Radio resource management (RRM) relaxation has been introduced in 3GPP NR Release 16 as a key feature for optimizing UE power saving. It can be applied for UEs under “low mobility” and “cell edge” criteria. In this study, we investigate its benefit in addition to discontinuous reception (DRX) for reduced capability (RedCap) new radio (NR) UEs, a new type of low-cost device, for which the power saving is a key requirement. We provide comprehensive simulation results that quantify energy saving by applying RRM relaxation for stationary and pedestrian RedCap UEs with different “cell edge” criteria and DRX settings. In addition, we evaluate the impact in terms of handover failures and packet delay. The simulation analysis shows that dynamic adjustment of “cell edge” criteria of RRM relaxation is a more power-efficient solution that can achieve up to 64% to 96% RRM measurement energy saving.

The first release of 5G NR (Rel-15) supports Internet of Things (IoT) use cases including ultra-reliable low-latency as well as massive machine type communications. In Rel-17, reduced capability devices are being introduced to support mid-range IoT use cases such as industrial wireless sensors, wearables, and video surveillance. These use cases require low-cost devices to support high reliability, low latency, medium data rate, and long battery life despite being low complexity in design. In this paper, we provide an overview of these devices and describe important features being standardized in 3GPP for complexity reduction, coverage compensation, and power saving.

The support for Internet of Things (IoT) has evolved over several successive releases of standard specifications in 3GPP. As a result, eMTC and NB-IoT are mature 4G wireless technologies that are seeing largescale deployment. Thus, even as 4G systems migrate to 5G New Radio (NR) technology, there is a strong motivation to continue to support eMTC devices through efficient deployment of eMTC within a 5G NR carrier. In 3GPP, studies are underway to identify and rectify issues related to coexistence between eMTC and NR systems. This paper presents an analysis of such coexistence considering various aspects. The analysis demonstrates that the issues affecting coexistence can generally be handled through implementation. The paper also discusses several mechanisms for achieving improved performance with coexistence.

Ultra-Reliable and Low Latency Communications (URLLC) is an important emerging area for the fifth generation (5G) cellular network. The requirements for URLLC are as stringent as 1-10-5reliability for a 32-byte packet with user plane latency of 1 ms. To achieve these requirements, grant-free transmission with repetitions of data packet has been recently proposed for uplink transmissions. However, the resource overhead and collisions among URLLC user equipments (UEs) become limiting factors to achieving optimal system performance. In this work, a hybrid resource allocation scheme is proposed to optimally allocate dedicated resource units and/or a shared resource pool to a group of UEs. Numerical results based on theoretical analysis show that the target requirements of URLLC can be achieved with up to 70% reduction in resource utilization compared to the conservative transmission scheme.

This paper provides an updated analysis of link-budget and coverage performance for LTE IoT technologies: enhancements for machine type communications (eMTC) and narrowband Internet of Things (NB-IoT). Previous studies have used the 3GPP evaluations assumptions and have demonstrated the coverage capabilities of these technologies when they are independently deployed. Some operators are, however, likely to deploy dual-mode networks - eMTC and NB-IoT - with the intent of supporting different applications in the two systems. With all conditions being equal for the two systems in such a scenario, comparison of the eMTC and NB-IoT technologies then requires that all assumptions are aligned. This paper extends the previous studies with the assumptions aligned for eMTC and NB-IoT systems to provide a fair coverage performance comparison. The study shows that compared to the 3GPP assumption, under the aligned assumptions, both eMTC and NB-IoT can support up to 5dB and 3dB higher uplink coverage, respectively. We further show these link budget improvements yield significantly reduced LTE IoT coverage outage in two simulated scenarios based on real network deployments: a wide area rural case and an urban deep indoor case. The results further demonstrate the potential of these LTE IoT technologies in realistic network deployment conditions.

