Department of Mathematics

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Author: search.filters.author.Kulshrestha, RakheeEnd date: 2019

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Now showing 1 - 10 of 17
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    Channel Optimization for Wireless Data Broadcast
    (IJCA, 2011) Kulshrestha, Rakhee
    Recently data broadcast has emerged as powerful tool for information dissemination to massive number of clients equipped with portable gadgets. Wireless communication use air as medium for transferring data to exchange information between mobile client and remote server. To enhance communication capacities and avoid information clashing multichannel broadcast is preferred; which partition available air bandwidth in to small bandwidth air channels. In wireless environment plethora of data are transferred through air creating chaos on air channels. Hence broadcast channel is scared resource for wireless communication which greatly concern system performance by affecting data access time. This paper studies process of data scheduling and broadcasting for multichannel environment with optimal use of air channels. Various method of data placement over multichannel are studied and analytical model to find optimal number of air channel is developed. Simulation results of system performance in context of access time are inferred and presented.
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    Reliability Analysis of Redundant Repairable System with Degraded Failure
    (MERC, 2004) Kulshrestha, Rakhee
    This investigation deals with the transient analysis of the machine repair system consisting of M-operating units operating under the care of single repairman. To improve the system reliability/availability, Y warm standby and S cold standby units are provided to replace the failed units. In case when all spares are being used, the failure of units occurs in degraded fashion. In such situation there is a facility of one additional repairman to speed up the repair. The lifetime and repair time of units are exponentially distributed. We use matrix method to solve the governing Chapman-Kolmogorov equations. Expressions for the system reliability, availability, mean time to system failure, etc. are established in terms of transient probability. Computational scheme is discussed to facilitate the numerical results. Sensitivity analysis is also carried out to depict the effect of various parameters on the system reliability.
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    Bilevel control of degraded machining system with warm standbys, setup and vacation
    (Elsevier, 2004-12) Kulshrestha, Rakhee
    In this paper, we study (N, L) switch-over policy for machine repair model with warm standbys and two repairmen. The repairman (R1) turns on for repair only when N-failed units are accumulated and starts repair after a set up time which is assumed to be exponentially distributed. As soon as the system becomes empty, the repairman (R1) leaves for a vacation and returns back when he finds the number of failed units in the system greater than or equal to a threshold value N. Second repairman (R2) turns on when there are L(>N) failed units in the system and goes for a vacation if there are less than L failed units. The life time and repair time of failed units are assumed to be exponentially distributed. The steady state queue size distribution is obtained by using recursive method. Expressions for the average number of failed units in the queue and the average waiting time are established.
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    N-policy for a machine repair system with spares and reneging
    (Elsevier, 2004-06) Kulshrestha, Rakhee
    This paper deals with the reliability characteristics of a machine repairable system with M-operating and S warm standby units. The units are assumed to fail in Poisson fashion. There is a provision of a removable repairman which repairs failed units according to exponential distribution. Due to impatience, the failed units may renege when repairman is busy. When N or more units are failed, the removable repairman turns on and starts the repair work. The repairman turns off when the system is empty. We use Laplace transforms technique to derive the explicit expressions of the reliability function and the mean time to system failure. Numerical results to highlight the effects of various system parameters to the reliability indices on the system have been provided.
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    A subrating channel assignment scheme for cellular radio network with directed retry
    (Elsevier, 2005-09) Kulshrestha, Rakhee
    In this paper the subrating channel assignment scheme is used to improve the performance of handoff packets. The subrating of a channel is done by dividing temporarily a full-rate channel into two half rate channels. Hand-off voice calls may also be served by subrated channels if all channels of the BS are occupied. The subrating of channels can degrade the quality, but it improves the grade of service (GOS) for hand-off calls and minimizes the delay. The provision of directed retry in overlapping area among neighbouring cells is also done for handoff attempts so that the blocking of handoff traffic can be checked to some extent. By using an iterative algorithm we obtain performance indices such as blocking probabilities, degradation in quality, total carried load, dwell time, etc. Numerical results have also been facilitated to prove the validity of the proposed iterative algorithm.
