Co-existence of terrestrial and non-terrestrial networks (NTN) is foreseen as an important component to fulfill the global coverage promised for sixth-generation (6G) of cellular networks. Due to ever-rising spectrum demand, using dedicated frequency bands for terrestrial network (TN) and NTN may not be feasible. As a result, certain S-band frequency bands allocated by radio regulations to NTN networks overlap with those already utilized by cellular TN, leading to significant performance degradation due to the potential co-channel interference. Early simulation-based studies on different co-existence scenarios failed to offer a comprehensive and insightful understanding of the overall performance of these networks. Besides, the complexity of a brute force performance evaluation increases exponentially with the number of nodes and their possible combinations in the network. In this paper, we utilize stochastic geometry to analytically derive the performance of TN-NTN integrated networks in terms of the probability of coverage and average achievable data rate for two co-existence scenarios. From the numerical results, it can be observed that, depending on the network parameters, TN and NTN users’ distributions, and traffic load, one co-existence case may outperform the other, resulting in the optimal performance of the integrated network. The analytical results presented herein pave the way for designing state-of-the-art methods for spectrum sharing between TN and NTN and optimizing the integrated network performance.

Measurement reporting is essential in every cellular network to guarantee the best radio resource management and performance to its users. The information in reports is mainly used to perform handovers and interference management between cells. In the case of cellular-connected UAVs, where the UAV impacts a high number of cells due to its flight height, measurement reporting becomes essential. However, applying the same reporting schemes used for terrestrial users, the UAV appears to generate a large number of reports, creating a substantial signalling overhead. To overcome this problem, we introduce in this paper a new measurement reporting scheme adapted for UAVs, which reduces the number of reports compared to LTE-supported aerial vehicles. Our scheme shows a 30% reduction in number of reports compared to LTE, without having a major impact on the network’s knowledge about the most relevant cells.

We focus in this paper on Cellular-connected Uncrewed Aerial Vehicles (UAVs) in a scenario of a camera-equipped UAV, streaming a live event. The UAV coexists with a large number of ground User Equipment (gUEs) belonging to people attending the same event, and using the network to transmit their data. Hence the cellular network must satisfy the high data rate demand of both the UAV and gUEs. For that, we explore interference mitigation solutions, and propose a novel algorithm for UAV cell-selection which minimizes the impact of the UAV to the concerned serving cell. The results demonstrate an uplink data-rate gain of 32% for gUEs in the crowded cell, compared to the standard algorithm, while achieving a target UAV throughput of 20 Mbps. This comes at a cost of increased UAV transmission power of 50% and a slight data rate degradation for gUEs in neighboring cells, up to 13%.

Broadband low Earth orbit (LEO) satellite constellations are a reality. The integration of satellite and terrestrial systems for mobile communications is taking-off with the development of non-terrestrial networks (NTN) and the ongoing deployment of private constellations. Due to the highly mobile nature of LEO satellites, one of the critical research areas is the design of the mobility mechanisms to ensure robust service continuity for the end-user. Recent studies in the domain of Earth-moving cells have shown that measurement-based handover (HO) triggering events cannot guarantee a low number of radio link failures without an increase in signalling and measurement reporting. In this work, we present a new HO triggering event that exploits the predictable movement of LEO satellites and uses the distance between the user’s location and the centre of the moving cells on the ground. The performance of the proposed solution is evaluated with system-level simulations and compared against the measurement-based baseline HO and Rel-16 Conditional HO (CHO). It is found that the location-based HO triggering event completely eliminates the HO failures as well as unnecessary HOs and ping-pongs. As a result, the location-based HO triggering event extends the mean time-of-stay from values below 2 s to 4.8 s where the optimal mean time-of-stay is 4.9 s.

The development of non-terrestrial networks (NTN) aims to satisfy the requirements of ubiquitous and seamless coverage for fifth-generation (5G) services. Low Earth orbit (LEO) satellites introduce challenging mobility requirements to the 5G New Radio (NR) radio resource management procedures. Current research shows that the baseline 5G NR UE-assisted network-controlled handover (HO) procedure, meant for terrestrial scenarios, fails to ensure continuous and satisfactory service in LEO-based NTN. The conditional handover (CHO), specified by 3GPP in Rel-16, was designed for terrestrial networks to enhance mobility robustness by making HO decisions earlier. In this work, we conduct system-level simulations to evaluate the 5G NR mobility performance of the CHO in a LEO-based NTN with Earth-moving cells scenario. The simulation results show that the CHO procedure reduces the radio link failures and handover failures to 0 but increases the unnecessary HO rate by more than 60% in comparison with the baseline HO, which leads to an increase of the signalling and measurement reporting. Finally, future research directions are identified to address the increase of the signalling overhead by exploiting the predictability of the satellite’s movement.

