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Search Results: 1 - 10 of 6439 matches for " Naveed Ul Hassan "
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Adaptive Resource Allocation with Strict Delay Constraints in OFDMA System
Naveed Ul Hassan,Mohamad Assaad
EURASIP Journal on Wireless Communications and Networking , 2010, DOI: 10.1155/2010/121080
Adaptive Resource Allocation with Strict Delay Constraints in OFDMA System
Ul Hassan Naveed,Assaad Mohamad
EURASIP Journal on Wireless Communications and Networking , 2010,
Abstract: We consider the adaptive resource allocation problem in downlink Orthogonal Frequency Division Multiple Access (OFDMA) system with strict packet delay constraints in the range of . In this range of delay constraints, resource optimization has to be simultaneously performed over multiple time slots. Thus optimal allocation decisions require future Channel State Information (CSI) and packet arrival rate information. The causal nature of CSI combined with the increase in the number of optimization variables makes it a very challenging problem. We propose a two-step solution by separating scheduling from subcarrier and power allocation. Our proposed causal scheduler ensures delay guarantees by deriving a minimum data rate out of the user queues while minimizing transmit power in every time slot. The output rates are fed to the resource allocation block and the problem is formulated as a convex optimization problem. The subcarrier and power allocation decisions are made in order to satisfy the demanded rates within the peak power constraint. We address the feasibility of the physical layer resource allocation problem and develop efficient algorithms. When the problem is infeasible we devise a strategy which incurs minimum deviation from the proposed rates for maximum number of users. We show by simulations that our proposed scheme can efficiently utilize time variations as well as multiuser diversity in the system.
Electricity Cost Minimization for a Residential Smart Grid with Distributed Generation and Bidirectional Power Transactions
Yi Liu,Naveed Ul Hassan,Shisheng Huang,Chau Yuen
Mathematics , 2012,
Abstract: In this paper, we consider the electricity cost minimization problem in a residential network where each community is equipped with a distributed power generation source and every household in the community has a set of essential and shiftable power demands. We allow bi-directional power transactions and assume a two-tier pricing model for the buying and selling of electricity from the grid. In this situation, in order to reduce the cost of electricity we are required to make, 1) Scheduling decisions for the shiftable demands, 2) The decisions on the amount of energy purchased from the gird by the users, 3) The decisions on the amount of energy sold to the grid by the users. We formulate a global centralized optimization problem and obtain the optimal amount of electricity consumed, sold and purchased for each household, respectively by assuming the availability of all current and future values of time-varying parameters. In reality, the lack of perfect information hampers the implementation of such global centralized optimization. Hence, we propose a distributed online algorithm which only requires the current values of the timevarying supply and demand processes. We then compare and determine the tradeoff between both formulations. Simulation results show that the proposed schemes can provide effective management for household electricity usage.
Demand Shaping to Achieve Steady Electricity Consumption with Load Balancing in a Smart Grid
Naveed Ul Hassan,Xiumin Wang,Shisheng Huang,Chau Yuen
Mathematics , 2012,
Abstract: The purpose of this paper is to study conflicting objectives between the grid operator and consumers in a future smart grid. Traditionally, customers in electricity grids have different demand profiles and it is generally assumed that the grid has to match and satisfy the demand profiles of all its users. However, for system operators and electricity producers, it is usually most desirable, convenient and cost effective to keep electricity production at a constant rate. The temporal variability of electricity demand forces power generators, especially load following and peaking plants to constantly manipulate electricity production away from a steady operating point.
Power Control for Sum Rate Maximization on Interference Channels Under Sum Power Constraint
Naveed Ul Hassan,Chau Yuen,Shayan Saeed,Zhaoyang Zhang
Mathematics , 2014,
Abstract: In this paper, we consider the problem of power control for sum rate maximization on multiple interfering links (TX-RX pairs)under sum power constraint. We consider a single frequency network, where all pairs are operating in same frequency band,thereby creating interference for each other. We study the power allocation problem for sum rate maximization with and without QoS requirements on individual links. When the objective is only sum rate maximization without QoS guarantees, we develop an analytic solution to decide optimal power allocation for two TX-RX pair problem. We also develop a low complexity iterative algorithm for three TX-RX pair problem. For a generic N>3 TX-RX pair problem, we develop two low-complexity sub-optimal power allocation algorithms. The first algorithm is based on the idea of making clusters of two or three TX-RX pairs and then leverage the power allocation results obtained for two and three TX-RX pair problems. The second algorithm is developed by using a high SINR approximation and this algorithm can also be implemented in a distributed manner by individual TXs. We then consider the same problem but with additional QoS guarantees for individual links. We again develop an analytic solution for two TX-RX pair problem, and a distributed algorithm for N>2 TX-RX pairs.
