3GPP Long Term Evolution Research Articles

Разработка и анализ системы с множеством излучателей и множеством приёмников для исследовательских целей

Systems with multiple input and multiple output (MIMO) play a key role in modern wireless communication devices. MIMO are used in wireless networks to increase channel throughput and transmission reliability. The implementation of the MIMO system will speed up research in the field of improving communication systems. In this article, we present a system-level analysis of a block level analog RF receiver in a MIMO system in accordance with the performance requirements described in the 3GPP Long-Term Evolution standard. An analytical study of the analog receiving part was carried out. The results show that the proposed system architecture satisfies the given requirements with a good margin. Numerical simulation of the operation of the 44 MIMO system in the line-of sight environments was performed. Taking into account the influence of only the noise of the receiver, a curve is obtained that determines the dependence of the error probability on the distance between the transmitter and receiver. Using this curve, it is possible to determine the distance corresponding to a given error probability for given aperture sizes of the transmitting and receiving arrays.

Precoding Matrix Selection for LTE System

In the current 4G Long Term Evolution (LTE) system, it adopts the orthogonal frequency division multiplexing (OFDM) and multiple input multiple output (MIMO) schemes to improve the spectral efficiency and increase the data rate for the system. Besides, precoding is an effective technique in MIMO transmission for the transmitter (Tx) to use a suitable precoding matrix in accordance with the change of the channel. With the proper selected precoding matrix, MIMO system can reduce the multiple access interference and increase the received signal to noise ratio (SNR) at the receiver (Rx). In this paper, two precoding matrix selection methods are proposed via using the features of the beam patterns of the adopted precoding matrices for 3GPP LTE system. With a little performance degradation, the first proposed method has the advantage of low computational complexity and the second method can have the zero latency property compared with the conventional full search methods.

Investigations on scheduling algorithms in LTE-advanced networks with carrier aggregation

Third generation partnership project (3GPP) long-term evolution advanced (LTE-A) is the fastest growing technology, which supports variety of applications by using effective and efficient radio resource management (RRM) procedure. With carrier aggregation (CA) concepts included in LTE-advanced protocol, the complexity of the RRM and scheduling of data increases. In this paper, basic LTE-A concepts and a study of different methods of component carrier allocation is studied and performance evaluation is carried out. From the simulation results, it can be inferred that static methods of component carrier allocation is simple but it could not be able to satisfy various important scheduler metric to provide a better QoS to UE. The random method though for some cases it seen better but it is not reliable as the outputs are also random. The dynamic methods of component carrier allocation have been able to provide better scheduler performance metric compared to static and random methods. More over different dynamic approaches can be also combined to improve the overall system efficiency.

Semi-Blind Post-Equalizer SINR Estimation and Dual CSI Feedback for Radar-Cellular Coexistence

Current cellular systems use pilot-aided statistical-channel state information (S-CSI) estimation and limited feedback schemes to aid in link adaptation and scheduling decisions. However, in the presence of pulsed radar signals, pilot-aided S-CSI is inaccurate since interference statistics on pilot and non-pilot resources can be different. Moreover, the channel will be bimodal as a result of the periodic interference. In this paper, we propose a max-min heuristic to estimate the post-equalizer SINR in the case of non-pilot pulsed radar interference, and characterize its distribution as a function of noise variance and interference power. We observe that the proposed heuristic incurs low computational complexity, and is robust beyond a certain SINR threshold for different modulation schemes, especially for QPSK. This enables us to develop a comprehensive semi-blind framework to estimate the wideband SINR metric that is commonly used for S-CSI quantization in 3GPP Long-Term Evolution (LTE) and New Radio (NR) networks. Finally, we propose dual CSI feedback for practical radar-cellular spectrum sharing, to enable accurate CSI acquisition in the bimodal channel. We demonstrate significant improvements in throughput, block error rate and retransmission-induced latency for LTE-Advanced Pro when compared to conventional pilot-aided S-CSI estimation and limited feedback schemes.

