Lars Lindbom

Bio: Lars Lindbom is an academic researcher from Ericsson. The author has contributed to research in topics: Transmission (telecommunications) & User equipment. The author has an hindex of 20, co-authored 68 publications receiving 1744 citations.

Network architecture, methods, and devices for a wireless communications network

Abstract: Methods and apparatus in a fifth-generation wireless communications, including an example method, in a wireless device, that includes receiving a downlink signal comprising an uplink access configuration index, using the uplink access configuration index to identify an uplink access configuration from among a predetermined plurality of uplink access configurations, and transmitting to the wireless communications network according to the identified uplink access configuration. The example method further includes, in the same wireless device, receiving, in a first subframe, a first Orthogonal Frequency-Division Multiplexing (OFDM) transmission formatted according to a first numerology and receiving, in a second subframe, a second OFDM transmission formatted according to a second numerology, the second numerology differing from the first numerology. Variants of this method, corresponding apparatuses, and corresponding network-side methods and apparatuses are also disclosed.

Enhanced Inter-cell Interference Coordination for Heterogeneous Networks in LTE-Advanced: A Survey

Abstract: Heterogeneous networks (het-nets) - comprising of conventional macrocell base stations overlaid with femtocells, picocells and wireless relays - offer cellular operators burgeoning traffic demands through cell-splitting gains obtained by bringing users closer to their access points. However, the often random and unplanned location of these access points can cause severe near-far problems, typically solved by coordinating base-station transmissions to minimize interference. Towards this direction, the 3rd generation partnership project Long Term Evolution-Advanced (3GPP-LTE or Rel-10) standard introduces time-domain inter-cell interference coordination (ICIC) for facilitating a seamless deployment of a het-net overlay. This article surveys the key features encompassing the physical layer, network layer and back-hauling aspects of time-domain ICIC in Rel-10.

Reference signal interference management in heterogeneous network deployments

Abstract: Methods and apparatus for enabling interference coordination in a communication network. A base station includes a plurality of antenna ports. Each antenna port is configured to transmit a reference signal, and each antenna port is associated with a respective cell. The base station determines a set of cells where transmissions of reference signals is to be performed from a reduced set of the plurality of antenna ports. The base station determines a subset of antenna ports in at least one cell of the determined set of cells to enable interference coordination in the network, and transmits the reference signal from the subset of antenna ports.

Tracking of time-varying mobile radio channels .1. The Wiener LMS algorithm

Abstract: Adaptation algorithms with constant gains are designed for tracking smoothly time-varying parameters of linear regression models, in particular channel models occurring in mobile radio communications. In a companion paper, an application to channel tracking in the IS-136 TDMA system is discussed. The proposed algorithms are based on two key concepts. First, the design is transformed into a Wiener filtering problem. Second, the parameters are modeled as correlated ARIMA processes with known dynamics. This leads to a new framework for systematic and optimal design of simple adaptation laws based on prior information. The algorithms can be realized as Wiener filters, called learning filters, or as "LMS/Newton" updates complemented by filters that provide predictions or smoothing estimates. The simplest algorithm, named the Wiener LMS, is presented. All parameters are here assumed governed by the same dynamics and the covariance matrix of the regressors is assumed known. The computational complexity is of the same order of magnitude as that of LMS for regressors which are either white or have autoregressive statistics. The tracking performance is, however, substantially improved.

Tracking of time-varying mobile radio channels. II. A case study

Abstract: For pt.I see ibid., vol.49, p.2207-17 (2001). Low-complexity Wiener LMS (WLMS) adaptation algorithms, of use for channel estimation, have been derived in Lindbom et al. (2001). They are here evaluated on the fast fading radio channels encountered in IS-136 TDMA systems, with the aim of clarifying several issues: How much can channel estimation performance be improved with these tools, as compared to LMS adaptation? When can an improved tracking MSE be expected to result in a meaningful reduction of the bit error rate? Will optimal prediction of future channel estimates significantly improve the equalization? Can one single tracker with fixed gain be used for all encountered Doppler frequencies and SNRs, or must a more elaborate scheme be adopted? These questions are here investigated both analytically and by simulation. An exact analytical expression for the tracking MSE on two-tap FIR channels is presented and utilized. With this tool, the MSE performance and robustness of WLMS algorithms based on different statistical models can be investigated. A simulation study then compares the uncoded bit error rate of detectors, where channel trackers are used in decision directed mode in conjunction with Viterbi algorithms. A Viterbi detector combined with WLMS, based on second order autoregressive fading models possibly combined with integration, provides good performance and robustness at a reasonable complexity.

