Implementation of PDSCH Receiver and CSI-RS for 5G-NR

PDSCH (Physical Downlink Shared Channel) is the data-bearing channel in 5G-NR. In order to decode data, it needs DCI (downlink control Information) from PDCCH (Physical Downlink Control Channel). PDSCH uses LDPC(Low-Density Parity Check) code for encoding the data which is an errorcorrecting code. One of the main blocks of PDSCH is Rate Matching and scrambling followed by modulation. NR supports modulation up-to 256 QAM (Quadrature Amplitude Multiplexing). AWGN and TDLC channel Model (delay spread) as defined in 3GPP specifications are used for the simulation purpose. The Channel estimator used for PDSCH is Least square followed by tone-averaging and linear interpolation in time. The block error rate performance highly depends on the channel quality between the base station and the receiver. For acquiring the channel quality, NR specifies a special type of cell-specific reference signal which can be configured for transmission on up-to 32 antenna ports. The CSI-RS resources are code, frequency and time division multiplexed. After passing through the channel the CSI receiver estimates the channel, and finds the suitable rank, the precoding matrix to be used and the MCS and feeds it back to the transmitter which is free to use the recommendation give by UE or follow its own. In either case, it signals the parameters used in the base station back to UE

3GPP LTE Release 9 and 10 requirement analysis to physical layer UE testing

The purpose of this thesis was to analyze the testing requirements to physical layer features which are used in LTE Release 9 and 10 timeframe. The aim of the analysis was to define test case requirements for new features from the physical layer point of view. This analysis can then be utilized to implement and design test cases using commercial eNB simulators. The analysis was carried out by studying the 3GPP specifications and by investigating the integration and system level testing requirements. Different feature specific parameters were evaluated and different testing aspects were studied in order to verify the functionalities and performance of the UE. Also, different conformance test case scenarios and field testing aspects were investigated in order to improve the test case planning in the integration and system testing phase. The analysis showed that in Rel-9 there are two main features which have a great impact on the Rel-9 physical layer testing. These two features are the dual-layer beamforming and UE positioning which is done with OTDOA and E-CID methods. It was analyzed that the requirements for the downlink dual-layer beamforming focus on TDD side and the test plan must contain especially throughput performance testing in integration and system phase testing. OTDOA and E-CID methods, on the other hand, need test plans which are concentrating on the positioning accuracy. In Rel-10, the analysis showed that there are plenty of new features on physical layer to ensure the transition from LTE to LTE-Advanced. The main requirements were assigned for the CA feature which has testing activities especially on the UE feedback operations. Also, different kinds of CA deployment scenarios were analyzed to evaluate more closely the initial CA testing scenarios in integration and system testing. Analysis continued with downlink multi-layer beamforming where the requirements were seen to concentrate on new CSI-RS aspects and to throughput performance testing. Uplink MIMO aspects were analyzed at the end and the studies showed that this feature may have a minor role in Rel-10 timeframe and therefore it does not have any important testing requirements which should be taken into account in test plans

Performance Analyses of Different MIMO Modes In LTE Release 8 Networks

The multi-antenna techniques are the one of the key features in 3GPP LTE specifications. Thus, the understanding of different transmission modes behaviour, available in LTE, is very important for high quality and cost efficient LTE network deployment. Besides, the lack of available practical studies of this topic makes the problem even more attractive. This master thesis work is focused on measurement based performance analyses of different special multiplexing (SM) modes available in LTE Release 8 networks using the same LTE base stations as used in this study. Field measurements have been carried out in different propagation environments. In analyses, user application throughput and MIMO utilization have been studied to demonstrate the efficiency of each mode. The measurement results are different than the theoretical and simulation based studies. The results clearly show that the open-loop-dynamic SM is the best choice, independent of the environment, for SNR > -2 to -5 dB and can provide up to 3 Mbps or 11.7% advantage over closed loop SM. The open loop static SM is as good as open loop dynamic SM only for very good, SNR > 10 to 15 dB, channel conditions. And, for the bad channel conditions, SNR 15 dB, which means, that there is a significant interference between parallel data streams. The bad performance of the closed loop is associated with low CQI reports for codeword 1 as the UE reduces the SNR for codeword 1 to mitigate the interference between parallel data streams. The results can be generalized only for the studied equipment hardware, software and parameters as the other vendors can have slightly different implementation of some parts of LTE. But any way, the results show that knowledge of the different SM modes behaviour can help to increase the quality of the network

Fundamental Limits in Correlated Fading MIMO Broadcast Channels: Benefits of Transmit Correlation Diversity

