This paper investigates the gain of inter-Node B macro diversity for a scheduled-based shared channel using single-carrier FDMA radio access in the Evolved UTRA (UMTS Terrestrial Radio Access) uplink based on system-level simulations. More specifically, we clarify the gain of inter-Node B soft handover (SHO) with selection combining at the radio frame length level (=10 msec) compared to that for hard handover (HHO) for a scheduled-based shared data channel, considering the gains of key packet-specific techniques including channel-dependent scheduling, adaptive modulation and coding (AMC), hybrid automatic repeat request (ARQ) with packet combining, and slow transmission power control (TPC). Simulation results show that the inter-Node B SHO increases the user throughput at the cell edge by approximately 10% for a short cell radius such as 100-300 m due to the diversity gain from a sudden change in other-cell interference, which is a feature specific to full scheduled-based packet access. However, it is also shown that the gain of inter-Node B SHO compared to that for HHO is small in a macrocell environment when the cell radius is longer than approximately 500 m due to the gains from hybrid ARQ with packet combining, slow TPC, and proportional fairness based channel-dependent scheduling.

In the Evolved UTRA (UMTS Terrestrial Radio Access) downlink, Orthogonal Frequency Division Multiplexing (OFDM) based radio access was adopted because of its inherent immunity to multipath interference and flexible accommodation of different spectrum arrangements. This paper presents the optimum adaptive modulation and channel coding (AMC) scheme when resource blocks (RBs) is simultaneously assigned to the same user when frequency and time domain channel-dependent scheduling is assumed in the downlink OFDMA radio access with single-antenna transmission. We start by presenting selection methods for the modulation and coding scheme (MCS) employing mutual information both for RB-common and RB-dependent modulation schemes. Simulation results show that, irrespective of the application of power adaptation to RB-dependent modulation, the improvement in the achievable throughput of the RB-dependent modulation scheme compared to that for the RB-common modulation scheme is slight, i.e., 4 to 5%. In addition, the number of required control signaling bits in the RB-dependent modulation scheme becomes greater than that for the RB-common modulation scheme. Therefore, we conclude that the RB-common modulation and channel coding rate scheme is preferred, when multiple RBs of the same coded stream are assigned to one user in the case of single-antenna transmission.

This paper presents the optimum control interval for intra-cell fractional transmission power control (TPC) for a shared data channel employing frequency domain channel-dependent scheduling and adaptive modulation and coding (AMC) in the Evolved UTRA uplink using single-carrier (SC)-FDMA radio access. The simulation results show that the best attenuation factor in the fractional TPC is approximately 0.6 for achieving the maximum user throughput when the maximum target received signal power, P0 is -60 dBm. Then, we show that the optimum averaging interval for the desired signal level, which corresponds to a substantial control interval for the fractional TPC, is approximately 100-200 msec regardless of the maximum Doppler frequency up to 222 Hz and the distance at the shadowing correlation of 0.5. Throughout the simulation results, we verify that slow intra-cell fractional TPC associated with fast AMC is effective in achieving the maximum cell throughput and cell-edge user throughput.

This paper investigates the best cell-common reference signal (RS) structure and transmit diversity scheme for Multimedia Broadcast Multicast Service (MBMS) signals considering frequency diversity in a single-frequency network (SFN) in the OFDM based Evolved UTRA downlink. Link-level simulation results show that cyclic delay diversity (CDD) is the most promising transmit diversity scheme for the MBMS signals considering the RS overhead. It is also elucidated that the required average received signal energy per symbol-to-noise power spectrum density ratio (Es/N0) using CDD is reduced by approximately 0.5 dB even though the MBMS signal obtains a sufficient frequency diversity gain in SFN operation. Furthermore, we clarify the achievable data rate for the MBMS signal at the cell edge of the centered MBMS cell that satisfies the required block error rate (BLER) using two-antenna transmit CDD and diversity reception by system-level simulation. Then, the simulation results show that the offered data rates with the required BLER of less than 10-2 at 95% coverage are 0.211 (0.17), 0.243 (0.196), 1.168 (1.084), and 2.754 (2.754) bps/Hz with the number of cells providing MBMS, NMBMS = 1, 3, 21, and 57, respectively, employing transmit CDD with two antennas (single-antenna transmission) for ISD = 500 m.

This paper proposes block-wise resource block (RB)-level distributed OFDMA transmission with ND-block division in order to obtain the frequency diversity effect even for low-rate traffic (here ND indicates the number of virtual RBs within one physical RB) in Evolved UTRA downlink. More specifically, we propose a constraint rule such that distributed transmission is multiplexed into a different physical RB from that of localized transmission in order to achieve the same resource assignment and independent decoding between the distributed and localized transmissions. Based on the proposed rule, a virtual RB for distributed transmission is segmented into ND blocks with the size of 1/ND of the original virtual RB. Then, the ND virtual blocks with the size of 1/ND are mapped together into each ND physical RB in a distributed manner, resulting in a large frequency diversity effect. Numerical calculations show that the block-wise RB-level distributed transmission can reduce the number of control signaling bits required for resource assignment compared to the subcarrier-level distributed transmission scheme, which provides the best performance. Moreover, a system-level simulation shows that the loss in the cell throughput employing the block-wise RB-level distributed transmission compared to that using the subcarrier-level transmission is only within 3-4% when the channel load is 0.5 and 1.0, i.e., the maximum loss is 3-4% at approximately 90% in the cumulative distribution function (CDF).