One of the key enablers for the use of cellular networks to provide connectivity to Unmanned Aerial Vehicles (UAVs) is reliability assurance. Estimating accurately the expected service availability and reliability that a UAV will experience along a planned route, helps to avoid critical situations. In this paper, we evaluate the use of a data-driven approach to estimate the expected serving signal level of a UAV planning to fly along a specific path. The estimation approach, presented in a previous study for the ground-level case, is based on the aggregation of measurements of UAVs that have previously been flying along the same route. Using this approach we achieve an estimation error as low as 2.7 dB. Based on the estimations we calculate the expected outage probability in terms of service availability and reliability and provide estimations of the expected critical areas along the route. Results show that 90% of the availability and 65% of the reliability critical areas in the route can be accurately estimated.

Low-Earth orbit (LEO)-based satellite communication systems are envisioned to be a next-generation key asset for telecom industry due to their potential to deliver global and seamless mobile broadband services. The high-speed mobility relative to Earth, that characterizes LEO orbits, will pose time-varying propagation conditions impacting the system performance in terms of mobility, availability and user throughput. Therefore, in LEO satellite systems, it is fundamental to understand accurately the signal variations between mobile satellites and users on the ground. This paper presents a radio propagation model able to describe realistically the time variations of the LEO-to-Ground path loss, including the line-of-sight changes and the impact of the surrounding built-up structures. We propose a low-complexity geometrical approach based on intelligent ray-tracing that considers the general dependencies on the elevation angle. The resulting model has been validated for a suburban scenario, exhibiting an overall root mean square error of 1.1 dB. Furthermore, the time-correlated geometry-based model is suitable for system-level radio mobility simulations with LEO-to-Ground satellite systems.

Low Earth orbit (LEO) satellite networks will play a major role in future broadband communications. To study LEO satellite mobility performance, and guarantee reliable service, accurate channel characterization is necessary. Current models, such as the ones reported by 3GPP and ITU, define channel parameters as a function of elevation angle, frequency and deployment scenario. However, key parameters including the line-of-sight (LOS) probability and the shadow fading do not describe any time component or correlation and, therefore, the movement of the satellite is not captured. This fact might result in unrealistic changes of the LOS/NLOS states hampering the radio mobility studies for 5G-based LEO satellite networks. In this paper, we present a Markov-based channel state model that takes into consideration the time correlations of the LOS variations along the satellite's orbit. The proposed model is based on ray-tracing measurements of suburban and dense urban scenarios and it can accurately reflect the behaviour of the channel state variations of those scenarios, essentially leading to a realistic number of state changes per satellite pass.

Estimating accurately the signal levels that a user equipment experiences along a movement route is a key step in the process of providing and guaranteeing the required service quality. Obtaining accurate location-specific estimations of the signal level is challenging due to its random variations. In this paper we investigate the use of aggregated measurements from multiple User Equipments (UE) to estimate the serving Reference Signal Received Power (RSRP) that the user will experience along a route. We use LTE measurements obtained in rural and urban areas from drive tests and analyze the dependence of data variability. Results show that the accuracy of data-driven estimation is impacted significantly by the variability in the underlying data due to UE orientation, UE characteristics and their immediate environment. With compensation for a subset of these effects the standard deviation of the estimation error can be lowered from an overall approximately 8 dB down to 4dB.

Cellular-connected unmanned aerial vehicles (UAVs) have recently attracted a surge of interest in both academia and industry. Understanding the air-to-ground (A2G) propagation channels is essential to enable reliable and/or high-throughput communications for UAVs and protect the ground user equipments (UEs). In this contribution, a recently conducted measurement campaign for the A2G channels is introduced. A uniform circular array (UCA) with 16 antenna elements was employed to collect the downlink signals of two different Long Term Evolution (LTE) networks, at the heights of 0-40m in three different, namely rural, urban and industrial scenarios. The channel impulse responses (CIRs) have been extracted from the received data, and the spatial, including angular, parameters of the multipath components in individual channels were estimated according to a high-resolution-parameter-estimation (HRPE) principle. Based on the HRPE results, clusters of multipath components were further identified. Finally, comprehensive spatial channel characteristics were investigated in the composite and cluster levels at different heights in the three scenarios.