Demand Response Management For Power Throttling Air Conditioning Loads In Residential Smart Grids
Yawar Ismail Khalid,Naveed Ul Hassan,Chau Yuen,Shisheng Huang
Computer Science , 2014,
Abstract: In this paper we develop an algorithm for peak load reduction to reduce the impact of increased air conditioner usage in a residential smart grid community. We develop Demand Response Management (DRM) plans that clearly spell out the maximum duration as well as maximum severity of inconvenience. We model the air conditioner as a power throttling device and for any given DRM plan we study the impact of increasing the number of power states on the resulting peak load reduction. Through simulations, we find out that adding just one additional state to the basic ON/OFF model, which can throttle power to 50% of the rated air conditioner power, can result in significant amount of peak reduction. However, the peak load that can be reduced is diminishing with the increase in number of states. Furthermore, we also observe the impact of inconvenience duration and inconvenience severity in terms of peak load reduction. These observations can serve as useful guidelines for developing appropriate DRM plans.
Customer Engagement Plans for Peak Load Reduction in Residential Smart Grids
Naveed Ul Hassan,Yawar Ismail Khalid,Chau Yuen,Wayes Tushar
Computer Science , 2015,
Abstract: In this paper, we propose and study the effectiveness of customer engagement plans that clearly specify the amount of intervention in customer's load settings by the grid operator for peak load reduction. We suggest two different types of plans, including Constant Deviation Plans (CDPs) and Proportional Deviation Plans (PDPs). We define an adjustable reference temperature for both CDPs and PDPs to limit the output temperature of each thermostat load and to control the number of devices eligible to participate in Demand Response Program (DRP). We model thermostat loads as power throttling devices and design algorithms to evaluate the impact of power throttling states and plan parameters on peak load reduction. Based on the simulation results, we recommend PDPs to the customers of a residential community with variable thermostat set point preferences, while CDPs are suitable for customers with similar thermostat set point preferences. If thermostat loads have multiple power throttling states, customer engagement plans with less temperature deviations from thermostat set points are recommended. Contrary to classical ON/OFF control, higher temperature deviations are required to achieve similar amount of peak load reduction. Several other interesting tradeoffs and useful guidelines for designing mutually beneficial incentives for both the grid operator and customers can also be identified.
Intrauterine Contraceptive Device Migration Presenting as Abdominal Wall Swelling: A Case Report
Imtiaz Wani,Adil Syed,Muddasir Maqbool,Iftikhar Bakshi,Hilal Bhat,Faheem Ul Hassan Andrabi,Naveed Mohsin
Case Reports in Surgery , 2011, DOI: 10.1155/2011/305914
Abstract: A number of complications are reported with the use of intrauterine contraceptive devices. These may pursue asymptomatic course or present as an acute abdomen after migration into peritoneal cavity. The authors here are reporting an abdominal wall swelling caused by transuterine migration of a copper intrauterine contraceptive device in a 28-year-old female. An open approach was used, and impacted foreign body was retrieved.
Impact of Scheduling Flexibility on Demand Profile Flatness and User Inconvenience in Residential Smart Grid System
Naveed Ul Hassan,Muhammad Adeel Pasha,Chau Yuen,Shisheng Huang,Xiumin Wang
Energies , 2013, DOI: 10.3390/en6126608
Abstract: The objective of this paper is to study the impact of scheduling flexibility on both demand profile flatness and user inconvenience in residential smart grid systems. Temporal variations in energy consumption by end users result in peaks and troughs in the aggregated demand profile. In a residential smart grid, some of these peaks and troughs can be eliminated through appropriate load balancing algorithms. However, load balancing requires user participation by allowing the grid to re-schedule some of their loads. In general, more scheduling flexibility can result in more demand profile flatness, however the resulting inconvenience to users would also increase. In this paper, our objective is to help the grid determine an appropriate amount of scheduling flexibility that it should demand from users, based on which, proper incentives can be designed. We consider three different types of scheduling flexibility (delay, advance scheduling and flexible re-scheduling) in flexible loads and develop both optimal and sub-optimal scheduling algorithms. We discuss their implementation in centralized and distributed manners. We also identify the existence of a saturation point. Beyond this saturation point, any increase in scheduling flexibility does not significantly affect the flatness of the demand profile while user inconvenience continues to increase. Moreover, full participation of all the households is not required since increasing user participation only marginally increases demand profile flatness.
Design of A Scalable Hybrid MAC Protocol for Heterogeneous M2M Networks
Yi Liu,Chau Yuen,Xianghui Cao,Naveed Ul Hassan,Jiming Chen
Computer Science , 2014,
Abstract: A robust and resilient Medium Access Control (MAC) protocol is crucial for numerous machine-type devices to concurrently access the channel in a Machine-to-Machine (M2M) network. Simplex (reservation or contention based) MAC protocols are studied in most literatures which may not be able to provide a scalable solution for M2M networks with large number of heterogeneous devices. In this paper, a scalable hybrid MAC protocol, which consists of a contention period and a transmission period, is designed for heterogeneous M2M networks. In this protocol, different devices with pre-set priorities (hierarchical contending probabilities) firstly contend the transmission opportunities following the convention based $p$-persistent CSMA mechanism. Only the successful devices will be assigned a time slot for transmission following the reservation based TDMA mechanism. If the devices failed in contention at previous frame, to ensure the fairness among all devices, their contending priorities will be raised by increasing their contending probabilities at the next frame. To balance the tradeoff between the contention and transmission period in each frame, an optimization problem is formulated to maximize the channel utility by finding the key design parameters: the contention duration, initial contending probability and the incremental indicator. Analytical and simulation results demonstrate the effectiveness of the proposed Hybrid MAC protocol.
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