Abstract The aim of this paper is to define new uncorrelated propagation channels for Multiple-Input-Multiple-Output (MIMO) purposes by producing angular phase differences in the transmission. The phase difference can be created such that the radiation power of the signal does not change when selecting correct values for real and imaginary parts of the complex value $$a+jb$$ . This results in the same signal amplitudes, i.e., coverage area or antenna power radiation pattern, but multi path signal components are received with phase differences. These phase differences then allow uncorrelated propagation channels to be used in MIMO N $$\times $$ N. In 5G/6G mobile networks, mostly only line-of-sight (LOS) connections between base stations and mobiles are available at very high frequencies, and small cell implementations with MIMO are needed to maximize the system capacity. However, MIMO has performance limitations in LOS environments due to lacking the required phase difference between MIMO channels when traditional antenna space separation is used. Thus, these new uncorrelated channels are especially needed in high-capacity small cell implementations but also in nearly LOS-type environments, as on highways. Ray-tracing simulations were done at 28 GHz frequency in a small cell LOS environment to show the impact of angular phase differences. Fast fading statistics and signal cross-correlations were analyzed to see the potential of utilizing MIMO N $$\times $$ N in LOS propagation paths. MIMO system capacities were calculated for different MIMO configurations, and these results were compared with the results of traditional spatially separated configurations. The simulated results showed that sufficient angular phase difference offers independent propagation channels in a small cell LOS environment with cross-correlation factors of 0.01–0.44. These low correlated propagation channels yielded a capacity increase of 3.44–3.88 times from SISO to MIMO 4 $$\times $$ 4 with one polarization and with different directional antennas. This capacity was even 95 % higher than the capacity with only spatially separated directional antennas.

Abstract The 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.

The purpose of this paper is to estimate the maximum achievable range for ambient backscattering communications (AmBC) by utilizing one of the lowest available frequency bands for mobile networks. Long term evolution (LTE) networks operating at 700 MHz (LTE-700, also referred to as LTE band 28) use the frequency division duplexing (FDD) technique for communications and are utilised as the ambient signals to perform the simulations. The simulations are carried out in urban macro-cellular and suburban highway environments. For the simulations, the sensors are placed in the line-of-sight (LOS) path of the LTE-700 transmitter and receiver antenna as this ensures the maximum applicability of the AmBC technology. Two propagation models, the ray tracing approach and the radar equation are leveraged to determine the maximum range of communication when the signal is reflected by the sensor. It is observed from the analysis that distances of a few hundred meters are achievable utilising both propagation models. The size of the sensor has a pivotal role in determining the maximum range of communication while utilising the radar equation. Therefore, a thorough analysis is performed using real-world sensor sizes deployed for the internet of things (IoT) wireless communication.

The ambient backscatter communication (AmBC) system utilizes the existing ambient RF signals present in the atmosphere for backscattering the signal. One of the challenges for AmBC system is the interference at the receiver module caused by the direct path signal from the ambient source. The purpose of this paper is to study the coverage aspects of the bi-static backscatter communication system in a typical urban environment at sub-1GHz frequencies using simulations in MATLAB. For the simulation, 3rdgeneration partnership project (3GPP) urban microcellular and international telecommunication union (ITU) device-to-device (D2D) propagation models are used. Moreover, the dynamic range i.e., the difference in the received power level of the direct path and the backscatter path is investigated. For correctly decoding the backscatter signal at the reader, the target value set for the dynamic range is less than 30 dB. This paper studies the importance of direct path interference suppression for the successful deployment of a bi-static backscatter communication system.

Abstract The aim of this article is to evaluate the applicability of 5G technology as a possible ambient signal for backscattering communications (AmBC). This evaluation considers both urban macro-cellular, small cell as well as rural highway environments. The simulations are performed in outdoor areas including analysis about 5G implementation strategies in different scenarios. Essential aspects of 5G radio network topology such as frequency domain (3.5 GHz and 26 GHz) and antenna locations (offering line-of-sight, LOS) are highlighted and turned to applicability scenarios with AmBC. The LOS scenarios are evaluated to determine the widest applicability area of 5G for AmBC. Typical AmBC applications are studied including collection of data from several sensors to receivers. Evaluation of the applicability of 5G was based on propagation related simulations and calculations utilising the ray tracing technique and the radar equation. The results demonstrate that 5G can be used as an ambient signal for backscattering communications for short ranges for typical sensor sizes. It is also observed that the range of communication is heavily dependent on the the size of the sensor.