In this work, we analyze the end-to-end latency measured in a client-server application that emulates the traffic requirements for the Unmanned Aerial Vehicle (UAV)'s Command and Control (C2) link. The connectivity is provided by two real LTE-A networks to a client attached to a flying UAV. Measurements are performed at 4 different heights: ground level, 15 m, 40 m and 100 m. In single operator scenarios, the reliability measured at the target latency, 50 ms, was between 99.6 % and 97.6 % in downlink, and 91.3% and 99.4% in uplink. These results are below the 99.9 % target reliability defined for UAVs and they show that several consecutive packets can be missed when the radio link connectivity degrades, leading to high (> 1 s) values for the 99.9%-ile of latency. To circumvent this, a dualoperator hybrid access scheme is proposed in this paper. The results show that the hybrid access strategy managed to reach the performance requirements in most cases. The solution shows potential to enable C2 over cellular networks, without requiring optimization or modifications in the network.

Although the use of cellular networks to serve drones has been investigated in several recent works, the path loss or shadowing variation is still relatively unexplored. The variation and its dynamic behaviour is of importance in characterizing the reliability of the drone communication link, but difficult to assess by experimental means on a large scale. The main goal of this paper is to study the feasibility of ray tracing models to accurately predict shadow fading variations at different heights, so that the shadow fading correlation distances for the UAV channel can be found in both vertical and horizontal directions, without the need of performing extensive field measurement campaigns. For that, predictions obtained through a ray tracing tool are compared to field measurements in an urban scenario. Our results show that with accurate 3D maps, the tool is useful for predicting the dynamics of the UAV propagation channel, and therefore can be used partly as a substitute for field measurements.

Mobility performance is at the heart of each cellular technology, including omni-present LTE networks. It becomes even more significant when such system is supposed to reliably support state-of-the-art devices, such as Unmanned Aerial Vehicles (UAVs), emerging at rapid pace in our surroundings. Contemporary network deployments, addressing mainly the needs of terrestrial users, were not optimized to serve UAVs moving below and above the typical cellular antenna heights. Thus, it is worth checking how they can handle these novel and distinctive services, also with respect to mobility robustness. This paper elaborates on the challenges ahead which must be tackled to make existing LTE networks sufficiently capable of accommodating Aerial Vehicles. We present simulation results in various environments, obtained for different user equipment's (UE's) heights and velocities. Furthermore, we describe and analyze the identified issues. Finally, we also suggest potential optimizations and future research goals.

This paper focus on the investigation of aerial communications for drones connected to cellular networks in urban areas. Most of the previous measurement based channel models for urban environments do not extend to users located at heights above rooftops. On the other hand, UAVs are expected to fly at the very low level (VLL) airspace, in heights much lower than those covered by previous air-to-ground models. By means of field measurements, this paper presents height-dependent closed form expressions for the urban channel model (path loss slope and shadowing) extending to heights up to 40 m and compares the observed results with 3GPP reference models and previous studies. Measurements were conducted by a radio scanner attached to a construction-lift to measure the radio signal from three different live LTE networks (800, 1800, and 2600 MHz). Results suggest radio path clearance increases with height. As a consequence, it leads to an increase in number of cells in the detectable range and in the set of neighbors within 3 dB of the serving cell in the receiver, indicating neighbor cells are closer to each other in the power domain.

Unmanned Aerial Vehicles (UAVs) are expected to be connected through cellular networks. As the radio characteristics are different for airborne UEs compared to terrestrial UEs, it is beneficial to identify whether a UE is airborne (on a UAV) or on the ground, such that interference and mobility management can be optimized for UAVs separately from terrestrial UEs. In this paper, we present a classification algorithm using existing LTE UE radio measurements to identify whether a UE is airborne or terrestrial. The method is verified with LTE measurements made in a rural area at different heights, including terrestrial measurements and it is shown that the method in 3 out of the 4 different measurement cases can detect a UE to be airborne with 99% likelihood, while the fourth case still can classify a UE correctly in 95% of the cases. The right classification can further be improved by taking multiple consecutive samples into account before making a classification decision.