There is an expected explosion in the number of users which will be connected to future wireless networks with the continued expansion of the Internet of Things. New technologies are needed in order to keep up with this connectivity demand. Non-orthogonal multiple access (NOMA) is one technology which seeks to improve spectral efficiency and allow for more connected users. NOMA seeks to overload resources in order to allow more users to access the same time and frequency resource blocks. There have been various proposals on how to realize NOMA in the network, including power domain non-orthogonal multiple access (PD-NOMA), interleave division multiple access(IDMA), and sparse code multiple access (SCMA). This paper investigates these three proposals and simulates them in the uplink setting in order to analyze their performance and compare them. Advantages and disadvantages for each technique are discussed with an emphasis on practical considerations.

The Internet of Things (IoT) is expected to reach a massive scale in the next few years and LTE has introduced a feature in Rel-13 called eMTC to support wide-area connectivity for IoT devices. One important trend for IoT is the integration of voice capability into the devices. However, low-cost, low-complexity IoT User Equipment (UE) typically supports only half-duplex communication and low data rates. In this paper, we compare the performance and coverage of low-complexity eMTC UE with legacy non-eMTC UE for delay-sensitive Voice over LTE (VoLTE) service. It is shown that eMTC UE can provide similar coverage to non-eMTC UE using the same delay and block error rate requirements. If the delay budget or quality of service can be relaxed for eMTC, then eMTC can provide slightly better VoLTE coverage. This allows service operators to support voice capability for IoT devices using existing infrastructure footprint.

In 3GPP Rel-13, a narrowband wide-area cellular system, named Narrowband Internet of Things (NB-IoT), has been introduced to provide low-cost, low-power connectivity for the Internet of Things. This system, based on Long Term Evolution (LTE) technology, can be deployed in three operation modes - in-band within LTE carrier, in the guard-band of LTE carrier, and stand-alone. Guard-band deployment allows the operator to support NB-IoT without requiring new spectrum and with minimal impact to LTE. This paper provides an overview and presents a study of NB-IoT deployment in LTE guard band. An analysis of coexistence of NB-IoT with LTE is presented and demonstrates that while there is mutual interference between NB-IoT and LTE on the uplink, the impact on either system is small. A performance analysis of NB-IoT is also presented. The link budget analysis demonstrates how the coverage target can be achieved for the uplink and downlink data channels. Illustrative uplink and downlink link-level simulation results are provided. The analysis in the paper shows that guard-band operation of NB-IoT is feasible and can provide support for massive number of low-throughput IoT devices.

In 3GPP, a narrowband system based on Long Term Evolution (LTE) has been introduced to support the Internet of Things. This system, named Narrowband Internet of Things (NB-IoT), provides low-cost devices, high coverage (20 dB improvement over LTE/GPRS), long device battery life (more than 10 years), and massive capacity. Latency is relaxed although a delay budget of 10 seconds is the target for exception reports. NB-IoT can be deployed in three different operation modes - (1) stand-alone as a dedicated carrier, (2) in-band within the occupied bandwidth of a wideband LTE carrier, and (3) within the guard-band of an existing LTE carrier. In this paper, we undertake a deployment study of NB-IoT using existing LTE infrastructure. We consider the case when only a fraction of the existing LTE cell sites support NB-IoT (so called partial deployment of NB-IoT). In this case, NB-IoT devices cannot attach to the best cell if that cell does not support NB-IoT. As a result, the path loss can be very high. In addition, they also suffer from high interference from non-NB-IoT cells. We examine potential techniques to compensate for the high path-loss and high interference and provide analysis to indicate when partial deployment of NB-IoT is feasible. We also examine interference issues in asynchronous deployments and study performance.

In-band full-duplex communication has been proposed as a technique in 5G to increase spectral efficiency. Traditionally full duplex wireless communication has been considered very challenging due to large self-interference that is generated. However in recent years researchers have begun to challenge this assumption with breakthroughs in self- interference cancellation (SIC). Most work on full duplex up to this point has been focused on point to point communication links and relatively little work has looked into the system level challenges. One of the largest unanswered questions about full duplex is whether it is a viable technology for access in future cellular networks. The main concern with deploying full duplex is how the additional interference will affect the system performance. In this paper, SIC will be modeled and link level simulations will be presented showing that full duplex only slightly degrades the uplink frame error rate performance of a full duplex capable eNB. These results will then be used to determine an appropriate link to system mapping for full duplex. From there multiple cellular system deployment scenarios will be investigated and the feasibility of full duplex will be explored. It will be shown that for Indoor Hotspot (InH) deployment scenario 20 percent sum throughput gain can be achieved with full duplex capability. For the outdoor scenari-os full duplex can grant up to 20 percent gains and 3 percent gains for the Urban Micro (UMi) and Urban Macro (UMa) deployment scenarios respectively depending upon the amount of sectorization used. Based on these initial results and some of the assumptions used it will be concluded that full duplex is challenging for outdoor access and may only be viable for indoor scenarios and other use cases (e.g. backhaul, unlicensed spectrum).