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    Transient Analysis of a Telecommunication System Using State Dependent Markovian Queue under Bi-Level Control Policy
    (JKAU, 2009) Kulshrestha, Rakhee
    In this paper, we develop a finite queueing model having single and batch service modes for telecommunication system, where two types of traffic, i.e. voice and data arrive in Poisson fashion. The server starts service only when N packets are accumulated in the system. The server performs service singly until there are C packets in the system. After then type 2 packets are discarded and all type 1 packets are served in a batch. The arrival rates of packets depend upon the server’s status. The transient state probabilities of system states are obtained by solving a set of linear equations with the help of Laplace Transform technique. Performance indices such as average queue length, expected idle time, and expected busy period are determined. We also investigate the optimal value of threshold parameter N and C after which the server changes the mode of service in order to minimize the expected cost. The numerical illustrations are provided to visualize the effect of various parameters on system performance
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    Performance Evaluation of Unified Index Hub Using Integrated Signature
    (IJARCS, 2010) Kulshrestha, Rakhee
    Due to its widespread application mobile computing has become reality. In real time broadcast, data management research community faces challenge from battery power and delay in data retrieval. The increasing populations of broadcast operator without widening the available electromagnetic spectrum worsen the situation. Index tree and signature techniques are generally employed to manage data in mobile environment. When similar type of data has broadcasted than signature technique is preferred over index tree technique for better data retrieval time. Lee and Lee model of integrated signature is effective in reducing access time. With many number of broadcast operators, the unification of operators is alternative way to manage data. The UIH developed by Verma S. et.al. is a way to unify the broadcast operators. This research work intends to propose a new model by applying integrated signature to UIH and compare the performance to state of art Lee and Lee model. The proposed model is simulated using Matlab7.4. The simulation result shows the proposed model out perform the existing state of art Lee & Lee model.
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    Time Efficient Indexing Technique for Querying Location Dependent Data in Wireless Broadcast
    (International Journal of Computer Applications, 2010-10) Kulshrestha, Rakhee
    Wireless communication and mobile computing have gained a lot concentration from the computer and communication research society. Wireless dissemination has emerged as an outstanding and scalable method to broadcast information to huge number of clients equipped with hand held devices. In practice, wireless broadcast faces challenge from issues like timely delivery of data, error free quality of service, low battery capacity and limited bandwidth. Different applications need to curb out different challenges. To support location based services in wireless data broadcast system a distributed spatial index (DSI) is popular. DSI indexing technique is in recent times has been becoming popular as reduce access time and energy consumption in location based queries because it has a linear yet fully distributed structure that facilitates multiple search path to be naturally mixed together by sharing links. Here, in this paper we address an issue where error free timely delivery of information is major concern. Such state of affairs generally appears in an inhouse environment where recharging of battery is not a serious concern. We have proposed a Data Replicated Distributed Spatial Index (DR-DSI) which is extension of Distributed Spatial Index to get advantages of data replication to reduce access latency.
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    Query Management for Efficient Data Access in Wireless Environment
    (IJCA, 2011) Kulshrestha, Rakhee
    With the cutting edge technology advance in wireless computers data broadcast has emerged as powerful tool for information dissemination to massive number of clients equipped with portable gadgets. In such computing system server continuously broadcast data over air channel without waiting for client’s response and client retrieve only the data pertaining to him. To retrieve such broadcasted data mobile client submit a query to broadcast channel and get responded in sequential manner. Hence query plays central role in wireless communication. The queries evoked in wireless environment are much more complex and varied than that in traditional tethered environment. Owing to their complex nature handling of wireless queries is a challenge to the database and networking research community. This paper studied various query management strategies for wireless environment and evaluates them for multichannel broadcast system.
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    Analysis of Multiple Queue Model in Cellular Networks with Sub Rating of Channels
    (King Abdulaziz University Journal, 2012) Kulshrestha, Rakhee
    In cellular Networks we generally consider a single queue for each cell, some authors proposed a model with a dedicated queue for each transceiver in the cell. We have extended the idea of dedicated queue for each transceiver in the cell with sub-rating channels to improve the Quality of Service (QOS) of the system. In this paper we have compared three models, in model-I we used guard channels to give priority to handoff attempts and a buffer for finite size is provided to give priority to handoff data attempts, further in model-II we have taken sub-rating channel scheme (SCS). In subrating scheme a full rate channel is temporarily divided into two half rate channels in the blocked cell; one half rate channel serve the originating call and another serves handoff call. We proposed a dedicated queue for each transceiver in the cell with sub-rating in model-III. The Fixed Channel Assignment Scheme is considered for all models. The probabilities of handoff failure, blocking probability of new calls, forced termination of handoff calls, probability of noncompleted calls for all models are calculated for varying assumed of values arrival rate of new data calls, arrival rate of new voice calls, buffer size of channels and service rates. We compared and analyzed the numerical results to validate the proposed models.