Browsing by Author "Sheikh, Muhammad Usman"
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Item Adaptive Physical Layer Selection for Bluetooth 5: Measurements and Simulations(John Wiley and Sons Ltd, 2021-01-06) Sheikh, Muhammad Usman; Badihi, Behnam; Ruttik, Kalle; Jäntti, Riku; Department of Communications and Networking; Communication Engineering; Wireless & Mobile CommunicationsThe main target of this article is to propose a simple Received Signal Strength Indicator- (RSSI-) based adaptive Physical Layer (PHY) selection approach for Bluetooth Low Energy 5.0 (BLE 5) and compare the performance of adaptive PHY selection with the performance of individual PHY. This article also validates the simulation results acquired from the in-house developed Ray Tracing (RT) tool with the BLE 5 measurements conducted in a corridor of the TUAS building, Aalto University. The performance metrics considered for the analysis are RSSI, throughput, and outage ratio. The impact of different transmission power on BLE 5 is also analyzed. The obtained simulation results indicate a Root Mean Square Error (RMSE) of about 4.6 dB between the measured and the simulated RSSI at 2.4 GHz frequency. By investigating these results, an adaptive PHY selection algorithm is proposed in this article. The adaptive PHY selection approach enhances the mean throughput of the system and improves the outage ratio as well. In the light of acquired results, the adaptive PHY selection scheme shows significant performance gain and is found more beneficial in the case of an environment with mixed RSSI samples, i.e., a mix of low and high RSSI values.Item Analysis of Drone Propagation with Ray Tracing from Sub-6 GHz Upto Terahertz Frequencies in a Real World Urban Environment(2021-01-13) Sheikh, Muhammad Usman; Ruttik, Kalle; Saba, Norshaida; Mutafungwa, Edward; Jantti, Riku; Hamalainen, Jyri; Department of Communications and Networking; Communication Engineering; Wireless & Mobile CommunicationsUnmanned aerial communication platforms have been recently considered as an effective solution to provide homogeneous and extended network coverage to terrestrial users. Unmanned Aerial Vehicles (UAVs) are expected to increase the network reliability and users' Quality of Experience (QoE). The first target of this paper is to analyze the propagation characteristics of drone transmission at different frequencies i.e., 3.5 GHz, 28 GHz, 60 GHz, and up to 180 GHz with 20GHz step. In the considered setup drone is flying at different heights i.e., from 50m up to 250m altitude and we carry out 3D ray tracing simulations assuming a propagation environment that is defined by the real building data from Helsinki city. Ground users are placed outdoors. We study the validity of a previously proposed geometrical Line of Sight (LOS) probability model between ground user and drone, and based on simulations we propose new modeling parameters. In the second part of the paper, the ray tracing results are compared with the analytical reference model. Finally, a new set of parameters is proposed for tuned analytical model based on acquired ray tracing results. The proposed analytical model provides significantly low Root Mean Square Error (RMSE) when compared with the analytical reference model.Item Arguments for One Radio Access Network (OneRAN) mobile infrastructure(Springer Netherlands, 2022) Sheikh, Muhammad Usman; Lempiainen, Jukka; Jäntti, Riku; Department of Communications and Networking; Communication Engineering; Tampere UniversityThe frequency spectrum is a scarce resource, and is owned and regulated by the state to ensure its efficient and fair utilization. All over the world, a large number of Mobile Network Operators (MNOs) are already involved in either active or passive Radio Access Network (RAN) sharing to maximize cost savings. The aim of this article is to challenge the ownership of individual operator’s infrastructure and present technical arguments for One Radio Access Network (OneRAN) approach for deploying a cellular network. The enormous increase in data traffic and regulatory requirements concerning public safety communications provide the basis for migrating to OneRAN infrastructure. The OneRAN approach provides an opportunity to gain technological benefits and helps in meeting the requirements of critical communication. OneRAN targets to maximize the savings on capital and operational expenses. The main focus of this work is outdoor wide-area coverage i.e., outdoor users in rural areas and on highways, as it is assumed that indoor service provision in the future requires a dedicated indoor solution. For the research work of this article, a measurement campaign was launched and different Key Performance Indicators(KPIs) of