Investigations on Scheduling Algorithms in LTE-Advanced Networks with Carrier Aggregation.

Third generation partnership project (3GPP) long-term evolution advanced (LTE-A) is the fastest growing technology, which supports variety of applications by using effective and efficient radio resource management (RRM) procedure. With carrier aggregation (CA) concepts included in LTE-advanced protocol, the complexity of the RRM and scheduling of data increases. In this paper, basic LTE-A concepts and a study of different methods of component carrier allocation is studied and performance evaluation is carried out. From the simulation results, it can be inferred that static methods of component carrier allocation is simple but it could not be able to satisfy various important scheduler metric to provide a better QoS to UE. The random method though for some cases it seen better but it is not reliable as the outputs are also random. The dynamic methods of component carrier allocation have been able to provide better scheduler performance metric compared to static and random methods. More over different dynamic approaches can be also combined to improve the overall system efficiency.

Localization in 3GPP LTE Based on One RTT and One TDOA Observation

We study the fundamental problem of fusing one round trip time (RTT) observation associated with a serving base station with one time-difference of arrival (TDOA) observation associated to the serving base station and a neighbor base station to localize a 2-D mobile station (MS). This situation can arise in 3GPP Long Term Evolution (LTE) when the number of reported cells of the mobile station is reduced to a minimum in order to minimize the signaling costs and to support a large number of devices. The studied problem corresponds geometrically to computing the intersection of a circle with a hyperbola, both with measurement uncertainty, which generally has two equally likely solutions. We derive an analytical representation of these two solutions that fits a filter bank framework that can keep track of different hypothesis until potential ambiguities have been resolved. Further, a performance bound for the filter bank is derived. The proposed filter bank is first evaluated in a simulated scenario, where the set of serving and neighbor base stations is changing in a challenging way. The filter bank is then evaluated on real data from a field test, where the result shows a precision better than 40 m 95% of the time.

Arbitrarily Parallel Turbo Decoding for Ultra-Reliable Low Latency Communication in 3GPP LTE

In order to meet the latency requirements of the ultra-reliable low latency communication (URLLC) mode of the third-generation partnership project’s long term evolution (LTE) mobile communication standard, this paper proposes a novel turbo decoding algorithm that supports an arbitrarily high degree of parallel processing, facilitating significantly higher processing throughputs and substantially lower processing latencies than the state-of-the-art (SOTA) LTE turbo decoder. As in conventional turbo decoding algorithms, the proposed Arbitrarily Parallel Turbo Decoder (APTD) decomposes each frame of information bits into a sequence of windows, where the bits within different windows are processed simultaneously using forward and backward recursions in a serial manner. However, in contrast to conventional turbo decoding algorithms, the APTD does not require different windows to be composed of an identical number of bits, which allows the use of an arbitrary number of windows and hence an arbitrary degree of parallelism, when decoding information bits of an arbitrary frame length. Furthermore, conventional turbo decoding algorithms alternate between simultaneously processing the windows in the upper decoder and those in the lower decoder. By contrast, the APTD processes the odd-indexed windows in the upper decoder at the same time as the even-indexed windows in the lower decoder and alternates between this and the reversed arrangement, hence further improving the decoding throughput and latency. Furthermore, the APTD achieves a reduced hardware resource requirement by calculating the extrinsic information based only on the outputs of the forward recursions, rather than based on both the forward and backward recursions of conventional turbo decoding algorithms. We demonstrate that the proposed APTD achieves superior latency, throughput, and computational efficiency than the SOTA LTE turbo decoder at all frame lengths, but particularly at the short frame lengths that are typically used in URLLC approaches. For example, at a frame length of $N={504}$ bits, the proposed APTD achieves an FER of 10−5 at the same $E_{b}/N_{0}$ as $I=8$ iterations of a conventional turbo decoder but with a computational efficiency that is 6 times higher than that of the SOTA turbo decoder, while achieving a latency and throughput that are 0.7 and 1.4 times those of the SOTA decoder, respectively.

