ETRI Journal
- Volume 29 Issue 4
- /
- Pages.445-451
- /
- 2007
- /
- 1225-6463(pISSN)
- /
- 2233-7326(eISSN)
An Efficient Adaptive Modulation Scheme for Wireless OFDM Systems
- Lee, Chang-Wook (School of Electrical Engineering and Computer Science, Kyungpook National University) ;
- Jeon, Gi-Joon (School of Electrical Engineering and Computer Science, Kyungpook National University)
- Received : 2006.09.07
- Published : 2007.08.31
Abstract
An adaptive modulation scheme is presented for multiuser orthogonal frequency-division multiplexing systems. The aim of the scheme is to minimize the total transmit power with a constraint on the transmission rate for users, assuming knowledge of the instantaneous channel gains for all users using a combined bit-loading and subcarrier allocation algorithm. The subcarrier allocation algorithm identifies the appropriate assignment of subcarriers to the users, while the bit-loading algorithm determines the number of bits given to each subcarrier. The proposed bit-loading algorithm is derived from the geometric progression of the additional transmission power required by the subcarriers and the arithmetic-geometric means inequality. This algorithm has a simple procedure and low computational complexity. A heuristic approach is also used for the subcarrier allocation algorithm, providing a trade-off between complexity and performance. Numerical results demonstrate that the proposed algorithms provide comparable performance with existing algorithms with low computational cost.