We investigate asymptotic capacity limits of the Gaussian MIMO broadcast channel (BC) with spatially correlated fading to understand when and how much transmit correlation helps the capacity. By imposing a structure on channel covariances (equivalently, transmit correlations at the transmitter side) of users, also referred to as \emph{transmit correlation diversity}, the impact of transmit correlation on the power gain of MIMO BCs is characterized in several regimes of system parameters, with a particular interest in the large-scale array (or massive MIMO) regime. Taking the cost for downlink training into account, we provide asymptotic capacity bounds of multiuser MIMO downlink systems to see how transmit correlation diversity affects the system multiplexing gain. We make use of the notion of joint spatial division and multiplexing (JSDM) to derive the capacity bounds. It is advocated in this paper that transmit correlation diversity may be of use to significantly increase multiplexing gain as well as power gain in multiuser MIMO systems. In particular, the new type of diversity in wireless communications is shown to improve the system multiplexing gain up to by a factor of the number of degrees of such diversity. Finally, performance limits of conventional large-scale MIMO systems not exploiting transmit correlation are also characterized.Comment: 29 pages, 8 figure

Resource Allocation in Multi-user MIMO Networks: Interference Management and Cooperative Communications

Nowadays, wireless communications are becoming so tightly integrated in our daily lives, especially with the global spread of laptops, tablets and smartphones. This has paved the way to dramatically increasing wireless network dimensions in terms of subscribers and amount of flowing data. Therefore, the two important fundamental requirements for the future 5G wireless networks are abilities to support high data traffic and exceedingly low latency. A likely candidate to fulfill these requirements is multicell multi-user multi-input multiple-output (MU-MIMO); also termed as coordinated multi-point (CoMP) transmission and reception. To achieve the highest possible performance in MU-MIMO networks, a properly designed resource allocation algorithm is needed. Moreover, with the rapidly growing data traffic, interference has become a major limitation in wireless networks. Interference alignment (IA) has been shown to significantly manage the interference and improve the network performance. However, how practically use IA to mitigate interference in a downlink MU-MIMO network still remains an open problem. In this dissertation, we improve the performance of MU-MIMO networks in terms of spectral efficiency, by designing and developing new beamforming algorithms that can efficiently mitigate the interference and allocate the resources. Then we mathematically analyze the performance improvement of MUMIMO networks employing proposed techniques. Fundamental relationships between network parameters and the network performance is revealed, which provide guidance on the wireless networks design. Finally, system level simulations are conducted to investigate the performance of the proposed strategies

Analysis of hybrid schedulers for CoMP resource allocation in LTE-Advanced SU-MIMO systems

Coordinated Multi Point transmission and reception (CoMP) has been considered as a promising technique to enhance system throughput performance by reducing inter-cell interference (ICI) in cell edge area. Past studies showed that Joint Processing (JP) transmission mode is capable to provide much better throughput performance benefits than Coordinated Scheduling/Beamforming (CS/CB) both in homogeneous and heterogeneous networks; however, the robust strategy of resource block (RB) allocation and scheduling algorithms has to be specifically designed for CoMP-JP in a MIMO-OFDMA system. In this paper, an intuitive algorithm will be investigated in order to reach the highest overall system throughput but keep same level of fairness performance at same time. We first analyze the threshold of reference signal strength to determine the operating region for CoMP-JP user selection, and then calculate the robust ratio of RB allocation for CoMP and non-CoMP users. In final stage, the hybrid schedulers adopted specifically for the unique characteristics of CoMP and non-CoMP users will be analyzed and compared. Our results show that the threshold of reference signal strength $(\lambda, \theta)$ should both be set at -1dB for CoMP operating region, and the parameter to the ratio of CoMP users should be set at $\gamma = 0.9$ for robust RB allocation

D3.2 First performance results for multi -node/multi -antenna transmission technologies

This deliverable describes the current results of the multi-node/multi-antenna technologies investigated within METIS and analyses the interactions within and outside Work Package 3. Furthermore, it identifies the most promising technologies based on the current state of obtained results. This document provides a brief overview of the results in its first part. The second part, namely the Appendix, further details the results, describes the simulation alignment efforts conducted in the Work Package and the interaction of the Test Cases. The results described here show that the investigations conducted in Work Package 3 are maturing resulting in valuable innovative solutions for future 5G systems.Fantini. R.; Santos, A.; De Carvalho, E.; Rajatheva, N.; Popovski, P.; Baracca, P.; Aziz, D.... (2014). D3.2 First performance results for multi -node/multi -antenna transmission technologies. http://hdl.handle.net/10251/7675