In 3GPP Rel-13, a narrowband system based on Long Term Evolution (LTE) is being introduced to provide wide-area cellular connectivity for the Internet of Things. This system, named Narrowband Internet of Things (NB-IoT), can be deployed in three different operation modes - (1) stand-alone as a dedicated carrier, (2) in-band within the occupied bandwidth of a wideband LTE carrier, and (3) within the guard-band of an existing LTE carrier. The design targets of NB-IoT include low-cost devices, high coverage (20-dB improvement over GPRS), long device battery life (more than 10 years), and massive capacity. Latency is relaxed although a delay budget of 10 seconds is the target for exception reports. This paper discusses the design and performance of the downlink and uplink data channels. Although the design of these channels is based on LTE, there are some differences, particularly in the uplink, with the introduction of subcarrier-level transmission. The similarities have enabled rapid specification, while the enhancements in the design enable the achievement of the stated targets for NB-IoT.

In 3GPP, a narrowband system based on Long Term Evolution (LTE) is being introduced to support the Internet of Things. This system, named Narrowband Internet of Things (NB-IoT), can be deployed in three different operation modes - (1) stand-alone as a dedicated carrier, (2) in-band within the occupied bandwidth of a wideband LTE carrier, and (3) within the guard-band of an existing LTE carrier. In stand-alone operation mode, NB-IoT can occupy one GSM channel (200 kHz) while for in-band and guard-band operation modes, it will use one physical resource block of LTE (180 kHz). The design targets of NB-IoT include low-cost devices, high coverage (20-dB improvement over GPRS), long device battery life (more than 10 years), and massive capacity. Latency is relaxed although a delay budget of 10 seconds is the target for exception reports. The specifications for NB-IoT are expected to be finalized in 2016. In this paper, we describe the targets for NB-IoT and present a preliminary system design. In addition, coverage, capacity, latency, and battery life analysis are also presented.

This paper investigates the impact of radar interference on LTE by directly injecting narrow-band radar waveforms into a state of the art LTE down-link simulator. We show detailed results demonstrating the impact of interference on various parts of LTE signaling including reference symbols. Then we show how the presence of radar interference causes errors in the noise and interference estimates, impacts decoding in the LTE soft decoder, and ultimately leads to erroneously received Sub-frames. We propose a mechanism to combat such interference and improve LTE throughput in the presence of narrow-band radar using selective erasures. We simulate the proposed scheme and show that it is extremely effective in mitigating narrow-band interference and realizing the throughput expected from LTE.

The Internet of Things will bring about billions of connected devices. In the cellular space, machine type communications using LTE is under consideration by many operators. LTE, however, was designed to provide broadband high-speed data service with very low latency. Machine type communications, on the other hand, have a different set of requirements, namely low-rate, low-overhead, low-power-consumption, and low-cost. To address these requirements and also to minimize impact from machine traffic to human traffic, 3GPP has been working on numerous LTE features such as power saving, overload control, signaling reduction, complexity reduction, and coverage enhancement. This paper will provide an overview of LTE enhancements for machine type communications. The paper will also present LTE capacity analysis for machine traffic as well as the battery life of the devices.

Deployment of LTE in unlicensed bands is being considered in Rel-13 of LTE. This feature is called Licensed-Assisted Access (LAA) using LTE. Unlicensed band is attractive due to the large amount of available spectrum. However, in shared spectrum the coexistence between LAA and WiFi systems becomes a primary challenge. This paper presents an analytical framework to investigate the downlink coexistence performance between two systems with a simple listen-before-talk (LBT) mechanism enforced on LAA. Using this framework, theoretical models based on Markov chains are established for both systems and downlink throughput can be calculated. Numerical results from the models show that the simple listen-before-talk scheme is very effective in LAA and LAA coexistence scenario (i.e. two LAA systems sharing the same spectrum). In LAA and WiFi coexistence scenario, it can improve WiFi performance substantially.

