高速下行鏈路封包存取是被稱為第三點五代的手機系統，能達到10Mbps以上的速率並且通過高速的分享通道解決封包瞬增的問題。為了因應無線網路通道狀況隨時間變動，達成無線資源有效運用，在高速下行鏈路封包存取中使用了動態調變與編碼的技術。使用者週期性的回報通道的狀況，而在規格書中定義了不同長短的週期，越短的週期能使得基地台更頻繁地取得通道資訊，因此能有更適當的資源分配。
但相對的，較頻繁的回報將造成多餘的電力浪費，並且影響其他通道的傳輸，因為如網頁的瀏覽這類資料傳輸有瞬時增加的特性，通道不是總在使用的情況下，這時的回報便是額外的負擔。所以一個良好的回報機制在新一代的手機系統中也扮演著重要的角色。
在此，我們提出了錯誤回歸隨選回報的方法，這方法擁有隨選回報方法能較好的保護第一個傳送封包的特性，並且通過監測通道的錯誤率在適當的時機啟動錯誤回歸，利用了封包之間傳輸的相關性和通道變化的相關性。透過我們的方法，能有較少的錯誤率和輕微的吞吐量影響，因此在相同的電力消耗下能有較好的表現。

HSDPA is called 3.5G related to 3G WCDMA/UMTS cellular system. It can reach over 10Mbps data rate and resolve the data bust problem by a high capacity shared channel. An important technology, AMC is used in HSDPA to manage the radio resource according the channel conditions, so that a good channel usage can achieve in HSDPA. In order to get the channel conditions between Node B and UEs, UEs periodically report the channel quality and have different cycles are defined in 3GPP specification.
A shorter cycle used make Node B better in resource deployment since Node B can know the channel conditions more often. But the channel is not always on used, the periodical report will cause unnecessary power consumption and channel interference. So a good feedback mechanism also plays an important role in the HSDPA.
In this paper, we present an error regressed on demand feedback scheme. This scheme is based on the on-demand scheme that has better ability on protecting the first packet. Besides, our scheme also monitors the error rate of channel and activates the error regression on appropriate time, and takes advantage of the correlation of data transmission and the correlation of channel changes. By this way, our scheme can reach less error rate and light decrease throughput, so that has good performance on power efficiency.

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