Performance and ASIC Designs of the K-best LSD and LMMSE Detectors for LTE Downlink

We consider performance comparison and application specific integrated circuit (ASIC) designs of linear minimum mean-square error (LMMSE) and K-best list sphere detector (LSD) algorithms for 4 × 4 and 8 × 8 multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Requirements for higher data rate and lower power consumption set new challenges for implementation. In order to minimize the power consumption, an optimal detector would be able to switch the detection algorithm to suit the channel conditions. The detectors are designed for three different modulation schemes using 28 nm complementary metal oxide semiconductor (CMOS) technology. The communications performance is evaluated in the Third Generation Partnership Project (3GPP) Long-Term Evolution (LTE) system. The impact of transmit precoding is considered. The ASIC designs aim at providing the hardware design aspects to the comparison of detectors. The designs are synthesized and complexity and power consumption results are found. Based on the ASIC synthesis and communications performance results, we show the performance–energy efficiency and performance–complexity comparison. We also present the most suitable scenarios for a low-power detector and show how the transmit precoding impacts the detector selection.

Adaptive Self-Deferral for Carrier Aggregation of LTE-LAA With RF Power Leakage in Unlicensed Spectrum

The licensed assisted access (LAA) is the new feature of 3GPP long-term evolution (LTE) that uses unlicensed spectrum as an additional bandwidth to meet ever-increasing mobile traffic demands. For fair coexistence with other incumbent systems such as Wi-Fi, LAA specifies the listen-before-talk (LBT) mechanism for channel access. LBT of LAA is also designed to support multi-carrier operation, which is the key to capacity increase, but inherent RF power leakage to adjacent carriers ruins the multi-carrier LBT and deteriorates aggregation capacity considerably. Self-deferral is a solution to solve this problem by aligning carriers' transmission times via transmission deferring of each carrier after backoff, for which the key to success is to find how long self-deferral must be. In this paper, we propose an algorithm to adjust a self-deferral period of the multi-carrier LBT adaptively to carrier loads for enhanced carrier aggregation capacity under RF power leakage. We formulate the target problem as an optimization problem whose objective is to maximize the expected number of aggregated carriers derived as a function of the self-deferral period and carrier loads. Then, we derive the optimum of the aggregation capacity maximization problem for the case of homogeneous interference patterns between carriers in a closed form. Due to the computational complexity of finding the global optimum for the general case of realistic heterogeneous interference patterns between carriers, we develop a suboptimal algorithm to configure the self-deferral period. Through extensive simulation, we demonstrate that the proper configuration of the self-deferral period is of importance and the proposed algorithm outperforms various LBT options in a wide range of network configuration by up to 72% in a single-spot scenario and 47% in 3GPP's indoor deployment scenario, while meeting fair coexistence with the Wi-Fi systems.

Fair-QoS Broker Algorithm for Overload-State Downlink Resource Scheduling in LTE Networks

Efficiently scheduling various service classes while fulfilling performance targets is one of the main challenges in 3GPP Long-Term Evolution (LTE) communication systems. However, Quality of Service (QoS) and fairness provisioning for all different service classes are generally unstable due to insufficient radio resources, especially in heavily loaded states of the network, which leads to the deterioration of overall system performance. In this paper, we address these challenging issues by proposing a two-level downlink scheduling algorithm to deliver all traffic types while attempting to provide a compromise for the LTE performance targets. For the higher level of the algorithm, a coherent resource distribution approach is developed by applying a game theory model in a nested manner to provide per-class fairness. At the lower level, the greedy-knapsack algorithm is properly tailored to optimally allocate resources to the best potential bearers for QoS and throughput enhancement. The performance of the proposed algorithm was evaluated for normal and overload states of the network. The simulation results clearly demonstrate that the proposed scheduling algorithm, compared with the reference scheduling algorithms, provides the best tradeoff for fairness, throughput, and QoS performance in terms of packet loss rate and packet latency for different service classes.