Device-to-device (D2D) communication is a new feature being introduced to LTE in 3GPP Release 12. This feature will provide proximity services including support for public safety applications. For D2D communication within the network coverage area, network assistance is very beneficial for interference management purpose to ensure reliable communication. In this case, a simple algorithm can be used wherein the network manages the number and selection of simultaneous D2D transmissions within its cell. This will help manage interference from D2D transmission in case of time-frequency reuse to ensure that minimum performance requirement can be satisfied. In this paper, we outline a method for determining the maximum number of simultaneous D2D transmitters in a given cell. In addition, a method for selecting D2D pairs for simultaneous transmission is also provided. It is shown that, with network assistance, the percentage of reliable D2D communication links can be improved significantly.

The Internet of Things will bring billions of devices that are inter-connected using cellular networks. LTE cellular systems are being deployed worldwide and will remain in place for the foreseeable future. However, LTE was designed for high data-rate broadband services. Even with M2M features being added in LTE Rel-12, it is not optimized for low data-rate and wide area M2M services such as smart meters, remote sensors, and consumer devices. In this paper, we present a design of a new narrowband M2M system built from existing LTE functionalities for Low Power Wide Area (LPWA) systems. Salient features of this new system include low-cost devices, high coverage, long device battery life, and high capacity. It can be deployed using minimum of one GSM channel and can also share spectrum with existing broadband LTE systems. Cost analysis shows significant reduction compared to LTE UEs. In addition, coverage analysis and capacity results are presented. Finally, coexistence with GSM is analyzed.

Wireless data traffic is projected to skyrocket 10 000 fold within the next 20 years. To tackle this incredible increase in wireless data traffic, a first approach is to further improve spectrally efficient systems such as 4G LTE in bands below 6 GHz by using more advanced spectral efficiency techniques. However, the required substantial increase in system complexity along with fundamental limits on hardware implementation and channel conditions may limit the viability of this approach. Furthermore, the end result would be an extremely spectrally efficient system with little room for future improvement to meet the ever-growing wireless data usage. The second approach is to move up in frequency, into an unused nontraditional spectrum where enormous bandwidths are available, such as at millimeter wave (mmWave). The mmWave option enables the use of simple air interfaces since large bandwidths can be exploited (e.g., 2 GHz) to achieve high data rates rather than relying on highly complex techniques originally aimed at achieving a high spectral efficiency with smaller bandwidths. In addition, mmWave systems will easily evolve to even higher system capacities, because there will be plenty of margin to improve the spectral efficiency as data demands further increase. In this paper, a case is made for using mmWave for a fifth generation (5G) wireless system for ultradense networks by presenting an overview of enhanced local area (eLA) technology at mmWave with emphasis on 5G requirements, spectrum considerations, propagation and channel modeling, air-interface and multiantenna design, and network architecture solutions.

Multicast device-to-device (D2D) transmission is important for applications like local file transfer in commercial networks and is also a required feature in public safety networks. In this paper we propose a tractable baseline multicast D2D model, and use it to analyze important multicast metrics like the coverage probability, mean number of covered receivers and throughput. In addition, we examine how the multicast performance would be affected by certain factors like dynamics (due to e.g., mobility) and network assistance. Take the mean number of covered receivers as an example. We find that simple repetitive transmissions help but the gain quickly diminishes as the number of repetitions increases. Meanwhile, dynamics and network assistance (i.e., allowing the network to relay the multicast signals) can help cover more receivers. We also explore how to optimize multicasting, e.g. by choosing the optimal multicast rate and the optimal number of retransmission times.