This paper presents the optimum physical random access channel (PRACH) structure in terms of the number of control signaling bits accommodated and the transmission bandwidth based on the link budget in order to satisfy the coverage requirement for the single-carrier (SC)-FDMA based E-UTRA uplink. First, we present the design concept of the PRACH structure considering the purposes of the random access procedure in the E-UTRA. Simulation evaluations including a system-level simulation show that a PRACH comprising a 0.5-msec preamble sequence can convey a 6-bit control signal at the cell edge when the inter-site distance (ISD) is 500 m under full channel load conditions with one-cell frequency reuse. It is also shown, however, that a PRACH longer than one-sub-frame, e.g., 1.0 msec, is necessary to support the ISD of 1732 m assuming the same conditions. We also show that the best transmission bandwidth for the PRACH is approximately 1.08-4.5 MHz from the viewpoint of the misdetection probability, and a 1.08-MHz transmission bandwidth is suitable considering other aspects such as flexible resource assignment in the time domain and a small number of options in the transmission bandwidth.

This paper presents comparisons between common and dedicated reference signals (RSs) for channel estimation in MIMO multiplexing using codebook-based precoding for orthogonal frequency division multiplexing (OFDM) radio access in the Evolved UTRA downlink with frequency division duplexing (FDD). We clarify the best RS structure for precoding-based MIMO multiplexing based on comparisons of the structures in terms of the achievable throughput taking into account the overhead of the common and dedicated RSs and the precoding matrix indication (PMI) signal. Based on extensive simulations on the throughput in 2-by-2 and 4-by-4 MIMO multiplexing with precoding, we clarify that channel estimation based on common RSs multiplied with the precoding matrix indicated by the PMI signal achieves higher throughput compared to that using dedicated RSs irrespective of the number of spatial multiplexing streams when the number of available precoding matrices, i.e., the codebook size, is less than approximately 16 and 32 for 2-by-2 and 4-by-4 MIMO multiplexing, respectively.

This paper presents the best transmit diversity schemes for three types of common/shared control signals from the viewpoint of the block error rate (BLER) performance in the Evolved UTRA downlink employing OFDM radio access. This paper also presents the coverage performance of the common/shared control signals using transmit diversity with respect to the outage probability that satisfies the required BLER performance, which is a major factor determining the cell configuration. Simulation results clarify that Space-Frequency Block Code (SFBC) and the combination of SFBC and Frequency Switched Transmit Diversity (FSTD) are the best transmit diversity schemes among the open-loop type transmit diversity candidates for two-antenna and four-antenna transmission cases, respectively. Furthermore, we show through system-level simulations that SFBC is very effective in reducing the outage probability at the required BLER for the physical broadcast channel (PBCH), for the common control signal with resource block (RB)-level assignment such as the dynamic broadcast channel (D-BCH) and paging channel (PCH), and in increasing the number of accommodated L1/L2 control signals over one transmission time interval duration, using mini-control channel element (CCE)-level assignment.

This paper investigates the uplink throughput performance and the interference power to other cells using an Evolved UTRA (E-UTRA) laboratory and field experimental system. In E-UTRA uplink, the near-far problem is not an issue since the orthgonality among the users within the target cell is maintained. Therefore, the fractional transmission power control (TPC), in which the target level of TPC is adjusted according to the path loss level, can be adopted. Thus, it is expected the high cell throughput and the large coverage area by combining fractional TPC, adaptive modulation and channel coding (AMC), and variable resource block (RB) allocation. The indoor and field experimental results show that the peak throughput of approximately 45 Mbps is achieved by allocating a wider bandwidth and setting higher target level for the UE located near the cell site while keeping the adjacent cell interference level almost the constant. We also showed that the system capacity can be improved by 50% in simple cell model by applying the AMC and the fractional TPC.

This paper experimentally investigates the effect of frequency error compensation provided by demodulation automatic frequency control (AFC) using the Synchronization Channel (SCH) in downlink OFDM radio access. The implemented OFDM receiver compensates for the frequency error caused by the difference in frequency between a base station (BS) and a user equipment (UE) using a time-division multiplexed SCH signal and that caused by the Doppler shift generated by the mobility of a user using reference signals with staggered multiplexing. Experimental results show that even when the standard oscillator frequency of the UE cannot be made to track the more accurate frequency of a BS, demodulation AFC can suppress the residual frequency error to a sufficiently low level, i.e., within 0.3 ppm, using the SCH so that the degradation in the block error rate of the physical broadcast channel control signals is slight, i.e., within approximately 0.1 dB, with respect to the case without frequency error for speeds greater than 350 km/h.

