通訊技術不斷地朝向高傳輸速率和高移動性的目標前進，正交分頻多工系統是一套有效率的方式，能同時傳輸高速率並且對抗碼際干擾，其具有多個載波，當通道為頻率選擇性衰減時，系統必須要有一套有效率的方法來分配資源。 傳統的分頻多路存取，是將子載波以固定的方式分配給用戶，有別於此，若我們能夠依照通道的狀況和使用者的需求，將子載波和位元適應地分配給使用者，必能減少所需的功率輸出。 將功率最小化的問題，其解決方式太過於複雜，所以陸續有次佳的方法提出，本論文提出一套方法來分配子載波和位元，並求此方法的改善，最後我將分析這套方法的複雜度和表現的情況。 The communication technology is forward to the target of high data rate and high mobility. Orthogonal frequency division multiplexing (OFDM) system is an efficient system. It can transmit high data rate and combat intersymbol interference (ISI). It has many sub-carriers. When channel is the frequency selective fading channel, the system must have an efficient algorithm to allocate resource. Traditional OFDM allocate sub-carriers and bits to users statically. If we can allocate sub-carriers and bits to users according to channel gain and the need of users, it can decrease the power that we need. It is too complex problem to minimum the power in all system. Some paper propose the sub-optimal allocation algorithm continually. This thesis proposes a bit allocation algorithm for sub-carrier and improves this algorithm. I will show their complexity and performance finally.