Heterogeneous networks (HetNets) and carrier aggregation (CA) are two distinct features of next-generation cellular networks. Small cells in HetNets are vital for data off-loading and can significantly improve area and cell edge spectral efficiency compared to using just macrocells. CA further increases the transmission bandwidth and thus network capacity by aggregating multiple component carriers on the physical layer. In this paper, we propose a tractable multi-band multi-tier model to study multi-flow CA in HetNets, where base station positions in each tier follow an independent Poisson point process. Our model incorporates an appropriate notion of load which allows the study of the impact of biasing on HetNet performance. For a typical HetNet consisting of two tiers, macro cells and small cells, and two bands, 800MHz band and 2.4GHz band, we observe that the gain (in terms of UE ergodic rate) is about 35% to 40% if the small cells adopt optimal biasing factor compared to the case without biasing. Our model also incorporates the impact of band deployment. For the typical HetNet described, our study suggests that deploying the 800MHz band and 2.4GHz band in both the macro and small cells helps the HetNet best exploit the CA feature.

Availability of large untapped spectrum resources in the millimeter wave (Mmwave) band is suitable for providing a gigabit experience with true local feel using high capacity small cells. Unlike traditional cellular systems, millimeter wave transmissions do not benefit from diffraction and dispersion making it difficult for them to propagate around obstacles thus resulting in higher shadowing loss. They also have less favorable link budgets due to lower power amplifier (PA) output powers and greater pathloss at these higher frequencies. Also, current costs of the Mmwave circuits are higher, but the costs will become much lower when the technology becomes mainstream. One advantage of millimeter wave, however, is that the smaller wavelengths allow for the fabrication of antenna arrays having a much higher number of antenna elements in a much smaller area than is typical at microwave bands. In this article, we outline a framework for Beyond-4G (B-4G) local area network in the millimeter wave band for both access and backhaul including air-interface, antenna-arrays and IC technology. It is shown that Mmwave B-4G small cell technology can provide peak and cell edge rates greater than 10 Gbps and 100 Mbps respectively with latency less than 1msec for local area network.

Machine type communications (MTC) is defined as data communication among devices without the need for human interaction. With the decommissioning of legacy cellular systems, migration of MTC devices to LTE is under investigation by many operators. It is desirable that the cost of LTE MTC devices is similar to that of existing GSM devices. Several cost reduction techniques have been studied. This paper summarizes cost reduction techniques for MTC devices and examines system impacts from such devices being introduced in LTE. Performance is evaluated for the Advanced Metering Infrastructure used in smart grid. It is seen that LTE offers significant capacity for smart metering even with low-cost devices. For a system with 10 MHz bandwidth, approximately 2% of the system resource is required to support AMI in an urban deployment scenario.

This paper presents the system performance analysis of 3GPP Long-Term Evolution (LTE) and IEEE 802.11 Wireless Local Area Networks (WLAN) in a situation where LTE downlink (DL) has been expanded over to unlicensed frequency band usually used by WLAN. Simple fractional bandwidth sharing mechanism is used to allow both technologies to transmit. The system performance is evaluated by means of fully dynamic network simulations.

Machine type communications (MTC) is defined as data communication among devices without the need for human interaction. Examples of MTC services include security, tracking, payment, smart grid, and remote monitoring. With the widespread introduction of LTE and decommissioning of legacy systems, migration of MTC devices to LTE is under investigation by many cellular operators. This paper examines LTE uplink coverage and capacity for machine type communications. It is seen that LTE provides similar coverage to other cellular systems but significantly higher capacity for MTC services. Capacity, however, may be significantly reduced for devices with lower maximum transmit power devices or QPSK-only modulation. MTC on LTE is also shown to be robust to interference and can be deployed in unlicensed band with only a moderate reduction in capacity.

In LTE Rel-8, mobile stations are equipped with only one transmit antenna while the base stations can employ multiple receive antennas. As a result, multi-user MIMO can be used in the uplink to enhance system capacity. This paper describes multi-user MIMO in the uplink for LTE and presents system-level simulation results under indoor hotspot, micro-cell, and macro-cell deployment scenarios. Two user pairing strategies, random and orthogonal pairing, are compared. Our results show that random pairing performs as well as orthogonal pairing under realistic implementation constraints. With four receive antennas at the base station, uplink MU-MIMO can increase cell capacity by approximately 30% in indoor hotspot, and 10% in micro-cell and macro-cell deployment. Corresponding improvements in user throughput are also observed, including a gain of between 9-28% in cell edge user throughput.

