無線多媒體應用是目前之趨勢,因此對於能夠提供高速率傳輸之無線通訊系統的需要與日俱增,換言之,無線寬通訊系統必須能夠解決因多重路徑傳而牽生之頻率選擇性衰落及對於高速移動所產生之時間選擇性衰落具有良好之抵抗能力。時空碼為一傳送分集,其結合了天線分集與編碼之概念。在發射機使用時空編碼技術並在接收時運用訊號處理的技巧,使得多根傳送天系系統擁有分集以及編碼所帶來之好處,進而提高系統之效能與容量。尤其對下傳連結之接收機(手機)而言,這是非常必要之作法,因為手機體積越小,成本越少,功率耗損愈低愈好。在所有時空碼中,塊狀時空碼具有很低之複雜度以及非常優越之性能。 在無線通訊裡,頻寬是一項非常重要的資源;要如何在不增加頻寬的下增加系統的可靠度一直是大家所研究的方向。在1998年,時空方塊碼(space-time block code, STBC)被提出來解決一個問題,時空方塊碼的基本概念是在傳送端或接收端加天線的數目以達到系統可靠度的提升;而為了使系統簡單化,在論文中,我們只討論系統裝一根接收天線與二根傳收天的效能本論文將重顧兩項先進傳輸技術:STBC及CDMA之探討。
Wireless communication is rapidly growing and has gradually replaced traditional wired solutions in many applications, e.g.,personal communications and local area networks, on account of the advantages of mobility and ease of installation. So high data rate transmission is also inevitable. Here we use Space Time Block Code and combine DS-CDMA systems. we try to compare the performance of new codging and traditional coding . First, chapter 1 we introduce the evolution of transmission. Chapter 2, we disscussed the new coding .The space time usually be used to resist fading channel. Chapter 3, we idsscussed a system of DS-CDMA systems.we associated STBC and DS-CDMA systems. Why we often used the system to work. Chaper 4 we discussed the some case , and verified by the simulation results. Chapter 5 a conclusion and suggestion.