This paper analyzes the radio channel between cellular network and Unmanned Aerial Vehichles (UAVs). The assessment is done by means of field measurements performed in a rural environment in Denmark. The tests were conducted in an operating LTE network (800 MHz), using a commercial cell phone placed inside the frame of a winged UAV. Trials were conducted with UAV flying at 5 different heights measured above ground level (20, 40, 60, 80 and 100m) and a pathloss regression line was obtained from the results. Thereafter, an analysis of downlink (DL) interference is performed for the reported measurements, which suggests that there is a height-related degradation on signal-to-interference levels. Three possible sources for this effect are also presented and discussed in this paper: expanded radio horizon at higher levels, line-of-sight (LOS) clearing and decreased obstruction of the first Fresnel zone. The importance of a better quantification of these factors are stressed as future work plans are described.

The use of Unmanned Aerial Vehicles (UAV) for civilian and commercial services has experienced a significant increase in the past couple of years. Emerging UAV enabled services, however, require extended beyond-visual-line-of-sight geographical range. One key regulatory requirement for these services is that the radio communication link must reliably cover a wide(er) area, when compared to the visual-line-of-sight range radio links currently used. Standardized cellular systems such as Long Term Evolution UMTS (LTE), are an obvious candidate to provide the radio communication link to UAVs. In this paper, we use empirical measurements in live rural LTE networks to assess the impact of uplink and downlink radio interference on the UAV radio connectivity performance. Further, we provide a baseline analysis on the potential of interference mitigation schemes, needed to provide a reliable radio connectivity to the UAVs.

In this paper we investigate the ability of Long- Term Evolution (LTE) network to provide coverage for Unmanned Aerial Vehicles (UAVs) in a rural area, in particular for the Command and Control (C2) downlink. The study takes into consideration the dependency of the large-scale path loss on the height of the UAV, which is derived from actual measurements, and a real-world cellular network layout and configuration. The results indicate that interference is the dominant factor limiting the cellular coverage for UAVs in the downlink: outage level increases from 4.2% at 1.5m height to 51.7% at 120m under full load condition. Lower network loads or larger inter-site distances reduces the interference and thus improves the coverage significantly: outage at 120m is reduced to only 1.9% under network load of 25% for example. Similar effects are expected to be achievable by static or dynamic interference coordination schemes. In addition, ideal Interference Cancellation (IC) scheme with ability to remove completely the dominant interferer shows less effective for UAVs than for users on the ground. On the other hand, macro network diversity has very good potential for drones, as not only it improves the coverage, but also the reliability of the C2 link.

In this paper we set out to analyze the indoor capacity under a realistic high-rise building scenario. The study takes into consideration the number of indoor cells deployed per floor, different inter-site distances (ISDs), transmit power settings and outdoor macro interference levels. The outcome shows large variation in performance gain just by optimizing indoor cell locations, highlighting the need for thorough indoor radio planning. Investing into more indoor cells helps to increase capacity, and also to cope better with outdoor interference, but the gain tends to be diminishing due to the increase of inter-cell interference (ICI). Increasing transmit power brings largest gain when the density of indoor cell is low, and the noise and/or outdoor interference is the dominant source of performance degradation. When analyzing performance gain of an ideal receiver-side Interference Cancellation (IC) algorithm, the study also shows that, if the Dominant Interferer Removal (DIR) rate is below 50%, doubling the number of indoor cells would bring better capacity gain than investing into such an IC receiver.

Indoor deployments for providing coverage and capacity inside buildings is an attractive option for cellular network operators as most of the traffic in today's cellular networks is generated indoors. This paper studies the benefit of indoor traffic offloading on the overall network capacity using a new method that allows assessing the network performance gains considering different levels of traffic offloading without the need to decide beforehand which buildings to deploy the indoor solutions in or the exact type of indoor solution used in each building. Using this method, we evaluate the impact of different amounts of indoor traffic offload and the performance of three different indoor deployment strategies on a study case network selected as a typical real world ultra dense urban area. The results show that choosing the most cost-effective buildings (lowest cost per traffic offload) first in the indoor deployment plan leads to highest network capacity gains for the same level of investment.