UMTS LTE system can support flexible bandwidth configuration up to 20 MHz. Currently, system enhancements are being considered to provide substantial improvements to LTE and allow it to meet or exceed IMT-Advanced requirements. One key enhancement feature is bandwidth extension via carrier aggregation to support deployment bandwidth up to 100 MHz. This will allow peak target data rates in excess of 1 Gbps in the downlink and 500 Mbps in the uplink to be achieved. Carrier aggregation is attractive because it allows operators to deploy a system with larger bandwidth by aggregating several smaller contiguous or non-contiguous carriers while providing backward compatibility to legacy users. For instance, an 80 MHz system can be constructed using contiguous or non-contiguous 4 × 20 MHz component carriers. Legacy users can then access the system using one of the component carriers. This paper provides an overview of carrier aggregation and discusses major technical issues including aggregation structure, scenarios, implementation, control signalling design and coexistence with legacy LTE systems.

Long-term evolution (LTE) of the UMTS network provides improved system capacity and coverage, high peak data rates, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operations and seamless integration with existing systems. To achieve these enhancements, a new design for the air interface including state-of-art multi-antenna technology was developed. This article describes multi-antenna schemes for UMTS LTE and provides system performance of different multi-antenna schemes under various scenarios.

Long-Term Evolution (LTE) will provide substantial enhancements to UMTS 3G systems including improved system capacity and coverage, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operations and seamless integration with existing systems. LTE supports both Frequency Division Duplex (FDD) and Time Division Duplex (TDD) modes to provide deployment flexibility in accordance with operator’s preference and spectrum allocation. This paper presents an overview of LTE TDD design and highlights key differences with FDD. Design challenges unique to TDD are presented together with adopted technical solutions. Finally, simulation results are provided to demonstrate typical TDD system performance with data applications.

The performance of the uplink physical channel of the 3GPP LTE system is considered in this paper. Assuming a single user spatial division multiple access transmission scheme, where users' signals are transmitted over different subcarriers, a low complexity channel estimation technique is proposed for the physical uplink shared channel (PUSCH). The proposed channel estimation technique is shown to have significant gains in performance compared to other well known channel estimation techniques such as the maximum-likelihood (ML) and the inverse fast Fourier transform (IFFT) channel estimation methods [5]. Simulation results for different channel models and modulation and coding schemes (MCS) using incremental redundancy (IR) based hybrid automatic repeat request (HARQ) operation are also shown. Finally, a robust detection scheme is proposed for the physical uplink control channel (PUCCH) and simulation results are summarized.

With the emergence of packet-based wireless broadband systems, work has begun on long term evolution (LTE) of the UMTS Terrestrial Radio Access and Radio Access Network aimed for commercial deployment in 2010. Goals for the evolved system include support for improved system capacity and coverage, high peak data rates, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operations and seamless integration with existing systems. To reach these goals, a new design for the air interface including control channel is envisioned. This paper provides a preliminary look at an efficient downlink control channel design to reduce the overhead required to support data transmission. Initial performance results show that close to optimal system performance can be achieved with downlink control overhead of less than 14%.

Long term evolution (LTE) of the UMTS Terrestrial Radio Access and Radio Access Network is aimed for commercial deployment in 2010. Goals for the evolved system include support for improved system capacity and coverage, high peak data rates, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operations and seamless integration with existing systems. To reach these goals, a new design for the air interface is currently being specified in the 3GPP standards body. The Uplink (UL) for LTE is based on Single Carrier Frequency Division Multiple Access. The UL control channel carries non-data associated control signaling like CQI, ACK/NACK, Scheduling request etc. To maintain the low PA power de-rating, the single carrier property of the UL has to be maintained. As such, special consideration should be given to the UL control channel design. This paper discusses in detail the LTE UL control channel design and its performance.

Comprehensive long term evolution of the Universal Mobile Telecommunications System (UMTS) specifications is currently ongoing to provide significant improvement over the current release. Important goals for the evolved system include significantly improved system capacity and coverage, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operations and seamless integration with existing systems. To ensure low latency, users must be able to establish a connection to the network quickly. This paper provides a preliminary design and procedure for the random access channel used to establish a connection when the mobile is not yet time-synchronized to the network in the uplink.