The main target of this paper is to evaluate the performance of Coordinated Multipoint (CoMP) transmission technique at Millimeter Wave (mmWave) frequency through a comprehensive set of simulations. A new metric for the performance evaluation of CoMP functionality called the Net CoMP utilization gain is introduced in this paper that takes into account the expected loading of the coordinating cells. Other performance metrics considered are the Signal to Interference plus Noise Ratio (SINR), throughput and dominance area. The acquired results show that the adoption of CoMP functionality provides higher gain in improving the Quality of Service (QoS) for the cell edge users compared with the other users. The net CoMP utilization gain as well as the overhead increases with the increase in number of transmission points (TPs). However, in highly loaded networks the risk of having negative impact (capacity loss) also increases with the increase in number of transmission points.

The main target of this research work is to study the provision of indoor service (coverage) using outdoor base stations at higher frequencies i.e. 10 GHz in the context of a single building scenario. In an outdoor to indoor propagation, an angular wall loss model is used in the General Building Penetration (GBP) model for estimating the additional loss at the intercept point of the building exterior wall. A novel angular wall loss model based on a separate incidence angle in azimuth and elevation plane is proposed in this paper. In the second part of this study, an Extended Building Penetration (EBP) model is proposed, and the performance of EBP model is compared with the GBP model. In EBP model, the additional fifth path known as the “Direct path” is proposed to be included in the GBP model. Based on the evaluation results, the impact of the direct path is found significant for the indoor users having the same or closed by height as that of the height of the transmitter.

The main target of this paper is to perform the multidimensional analysis of multipath propagation at higher frequencies i.e. 15 GHz and 28 GHz, using “sAGA” a 3D ray tracing tool. A real world outdoor Line of Sight (LOS) microcellular environment from the Yokusuka city of Japan is considered for the analysis. The simulation data acquired from the 3D ray tracing tool includes the received signal strength, power angular spectrum and the power delay profile. The different propagation mechanisms were closely analyzed. The simulation results show the difference of propagation at two frequencies i.e. 15 GHz and 28 GHz and draw a special attention on the impact of diffuse scattering at 28 GHz. In a simple outdoor microcellular environment with a valid LOS link between the transmitter and a receiver, a path loss difference of around 5.7 dB was found between 15 GHz and 28 GHz frequency of operation. However, the propagation loss at higher frequency can be compensated by using the antenna with narrow beamwidth and larger gain.

The aim of this study is to analyze how cellular network subscribers behave during an electricity network disturbance situation. Furthermore, removing the effect of randomly accessing the network could improve especially the speech capacity during these events. When part of the mobile network is unavailable, the availability of the cellular network services decreases. However, the subscribers have increased demand for services during disturbance scenarios since they fetch information from the Internet and try to contact their family and friends. The analysis in this paper shows that even an uncommon power blackout resulted in an increase of 73 % in new calls and 84 % in the number of short message service (SMS) demand for mobile network services in a rural area.

The power levels of cellular network User Equipment (UE) may vary considerably in both the receiver and the transmitter side, especially in indoor locations. With an indirect guidance method, the users are self-optimizing their UE to a better location with the help of an application. Thus, the user distribution is weighted more on high quality connection areas, which results in saving the UE batteries and reducing the overall radiation. This power reduction can also be understood as a capacity increase, especially in radio networks based on Code Division Multiple Access (CDMA), such as the Universal Mobile Telecommunications System (UMTS) technology. The aim of this paper is to show the possibility and the opportunity to save energy or to increase the capacity in cellular networks when the users are indirectly guided to optimize their UE locations. In this study, energy and capacity optimization is verified for residential indoor users in the measurements where the users are served by signals coming from several outdoor Base Stations (BSs) in a typical urban environment. The results obtained show that a path loss (PL) improvement of up to 10-25 dB can be achieved when the user locations are optimized and the signals are coming from the outdoor BSs.

Data traffic has significantly increased in the past years, and it is expected to grow even at higher pace. Long Term Evolution (LTE) technology and the concept of Dual-Cell High Speed Downlink Packet Access (DC-HSDPA) were introduced to serve the data users. The target of this paper is to analyse the impact of serving variable number of users per Transmission Time Interval (TTI) on the performance of LTE along with different antenna configuration and DC-HSDPA system with and without Power Control (PC). In this paper average cell throughput, relative throughput gain, and user's probability of no data transfer with different Intersite Distance (ISD) was analyzed in macro cellular environment. Simulation results revealed that average cell throughput decreases with the increase in both ISD and active number of users per TTI. But, LTE throughput was found to be more sensitive with the change in ISD, whereas DC-HSDPA throughput affects more with the change in serving number of users per TTI. DC-HSDPA with PC was found to offer lower probability of no data transfer compared to LTE regardless of ISD and active number of users.

