This paper investigates a dynamic packet scheduling algorithm designed to enhance the eXtended Reality (XR) capacity of fifth-generation (5G)-Advanced networks with multiple cells, users, and services. The scheduler exploits the newly defined protocol data unit (PDU)-set information for XR traffic flows to enhance its quality-of-service awareness. To evaluate the performance of the proposed solution, advanced dynamic system-level simulations are conducted. The findings reveal that the proposed scheduler offers a notable improvement in increasing XR capacity up to 45%, while keeping the same enhanced mobile broadband (eMBB) cell throughput as compared to the well-known baseline schedulers.

This paper presents a dynamic inter-cell interference coordination (ICIC) technique that enhances extended reality (XR) capacity, while minimizing the impact on enhanced mobile broadband (eMBB) traffic in a multi-cell multi-user network. The network identifies victim XR users based on their experienced performance and dynamically coordinates with aggressor cells for muting in specific transmission time intervals to alleviate interference for the victim users. Extensive dynamic system-level simulations demonstrate the effectiveness of the proposed ICIC scheme, achieving a 22-32% gain in XR capacity while incurring a degradation of 12-22% in average eMBB cell throughput.

In this paper, we address the joint performance of eXtended reality (XR) and best-effort enhanced mobile broadband (eMBB) traffic for a 5G-Advanced system. Although XR users require stringent throughput and latency performance, operators do not lose significant additional network capacity when adding XR users to an eMBB-dominated network. For instance, adding an XR service at 45 Mbps with a 10 ms packet delay budget yields close to a 45 Mbps drop in eMBB capacity. In an XR-only network layer, we show how the capacity in a number of supported XR users depends significantly on the rate but also the latency budget. We also show how the XR service capacity is significantly reduced in the mixed service setting as the system goes into full load and other-cell interference becomes significant. The presented results can be used by cellular service providers to assess their networks’ performance of XR traffic based on their current eMBB performance or as input to dimensioning to be able to serve certain XR traffic loads.

Due to mobility and interference, using enterprise Wi-Fi for communication in industrial networks can result in control loop latencies exceeding 100 ms for at least 0.1% of the time, even in those cases where Wi-Fi handover-specific parameters have been optimized, making the technology unfit for Industrial IoT (IIoT) with strict communication reliability requirements. To improve its performance, this paper presents a novel approach towards the design and implementation of a radio-aware multi-connectivity concept using a layer-4 scheduling mechanism. Two packet scheduling mechanisms are presented: packet duplication and best path scheduling. A mobility coordinator scheme is used to improve the performance of the packet schedulers by preventing simultaneous handovers and ensures the STAs connect to different APs. By using this multi-connectivity solution, a significant performance improvement was observed, cutting down the latencies of the system to 30-80 ms at the 99.9%-ile of reliability (depending on the operational conditions). Furthermore, by applying the proposed schemes, Wi-Fi handovers delays can be fully mitigated allowing for true seamless roaming in mobile conditions.

5G New Radio (NR) technology is expected to enable the wireless transition of manufacturing processes in modern factories. In order to proper dimension the 5G system, accurate models of the data and control traffic in industrial use cases are needed. In this paper, we analyze the industrial traffic empirically measured in different Danish factories and compare its characteristics to the modeling assumptions used in the 3GPP for 5G NR performance analyses. In particular, three relevant use cases are studied: a unit test cell for actuator calibration, a visual inspection cell, and the control of an autonomous mobile robot (AMR). Our results indicate that some of the relevant 3GPP assumptions for industrial traffic such as exponential packet-interarrival time (PIAT) for aperiodic traffic and fixed packet sizes are only partially corroborated by experimental evidence. Moreover, industrial traffic can exhibit a large burstiness that may lead to conservative admission control and radio resource allocation.

This paper presents the implementation framework and performance evaluation of a wireless Manufacturing Execution System (MES) for Industry 4.0. The proposed solution is based on self- configuring multi-access gateways that enable seamless transport of delay-tolerant industrial Ethernet control data traffic over LTE or Wi-Fi (or both, using hybrid-access techniques). The wireless MES solution has been deployed at the Smart Production Lab facilities at Aalborg University, allowing the removal of Ethernet cables between modules in a production line setup, and thus enabling a faster re-configuration of the production facilities. The performance of the wireless MES solution is benchmarked against the reference Ethernet case in terms of latency and packet loss. The trials revealed that, despite the increase in latency and packet loss as compared to the reference operation over Ethernet, both LTE and Wi-Fi under different conditions were able to reliably support the production control operations at MES level without discernable difference on the overall functionality of the system.