With the emergence of packet-based wireless broadband systems such as 802.16e, it is evident that a comprehensive evolution of the universal mobile telecommunications system specifications is required to remain competitive. As a result, work has begun on long term evolution (LTE) of the UMTS terrestrial radio access and radio access network aimed for commercial deployment in 2010. Goals for the evolved system include support for improved system capacity and coverage, high peak data rates, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operations and seamless integration with existing systems. To reach these goals, a new design for the air interface is envisioned. This paper provides a preliminary look at the air interface for Evolved UTRA (E-UTRA) and associated key technologies required to reach its design objectives. Initial E-UTRA system performance results show a 2 to 3x improvement over a reference Rel-6 UMTS system configuration [1, 2] for both uplink and downlink.

Multi-user scheduling and OFDM techniques are well regarded as promising candidates to provide high data- rate and reliable transmissions in future communication systems. To optimally exploit multi-user diversity and frequency selectivity, exhaustive channel information is needed for every user - an impracticality given limited feedback bandwidth. Simple and efficient feedback schemes therefore become a crucial task in designing a next generation standard. In this paper, two near-optimal feedback schemes are proposed that achieve most of the multi-user scheduling benefit with very few feedback bits. It is also shown that the feedback schemes are robust to long feedback intervals. As expected, at higher Doppler spread, the performance gap using the proposed schemes becomes larger but still provides satisfactory performance.

Evolved UTRA and UTRAN is being standardized in 3GPP standard group as a long term evolution of the 3GPP radio-access technology. The goal is to achieve 2-4 times the spectral efficiency and user throughput and much smaller latency compared to HSDPA/HSUPA. Single carrier FDMA (e.g. DFT-SOFDM) is the multiple access technique of choice for uplink transmission. Interference control is one of the key elements to achieve the target spectral efficiency and user cell- edge performance requirement, especially for uplink. In this paper, interference mitigation is implemented through slow fractional power control and interference coordination through UE alignment and FDM resource allocation. Simulation results show that these techniques significantly improve uplink sector and cell edge user throughput performance.

In this paper, the performance of a prototypical IEEE 802.16e network is analyzed via link and system simulations. The exponential effective SIR mapping (EESM) is used to map the instantaneous SINR of received signals to a service-specific packet erasure rate (PER), which is in turn used to assess the downlink and uplink network and user data throughput. A variety of data traffic models are considered, including web browsing (HTTP) and full buffer sessions, operating in flat-fading and frequency-selective multipath channels such as the ITU Pedestrian-B model. The downlink network performance of the prototypical IEEE 802.16e network is compared to a 3GPP UMTS high speed downlink packet access (HSDPA) system of similar physical dimensions. System simulation results for the prototypical IEEE 802.16e network considered show-when frequency-selective scheduling is not applied-that the IEEE 802.16e downlink has similar throughput performance as HSDPA for a 70/30 TDD DL/UL frame split but approximately 40%-50% higher spectral efficiency, although control channel overhead and uplink capacity limitation remain significant open issues for further study

Enhanced Uplink technology is being standardized in Release-6 of 3GPP W-CDMA specifications with the completion date of 2nd quarter of 2005. Advanced features being introduced include adaptive modulation and coding, Hybrid ARQ, fast rate control or scheduling by the base station, higher peak rates (5.76 Mbps) and support of 2ms TTI. These techniques reduce overall delay and increase throughput significantly compared to earlier releases of 3GPP W-CDMA (Release-99/ 4/ 5). As a result, Enhanced Uplink will significantly improve the user mobile experience and enable new services and applications. In this paper, the scheduling and resource allocation aspects of Enhanced Uplink are discussed with accompanying analysis and system simulation results. These results show that Enhanced Uplink improves sector and user throughput by approximately 50-80% compared to earlier 3GPP W-CDMA releases.

