Constant Envelope Modulation Techniques for Limited Power Millimeter Wave Links

Abstract

The demand for increased capacity and link availability for mobile communications requires the utilization of higher frequencies, such as millimeter waves at extremely high frequencies (EHFs) above 30 GHz. In this regime of frequencies, the waves are subjected to high atmospheric attenuation and dispersion effects that lead to a degradation in communication reliability. The fact that solid-state millimeter and sub-millimeter wave sources are producing low power calls for effective signaling utilizing waveforms with a low peak to average power ratio (PAPR), such as constant envelope (CE) modulation. The CE techniques present a PAPR of 0 dB resulting in peak power transmission with high energy efficiency. The study of the performances of constant envelope orthogonal modulation techniques in the presence of co-channel interference is presented. The performance is evaluated in terms of the average symbol error rate (SER) using analytical results and simulations. The theory is carried out for the CE-M-ary time orthogonal (CE-MTO) and CE-orthogonal frequency division multiplexing (CE-OFDM), demonstrating comparable performances while leading to a simpler implementation than that of the CE-OFDM.Keywords: co-channel interference (CCI); constant envelope OFDM (CE-OFDM); constant envelope MTO (CE-MTO); millimeter wave communications IntroductionWireless communications require more bandwidth because of the necessity of the capacity increasing, the availability, and the reliability. As a result, new bands need to be searched for in the electromagnetic spectrum, reaching millimeter and sub-millimeter wavelengths. Recent technological developments have made extremely high frequencies (EHF) a candidate for wireless applications, such as for the fifth generation (5G) of cellular communications (for which bands in the 24.25-29.5 GHz and 37-43.5 GHz are already allocated [1]), satellite communications [2,3], high resolution radars [4,5], and remote sensing [6,7]. The realization of wireless communications in the millimeter wavelength systems is becoming commercial, compact, and less expensive [8,9].However, the fact that the atmospheric medium is not entirely transparent to millimeter waves (MMWs) requires careful considerations regarding the frequency selective absorption and dispersion effects emerging in this band [10]. Moreover, low power transmissions and reduced receiver sensitivities lead to further degradation in the link performances [11]. These phenomena also apply to radars and remote sensing systems operating in the millimeter and Terahertz frequencies [12].While the bands in the ultra-high frequency (UHF) spectrum are fully used, millimeter waves (the EHF spectrum) are relatively free of users, and broad bands of frequencies can be allocated for wireless communication applications. With the demand for more spectrums for the mobile communication infrastructure, additional bands within the millimeter waves regime are allocated for the future 5G of the cellular networks [13]. The extension of the spectrums enables ultra-...