Reduced-Power Almost Black Subframe Based Pulse Radar Spectrum Sharing for LTE System

Cochannel pulse radar and long term evolution (LTE) deployments are considered by the FCC citizen broadband radio service (CBRS) and also 5G spectrum sharing. This paper proposes a radar spectrum sharing method based on LTE reduced-power almost blank subframe (RP-ABS) mechanism, which is used to mitigate interference to pulse radar while maintaining high LTE throughput. For LTE, payload bits are first packed into nonradar interfered time domain subframes (SFs), and then RP-ABS or even zero-power almost blank subframe (ABS) are adopted in the rest SFs. For pulse radar, target detection performance is guaranteed, thanks to the decreased interference caused by LTE RP-ABS power. We also formulate and solve an optimization problem for radar and RP-ABS-based LTE spectrum sharing, which consider tradeoffs between RP-ABS-based LTE performance (bit error rate and throughput) and radar detection probability concurrently. Using 3rd generation partnership project (3GPP) LTE sensitivity test as a benchmark, 28.83% throughput gain can be obtained for RP-ABS-based method. A hardware-in-the-loop testbed is also designed to prove spectrum sharing between RP-ABS-based LTE and radar viable.

Secure LTE-Based V2X Service

Internet of Things (IoT) is the reality of a new and powerful ubiquitous technology. One of its main driving forces is the 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE), seeking to encompass all the applications of IoT. With this trend, 3GPP has finally made the Release 14 for LTE-based vehicle to everything (V2X) service. In this proposed paper, we evaluated the new LTE-based V2X architecture in regards to V2X message delivery and security requirements. We showed that a proper resource allocation and reference point (channel) selection could accommodate all types of V2X message deliveries. However, focusing more on security, we deemed that LTE-based V2X security falls short of meeting adequate security requirements, especially, to well preserve the privacy. Hence, we proposed a privacy preserving security for LTE-based V2X service. Considering the privacy as the top security requirement, we seamlessly integrate our security scheme with the specified LTE security architecture. Our scheme is scalable while fulfilling basic wireless message security requirements. We also provide the security and performance analysis to show the robustness and effectiveness of our proposed schemes.

Tunable Frequency-Division Duplex RF Front End Using Electrical Balance and Active Cancellation

This paper presents a novel, tunable, frequency-division duplexing radio frequency (RF) front end that combines passive and active self-interference (SI) cancellation. An electrical-balance duplexer is used to passively cancel transmitter noise in the receive band, and an active canceller is employed to suppress SI in the transmit (Tx)-band. Subsystem specifications are developed, and a system-level analysis of noise and SI powers in this novel architecture is provided, thereby illustrating its operation. A proof-of-concept demonstrator, built from a software-defined radio and discrete RF components, has been characterized across a range of duplex configurations in the 700–950-MHz range and also at 1900 (Long-Term Evolution (LTE) band 3) and 2600 MHz (LTE band 7). The prototype achieves an impressive 6.0–7.4-dB noise figure in the presence of a +27-dBm LTE uplink Tx blocker for duplex separations of 47.5 MHz and above. The duplexer has also been tested against reference sensitivity test cases defined in the 3GPP LTE specification, demonstrating specification compliant sensitivity in LTE bands 28 (700 MHz), 3, and 7.