The objective of this paper is to propose traffic steering solutions that aim at optimizing the end- user throughput. Two different implementations of an active mode throughput-based traffic steering algorithm for Heterogeneous Networks (HetNet) are introduced. One that always forces handover of the active users towards the cell offering the highest throughput, and a second scheme that aims at maximizing the systems sum throughput. Results show that the first option brings the best performance at the cost of more than three handovers per user per second for high-load cases. The second option offers slightly lower traffic steering gains at a considerably lower cost in terms of number of handovers. The gain in terms of increased average session throughput for the second option equals 32% at low-load, 18% at medium-load, and 7% at high-load conditions. The gain in the fifth percentile user session throughput is generally higher, reaching values of 36% and 18% for the medium- and high-load conditions.

Complementing macro-only cellular networks with low-powered base stations is a promising deployment solution to cope with exploding data traffic in the coming years. In Long Term Evolution (LTE)-Advanced, interference mitigation technologies, like the linear interference rejection combining (IRC) receiver and Enhanced Inter-Cell Interference Coordination (eICIC), are introduced to address the co-channel interference between macro and small cells in downlink. These advanced techniques will boost the performance of small cells, and impact the network deployment upgrade. In this paper, LTE-A small cell deployments are evaluated through a network upgrade case study. A network upgrade with small cell deployments is simulated in a realistic metropolitan scenario to satisfy the traffic growth forecast over a period of ten years. A dynamic system level simulator is used to model the network behavior of IRC receiver and eICIC. The deployment time, scale and cost of the small cells improved by interference mitigation solutions are presented. The simulation results show that small cell deployments are the fundamental way to increase the system capacity as well as that eICIC is a promised solution to improve the system capacity. An increase of 56% in system capacity, which corresponds to a ~19 month network upgrade delay and 34% cost savings , can be achieved by eICIC in the case where small cells deployments become very dense.

In this paper, evaluation of HSPA radio technology is provided with the reference to IMT-Advanced requirements. Recent technological advancements are included to verify if HSPA is capable of meeting these requirements. Extensive system-level simulation campaigns are carried out, which shadow IMT-A performance evaluation guidelines and suggested test environments specifications. Respective results are analyzed in the context of spectral efficiency, VoIP capacity and high speed mobility of IMT-A requirements. The presented results indicate that although a single strongly interference-limited environment is unlikely to pass stringent IMT-A spectral efficiency criteria, overall all the IMT-A test requirements are passed.

In this paper traffic steering between a High-Speed Downlink Packet Access (HSDPA) network and a 3GPP Long Term Evolution (LTE) network with different carrier frequencies is investigated. First, two traffic steering algorithms, relying on static network information, are assessed from a traffic theoretical point of view and numerically. Furthermore, numerical analysis of two traffic steering algorithms, relying on dynamic information such as user SINR and cell load, is also performed. It is shown that the dynamic traffic steering algorithms outperform the static methods in terms of end user performance. Finally, it is investigated how the LTE terminal penetration affects the performance of the proposed traffic steering algorithms. For low LTE terminal penetration all LTE capable terminals should be pushed to the LTE network, and for high LTE terminal penetration a more dynamic traffic steering scheme should be used.

Small cells are popular deployment options for coverage holes and capacity hotspot areas. Due to the poor outdoor-to-indoor propagation property of in-building environment, a dedicated wireless system installed inside the building is often preferred for providing indoor users high-data-rate services. Distributed antenna systems and Femto cells are cost-efficient techniques for this application. In this paper, their performance is evaluated in an LTE downlink context along with a proposed joint scheduling system, which maximizes the supported number of users under a QoS constraint. The selection of the enterprise building model includes a general office building model described in the WINNER II project and a site-specific office building with large scale path-loss values retrieved from measurements. Results show superior performance of the Femto system compared to DAS in providing high-data-rate services in most cases with a quality-guaranteed scheduler, while the centralized joint scheduling system gives the best performance. The centralized scheme can also help improve the system robustness in obtaining high performance even in the situation where access points are placed non-optimally.

