A simple fundamental relationship is derived between antenna gain and transmitter power which maximizes the effective radiated power in mass-limited satellite systems. In the most common case, maximum effective radiated power is achieved when the payload mass is divided equally between the antenna system and the power system. Although this may have been known intuitively to satellite designers, to the author's knowledge this relationship has never been published. Example calculations show that considerable increases in performance can be expected for satellites which employ high-gain multibeam antennas.

A satellite system with several independent spot beams is considered, wherein each spot beam can be scanned over a limited portion of some large service region. The spectral band is totally reused in each spot beam, thereby providing high system capacity. Such a system combines the high antenna gain advantages of a fixed beam system while providing access to the satellite from any point within the overall service region. Moreover, the transmission resources of the satellite can be dynamically allocated to match time-varying changes of the possibly nonuniform terrestrial traffic patterns. The limited-scan antenna forms multiple spot beams, each of which scans only in one dimension; by alternating polarizations among scan strips, high isolation between beams is guaranteed. We show that nearly equal volumes of traffic can be served by each limited scan beam by proper orientation of the scan regions, and complete interconnectivity among all points in all scan regions is achieved easily. A practical antenna design to implement this concept is presented.

The performance of large scale multicell mobile radio systems using dynamic channel assignment and having limitations on the number of servers available in each coverage cell was investigated by computer simulation. At low system blocking the traffic carried is determined solely by the server limitations while at higher blocking the traffic carried is determined by channel limitations.

Large-scale mobile radio systems using dynamic channel REassignment switch the channels assigned to some of the calls in progress to maintain a nearly optimum separation between coverage areas simultaneously using the same channel. Dynamic channel REassignment produces a significant increase in channel occupancy. For example, in the systems studied, which have a uniform distribution of their fixed channels and were operated against a uniform spatial distribution of offered traffic, the channel occupancy was increased by\frac23over a pure fixed channel assignment system at a blocking rate of one percent. This corresponds to a channel savings of about 40 percent for the same traffic carried at one percent blocking by the hybrid systems that were studied.

Measurements of signal attenuation were made from a suburban hilltop base station to a mobile vehicle on several streets in the surrounding countryside. Measurements of signal strength were simultaneously made in the winter of 1971 at frequencies of 836 MHz and 11.2 GHz and then repeated in the summer to determine the effects of foliage. The presence of foliage reduced the received signal strength and the effect was more pronounced atX-band than at UHF. In cases where the shadowing obstacle was tree covered, signal levels at UHF might typically be 10 dB lower when the trees were in full leaf, whereas atX-band this additional loss could be as high as 20 dB. The experimental data was compared to values predicted by knife-edge diffraction and reasonable agreement was found.

When more than one radio channel is available to serve a mobile customer in a large-scale mobile communications system the strategy used to make the assignment has an effect on system performance. Performance characteristics for five different assignment strategies obtained from a computer simulation are compared in this paper. It was found that the strategy that chooses a channel to be assigned at a base station so that the distance to the next base station using the same channel is a minimum, performs better than a strategy that minimizes the mean square distance to the next "in use" base stations on both sides. Also, it was found that choosing the first available channel encountered in a channel search is a strategy that produces reasonably good system performance.

Dynamic channel assignment in mobile communications systems is able to cope with varying nonuniform spatial user demand. It also readily handles the normal randomness in offered traffic. This study presents system performance data for radio systems having 8, 20, 40, 80, and 120 radio channels available and a radio-channel reuse interval of 4 base-station coverage areas. Data are also presented that compare performance of a 30 radiochannel system with a reuse interval of 3 base stations, a 40 radiochannel system with a reuse interval of 4 base stations, and a 50 radio-channel system with a reuse interval of 5 base stations. The results are obtained from a computer simulation of a onedimensional network laid out along a line. As the number of radio channels available to a communication system increases, the system becomes more efficient in handling the fluctuations in offered traffic. Changing the radio-channel reuse interval also affects the per-channel traffic carried by a dynamic-channel-assignment system.