Long Term Evolution(LTE) technology for three commercial MNOs of Finland were measured over a 52 km highway from Iittala to Tampere city. The acquired results highlight the gain of OneRAN infrastructure as it enhanced the user quality of experience i.e., user throughput, especially of the critical cell border users, and improved the overall system performance economically. Finally, supportive arguments are presented for having a OneRAN infrastructure specifically over the highways.Item Artificial Rich Scattering-Assisted MIMO Systems Using Passive Backscatter Devices(2022) Al-Nahari, Azzam; Jantti, Riku; Sheikh, Muhammad Usman; Department of Communications and Networking; Communication EngineeringReconfigurable intelligent surfaces (RIS) are emerging as a promising technology for the future 6G networks. One of the challenges of IRS systems is that they require feedback control which in turn means that they have to have receiver and microcontroller that consume power. In this paper, we propose to use passive chipless backscatter devices to shape the channel between the transmitter and the receiver. We propose a novel artificial rich scattering (ARS)-assisted MIMO system, that uses passive chipless backscatter devices to shape the channel covariance matrix by increasing its rank even if the direct transmission channel has strong line-of-sight (LoS) component. In particular, we conduct a large system analysis and show that the achievable rate is independent of the phase shift matrix at the backscattering nodes. Moreover, by introducing large number of passive scattering elements in the system, we can improve the system capacity even with the presence of strong LoS component in MIMO channel. We also consider the case of ARS-assisted MISO case when the channel state information (CSI) is available at the transmitter side and derive tight lower bound on the ergodic rate.Item Assessment of coordinated multipoint transmission modes for indoor and outdoor users at 28 GHz in urban macrocellular environment(ASTES Publishers, 2019-01-01) Sheikh, Muhammad Usman; Biswas, Ritayan; Lempiainen, Jukka; Jantti, Riku; Department of Communications and Networking; Communication Engineering; Tampere UniversityThe aim of this article is to analyze and evaluate the performance of Coordinated Multipoint (CoMP) transmission approach at a frequency of 28 GHz using three dimensional ray tracing simulations in an urban macrocellular environment. The new performance metric introduced in this article is the relative power usage. Other performance metrics examined in this article are received power, the Signal to Interference plus Noise Ratio (SINR), user throughput, relative throughput gain, and the percentage of overlapping area with multiple cells. Indoor and outdoor users are separately analyzed for few key performance indicators. Different cases of coordinated multipoint transmission i.e. intra-node and inter-node coordination is analyzed. The post analysis of the acquired simulation data shows that the use of CoMP functionality is more beneficial for the cell edge users compared with the other users in terms of improving the user’s experience. The throughput gain as well as the transmission overhead of the CoMP approach increases with the increase in number CoMP ports. Inter-node CoMP is much more power efficient and beneficial in comparison with the intra-node CoMP case.Item Capacity Limitation of Small Cell Densification(2022) Sheikh, Muhammad Usman; Lempiainen, Jukka; Jantti, Riku; Department of Communications and Networking; Communication Engineering; Tampere UniversityDeployment of small cells is considered as an easy approach for adding capacity to the system. However, it is important to realize that in a non-noise limited system, each additional cell increases the interference in the system. The target of this paper is to show the capacity limitation of the cellular network with an increasing number of small cells in a network. Ultra-dense deployment of small cells implies a high probability of line of sight (LOS) transmission between the transmitter (TX) and receiver (RX). The LOS transmission helps in enhancing the received signal strength, whereas, on the other hand, the interference power significantly grows with small cell densification. This paper presents the analytical analysis of bad cell border area for one-, and two-dimensional grid of small cells. The lamp post solution for the small cell deployment along the street is studied through simulations. The acquired results show that the overall interference in the system and the bad signal to interference plus noise ratio (SINR) cell border area grows with cell densification. System capacity saturates and then starts to collapse as the