This paper presents a differential detection scheme for transmit diversity using two transmit antennas without requiring channel state information at either the transmitter or receiver. The scheme uses equal energy constellations and simple encoding, with low decoding complexity at the receiver. It provides full spatial diversity and does not require channel state information at the receiver. The scheme extends differential detection to two transmit antennas. The paper discusses existing transmit diversity schemes, including space-time trellis coding and space-time block coding, which provide significant gains over earlier schemes. However, these schemes require channel state information at the receiver. In contrast, the proposed differential detection scheme does not require such information. The paper describes a simple transmission scheme assuming coherent detection, including a system model and encoding algorithm. It also presents a coherent detection algorithm that achieves maximum likelihood decoding based on linear processing at the receiver. The paper then introduces a differential encoding algorithm for two transmit antennas. It describes how the encoding process works, using a set of vectors with specific properties to represent constellation symbols. The encoding algorithm is inductive, using previously transmitted symbols to encode new data. The paper then presents a differential decoding algorithm for two transmit antennas. It describes how the receiver uses previously received symbols to decode new data. The decoding algorithm is based on linear processing at the receiver and involves finding the closest vector in a set of vectors to a received signal. The paper analyzes the performance of the proposed differential detection scheme, showing that it incurs a 3 dB loss compared to coherent detection. Simulation results are presented for BPSK, QPSK, and 8-PSK constellations, showing the performance of the differential detection scheme compared to coherent detection. The paper concludes that the proposed differential detection scheme provides full spatial diversity without requiring channel state information at the receiver. It also notes that the scheme works for quasistatic and nonfrequency-selective channels. The paper suggests that extending the scheme to more than two transmit antennas is a nontrivial task and requires the theory of generalized orthogonal designs.This paper presents a differential detection scheme for transmit diversity using two transmit antennas without requiring channel state information at either the transmitter or receiver. The scheme uses equal energy constellations and simple encoding, with low decoding complexity at the receiver. It provides full spatial diversity and does not require channel state information at the receiver. The scheme extends differential detection to two transmit antennas. The paper discusses existing transmit diversity schemes, including space-time trellis coding and space-time block coding, which provide significant gains over earlier schemes. However, these schemes require channel state information at the receiver. In contrast, the proposed differential detection scheme does not require such information. The paper describes a simple transmission scheme assuming coherent detection, including a system model and encoding algorithm. It also presents a coherent detection algorithm that achieves maximum likelihood decoding based on linear processing at the receiver. The paper then introduces a differential encoding algorithm for two transmit antennas. It describes how the encoding process works, using a set of vectors with specific properties to represent constellation symbols. The encoding algorithm is inductive, using previously transmitted symbols to encode new data. The paper then presents a differential decoding algorithm for two transmit antennas. It describes how the receiver uses previously received symbols to decode new data. The decoding algorithm is based on linear processing at the receiver and involves finding the closest vector in a set of vectors to a received signal. The paper analyzes the performance of the proposed differential detection scheme, showing that it incurs a 3 dB loss compared to coherent detection. Simulation results are presented for BPSK, QPSK, and 8-PSK constellations, showing the performance of the differential detection scheme compared to coherent detection. The paper concludes that the proposed differential detection scheme provides full spatial diversity without requiring channel state information at the receiver. It also notes that the scheme works for quasistatic and nonfrequency-selective channels. The paper suggests that extending the scheme to more than two transmit antennas is a nontrivial task and requires the theory of generalized orthogonal designs.