimization in Wireless Networks write by Sheu-Sheu Tan. This book was released on 2013. Channel Aware Scheduling and Resource Allocation with Cross Layer Optimization in Wireless Networks available in PDF, EPUB and Kindle. We develop channel aware scheduling and resource allocation schemes with cross-layer optimization for several problems in multiuser wireless networks. We consider problems of distributed opportunistic scheduling, where multiple users contend to access the same set of channels. Instead of scheduling users to the earliest available idle channels, we also take the instantaneous channel quality into consideration and schedule the users only when the channel quality is sufficiently high. This can lead to significant gains in throughput compared to system where PHY and MAC layers are designed separately and the wireless fading channels are abstracted as time invariant, fixed rate channels for scheduling purposes. We first consider opportunistic spectrum access in a cognitive radio network, where a secondary user (SU) share the spectrum opportunistically with incumbent primary users (PUs). Similar to earlier works on distributed opportunistic scheduling (DOS), we maximize the throughput of SU by formulating the channel access problem as a maximum rate-of-return problem in the optimal stopping theory framework. We show that the optimal channel access strategy is a pure threshold policy, namely the SU decides to use or skip transmission opportunities by comparing the channel qualities to a fixed threshold. We further increase the spectrum utilization by interleaving SU's packets with periodic sensing to detect PU's return. We jointly optimize the rate threshold and the packet transmission time to maximize the average throughput of SU, while limiting interference to PU. Next, we develop channel-aware opportunistic spectrum access strategies in a more general cognitive radio network with multiple SUs. Here, we additionally take into account the collisions and complex interaction between SUs and sharing of resources between them. We derive strategies for both cooperative settings where SUs maximize their sum total of throughputs, as well as non-cooperative game theoretic settings, where each SU tries to maximize its own throughput. We show that the optimal schemes for both scenarios are pure threshold policies. In the non-cooperative case, we establish the existence of Nash equilibrium and develop best response strategies that can converge to equilibria, with SUs relying only on their local observations. We study the trade-off between maximal throughput in the cooperative setting and fairness in the non-cooperative setting, and schemes based on utility functions and pricing that mitigate this tradeoff. In addition to maximizing throughput and fair sharing of resources, it is important to consider network/scheduling delays for QoS performance of delay-sensitive applications. We study DOS under both network-wide and user-specific average delay constraints. We take a stochastic Lagrangian approach and characterize the corresponding optimal scheduling policies accordingly, and show that they have a pure threshold structure. Next, we consider the use of different types of channel quality information, i.e., channel state information (CSI) and channel distribution information (CDI) in the opportunistic scheduling design for MIMO ad hoc networks. CSI is highly dynamic in nature and provides time diversity in the wireless channel, but is difficult to track. CDI offers temporal stability, but is incapable of capturing the instantaneous channel conditions. We design a new class of cross-layer opportunistic channel access scheduling framework for MIMO networks where CDI is used in the network context to group the simultaneous transmission links for spatial channel access and CSI is used in the link context to decide when and which link group should transmit based on a pre designed threshold. We thereby reap the benefits of both the temporal stability of CDI and the time diversity of CSI. Finally, we consider a novel application of cross layer optimization for communication of progressive coded images over OFDM wireless fading channels. We first consider adaptive modulation based on the instantaneous channel state information. An algorithm is proposed to allocate power and constellation size at each subchannel by maximizing the throughput. We next consider both the variance and the average of the throughput when deciding the constellation size for adaptive modulation. Simulation results confirm that cross-layer optimization with adaptive modulation enhances system performance.