In this paper, a new multi-connectivity protocol is introduced for mission critical applications that use wireless 5G multi-UE devices. It extends the MP-QUIC transport protocol by adding selective data duplication with strict prioritization to support a mix of critical and non-critical applications on a single end-to-end connection; e.g. suitable for self-driving cars getting mission critical drive control commands from the network (priority) while receiving map- updates (background). The Selective Redundant MP- QUIC solution simultaneously provides bandwidth aggregation and higher speeds for background data while ensuring maximum reliability and availability for the priority data by duplicating it on the available paths. The proposed algorithm is first evaluated using an emulated fixed-delay channel as well as a well-known Internet connection model. Next, a highway drive test is conducted using two LTE modems, resembling a typical autonomous car scenario. The tests show that the algorithm can protect the critical data flow also in presence of a background load of 2 Mb/s and across a wide range of channel conditions. Using our proposed MP-QUIC solution over two LTE connections, the 99.9%-tile of critical traffic latency shows a 5 times improvement versus using a single-path connection and 3 times versus using state of the art MP-QUIC protocols.

In this paper we study the potential of commercial Long Term Evolution (LTE) networks for supporting reliable low-latency applications. To this end, we use one-way end-to-end latency measurements of a commercial LTE network deployed in Vodafone R&D's Innovation Lab where we control the over-the-air traffic and air interface configuration. The experimental results show that the achievable latency and reliability is mainly limited by two features of the LTE radio system: the configured Discontinuous Reception (DRX) pattern and the Scheduling Request (SR) periodicity of the UE. The one-way latencies vary between 40 and 95 ms at the 99.9% percentile, depending on the inter-arrival time of the generated traffic. By disabling or applying less-restrictive DRX and SR patterns and using an aggressive uplink allocation technique, we show how the one-way latency performance improves significantly, e.g. as low as 7 ms with 99.9% probability regardless of the traffic characteristics. For cases where configuring the radio interface is not feasible, we show different options available at the application layer for improving the latency performance of the application. For instance, the application may frequently transmit small packets to reduce the probability of the UE going to DRX mode, or coordinate the message generation interval with the SR opportunities and DRX patterns of the underlying radio system.

Autonomous vehicle applications require sub-100 ms message latency with a high success probability. While this will be supported by upcoming fifth generation networks, hybrid access technology using multiple LTE connections, may pave the way for the autonomous vehicle applications today. In current LTE networks, handovers often lead to long data interruption. Therefore, we study the handovers and the related data interruption, and how performance can be improved through hybrid access, using redundant transmissions over multiple connections. The study is based on drive tests, where four QualiPoc measurement smartphones are connected to different LTE networks simultaneously, performing synchronized ping latency measurements, and recording handover events. The results show that a handover event during a ping measurement, prolongs the average latency from 60-80 ms to more than 200 ms. However, the handovers do not occur simultaneously in the measured LTE networks. Therefore, hybrid access with two connections is shown to reduce the handover outage by a factor 60. Furthermore, the 99.9 %-tile latency is reduced 66 %, by using two simultaneous connections, as compared to the best single network measurement.

This paper presents enhancements for lowering the handover interruption time in future wireless networks. We propose a selective data forwarding for the handover preparation phase, and the integration of the make-before-break procedure with the synchronous random access-less handover. To evaluate our proposals, we analyze the handover timing for typical and variable values of the user equipment and e-NodeB processing times, and X2 interface latencies. Our results show that the processing delays, reconfiguration times, and the X2 latency should be simultaneously reduced to minimize the data interruption time. Selective data forwarding during the handover preparation reduces the data interruption time by 18 % compared to the basic random access less handover with typical network delays. Make-before-break is the most suitable handover type for future low-latency applications, as it achieves zero data interruption independent of the latency of handover steps.