capacity loss due to the additional cell interference becomes dominant over the gain of cell densification after the saturation point.Item Channel Characterization at Sub-THz Band with Measurements and Ray Tracing in Indoor Case(2023-02-22) Sheikh, Muhammad Usman; Ali, Muhsin; Carpintero, Guillermo; Ruttik, Kalle; Mutafungwa, Edward; Jantti, Riku; Department of Information and Communications Engineering; Department of Communications and Networking; Communication Engineering; Universidad Carlos III de MadridUltra-wide bandwidth (BW) available at terahertz (THz) and sub-THz frequencies makes these bands interesting for wireless communication systems. A large BW at the sub-THz frequency band offers a promising solution for applications with short-range and high data rate requirements. Since the provision of high-speed computational systems, deterministic channel models have been extensively used for indoor field prediction and radio channel characterization, especially for high frequencies i.e., millimeter wave (mmWave) and sub-THz frequencies. We have developed an in-house built ray tracing (RT) tool, capable of characterizing a radio channel with good accuracy and precision. The aim of this paper is to validate the power angular spectrum (PAS) acquired through our RT tool with the measurement data at sub-THz frequencies of 90, 95, and 100 GHz, in both line-of-sight (LOS) and non-LOS (NLOS) University corridor environment. A photonics-based measurement setup with high accuracy is utilized for generating the sub-THz signal, and for acquiring the measurement data. In addition to the PAS, other channel metrics considered for the analysis through RT simulations are root mean square delay spread (RMS-DS) and RMS angular spread (RMS-AS) in an azimuth plane. The results presented in this paper show that our in-house built RT is capable of providing considerably good agreement between the measured and simulated PAS in both LOS and NLOS states.Item Dual connectivity in non-stand alone deployment mode of 5G in Manhattan environment(2020-01) Sheikh, Muhammad Usman; Asghar, Muhammad-Zeeshan; Jantti, Riku; Department of Communications and Networking; Communication EngineeringThe main target of this paper is to analyze the performance of an outdoor user in a dense micro cellular Manhattan grid environment using a ray launching simulation tool. The radio propagation simulations are performed using a Shoot and Bouncing Ray (SBR) method. The network performance is analyzed at three different frequencies i.e. 1.8 GHz, 3.5 GHz, and 28 GHz. Additionally, the benefits of combining LTE and potential 5G frequency bands by using feature of Dual Connectivity (DC) in an outdoor scenario has been highlighted. The considered performance metrics are received signal level, SINR, application throughput. The acquired simulation results from Manhattan canyon street environment reveal that a good 5G outdoor coverage can be provided at 3.5 GHz and 28 GHz while using existing 4G micro sites. The impact of Dual Connectivity at user's throughput is studied in this article, and it is shown user throughput can be doubled by leveraging the benefits of LTE and 5G NR together.Item Impact of Interference Suppression under Ray Tracing and 3GPP Street Canyon Model(2020-05) Sheikh, Muhammad Usman; Jantti, Riku; Hamalainen, Jyri; Department of Communications and Networking; Communication Engineering; Wireless & Mobile CommunicationsChannel models are routinely used for evaluating the performance of wireless technologies and cellular networks. An appropriate channel model is necessary for a credible system analysis, and the shortcomings in the channel model may lead to erroneous conclusions. In this paper we characterize the impact of Interference Suppression (IS), Interference Cancellation (IC) and interference management on the system performance when using a) the 3rd Generation Partnership Project (3GPP) street canyon model (TR 38.901, Release 14), b) Shoot and Bouncing Ray (SBR) method based Ray Tracing (RT) model, and c) a proposed large scale path loss model in an urban, so-called Manhattan building grid environment. Simulations are performed using the 28 GHz carrier frequency that has been recently considered for the 5th Generation (5G) networks. Simulation results indicate that the 3GPP channel model provides slightly pessimistic path loss values than RT in Line of Sight (LOS) conditions, whereas in Non-LOS (NLOS) situation it gives a considerable pessimistic path loss estimation as compared with the deterministic RT approach. The difference between channel models is notable especially for the estimation of Signal to Interference plus Noise Ratio (SINR). Since RT provides realistic results due to accurate radio environment