To enhance the throughput of a slotted ALOHA control channel in a radio communication system, we present and analyze a method for estimating the number of remote stations that are attempting to transmit to a central base station. Each of the contending remote stations randomly chooses to transmit with probability p. Our novel contribution is the use of information concerning the number of successful packet transmissions that arrive without retransmission (i.e., that are successfully received on their first transmission attempt), as a metric for accurately and robustly estimating the number of contending remote stations. This estimate is determined at the base station and then used to compute the optimal transmission probability p that is used as feedback to the remote stations for their use. The proposed estimation method is analyzed and shown to provide good steady-state performance. While we analyze a slotted ALOHA type of access protocol here, these results can be applied to more complex reservation multiple access protocols in which the slotted ALOHA protocol is used for the reservation channel.

The probability of capture under a model (for a land mobile radio direct sequence spread spectrum system) based on the ratio of the largest received power to the sum of interference powers is examined in the limit of a large number of transmitting stations. It is shown in great generality that the limit depends only on the capture ratio threshold and the roll-off exponent of the distribution of power received from a typical station. This exponent is insensitive to many typical channel effects such as Rician or Rayleigh fading and log-normal shadowing. The model is suitable for large systems with noncoherently combined interference.

We consider the design of efficient channel allocation algorithms in personal communication networks (PCN) where the cells have varying traffic loads. A common communication channel is to be dynamically shared between the cells. We propose a distributed intercell channel allocation policy that is easy to implement through the use of simple signaling between neighboring cells. For cells arranged in a line, we show that the proposed policy achieves maximum throughput. The same is true when the cells are arranged in a circle and the frequency reuse distance is 2, while for larger reuse distances and planar hexagonal arrays, the policy may not always achieve maximal throughput. For general circular arrays, we enhance the policy to achieve maximal throughput asymptotically as the number of cells increases. For planar hexagonal arrays, we show that the policy can guarantee throughputs which are fairly close to maximal.

Unlike wired networks, packets transmitted on wireless channels are often subject to burst errors which cause back to back packet losses. Most wireless LAN link layer protocols recover from packet losses by retransmitting lost segments. When the wireless channel is in a burst error state, most retransmission attempts fail thereby causing poor utilization of the wireless channel. Furthermore, in the event of multiple sessions sharing a wireless link, FIFO packet scheduling can cause the HOL blocking effect, resulting in unfair sharing of the bandwidth. This observation leads to a new class of packet dispatching methods which explicitly take the wireless channel characteristics into consideration in making packet dispatching decisions. We compare a variety of channel state dependent packet (CSDP) scheduling methods with a view towards enhancing the performance of the transport layer sessions. Our results indicate that by employing a CSDP scheduler at the wireless LAN device driver level, significant improvement in the channel utilization can be achieved in typical wireless LAN configurations.

Considers the design of efficient channel allocation algorithms in personal communication networks where the cells have varying traffic loads. A common communication channel is to be dynamically shared between the cells. The authors propose a distributed inter-cell channel allocation policy that is easy to implement through the use of simple signalling between neighboring cells. For cells arranged in a line they show that the proposed policy achieves maximum throughput. The same is true when the cells are arranged in a circle and the channel can be reused in every other cell. For larger reuse distances and planar hexagonal arrays, the policy may not always achieve maximal throughput. For these cases the authors provide regions of achievable cell throughputs under the proposed policy and show that they are tight in certain cases.

We analyze an efficient medium access control (MAC) protocol for use in a single cell of a wireless local area network (LAN). A fixed frame structure with two periods is used; one period for making reservations using a slotted Aloha protocol and a second period for data transmission. The MAC protocol operates in a centralized manner in which a single station, the base station, accepts reservations (transmission or data requests) that are made by the remote stations, and then schedules the times in which they will transmit or receive data. We consider two different types of client-server traffic models, an open-loop and a closed-loop model. In the open-loop model, a remote station can generate reservation requests for the base station whether or not it has received a response from the base station. In the closed-loop case, the remote station waits for a response before generating a new request. The performance of the MAC protocol was analyzed exactly for both the open and closed-loop traffic models and for cases in which transmission errors and a mean-value type of radio capture model are included. In addition, different policies were considered for the transmission strategy that is used by the remote stations when they attempt to make reservations. We derive exact results for the mean throughput and waiting times as well as for the queue length distributions. We also derive an approximate Markov chain to treat a case in which a fixed-position capture model is used. Several types of behavior are illustrated through the use of numerical examples.>

Abstract We present an algorithm that does packet routing on an N‐node butterfly in time O(log N) with small constants. The algorithm is based on Ranade's probabilistic PRAM emulation. We simplify the algorithm by focusing on packet routing and prove bounds on its performance for the cases of permutation routing and uniform, random traffic. The main results are upper bounds on the probability that the routing time exceeds t for a fixed queue size. The simplifications made to Ranade's original algorithm and a more careful analysis enabled us to achieve better constants, which, to the best of our knowledge, are the best to date. © 1994 by John Wiley & Sons, Inc.

An efficient medium access control (MAC) protocol for use in a single cell of a wireless local area network (LAN) is analyzed. A fixed frame structure with two periods is used, one period for making reservations using a slotted Aloha protocol and a second period for data transmission. The MAC protocol operates in a centralized manner in which a single station, the base station, accepts reservations (transmission or data requests) that are made by the remote stations, and then schedules the times in which they will transmit or receive data. Two different types of client-server traffic models, open loop and closed loop, are considered. Exact results are derived for the mean throughput and waiting times as well as for the queue length distributions. Several types of behavior are illustrated by numerical examples.>

The impact of fairness on the throughput of ring networks with spatial reuse is investigated. A model for a slotted ring with spatial reuse that employs a simple fairness mechanism is presented. An exact expression for the expected time taken to evacuate this ring when each node initially contains one packet is derived. The expected evacuation time is used to obtain an exact expression for the throughput of the ring. It is shown that as the number of nodes on the ring increases, the penalty for fairness in terms of throughput becomes negligible.>

An algorithm is presented that does packet routing on an N-node butterfly in time O(log N) with small constants. The algorithm is based on A. Ranade's (1987) probabilistic random access machine (PRAM) emulation. The algorithm is simplified by focusing on packet routing. Bounds on the performance of the algorithm are proven for permutation routing and uniform random traffic. The main results are upper bounds on the probability that the routing time exceeds t for a fixed queue size. The constants achieved are the best to date. A complete description of the routing algorithm is given.>

Four packet-switched networks using shuffle-exchange interconnections and deflection routing are analyzed. The first two are well-known networks based solely on shuffle interconnections, and the other two are variations in which the negative effects of deflection are reduced. Approximate state equations are given under a uniform traffic assumption. The equations predict the distribution of packet delay and can be used in situations where packets are assigned priorities. The four networks are briefly compared to each other and to Batcher-Banyan sorting networks and hypercube deflection networks.>

The (n, k) pseudocyclic maximum-distance-separable (MDS) codes modulo (x/sup n/-a) over GF(q) are considered. Suppose that n is a divisor of q+1. If n is odd, pseudocyclic MDS codes exist for all k. However, if n is even, nontrivial pseudocyclic MDS codes exist for odd k (but not for even k) if a is a quadratic residue in GF(q), and they exist for even k (but not for odd k) if a is not a quadratic residue in GF(q). Also considered is the case when n is a divisor of q-1, and it is shown that pseudocyclic MDS codes exist if and only if the multiplicative order of a divides (q-1)/n, and that when this condition is satisfied, such codes exist for all k. If the condition is not satisfied, every pseudocyclic code of length n is the result of interleaving a shorter pseudocyclic code.>