New efficient dynamic wavelength assignment schemes for wavelength routed WDM ring networks without wavelength converters are proposed. They significantly reduce the blocking probability of the dynamically assigned wavelengths and improve the network throughput. The guiding principle of the new schemes is to maximize contiguously assigned wavelength connections by selecting the best fitting wavelength and therefore to prevent a large number of small unused gaps. Furthermore the new introduced optimum full mesh reservation and the optimized deallocations improve the performance. The gain of the new schemes is shown by simulations. It can be seen that the performance of a wavelength routed ring with one of the new heuristic assignment schemes and the absence of any wavelength converter is almost as good as the performance of a theoretical WDM ring with full wavelength conversion capabilities provided in every node.

A new method for fast optimum wavelength assignments (WLA) within two fiber optical transparent WDM rings is proposed. The combinatorial WLA problem is solved optimally by a heuristic. The generalized shortest path routing matrix (GM) is used and its decomposition in 4 areas significantly simplifies the global WLA by a fast sequential algorithm. This algorithm is less complex and its calculation time is far below the time needed for other heuristics, e.g. one order of magnitude faster than the cyclic shift method. A second compact WLA algorithm that is based on formulas is proposed. The complexity of its implementation reduces to less than 15 lines of code. This algorithm supports either local WLAs with the time complexity O(1) per demand pair or global WLAs for WDM rings of F facility nodes with O(F/sup 2/).

The Kaufman-Roberts (1981) multirate recurrence equation is converted to a functional equation subject to a single step parameter d, which defines the state-dependent recurrence depth of the multirate model. This parameter, d, is verified to be the joint solution of two moment-generating functions. In contrast to the multirate transform domain solution, the characteristic function of the functional model may be inverted explicitly. But this inverse is scaled by d and yields a new state-dependent probability density based on two types of scaled gamma functions. They uniformly cover wide areas of continuous states, capacities C, and demands. A two-moments series expansion of d in the transform domain signifies that it models the effective bitrate of the multirate connections under progress within a complete sharing mode of C. Selected case studies show very good agreements to the exact Kaufman-Roberts' state probabilities and to the high accurate Mitra-Morrison's (1994) tail probabilities. Further partial sharing mode investigations include an efficient approximation for connection admission controls by trunk reservation covering partial and full fairness. The resulting state and tail probabilities deviate only slightly from Roberts' approximations of the past. All solutions achieve time complexities of O(1) per state, which amount to O(SC) with iterative multirate recurrence solutions for S service classes.

A fault-tolerant network clock regenerator (NCR) will be analyzed, which consists of two digital phase-locked loops (DPLL), and which allows a dynamical configuration control and thus is able to meet CCITT's Recommendations concerning permissible slip rates, frequency inaccuracy, as well as phase jitter and wander. The network synchronization scheme will conform to the master-slave principle, in the course of which the reference clock is derived from a national caesium atomic oscillator as master. The NCR's mentioned before serve as slaves which are equipped with highly precise voltage-controlled crystal oscillators and proportional-integral working DPLL's. The results of a field trial in the long-distance communications network of the "Deutsche Bundespost (FRG)" are given and interpreted by a Random Walk Model which describes the time interval errors appearing. For future digital exchanges, an NCR with intelligent configuration control is introduced, which consists of two microprocessor-controlled digital phase-locked loops (MCDPLL) and which has comparable time stability characteristics as the double-DPLL mentioned above at half the circuit volume. Finally, the dominant advantages are shown which result from synchronizing broad-band services by intelligent NCR techniques.

This paper presents a systematic study of the possibilities of time-transparent and of code-transparent binary data transmission in digital communication networks where PCM or differential PCM (DPCM) systems are employed for the encoding of speech or video signals. To describe the effects that occur if data signals instead of speech or video signals are sampled and transmitted by these two encoding methods, time-transparency and code-transparency are defined and are used as figures of merit. The occurrence of time-quantizing errors and amplitude errors at the decoder output is statistically analyzed. The limitations to be considered in the various applications are described, and time- and code-transparency are evaluated quantitatively. The predictions of the analysis are then compared with the results obtained through simulations. The comparison shows that for data rates below 10 percent of the bit rate (bits per second) in the digital channel, conventional PCM and DPCM encoding are acceptable for binary data transmission and have the advantage of easy signal integration. For higher data rates special data encoding is necessary. The encoding method analyzed here is dual-mode.