Radio networks are at the brink of a transformation in order to meet new requirements for high data and device densities expected for the Internet-of-Things (IoT) era. Cloud technology is positioned to be a key element in building effective 5G radio networks, so-called Cloud RANs. In this paper, we focus on Cloud RAN architectural benefits in relation to synchronous handovers without random access; an important enabler for ultra-low latency and ultra-high reliability services for high mobility IoT applications. We analyze the performance of Cloud RAN architectures and introduce a new concept for reducing the handover preparation time. Compared to today's distributed RAN architectures, we show a handover preparation time reduction of up to 60% for a wide range of interface and processing latency assumptions.

Cloud Radio Access Networks (Cloud RAN) is an emerging architectural paradigm that attempts to exploit operational efficiencies through centralization of baseband functions, pooling efficiencies for RAN baseband processing, and air-interface performance gains by fast-time-scale multi-cell coordination. In this paper, we aim to derive insights underlying key technologies and tradeoffs that drive Cloud RAN. We highlight principles that explain the impact of Cloud RAN architectures and functional splits on multi-cell coordination gains. We show that the ability to extract pooling gains can differ significantly between RAN functions, depending on whether they are per-user or per-cell functions. We propose a method for elastic scaling of RAN functions that takes into account both real-time and non-real-time needs. We conclude with a proposal for a methodology for operators to evaluate the overall tradeoffs they will face in deciding whether to adopt Cloud RAN.

We compare the algorithms for centralized and decentralized multi-cell joint optimization of coordinated scheduling with muting. For conventional non-overlapping clusters of cooperating cells, we show that for the same latency of communication, an appropriate decentralized algorithm can equivalently achieve the same jointly optimal solution achieved by a centralized approach. In this decentralized algorithm, cells do not exchange CSIs of all users with other cells, but instead exchange per-cell benefit metrics. In non-overlapping clusters, border cells in a cluster do not coordinate with strong interferers outside the cluster. We introduce a new cluster design called Liquid Cluster which allows a cell to flexibly cooperate with all its relevant interferers. The decentralized algorithm easily extends to Liquid Clusters, performing better than conventional non-overlapping 9-cell clusters.

Enhanced Intercell Interference Coordination (eICIC) techniques boost the performance of co-channel deployments of macro and small cells. However, features like the Almost Blank Subframes (ABS) are intended to be semistatically configured, due to the limited amount of information and the intrinsic delay over the X2 inter-cell interface. In this paper we investigate dynamic solutions for the allocation of the muted resources with small cells in the form of Remote Radio Heads (RRH), connected to the macro cell through a low latency interface. A simple eICIC framework for intercell Radio Resource Management in macro-RRH cases is developed. Based on minimal information collection, we propose an algorithm that adjusts the ABS ratio on a fast basis, aiming at balancing the instantaneous load betweeen the macro and the RRH layer. Performance results with bursty traffic and low and high load conditions show that the dynamic algorithm provides gains of 40-50% both in 5%-ile and 50%-ile user throughput compared to the semi-static case.

As small cell solutions for efficient in-building wireless deployment, the distributed antenna system (DAS) and Femtocells constitute two major options. In this work, we study the Total Cost of Ownership (TCO) in combination with system performance in order to reach technology-economical conclusions regarding of these deployment options. Our aim is to identify the most cost economical solution for indoor wireless deployment which meets the indoor capacity need and provides ubiquitous indoor coverage. In the analysis we focus on LTE enhancement in the enterprise buildings. We discuss the unique cost features of DAS and Femto systems and highlight the importance of backhaul visibility in the cost analysis. For enterprise building solutions, we show the cost advantage of low-cost Femtocells over DAS in all scenarios regardless of coverage building size. We also suggest when DAS becomes more economical for large buildings with low data traffic need.

The Macro offload of closed mode 3G Femtocells is studied; i.e. how much of downlink macrocellular traffic can be moved to a Femtocell layer. Taking the 3GPP dense urban reference model as our starting point we show that the combination of adaptive Femtocell power calibration together with a Macro-user frequency allocation method that considers the SINR difference between the mixed and a Macro-only carrier, improves offload. Additionally, the total number of carriers available to the operator is important for the offload potential. It is confirmed that a macro-only carrier is a desirable deployment strategy. At a 25% HNB penetration rate in apartments, 7% of the network traffic can be offloaded in the two-carrier case. This improves to 15% when three carriers are available. With Femto-aware macro-user carrier allocation, the offload performance improves further to 20% with 2 carriers.