In the Long Term Evolution system Discontinuous Transmission and Reception (DRX/DTX) has been introduced to extend the terminal battery lifetime. In this paper, we study the energy-saving provided by this mechanism and the impact on the QoS performance of Voice over IP (VoIP) traffic under dynamic and semi persistent packet scheduling strategies. Simulations and analytical results show that the DRX/DTX scheme can reduce the terminal power consumption without compromising the required VoIP QoS in terms of maximum air-interface delay. However, it does not provide any further power savings if the terminal is asleep for a period longer than 20 ms. It is shown that the power savings are larger for semi persistent scheduling than for dynamic packet scheduling at the cost of a lower spectral efficiency.

This paper studies the different ways of extending wireless coverage for high data rates and improving the data capacity in a building. The solutions considered include deployments of single or multiple small base stations, i.e. Picocell or Femtocell, and distributed antenna system, operated on the same frequency as the macro cellular network. We look at the radio performance of each solution in a LTE downlink context with in-building path loss values retrieved from real-life measurements. The performance is compared by means of maximum supportable user numbers and average system throughput. Potential gains by hard frequency reuse in the building and QoS based packet scheduling are examined. Simulation results show the robustness of the proposed distributed antenna system and the conditions for multi-Femtocell deployment.

This paper deals with packet scheduling for Voiceover-IP (VoIP) traffic in the Long Term Evolution (LTE) EUTRAN Downlink. The more specific target is to optimize the performance of dynamic scheduling for traffic mixes of VoIP and best effort users. To this end, we introduce the Required Activity Detection (RAD) packet scheduling algorithm with Delay Sensitivity (RAD-DS).With an appropriate delay sensitivity function, it is shown that a MACRO 1 cell with 5MHz transmission bandwidth can support up to 346 VoIP users. Furthermore, a novel delay sensitivity based soft prioritizing strategy is proposed for handling traffic mixes. It is shown that when 200 VoIP users are present in a cell along with best effort users, the proposed strategy can provide a cell throughput of up to 82% of the cell throughput with only best effort users.

For the future LTE-Advanced network, one of the requirements in the uplink (UL) direction is to enhance the celledge user performances. Coordinated multi-point reception in the UL is one of the techniques being investigated to further improve the performance of LTE networks. With the help of the information coordination through the links between the sites and advanced receivers the UL performance can be improved. The simulation results show that, with the ideal interference cancellation, inter-Site maximum ratio combining, and optimized closed-loop and open-loop fractional power control, there are about 27% gains for the 5% outage user throughput and 12% gains for the average user throughput. As shown in this paper, these gains from UL macro-scopic multi-cell combining between sites are achieved for optimized power control, ideal interference cancellation receivers, and X2 with no delay and high bandwidth.

In the UTRAN long term evolution (LTE), the downlink data channel is shared among the active users through the orthogonal frequency division multiple access (OFDMA) technique, and high gains can be achieved by using dynamic packet scheduling. Control channels introduce an additional overhead, but also play a key role in exploiting such gains. This paper focuses on the physical downlink control channel (PDCCH) and introduces the main PDCCH related features which need to be analyzed in order to minimize its impact on the system performance.

This paper focuses on the Physical Downlink Control Channel (PDCCH) and describes the impact of its realistic constraints. Specifically, the impact on the performance of the UTRAN LTE FDD downlink and on the QoS provisioning is studied. It is described, when adopting a QoS-aware packet scheduling policy, how scheduling limitations due to control channel may affect the scheduler behavior. It is shown that the system level performance degradation could be kept negligible utilizing the dynamic link-adaptation mechanisms available on the control channel and adopting careful control channel-related design solutions. Therefore, assuming a proper dimensioning in terms of OFDM symbols reserved for control, the PDCCH could simply be modeled for LTE FDD system level simulation purposes by limiting the number of PDCCH allocations. Such a number primarily depends on the system bandwidth.

The 3GPP UTRAN Long Term Evolution (LTE) system utilizes packet based architecture with distributed mobility management, where the E-UTRANNode-B (eNB) takes the responsibility of making the hard handover/handoff (HO) decisions based on the user equipment (UE) measurements. To cope with the corner effect due to the loss of the line of sight (LOS), a fast HO decision algorithm is required which can guarantee the LTE seamless HO requirement and keep the quality of service (QoS) criteria. In this paper, a HO decision algorithm, the integrator algorithm, has been evaluated in the Manhattan scenario, and is compared with the traditional power budget (PBGT) handover. The study focuses on the LTE intra-frequency HO scenario and uses the reference symbol received power (RSRP) measurement as input. The results show that the integrator algorithm has the same performance as the PBGT algorithm based on the number of HOs per UE and signal to interference plus noise ratio (SINR) evaluations for different UE speeds.