and signal modeling and, on the other hand, the correct SINR estimation is crucial for the wireless system evaluation. Our proposed path loss model is based on RT simulations. The performance of the proposed model for different performance metrics matches well with the RT results.Item Link Budget Validation for Backscatter-Radio System in Sub-1GHz(2019-04-01) Badihi, Behnam; Liljemark, Aleksi; Sheikh, Muhammad Usman; Lietzen, Jari; Jantti, Riku; Department of Communications and Networking; Communication Engineering; Communications Theory; Department of Communications and NetworkingAmbient backscatter communications system (ABCS) has recently been introduced as a cutting edge technology in which devices communicate in wireless mode by exploiting ambient radio frequency (RF) signals instead of actively generating them. ABCS is a promising technology for Internet of Things (IoT) use cases in which the power efficiency is a major challenge yet to be addressed. ABCS is in its early development stages from theoretical and practical perspectives. In this regard, it is highly important to understand the multi-aspects of the link budget of ABCS. Hence, in this paper we conducted a comprehensive study including measurements in different propagation environment and thorough simulation. The measurements are preformed in sub-1 GHz band and particularly in 590 MHz with the tags designed in the house. The results confirm the match between measurements and the simulations with trivial error.Item Polarization adaptation to improve cell border area bitrates and system capacity in small cells(Springer, 2023-12-28) Lempiäinen, Jukka; Sheikh, Muhammad Usman; Asp, Ari; Jäntti, Riku; Department of Information and Communications Engineering; Communication Engineering; Tampere UniversityThe target of this paper is to show the impact of polarization adaptation on the received signal quality in an outdoor small-cell deployment scenario. The signal-to-interference ratio (SIR) is the key factor in defining the achievable data rate, and the capacity of the cell. At the cell border area, the SIR value is typically low and causes a significant decrease in the system capacity and achievable data rates. These bad SIR areas at the cell border can be improved by using orthogonal polarizations in the neighboring cells rather than using all polarizations over the whole cell coverage area. For the research work of this paper, a series of measurements were carried out to measure a received signal power and a cross polarization discrimination (XPD) ratio while the signal is transmitted and received with a different set of polarizations. In the measurements, we have considered horizontal, vertical, +/− 45° slanted polarizations, and two different environments, urban street and open space, and three frequency bands, 970−1030 MHz, 2000−2030 MHz and 3364−3400 MHz. The measurement results revealed that at a different distance from the transmitter, for horizontal/vertical polarization, the average XPD is around 24.7 dB and 31.7 dB in the urban street and open area environments, respectively. For +/− 45° slanted polarization, the average XPD is around 11.5 dB and 12.1 dB in the urban street and open area environments, respectively. This paper goes on to propose polarization adaptation in each cell, where the primary polarization is valid for the whole service area of the cell, and secondary polarization is only used in close proximity of the base station antenna. Considering the results, it is emphasized that system capacity can be significantly improved by having only one channel with good SIR values compared to multiple channels with bad SIR values. However, MIMO channels with orthogonal polarizations or with spatial multiplexing can be utilized in the closed vicinity of the base station, i.e., in an area with good SIR values. It is shown that the overall cell capacity can be increased by almost 35% by utilizing polarization adaptation compared to MIMO 2 × 2.Item Power Angular Measurements and Ray Tracing Simulations at Sub-THz Frequencies in Corridor(2022) Sheikh, Muhammad Usman; Ali, Muhsin; Carpintero, Guillermo; Ruttik, Kalle; Mutafangwa, Edward; Jantti, Riku; Department of Communications and Networking; Communication Engineering; Universidad Carlos III de MadridUltra-wideband terahertz (THz) wireless communication systems are anticipated as a promising solution for applications with high bandwidth requirements in an indoor environment. To design the communication system operating at THz or sub-THz frequencies, it is important to acquire fundamental knowledge about the radio propagation characteristics at those frequencies. The main target of this paper is to conduct power angular spectrum (PAS) measurements at