This paper considers the implementing issues of signal-time coding (STC) at physical layer in additive white Gaussian noise relay networks. Firstly, a performance evaluation criterion, the reliable information per symbol (RIPS), is proposed to characterize the performance of STC in noisy wireless networks. Secondly, a new construction scheme based on route ID for the codeword of STC is presented, and some structural properties of the codeword of STC are investigated. Thirdly, the error probabilities of STC in both the signal domain and the time domain are discussed. Furthermore, two implementing schemes, that is, the energy detection based STC (ED-STC) and the symbol detection based STC (SD-STC), are proposed, and their performance bounds in terms of RIPS are discussed. Numerical analyses show that both ED-STC and SD-STC outperform the traditional transmission methods in terms of effective information rate even under some practical conditions.