To minimize the terminal's transmission power in bursty uplink traffic conditions, the evolved high-speed uplink packet access (HSUPA) concept in 3GPP WCDMA includes a feature known as dedicated physical control channel (DPCCH) gating. We present here a detailed link level study of gating from a link efficiency (LE) perspective; LE being expressed in bits per second per Watt. While the overall gain mechanisms of gating are well known, we show how special challenges related to discontinuous enhanced dedicated channel (E-DCH) transmission can be addressed for high link and system performance. We consider the E-DCH performance degradation caused by gating on other radio procedures relying on the DPCCH, such as inner and outer loop power control. Our studies show that gating is beneficial for both for 2 and 10 ms transmission time intervals. The gains in terms of LE with a vehicular A 30 kmph channel are in the range of 4-5 dB for a bit rate of 32 kbps and an E-DCH activity factor of 0.1. For bit rates higher than 1 Mbps and an activity factor of 0.25, the gains are close to zero or even negative.

The E-HICH is a downlink control channel associated to the HARQ procedure in HSUPA. It allows the MAC-e entity in the NodeB to signal the correct or incorrect reception of a given MAC-e PDU by transmitting ACKs or NACKs. Errors on this channel can cause misinterpretations and impact the overall system performance. This paper looks at the performance impact caused by two types of errors: ACK misinterpreted as NACK and vice versa. Detailed user and system performance results versus the error levels on the E-HICH are provided for both cases. A2N errors cause a direct degradation of the user throughput that increases with the probability. N2A errors have a more intricate impact that leads to opposite effects. On the one hand, it causes the level of RLC retransmissions to increase. On the other hand, the missing PDUs change the HARQ operating point which will then decrease the RLC retransmission level. The overall consequence is a lowered cell and user throughput for lowly loaded networks, whereas it is almost imperceptible in fully loaded networks.

The relative contribution of the transport network towards the per-user capacity in mobile telecommunication systems is becoming very important due to the ever increasing air-interface data rates. Thus, resource management procedures such as admission, load and handover control can make use of information regarding the available bandwidth in the transport network, as it could end up being the bottleneck rather than the air interface. This paper provides a comparative study of three well known available bandwidth estimation techniques, i.e. TOPP, SLoPS and pathChirp, taking into account the statistical conditions of the available bandwidth and assessing the variability of their estimations. Simulation-based studies on a mobile transport network show that pathChirp outperforms TOPP and SLoPS, both in terms of accuracy and efficiency

This paper presents HSDPA performance evaluation in an urban micro cell environment with outdoor base station antenna heights below roof-top level (10 m) and both outdoor and indoor pedestrian mobiles (3 km/h). A path loss model which accounts for the 3D geometry of the radio environment is used, thus allowing the simulation of indoor user locations at different building floor levels. The single user throughput evaluation is carried out using realistic HSDPA link-level simulations combined with the newly obtained statistics of the geometry factor in the considered micro cell environment. The results with 80% HSDPA power and 15 HS-PDSCH multi-codes showed median single-user throughput in the range of 4.8 Mbps/cell. It was also found that ground floor areas can be served with up to 5% better median throughputs compared to the outdoor and high (top) floor areas

High speed uplink packet access (HSUPA) improves the cell throughput by faster scheduling, L1 HARQ and enhanced bit rates. This paper introduces a dynamic system simulator for studying HSUPA system performance. This simulator is used to analyze the effect on the cell throughput of increasing the BLER target and the target number of transmissions. The L3 cell throughput increases when the target number of transmissions increases, while the control overhead in terms of transmission power is estimated to be approximately 25%

The present paper highlights the performance of the transport control protocol over WCDMA networks. The TCP flow control adjusts the transmission rate to the network and receiver's capacity. Due to this protocol self-adaptation to the transmission conditions of the links involved in the TCP connection, the protocol performance can not be disconnected from the underlying network. In WCDMA networks, the RRM assigns the radio resources to the UE in the cell, which directly impacts the TCP throughput performance. The results show that the allocation of high bit rate dedicated channels to small file downloads (such as Web pages) produce poor channelization code efficiency compared to allocating low bit rate channels. Under certain conditions, for large file downloads (such as ftp) the code efficiency and throughput performance improve significantly due to the protocol nature to fully utilize the bottleneck capacity. This protocol performance suggests a radio resource allocation strategy for DCH channels, which increases the bit rate stepwise as the file transmission evolves starting from a low bit rate.