This paper proposes the use of inter-cell transmission power control (TPC) with overload indicator (OLI) signaling to user equipment (UE) in addition to intra-cell TPC for the Evolved UTRA uplink. In the proposed inter-cell OLI transmission method, a cell site (Node B) selects UEs offering high-level interferences to the cell site based on the measured path loss difference, and then, the cell site transmits the OLI signal to the selected UEs. The simulation results show that the inter-cell TPC improves both the average user throughput and cell-edge user throughput at 5% in the cumulative distribution function (CDF) curve, assuming the same sector throughput. For instance, when the sector throughput is 1 Mbps using 1.08 MHz bandwidth, the inter-cell TPC with the proposed UE-common OLI scheme increases the average user throughput and the 5%-cell edge user throughput by approximately 41% and 53%, respectively, compared to the case with intra-cell TPC only. Furthermore, when the inter-cell TPC with the proposed UE-individual OLI is employed, the corresponding average user throughput and the 5% user throughput are increased by approximately 87% and 94%, respectively.

This paper presents a comparison of hierarchical and non-hierarchical synchronization channel (SCH) structures in terms of the initial cell search time and neighboring cell search time 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 90% in the cumulative distribution function (CDF) 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 (SINR) 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 the auto-correlation based detection in the non-hierarchical SCH structure. Thus, we conclude that the hierarchical SCH structure is superior to the non-hierarchical SCH structure based on the cell search time performance especially in the neighboring cell search.

This paper compares the turbo code and rate-compatible low-density parity-check (LDPC) codes based on the block error rate (BLER) performance and decoding complexity in order to clarify which channel coding scheme is most appropriate for the channel coding scheme in the OFDM based Evolved UTRA (E-UTRA) downlink. Simulation results and the decoding complexity analysis show that although the Rate-Compatible/Quasi-Cyclic (RC/QC)-LDPC code employing an offset layered belief propagation (BP) method can reduce the computational complexity by approximately 30% for the channel coding rate of R ≥ 1/2, the required average received signal energy per bit-to-noise power spectrum density ratio (Eb/N0) is degraded by approximately 0.2-0.3 dB for R = 1/3, 1/2 and 3/4 compared to that for the turbo code. Moreover, the decoding complexity level of the RC/QC-LDPC code with the δ-min algorithm is almost the same or higher than that for the turbo code with a slight degradation in the required received Eb/N0. Although the decoding complexity level of the ZigZag code is lower than that of the turbo code, the code brings about a distinct loss in the required average received Eb/N0 of approximately 0.4 dB. Finally, the turbo Single Parity Check (SPC) code improves the BLER performance compared to the ZigZag code, i.e., achieves almost the same BLER performance as that for the turbo code, at the cost of a two-fold increase in the decoding complexity. As a result, we conclude that the turbo code with a contention free interleaver is more promising than the LDPC codes for prioritizing the achievable performance over complexity and as the channel coding scheme for the shared data channel in the E-UTRA.

In the Evolved UTRA (UMTS Terrestrial Radio Access) uplink, single-carrier frequency division multiple access (SC-FDMA) radio access was adopted owing to its advantageous low peak-to-average power ratio (PAPR) feature, which leads to wide coverage area provisioning with limited peak transmission power of user equipments. This paper proposes orthogonal pilot channel generation using the combination of FDMA and CDMA in the SC-FDMA-based Evolved UTRA uplink. In the proposed method, we employ distributed FDMA transmission for simultaneous accessing users with different transmission bandwidths, and employ CDMA transmission for simultaneous accessing users with identical transmission bandwidth. Moreover, we apply a code sequence with a good auto-correlation property such as a Constant Amplitude Zero Auto-Correlation (CAZAC) sequence employing a cyclic shift to increase the number of sequences. Simulation results show that the average packet error rate performance using an orthogonal pilot channel with the combination of FDMA and CDMA in a six-user environment, i.e., four users each with a 1.25-MHz transmission bandwidth and two users each with a 5-MHz transmission bandwidth, employing turbo coding with the coding rate of R = 1/2 and QPSK and 16QAM data modulation coincides well with that in a single-user environment with the same transmission bandwidth. We show that the proposed orthogonal pilot channel structure using the combination of distributed FDMA and CDMA transmissions and the application of the CAZAC sequence is effective in the SC-FDMA-based Evolved UTRA uplink.

We present a TCP flow level performance evaluation on error rate aware scheduling algorithms in Evolved UTRA and UTRAN networks. With the introduction of the error rate, which is the probability of transmission failure under a given wireless condition and the instantaneous transmission rate, the transmission efficiency can be improved without sacrificing the balance between system performance and user fairness. The performance comparison with and without error rate awareness is carried out dependant on various TCP traffic models, user channel conditions, schedulers with different fairness constraints, and automatic repeat request (ARQ) types. The results indicate that error rate awareness can make the resource allocation more reasonable and effectively improve the system and individual performance, especially for poor channel condition users.

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 in 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 in the central part of the given transmission bandwidth. After 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 performance made possible by using the proposed SCH structure and the cell search method.