ROOMMATEs: An Unsupervised Indoor Peer Discovery Approach for LTE D2D Communications

Recently, there has been an increasing interest in offloading the 3GPP LTE data by using device-to-device (D2D) communications between devices. However, the peer discovering is challenging, especially in the indoor environment, since traditional users use a cellular signal to find peers, leading to incurring interference to other cellular users. In this paper, we propose ROOMMATEs, a novel approach for indoor peer discovery process, which is the enabler for indoor D2D communications in long term evolution (LTE) networks. It is a centralized approach utilizing, but not limited to, the ubiquitous WiFi network/femtocell network, combining with eNodeB in order to deliver the best results. ROOMMATEs is an unsupervised, yet energy efficient algorithm that can find surrounding user equipments (UEs) while minimizing interference and consuming much less energy. Based on the results, ROOMMATEs proves to be highly energy efficient, saving on average 24% per UE and improving signal-to-interference-plus-noise ratio in order of tens of decibels compared to other approaches. Moreover, ROOMMATEs provides indoor place identification for UEs with high accuracy using a small number of observations. ROOMMATEs is robust to missing and noisy data, works with various UEs’ brands/models, and requires no user interactions.

A Comparative Study of PMI/RI Selection Schemes for LTE/LTEA Systems

This paper presents a joint calculation of the precoding matrix indicator (PMI) and rank indicator (RI) in multiple-input multiple-output (MIMO) downlink third generation partnership project (3GPP) universal mobile telecommunications system (UMTS)/long-term evolution (LTE) systems. The standard codebook based precoding is used where the mobile station estimates and sends some measures related to the channel state information to the base station for link adaptation purpose. We study the system performance using link-level simulation under realistic assumptions. Specifically, we use K-best MIMO decoding in the presence of perfect and imperfect estimation of the channel and the noise variance, as well as white and colored noise plus interference defined by the 3GPP LTE specification documents. Similar to some previous results, our method for calculating the PMI/RI is based on maximizing the mutual information between the transmitted and received symbols with respect to the precoding matrix. We evaluate the system performance using two channel measures when computing the mutual information. The first measure is the estimated channel whereas the second one is the estimated channel covariance matrix. Although these two measures have been used in different literature, there have not been conclusive results on which one should be used in different practical scenarios. We assess the system performance using Monte Carlo simulations and compare different test cases, e.g., 3GPP channel models, wideband, and subband PMI/RI calculation, white/color noise plus interference, etc. We then conclude our work with technical recommendations for different scenarios.

Robust predictive filtering schemes for sub‐band CQI feedback compression in 3GPP LTE systems

The third generation partnership project (3GPP) long-term evolution (LTE) cellular system offers high data rate capabilities by leveraging several techniques including link adaptation and frequency selective scheduling. These techniques rely on accurate channel quality indicator (CQI) feedback reports that are sent by the user equipment (UE) to the evolved node B, a process which results in high signalling overhead. In this study, the authors propose a UE-assisted sub-band feedback compression scheme based on a predictive filtering technique to reduce this signalling overhead. Four schemes based on adaptive filters have been designed, implemented and tested in an LTE system level simulator. Simulation results indicate that the proposed compression scheme has shown efficacy with an overall CQI feedback signalling reduction of up to 92.5% whilst maintaining stable sector throughput, when compared with the standard 3GPP CQI feedback mechanism. Although the proposed scheme exhibits low computational and memory complexity, a reduced-complexity scheme achieving an average computational load reduction of up to 35% is also presented.

Unsupervised Long- Term Evolution Device-to-Device: A Case Study for Safety-Critical V2X Communications

In this article, we explore the recent Third Generation Partnership Project (3GPP) long-term evolution (LTE) device-to-device (D2D) radio resource management specification (Release 14) to identify the challenges and evaluate the potential of unsupervised LTE D2D (mode 2) for safety-critical vehicle-to-everything (V2X) communications. We also propose two distributed resource allocation strategies for unlicensed band access. Complementary to dedicated short-range communication (DSRC)/intelligent transport system (ITS)-G5, unsupervised LTE D2D presents an opportunity to provide redundancy for ultrareliable systems, such as safety-critical V2X communications.

