A design procedure for 30/20 GHz trunking systems is presented which permits the joint optimization of the satellite links and the terrestrial links between diversity terminals of individual earth stations. This process involves the generation of uplink and downlink power control functions (PCF's), which depend on 1) the rapidity with which power control can be exercised, relative to the rate of variation of atmospheric attenuation, and 2) the available uplink and downlink HPA power. The PCF's combine to produce a link availability curve (LAC), which describes the uplink/downlink fade combinations for which a specified bit error rate (BER) can be maintained. The set of required terminal separation distances (TSD's) can generally be computed from the LAC, together with the marginal uplink and downlink attenuation distributions. Methods of implementing uplink and downlink power control are discussed. In particular, several alternatives for determination of uplink attenuation and selection of the appropriate transmit terminal are contrasted.

A method of assigning carrier levels in an SCPC system with mixed earth stationG/Tsis developed which optimizes system performance for uniformly spaced and randomly assigned carrier frequencies. The optimum transponder backoff is shown to be identical to that for a system of uniform carriers in which the (common) earth station(G/T)^{-1}is a weighted average of the different(G/T)^{-1}values in the mixed system. With the transponder backoff determined, the carrier level to be transmitted to each station type is simply expressed in terms of the stationG/T. Since the carrier frequencies are randomly assigned, the technique described is ideally suited to the design of a demand-assignment system. Alternatively, the same performance can be realized through a pseudorandom choice of frequencies in a system of fixed frequency assignments. In the particular case of two station types with an equal number of large and small carriers, a system employing a random assignment of carrier frequencies is compared with one in which the large and small carriers alternate in frequency. It is shown that, if equal carrier-to-noise ratios are required for the two carrier sizes, the two systems are capable of identical performance. However, the system of alternating carriers requires a lower EIRP per carrier from the smallerG/Tstations.

Carrier-to-intermodulation (C/IM) power ratios are derived for two types of single-channel-per-carrier (SCPC) systems in terms of the single-carrier transfer characteristic of the satellite TWT. The first system is based on a set of equal-amplitude, uniformly spaced carriers and is appropriate whenever complete earth-station interconnectivity is required in a bandwidth-limited environment. The second system is designed to handle traffic flow between a large number of small stations and one or more large stations. It utilizes a frequency plan of alternating large and small carriers. The C/IM ratios for the twolevel system are expressed in terms of the C/IM ratio for a single-level system operating at the same TWT backoff. Application of the results to a power limited system of either type is also indicated.

The design of signals for binary communication systems employing feedback has previously been considered by Turin. A delayless, infinite-bandwidth forward channel disturbed by additive, white, Gaussian noise is assumed. At each instant of time, the log likelihood ratio of the two possible signals is fed back to the transmitter via a noiseless and delayless feedback channel. The forward-channel signals are said to be optimally designed when the feedback information is so utilized that the average (for sequential detection) or fixed (for nonsequential detection) transmission time is minimized, subject to a specified probability of error. Average and peak power constraints are also placed on the signals. Turin has solved the signal design problem for extreme values (i.e., very large or equal to one) of the peak-to-average power constraint ratio. These results are extended in this paper to arbitrary values of the power constraint ratio, for both sequential and nonsequential detection.

The presence of a feedback channel makes possible a variety of sequential transmission procedures, each of which can be classified as either a block-transmission or a continuous-transmission scheme according to the way in which information is encoded for transmission over a noisy forward channel. A sequential continuous-transmission system employing a binary symmetric forward channel (but which is suitable for use with any discrete memoryless forward channel) and a noiseless feedback channel is described. Its error exponent is shown to be substantially greater than the optimum block-code error exponent at all transmission rates less than channel capacity. The average value and the first-order probability distribution of the effective constraint length, found by simulating the system on an IBM 709 computer, are also given.