We analyze the throughput of a combined hybrid-ARQ and link adaptive packet data transmission system. An analytical approach is used to develop a method for selecting transmit data rates that will maximize system throughput based on available channel state information and the maximum number of allowable transmissions. Performance of the system in the presence of channel estimation errors is also analyzed. Our results show that the availability of channel state information improves system performance significantly, especially under slowly fading channels or when the maximum number of transmissions allowed is small. We also show that, at low SNR, significant gain can be achieved by incorporating the knowledge of TV, the maximum allowable number of transmissions, into our data rate selection process. In addition, comparison to simulation results demonstrates that this approach can also be used to accurately evaluate performance of practical systems.

The large-system performance of iterative multiuser decision-feedback detectors (DFDs) is studied for synchronous coded direct-sequence code-division multiple access. Both successive and parallel demodulation of users are considered. The filters are optimized according to the minimum mean-squared error criteria, assuming perfect feedback. We first consider Viterbi decoding with hard decision feedback, and compute union bounds on the large-system error rate. We then consider maximum a posteriori (MAP) decoding with soft decision feedback, and evaluate the error rate semianalytically by assuming the log-likelihood ratios computed by the MAP decoder are Gaussian random variables. Performance is studied numerically as a function of noise level, spectral efficiency, and code rate. Results show that soft decision feedback gives substantial gains relative to hard decision feedback. At moderate spectral efficiencies (users divided by bandwidth expansion less than 0.9), the iterative DFDs with soft decision feedback based on a posteriori probabilities can achieve near-single-user performance at an E/sub b//N/sub 0/ close to the large-system capacity bound.

The paper compares two hybrid automatic repeat request (HARQ) schemes using incremental redundancy (IR) which have been proposed for the UMTS (W-CDMA) high speed downlink shared channel (HS-DSCH). Their relative throughput performance is reported for various channel conditions. It is shown that the two-stage rate-matching scheme has marginally worse performance compared to the alternative block interleaving scheme for certain coding rates and under some channel conditions.

In this paper, we investigate the performance of a quasi-static method used to predict link-level error performance in dynamic system simulations. Two flavors of the quasi-static approach are used to model the link characteristics: (a) static curves with fudge factors; and (b) short-term frame error curves. For the fudge factor based method, we examine the various factors (or penalties) required for the method to work properly, their limitations in capturing the various features of the high-speed packet data channel, and their effects on the overall accuracy of the technique. Here, we concentrate on three important penalties: puncturing penalty, Doppler penalty, and demapping penalty. The quasistatic method based on short-term frame error curves is used to generate frame erasures for voice and control channels associated with high-speed packet data channels. From simulation results, it is shown that both variations of the quasi-static method can provide accurate prediction of link-level performance at certain operating ranges, provided that the penalties are correctly obtained. At low frame error rates and moderate to high speeds, however, the quasi-static method often fails to accurately reflect frame error performance at the link level.

Multiuser decision-feedback detectors (DFDs) for direct-sequence code-division multiple access, based on the minimum mean-squared error (MMSE) performance criterion, are described. Both successive and parallel feedback (interference cancellation) with hard decisions are considered. An iterative DFD is presented, which consists of cascaded DFDs, each performing successive cancellation. The two-stage DFD achieves the single-user bound in the absence of error propagation, and performs significantly better than an MMSE DFD with parallel feedback. The filter structures are generalized to include finite impulse response feedforward and feedback matrix filters, which account for asynchronous users and intersymbol interference. The effect of error propagation is illustrated through simulation. Both uncoded and coded performance results are presented. Although error propagation can significantly degrade performance, the DFDs still offer a significant performance gain relative to linear MMSE detection.

Multiuser decision-feedback detectors (DFDs) for DS-CDMA are presented using the minimum mean squared error (MMSE) criterion. Both successive and parallel feedback (interference cancellation) are considered. Short spreading codes are assumed, eliminating the need for remodulation. A multi-stage DFD is presented which consists of cascaded DFDs each performing successive cancellation. In the absence of error propagation, a two-stage structure achieves the single-user bound for all users, and is shown to be equivalent to an MMSE DFD with parallel feedback. The effect of error propagation is illustrated through simulation. Both uncoded and coded performance results are presented. These results show that the DFDs can offer a significant performance gain relative to linear MMSE detection.