sub-THz frequencies of 90, 95, and 100 GHz in a line-of-sight (LOS) office corridor environment, and validate the ray tracing (RT) simulation results with the measurements. A sophisticated photonics-based measurement setup with high accuracy is utilized for measurement, whereas, an in-house built RT tool is used for simulation. The PAS is measured and simulated at eight different locations and a decent agreement is achieved between both. Whereas the other channel characteristics like root mean square delay spread (RMS-DS) and angular spread (RMS-AS) are only investigated through RT simulations. In the case of direct orientation, the root mean square error of about 1.5, 0.9, and 3.7 dB is found between the measured and simulated received signal power level at 90, 95, and 100 GHz, respectively.Item Quality-aware trajectory planning of cellular connected UAVs(2020-09-25) Sheikh, Muhammad Usman; Riaz, Maria; Jameel, Furqan; Jäntti, Riku; Sharma, Navuday; Sharma, Vishal; Alazab, Mamoun; Department of Communications and Networking; Department of Electronics and Nanoengineering; Communication Engineering; Network Security and Trust; Charles Darwin UniversityThe use of Unmanned Aerial Vehicles (UAVs) is becoming common in our daily lives and cellular networks are effective in providing support services to UAVs for long-range applications. The main target of this paper is to propose a modified form of well-known graph search methods i.e., Dijkstra and A-star also known as Aalgorithm, for quality-aware trajectory planning of the UAV. The aerial quality map of the propagation environment is used as an input for UAV trajectory planning, and the quality metric considered for this work is Signal to Interference plus Noise Ratio (SINR). The UAV trajectory is quantified in terms of three performance metrics i.e., path length, Quality Outage Ratio (QOR), and maximum Quality Outage Duration (QOD). The proposed path planning algorithm aims at achieving a trade-off between the path length and other quality metrics of the UAV trajectory. The simulations are performed using an agreed 3GPP macro cell LOS scenario for UAVs in MATLAB. Simulation results illustrate that the proposed algorithm significantly improves the QOR by slightly increasing the path length compared with the naive shortest path. Similarly, the outage avoidance path achieves high QOR at the expense of large path length, and our proposed method finds a compromise and provides an optimal quality-aware path.Item A study about signal variation with minor receiver displacement in a meeting room at 60 GHz: measurements and simulations(SPRINGER PUBLISHING COMPANY, 2021-12) Sheikh, Muhammad Usman; Ruttik, Kalle; Jäntti, Riku; Hämäläinen, Jyri; Department of Communications and Networking; Communication Engineering; Wireless & Mobile CommunicationsThe aim of this work is to study the impact of small receiver displacement on a signal propagation in a typical conference room environment at a millimeter wave frequency of 60 GHz. While channel measurements provide insights on the propagation phenomena, their use for the wireless system performance evaluation is challenging. Whereas, carefully executed three-dimensional ray tracing (RT) simulations represent a more flexible option. Nevertheless, a careful validation of simulation methodology is needed. The first target of this article is to highlight the benefits of an in-house built three-dimensional RT tool at 60 GHz and shows the effectiveness of simulations in predicting different characteristics of the channel. To validate the simulation results against the measurements, two different transmitter (Tx) positions and antenna types along with ten receiver (Rx) positions are considered in a typical conference room. In first system configuration, an omnidirectional antenna is placed in the middle of the table, while in the second system configuration a directed horn antenna is located in the corner of the meeting room. After validating the simulation results with the measurement data, in the second part of this work, the impact of a small change, i.e., 20 cm in the receiver position, is studied. To characterize the impact, we apply as performance indicators the received power level, root mean square delay spread (RMS-DS) and RMS angular spread (RMS-AS) in azimuth plane. The channel characteristics are considered with respect to the direct orientation (DO), i.e., the Rx antenna is directed toward the strongest incoming path. Different antenna configurations at the Tx and Rx side are applied to highlight the role of antenna properties on the considered channel characteristics. Especially, in the second system configuration the impact of different antenna half power beamwidth on different considered