LTE Indoor MIMO Performance and Antenna Configuration

Long-term evolution (LTE) and multiple input multiple output (MIMO) have earned reputations to be a cutting‒edge technology, which can boost significantly wireless communication performances. However, many aspects influence on LTE MIMO efficiency; those include propagation environments and antenna configurations. The goal of the thesis is to study performances of LTE MIMO on downlink in indoor. MIMO gains over transmit diversity and single antenna are the objective. Additionally, the study compares MIMO indoor performances with different antenna configurations at LTE base station and UE, including space diversity and polarization diversity. Some results obtained in this thesis follow the expectations what have been studied in literature and previous practical studies but some differences are also pointed out. Medium access control throughput (MAC TP) and some system parameters in LTE network that are linked with TP are analysed; those parameters are CQI, MCS as well as MIMO utilization. Effects of indoor propagation, such as LoS, NLoS, good and bad signal levels on SNR strength and MIMO utilization are clarified. In overall, MIMO outperforms transmit diversity (TxDiv) and single antenna in LTE indoor. The overall MIMO MAC TP gains are about nearly 40.0% over TxDiv and more than 20.0% over single stream. LoS environment boost SNR strength. Hence, up to 35.0% TP gain over single antenna is achieved. However, LoS signals make the channel become correlated due to lack of multipaths, causing that MIMO is not fully utilized. The gain of MIMO over single antenna is reduced at no LoS environments, particularly only around 17.0% and 21.0% MAC TP gains are recorded at NLoS channels with good signal levels and weak signal strength, relatively. The overall TP gain the UE experiences by using TxDiv over single antenna is roughly more than 20.0%, but LoS environment limits TxDiv performance. Hence, at LoS channel, TxDiv performance is reduced by around 2.0% compared to single stream. The worse the channel, the better TxDiv performs. The highest gain is at cell edge environment when TxDiv improves throughput more than 40.0% over single antenna. Clearly, antenna configuration impacts network performance. Large horizontal separation (7λ) between antenna elements outperforms small separation (0.5λ) in terms of SNR, MIMO utilization and MAC TP. The MAC TPs of large separation by using omni-directional and directional antennas are almost similar, around 27.0 Mbps. Space diversity with omni-directional antennas provides roughly 14.0% MAC TP improvement while only approximately 4.5% TP gain can be achieved with directional antennas. Vertical‒horizontal polarization pair deployed at LTE base station is found to provide better performance over vertical‒vertical polarization and X‒pol pairs. Signals also appear to be more correlated with vertical-horizontal polarization pair since MIMO utilization gets better values, MIMO utilization gains are around 18.0% over vertical-vertical polarization pair and 6.0% over X-pol pair, resulting in around 31.7% and 17.0% MAC TP gains over the two latter, relatively. The results also point out that changing polarizations at UE do not give clear MAC TP and MIMO utilization improvements. From the radio network planning point of view, the results obtained in this thesis can be considered as guidelines for indoor network planning and optimization for network operators. It is important to conclude that based on the measurements made in this thesis, space diversity (7λ) with omni-directional antennas and vertical-horizontal polarization pairs appear to give optimal indoor performance. However, it should be taken into consideration that all results presented in this thesis are highly dependable on the chosen antennas, LTE network systems, devices and indoor environment where the measurements are carried out. Hence, the results may vary with the factors mentioned

Coordinated Multipoint Communications In Heterogeneous Networks

As users' demands on cellular service escalate rapidly, operators are required to deploy technologies with wider and more sophisticated techniques. In order to meet the future service needs, the standardization body 3rd Generation Partnership Project (3GPP) has standardized Long Term Evolution (LTE) and it has been working on enhancement of LTE and LTE-Advanced. The two key enabling technologies of LTE-Advanced are Heterogeneous Networks (HetNets) and Coordinated Multipoint (CoMP) communications. The former is aimed to improve inconsistent user experience and its basic feature is standardized in 3GPP release 11. The latter one where small cells are deployed within macro-cellular networks has been considered to enhance coverage and capacity. This thesis presents a concise literature survey of cooperative communications and CoMP technologies. Furthermore, a detailed Matlab-based simulation study on CoMP between macro and small cells in HetNets is presented. Comparative analyses and evaluations are also made for different CoMP schemes under different deployed scenarios. At the same time, a new CoMP UE selection criterion is proposed to fit the modified round robin scheduling deployed in simulation and optimize the resource allocation among CoMP and non-CoMP UEs