This paper mainly concentrates on recent studies on land mobile propagation, considering new trends of the progress of digital and personal land mobile communications. High speed digital transmission for millimeter-wave indoor communication is of another current interest. Microcellular propagation in urban areas and indoor propagation are major research targets at present days. Multipath propagation characteristics such as delay-profiles becomes more and more important measuring items, and some signal processing methods like MUSIC method have been widely introduced to improve the time resolution against the limit of available radio bandwidth. Path-loss characteristics in mobile propagation are extended to the path-loss prediction and are going to be applied to cellular system design in connection with the design of directional base-station antennas. Another recent topic is an extension of target frequency bands for mobile propagation studies, which are spreading from VHP, UHF and SHF to EHF bands.

Research and standardization activities on FPLMTS are under way throughout the world. This paper shows recent study results on radio transmission technologies in ARIB (Association of Radio Industries and Businesses), which in the standardization organization in Japan. On-going study shows two TDMA based and four CDMA based radio transmission technologies under study. These technologies need to be further studied in detail. The proposal from ARIB is expected to be summarized around the end of the year 1996.

MTDMA (Multimedia, Multimode TDMA) system has been developed for the 3rd generation mobile communications. An adaptive modulation technique is employed, which select 16 QAM or QPSK modulations fit for the O (Indoor Office)/P (Outdoor to Indoor and Pedestrian) communication environments. The maximum user rate of 4 Mbps is realized. Basic specification is described for O, P and V environments.

In this paper, some misconceptions about "multipath propagation" are discussed for those propagation engineers, who are not familiar with the close relationship between multipath propagation and a communication system in a mobile/portable radio communication environment. It is shown that believed facts about multipath propagation are not always true. Namely, it is well-known that multipath propagation is undesirable if a conventional sample-and-decision receiver is assumed. It is not well-recognized that it can be a desirable phenomenon if a sophisticated communication system uses adaptive equalization, anti-multipath modulation, or spread spectrum communication, for example. On the other hand, it is widely accepted that root mean square (rms) multipath delay spread is a good measure of bit-error-rate performance, i.e., as rms delay spread gets larger, bit-error-rate generally gets worse. However, it is pointed out that this is not always true, especially in propagation conditions with very long-delayed multipath signals. In short, it is the purpose of this paper to show examples that the facts believed to be true sometimes turn out to be false, unless we pay attention to both aspects of propagation and system design in the field of mobile/portable radio communications. In fact, for highly efficient communication systems design, propagation, antenna and system factors should be taken into account simultaneously.

This paper compares two techniques in recovering the capacity degradation caused by sectorization in a cellular system. They are the Directed Retry and Load Sharing in sector cells. Since both techniques requires an overlapping area between adjacent sectors, the values of the overlapping area are chosen such that the Carrier to Interference Ratio (CIR) is satisfied.

An experimental study on propagation characteristics in a room of a modern office building using a 57.5 GHz carrier is described. The objective of the study is to provide initial information about the path-loss and fading characteristics for millimeter-wave wireless indoor communication systems. The area of the floor of the room is about 90 m2 and the room was almost empty with no furniture except the experimental apparatus. A wide-beam scalar feed horn transmission antenna and an omnidirectional receiving antenna were used and set to be with the same height. The measured area was divided into many "squares" to characterize the propagation. The variation of square transmission loss was calculated, and the regions where the maximum square transmission loss was observed were pointed out. It became clear that the distance power law for square transmission loss was approximately of the order d-2 along the direct path. Rician distributions for fast fading were derived in almost all squares of this room. The spectra for the fast fading envelope were also derived. From the propagation point of view, the results show that no extreme difficulty seems to exist in developing wireless communication systems in the 60 GHz band.

This paper deals with the method of integration of voice and data in wireless communication systems. By applying the DSV (Data Steal into Voice) technique to D-TDMA (Dynamic Time Division Multiple Access) systems, this paper presents an MAC (Media Access Control) method of integration of voice and data for the systems such as cellular radios and cordless phones. After a brief review of the D-TDMA scheme and the DSV technique, the protocol called D-TDMA/DSV is described. Then, a static analysis to derive the channel capacity and a dynamic analysis to evaluate the throughput and delay performance are presented. An extension of TFA (Transient Fluid Approximation) analysis is employed in the dynamic analysis. With the same system parameters, the capacity of D-TDMA/DSV is compared with that of the traditional D-TDMA. Under the limitation of the blocking probability required for cellular radios, some numerical examples of dynamic analysis are given to show the throughput and delay performance of the system.