Collision Resolution Algorithm Research Articles

On the asymptotics of the average CRI length of the slotted ALOHA collision resolution algorithm

We provide uniform asymptotic expansions of a finite sum L n, p of essentially geometric type, which arises in the investigation of the average CRI length of the well-known slotted ALOHA collision resolution algorithm with retransmission probability p. In particular, our investigations establish large regions of uniform validity w.r.t. p as n→∞. By means of a direct asymptotic method based on the analysis of a certain sum involving binomial coefficients, we obtain an asymptotic expansion of L n, p , which is uniformly valid for p ⩾ n -0.51/2 e, n→∞. The application of some well-established methods relying on complex analysis yields another result, this time uniformly valid for p ⩾ n -0.99 as n→∞.

Time-of-arrival-based retransmission scheduling for unslotted random access channels

Time-of-arrival-based retransmission scheduling algorithms for unslotted ALOHA-type random access channels with high propagation delay are introduced and analysed in this paper. The techniques described are motivated by the fact that collision bursts on asynchronous channels can be analysed to create a partial time-ofarrival based ordering between the conflicting packets. Packets successfully ordered by collision burst analysis are then retransmitted in a locally synchronous, scheduled manner, thus eliminating potential further conflict between a large fraction of retransmitted messages. Collision resolution algorithms appropriate for channels with continuous signal detection, signal and collision detection, or signal and modified collision detection are described and evaluated in terms of throughput using a simple Poisson traffic model. The maximum throughput is shown to be 0.41, 0.47 and 0.509 for the three cases, thus demonstrating that the proposed time-of-arrival algorithms are competitive with the best slotted collision resolution algorithms. The practicality of the techniques described is also established by showing that maximum throughput is relatively insensitive to inaccuracies in channel feedback for a typical implementation of modified collision detection on a radio frequency channel.

Collision resolution via carrier sensing

Abstract A new collision resolution algorithm via carrier sensing for a randomly accessed channel is proposed and studied in this paper. The channel time is slotted into τ‐sec minislots and complete transmission of a data packet consumes lp minislots. The τ‐sec minislot equals the maximal one‐way source‐destination propagation delay and the time needed to detect and abort a collision consumes lc minislots. Analytical results of throughput and delay have been explicitly derived. Via numerical examples, it is observed that channel throughput reaches 0.96775 if lp = 100 and lc = 2. The channel throughput is 0.68111, even if lp = 10 and lc = 5. Computer simulations are also provided to verify the validity of the analysis.

A multiuser random-access communication system for users with different priorities

A binary feedback collision resolution algorithm is developed for a multiuser random access communication system with nonhomogeneous user population. The user population is split into two classes with different priorities. The throughput and delay analysis of the proposed algorithm are performed, and numerical results are obtained. >

Stability of multiple access communication networks

The problem of stability of different multiple access schemes in computer networks is discussed. The results for the main multiple access schemes — slottedaloha, controlledaloha, csma, csma/cd, polling systems and collision resolution algorithms are surveyed. The techniques used for the stability of these systems have been emphasized.

Collision resolution algorithms for CDMA systems

A study is made of collision resolution algorithms for code-division multiple-access systems. Both random and fixed code assignment are considered. Different codes are orthogonal. Two types of multiuser interference are considered. Either the well-known 0.487 algorithm or a windowed version of Capetanakis' collision resolution algorithm is used in resolving collisions. Throughput and delay are derived for each of the protocols considered. Computer simulations are provided to verify the validity of the analysis.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The robustness and performance of tree collision resolution algorithms in an unshared feedback error environment

This paper discusses in detail the robustness of the Capetanakis Collision Resolution Algorithm (CCRA) with and without the arrival epoch modification for multiple access networks. In particular, we show that the algorithm is robust against errors that cause different stations to see different feedback information about the results of the transmission attempts, and we quantify, through simulations and analysis, the performance (throughput/delay) degradation caused by those unshared errors.

Analysis of a stack algorithm for CSMA-CD random length packet communication

An exact performance evaluation of the free-access stack collision resolution algorithm is given under the hypotheses of carrier-sense multiple access with collision detection (CSMA-CD) local area network communication with packets of different length. In particular, the packet delay moments (mean and variance) and the maximum throughput that the system achieves for any given packet length distribution are precisely described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Random-access systems with a time varying channel

A random multiple-access system which employs a collision resolution algorithm for accessing a common time-varying channel is considered. The channel is assumed to be in one of two states. In each state, the channel is characterized by a general discrete memoryless channel and the transitions between the two states are assumed to be Markovian. A set of sufficient conditions for the ergodicity (stability) of the system is established. As an example, the case when the Capetanakis tree algorithm operates with a time-varying noisy channel is examined. The stability of this system is analyzed, and the throughput is evaluated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Throughput analysis of blocked access tree algorithms with mini-slots

The tree-based collision resolution algorithms have been extensively studied because of their stable behavior. Some of these studies have employed control mini-slots in order to improve the performance of tree-based algorithms. This paper analyzes the maximum stable throughput of two Q-ary blocked access tree algorithms with mini-slots: one (TA/M-BF) assumes that something/nothing binary feedback information is available in a mini-slot, and the other (TA/M-TF) assumes ternary feedback information in a mini-slot. Both algorithms allow all users having new packets to transmit them in the slot immediately after the previously collided packets are resolved (i.e., blocked access algorithms). The stability of these algorithms is affected by two critical values of the throughpuut; the lower critical value is called the maximum stable throughput. We offer a way to derived those values exactly. The effect of mini-slot length on the maximum stable throughput is also evaluated. Furthermore, the performance of the above two algorithms is compared on the basis of numerical results drawn from our analysis.

