本研究探討無線電分封通訊應用於道路自動收費系統可行性．無線電分封
通訊之穩定性取決於多項因素，如系統服務速率，多重存取方式，以及新
進入系統之使用者的速率等，因此在設計系統時需將這些因素列入考慮，
並在系統穩定性與效率間作一平衡的抉擇，本研究以頻道選擇多重選取的
架構（CsMA），考慮道路使用者駕駛速度，行車間距，通訊涵蓋範圍及其
它交通相關問題，來探討使用者進入系統的速率（包含新進入系統使用者
的速率及封包重傳的機率）對無線電分封通訊系統穩定性的影響．我們利
用模擬分析，對通道容量不足所產生的不穩定現象，探討所須增加的位元
速率與頻道數，以選定可靠的雙向通訊策略．

In this study , we analyze the stability of an electronic toll
collection (ETC) system , using packet radio approach .
Stability of the packet radio network depends on several
factors, such as system service rate,multiple access scheme ,
arrival rate , etc . These factors must be studied to analyze
the tradeoff between system stability and performance . The
analysis is based on CsMA (Channel-selection Multiple Access)
simulation model. We simulate the arrival rates,including the
rate of new arrivals and the retransmited packets, with the
considerations of vehicle speed,vehicle interarrival time and
the stability of such an ETC system . Simulation results
suggests that a reliable and cost-effective wireless two-way
communication system can be established.