In a race towards 4G technologies, future cellular network like Long Term Evolution (LTE) is competing with high data rates and improved spectrum efficiency. The target of this paper is to evaluate performance of Adaptive MIMO Switching (AMS) in LTE in terms of cell throughput and throughput gain with respect to other antenna configuration. The impact of different intersite distance on the performance of AMS was also investigated in this paper. The assessment was based on simulations using analytical channel model. Kronecker channel model without any Channel State Information (CSI) at transmitter was used for the simulation purposes. Adaptive MIMO switching works on the principle of switching among transmit diversity, receive diversity, and spatial multiplexing in accordance to SINR level. Simulation results reveal that significant improvement in cell throughput can be achieved by applying AMS technique. However, utilization of standard MIMO transmission techniques also improves channel capacity.

The aim of this paper is to analyze the impact of smart traffic handling scheme in managing the radio resources among different layers of the multilayer network. Impact of smart traffic handling scheme on loading of GSM900/1800 layers along with UMTS900/2100 layers was observed. The capacity of UMTS network is known to be interference limited. Interference margin is introduced in UMTS link budget as system parameter, to account for the system degradation. Interference margin is directly proportional to the uplink loading of the cell. In this paper, impact of smart traffic handling scheme was also observed on interference margin, provided only in the UMTS link budget. Smart traffic handling scheme is compact and intelligent traffic handling scheme, and it is based on distance of the user from base station and required service type. The idea of GSM900 and UMTS900 as an overlay with GSM1800 and UMTS2100 as an underlay was maintained by smart traffic handling scheme.

ABSTRACT The aim of this paper is to analyze the impact of smart traffic handling scheme in managing the radio resources among the different layers of multimode multiband radio network. The impact of two different traffic handling schemes on loading of GSM900/1800 layers along with Universal Mobile Telecommunications System (UMTS) 900/2100 layers was observed. Interference margin is introduced in the UMTS link budget as a system parameter that will account for systems degradation. One of the targets of this massive simulation campaign was to observe the impact of smart traffic handling scheme on interference margin. Network performance was analyzed with different interference factors. Results presented in this paper show that 1–2.5 dB of interference margin can be reduced for UMTS coverage layer and that 5–22% of UMTS capacity layer utilization can be improved. Significant improvement in speech blocking probability was observed because of optimized load balancing among the layers. UMTS base station power was effectively used by restraining the speech users from using the power resources of UMTS layers. Finally, the simulation results revealed the importance of deploying UMTS900 in a multilayer network. The suggested traffic handling scheme is compact and intelligent scheme, and it is based on distance of the user from the base station and required service type. Copyright © 2011 John Wiley & Sons, Ltd.

This paper discusses essential implementation aspects of simple amplify-and-forward type repeaters from the radio network planning point of view. Different RF-repeater configurations are assessed through numerical analysis and field measurements in WCDMA network. The target of this paper is to show the important factors regarding the repeater deployment, which have significant impact on the overall cellular network efficiency. The paper shows the impact of repeater donor antenna beam width on the repeater deployment flexibility. Moreover, the impact of repeater on the optimum BS antenna tilt angle is presented using two macrocellular topologies. Finally, the significance of repeater placement in the repeater antenna line is emphasized through field measurements using an outdoor-to-indoor repeater configuration for WCDMA.

The target of the paper is to study the impact of antenna- and cell configuration of a single high altitude platform (HAP) station on the overall network performance point of view. In the studied approach, one HAP station alone provides UMTS services to terrestrial mobile users. Large number of different antenna and cell configurations has been simulated with a system level Monte Carlo WCDMA simulator. The results emphasize the differences between of the used antenna- and cell configurations. The optimum performance was achieved by using antennas with 2 degree beam width and 6 tiers of cells for the reference location. The overall service probability with high number of users varied from 42 % to 95 %, when the antenna- and cell configuration were updated from the worst to the optimum one. The results of this paper will give some guidelines for the HAP antenna- and cell configuration planning, and emphasize the importance of proper radio network planning when targeting to maximum system performance.

