Data transmission over mobile radio channels is investigated. The high-level data link control protocol is used. The message is sent in a packet and a retransmission is necessary if errors are detected in the receiver. Differential phase-shift keying modulation is used. Expressions of system efficiency and delay are derived. Numerical results show that the system has acceptable performance when average signal-to-noise ratio is high, while lower signal-to-noise ratio results in lower efficiency and larger delay. In order to improve system performance, a diversity technique is adopted. It is found that the diversity technique is effective in increasing system throughput and reducing system delay. It is concluded that the implementation of diversity is essential in such error detection and retransmission communication schemes over mobile channels.
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