However, the optimization problem with consideration of the diverse arbitration www.selleckchem.com/products/Calcitriol-(Rocaltrol).html metrics is complicated and difficult to be extracted and solved. Thus, most of the proposed strategies [3�C26] have solved the reader interference problem with consideration of one or two arbitration metrics. For example, frequency-hopping spread Inhibitors,Modulators,Libraries spectrum (FHSS) utilizes multiple frequency channels, while DCS, VDCS (Colorwave) [5,6] and listen before talk (LBT) [7] require readers to operate at different times. DAPC and PPC [8,9] dynamically adjust transmission power at discrete-time steps using the SNR of backscatter signal measured at each reader. Although the existing proposals may be effective in preventing the reader interference problem, they may Inhibitors,Modulators,Libraries not be the best solution due to insufficient arbitration metrics.

In this paper, we introduce a novel cross-layer optimization design based on mixed-integer linear programming (MILP), which optimally Inhibitors,Modulators,Libraries assigns communication channel, time, and output power to each RFID reader. The solution from the optimization design not only solves the reader interference problem, but also achieves multiple objectives such as minimum interrogation cycle, maximum reader utilization, and energy efficiency. Based on the priority of the multiple objectives, our cross-layer design is presented as a three-stage optimization Inhibitors,Modulators,Libraries problem. In the first stage, we optimize the RFID system to have minimum cycle time. Here, each RFID reader should be scheduled to successfully recognize the tags within its desired interrogation range at least once during a cycle.

Once the temporal schedule is assigned, the RFID readers repeat the same temporal pattern after one cycle. Our first aim is to minimize this cycle so that interrogation delay of RFID reader can be minimal. In general, the solution, i.e., resource assignment set, to the first stage that provides minimum cycle time is not unique. Cilengitide Thus, among the multiple solutions, it is desirable to select a set that provides the maximum utilization. In the second stage, we optimize the system to achieve the maximum utilization while maintaining the minimum cycle time found in the first stage. Again the system can be optimized in terms of output power while maintaining the optimality found in the previous stages.

Then, we transform the three-stage optimization problem into a compact single-stage optimization problem by properly assigning a weight to each of the three objectives, because selleckchem the three-stage optimization is cumbersome to execute.The rest of the paper is organized as follows. The existing proposals to solve the RFID reader interference problem are reviewed in Section 2, and the network model and interference model are introduced in Section 3. The cross-layer optimization designs are presented in Section 4. Numerical results and comparative view of the anti-collision approaches are shown in Sections 5 and 6.