Link Budget Evaluation Research Articles

Uplink coverage enhancements for extremely large-cell sites

In urban areas, the network operators deploy small-cell sites and install a large number of base stations to support densely populated cellular users. A similar small-cell deployment in rural areas is not feasible for the operators, as it will significantly increase the capital expenditure, and the return on the investment will also be comparatively lower. Hence, the most feasible way to provide cellular connectivity to rural areas is the deployment of large-cell sites. However, the technology developed for International Mobile Telecommunications (IMT)-Advanced standard (or 4G) was evaluated for an inter-site distance of 1.732 km, making the large-cell connectivity required for rural areas an afterthought. For cellular last-mile rural connectivity to be a reality through IMT-2020 (or 5G), the key is to have future technologies supporting large cells. In large-cell sites, the users experience comparatively more path loss, and thus, have poor signal coverage. Further, compared to downlink, the transmission power in uplink is limited, and therefore, uplink transmissions define the coverage of the communication system. Motivated by this, we propose several coverage solutions for uplink, considering an extremely large-cell site scenario. We initially analyze the received signal-to-noise ratio with 4G/5G systems at various distances based on the link budget evaluation. At larger inter-site distances, we show that it is infeasible to achieve cellular coverage with the current 4G/5G specifications. We then propose enhancements related to the waveform, modulation and coding schemes, resource allocation, and power control mechanisms. We evaluate the proposed enhancements through system- and link-level simulations, and show a significant improvement in the coverage for cell-edge users. We also show that our proposed enhancements achieve close to two times the improvement in the network capacity when compared to the currently available 5G specifications.

Millimeter-Wave and Terahertz Fixed Wireless Link Budget Evaluation for Extreme Weather Conditions

To develop highly reliable fixed wireless links, such as mobile backhaul and fronthaul systems, it is essential to evaluate the link budget under extreme weather conditions. In this paper, we presented a link budget evaluation for fixed wireless links using radio signals at four different carrier frequencies: 75.375, 85.375, 275, and 400 GHz. As examples of extreme weather conditions, we focused on storms which can be defined as the combination of high temperature, violent rain, and strong winds. A theoretical model was proposed to evaluate the attenuation by the wind effect, which was due to mechanical vibration. Using the proposed model, we evaluated the link attenuation with different weather parameters, such as clear weather condition, different rain rates, and strong wind. In addition, the maximum channel capacities were estimated based on the model. According to the calculation results, it can be confirmed that the attenuation caused by heavy rain is the dominant factor to the whole system. Besides, the attenuation due to antenna gain degradation induced by the wind effect is considerable for the wireless link at high frequencies (275 and 400 GHz). This manuscript includes a comprehensive discussion regarding various weather factors including gas, rain, and wind, which impact the fixed wireless links. The obtained results would be useful for designing a high reliability fixed wireless link to operate under different weather conditions.

Channel Characteristics and Wireless Telemetry Performance of Transplanted Organ Monitoring System Using Ultrawideband Communication

Recently, wireless implanted applications have attracted considerable interest in the medical domain due to their capability to offer healthcare sensing and monitoring. One such promising application is the wireless monitoring of transplanted organs, particularly a transplanted liver. Ultrawideband (UWB) technology is well suited for wireless implanted applications since it allows physical size reduction, as well as increased longevity of the implanted devices. However, because of the high attenuation of UWB signals inside the human body, it is necessary to examine their propagation characteristics and demonstrate the feasibility of such an application. In this paper, an investigative study involving the liver implanted wireless telemetry link using UWB technology is presented. Measurements using multilayer phantoms and simulations using a human digital model have been conducted within the frequency band of 4.5–6.5 GHz. Multilayer phantom measurements have demonstrated the attenuations ranging between –50 and –100 dB over the considered frequency band. A path loss model at the liver area has been obtained from the simulations. Also, the numerical results have shown that the attenuation variation due to respiration-induced organ movements was within 30-dB range with respect to the largest organ movement distance of 40 mm, which emphasized the influence of organ movements on the in-body attenuations. Our preliminary link budget evaluation of liver–skin surface communication link, including the effect of shadowing and organ movements, estimated that it is possible to achieve a high data rate of 10 Mb/s with a bit error rate of 10−3 at a distance of about 40 mm.

A New Approach to the Link Budget Concept for an OAM Communication Link

Following on from the increasing interest for electromagnetic waves carrying Orbital Angular Momentum (OAM), different configurations of antenna systems able to generate such beams have been proposed. However, in our opinion, a traditional radiation pattern approach does not provide the right picture of an OAM-based communication link. For this reason we propose a new general concept, the "OAM-link pattern", which takes into account the peculiar phase structure characterizing these waves. Focusing on OAM transmissions between antenna arrays, we introduce a formula for the link budget evaluation which describes the whole communication link and directly leads to a "classically shaped" main lobe pattern for a proper rephased reception in the case of uniform circular arrays.

Numerical Characterization and Link Budget Evaluation of Wireless Implants Considering Different Digital Human Phantoms

This paper presents a numerical investigation of the radiation characteristics of gastric, bladder, and cardiac implants based on the finite-differences time-domain method. Simulations were performed at the medical implanted communication services (MICS) and the industrial, scientific, and medical radio bands, respectively, using three different digital inhomogeneous human phantoms (two male and one female models). The numerical analysis demonstrated that the radiation performances are strongly dependant on the location of wireless implants, as well as the body mass index of the subject. The results highlighted the significance of subject specific modeling when designing wireless implants. A link budget calculation was proposed for the communication between a left-ventricular wireless implant and an off-body base station as an example for MICS applications. It is demonstrated that, due to the presence of human tissues, the antenna radiation from wireless implants tends to be directive, and therefore, the signal-to-noise ratio in communication links is strongly dependent on the orientation of the human subject with respect to the base station.

Coverage prediction and performance evaluation of wireless metropolitan area networks based on IEEE 802.16

This work aims at performing a more detailed coverage and performance analysis of wireless metropolitan area networks based on the IEEE 802.16 standard, which is the basis of WiMAX technology. This paper provides a more formal approach to estimate coverage and performance of WiMAX technology, which enables simplified link budget evaluation. Initially, the major functionalities within the standard that support operation in NLOS scenarios are described. Several operation scenarios are then specified, based on the combination of key system parameters (e.g., transmission power, operation frequency, channel bandwidth) and coverage prediction models. In order to support coverage estimation for operation frequencies up to 6 GHz, appropriate coverage prediction models are adopted for frequencies above 2 GHz. Based on the proposed approach, coverage and performance are estimated under some real world scenario conditions, considering Brazilian regulatory rules for licensed and license-exempt bands.

Concept of a wireless indoor video communications system

The aim of this paper is to describe and specify the concept of a future wireless indoor video communications system. The radio frequency link operating in the 2.4/5.8 GHz ISM-band is considered as the transmission medium. First, the general concept of the system which is based on a decentralized/distributed topology is illustrated in detail. Then, the physical layer of the system which is based on a combination of TDMA and FDMA is examined. The system supports variable rate transmission and is flexible. As modulation both QPSK and 16-QAM are taken into account. The channel coding is based on a powerful Reed–Solomon code. The control signals, sent at the beginning of the TDMA frames, with carrier-sensing based on correlation are used to detect the free time-slots. An example of the access to the network is given. Furthermore, the simulation results with a link-budget evaluation are analyzed. It is shown that the maximum data rate at 2.4 GHz, using a 16-QAM modulation can be up to 26.8 Mbit/s.