The Magic WAND project (wireless ATM network demonstrator) is a project within the European Union ACTS (Advanced Communications Technologies and Services) initiative. The project aims to design, verify, implement and demonstrate a wireless access network for ATM LANs. The WAND system is designed to operate in the 5.2 GHz band for indoor environments with user mobility limited to walking speed. This paper addressed the design and implementation of the wireless transmitter and receiver units and discusses complexity and performance.

The Magic WAND project (Wireless ATM Network Demonstrator) is one of the largest projects within the European Union ACTS (Advanced Communications Technologies and Services) initiative. The project aims to design, verify, implement, and demonstrate a wireless access network for ATM LAN's. The complete range of functionality, from physical data transmission to shared multimedia application, is addressed. The WAND system is designed for indoor environments with user mobility limited to walking speed. The system's functional specification has been designed and verified using SDL (specification and description language). In this paper, the WAND system functional model is given and SDL simulation results are presented, to illustrate how the protocols support some of the key operations of a wireless access network. These include initial registration, call setup, and handover.

Asynchronous transfer mode networks are being deployed to support a wide range of applications and environments. ATM based broadband-ISDN promises to become the first telecom technology that supports multimedia communications in both the wide and local area. The envisaged wide availability of ATM makes it the transfer technology of choice for the next generation of wireless LANs. The wireless ATM access demonstrator, which we describe, provides transparent, untethered access to the wired ATM infrastructure. It proved in practice that ATM, conceived originally for use over optical fibers can be extended over a wireless link.

Studies a model of a network of links with the capacity of an integer number of bandwidth units that are shared amongst calls subdivided in K classes. A class is typified by the bandwidth requirement on each link and the average holding time of its calls. Calls arrive according to a Bernoulli-Poisson-Pascal process. The joint PDF of the number of bandwidth units in use, is found using a known recursion formula that is amenable to numerically instability. An algorithm that fixes the instability is proposed. Previous articles concentrated on time blocking probabilities. Those discussing call blocking probabilities suggest algorithms that are either approximative or time consuming. The present paper proposes a new one, that is shown to be superior in terms of accuracy and computation and storage overhead to the best exact algorithm available so far.>

A large number of terminals transmitting data packets over a common radio channel to a central base station is studied. In inhibit sense multiple access (ISMA), the base station broadcasts a busy signal when an incoming packet is being received, to inhibit other terminals from colliding transmissions. This busy signal arrives at each terminal with a propagation delay, proportional to the distance between the base station and the terminal. This leads to unfairness in the probability of successfully transmitting a data packet, since nearby terminals have more up-to-date information on the actual channel status than remote terminals. This unfairness is additional to the advantage that nearby terminals have because of the capture effect, which is also considered. The paper applies nonstationary Poisson processes to describe the random arrivals of data packets at the central receiver. It is shown that the probability of a successful attempt to transmit a packet decreases, approximately linearly with the distance between the transmitter and the central receiver. The total throughput is also assessed, and it is found that the assumption of a fixed propagation delay adopted in CSMA studies by others gives too optimistic results for ISMA. Moreover, the analysis suggests a subtle change of the fixed delay approximation that enhances its accuracy, without adding complexity. The effect of propagation delays in random access radio networks are of increasing importance, since newly developed systems are designed to transmit with increasingly high bit rates.>

Low delay or low loss (LDOLL) queuing policies for asynchronous transfer model (ATM) fast packet switching allow either retrieval priority or storage priority to be given to the ATM cells of traffic streams with different performance requirements. The improvements in performance that can be achieved by using one bit in the ATM cell header to make the binary LDOLL distinction are analyzed. In the analysis, simulation of the level, where the cell transmission rate of a source may vary between zero and the peak rate and computation at the level, where queuing of individual cells is considered, are combined. It is shown that LDOLL queuing, compared with FIFO queuing in ATM switches, can reduce cell loss probability by many orders of magnitude for low loss traffic. Low delay traffic incurs a slightly higher cell loss which is compensated with a reduced cell delay mean and variance.>

The power of ATM (asynchronous transfer mode) is its ability to provide bandwidth on demand, different sources can have different bandwidth requirements. Sources also differ in performance requirements, some ask for minimal delay variations, whereas others must have extremely low cell loss probabilities. It is shown how these complementary performance requirements can be explained with an LDOLL (low delay or low loss) queue, where sources get either service priority or storage priority. The space of possible LDOLL queuing policies is very large, even after a justified reduction, the size is still O(2/sup Q2/), Q being the maximum number of ATM cells in the LDOLL queue. Using Markov decision theory and concepts of linear programming, only Q so-called efficient solutions are achieved. These are the LDOLL threshold policies, which are conceptually appealing, robust in performance, and practical from the implementation viewpoint.>