Bertram Gunzelmann

Closed loop transmission with precoding selection in LTE/LTE-Advanced system

Closed-loop transmission combined with MIMO (multiple-input multiple-output) and OFDM (orthogonal frequency division multiplexing) technologies have drawn most attentions during development of the 4G systems (fourth generation of mobile communication systems). In LTE (Long Term Evolution) and LTE-Advanced systems, which are proposed by 3GPP (Third Generation Partnership Project) to be the most competitive candidate for the 4G systems, the codebook based precoding scheme is deployed for realizing the closed-loop transmission concept. This scheme introduces the precoding matrix selection at the receiver and precoding operation at the transmitter and achieves a good tradeoff between the system complexity and the performance gain given by the closed-loop transmission. In this manuscript, the authors give a brief overview of the LTE/LTE-Advanced system downlink transmission. Furthermore, different precoding matrix selection criteria are discussed at the aim of optimal receiver design. Following the analytical and numerical results, the authors conclude that the minimum post mean squared error based criterion is the optimal candidate for precoding matrix selection at the receiver in LTE compliant systems.

On the physical layer performance with rank indicator selection in LTE/LTE-Advanced system

The 3GPP (Third Generation Partnership Project) LTE (Long Term Evolution) and LTE-Advanced activities work toward the evolved UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access (E-UTRA), and the solution of IMT-Advanced (International Mobile Telecommunications) and systems beyond. The combination of OFDM (orthogonal frequency division multiplexing) and MIMO (multiple-input multiple-output) has been introduced into LTE and LTE-Advanced systems for achieving high system capacity. Furthermore, the closed-loop concept with codebook based precoding MIMO and transmission layers selection, termed as RI (rank indicator) selection have also been included to provide robust transmission in mobile wireless communication scenarios and increase the cell coverage. This manuscript focuses on the RI selection study and implementation in LTE and LTE-Advanced systems and illustrates the downlink performance evaluation and comparison with different RI selection schemes. According to the analytical and numerical results from an LTE and LTE-Advanced compliant simulator, the mutual information based scheme is chosen as the best candidate for RI selection.

On MIMO with successive interference cancellation applied to UTRA LTE

The long term evolution of UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access, abbreviated as UTRA LTE, makes use of OFDM (orthogonal frequency division multiplexing) combined with MIMO (multiple-input multiple-output), termed MIMO-OFDM. The potential maximization of transmitted data rates has been considered a most beneficial feature of MIMO schemes. This maximization shall be strived for by spatial multiplexing. In particular, high data rates in the downlink have been considered desirable. Also, in view of an efficient implementation, the downlink requires a thorough assessment. Therefore, the authors will discuss the deployment of spatial multiplexing in the UTRA LTE downlink and will show that the performance of successive interference cancellation (SIC) based data detection techniques for MIMO-OFDM is beneficial.

Dynamic transmission mode selection in LTE/LTE-Advanced system

Recently, the LTE (Long Term Evolution) and LTE-Advanced systems, developed by the 3GPP (Third Generation Partnership Project), has been proposed as the candidate for the 4G systems (forth mobile communication systems). The combination of OFDM (orthogonal frequency division multiplexing) and MIMO (multiple-input multiple-output) transmission technologies has been introduced into LTE systems for achieving high system performance required by 4G systems. Furthermore, the closed-loop concept with codebook based precoding MIMO and dynamic transmission mode selection, termed as RI (rank indicator) selection, have also been deployed in LTE systems to provide robust link connection and large cell coverage. In this manuscript, the authors focused on the study of dynamic transmission mode selection and its implementation in LTE systems. Different RI selection schemes were proposed in this manuscript with the corresponding downlink performance evaluation. According to the analytical and numerical results, the authors conclude that the mutual information based scheme is the best candidate for RI selection in LTE/LTE-Advanced compliant systems.

System performance of UTRA LTE and LTE-advanced

The long term evolution of UMTS Terrestrial Radio Access (UTRA LTE) and its enhanced version - LTE-Advanced use OFDM (orthogonal frequency division multiplexing) combined with MIMO (multiple-input multiple-output), termed MIMO-OFDM. The spatial multiplexing (SM) MIMO scheme is deployed in LTE and LTE-Advanced downlink to provide high data rates. In this communication, the authors will discuss a set of block decision detection techniques orientated to SM signals in MIMO-OFDM system. Both zero-forcing (ZF) and minimum mean square error (MMSE) schemes based detection versions are presented. Setting out from a novel general model for the evaluation of the signal-to-noise ratio (SNR) at the data detector output, the authors will evaluate the error ratio performance of the novel MIMO detectors and provide comparison results. It will be shown that the simple block decision detectors rather than interference cancellation based schemes provide an attractive coded performance at a lower realization complexity.

On the physical layer performance of the release 8 E-UTRA downlink

The 3GPP (Third Generation Partnership Project) LTE (Long Term Evolution) activity towards the evolved UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access, which is known as E-UTRA, was started in November 2004 and recently culminated in the Release 8 of the 3GPP technical specifications, cf. e.g. the technical specifications 3GPP TS 36.101 and 3GPP TS 36.201. In the case of the physical layer, the performance evaluation of E-UTRA must be based on the 3GPP technical recommendation TR 25.814, published in October 2006. This manuscript illustrates the performance which can be expected in the downlink of UTRA LTE in various conditions.

On MIMO for UTRA LTE

The long term evolution of UMTS (Universal Mobile Telecommunications System), UTRA LTE, is based on OFDM (orthogonal frequency division multiplexing) combined with MIMO (multiple-input multiple-output) techniques. In particular, the Alamouti and the V-BLAST (Vertical Bell Labs Layered Space Time) schemes are seen as interesting MIMO concepts. In this communication, the authors will compare these two MIMO schemes w.r.t. the achievable performance in the UTRA LTE downlink using up to two transmit and two receive antennas.

Closed-loop schemes in UTRA LTE and LTE-advanced

The 3GPP (Third Generation Partnership Project) LTE (Long Term Evolution) activity towards the evolved UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access, which is known as E-UTRA, was started in November 2004 and recently culminated in the Release 8 of the 3GPP technical specifications, cf. e.g. the technical specifications 3GPP TS 36.101 and 3GPP TS 36.201. In the case of the physical layer, the performance evaluation of E-UTRA must be based on the 3GPP technical recommendation TR 25.814, published in October 2006. This manuscript illustrates the performance which can be expected in the downlink of UTRA LTE in various conditions.