Hyoung-Kyu Lim

Utility-based downlink power allocation in multicell wireless packet networks

We introduce a utility-based radio resource management technique for multicell wireless packet networks. Assuming each base station operates to maximize its own cell utility, we try to maximize the system utility which is defined as the sum of each cell utility. By using the downlink transmit power of each base station as a control variable, we formulate a problem of system utility maximization. However, the problem is intractable because it contains non-convex functions, and, accordingly, the complexity is too high. Therefore, we first analyze a simple two-cell problem and take an intuitive approach to find its optimal solution. We extend this intuition to a general multi-cell problem and devise a simple heuristic algorithm that requires a light overhead of signaling between neighboring base stations. Through simulations, we compare, in terms of utility gain, our proposed heuristic algorithm with two competing schemes, optimal power allocation and maximum power allocation. As expected, the optimal allocation scheme shows the best performance but cannot be applied to real multi-cell problems due to its intractable complexity. Our proposed heuristic algorithm has very low complexity and its performance lies between the optimal allocation and maximum allocation schemes.

Complementing Security Breach of Authentication by Using Shared Authentication Information in Mobile WiMAX Networks

The signalling protocol vulnerability opens DDoS problem in Mobile WiMAX networks. This letter proposes an authentication method that uses the unrevealed upper 64bits of Cipher-based MAC as a solution. It runs for MSs in idle mode and reduces the calculation complexity by 59% under DDoS attack while incurring 1% overhead under normal condition.