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.

In this paper we consider the co-existence of 3G macro and femto base stations (MNB and HNB) on the same frequency carrier. Both restricted closed subscriber group (CSG) and non-CSG HNBs are investigated into. We consider both residential and office/apartment deployments using the agreed 3GPP simulation assumptions. We demonstrate the macro offload capability of HNBs and show that end-user experience in many cases is mainly improved due to being the only one served by the cell. We find that 25% of users would experience worse channel quality towards their HNB than towards the MNB in the same location, though the overall network capacity is improved. Results indicate that an operator should take some care as to where HNBs are deployed and have at least a single CSG-HNB free carrier to ensure wide area coverage inside buildings (even if aggressive power control schemes are used).

This paper addresses the performance of spatial division multiplexing (SDM) multiple-input multiple-output (MIMO) techniques together with frequency domain packet scheduling (FDPS) in both theory and practice. We start with a theoretical analysis under some ideal assumptions to derive the performance bounds of SDM-FDPS. To facilitate the analysis, a unified SINR concept is utilized to make a fair comparison of MIMO schemes with different number of spatial streams. The effect of packet scheduling is included in the post-scheduling SINR distribution using an analytical model. Based on that, the performance bounds are obtained with a more realistic SINR to throughput mapping metric. The system-level performance of SDM-FDPS has been evaluated under practical constraints using detailed simulations based on the UTRAN long term evolution (LTE) downlink cellular system framework. The purpose is to investigate the impact of realistic factors on performance. Results confirm that the combination of SDM and FDPS can increase the spectral efficiency significantly, particularly in a micro-cell scenario, and up to 30%-60% gain is observed over 1times2 with FDPS depending on the traffic models considered. Finally, the more practical simulation results are compared against the theoretical performance bounds. A performance loss is seen in the simulations due to realistic coding/modulation, impact of frequency selectivity, signalling constraints, imperfect channel quality indicator (CQI), etc.

Wireless Communications Systems are at the centre of a new and passionate era for telecommunications characterised, in industrial terms, by the convergence of systems and technologies, a transition towards all-IP networks, and the development of technologies with a user-centric focus. On the other hand, in terms of Research and Development, researchers are already considering other, more futuristic, aspects beyond those just mentioned, and these days hot topics include things like the Internet of the Future, and all the Post-IP perspectives that come with it. In both grounds, that is the more industrial related one and the one nearer an academic perspective, there is still a long way to go, before many of the ideas being discussed today can see the light of day as a commercial product. In this context, the International Symposium on Wireless Communication Systems (ISWCS) has positioned itself as a dynamic forum for researchers and technologists to present and discuss original ideas and contributions in all fields related to mobile and wireless communication systems. ISWSC'06, the 3rd edition, held in Valencia, Spain, on September 2006, brought together leading and enthusiastic researchers and technologists, willing to identify and discuss the future technical challenges and business opportunities arising in the path towards the realisation of ambient wireless communication networks. Besides this, it was a good forum for Ph.D. students to present their work, and exchange their ideas. The idea of setting up a special issue of a journal with the very best papers of the conference was brought up by the excellent quality of some papers presented at the conference. The objective of a special issue of this kind is always to put together, beyond the conference proceedings, the best papers in an enhanced and revised version, enabling the journal to publish good papers with timely updated information in a very short time. This special issue of Wireless Communications and Mobile Computing contains the very best papers presented at ISWCS'06. An invitation was sent to a restricted number of papers, and an additional review procedure was held, beyond the conference one. At the end, this set of six papers was accepted. The papers in this issue address some of the hot topics being investigated these days, ranging from localisation and frequency sharing to multi carrier-code division multiple access (MC-CDMA) and multiple input multiple output (MIMO). This shows that the physical layer still attracts a lot of attention, and that it still has a lot of topics to be explored. The first two papers address MIMO channels, in modelling or measurement perspectives. Matthias Pätzold and Bjørn Olav Hogstad present a model for a wideband MIMO channel based on the geometric elliptical scattering one, which can be used as a starting point for the derivation of a frequency-selective space–time channel simulator, being also useful for studying MIMO channel capacity under various propagation conditions. Michail Matthaiou et al. bring a paper on dual frequency MIMO measurements around the ISM 2.4 GHz band, in indoor environments, with initial results being promising enough, as the joint spectra seem to be remarkably similar, implying that the underlying propagation mechanisms at the considered bands are also similar. Farrukh Rashid and Athanassios Manikas present one of the papers dealing with MC-CDMA, namely on arrayed reception in space-time diffused multipath vector channels; results show that the use of a diffused channel modelling in arrayed receivers yields better bit error rate (BER) and signal to noise plus interference ratio (SNIR) performance than receivers that ignore the presence of spatial and/or temporal diffusion. The other paper on MC-CDMA, from Nguyen Tran Khoa et al., addresses frequency sharing in hotspot communications for cellular networks; it proposes an overlap in the uplink of an OFDM hotspot system to an MC-CDMA cellular one, in the same frequency band, beam-forming being applied to eliminate inter-system interference. The paper for Barbara Mavì Masini et al. also deals with the coexistence of different systems, in particular on the benefits of diversity schemes for Bluetooth coverage extension in the presence of IEEE 802.11g interference, analysing packet error and coverage probabilities, among other parameters. Finally, Joseph Shmuel Picard and Anthony Joseph Weiss present a paper addressing localisation of networks using various ranging bias models, presenting a set of iterative algorithms that cope successfully with the various bias models and provide Maximum Likelihood position estimates.

