This letter proposes a peak power reduction method that optimizes sub-carrier phases of an OFDM signal. The proposed method doesn't require side information transmission and original signal regeneration, which are required in conventional peak power reduction methods with phase optimization, since the optimized phases are distributed as jitter around the original phases before optimization. The iterative PTS (partial transmit sequences) algorithm with a restricted phase control range is used for the jitter injection: the phase optimization process is repeated with widening the control range. A computer simulation is carried out to estimate the proposed method performance. The results show that the proposed method can reduce the peak power by 4 dB when the power penalty caused by phase jitter is only 0.2 dB.

This paper describes downlink throughput performances measured in a mobile broadband wireless access (MBWA) system field trial with Fast Low-latency Access with Seamless Handoff Orthogonal Frequency Division Multiplexing (FLASH-OFDM). The field trial results show that the downlink cell sizes are 0.4 km2, 0.6 km2, and 1.7 km2 when the sector antenna heights are 19 m, 58 m, and 84 m, respectively, assuming the following items. (1) The cell shape is circular. (2) The cell edge is defined as the location where the average downlink throughput is 1.5 Mbit/s.

This paper describes feasibility of a proposed fixed wireless access system with CDMA technology. The system adopts a primary modulation of 16 QAM and the same frequency allocation in all cells to improve spectral efficiency. The system capacity is 1 Gbps per cell within 120 MHz bandwidth. The number of available orthogonal codes corresponds to the orthogonal code length in the system. All subscribers can attain an error free condition with output power control in the presence of inter-cell interference. The following two items are considered to examine the proposed system feasibility. 1) A test modem is fabricated, and a back-to-back modem BER performance is measured. An inter-symbol interference (ISI) level of the modem is estimated with the measured performance. 2) A computer simulation of down-link power control is carried out considering inter-cell interference and impairment factors of the power control such as intra-sector interference caused by the ISI and limited ranges of total and relative output power controls. The simulation results show that the proposed system would be feasible because the obtained power penalties caused by the above impairment factors are negligible.

This paper proposes a heterogeneous wireless network with handover in the application layer. The proposed network requires no upgrade of wireless infrastructure and mobile terminals to convert the present homogeneous networks to the proposed heterogeneous network. Only installing application programs on the content server side and the mobile terminal side is required. The performance of the proposed network has been evaluated in a field trial using a mobile broadband wireless access (MBWA) air interface with wide coverage and a wireless local area network (WLAN) air interface with high throughput. The field trial results show that the maximum value of the handover outage time is only 170 ms. The proposed heterogeneous wireless network is promising since both high throughput and wide coverage area are attained by a combination of the proposed handover scheme with the present homogeneous wireless networks.