Jacek Gora

Cell-Specific Uplink Power Control for Heterogeneous Networks in LTE

This paper provides an assessment of 3GPP standardized LTE/LTE-A uplink power control procedures in case of a co-channel operation of different types of base stations. Especially the case of femtocell deployment with an overlaying macrocell is considered. Imperfections of the currently accepted procedures in case of such networks are pointed and a modified solution is proposed. It is shown that in case of heterogeneous networks more cell-specific configuration can lead to 8% and 14% performance improvements in capacity and coverage of local cells respectively, without harm for overlying macrocells. The evaluation of the proposed scheme has been done on case of a macro and femto co-channel deployment, but should be also valid for other cell types.

Deployment aspects of 3G femtocells

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).

In-band and out-band relaying configurations for dual-carrier LTE-advanced system

For multi-hop transmission two basic relaying modes are available: in-band and out-band. The in-band mode is the main solution considered in most state-of-the-art studies and it is the focus of the 3GPP LTE-Advanced specification. This is because the solution requires only one frequency carrier for relay node operation. However, with evolution of cellular systems, multi-carrier operation is commonly considered. This enables implementation of the out-band operation mode in an operator controlled spectrum. In this paper we discuss and compare the two operation modes with consideration of real world factors. Furthermore, we propose several resource allocation schemes, that are evaluated in a dual-carrier system, to assess applicability of the relaying modes. As a result we identify the most promising configurations for advanced relay enhanced networks.

QoS-aware resource management for LTE-Advanced relay-enhanced network

Relaying is one of the major innovative concepts proposed in the recent years for cellular radio communication systems. It is a perfect solution for dealing with the issue of high variability of performance in cellular networks. By coordinated deployment at cell-edge or in shadowed areas, relay nodes can extend network coverage and increase the low end-user performance. Considering the advantages, relaying is recently being included in the standards of the fourth generation systems such as the LTE-Advanced and the WiMAX. However, one major problem of relaying is still to be resolved. Specifically, there are no concrete concepts for quality-of-service provisioning for relayed transmissions. This paper investigates the case of packet delivery times over multi-hop links in relay-enhanced networks. The discussion is specifically based on relaying implementation in the LTE-Advanced system. The quality-of-service satisfaction and its fairness for the base station and relay-node-connected users are analyzed in the framework of the utility theory. For the purpose of this analysis, utility functions are proposed for real-time traffic with minimum data rate and/or maximum packet delivery time requirements. Furthermore, several optimization concepts are proposed for managing multi-hop transmissions in a quality-of-service aware manner. The included analysis based on the LTE-Advanced system level simulations shows that the proposed optimizations have the potential to improve the overall quality-of-service satisfaction in a relay-enhanced system.

Resource management issues for multi-carrier relay-enhanced systems

Relaying is one of the enabling techniques for next generation systems. Factors deciding on performance of relay-enhanced systems are the resource allocation and coordination. The capacity of the wireless relay backhaul link is typically the bottleneck of transmissions conveyed through the relay node. It can be to some extent improved by allocating dedicated resources; however, typically this is done at the expense of the performance of users served directly from the base station. To achieve optimum overall performance, resource assignment to relays and users has to be done carefully. This article addresses the problem of resource allocation with relays operated in multi-carrier scenarios. Guidelines for optimization of the resource allocation under the resource fair policy are given with different relay configurations, including time, frequency, and hybrid resource partitioning schemes. Finally, advanced resource coordination procedures are presented. Multi-carrier interference coordination is proposed for improving the quality of radio links, and carrier load balancing for improving the efficiency of resource utilization.

Pass It on: Advanced Relaying Concepts and Challenges for Networks Beyond 4G

Relay nodes (RNs) will be a key feature of future wireless networks. RNs can extend coverage, increase network capacity, and provide more uniform quality-of-service (QoS) across the cell area in a cost-effective manner. Therefore, not surprisingly, relaying techniques have attracted a significant amount of attention from the wireless industry and standards. The Third-Generation Partnership Project (3GPP) release 10 has considered RNs that act as base stations (BSs), known as type-1 RNs, aiming only for coverage extension. However, RNs can be employed in different ways, and several challenges have to be addressed to attain the theoretical gains. This article presents an overview of the relaying concepts related to the 3GPP long-term evolution (LTE) road map, i.e., concepts related to type-1, type-2, and moving RNs. The implementation challenges are outlined, and a number of promising solutions for each RN type are discussed. More specifically, for type-1 RNs, this article focuses on the allocation of resources to the backhaul and access links. For type-2 RNs, the focus is on designing distributed hybrid automatic repeat request (HARQ) protocols that involve RNs. Moving RNs are presented as an efficient solution to the ever-growing demand for wireless broadband by vehicleborne users. Overall, the presented relaying concepts and solutions can significantly improve the user experience and can play an important role in the future.

Control of dexterous hand - algorithm implementation issues

This paper relates to the research on a dexterous hand prosthesis conducted at the Wroclaw University of Technology. The possibility of aiding the prosthesis control system by utilization of application specific digital circuits is presented. Several exemplary designs, prepared during some of to-date works conducted by authors, have been presented. Discussed solutions are part of a bigger project that is still ongoing and are still being developed.

FFT Based EMG Signals Analysis on FPGAs for Dexterous Hand Prosthesis Control

This paper relates to the research on a dexterous hand prosthesis conducted at the Wroclaw University of Technology. The possibility of recognizing human intention by digital processing of electromyographic (EMG) signals is presented. The realization of the decision-making logic in specialized digital circuits is investigated into. The article specifically deals with the issue of the Fast Fourier Transform (FFT) algorithm floating-point implementation.

Interference mitigation for multi-carrier relay-enhanced networks

Relaying is a technique introduced recently to cellular systems such as LTE-Advanced or mobile WiMAX. It is designed especially for improving performance of users experiencing poor radio conditions towards traditional macro base stations, e.g. users located at cell-edge areas. In this paper, performance of relay nodes operated in a multi-carrier system is investigated. The multi-carrier operation is typically not considered for relay nodes, thus not well studied yet. Procedures for detecting high inter-relay interference and its mitigation by coordinated carrier allocation are proposed here. The conducted analysis shows that by using the proposed procedures capacity of a relay-enhanced network can be increased by 10% compared to a network without interference mitigation solutions implemented.

Design and optimization aspects of wireless backhaul operated in the millimeter wave spectrum

In this article we discuss a case of a cellular network with backhaul operated wirelessly on millimeter waves (mmWaves). We perform extensive studies based on ray-tracing and system-level simulations to assess performance of such deployments. For the purpose of the evaluations we propose a backhaul topology optimization algorithm that allows assessment of the gateway (GW), i.e. nodes with wired backhaul, penetration required to provide a certain performance to the access network. Finally, we formulate recommendations about various aspects of such networks, e.g. inter-site distance or antenna configurations.