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.

In this paper we analyze the downlink OFDMA system-level performances of a 2times2 dual-stream MIMO multiuser transmission scheme under the assumptions of partial and noisy channel quality indicator (CQI) feedback available from the terminals. The effects on the CQI feedback of the terminal measurement and estimation errors, quantization errors, uplink reporting format and delays are included. Two reduced CQI reporting schemes are evaluated in macro and microcell scenarios when operating in combination with a MIMO outer loop link adaptation (OLLA) and a MIMO aware frequency domain packet scheduling (FDPS) algorithm. We show that, by using OLLA and with a proper choice of the CQI reporting scheme for dual-stream MIMO, the required CQI feedback overhead can be reduced by 90% while limiting the cell throughput losses to less than 10%.

In this paper we propose a modification to Shannon capacity bound in order to facilitate accurate benchmarking of UTRAN long term evolution (LTE). The method is generally applicable to wireless communication systems, while we have used LTE air-interface technology as a case study. We introduce an adjusted Shannon capacity formula, where we take into account the system bandwidth efficiency and the SNR efficiency of LTE. Separating these issues, allows for simplified parameter extraction. We show that the bandwidth efficiency can be calculated based on system parameters, while the SNR efficiency is extracted from detailed link level studies including advanced features of MIMO and frequency domain packet scheduling (FDPS). We then use the adjusted Shannon capacity formula combined with G-factor distributions for macro and micro cell scenarios to predict LTE cell spectral efficiency (SE). Such LTE SE predictions are compared to LTE cell SE results generated by system level simulations. The results show an excellent match of less that 5-10% deviation.

In this study we analyze the downlink OFDMA system level performance for three different channel quality indicator (CQI) reporting schemes. The effect of terminal measurement and estimation errors, quantization from formatting and compression, and uplink reporting delays and detection errors are included. We find that a simple threshold-based CQI scheme provides an attractive trade-off between downlink system level performance and uplink CQI signaling overhead, as compared to using a best-M scheme. When applied to the UTRAN LTE system in a 10 MHz bandwidth, we find that a frequency domain packet scheduling gain of 40% is achievable with a CQI word size of only 30-bits. Finally, the effect of applying a so-called outer loop link adaptation algorithm is reported.

In this paper we investigate the performance of frequency domain packet scheduling (FDPS) under fractional load (FL), based on the UTRAN long term evolution downlink. Under FL, the packet scheduler does not need to transmit on entire system bandwidth due to lack of traffic in the network, which leads to an improvement in the user experienced SINR. System-level simulations show that the proportional fair scheduler tries to optimize resource allocation by avoiding transmission on frequencies that are experiencing severe interference. As an example, FDPS can provide a gain of 4 dB in SINR over the round-robin scheduler, when the load is equal to 25%. The observed interference control is achieved without any centralized management. Further, FDPS under FL can provide an effective trade-off between cell throughput and coverage. The FDPS performance is dependent on the ability of link adaptation to track variations in interference. This ability is reduced when the frequency usage pattern is changing rapidly over time.

