A Research on Spectrum Allocation Using Optimal Power in Downlink Wireless system

A resource Allocation Problem for spectrum sharing in wireless communication system. Using multiinput multi-output orthogonal frequency division multiple ( MIMO-OFDM) is a very promising technology for enhancing the flexibility and efficiency of cellular and future communication systems. A joint optimization problem for resource allocation is solved by a combine scheme of multiple-input multiple-output with orthogonal frequency division multiple (MIMO-OFDM) and used for broadband wireless applications. The energy efficiency is also key parameter in designing and evaluating communication system. we can address the assignment of subcarriers and power allocation to all users to optimize the sum of user average data rates, total available transmitted power, and proportionality among users, subcarriers. We propose an algorithm that process subcarrier and power allocation simultaneously under data rate constraint. Computationally efficient water filling algorithm for multiuser OFDM. This algorithm is based on the multiuser water filling theorem and determines the subcarrier allocation for a multiple access OFDM system, The presented iterative algorithm performs well, also with a high number of sub channels.