Three-Dimensional Positioning for LTE Systems

In the Third-Generation Partnership Project (3GPP) Long-Term Evolution (LTE) specifications, several 2-D positioning methods have been proposed to support location-based services (LBSs). It has been shown that the observed time difference of arrival (OTDOA) method provides the best result. With the advent of the fifth-generation cellular systems, 3-D beamforming will be introduced, and 2-D positioning may not be sufficient for future applications. Although the conventional OTDOA method can be used in 3-D positioning, it requires more base stations (BSs) in cooperation and often performs poorly in typical cellular network geometry. In this paper, we propose a novel OTDOA-based method to solve the problems. First, we exploit the sparsity of the wireless channel and propose to use a compressive-sampling-based channel estimation method, which greatly enhances the precision of time-of-arrival (TOA) estimation. Then, we propose a transmit beamforming scheme such that the elevation angle of departure (AOD) can be accurately estimated. Finally, we combine the estimated TOAs and the AOD in the OTDOA scheme to conduct 3-D positioning. With the proposed scheme, the number of BSs required for 3-D positioning remains the same as that of 2-D, and the positioning accuracy greatly outperforms that of the conventional OTDOA method. Simulations show that 90% of the position error can be less than 7 m.

Analytical Model and Performance Evaluation of Long-Term Evolution for Vehicle Safety Services

In a traffic jam or dense vehicle environment, vehicular ad hoc networks (VANETs) cannot meet the safety requirement due to serious packet collisions. The traditional cellular network solves packet collisions but suffers from long end-to-end delay. Third-Generation Partnership Project (3GPP) Long-Term Evolution (LTE) overcomes both drawbacks; thus, it may be used, instead of VANETs, in some extreme environments. We use Markov models with dynamic scheduling and semipersistent scheduling (SPS) to evaluate how many idle resources of LTE can be provided for safety services and how safety applications impact LTE traditional users. Based on the analysis, we propose to reserve the idle radio resources in LTE for vehicular safety services (LTE-V). Additionally, we propose the weighted-fair-queuing (WFQ) algorithm to schedule beacons for safety services using the LTE reserved resources. Numerical results verify that the proposed mechanism can significantly improve the reliability of safety applications by borrowing limited LTE bandwidth. We also build an NS3 simulation platform to verify the effectiveness of the proposed Markov models. Finally, the reliability of applications, including cooperation collision warning (CCW), slow vehicle indication (SVI), and rear-end collision warning (RCW), using dedicated short-range communication (DSRC) with LTE-V, are evaluated. The simulation results demonstrate that the stringent quality-of-service (QoS) requirement of the aforementioned three applications can be satisfied, even under heavy traffic.

Enhanced Signal Detection in 3GPP LTE System with Successive Interference Cancellation

In this paper we introduced interference cancellation (IC) in the cell search and the detection of physical downlink shared channel (PDSCH) in long term evolution (LTE) of 3rd generation partnership project (3GPP). After user equipment (UE) is turned on, it has to first search the target cell using synchronization channel (SCH). After UE gets timing and cell identification (Cell ID) by cell search process, it can start to transmit and receive data through the traffic channel. In most cases, UE experiences the interference from surrounding neighbor cells, which may result in the degradation of the receiver performance. Not only in time division duplex (TDD) but also frequency division duplex network (FDD), the cells must be deployed with the time aligned to support better successful handover and also provide multemedia broadcast and multicast service (MBMS) efficiently in the network. In synchronous network system, since every cell sends his SCH using shared resource allocation, it is inevitable that two or more neighboring cells can interfere each other in some situation. The cell specific reference signal (CRS) is used for channel estimation in downlink reception. The CRS from neighbor cells may overlap with the resource of PDSCH of the target cell. Hence, the collision of SCH and CRS from the neighbor cells can degrade both the performance of cell search and PDSCH reception at the same time. In this paper, we analyzed the improved performance of the cell search and PDSCH reception by using successive interference cancellation. Simulation results show that the proposed scheme can effectively reduce the mutual interference and improve the performance of the signal detection in view of the cell search and PDSCH reception, respectively.