In this paper we evaluate the performance of downlink channel dependent scheduling in time and frequency domains. The investigation is based on the 3GPP UTRAN long term evolution (LTE) parameters. A scheduler framework is developed encompassing frequency domain packet scheduling, HARQ management and inter-user fairness control. It is shown that by dividing the packet scheduler into a time-domain and a frequency-domain part the fairness between users can be effectively controlled. Different algorithms are applied in each scheduler part, and the combined performance is evaluated in terms of cell throughput, coverage, and capacity. We show that frequency-domain packet scheduling can provide a gain of around 35% in both throughput and coverage over opportunistic time-domain only scheduling. Furthermore, it is shown that by using an equal throughput scheduler, coverage can be improved by 100% at the expense of a 5% loss in average cell throughput in comparison with the proportional fair scheduler.

In this paper we investigate the effect of modelled RF transmitter impairments on UTRA Long Term Evolution (LTE) uplink link performance. Nonlinear power amplifier, gain imbalance, phase imbalance, and phase noise are considered. The main contributions of this work is assessment of the relation between Error Vector Magnitude (EVM) and link performance loss due to each impairment and the investigation of a white Gaussian noise source in the transmitter as an equivalent model of the impairment. The results obtained are based on the UTRA LTE uplink parameter settings. Results show that the EVM is a good measure to estimate the link level performance loss for numerous impairments. The performance degradation in AWGN and a frequency selective fading when using a white noise source as an equivalent transmitter RF impairment model, fits well with the other impairments in the anticipated range of EVM. An analytical formulation describing the effect of the white noise source in the SNR loss fits similarly with the simulation results. With 16 QAM rate 3/4, an EVM value of 8% corresponds to an SNR loss of approximately 0.5 dB.

This paper addresses the performance of spatial division multiplexing (SDM) multiple-input multiple-output (MIMO) techniques together with frequency domain packet scheduling (FDPS) based on UTRAN long term evolution (LTE) downlink. Two SDM concepts currently considered in 3GPP are the single-user (SU-) and the multi-user (MU-) MIMO. For MU-MIMO, multiple users can be scheduled on different streams on the same time-frequency resource, while SU-MIMO restricts one time-frequency resource to a single user. Both concepts are analyzed against the 1times2 maximal ratio combining (MRC) case, using the proportional fair (PF) criterion extended to frequency and spatial domains. The realistic finite buffer best effort traffic model is used in the study. Results show that in the macrocell scenario, the combination of FDPS and SDM (SDM-FDPS) without preceding achieves only marginal gain in cell throughput, due to limited SINR dynamic range. The gain is increased to around 20% when precoding is applied. In the micro-cell scenario, the gain of SDM-FDPS over the reference scheme is increased up to 35% with precoding.

MIMO techniques in the spatial division multiplexing (SDM) mode have demonstrated tremendous performance potential when a single user link is considered. Recent studies have shown that frequency domain packet scheduling (FDPS) can provide a significant gain when combined with SDM (SDM-FDPS) by exploiting the multi-user diversity gain over frequency as well as the spatial domains. However, the increased signaling requirements in both uplink and downlink may prevent its practical use. In this paper several effective approaches are identified for reducing the signaling requirements for SDM-FDPS while still maintaining acceptable performance. Results show that the performance loss can be kept within 10% for a uplink signaling reduction of 88% and a downlink signaling reduction of 30%.