The aim of this paper is to evaluate the impact of selected topology planning aspects on performance of WCDMA cellular network and mobile positioning techniques. The assessment is based on field measurements and simulations. Capacity improvement is illustrated for the network topology when antenna down tilt, sectoring, and repeaters are considered. In turn, two network-based location methods (CID+RTT and PCM) are selected for evaluation of the accuracy in a radio environment optimized for the maximum capacity. Presented results yield for a compromise if both, radio capacity and the CID+RTT, are aimed to be maximized through antenna down tilting and sectoring. On the other hand, topology optimization through repeater deployment improves the positioning accuracy as well. Considered topology optimization methods affect the PCM accuracy when the underlying database is intended to operate in a non-optimized topology, however the mean value of the accuracy is still on an appropriate level.

The target of the paper is to study performance of HSDPA in indoor environment, and to provide guidelines for HSDPA coverage and capacity planning and antenna configurations selection. Field measurements with a HSDPA data card, field measurement software, and a fully functional HSDPA enabled UMTS network were performed. Indoor corridor environment was used to study the impact of different distributed antenna configurations on a HSDPA performance. In addition, pico cell configuration is compared to corresponding distributed antenna configuration, and the effect of coverage limitations on HSDPA capacity is studied. The results show, that ensuring sufficient coverage is the key factor in planning HSDPA indoor network. Signal quality can be enhanced by increasing the number of antennas in DAS, which is also visible as improved capacity. Better signal level can be achieved by pico base stations, but taking benefit of added capacity is problematic. The measurement results show that distributed antenna configuration provides better performance compared to pico cells. As a conclusion, adequate coverage planning plays an important role in planning indoor networks for HSDPA, and some additional capacity can be gained by antenna configuration optimization.

Optimum performance of a network configuration corresponds to a configuration which minimises the number of sites required to provide a target service probability over the network coverage area. The purpose of this paper is to find the optimum network configuration for three alternative network layouts and to analyse and compare the performance of these layouts with the optimum configuration. Two of the selected layouts are widely used in cellular networks and the third has been selected as an alternative layout potentially providing performance improvement. The results indicate that all of the presented network layouts have comparable performance in nominal conditions used in the analysis and that usage of different network layouts could be considered more widely in practical networks

The aim of this paper is to assess the applicability of a repeater connected to a distributed antenna system for improving indoor capacity in UMTS radio network. A guarantee of sufficient coverage and capacity for in-building areas constitutes a considerable issue in topology planning, because in both links, indoor users produce high interference to the outdoor network due to significant indoor propagation losses. Presented configuration exploits effectively a repeater system that amplifies the signal from the outdoor network and delivers it for indoor locations through distributed antenna system. Implementation of the analyzed repeater system is straightforward as it does not require usage of separate carrier. Moreover, any separate scrambling codes do not have to be dedicated either. Conducted measurement campaigns reveal improvement of radio conditions due to repeater implementation that results in 35% gain of downlink capacity for indoor locations. Furthermore, in the analyzed scenario, the average value of SIR is improved by 3.41 dB that might lead to an increase of capacity in HSDPA as well. Simultaneously, the executed measurements illustrate the positive impact of the repeater configuration on the downlink capacity of the surrounding macrocellular network.

The target of this paper is to show the optimal base station antenna height and downtilt for a novel network layout, and to compare the performance of the novel network layout to a traditional layout. The optimum performance is derived by analyzing the maximum cell area which provides the minimum service probability over the analysis area. The results of the simulation campaign show that a novel network layout (modified hexagonal grid) provides equal or even slightly better performance than the nominal layout. Moreover, the obtained results define the optimal base station antenna height and downtilt in order to maximize base station coverage area with required service probability

Base station antenna diversity can be used to soothe the impairments caused by multipath propagation, interference and random angular orientation of the mobile station. Currently the widely implemented scheme is the space diversity with horizontal antenna separation. An attractive alternative to combat the non-idealities of the radio channel is to use polarisation diversity. The aim of this paper is to evaluate experimentally the impact of the mobile antenna orientation on the polarisation diversity performance in a DCS1800 network. Additionally, the performance of polarisation diversity schemes with horizontal/vertical (HV) and /spl plusmn/45/spl deg/ slanted antenna schemes are compared to the non-diversity case. The obtained results show that in coverage limited case almost equal diversity gain and system performance can be achieved independent on the mobile antenna orientation or on the implemented scheme.