Yoshiharu Yamazaki

First-Ever Report on MBWA System Field Trial: Interference Issue in Sectored Cell Layout

This paper discusses results of a MBWA system field trial with fast low-latency access with seamless handoff orthogonal frequency division multiplexing (FLASH-OFDM). The results of the trial show that the downlink throughput performance is significantly impaired by inter-sector interference. To clarify the reasons of the impairment, we carry out a computer simulation on inter-sector interference reduction capability of frequency hopping orthogonal frequency division multiple access (FH-OFDMA), which is used as a multiple access scheme in FLASH-OFDM. The results are summarized as follows: (1) the interference reduction capability of FH-OFDMA is almost the same as that of direct sequence code division multiple access (DS-CDMA), which allocate the same frequency band to all sectors, and (2) in FH-OFDMA, a long hopping-pattern length yields no site diversity effect to reduce inter-sector interference. Additionally, a cumulative distribution of measured signal to noise and interference ratio (SNIR) shows that pilot signals in the neighboring sectors mainly impair the throughput performance. Since a sectored cell layout is mandatory for deployment of the MBWA systems in a high traffic area, inter-sector interference reduction is a key issue for these systems.

Measured downlink throughput performance of MBWA system in urban area

In this paper, we report on a mobile broadband wireless access(MBWA) system field trial with fast low-latency access with seamless handoff orthogonal frequency division multiplexing (FLASH-OFDM), which was carried out at Sendai city in Japan. This paper focuses on coverage and downlink throughput performance, which are the most important criteria for assessing wireless data communication systems. The field trial results show that the base-station can communicate to a subscriber at a cell edge with a throughput of 1.5 Mbit/s assuming circular cells of 0.4 km2, 0.6 km2, and 1.7 km2 when the sector antenna heights are 19 m, 58 m, and 84 m, respectively. Therefore, it is considered that the MBWA system is suitable to provide a broadband mobile data communication service to subscribers in an urban area.

Uplink throughput performance of FH-OFDMA improved by 16 QAM: Effect estimation and validation in MBWA system field trial

In this paper, we report on a mobile broadband wireless access (MBWA) system field trial with Fast Low-latency Access with Seamless Handoff Orthogonal Frequency Division Multiplexing (FLASH-OFDM), which was carried out at Sendai city in Japan. In this paper, the uplink throughput improvement effect of 16 quadrature amplitude modulation (QAM) is estimated by using the measured throughput and received signal level of quadrature phase shift keying (QPSK). The estimation results show that 16 QAM yields a higher uplink throughput than QPSK within coverage of 700 m when the base-station antenna height is 58 m. The results are validated by evaluating the uplink throughput performance of 16 QAM measured in the field trial. We consider that 16 QAM is useful to provide a mobile broadband data communication service to subscribers in uplink as well as downlink.

Coverage Estimation of Uplink 16 QAM Signal up to 20 MHz Bandwidth Based on Field Trial Results of FH-OFDMA System

In this paper, we report on a mobile broadband wireless access (MBWA) system field trial with Fast Low-latency Access with Seamless Handoff Orthogonal Frequency Division Multiplexing (FLASH-OFDM), which was carried out at Sendai city in Japan. This paper describes coverage estimates of an uplink 16 quadrature amplitude modulation (QAM) signal under the condition of constant terminal output power when the bandwidths are from 2.56 MHz to 20.48 MHz. The estimates are based on the field trial results of 1.28 MHz bandwidth. The results show that wider bandwidth yields narrower coverage area. 16 QAM can be used within 55 %, 45 %, 35 %, and 25 % of the field trial area when the signal bandwidths are 2.56 MHz, 5.12 MHz, 10.24 MHz, and 20.48 MHz, respectively. We consider that 16 QAM is useful even if the signal bandwidth is wider than that 10 MHz.