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A low cost frequency-dependent (FD) I/Q imbalance self-compensation scheme is investigated in this paper. The direct conversion transmitters are widely used in wireless systems. However, the unwanted image-frequencies and distortions are inevitably introduced into the direct conversion system. This problem is even severer in wideband systems. Therefore, the accurate estimation and compensation of I/Q imbalance is crucial. The current compensation method is based on external instruments or internal feedback path which introduces additional impairments and is expensive. This paper proposes a low cost FD I/Q imbalance self-IQ-demodulation based compensation scheme without using external calibration instruments. First, the impairments of baseband and RF components are investigated. Further, I/Q imbalance model is developed. Then, the proposed two-step self-IQ-demodulation based compensation scheme is investigated. In the first step of the scheme, the local oscillator (LO) related I/Q impairments parameters are estimated. Then in the second step, the overall FD I/Q imbalance parameters are estimated by utilizing the transmitter LO. To realize this self-IQ-demodulation algorithm, this paper introduces minor modifications to the current power detector circuit. Afterwards, the estimated parameters are applied to the baseband equivalent compensator. This sophisticated algorithm guarantees low computation complexity and low cost. The compensation performance is evaluated in laboratory measurement. [ABSTRACT FROM PUBLISHER]

Most wireless microphones operate on vacant television broadcasting channels in the very high frequency and ultrahigh frequency bands, as secondary users operating on the no-interference and no-protection basis. Some wireless microphones share the 2.4 GHz band with other wireless devices. The 698–806 MHz band was repurposed when television broadcasting switched from analog to digital (and the 600 MHz band may be repurposed in the near future), resulting in less spectrum available for wireless microphone operations. To keep wireless microphones operating effective in this environment, engineers, researchers, and regulators require comprehensive knowledge of the spectrum, interference, and regulations regarding wireless microphones. This paper first presents the characteristics of the frequency bands currently allocated for wireless microphone operations. Next, interference that may be experienced by wireless microphones and frequency coordination required to allow multiple microphones to work together at the same site without interference are presented. Finally, it summarizes the regulations in Canada, United States of America, European Union, and Australia for wireless microphones regarding allowable transmitter frequency, power, bandwidth, channel masks, maximum frequency deviation for FM, and spurious emissions. [ABSTRACT FROM PUBLISHER]

The demand for multimedia services is increasing at an astonishing speed. To deal with the overwhelming data traffic, approaches such as extending available bandwidth are proposed in wireless communication technology. Apart from the enlargement of bandwidth, the enhancement of the efficiency of resource usage is also grabbing the eye. 3GPP has introduced MBMS as a solution to improve the efficiency of resource usage since LTE release 8. Although going through many further enhancements in the recent releases, MBMS still needs modification to meet the requirements for applications in the future. Hence, for the emerging NR MBMS, more flexible network structure, deployment, and resource usage are the main topics for enhancements. In this paper, we identify that the system performance can be improved by adjusting the SFN area with the existence of inter-bearer interference. By allocating the same resources to different SFN areas, the system performance enhances in some cases. As such, we propose a graph-based solution called GGPA to address the problem of utility optimization. After an exclusion stage and a merging stage, GGPA outputs a result which partitions a given topology into multiple non-overlapping SFNs. The simulation results show that GGPA attains the sub-optimality in each identified scenario; in addition, it consumes less calculation time compared with exhaustive search. With the dynamic configuration of MBSFN areas resulting from GGPA, the NR MBMS could achieve better resource efficiency. [ABSTRACT FROM AUTHOR]

OFDM has been applied in a wide variety of wireless communications in recent years since it has the advantage over the conventional single-carrier modulation schemes when enduring the frequency-selective fading. However, intercarrier-interference (ICI) and interblock interference (IBI) due to the Doppler effect, carrier frequency drift of local oscillators and multipath fading limit the capability of OFDM systems. In this paper, a new generalized mathematical model for intercarrier and interblock interferences is derived for wireless mobile OFDM systems, in which Doppler frequency drift, local carrier frequency offset, multipath fading, and cyclic prefix coding are all present in reality. Such a new ICI/IBI model can be applied for OFDM performance evaluation in different environments. This new formulation of IBI and ICI provides a generalized framework which includes special ICI models appearing in the previous literature. Besides, the derived OFDM performance evaluation analysis in this paper can greatly benefit OFDM designers for wireless multimedia networks and digital video broadcasting technologies. [ABSTRACT FROM AUTHOR]

Wireless microphones are indispensable to modern society. They are used worldwide by professionals and amateurs for such applications as live performances, electronic news gathering, and conference presentations. Due to the radio spectrum crunch, wireless microphones have become a hot topic of discussion and debate among television broadcasters, wireless microphone manufacturers, wireless network operators, and spectrum regulators. In order to keep wireless microphones operating well, it is necessary to give engineers, researchers, and regulators a comprehensive overview of wireless microphones in the aspects of technologies, spectrum requirements, and interference that may be experienced or generated by wireless microphones. This overview is divided into two parts. Part I provides an overview of typical wireless microphone system components, their performance requirements and technical parameters, and the technologies that are used in current wireless microphones. Part II focuses on the spectrum, sources of interference, and regulations surrounding wireless microphones. [ABSTRACT FROM PUBLISHER]

The International Telecommunications Union has defined the frequency band in which Broadcasting Satellite Systems (BSS) and Multi-channel Multipoint Distribution Systems (MMDS) should coexist. With the development of MMDS working on the same frequency band as the BSS, and theoretically with identical technical parameters, an important question arises of how to set up the parameters of terrestrial distribution systems so that their coexistence with satellite systems is enabled while at the same time terrestrial systems are not made technically too limited. In this article, we summarize the results of extensive research work that sought to answer the above question. Results of practical measurements performed on MMDS and BSS are presented. The calculations were performed according to the ITU-R Regulations. In addition to measuring professional commercial systems, we constructed a transmitting/receiving system to simulate a worst-case scenario-having the BSS and MMDS transmitters and receiver (measurement system) on the same line (Fig. 1). From the analysis of the empirical measurements and calculations, we determined how the parameters should be set up so as to enable the quality coexistence of BSS and MMDS. We focused on those parameters that significantly influence such a coexistence: the geographical position of BSS and MMDS transmitters, Symbol Rate, Code Rate, MMDS Transmitter Frequency, and MMDS Transmitter Power. [ABSTRACT FROM AUTHOR]