Method and apparatus for enhancing coverage of machine type communication (mtc) devices

Abstract: A method and apparatus are described for a low cost machine-type-communication (LC-MTC) wireless transmit/receive unit (WTRU) to enhance coverage. An example method for physical broadcast channel (PBCH) enhancement includes receiving system information on an enhanced PBCH (ePBCH). The ePBCH is located in a set of radio frames which is a subset of available radio frames, where the subset includes fewer than all the available radio frames. The ePBCH is received in at least one radio frame of the set of radio frames. An example method for physical random access channel (PRACH) enhancement includes receiving configuration of legacy PRACH resources and enhanced PRACH (ePRACH) resources. The WTRU selects one of legacy PRACH resources or ePRACH resources based on a coverage capability. Another example method for PRACH enhancement includes receiving configuration of ePRACH resources. The ePRACH resources include multiple ePRACH resource types, each ePRACH resource type being associated with a coverage capability.

Algorithms for Enhanced Inter Cell Interference Coordination (eICIC) in LTE HetNets

Abstract: The success of LTE Heterogeneous Networks (HetNets) with macro cells and pico cells critically depends on efficient spectrum sharing between high-power macros and low-power picos. Two important challenges in this context are, {(i)} determining the amount of radio resources that macro cells should {\em offer} to pico cells, and {(ii)} determining the association rules that decide which UEs should associate with picos. In this paper, we develop a novel algorithm to solve these two coupled problems in a joint manner. Our algorithm has provable guarantee, and furthermore, it accounts for network topology, traffic load, and macro-pico interference map. Our solution is standard compliant and can be implemented using the notion of Almost Blank Subframes (ABS) and Cell Selection Bias (CSB) proposed by LTE standards. We also show extensive evaluations using RF plan from a real network and discuss SON based eICIC implementation.

Radio base station, user terminal, and radio communication method

Abstract: The present invention is designed to improve spectral efficiency in a radio communication system which can use non-orthogonal multiple access (NOMA). Steps are provided in which a radio base station configures one of a plurality of transmission mode including a first transmission mode, which groups a plurality of transmission methods including a transmission method to employ non-orthogonal multiple access (NOMA) and multiple-user multiple-input and multiple-output (MU-MIMO), and a second transmission mode, which groups a plurality of transmission methods including a transmission method to employ this NOMA and open-loop transmit diversity, and transmits a downlink signal for this user terminal based on the configured transmission mode.

Algorithms for Enhanced Inter-Cell Interference Coordination (eICIC) in LTE HetNets

Abstract: The success of LTE heterogeneous networks (HetNets) with macrocells and picocells critically depends on efficient spectrum sharing between high-power macros and low-power picos. Two important challenges in this context are: 1) determining the amount of radio resources that macrocells should offer to picocells, and 2) determining the association rules that decide which user equipments (UEs) should associate with picos. In this paper, we develop a novel algorithm to solve these two coupled problems in a joint manner. Our algorithm has provable guarantee, and furthermore, it accounts for network topology, traffic load, and macro-pico interference map. Our solution is standard compliant and can be implemented using the notion of Almost Blank Subframes (ABS) and Cell Selection Bias (CSB) proposed by LTE standards. We also show extensive evaluations using RF plan from a real network and discuss self-optimized networking (SON)-based enhanced inter-cell interference coordination (eICIC) implementation.

User equipments, base stations and methods

Abstract: A user equipment (UE) is described. The UE includes a higher layer processor configured to receive an RRC message for enhanced resource element group (EREG) configuration. The UE also includes a physical downlink control channel receiver configured to monitor an enhanced physical downlink control channel (EPDCCH) on the basis of a first EREG structure if the EREG configuration is not established, and to monitor the EPDCCH on the basis of a second EREG structure if the EREG configuration is established. All resource elements (REs) with number i in a physical resource block (PRB) pair comprise EREG number i.