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SCHEDULING IN NETWORKS WITH TIME-VARYING CHANNELS AND RECONFIGURATION DELAY

ABSTRACT

We consider the optimal control problem for networks subjected to time-varying channels, reconfiguration delays, and interference constraints. We show that the simultaneous presence of time-varying channels and reconfiguration delays significantly reduces the system stability region and changes the structure of optimal policies. We first consider memory less channel processes and characterize the stability region in closed form. We prove that a frame-based Max-Weight scheduling algorithm that sets frame durations dynamically, as a function of the current queue lengths and average channel gains, is throughput-optimal. Next, we consider arbitrary Markov-modulated channel processes and show that memory in the channel processes can be exploited to improve the stability region. We develop a novel approach to characterizing the stability region of such systems using state-action frequencies, which are stationary solutions to a Markov Decision Process (MDP) formulation. Moreover, we develop a dynamic control policy using the state-action frequencies and variable frames whose lengths are functions of queue sizes and show that it is throughput-optimal. The frame-based dynamic control (FBDC) policy is applicable to a broad class of network control systems, with or without reconfiguration delays, and provides a new framework for developing throughput-optimal network control policies using state-action frequencies. Finally, we propose Myopic policies that are easy to implement and have better delay properties as compared to the FBDC policy.

EXISTING SYSTEM	PROPOSED SYSTEM
EXISTING CONCEPT:- In the existing system large queue lengths, since the policy keeps the same schedule during the resulting long frames, we obtain the time-average channel gains in the system, as seen in the stability condition In this section, we consider systems that have time-varying channels with memory. We establish the stability region for such systems and propose a throughput-optimal dynamic control policy.	PROPOSED CONCEPT:- In the proposed system The main contribution of this paper is in solving the scheduling problem in single-hop networks under arbitrary reconfiguration delays, time-varying channels, and interference constraints for the first time. These papers studied saturated system models, and the optimality of myopic policies was established for a single server and two channels in, for arbitrary number of channels in, and for arbitrary number of channels and servers
EXISTING ALGORITHM:- Time-Slot Algorithm	PROPOSED ALGORITHM:- VFMW Algorithm
ALGORITHM DEFNITION:- Characterization of the stability region does not scale with the number of nodes. This is also true for networks without reconfiguration delays. In fact, for a fixed channel state, the stability region of the corresponding system without any reconfiguration delay is the convex-hull of the possible activations.	ALGORITHM DEFNITION:- It algorithms that make scheduling decisions based on time-average channel gains and queue lengths stabilize the system by keeping the current schedule over a frame of duration that is a function of the queue lengths.
DRAWBACKS:- Not possible to opportunistically take advantage of the diversity in time-varying channels Not achieving throughput.	ADVANTAGES:- Significantly reduced stability Reduce reconfigurations delay Resolves Scheduling Problems