Motohiro Tanno

Coordinated multipoint transmission/reception techniques for LTE-advanced [Coordinated and Distributed MIMO]

This article presents an elaborate coordination technique among multiple cell sites called coordinated multipoint transmission and reception in the Third Generation Partnership Project for LTE-Advanced. After addressing major radio access techniques in the LTE Release 8 specifications, system requirements and applied radio access techniques that satisfy the requirements for LTE-Advanced are described including CoMP transmission and reception. Then CoMP transmission and reception schemes and the related radio interface, which were agreed upon or are currently being discussed in the 3GPP, are presented. Finally, system-level simulation evaluations show that the CoMP transmission and reception schemes have a significant effect in terms of improving the cell edge user throughput based on LTE-Advanced simulation conditions.

Evolved UTRA - physical layer overview

This paper presents the physical layer features and structures, along with the NTT DoCoMos proposals on solutions for the Evolved UTRA. After completion of study item investigations, outlines for physical channel structures were determined. The proposals for the orthogonal reference signal structures, multiplexing of the synchronization signal and broadcast channel appropriate to scalable multiple transmission bandwidths, the hierarchical synchronization signal structure, the downlink Layer 1 (L1) /Layer 2 (L2) control channel structure, and block-wise resource block-level distributed transmission for the shared data channel in the downlink are described. Other proposals such as purpose grouping for the random access channel in the uplink, the uplink L1/L2 control channel structure, and a link adaptation scheme for the shared data channel are also presented.

Broadband radio access: LTE and LTE-advanced

This paper addresses broadband radio access techniques for the Long-Term Evolution (LTE) specified as the Release 8 specifications (Rel. 8 LTE) and LTE-Advanced in the 3rd Generation Partnership Project (3GPP). We first briefly describe the system requirements for the Rel. 8 LTE and LTE-Advanced. Then, we describe wider transmission bandwidths around 100 MHz to satisfy the peak data rate of 1 Gbps in the downlink and 500 Mbps in the uplink for LTE-Advanced. Based on multiple access schemes and multiple-input multiple-output (MIMO) channel techniques in the Rel. 8 LTE, enhanced multiple access schemes and MIMO channel techniques for LTE-Advanced are presented to satisfy the improved system requirements while maintaining backward compatibility with the Rel. 8 LTE radio interface.

Investigation on Optimum Radio Link Connection Using Remote Radio Equipment in Heterogeneous Network for LTE-Advanced

This paper proposes the optimum radio link connection (RLC) using remote radio equipment (RRE) in a heterogeneous network in which various types of cell configurations exist with different cell sizes and downlink transmission power levels for LTE (Long-Term Evolution)-Advanced. The instantaneous received signal-to-interference plus noise power ratio (SINR) and the user throughput performance employing the proposed RLC methods are investigated using system-level simulations. From the simulation results, we show that the proposed independent RLC method between the downlink and uplink and the proposed multipoint RLC method based on coordinated multipoint transmission/reception achieve a higher user throughput both in the downlink and uplink compared to the conventional common RLC method. Therefore, the proposed independent and multipoint RLC methods are very promising candidates to improve the user throughput particularly near the cell edge in a heterogeneous network for LTE-Advanced.

Three-step fast cell search algorithm utilizing common pilot channel for OFCDM broadband packet wireless access

This paper proposes a three-step cell search algorithm that utilizes only the common pilot channel (CPICH) for the forward link orthogonal frequency and code division multiplexing (OFCDM) broadband packet wireless access, assuming two-layered spreading code assignment with a cell-specific scrambling code (CSSC) and a channel-specific orthogonal code (CSOC). The proposed cell search algorithm is performed in the following three steps: OFCDM symbol timing detection utilizing the guard interval timing in the first step; successive simultaneous frame timing and CSSC group detection in the second step by taking the correlation of the CPICH based on the property yielded by shifting the CSSC phase in the frequency domain; and CSSC identification within the group based on the correlation detection with CPICH in the third step. The most prominent feature of the proposed cell search algorithm is that it does not employ the conventional synchronization channel (SCH), which is exclusively used for the cell search. Computer simulation results elucidate that when the transmission power ratio of the CPICH to one code channel of the traffic channel (TCH) is more than 9 dB, the proposed cell search method achieves faster cell search time performance compared to the conventional method using the SCH with the transmission power ratio of the SCH to one code channel of the TCH of 3 dB. Furthermore, the results show that it can accomplish the cell search within 1.7 msec at 95% of the locations in a 12-path Rayleigh fading channel with the maximum Doppler frequency of 80 Hz and the r.m.s. delay spread of 0.32 /spl mu/sec.

