A new MAC layer protocol, DQRAP (distributed queueing random access protocol), provides performance with respect to throughput and delay that approaches that of an ideal protocol. The paper introduces PDQRAP, a prioritized version of DQRAP. Two formats, the extra-bit and the extra-slot, each a variation of the basic DQRAP are described. Simulation results are presented that show that under a total traffic load of 90%, a high priority segment of 20%-30% in either format has delay characteristics ranging from one-third to one-half of the delay characteristics of the normal priority traffic. The relative advantages and disadvantages of each format ore discussed. It is suggested that PDQRAP could be the mechanism that allowed a shared medium to economically transport traffic associated with multi-media services utilizing LANs, MANs, and WANs.>

For decades there has been a search for a multiple access protocol for a broadcast channel that would provide a performance that approached that of the ideal M/D/1 queue. This ideal performance would provide immediate access at light loads and then seamlessly move to a reservation system at high offered loads. DQRAP (distributed queueing random access protocol) provides a performance which approaches this ideal. Furthermore it is accomplished using as few as three control minislots which suggests that, aside from establishing new theoretical bounds, DQRAP will be of great practical value.DQRAP requires that channel time be divided into slots each of which consists of one data slot and m control minislots, and that each station maintain two common distributed queues. One queue is called the data transmission queue, or simply TQ, used to organize the order of data transmission, the other queue is the collision resolution queue, or simply RQ, which is used to resolve the collisions and to prevent collisions by new arrivals. The protocol includes data transmission rules, request transmission rules and queuing discipline rules. Modelling and simulation indicate that DQRAP, using as few as 3 minislots, achieves a performance level which approaches that of a hypothetical perfect scheduling protocol, i.e., the M/D/1 system, with respect to throughput and delay. DQRAP could prove useful in packet radio, satellite, broadband cable, cellular voice, WAN, and passive optical networks.

The distributed queue dual bus is a protocol being considered by the IEEE 802.6 Working Committee for adoption as a metropolitan area network standard. Its primary function is to interconnect LANs over a high-speed physical medium (optical networks) operating at over 100 Mb/s and to support integrated traffic. Although DQDB is a totally distributed and contention-free protocol with throughput very close to one, the access delays experienced by stations vary with their position on the bus, upstream stations on a particular bus experiencing lesser delays compared to downstream stations. The results of simulation runs that compare the access delays experienced by MAC (media access control) stations at different utilization levels and at different priority levels are presented. It is noted that skewing in access delays is experienced by downstream stations.>

Realism in computer graphics typically requires using 24 or more bits/pixel to generate an image. This paper describes a method developed by the authors called "Color Cell Compression" or "CCC" that preserves at least a limited animation and local update capability yet yields extraordinary-looking color images in approximately two bits/pixel independent of image complexity. Three intermediate methods of compressing images to six, four and three bits/pixel respectively are also described. The CCC encoding process for a 640 × 480 image averages 11 seconds on a VAX 11/750, however, the CCC method does permit real-time decoding of these images using software look-up tables and conventional display hardware. The three intermediate methods may also be decoded in real time but have the added advantage of requiring only 3-4 seconds for encoding on a VAX 11/750.