近幾年，IEEE 802.11p/WAVE(無線接取車載環境)為車載網路下新興的標準之一。於車載環境下廣播資料與控制封包變得更為重要，特別是針對安全性與非安全性應用下廣播資料封包與狀態交換。IEEE 1609.4標準有定義廣播封包於控制通道(Control Channel, CCH)間隔內被傳送，但在做通道交換(channel switch)時會發生封包碰撞的情形。因此，本論文提出以機率為基礎之壅塞控制機制(PCC, Probability based Congestion Control)。此機制每輛車先利用廣播Hello訊息封包估計鄰近車輛的數目，之後透過機率模型計算出期望的位移間隔值並預先加到原始MAC contention window之前。透過PCC機制可降低封包碰撞情況並提升傳輸的吞吐量。如給定車輛數為60台，模擬結果顯示透過使用PCC機制約降低45%至60%封包遺失的機率。

In recent years, IEEE 802.11p/WAVE (Wireless Access in Vehicular Environments) is an emerging family of standards intended to support wireless access in Vehicular Networks. Broadcasting of data and control packets is expected to be crucial in this environment. Both safety-related and non-safety applications rely on broadcasting for the exchange of data or status and advertisement messages. Most of the broadcasting packet is designed to be delivered on a given frequency during the Control Channel (CCH) interval set by the IEEE 1609.4 draft standard. However, the PCC (Probability based Congestion Control) mechanism is firstly developed based on the estimation of potential neighboring vehicles through probabilistic model and broadcasting Hello messages, and then calculating the expected offset slots for reduce the collision situations, and thus increase transmission throughput. For a given number of vehicles (N=60), the simulation results show that around 45%~60% reduction in packet loss probability could be achieved by using PCC mechanism.