Baseband frequency hopping in the combination with downlink power control and discontinuous transmission has been investigated as a quality improving feature in a live GSM network. Using the dropped call rate and the frame erasure rate to measure the network quality, the use of frequency hopping proves a powerful network quality enhancement feature. By optimising the frequency plan and the handover algorithm a reduction in dropped calls is achieved. Along with frequency hopping, downlink discontinuous transmission has been investigated. In this situation an increase in bad quality, partly due to the statistical inaccuracy with discontinuous transmission in GSM and maybe due to poor performance of the mobile stations, was encountered. The current status is therefore to reject the use of downlink discontinuous transmission until more information about the performance of the mobile stations is found. The combination of baseband frequency hopping and downlink power control has also been investigated. Even with a maximum dynamic range of 6 dB a large average base station transmitting power reduction is achieved. However no quality improvements in terms of dropped calls could be found.

IUO (intelligent underlay-overlay) in a combination with random frequency hopping in GSM is analysed. Several improvements to the original IUO concept analysed in Nielsen et al. (1997) are introduced. With the improved IUO concept it is possible to load a network configuration consisting of 4 regular frequency channels and 3 super layer channels almost to the hard blocking limit. A capacity gain of more than 40 percent compared to a one layer frequency hopping 3/9 reuse network has been found.

This paper analyze the performance of two branch antenna diversity in GSM related systems. Several combining techniques for both up- and downlink are analyzed. Frequency diversity obtained from slow frequency hopping in GSM is also considered. Finally antenna diversity results for a non-ideal antenna configuration, i.e., introducing antenna branch cross-correlation or cross polarization discrimination (XPD) are presented.

To evaluate the performance of a mobile radio system, both network and link quality aspects have to be evaluated. A network simulator is often used to find the influence of different system parameters, such as DTX, frequency hopping and power control. To complete the evaluation, a link simulator has to be integrated in the network simulator, so that each radio link can be simulated. An obvious method to integrate the radio link quality aspects with the network simulator is to use the output of the network part of the simulator as input for an integrated link simulator. This will however lead to time consuming simulations, In this paper a simpler method is presented, which leads to a shorter simulation time. The output of the network part of the simulator, expressed in signal to interference (C/I) values, is used as input for look-up tables, which lead to a BER and a frame erasure rate (FER) for each radio link. These look-up tables are depending on the hopping pattern and channel profile and they are also receiver dependent. The results of the mapping method are good, except for a few situations, where the prediction of the BER goes wrong. This happens when sequential hopping with a few frequencies is used and the speed of the mobile user is low. In general the presented predictions are within 1 dB (FER) and within 0.2 dB (BER).

The need for more capacity in GSM networks is increasing. Using random frequency hopping and fractional loading is a potential way to obtain more capacity. In this paper the optimal reuse scheme for a GSM system with random frequency hopping is presented along with some methods to increase the capacity and to improve the link quality, like using DTX and fractional loading. The 1/3 reuse scheme appears to be best if the capacity is determined by looking at the distribution of signal to interference (CIR) values, while the 3/9 reuse scheme seems best if the focus is at the percentage of dropped calls (with the used dropped call, power control and handover algorithm). The 1/3 reuse scheme has the advantage over the 3/9 reuse scheme that it is able to profit from fractional loading, which gives better quality to the individual user.

Optimum diversity combining in a wireless communications system using TDMA/TDD is considered. By the use of optimum diversity combining a receiving antenna array is able to suppress interference and thus the capacity of the system is increased. The results in this paper are obtained by simulations. In the simulations a DECT-like system is used as the TDMA/TDD system. The results show that in the uplink direction M-1 interferers can be suppressed by an M element array. However the downlink transmit diversity performance is much worse, due to the changes in the radio channel during the dwell time between the uplink and downlink burst. That is the reason why it is concluded that optimum diversity combining is only useful for a TDD system with a short dwell time.