在無線網路上的平均分散和連續性的錯誤造成封包錯誤，混合式自動重送機制藉由結合自動重送和前向糾錯回復錯誤。前向糾錯可分為封包層級和位元組層級，如果混合式自動重送結合位元組層級前向糾錯，錯誤的編碼區段如果不能被位元前向糾錯回復時則重送該錯誤區段，由於位元組前向糾錯保護能力不足，自動重送發生頻率會提高。如果混合式自動重送結合封包層級前向糾錯，雖然重送和前向糾錯的回復負擔很大，但是它的保護能力及範圍都較為寬廣。子封包層級前向糾錯藉由縮小封包層級的編碼單位來減小在回復錯誤時的負擔但是需要使用檢查和來辨認錯誤的子封包。在這篇論文我們提出一個結合位元組和子封包前向糾錯機制並且再加上自動重送來減少錯誤回復負擔，在我們的機制中，子封包前向糾錯的檢查和由位元組前向糾錯取代而且根據動態調整自動重送的次數。此外，根據目前的位元錯誤率代入負擔付出模組來動態調整子封包和位元組前向糾錯的編碼率和編碼單元而重送次數使用時間延遲模組來計算。實驗結果顯示可適性位元組和子封包前向糾錯及重送機制可以得到較好的回復效率。

Uniform bit error and burst bit error cause packet error in wireless networks. Hybrid Automatic Repeat request (HARQ) helps recover from packet error by combining ARQ and Forward Error Correction (FEC) protection mechanisms. Packet level FEC (P-FEC) and Byte level FEC (B-FEC) are two different types of FEC. In a HARQ with the B-FEC mechanism, the error coding block is retransmitted when B-FEC cannot recover from errors. ARQ retransmits frequently under high bit error rate or burst error pattern conditions. In a HARQ with the P-FEC mechanism, ARQ retransmission overhead and P-FEC recovery overhead are high, but the mechanism benefits from the P-FEC recovery range. Sub-Packet level FEC (SP-FEC) decreases the recovery overhead by reducing the P-FEC coding unit but still uses a checksum to identify error sub-packets. In this paper, we propose a combination of Byte and Sub-Packet FEC (BS-FEC) mechanisms with the ARQ mechanism to reduce error recovery overhead. In the proposed system, the SP-FEC checksum is replaced by B-FEC and ARQ is provided adaptively when the network environment deteriorates. Moreover, the adaptive SP-FEC (n, k) and the adaptive B-FEC bit rate are decided according to immediate network conditions by an overhead cost model, while the ARQ retry limit is decided by a time constraint mode. Numerical and simulation
experimental results show that BS-FEC mechanism obtain better recovery efficiency with reduced recovery overhead.

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