channel characteristics is highlighted through acquired simulation results. The validation of results shows the RMS error of only 2–3 dB between the measured and simulated received power levels for different Tx configurations in the direction of DO. Results indicate that only a small change of the Rx position may result a large difference in the received power level even in the presence of line-of-sight between the Tx and Rx. It is found that the STD of received power level across the room increases with the decrease in HPBW of the antenna. As can be expected, directed antennas offer lower value of RMS-DS and RMS-AS compared with isotropic antenna.Item Ultra-low-power wide range backscatter communication using cellular generated carrier(Multidisciplinary Digital Publishing Institute (MDPI), 2021-04-02) Sheikh, Muhammad Usman; Xie, Boxuan; Ruttik, Kalle; Yiğitler, Hüseyin; Jäntti, Riku; Hämäläinen, Jyri; Department of Communications and Networking; Communication Engineering; Wireless & Mobile CommunicationsWith the popularization of Internet-of-things (IoT) and wireless communication systems, a diverse set of applications in smart cities are emerging to improve the city-life. These applications usually require a large coverage area and minimal operation and maintenance cost. To this end, the recently emerging backscatter communication (BC) is gaining interest in both industry and academia as a new communication paradigm that provides high energy efficient communications that may even work in a battery-less mode and, thus, it is well suited for smart city applications. However, the coverage of BC in urban area deployments is not available, and the feasibility of its utilization for smart city applications is not known. In this article, we present a comprehensive coverage study of a practical cellular carrier-based BC system for indoor and outdoor scenarios in a downtown area of a Helsinki city. In particular, we evaluate the coverage outage performance of different low-power and wide area technologies, i.e., long range (LoRa) backscatter, arrow band-Internet of Things (NB-IoT), and Bluetooth low energy (BLE) based BC at different frequencies of operation. To do so, we carry out a comprehensive campaign of simulations while using a sophisticated three-dimensional (3D) ray tracing (RT) tool, ITU outdoor model, and 3rd generation partnership project (3GPP) indoor hotspot model. This study also covers the energy harvesting aspects of backscatter device, and it highlights the importance of future backscatter devices with high energy harvesting efficiency. The simulation results and discussion provided in this article will be helpful in understanding the coverage aspects of practical backscatter communication system in a smart city environment.Item X-Haul Solutions for Different Functional Split Options Using THz and Sub-THz Bands(2022-10-24) Sheikh, Muhammad Usman; Ruttik, Kalle; Mutafungwa, Edward; Jäntti, Riku; Hamalainen, Jyri; Yusta Padilla, Eduardo; Department of Communications and Networking; Communication Engineering; Wireless & Mobile Communications; TelefonicaIn a variety of scenarios, from temporal events to emergencies, mobile cell also known as cell on wheels (COW) or cell on light truck (COLT) is considered as a widespread solution for temporarily increasing the capacity of the cellular networks. Flying cells are small-sized, low-cost, fast deployment options of mobile cells. In the fifth generation (5G) of cellular systems, the functionalities of radio access network (RAN) components i.e., centralized unit (CU), distributed unit (DU), and radio unit (RU) vary in different functional splits and thus have different data rate requirements for the interfaces between the units. The initial target of the paper is to provide a basic overview of different functional splits introduced in 5G, and highlight the throughput requirements of the transport X-Haul links of those functional splits. Moreover, the target is to investigate the option of utilizing terahertz (THz) and sub-THz wireless radio link to meet a high data rate requirement. In this work, we considered two frequency bands i.e., 105 GHz and 220 GHz, and estimated the handling capacity of the X-Haul link for different supporting bandwidths and distances. The X-Haul link capacity requirements also depend upon the air interface configuration, therefore, in this work different bandwidths, the number of antennas, and MIMO layer configurations are considered. The analysis is applicable for the terrestrial as well as for the flying platforms. Interestingly, it is found that with a lower functional split i.e., split 8, the X-Haul data requirement is above 150 Gbps for a simple 5G system with only 100 MHz bandwidth and 32 antennas.