A limited sensing protocol for multiuser packet radio systems

A protocol for a multiuser packet radio communication channel is proposed. The basic functions of this protocol are determined by a modified stack-type limited sensing collision resolution algorithm. The protocol is a hybrid of a pure random-access scheme and a reservation scheme. A message consists of a number of packets that are capable of revealing the current activity of the channel. The performance of the system is investigated in terms of throughput and average message delay and analytical results are provided. >

Collision resolution algorithms in multistation packet-radio networks

The performance of a multistation packet-radio network in which the nodes of the network employ some collision resolution algorithm (CRA) for accessing a shared radio channel is analyzed. The two CRAs considered here are the binary-tree CRA (BTCRA) and the clipped binary-tree CRA (CBTCRA). The exact analysis of a multistation network with these access schemes is intractable. Therefore, the authors present an approximate method that captures the interactions among the nodes of different stations. The mean idea is to view the interference among the nodes of different stations as independent random noises and compute the probabilities of these noises, taking into account the interactions between the nodes. Numerical results of the approximate analysis are presented and compared with the results of simulations. >

Splitting algorithms in noisy channels with memory

Multi-access networks are considered in which the shared channel is noisy. The authors assume a slotted-time collision-type channel, Poisson infinite-user model, and binary feedback. Due to the noise in the shared channel, the received signal may be detected as a collision even though no message or a single message is transmitted. This kind of imperfect feedback is referred to as error. A common assumption in all previous studies of multi-access algorithms in channels with errors is that the channel is memoryless. The authors consider the problem of splitting algorithms when the channel has memory. They introduce a two-state, first-order Markovian model for the channel and analyze the operation of the tree collision-resolution algorithm in this channel. They obtain a stability result, i.e., the necessary conditions on the channel parameters for stability of the algorithm. Assuming that the stability conditions hold, they calculate the throughput of the algorithm. Assuming that the stability conditions hold, they calculate the throughput of the algorithm. Extensions to more general channel moders are discussed. >

Mixing collision resolution algorithms exploiting information of successful messages

Algorithms for accessing a slotted-time collision-type broadcast are considered under a Poisson infinite-user model, where each user observes the channel and determines for each slot whether idle or success or collision has occurred. The highest throughput previously achieved for this model is 0.4878. A new scheme is introduced which does not exceed the limitations of the system model, yet achieves a throughput of 0.4892. Extra information is added to the message that can be used only when the message is received successfully. One form of extra information is described, and a new algorithm that exploits it is proposed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Group Testing Protocol with Capture for Random Access Communication

The capture property of a receiver is used to design a collision resolution algorithm for a ternary feedback random access channel. Group testing techniques are employed under the assumption of finite users model. Users are assumed to generate a packet with probability p during a collision resolution interval. Two groups of users with different transmission powers are assumed to exist in the system. Performance of this algorithm is shown to be considerably better than that of the algorithm without capture. Effect of varying the number of users in both groups on the expected collision resolution interval is studied. One of the features of this algorithm is that it is always superior to TDMA for any probability p as long as there is at least one user in the high power group.

A 0.487 throughput limited sensing algorithm

We consider Poisson packet traffic accessing a single-slotted channel. We assume the existence of a ternary feedback per channel slot. We also adopt the limited feedback sensing model where each user senses the feedback only while he has a packet to transmit. For this model we develop a collision resolution algorithm with last come-first served characteristics. The algorithm attains the same throughput as Gallager's algorithm without the latter's full feedback sensing requirement. In addition, it is easy to implement, requires reasonable memory storage, induces uniformly good transmission delays, and is insensitive to feedback errors. In the presence of binary (collision versus noncollision) feedback the algorithm may attain a throughput of 0.4493 .

Announced Arrival Random Access Protocols

In this paper we propose and evaluate several protocols for a random access channel. The channel is divided into a control subchannel which is used to inform all users of the approximate times of arrival of new packets and a data subchannel which is used to transmit the data. Packets arriving at different users at approximately the same time may cause a collision on the control subchannel. Such collisions are resolved on the data subchannel by a collision resolution algorithm. Eight protocols that differ in the feedback available on both channels and the time that the feedback is available are described and evaluated. The expected delay of each protocol is determined by modeling the system as a slotted concentrator. Comparisons are made among the protocols described and analyzed in this paper and between these protocols and other protocols that have been studied previously.

A Collision Resolution Protocol with Simplified Energy Detection

Collision Resolution Algorithms (CRAs) improve the throughput performance of a slotted random-access channel shared by a large population of bursty users. Using (0, 1, e) feedback, the highest capacity reported to date for such a CRA is 0.4878. This can be improved by incorporating additional feedback to provide more information on the number of users involved in a collision. This paper proposes a CRA using simplified energy detection feedback with a capacity of 0.502. In contrast to other schemes using energy detection, this scheme is not sensitive to signal attenuation between users and is simpler to implement.

Collision resolution for buffered users

Previously proposed collision resolution algorithms are extended to a system in which each user has a sufficiently large buffer and is allowed to transmit more than one packet in a collision resolution interval. In the protocol proposed in this study, within each collision resolution interval only the head-of-queue packet in each nonempty buffer has to go through collision resolution. The rest can be transmitted continuously via the addition of a control bit. Our protocol is definitely better than any other protocol in which each packet has to fight its own way through the channel.

Deterministic vs. probabilistic tree collision resolution algorithms

Deterministic vs. probabilistic tree collision resolution algorithms