Layered OFDMA Radio Access for IMT-Advanced

This paper proposes layered orthogonal frequency division multiple access (OFDMA) radio access for LTE (long-term evolution)-advanced to achieve higher-level system requirements than those in Release 8 LTE called Evolved UMTS terrestrial radio access (UTRA) and UMTS terrestrial radio access network (UTRAN). Layered OFDMA comprises layered transmission bandwidth assignment according to the required data rate, a layered control signaling structure, and support for layered environments in which an adaptive multi-access scheme with hybrid single-carrier and multicarrier based radio access is applied. layered OFDMA radio access will support all functionalities provided in Release 8 LTE and its enhancement. Key radio access techniques such as fast inter-cell radio resource management that take advantage of remote radio equipment (RRE) aiming at inter-cell orthogonality, multi-antenna transmissions with more antennas, and coverage enhancing techniques are used to achieve a high level of capacity and cell-edge spectrum efficiency.

Physical Channel Structures and Cell Search Method for Scalable Bandwidth for OFDM Radio Access in Evolved UTRA Downlink

This paper proposes physical channel structures and a cell search method for OFDM based radio access in the evolved UTRA (UMTS Terrestrial Radio Access) downlink, which supports multiple scalable transmission bandwidths from 1.25 to 20 MHz, in the proposed physical channel structures, the central sub-carrier of the OFDM signal is located on the frequency satisfying the 200-kHz raster condition regardless of the transmission bandwidth of the cell site. Moreover, the synchronization channel (SCH) and broadcast channel (BCH), which are necessary for cell search, are transmitted from the central part of the entire transmission spectrum with a fixed bandwidth. In the proposed cell search method, a user equipment (UE) acquires the target cell in the cell search process in the initial or connected mode employing the SCH and possibly the reference signal, which are transmitted from the central part of the given transmission bandwidth. Alter detecting the target cell, the UE decodes the common control information through the BCH, which is transmitted at the same frequency as the SCH, and identifies the transmission bandwidth of the cell to be connected. Computer simulations show the fast cell search time performance using the proposed SCH structure and the cell search method.

Investigations on Synchronization Channel Sequences in OFDM Based Evolved UTRA Downlink

This paper presents the optimum primary- synchronization channel (P-SCH) and secondary-SCH (S-SCH) sequences for the SCH based on criteria to achieve fast initial and neighboring cell search time performance in the Evolved UTRA (E-UTRA) downlink. Simulation results show that the P-SCH sequence has a slight influence on the achievable cell search time, and that the application of multiple sequences, i.e., three P-SCH sequences, is beneficial in achieving fast cell search time performance particularly for the neighboring cell search. The results also show that the Walsh-Hadamard sequence or cyclic-shifted orthogonal sequence is suitable for the S-SCH sequence to indicate the cell ID group. Furthermore, it is shown that the combination of a permutation of the orthogonal S-SCH and P-SCH-specific scrambling sequences is advantageous in suppressing the cross-correlation between S-SCHs that collide and in achieving a fast cell search time particularly for the neighboring cell search in inter-node B synchronous operation.

Investigation on Transmit Diversity for Synchronization Channel in OFDM Based Evolved UTRA Downlink

Tins paper presents the most appropriate transmit diversity scheme for the synchronization channel (SCH) employing the latest radio interface for the SCH structure and sequences based on system-level simulations in the evolved UTRA downlink. The transmit diversity candidates assumed in the paper are preceding vector switching (PVS), time switched transmit diversity (TSTD), cyclic delay diversity (CDD), and frequency switched transmit diversity (FSTD) based on the features of the SCH. Simulation results show that transmit diversity is effective in increasing detection probabilities of SCH timing detection in the first step and the cell ID group-specific SCH sequence in the second step of the cell search process. Moreover, we clarify that PVS is the best transmit diversity scheme for the SCH based on the reduction in the cell search time. We show that PVS achieves fast cell search in less than approximately 20 msec at the location probability of 90% regardless of the inter-site distance up to 10 km.

Cell Search Time Comparison Using Hierarchical and Non-Hierarchical Synchronization Channels in OFDM Based Evolved UTRA Downlink

This paper presents a performance comparison of the initial cell search time and neighboring cell search time using hierarchical and non-hierarchical synchronization channel (SCH) structures in order to establish the optimum SCH structure in the evolved UTRA downlink. Computer simulation results show that in a 19-cell configuration, the cell search time at the 90% cumulative distribution function using the hierarchical SCH structure is less than half that using the non-hierarchical SCH structure in a neighboring cell search under low signal-to-interference plus noise power ratio conditions, although both structures achieve almost the same cell search time in the initial cell search. This is due to the cross-correlation based SCH symbol timing detection in the hierarchical SCH structure, which is affected less by noise than auto-correlation based detection in the non-hierarchical SCH structure. Thus, we conclude that the hierarchical SCH structure is more appropriate than the non-hierarchical SCH structure based on the cell search time performance especially in the neighboring cell search.