Browsing by Author "Al-Saman, Ahmed"

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    Buffer Delay Improvement in Gait-Cycle-Driven Transmission Power Control Scheme for WBAN
    (IEEE, 2020-10-08) Mohamed, Marshed; Cheffena, Michael; Ai, Yun; Al-Saman, Ahmed
    Due to the dynamic nature of the wireless body area network (WBAN) channels, there is a need for dynamic transmission power control (TPC) to increase their energy efficiency. The existing gait-cycle-driven TPC (G-TPC) successfully achieves this objective, however, it introduces maximum buffer delay equal to the period of the gait cycle. In this study, we investigate the relationship between the potential power saved and the maximum buffer delay in the G-TPC approach. A new approach is proposed based on the transmission window (instead of currently used transmission point) to reduce the maximum buffer delay by studying the received signal strength indicator (RSSI) gait patterns collected from 20 subjects. The results indicated that with a slight modification of the protocol, the same power saving can be achieved for 1.2% of the time with less than half of the maximum buffer delay. The study also indicated that, with tolerant power saving requirements, at least half of the gait channels can reduce the maximum buffer delay by more than 38%.
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    In-Body Sensor Communication: Trends and Challenges
    (IEEE, 2021-07-07) Mohamed, Marshed; Maiseli, Baraka; Ai, Yun; Mkocha, Khadija; Al-Saman, Ahmed
    Wireless body area networks (WBANs) consist of interconnected devices that monitor the human body functions and the surrounding environment. Of these sensors, implants encounter multiple challenges due to their invasive nature. In addition, the transmission channel of the implants involves living tissues that pose practical challenges in channel modeling. Despite several promising applications of implants in the healthcare industry, there have been insufficient comprehensive reviews that extensively describe trends and challenges of this technology. This work reviews in-body WBANs and presents critical challenges that hinder advancement and application of the technology. We also discuss possible solutions that may be useful to realize in-body WBANs practically.
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    Indoor Channel Estimation Using Single-Snapshot Wideband Measurement
    (IEEE, 2020-03-15) Ai, Yun; Cheffena, Michael; Mohamed, Marshed; Al-Saman, Ahmed
    The successful design of communication systems generally requires knowledge of various channel characteristic parameters. This paper utilizes the reverberation time extracted from single-snapshot wideband measurement to estimate different indoor propagation parameters based on the room electromagnetics theory. The indoor room environment is conceived as a lossy cavity that is characterized by the diffuse scattering components resulting from the surrounding walls and objects and possibly a line-of-sight (LoS) component. The main advantages of the room electromagnetics based approach are simplicity and good accuracy. The approach needs only one wideband measurement in order to extract the reverberation time in addition to some dimensional information on the investigated room to predict various important channel parameter of great importance. The measurements show good agreement with the theoretical predicted results.
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    Performance of Full-Duplex Wireless Back-Haul Link under Rain Effects Using E-Band 73 GHz and 83 GHz in Tropical Area
    (MDPI, 2020-09-03) Al-Saman, Ahmed; Mohamed, Marshed; Cheffena, Michael; Azmi, Marwan Hadri; Rahman, Tharek
    This paper presents rain attenuation effects on the performance of the full-duplex link in a tropical region based on one-year measurement data at 73.5- and 83.5-GHz E-band for distances of 1.8 km (longer links) and 300 m (shorter links). The measured rain attenuations were analyzed for four links, and the throughput degradation due to rain was investigated. The findings from this work showed that the rain attenuation for both frequencies (73.5 and 83.5 GHz) of E-band links are the same. The rain rates above 108 and 193 mm/h caused an outage for the longer and shorter links, respectively. The 73.5 and 83.5 GHz bands can support the full-duplex wireless back-haul link under rainy conditions with outage probability of 2.9×10−4 and 6×10−5 for the longer and shorter links, respectively. This work also finds that the heavy rain with rain rates above 80 mm/h for long link and 110 mm/h for short link causes about 94% and 0.90% degradation of maximum throughput. The application of these findings would help improve the architecture and service of full-duplex wireless E-band links that are established at other sites and in other tropical areas.
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    Radio Propagation Measurements in the Indoor Stairwell Environment at 3.5 and 28 GHz for 5G Wireless Networks
    (Hindawi, 2020-12-28) Al-Saman, Ahmed; Mohamed, Marshed; Cheffena, Michael
    To cover the high demand for wireless data services for different applications in the wireless networks, different frequency bands below 6 GHz and in millimeter-wave (mm-Wave) above 24 GHz are proposed for the fifth generation (5G) of communication. The communication network is supposed to handle, among others, indoor traffic in normal situations as well as during emergencies. The stairway is one of those areas which has less network traffic during normal conditions but increases significantly during emergencies. This paper presents the radio propagation in an indoor stairway environment based on wideband measurements in the line of sight (LOS) at two candidate frequencies for 5G wireless networks, namely, 3.5 GHz and 28 GHz. The path loss, root mean square (RMS) delay spread, K-factor results, and analysis are provided. The close-in free-space reference distance (CI), floating intercept (FI), and the close-in free-space reference distance with frequency weighting (CIF) path loss models are provided. The channel parameters such as the number of clusters, the ray and cluster arrival rates, and the ray and cluster decay factors are also obtained for both frequencies. The findings of the path loss show that the CI, FI, and CIF models fit the measured data well in both frequencies with the path loss exponent identical to the free-space path loss. Based on clustering results, it is found that the cluster decay rates are identical at both bands. The results from this and previous measurements indicate that at least one access point is required for every two sections of the stairway to support good coverage along the stairwell area in 5G wireless networks. Moreover, for 5G systems utilizing mm-Wave frequency bands, one access point for each stair section might be necessary for increased reliability of the 5G network in stairwell environments.
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    Wideband Channel Characterization for 6G Networks in Industrial Environments
    (MDPI, 2021-03-12) Al-Saman, Ahmed; Mohamed, Marshed; Cheffena, Michael; Moldsvor, Arild
    Wireless data traffic has increased significantly due to the rapid growth of smart terminals and evolving real-time technologies. With the dramatic growth of data traffic, the existing cellular networks including Fifth-Generation (5G) networks cannot fully meet the increasingly rising data rate requirements. The Sixth-Generation (6G) mobile network is expected to achieve the high data rate requirements of new transmission technologies and spectrum. This paper presents the radio channel measurements to study the channel characteristics of 6G networks in the 107–109 GHz band in three different industrial environments. The path loss, K-factor, and time dispersion parameters are investigated. Two popular path loss models for indoor environments, the close-in free space reference distance (CI) and floating intercept (FI), are used to examine the path loss. The mean excess delay (MED) and root mean squared delay spread (RMSDS) are used to investigate the time dispersion of the channel. The path loss results show that the CI and FI models fit the measured data well in all industrial settings with a path loss exponent (PLE) of 1.6–2. The results of the K-factor show that the high value in industrial environments at the sub-6 GHz band still holds well in our measured environments at a high frequency band above 100 GHz. For the time dispersion parameters, it is found that most of the received signal energy falls in the early delay bins. This work represents a first step to establish the feasibility of using 6G networks operating above 100 GHz for industrial applications.