Shigeru Tomisato

Peak Reduction Improvement in Iterative Clipping and Filtering with a Graded Band-Limiting Filter for OFDM Transmission

The large PAPR of orthogonal frequency division multiplexing (OFDM) transmission is one of the serious problems for mobile communications that require severe power saving. Iterative clipping and filtering is an effective method for the PAPR reduction of OFDM signals. This paper evaluates PAPR reduction effect with a graded band-limiting filter in the iterative clipping and filtering method. The evaluation result by computer simulation shows that the excellent peak reduction effect can be obtained in the fewer iteration numbers by using a roll-off filter instead of the conventional rectangular filter, and the iteration number with the roll-off filter achieving the same PAPR is fewer by twice. The result confirms that the clipping and filtering method by using a graded band-limiting filter can achieve low peak OFDM transmission with less computational complexity.

Cellular CDMA system capacity in a service area with tapered traffic distribution

In the radio link design of cellular CDMA system, system capacity has been estimated with the uniform traffic distribution condition so far. In many cases, however, actual traffic in a service area is not distributed uniformly. Therefore, this paper discusses the up link capacity of the cellular CDMA system applied in a service area with tapered traffic distribution condition. The analytical result shows that the system capacity is degraded according to the degree of traffic concentration to the service area center. It is also suggested that the cell size change in inverse to the degree of traffic concentration is effective to mitigate the system capacity degradation

Peak Power Reduction Method Using Adaptive Peak Reduction Signal Level Control for OFDM Transmission Systems

Future broadband mobile communication systems are necessary to achieve the bit rates of 100 Mbit/s. Orthogonal Frequency Division Multiplexing (OFDM) transmission is an attractive technology because it can remove the influence of frequency selective fading in broadband transmission by adding a suitable guard interval to each OFDM symbol. However, peak-to-average power ratio (PAPR) is very large in OFDM transmission. In this paper, we propose a new PAPR reduction method which can be applied even when unusable bands are inside the system band. In the proposed method, peak reduction signals are generated by iterative signal processing only in the usable frequency band, and filtering to remove out-of-band components of the peak reduction signals is incorporated into the iterative signal processing. The results of computer simulation show that the proposed method can effectively reduce peak power without expanding the spectrum both outside the system band and into unusable bands inside the system band. By using the proposed method, the broadband mobile communication system with low peak power and high flexibility of frequency band use can be realized.

A study on integration of mobile communication and TV broadcasting systems operating in UHF band

According to the recent introduction of digital-TV broadcasting services and the band expansion for mobile communication services, new systems by the integration of mobile communication and terrestrial TV broadcasting systems in the UHF band are expected to realize efficient resource management and new attractive services. In this paper, the aspects on system configuration and mobile radio link design are examined to investigate the possibility of integration of mobile communication and TV broadcasting systems operating in the UHF band.

Transmission Performance Evaluation for Designing an OFDM Transmitter That Offers Iterative Peak Reduction

One of the key technologies to realize future broadband mobile communications is orthogonal frequency division multiplexing (OFDM) transmission. However, the peak-to-average power ratio (PAPR) in OFDM transmission is so much larger than that in single carrier transmission that its adoption in mobile communication systems is uncertain. This paper evaluates the transmission performance possible with iterative peak reduction to design more efficient OFDM transmitters. The PAPR reduction effect and bit error rate (BER) performance are clarified by computer simulations. We calculate the set PAPR value that achieves a target PAPR in the iterative peak reduction method. The required Eb/N0 performance is evaluated under the calculated PAPR condition. The results are effective in designing the back-off value of a transmission power amplifier given fixed transmission quality and computational complexity.