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Delay analysis and buffer management for random access in cognitive radio networks
, Article 2013 Iran Workshop on Communication and Information Theory ; May , 2013 , Page(s): 1 - 6 ; 9781467350235 (ISBN) ; Majd, S. A ; Pakravan, M. R ; Sharif University of Technology
2013
Abstract
In this paper, we consider a cognitive radio network in which multiple Secondary Users (SUs) contend to access primary network's channels with a random access scheme. Our goal is to analyze SUs' queuing delay performance in terms of mean queue lengths and find a minimum buffer space for which the overflow probability is less than a desired threshold. In general, the considered network can be modeled as a multidimensional Markov chain. However, the enormous state space makes the numerical analysis intractable. Nevertheless, the state space can be reduced to a two-dimensional Markov chain in the symmetric channel condition. By this approach, the optimal contention probability that minimizes...
Design of Adaptive Interleaver in Wireless Communication
, M.Sc. Thesis Sharif University of Technology ; Golestani, Jamaloddin (Supervisor)
Abstract
Generally to deal with errors in communication systems, two methods have been proposed: FEC and ARQ. In FEC, redundancy bits are added to the data that causes detection and correction of certain error patterns. ARQ method is based on retransmission of information if there is an error in the information. Another method, which is called Hybrid-ARQ, is the combination of these two methods; there are two types of TypeI and TypeII for this category. In typeI, number of redundancy bits in consecutive transmissions of one codeword is constant but in typeII, number of redundancy bits of a codeword increases in subsequent retransmissions.
To deal with burst errors, we can use interleaving along...
To deal with burst errors, we can use interleaving along...
Evaluation and Modeling of Queue Length Resulting from Shock Waves in Freeway Work Zone Areas
, M.Sc. Thesis Sharif University of Technology ; Nassiri, Habibollah (Supervisor)
Abstract
Highway work zone is one of the important factors that create long queues and Delays, increase air population, fuel consumption, and road accident. Since in this zones, one and two or sometimes three lanes may be closed, more careful evaluation of the causes of queue formation seems necessary. The purpose of this research was to develop a method to estimate queue length at work zone in rural freeways, based on its traffic flow characteristics. In this study, traffic data from three work zone locations in Karaj-Qazvin freeway was collected. Results of different modeling show that platooning arrival of vehicles at work zone, increase in percentage of heavy vehicles, high variation of speed and...
S-NC: Structure-free network coding-aware routing in wireless sensor networks
, Article MSWiM'12 - Proceedings of the 15th ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems ; 2012 , Pages 403-407 ; 9781450316286 (ISBN) ; Yousefi, H ; Movaghar, A ; Sharif University of Technology
2012
Abstract
Network Coding (NC) is an emerging technique that helps wireless networks to have higher throughput and better energy efficiency. In this paper, a novel network coding-aware routing (S-NC) which uses NC to improve reliability and robustness in unreliable WSNs is proposed. It is based on a structure-free routing algorithm as the underlying routing engine which employs neighbor queue length to increase coding opportunity; while exploiting a spatial coding method to control the amount of redundancy. To the best of our knowledge, this is the first study on the topic of network codingaware routing in Wsns. Simulation results in Tossim demonstrate that S-NC significantly improves the performance...
Adaptive congestion estimation and control in active queue management
, Article International Conference on Control, Automation and Systems, ICCAS 2007, Seoul, 17 October 2007 through 20 October 2007 ; December , 2007 , Pages 2850-2853 ; 8995003871 (ISBN); 9788995003879 (ISBN) ; Haeri, M ; Sharif University of Technology
2007
Abstract
Active Queue Management (AQM) policies provide an early indication of incipient congestion to the source. In this paper, we propose a new AQM policy that predicts the instantaneous queue length at next time instant using adaptive filtering technique. To use the algorithm in fast routers, we reduce its computational complexity using a direct method to compute the manipulating signals. We show that adaptive congestion estimation is able to control the oscillations in the instantaneous queue length. We compare the performance of our method with respect to other well-known AQM methods such as RED and PI which are also simulated by MATLAB. We also compare the computational complexity of these...
A queueing system with inventory and mixed exponentially distributed lead times
, Article International Journal of Advanced Manufacturing Technology ; Volume 53, Issue 9-12 , August , 2011 , Pages 1231-1237 ; 02683768 (ISSN) ; Haji, R ; Hassanzadeh, F ; Sharif University of Technology
2011
Abstract
We consider M/M/1/∞ systems with inventory in which completing each service in the queueing system requires an on-hand inventory. Continuous review (r, Q) policy is considered for the inventory system, and lead times are assumed to be mixed exponentially distributed. During stockout, arriving demands get rejected from the queue and become lost (lost sale situation). We derive stationary distribution of product form of joint queue length and on-hand inventory. The resulting distribution is employed to compute performance measures which can be used to derive the optimal policy. Optimal order size for predetermined reorder policy is initially determined and finally, optimal reorder point and...
Computational complexity reduction of an adaptive congestion control in active queue management
, Article Chinese Control and Decision Conference 2008, CCDC 2008, Yantai, Shandong, 2 July 2008 through 4 July 2008 ; 2008 , Pages 3743-3747 ; 9781424417346 (ISBN) ; Haeri, M ; Sharif University of Technology
2008
Abstract
Active Queue Management (AQM) policies provide an early indication of incipient congestion to the source. In this paper, we propose a new AQM policy that predicts the instantaneous queue length at the next time instant using adaptive filtering technique. To use this algorithm in fast routers, we have reduced its computational complexity. The proposed method uses a simple linear function as adaptive rule. We show that this adaptive congestion control method is able to control the oscillations in the instantaneous queue length. We compare the performance of our method with the other well-known AQM methods such as RED and PI which are also simulated by MATLAB. We also compare the computational...
Traffic flow control using multi-agent reinforcement learning
, Article Journal of Network and Computer Applications ; Volume 207 , 2022 ; 10848045 (ISSN) ; Javadpour, A ; Bolouki, S ; Sangaiah, A. K ; Ja'fari, F ; Pinto, P ; Zhang, W ; Sharif University of Technology
Academic Press
2022
Abstract
One of the technologies based on information technology used today is the VANET network used for inter-road communication. Today, many developed countries use this technology to optimize travel times, queue lengths, number of vehicle stops, and overall traffic network efficiency. In this research, we investigate the critical and necessary factors to increase the quality of VANET networks. This paper focuses on increasing the quality of service using multi-agent learning methods. The innovation of this study is using artificial intelligence to improve the network's quality of service, which uses a mechanism and algorithm to find the optimal behavior of agents in the VANET. The result...