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

In this paper we investigate the potential of downlink frequency domain packet scheduling (FDPS) for the 3GPP UTRAN long-term evolution. Utilizing frequency-domain channel quality reports, the scheduler flexibly multiplexes users on different portions of the system bandwidth. Compared to frequency-blind, but time-opportunistic scheduling, FDPS shows gains in both average system capacity and cell-edge data rates on the order of 40%. However, the FDPS performance is shown to depend significantly on the frequency-domain scheduling resolution as well as the accuracy of the channel state reports. Assuming typical urban channel profile, studies show that the scheduling resolution should preferably be as low as 375 kHz to yield significant FDPS gain with two-branch receive diversity and in 20 MHz. Further, to have convincing FDPS gain the std. of error of radio state reports needs to be kept within 1.5-2 dB

Performance evaluation of closed-loop transmit diversity (CETD) for 3GPP UTRA long term evolution (ETE) is addressed in this paper. To reduce the feedback and keep comparable performance with optimum weighting, we reduce the feedback by means of quantization and subcarrier grouping. Theoretical analysis on loss of different quantization resolution and size of groups shows the tradeoffs between signalling overhead and performance. Although CETD can bring array and diversity gain, the interaction of CETD with some of the essential features of UTRA ETE system like adaptive modulation coding (AMC)-based time domain link adaptation and hybrid ARQ may affect the attainable spectral efficiency gain from CETD. In this paper, detailed link level simulation is carried out to investigate this interaction with two transmit antennas assuming one or two receive antennas. Simulation results show that the cell level gain is quite limited for CETD, in which only 9.8% and 18% gain is observed in micro- and macro- cell respectively with two receive antennas and a grouping size of 25

In this paper, a QoS-aware packet scheduler based on the proportional fair principle is proposed and studied. The new scheduler includes robust estimation of required scheduling activity for a user to meet the QoS requirements and takes into account the cell load and individual user conditions. A framework for distributing capacity between best-effort and QoS users is embedded in the scheduling algorithm. For a given QoS target and a WCDMA/HSDPA system, the scheduler provides around 40% user capacity gain compared to the well-known QoS-aware proportional fair scheduler based on barrier function scaling. While being better at guaranteeing QoS compared to the reference scheduler, it simultaneously provides orders of magnitude larger gain in what throughput is delivered to best- effort users in a mixed-service scenario. A main advantage of the scheduler is its simplicity and inherent robustness which makes it easy to configure in a multi-user/service environment.

The functional split between the centralized radio network controller (RNC) and the base station (node-B) presents new challenges and opportunities for implementing QoS control for HSDPA. In this paper we present different options for implementing QoS over HSDPA, and we focus particularly on the shared responsibility between the QoS aware algorithms at the RNC and the node-B. Different strategies for QoS aware node-B packet schedulers are discussed. The paper is concluded with network performance results for different services over HSDPA, ranging from simple best effort traffic, to constant bit rate streaming, and voice over IP. For these services we show capacity gains of up to 40% from using QoS-aware packet scheduling.

This paper evaluates spectral efficiency performance of the 3GPP Evolved UTRA (E-UTRA) downlink with baseline settings. A detailed link level tool has been developed including the majority of 3GPP E-UTRA link chain processing modules such as time-domain link adaptation and LI HARQ. Since MIMO is an integral part of the new system, we include four basic multiple antenna configurations in the analysis, namely the SISO, 1x2 SIMO, 2x2 SFC and 2x2 BLAST schemes. Since the BLAST is very sensitive to channel estimation error in cell edge, a case denoted as adapMIMO is considered as well, where the SFC is taken as a backup for the BLAST in cell edge. The system bandwidth is fixed at 20 MHz and a Typical Urban channel model is assumed for both macrocell and microcell evaluations. Simulation results show that in macrocell scenario, the spectral efficiency performance gain of SIMO over SISO is up to 54%, while SFC shows an additional gain of 14% over SIMO. Although the adapMIMO scheme has similar performance as SFC in the macrocellular case, it produces about 30% spectral efficiency gain in the microcell scenario.

This paper addresses the potential gain of including MIMO adaptation into Link adaptation (LA) Layer. Theoretical analysis is carried out from a new perspective, namely the distribution of unified instantaneous signal to interference and noise ratio (unified SINR) which encompasses MIMO schemes with different number of effective spatial streams and/or different receiver structures. Based on that, the capacity of LA including MIMO adaptation is formulated. Besides the theoretical analysis, issues concerning the practical application of LA including MIMO adaptation are discussed. A two dimensional lookup table (LUT) based on average SINR and SINR ratio is investigated for the selection of MIMO, modulation and coding set every transmission time interval. Results from simulations with real time domain LA show that significant spectral efficiency gain can be achieved as compared to the case of LA without MIMO adaptation.