tailieunhanh - Vehicular Technologies Increasing Connectivity Part 7

Tham khảo tài liệu 'vehicular technologies increasing connectivity part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Resource Allocation and User Scheduling in Coordinated Multicell MIMO Systems 171 Finally the iterative algorithm which solves the optimization problem 18 . minimizes the Chernoff upperbound is listed below. Although a formal proof has not been provided yet it is conjectured that Algorithm 2 converges to its optimal solution. At each iteration Ak is determined as a unique solution for all k and a fixed set of powers. Regarding the power iteration since the objective function 21 is concave in pbk when fixing all other powers a sequential update of the powers P1 P2 . pb P1. shall converge under individual base station power constraints. Algorithm 2 Resource allocation for single carrier systems with partial CSI 1 Initialize p 2 repeat 3 for each base station do 4 Update A with the solution of the polynomial 20 5 Update p by evaluating the KKT conditions 21 6 end for 7 until convergence of f A p No channel state information When there is no channel state information at the central station the strategy is to equally divide the total available power of each base station among all user terminals. Thus there is no optimization problem here. Assuming that the maximum power of each base station is equal to P and defining p Pbk P K then B Ak V abk 2 Pbk b 1 p V abk 2 Ak 22 b 1 where Ak is a chi-squared random variable with 4 M K 1 degrees of freedom. If it is assumed that Vbk 1 for all links then the cumulative distribution function of Ak is given by the following expression . r ÍM K 1 2 M K 1 1 1 7M K 1 k FAe y 1 exp ---y V 77 I --- ---y I . 23 A y p k p y k 0 k p y Let Ck 2Yk 1. Under these assumptions the outage probability of the system is given by K B Pout Y p 1 n Pr log 1 V abk 2 pbk Yk 1 k 1 b 1 K ị B 1 n Pr p V abk 2 2Yk 1 k 1 b 1 K 1 n Pr Ak Ck k 1 K . . 1 n 1 FAk Ck . 24 k 1 172 Vehicular Technologies Increasing Connectivity Performance of resource allocation strategies Figure 2 shows the outage probability performance versus signal-to-noise ratio .